Croatian Digital Dissertations Repository
Not a member yet
10487 research outputs found
Sort by
EFFICIENCY OF SELECTED PHYSIOTHERAPY TREATMENTS IN PATIENTS WITH LOW BACK PAIN
No full textCilj istraživanja: Glavni cilj je ispitati koji konzervativni postupak fizikalne terapije daje
najbolje rezultate u smanjenju boli kod pacijenata s lumbalnim bolnim sindromom.
Materijal i metode: U istraživanju je sudjelovalo 210 ispitanika koji su bili raspoređeni u
sedam skupina, 6 eksperimentalnih i jedna kontrolna skupina. Kontrolnu skupinu činili su
pacijenti koji su dolazili u ordinaciju fizikalne medicine i rehabilitacije zbog drugih dijagnoza
te ne obuhvaćaju problematiku lumbalnog bolnog sindroma. Svaki je pacijent prošao kroz 10
terapijskih ciklusa tijekom 10 dana. Prosječna dob ispitanika iznosi 50,11 godina (s = 12,9
godina). Od 210 ispitanika bilo je 128 žena (61 %) i 82 muškarca (39 %). Na početku
istraživanja pacijenti su ispunili oba upitnika Roland-Morris Disability Questionnare i
Oswestry Low Back Pain Disability Questionnare, dok se na kraju istraživanja ispunjavao
Roland-Morris Disability Questionnare.
Rezultati: Nakon provedene terapije u svim skupinama došlo je do značajnog poboljšanja kod
svih tretiranih pacijenata. U svim skupina postoji statistički značajna razlika p < 0,05 i p <<
0,001 kod post hoc Scheffeova testa za ukupni Roland-Morrisov upitnik. Rezultati istraživanja
pokazuju da je kombinirana terapija najučinkovitija kod ispitanika s lumbalnim bolnim
sindromom. Naime, između ispitanika skupine 3 (elektroanalgezija) i skupine 4
(magnetoterapija) nema statistički značajne razlike p = 0,987. Također kod ispitanika koji su
koristili pojedinačnu terapiju lasera i ultrazvuka nema statistički značajne razlike p = 0,999.
Testovi kojima smo mjerili opseg pokreta lumbalne kralježnice, indeks sagitalne gibljivosti,
Lasegueov test i Thomayerova mjera, pokazuju poboljšanja kod svih skupina.
Zaključak: Nakon provedenog istraživanja svi sudionici studije imaju veći stupanj
osposobljenosti. Najbolja metoda fizikalne terapije pokazala se u skupini 6, koja obuhvaća
kombinaciju svih fizioterapijskih procedura s kineziterapijom lumbosakralne kralježnice.Objectives: The main goal is to examine which conservative physical therapy procedure gives
the best results in reducing pain in patients with low back pain.
Material and Methods: In the research 210 respondents participated were divided into seven
groups, 6 experimental and one control group. The control group includes patients who come
to the physical medicine and rehabilitation office due with other diagnoses and do not include
the issue of low back pain. Each patient goes through 10 therapeutic cycles over 10 days. The
average age of the respondents is 50.11 years (s = 12.9 years). Out of 210 subjects, 128 were
women (61 %) and 82 (39 %) were men. At the beginning of the study, patients completed both
the Roland-Morris Disability Questionnaire and the Oswestry Low Back Pain Disability
Questionnaire, while at the end of the study, the Roland-Morris Disability Questionnaire was
completed.
Results: After the therapy in all groups, there was a significant improvement in all treated
patients. In all groups there is a statistically significant difference of 0.05 and p << 0.001 in the
post-hoc Scheffe test for the total Roland-Morris questionnaire. Research results show that
combined therapy is the most effective in subjects with lumbar pain syndrome. Namely, there
is no statistically significant difference between the subjects of group 3 (electroanalgesia) and
group 4 (magnetotherapy) p = 0.987. There is also no statistically significant difference in
subjects who used individual laser and ultrasound therapy p = 0.999. The tests we used to
measure the range of motion of the lumbar spine, the index of sagittal mobility, the Lasegue
test and the Thomayer measure show improvements in all groups.
Conclusion: After the research, all study participants have a higher level of training. The best
method of physical therapy was shown in group 6, which includes a combination of all
physiotherapy procedures with kinesitherapy of the lumbosacral spine
PREDICTORS OF SEXUAL DYSFUNCTION AMONG WOMEN TREATED FOR HIGH BLOOD PRESSURE
No full textCilj istraživanja: Ispitati mišljenja i postupanja LOM vezano uz zdravstvenu pismenost, snagu
religijskih uvjerenja, kvalitetu života i povezanosti seksualnih disfunkcija s antihipertenzivnim
liječenjem te istražiti prevalenciju, predskazatelje i međuodnos zdravstvene pismenosti,
kvalitete života, izraženosti religijskih uvjerenja, vrste antihipertenzivne terapije te učestalosti
seksualnih disfunkcija kod žena oboljelih i liječenih od arterijske hipertenzije.
Nacrt studije: Presječno istraživanje
Ispitanici i metode: Istraživanje je provedeno od ožujka do rujna 2022. godine u Republici
Hrvatskoj. Prvu grupu ispitanika činili su LOM, a drugu grupu činile su žene koje boluju i liječe
se od arterijske hipertenzije. Upitnikom za LOM prikupljeni su sociodemografski podaci,
podaci o radu ambulante te mišljenja o zdravstvenoj pismenosti, kvaliteti života, snazi
religijskog vjerovanja, utjecaju COVID-19 i odnos tih varijabli na seksualne funkcije
pacijentica, te uobičajen način rada. Ispitivanje pacijentica provelo se putem upitnika pomoću
kojeg su se prikupili sociodemografski podaci, podaci o postojanju drugih kroničnih bolesti,
podaci o terapiji i vezano uz COVID-19 te upitnika FSFI, Sv. Klara – Upitnik o snazi religijskog
vjerovanja, SF-12v2 i NVS-HR.
Rezultati: Prevalencija seksualnih disfunkcija kod žena oboljelih i liječenih od arterijske
hipertenzije je 58,7%. LOM uviđaju važnost zdravstvene pismenosti, kvalitete života
pacijentica i utjecaja religioznosti na slabiju prijavu seksualnih disfunkcija. Manji broj LOM
primjećuje povezanost između korištenja antihipertenzivne terapije i seksualnih disfunkcija.
LOM vrlo rijetko ispituju pacijentice s arterijskom hipertenzijom za njihove seksualne funkcije.
Najveće barijere pokazale su se nedostatak vremena i mišljenje LOM da pacijentice ne žele
pričati o tome. LOM vrlo rijetko upisuju dijagnozu F52 u karton i najčešće predlože promjenu
terapije. Povećanje ITM povećava vjerojatnost nastanka seksualnih disfunkcija, a poboljšanje
mentalnog zdravlja, jačanje zdravstvene pismenost i snažnija religioznost smanjuju vjerojatnost
nastanka seksualnih disfunkcija kod žena oboljelih i liječenih od arterijske hipertenzije. Žene
koje su oboljele i liječe se od arterijske hipertenzije te koriste inhibitore kalcijevih kanala
(dihidropiridinske) značajno češće imaju seksualne disfunkcije.
Zaključak: Dobiven je u cijelosti značajan model koji se sastoji od četiri značajna
predskazatelja: povišen ITM koji povećava vjerojatnost nastanka te bolje mentalno zdravlje,
veća snaga religijskog vjerovanja i ograničena ili zadovoljavajuća zdravstvena pismenost koji
smanjuju vjerojatnost nastanka seksualnih disfunkcija. Slijedom dobivenih rezultata,
preventivni pristup seksualnom zdravlju biti će cjelovitiji i uspješniji.Objectives: To examine the opinions and actions of general praticioners (GPs) about health
literacy, the strength of religious beliefs, quality of life and the connection between sexual
dysfunctions and antihypertensive treatment. Furthermore, to investigate the prevalence,
predictors and relationships between health literacy, quality of life, the strength of religious
beliefs, the type of antihypertensive therapy and the frequency of sexual dysfunctions in women
suffering from and being treated for arterial hypertension.
Study Design: Cross-sectional study
Participants and methods: The research was conducted from March to September 2022 in
Republic of Croatia. The first group of participants were GPs, and the second group consisted
of women suffering from and being treated for arterial hypertension. The examination for GPs
was carried out using a questionnaire through which socio-demographic data, data on the
clinic’s work and GPs opinions on health literacy, quality of life, strength of religious belief,
the impact of COVID-19, their common practice, and the overall relationship of these variables
in contrast to the patients’ sexual functions, were examined. The examination for female
patients was conducted through a five-part questionnaire, which collected sociodemographic
data, data on the existence of other chronic diseases, data on therapy, questions related to
COVID-19 and the FSFI questionnaire, the Santa Clara Strength of Religious Faith
Questionnaire, SF-12v2 and NVS-HR.
Results: The prevalence of sexual dysfunctions in women suffering from and being treated for
arterial hypertension is 58.7%. GPs recognize the importance of health literacy, the patient's
quality of life, and the influence of religiosity on the lower reporting of sexual dysfunctions.
Fewer GPs note the relation between the use of antihypertensive therapy and sexual
dysfunction. GPs very rarely examine patients with arterial hypertension for their sexual
functions. Lack of time and GPs opinion that patients do not want to talk about it proved to be
the biggest barriers. GPs very rarely write the diagnosis F52 (Sexual diagnosis) in the record
and most often suggests a change of therapy. An increase in Body Mass Index increases the
likelihood of sexual dysfunctions, while improving mental health, strengthening health literacy
and stronger religiosity reduce the likelihood of sexual dysfunctions in women suffering from
and treated for arterial hypertension. Women who are being treated for arterial hypertension
and use calcium channel blockers (dihydropyridine) significantly more often have sexual
dysfunctions.
Conclusion: A significant model consisting of four significant predictors was obtained: higher
BMI, which increases the probability of occurrence of sexual dysfunctions and better mental
health, greater strength of religious belief, and limited or satisfactory health literacy, which
reduce the probability of occurrence of sexual dysfunctions. As a result of the obtained results,
the preventive approach to sexual health will be more comprehensive and successful
Business models and firm performance in food service industry
No full textPojam poslovni model u ekonomskoj, posebice menadžerskoj literaturi sve se češće spominje, a u zadnjih 20-tak godina istraživanja na tom području prilično su intenzivirana. Autori kontinuirano analiziraju značenje poslovnih modela za poslovanje, povezanost strategije poslovanja s poslovnim modelima i nastoje identificirati ključne elemente poslovnih modela primjerima iz različitih gospodarskih djelatnosti. Interes za istraživanja na temu poslovnih modela prilično je velik, no još uvijek nema dovoljno istraživanja koja se odnose na turistički sektor i ugostiteljsku djelatnost, a pogotovo radova koji povezuju poslovni model i uspješnost poslovanja. U doktorskom radu prikazan je teorijski pregled razvoja poslovnih modela i njegovih elemenata, kako općenito tako i u kontekstu turizma i ugostiteljstva. Osim navedenoga, utvrdile su se karakteristike poslovnih modela poduzeća koja posluju u djelatnosti pružanja usluga pripreme i usluživanja hrane i pića te je istražena veza između poslovnoga modela i uspješnosti poslovanja poduzeća u djelatnostima pripreme i usluživanja hrane i pića. Empirijsko istraživanje provedeno je korištenjem primarnih podataka dobivenih analizom anketnih upitnika upućenih vlasnicima poduzeća u djelatnosti pružanja usluga hrane i pića u hrvatskom ugostiteljstvu te analizom dostupnih sekundarnih podataka. Rezultati su istraživanja pokazali da je u hrvatskom ugostiteljstvu moguće izdvojiti više različitih poslovnih modela. Identificirani poslovni modeli jesu: restorani sa širokom ponudom jela koji rade cijele godine, sezonski restorani sa širokom ponudom jela, restorani sa širokom ponudom jela i dodatnom uslugom koji rade cijelu godinu, restorani s uskom ponudom jela i dodatnim takeaway uslugama i uslugama dostave koji rade cijelu godinu i restorani s širokom ponudom jela, dodatnom uslugom cateringa koji rade cijelu godinu. Uz identificirane poslovne modele, dobiveni su i rezultati koji impliciraju kako su poslovni modeli s izuzetno izraženom komponentom dodatne usluge dostave i takeaway usluge uspješniji od ostalih. Nadalje, rezultati istraživanja impliciraju da poslovni modeli s implementiranim elementima poslovnoga modela limitirane ponude, dodatne usluge dostave i usluge takeaway ostvaruju bolje financijske rezultate. Originalnost rada prepoznaje se u činjenici da se istraživanja poslovnih modela s fokusom na ugostiteljstvo i segment pružanja hrane i pića ne provode dovoljno u Republici Hrvatskoj, a ni u svijetu. Teorijski doprinos istraživanja proizlazi iz teorijske analize karakteristika poslovnih modela u turizmu i ugostiteljstvu s naglaskom na djelatnost pripreme i usluživanja hrane i pića. U kontekstu ugostiteljskoga poslovanja nema dovoljno istraživanja koja definiraju elemente poslovnih modela poduzeća, koja djeluju u ugostiteljstvu u djelatnosti pripreme i usluživanja hrane i pića. Isto tako, nema dovoljno istraživanja u kojima se stavlja u odnos dizajn poslovnoga modela ugostiteljskoga poduzeća s rezultatima njegova financijskog poslovanja. U ovom radu identificirani su elementi poslovnih modela ugostiteljskih poduzeća, prikazani su različiti poslovni modeli poduzeća u ugostiteljskoj djelatnosti te su identificirane specifičnosti poslovnih modela u segmentu poduzeća koja djeluju u ugostiteljstvu. Empirijski doprinos istraživanja proizlazi iz identificiranja različitih poslovnih modela poduzeća koja djeluju u djelatnosti pripreme i usluživanja hrane i pića te utvrđivanja veze između poslovnoga modela te uspješnosti poslovanja poduzeća u djelatnosti pripreme i usluživanja hrane i pića. Sličan pristup istraživanju identificiran je samo u jednom radu i to na području Rusije, koja obuhvaća prilično veliko tržište u odnosu na hrvatsko tržište te samim time na takvom tržištu moguće su, velike različitosti u poslovanju poduzeća. Također, Rusija nije toliko turistički orijentirana u smislu sezonskoga načina rada, kao što su zemlje poput Hrvatske, Španjolske, Turske, Grčke i drugih sličnih zemalja, pa ovaj rad sa zaključcima koji su proizašli iz empirijskog dijela istraživanja, značajan za zemlje sličnih gospodarskih prilika. Empirijski doprinos vidljiv je i u metodološkom pristupu kroz upotrebu klaster analize u svrhu identificiranja različitih poslovnih modela poduzeća u ugostiteljstvu, koji se može primijeniti i u budućim istraživanjima sličnoga tipa u sklopu neke druge djelatnosti te korištenjem drugih nezavisnih i zavisnih varijabli. Aplikativni doprinos istraživanja proizašao je iz identificiranja poslovnih modela i elemenata poslovnih modela za koje se utvrdilo da omogućuju bolji financijski rezultat. Rezultati istraživanja mogu se direktno primijeniti u poslovnim sustavima koji provode ugostiteljsku djelatnost pružanja usluga hrane i pića.When doing business, entrepreneurs are aware of numerous opportunities to achieve additional value by implementing various ideas in different business segments. Despite this, in practice, it has been shown that more than good ideas are needed to break through and compete in the market to achieve the desired goals. New participants are constantly entering the market whose business is based on different methods, new approaches, and new products, in other words, new business models to achieve the highest possible profit and sustainability on the market. Each company has its own business model and, depending on the design of the business model, achieves a particular position in the market and specific financial results.
The term business model is frequently used, especially in management literature, and in the last 20 years, the publication of papers in this field has intensified. The term itself has been perceived and defined in various ways, so there needs to be more consistency in its definition and interpretation. Also, the term has been defined and understood differently in various economic areas and thought history has been considered an essential construct in several research fields. The most frequently mentioned and used elements in research are value proposition, value creation, customers, resources, and revenues. Consistency in naming and using these terms is noticed only in the concept of the value achieved through the various activities of the company. In almost all research papers, the term value proposition is mentioned as a foundational and essential element of every business model. The authors continually analyse the significance of business models related to company performance and the relationship of business strategy and business models. They try to identify the key elements of business models by using examples from different economic activities. Although the interest in business model research is extensive, and numerous papers have already been published on this topic, not enough research is being done on the tourism or hospitality industry.
The purpose of this research was to determine various business model designs implemented by companies in the food and beverage industry and to find and identify correlations between different business models and the company´s financial performance. By analyzing business models and comparing a larger sample of firms operating in the hospitality industry, specifically in food and beverage service activities, the relationship between business model design and business performance in the hospitality industry is explored. This thesis presents a theoretical review of the development of business models and their elements, both in general and in the context of the tourism and hospitality industry.
The business model in the hospitality industry includes three key components: the operating model, which represents the way in which value is created for the company; the economic model, which includes income drivers and an approach to creating sales prices; and the strategic model, which defines the market and how to approach a company’s growth. Essential elements, with specific items singled out for companies dealing with preparing and serving food and drinks, are products, value creation and growth, and profit realization. The products that enter the operational dimension of the business refer to the breadth of the range of dishes in all categories of the offer. Value creation, also an operational component, refers to how the service is offered, whether ready or semi-ready meals are used or if meals are created on the spot; whether a full table service is provided or the guest serves themselves; and the possibility of delivering additional services such as the possibility of taking food outside the restaurant (take away), preparing food in the facility and serving services at another location (catering), and the possibility of delivering food (home delivery) to another location. Utilizing a model that contributes to achieving company growth and profit realization, the economic and strategic components of business determine whether the company will operate through one catering facility or several catering facilities, separately or in a chain, and from a geographical point of view, whether the facilities are local, regional or nationally oriented, and whether the company operates according to its own strategic framework or bases its business on a franchise agreement.
The analysis was performed on a sample of 147 companies in the Republic of Croatia operating within the food and beverage service industry. A cluster analysis was conducted to define specific groups of food and beverage companies with specific business elements and characteristics. The parametric t-test and the ANOVA method of linear modelling were used to explore the mutual relationship between a company’s business model and performance measures. The findings reveal statistically significant relationships between the variables used in the research based on the selected sample and the obtained clusters of companies. In addition, the characteristics of companies´ business models in the food service industry were determined, and the impact of individual business model designs on company performance was tested. Empirical research was carried out using primary data obtained by analyzing survey questionnaires addressed to the owners of the company providing food and beverage service activities and by analyzing available secondary data.
The findings proved that, in the Croatian hospitality industry, there is a possibility of singling out several different business models. The identified designs of business models include: “Restaurants with a wide range of dishes that operate all year round,” “Seasonal restaurants with a wide range of dishes,” “Restaurants with a wide range of dishes and additional services that operate all year round,” “Restaurants with a narrow range of dishes, additional services take away and food delivery, that operate the whole year,” and “Restaurants with a wide range of dishes, with an additional catering service that works all year round.” It was also found that there is a difference between individual elements of business models and financial business performance. Accordingly, companies with a business model that includes additional services for food delivery, takeaway, or limited offers of food and beverages achieve better financial performance.
The theoretical contribution of this research is observed through the theoretical analysis of the characteristics and business model designs in the tourism and hospitality industry with an emphasis on food and beverage services. Authors who previously researched this field state in their conclusions that it would be desirable to conduct additional research and consider companies that are more similar in their business model and are operating in the same field to gain a better understanding of the topic. Only when this is achieved could better conclusions be drawn about the impact of business models on company operations because the results obtained so far are too generalized. The theoretical contribution is also visible in the methodological approach. The use of cluster analysis for the purpose of identifying different designs of business models of companies in the hospitality industry can be replicated in future research of a similar type within another industry and by using other independent and dependent variables.
The contribution of empirical research results from the determination of different business models of companies that operate in the food and beverage service industry and identifying the correlation between the design of the business model and the financial performance of the company.
The applicable contribution of the research is reflected in the identified business models and elements of business models that have been found to enable better financial performance. Companies that can identify the key elements of their business in time, implement their business model, and find new ways in which they can continuously innovate will be able to understand better and utilize the possibilities for adapting as quickly as possible to a dynamic and challenging market.
The originality of this thesis is recognizable in the fact that research on business models focused on providing food and beverage service activities has not been explored to a sufficient extent, neither in the Republic of Croatia nor internationally
Afirmacija smisla života u romanima Michaela D. O'Briena
No full textThe doctoral thesis studies the topic of the affirmation of the meaning of life in the realistic novels by Canadian Catholic author Michael D. O’Brien through Viktor Frankl’s logotherapy and existential analysis and the theological-philosophical approach of Christian anthropology. Through stories about the spiritual journey of an ordinary person, O’Brien explores metaphysical questions of discovering the meaning of life through deeds, love, faith, and the acceptance of suffering, while affirming the uniqueness and value of every human life and addressing the concepts of spirituality, freedom, responsibility, and conscience. Similarly to O’Brien’s novels, Christian theology and philosophy, as well as existential analysis and logotherapy, take the spiritual dimension of human beings as their starting point and deal with the question of the meaning of life, providing answers compatible to O’Brien’s. According to existential analysis and logotherapy, each person has the responsibility to discover the meaning of their life through self-transcendence, which is realized through deeds, experiences such as love, and their attitude toward inevitable suffering. Christianity provides an ontic foundation to this phenomenological manifestation of meaning. This foundation is God, who is love, so that, according to Christianity, the experience of meaning is in the experience of love, by which man is saved. Salvation thus represents the ultimate meaning of life. The aim of this research is to study, describe, and typify the affirmative elements that represent the meaning of life in Michael D. O’Brien’s realistic novels as well as to determine whether O’Brien’s novels belong to high or popular literature.Doktorska disertacija proučava temu afirmacije smisla života u realističkim romanima kanadskoga katoličkog književnika Michaela D. O'Briena primjenom egzistencijske analize i logoterapije Viktora Frankla te teološko-filozofskog pristupa kršćanske antropologije. Pričama o duhovnom putovanju „maloga“ čovjeka, O'Brien se bavi metafizičkim pitanjima o otkrivanju smisla života putem djela, ljubavi, vjere i prihvaćanja patnje, afirmirajući jedinstvenost i vrijednost svakoga ljudskog bića te baveći se konceptima duhovnosti, slobode, odgovornosti i savjesti. Kršćanska teologija i filozofija te egzistencijska analiza i logoterapija za svoje polazište uzimaju čovjekovu duhovnu dimenziju te se bave pitanjem smisla života, dajući odgovore kompatibilne O'Brienovima pa su stoga upotrijebljene kao teorijski okvir ove analize. Prema egzistencijskoj analizi i logoterapiji, svaka je osoba odgovorna za otkrivanje vlastitoga životnog smisla. Cilj je ljudske aktivnosti realizacija vrijednosti, a tri su tipa vrijednosti: stvaralačke, doživljajne i vrijednosti stava. Sve se one ostvaruju sebe-nadilaženjem. Ovomu fenomenološkomu očitovanju smisla kršćanstvo pruža ontički temelj. Taj temelj jest Bog, koji je ljubav, tako da je, prema kršćanstvu, iskustvo smisla u iskustvu ljubavi, po kojoj se čovjek spašava. Spasenje stoga predstavlja konačni smisao života. Cilj ovog istraživanja jest proučiti, opisati i tipizirati afirmativne elemente koji predstavljaju smisao života u realističkim romanima Michaela D. O'Briena te utvrditi pripadaju li O’Brienovi romani visokoj ili popularnoj književnosti
The aspects of the concept of time in the philosophy of Nikolai Berdyaev
No full textPod okriljem hipoteze rada da je vrijeme temeljni pojam filozofske misli Nikolaja Aleksandroviča Berdjajeva, ovaj rad za cilj ima pokazati prisutnost pojma vremena u ključnim dijelovima njegove filozofije, a osobito pojma vječnosti kao vremenske i vanvremenske kategorije. U svrhu ostvarenja zadana cilja, uvodna riječ rezervirana je za postavljanje onoga kako i zašto prilikom analize Berdjajevljeve misli o vremenu, gdje se pokazuje kako je njegovo poimanje vremena usko povezano s načinom na koji on pristupa životnim i filozofskim problemima. Zbog te povezanosti donesen je i biografski prikaz života Nikolaja Aleksandroviča, u kojem se otkriva kako je vrijeme u kojem je živio i djelovao utjecalo na oblikovanje njegova pojma vremena. Unutar i izvan krugova u kojima se kretao, njegova misao o vremenu oblikuje se u njegovu zauzimanju stava u odnosu na vlastite suvremenike, kritičare, kulturu, religiju, spisateljsku djelatnost i pitanje smisla života u cjelini. Filozof Berdjajev dobro je upoznat s načinom na koji vrijeme shvaćaju njegovi filozofski prethodnici, ali i suvremenici, zbog čega ovaj rad u sažetom prikazu donosi pregled problematike vremena, kod relevantnih filozofima i struja, kako bi se ukazalo na posebnost Berdjajevljeva poimanja vremena. Pojam vremena kod ruskog filozofa u ključnim vidovima njegove misli odražava svijest o tome kako se pojavnost vremena može razumjeti i objektivno i subjektivno, što se u njegovoj misli odražava u tome kako on razrađuje sljedeće pojmove: objektivacija, metafizika povijesti, kozmičko, povijesno i egzistencijalno vrijeme i aktivno-stvaralački eshatologizam. Aspekti pojma vremena u njegovoj filozofiji: vječnost, odgovornost, osoba, sloboda i stvaralaštvo, kako ovaj rad nastoji pokazati, nerazdvojivi su elementi njegove filozofske misli koju je on razradio u jedinstvenu cjelinu filozofske argumentacije i teoloških uvjerenja, u kojoj se vrijeme ne može pojmiti razdvojeno od vječnosti i vječnost razdvojenu od vremena. U kontekstu filozofsko teološke usmjerenosti njegovih argumenata, Berdjajev, kako ovaj rad želi pokazati, vrijeme poima kao stvarnost koja nastaje odnosom čovjeka prema svijetu i vječnosti. Vrijeme je za njega sudbina čovjeka koji zalaganjem, odgovornošću, osobnošću, slobodom i stvaralaštvom u vremenitoj povijesti uspostavlja vječno-božansku stvarnost dajući trenutan, ali i konačan (eshatološki) smisao cjelokupnom kozmosu.In this doctoral thesis entitled The Aspects of the Concept of Time in the Philosophy of Nikolai Berdyaev, I attempt to show that the notion of time is crucial for understanding Russian philosopher Nikolai Berdyaev. I argue that the concept of time and aspects of time are present throughout Berdyaev’s philosophical thought. Furthermore, I wish to show that the entirety of Berdyaev’s philosophical thought is interwoven with the notion of time and cannot be understood separately from time, as a timely and supra-timely category, along with the aspects of time: the dynamic eternity, responsibility, person, freedom and creativeness. The introduction to the thesis explains that Berdyaev’s philosophy is a meaning-oriented system, as the Russian philosopher is not merely a philosophical thinker, but also a seeker of the meaning of life. In that way, he is also a seeker of a higher meaning and of the mystical, divine knowledge, which is why, when one talks about Berdyaev’s philosophy, one cannot talk about a system of philosophy. Topic-wise, Berdyaev is seemingly philosophically everywhere. He’s interested in philosophy out of love for wisdom, as somebody who is in awe of life’s mysteries, which is why he discusses multiple topics multiple times, from multiple angles, in different contexts. When researching Berdyaev, everything matters and all topics are interconnected by his attempts to find the meaning of life. In that way, Berdyaev’s philosophy opens up as a triad of topics about: the man, the world, and God. Time in Berdyaev’s thought is indistinguishable from these three topics, and is related to his attempt to give life meaning within eternity, which presents itself to the ever-changing world as a never-changing constant. To show this, a biography of Nikolai Alexandrovich Berdyaev is given, through which I attempt to point out that in order to understand his concept of time, one must know the person behind the name and be familiar with the circumstances of his life. His biography shows that his notion of time is related to what he has experienced in life while searching for meaning in the circumstances life has presented him with. As he lived in „interesting times”, where the world around him was ever-changing, he began to experience life through a lens of eternity, sub specie aeternitatis through which he could give meaning to his current and future predicaments. In that way, his thought formed around the crucial role of man within creation, specifically, man as a personality, man as a being of freedom, God-man, man as a creator, man as a steward of creation. Berdyaev’s thoughts were formed within the discourse with his contemporaries. In his early days, he set up a belief within himself that philosophy is a search for meaning. That process was ongoing during his student years when he was a Marxist supporter, then in exile when he broke up with the Marxists and the Leninists, and before the revolution in Moscow within various Moscow groups: the God-seekers, the cosmists, the idealists, the symbolists, the existentialists and other groups in which he and others formed the core of what became known as the Russian religious renaissance. Also in Europe, where he was exiled along with the others, and where he again experienced the uncertainty of all things within this timely realm. Despite the turbulent times, Berdyaev became renowned and influenced many contemporary thinkers. What is important is that the notion of time in his philosophy is deeply connected to the experience of dialogue. Berdyaev was well aware of the philosophical problems of the time and was in close contact with many contemporary authors. The specific difference between Berdyaev and his predecessors needs to be shown, as well as how he differs in understanding the notion of time from his contemporaries. In light of the topic, and since many authors deal with the problem of time, I consider time in light of the fenomenon, under the light of introspection, temporality and history. These three „philosophical pillars” of the notion of time are always present when one philosophically considers the notion of time. First, time is certainly a phenomenon, an appearance, something that presents itself to the observer, and something that can be thought of independently, separate from other existing objects. Secondly, time has a quality of something intimate, something felt inside the one who senses time. Time is something that can be understood only by introspection, and according to some philosophers, time does not exist objectively and is always subjective. Third, the notion of time is the notion of history, of temporality and is understood as a period, an era or a space in which the events unfold progressively towards a future goal or end. None of the them philosophically provide an answer to the problem of time, only the context in which time must be viewed to be understood. To understand the nature of time, one can argue with Berdyaev that time encompasses three notions: the cosmic time, the historical time, the existential time. Existential time is the base time, cyclical time, a circle of motion ordained by the cosmos in which all life lives and breathes. The historical time represents an arrow, and is separated from the „time-circle” by intention. History has a direction, and is aimed at a certain end. Here, in the realm of the historical, man is lifted above the base and the carnal time, but is still subjected to and enslaved by progress, by the idea of a better tomorrow that never comes. Because of that, Berdyaev posits a third notion, the notion of existential time in which time is condensed into a point, in which time is experienced not as the immediate, now, but as a presence, an existens, as a living. The idea of existential time for Berdyaev is connected with the notion of eternity as an all-encompassing and ever-present reality of God, who can be understood as He who is present. With that in mind, existential time becomes a reality of opportunity in which a person becomes an associate of the divine, the one who ushers in eternity into time. It is important to note that the notion of time in Berdyaev’s philosophy is connected to eternity, in which all time-history becomes part of a larger divine reality. Therefore, according to Berdyaev, there exists a Metahistory in which eternity can enter into time and time can influence eternity. I argue that the notion of time in the philosophy of Nikolai Berdyaev, is based on his concept of the metahistorical and that if eternity can enter time and time can enter eternity, all of time becomes a reality, a realm of the real, where there is actually no time per se, but a net of responsibility which is constructed by overlapping timelines. Time itself is a reality, a matrix of sorts, and beings are the ones who construct that time matrix with their daily decisions. That way human beings are the active-creative participants in the eschatological process, as they decide the outcome of their strains of time, which in turn interact with other time-strains and form the reality of time. The active-creative-eschatology also means that human actions are decisive, irreversible, and once realized create ripples through time and space. Connected with that, Berdyaev’s notion of eternity can be further expanded by linking it with the metahistorical with the active-creative-eschatology and making it the prime reality composed of time, the eternal, and the realm of God. Thus conceived, eternity becomes a dynamic concept, with its own inner workings and movements. Eternity becomes a realm in which the things that are eternal influence the temporal, in which temporal interacts with the eternal. The reality in which the presence and certainty of God affects time, and the eternal things, and in which time and eternal things contribute to the inner workings of the realm of God. It is my argument that eternity can be comprehended as a constructional reality, that eternity in fact is constructed with the support of time, and more specifically, that human decisions shape eternity. That is why the aspects of the notion of time in Berdyaev’s philosophy: 1) responsibility, 2) the persona, 3) freedom, and 4) creativeness, play a big part in comprehending the nature of time. Time is formed, created in freedom, freedom that, as Berdyaev points out, is ungrounded before being, before the first action of God. Beings are free, free to be maximally responsible, to take care of themselves and others in a sub specie aeternitatis way, always keeping in mind the last things, the final result which, whether good or bad, has consequences for all the others, affected or unaffected. Being maximally responsible is indeed an aspect of time, as consequences of one’s actions form a ripple effect within reality, resulting in the formation of what others perceive as events in time or immediate reality. Time is also connected to the notion of personhood, to the idea that human beings can become authentic entities, free entities that can, within time, creatively surprise even God. Inside the mask of a persona, a subject within time can transcend time, can rise up from the cycle of life and death, and step into the realm of recorded history, the realm of the spirit, and even further, into the realm of existential creativeness. As Berdyaev puts it, the subject does not create the world, God does, but God creates creative subjects, who are called to creativity, to discover the person, to answer the call of freedom, the call of the divine. In answering the call of the divine, man can truly become the associate of God, the divine human who governs over all of creation, over all of time. But, as it needs to be noted, man can also answer the call of the devil and become the ultimate destructor. Nevertheless, man is a being of creativeness and the construction of time depends on his actions, whether good or bad. Time is being constructed with every act, whether that act is passive or active, positive or negative; one act affects all others and all others affect the one. The creation of time does not merely include freedom and requires that people act responsibly, but also that the creator of time is satisfied with the choice he made through his actions, as he is the one who will need to live with the consequences of the deed once it is done. In conclusion, this thesis has shown the complexity of Berdyaev’s thought, as well as the complexity the notion of time has in his philosophy. Furthermore, the thesis has defended its hypothesis that time is linked with eternity as a timely and un-timely category. The thesis has also shown that Berdyaev’s thought cannot be researched independently from the aspects of time: dynamic eternity, persona, creativeness and responsibility – they are the key points in Berdyaev’s opus
Principles of local history materials organization in online environment
No full textZavičajna građa, tradicionalno dio zbirki informacijskih ustanova, suočava se s promjenama u načinu organizacije u mrežnome okruženju, dok te promjene ne prate sustavno teorijsku razinu. Disertacija nastoji popuniti ovu prazninu zasnivanjem istraživanja kvalitativnoga nacrta i prema metodologiji utemeljene teorije, pri čemu su prepoznata četiri istraživačka problema i planirana cilja, a na temelju provedenoga istraživanja, izvedeni su i pripadajući rezultati: (1) Nedostatak sustavnoga opisa i znanstveno jasno oblikovanih načela organizacije zavičajne građe u mrežnome okruženju doveo je do razvoja teorijskoga elaborata koji razrađuje načela i koncepte organizacije ove građe. (2) Dosadašnji pristup u teoriji organizacije zavičajne građe ograničava se na zavičajne zbirke u informacijskim ustanovama, zanemarujući one koje stvaraju građani i druge ustanove, a kao rezultat navedenoga nastojanja stvoren je teorijski elaborat koji se sastoji od načela organizacije mrežne zavičajne građe i koji je stvaran po principu teorijskoga uzorkovanja, pa su tako u istraživački uzorak uključena mrežna mjesta informacijskih ustanova, ali i ona koja nastaju radom zainteresiranih građana ili drugih vrsta ustanova neovisnih o informacijskome i baštinskome sektoru. (3) Zbog nepostojanja jasno definiranih načela, upitni su kriteriji vidljivosti i održivosti zavičajne građe u cjelokupnosti umreženoga svijeta, a kao rezultat ispostavljen je teorijski elaborat koji se sastoji od 13 koncepata, 13 načela i 4 tvorbena koncepta. (4) Testiranjem metodologije utemeljene teorije u polju informacijskih znanosti, dokazano je da se ona može uspješno primijeniti u istraživanju informacijskih sustava na temelju uspješno izvedenoga istraživačkog rezultata, tzv. utemeljene teorije, odnosno teorijskoga konceptualnog modela i teorijskih načela organizacije zavičajne građe u mrežnome okruženju. Ključni doprinosi istraživanja nalaze se upravo u otkrivanju složenosti interakcije među glavnim konceptima organizacije mrežne zavičajne građe. Rezultati istraživanja otvaraju novu perspektivu na područje organizacije mrežne zavičajne građe, na samu mrežnu zavičajnu građu, kao i na zavičajni mrežni sadržaj kao takav, odnosno, u širemu smislu na fenomen zavičajnosti u mrežnome okruženju. Rezultati sugeriraju da ovo područje nije potpuno istraženo ako se fokusira isključivo na mrežna mjesta informacijskih i baštinskih ustanova, što otvara prostor za daljnje teorijsko istraživanje složenih odnosa između pojedinih identificiranih koncepata, kategorija i načela, kroz istraživanje dviju identificiranih skupina istraživačkoga uzorka.The field of information sciences represents an interdisciplinary and complex segment within the social sciences, and ideally, it involves dynamic research and up-to-date descriptions of phenomena, concepts, and ultimately, corresponding theories. In reality, however, it is common for established theories to quickly lose relevance and fail to encompass the totality of phenomena in new contexts. One such case is local heritage material, traditionally considered part of local collections in information institutions, which, in the past two decades, has undergone significant changes in its organizational contexts and conditions, though these changes have not been systematically recorded at the theoretical level. A review of previous theory and the state of research, literature, and existing works in the field of local heritage and the organization of local content and materials reveals a research gap in the comprehensiveness or totality of theoretical and research perspectives on the given problems. Scholars and experts have explored certain segments of this topic, investigating and writing about various subjects and phenomena that partially touch upon the issue of organizing local heritage material online. However, there is no comprehensive study that addresses the principles of organizing local heritage material on the web, encompassing materials organized both by information or heritage institutions (GLAM) and by entities outside the information and heritage sectors or groups of interested citizens. This doctoral dissertation aims to defend the idea of developing theoretical and data-driven principles for organizing local heritage material in an online environment by researching websites that host such material, using the methodology of grounded theory. The motivational idea presented in the synopsis of this dissertation relates to the complexity and comprehensiveness of the approach, which has not been clearly recognized in existing research that focused on some aspects of this area, but certainly not on a comprehensive approach. The general research issue prompting further inquiry arises from the fact that previous studies on local collections have focused on websites associated with information institutions such as archives, libraries, or museums, while websites hosted by other institutions, organizations, associations, and volunteer groups have been studied separately. For this reason, the research is based on the concept of local heritage material, allowing for a sample selection according to a theoretical criterion, namely the content and theoretical relevance of the material for the phenomenon of local heritage, regardless of the organizer or other formal conditions of the website. By including websites from various initiators and organizers, the perspective is broadened, opening up additional possibilities for analysis, especially regarding user needs, which become precondition for user-centered design. Emphasis is placed on a comprehensive and complex approach. In considering the research problems and goals on which the synopsis of this doctoral dissertation is based, articulated through four points, the results of the research and conclusions can also be analyzed through these four points. The first research problem, which highlights the absence of systematic descriptions or scientifically well-defined principles for organizing local heritage material in an online environment, leads to the research goal of providing a detailed description of the organization of online local heritage material. The result is a comprehensive theoretical elaboration that develops principles and concepts for organizing local heritage material online. The second research problem indicates that the theory of organizing local heritage material is limited to describing local collections in information institutions and does not include collections created through the efforts of interested citizens. This leads to the research goal of generating principles for organizing online local heritage material based on data obtained from website research. As a result, a theoretical elaboration is created, consisting of principles for organizing local heritage material online, which were developed through theoretical sampling. The sample includes websites from both information institutions and local collections created by interested citizens or other institutions outside the information and heritage sectors. The third research problem identified in this context is that, due to the lack of well-defined principles for organizing local heritage material online, the criteria for the visibility and sustainability of this type of material in the broader networked world are unclear. This problem leads to the goal of providing solutions through systematic and clear principles to ensure the sustainability of local heritage material in an online environment. The outcome of this goal is a theoretical elaboration consisting of 13 concepts, 13 principles, and 4 formative concepts. The model is presented with a clear articulation that shows their connections and is grounded in research data, which are prerequisites for practical implications of sustainability for local heritage material in an online environment. The fourth research problem relates to the methodological level—it was observed that there are no clear and systematic outcomes from applying the grounded theory methodology in the field of information sciences, particularly in studies of information systems. Consequently, the research goal was to test the applicability of grounded theory in information sciences. The result of this research is the demonstrated potential for applying grounded theory in the field of information sciences, particularly in the study of websites as information systems, with positive outcomes. The research successfully generated a result known as grounded theory, or a theoretical conceptual model and principles for organizing local heritage material in an online environment. Each research problem indeed motivated a specific research goal, expressed in an action-oriented form, guiding the steps and progression of the research process. In developing the research strategy for this dissertation, grounded theory was chosen due to its observed applicability in information sciences, based on the inductive and qualitative methodological predisposition of the research problems and goals. This methodology, primarily developed in sociological research circles, is suitable for studying phenomena that change rapidly and require the generation of a theoretical description based on primary research data in a short period. It has been recognized as appropriate for this dissertation. What is certainly novel in the research approach proposed in this work is the idea that the concept of local heritage material is freed from its exclusive reliance on institutional work and collection-focused research approaches. The research starts from the smallest unit common to all types of websites that host local heritage material—the unit of local heritage material itself. Local heritage material is considered an independent unit relative to other materials on websites based on the content (and sometimes formal) criterion of local relevance, that is, belonging to a local heritage context. The common expression of "local heritage" in Croatian language and librarianship (and other professions) is "zavičajna baština", which has a meaning similar to the concept of homeland, while in other linguistic and cultural traditions, the term is based on the meanings of locality and local history. Accordingly, the research includes websites with terms such as "local collection" or "local history collection" in English. Based on this approach of studying materials rather than collections or institutions, the research also includes websites featuring local heritage material created by citizens, such as participatory collections or local heritage collections on social media. This inclusion allows individuals from the local area, groups of citizens, and volunteers to be equally represented in the research context alongside the traditional hosts of websites featuring local heritage material. To summarize: the research problems motivating this dissertation are connected to the organization of local heritage material in its changed online context. The research will encompass various websites hosting local heritage material, and it is important to emphasize that both local heritage materials organized in collections by information institutions and those organized by citizen groups will be studied. The goal of this work is to review and describe the current state of online organization of local heritage material and, based on data analysis, ultimately generate principles for organizing local heritage material in an online environment. The original scientific contribution of this dissertation is expected to come in the form of an original research report and the application of grounded theory in the field of information sciences, with the goal of generating modern and comprehensive principles for organizing local heritage material online. Clear principles for organizing local heritage material contribute to the visibility and sustainability of information institutions in the networked and online world. The methodological contribution is also significant, as the application of grounded theory in information sciences, especially in the study of information systems, has not been significantly or sufficiently documented. Therefore, the research component of this work will provide an opportunity to test and demonstrate the applicability of grounded theory in information sciences, specifically in the study of information systems. The key contributions of this research lie in revealing the complexity of the interaction among the main concepts of organizing online local heritage material, which has not been previously recognized in the literature. Based on an analysis of research data using the grounded theory methodology, a conceptual model was developed, illustrating how the 13 central concepts related to the organization of online local heritage material are based on 13 theoretical principles concerning the phenomenon of local heritage in an online environment. This provides a new perspective on the organization of online local heritage material, the material itself, and local heritage content in general, offering practical implications for both further theoretical research and practice. In conclusion, this research highlights the need for continued study of the organization of local heritage material in the online environment, as the field possesses a number of distinctive features that differentiate it from other areas of the digital world. These distinctions are reflected through categories identified inductively, starting from the specific data, followed by the grouping of items, and ultimately by identifying categories and concepts. While the names of the concepts may resemble general concepts in the digital organization of materials, the underlying categories and properties reveal the specific nature of this field. The theoretical principles outlined in this dissertation, such as the principles of micro-linguistics (N3), spatial belonging (N4), local strategy (N6), local or regional studies (N7), and community (N9), underscore the distinctiveness of organizing local heritage material. This doctoral dissertation is a proposal for approaching this complex and specific information and heritage phenomenon, as well as a reminder of the importance of developing theoretical thinking about constantly changing phenomena in the dynamic online environment
Influence of corneal biomechanics on surgically induced astigmatism after cataract surgery in pseudoexfoliative syndrome
No full textKornealna histereza (CH) i kornealni faktor rezistencije (CRF) kornealna su biomehanička svojstva koja mogu utjecati na postoperativni astigmatizam nakon operacije katarakte. Pretpostavlja se da pacijenti s pseudoeksfolijativnim (PEX) sindromom imaju promijenjene, odnosno niže vrijednosti kornealnih biomehaničkih svojstava u odnosu na pacijente bez PEX sindroma. Cilj je ovog istraživanja bio razjasniti ponašanje rožnice i utjecaj njenih biomehaničkih svojstava na postoperativni astigmatizam kod pacijenata s PEX sindromom nakon operacije katarakte.
74 pacijenta (oka) kojima je operirana katarakta u Klinici za očne bolesti KBC-a Zagreb uključena su u ovo prospektivno opservacijsko istraživanje i praćena tijekom 30 dana. Operaciju katarakte je izveo jedan operater metodom fakoemulzifikacije kroz kornealnu inciziju veličine 2,75 mm smještenu na 12 sati. Svim su pacijentima preoperativno i postoperativno 1., 7. i 30. dana učinjeni oftalmološki pregled, mjerenje kornealne biomehanike i snimka kornealne topografije.
Analizom podataka utvrđeno je da pacijenti s PEX sindromom imaju niže vrijednosti CH-a i CRF-a u odnosu na kontrolnu skupinu, no razlika nije bila statistički značajna. Nadalje, pacijenti s PEX sindromom imali su na svim pregledima statistički značajno veći kornealni astigmatizam nego ispitanici kontrolne skupine. Pritom je u obje skupine postoperativni astigmatizam bio statistički značajno veći od preoperativnog astigmatizma.
Utjecaj operacije katarakte na biomehanička svojstva rožnice izraženiji je kod pacijenata s PEX sindromom. U prilog tome govore statistički značajno sniženje CH-a 1. postoperativnog dana i statistički značajno povećanje u razdoblju od 1. do 30. postoperativnog dana, kad su se vrijednosti CH-a vratile na preoperativne razine, dok se CRF nije značajno mijenjao tijekom postoperativnog razdoblja praćenja. U kontrolnoj je skupini došlo do smanjenja CH-a 1. postoperativnog dana uz njegov oporavak na preoperativne vrijednosti 30. dana nakon operacije, no promjene nisu dosegle statističku značajnost. CRF je u kontrolnoj skupini blago porastao 1. postoperativnog dana, nakon čega je nastupilo statistički značajno smanjenje između 1. i 7. postoperativnog dana te je 30. dana nakon operacije CRF ostao nižih vrijednosti u odnosu na preoperativnu razinu, ali se ta razlika također nije pokazala statistički značajnom.
Glavni prediktori postoperativnog astigmatizma 30. dana nakon operacije katarakte kod pacijenata s PEX sindromom utvrđeni regresijskom analizom bili su preoperativna vrijednost CH-a, vrijednost CRF-a 1. postoperativnog dana, preoperativni i rani postoperativni astigmatizam 1. i 7. dana, i preoperativna os astigmatizma, a u kontrolnoj skupini preoperativni i rani postoperativni astigmatizam, te vrijednost CRF-a 1. postoperativnog dana.
Iz utvrđenog proizlazi da biomehanika rožnice utječe na postoperativni astigmatizam samo kod pacijenata s PEX sindromom te da rožnica u ovih pacijenata pokazuje različito ponašanje pod utjecajem operacije katarakte za razliku od pacijenata bez PEX sindroma, no daljnja će istraživanja biti potrebna da bi se dodatno razjasnile točne patogenetske i kliničke promjene u rožnici i poboljšali postoperativni rezultati kod ovih pacijenata.Corneal hysteresis (CH) and corneal resistance factor (CRF) are corneal biomechanical properties that may influence postoperative astigmatism after cataract surgery. It is assumed that patients with pseudoexfoliative (PEX) syndrome have altered, that is, lower values of corneal biomechanical properties compared to patients without PEX syndrome. The aim of this study was to clarify the behavior of the cornea and the influence of corneal biomechanical properties on postoperative astigmatism in patients with PEX syndrome after cataract surgery.
Seventy-four patients (eyes) who underwent cataract surgery at the UHC Zagreb Eye Clinic were included in this prospective observational study and followed for 30 days. Cataract surgery was performed using the phacoemulsification method through a 2.75 mm corneal incision located at 12 o'clock by one surgeon. Preoperatively and postoperatively on the 1st, 7th and 30th day, all patients underwent an ophthalmological examination, measurement of corneal biomechanics and a recording of corneal topography.
Data analysis revealed that patients with PEX syndrome had lower values of CH and CRF compared to the control group, but the difference was not statistically significant. Furthermore, patients with PEX syndrome had statistically significantly higher astigmatism than subjects of the control group at all examinations. In both groups, postoperative astigmatism was statistically significantly higher than preoperative astigmatism.
The impact of cataract surgery on the biomechanical properties of the cornea is more pronounced in patients with PEX syndrome. This is supported by a statistically significant decrease in CH on the 1st postoperative day, and a statistically significant increase from the 1st to the 30th postoperative day, when CH values returned to preoperative levels, while CRF did not change significantly during the postoperative follow-up period. In the control group, there was a decrease in CH on the 1st postoperative day with its recovery to preoperative values on the 30th day after surgery, but the changes did not reach statistical significance. In the control group, CRF increased slightly on the 1st postoperative day, then a statistically significant decrease occurred between the 1st and 7th postoperative days, and on the 30th day after surgery, CRF remained at lower values compared to the preoperative level, but this difference also did not show statistical significance.
The main predictors of postoperative astigmatism on the 30th day after cataract surgery in patients with PEX syndrome determined by regression analysis were the preoperative value of CH, the value of CRF on the 1st postoperative day, preoperative and early, 1st and 7th day, postoperative astigmatism, and preoperative axis of astigmatism, and in the control group preoperative and early postoperative astigmatism and the value of CRF on the 1st postoperative day.
From the findings, it follows that corneal biomechanics affects postoperative astigmatism only in patients with PEX syndrome and that the cornea in these patients shows different behavior under the influence of cataract surgery in contrast to patients without PEX syndrome, but further research will be needed to clarify the exact pathogenetic and clinical changes in the cornea and improve postoperative results in these patients
Optimizing the process of sustainable ultrasonic and microwave protein extraction from coffee silverskin
No full textSrebrna pokožica kave (SPK) je nusproizvod klasičnog procesa prerade kave i potencijalni je
izvor nutritivno važnih spojeva (proteina, peptida, polifenola, prehrambenih vlakana i sl.) s
velikim mogućnostima primjene u razvoju funkcionalnih proizvoda. Kako bi proces
iskorištavanja SPK, ali i sekundarnih sirovina općenito, bio što održiviji te u skladu s ciljevima
održivog razvoja, vrlo je važno u tom smislu kontinuirano istraživati i unaprjeđivati
mogućnosti korištenja održivih tehnologija među kojima se posebno ističu ultrazvučna
ekstrakcija (UAE) i mikrovalna ekstrakcija (MAE). Osnovni ciljevi predloženog istraživanja
bili su istražiti primjenjivost iskorištavanja SPK kao sekundarne sirovine, a s obzirom na njezin
kemijski sastav i zdravstvenu ispravnost, ispitati mogućnosti primjene UAE i MAE u
ekstrakciji proteina i peptida iz SPK, okarakterizirati dobivene ekstrakte s obzirom na prinose
ciljnih komponenti i udjele drugih bioaktivnih sastavnica te odrediti ukupni ekološki otisak
optimiziranih ekstrakcijskih procesa. Rezultati istraživanja pokazali su da se s obzirom na
ostatke pesticida i teških metala SPK može smatrati zdravstveno ispravnom te je ona u tom
smislu iskoristiva kao sekundarna sirovina u prehrambenoj industriji. Optimizacijom
UAE/MAE pokazano je da sva tri istraživana parametra - amplituda ultrazvuka/snaga
mikrovalova (A), vrijeme ekstrakcije (B) i njihov međusobni odnos (AB), imaju značajan
utjecaj na promjenu udjela ukupnih proteina. Najveći prinos proteina (1,10 ± 0,08 mg/L)
dobiven je primjenom UAE (3 min/100 %). U slučaju MAE prinosi proteina bili su značajno
niži - najveći postignuti prinos bio je 0,77 ± 0,07 mg/L (9 min/200 W). Ekstrakti su sadržavali
sve esencijalne aminokiseline što ukazuje na prihvatljivu kvalitetu proteina i potencijal za
upotrebu u ljudskoj prehrani. Raspon veličina tri glavne identificirane skupine proteina kretao
se od 15,7 kDa do 70,2 kDa pri čemu je najmanji protein sadržavao Barwinovu domenu što
ukazuje na potencijal za dobivanje bioaktivnih peptida. Ekstrakti SPK sadržavali su značajne
količine polifenolnih spojeva, neovisno o primijenjenim uvjetima ekstrakcije. Značajno veća
potrošnja energije MAE u usporedbi s UAE doprinijela je znatno višem potencijalu globalnog
zatopljenja (GWP) te ekstrakcijske tehnike odnosno GWP ekstrakcijskog procesa iznosio je
15,5 g CO2e za MAE naspram 4,95 g CO2e za UAE. Ukupan GWP postupka izdvajanja
proteina iz SPK primjenom UAE iznosio je 509,5 g CO2e/kg otpada u slučaju odlaganja otpada
na deponij, uz mogućnost dodatnog smanjenja na 231,0 g CO2e/kg otpada u slučaju
kompostiranja preostalog otpadnog materijala. Dobiveni rezultati predstavljaju značajan
doprinos trenutačnim i ograničenim saznanjima o mogućnostima korištenja SPK kao izvora
proteina i biološki vrijednih peptida te pružaju originalan uvid u potencijal globalnog
zatopljenja procesa i ponovnog iskorištavanja SPK, a ovisno o primijenjenim ekstrakcijskim
postupcima i upravljanju preostalim otpadnim materijalom.Background. Coffee silverskin (CSS) is a by-product of the classic coffee processing and a potential source of nutritionally important compounds with great application potential in the development of functional products (e.g. proteins, peptides, polyphenols and dietary fibres). To improve the sustainability of CSS reuse (and the reuse of secondary raw materials in general) and to be in line with the sustainable development goals it is necessary to research and improve the possibilities of the use of green technologies, such as ultrasonic extraction (UAE) and microwave-assisted extraction (MAE), mainly to reduce extraction time and/or energy consumption while simultaneously reducing the use of extraction solvents. The main goals of the proposed research were to investigate the possibilities of applying UAE and MAE in the extraction of proteins from CSS and to characterize obtained extracts with regard to protein yields and structural characteristics of major protein classes (1); the proportion of other bioactive components in obtained extracts (2); and the overall ecological footprint of the optimized UAE/MAE processes applied for obtaining the CSS extracts (3).
Methods. Once the roasting of coffee was completed, the by-product - CSS was collected and further utilized in the research. Samples were obtained from Franck Ltd. (Zagreb, Croatia) and contained a mixture of 2 blends of coffee - Coffea robusta and Coffea arabica. Samples were provided in the briquette form and were processed into powder to expedite the analyses. The experimental part of this research was divided into three parts. In the first part of investigation health safety of CSS was investigated, with the aim of determining its applicability as a secondary raw material in food industry. In the second part of investigation UAE and MAE extraction processes for obtaining proteins from CSS were optimized and compared, focusing on the protein yield as the main output parameter. Extracts obtained under optimized conditions were characterized in terms of polyphenol content (1); amino acid composition (2); and content and structural characteristics of target peptides (3). In the third part of investigation the environmental footprints of the UAE/MAE processes for obtaining protein extracts from CSS were assessed and compared by the life cycle assessment (LCA) approach. The calculations
were based on obtained experimental data and additional data obtained from the industry and the chosen environmental footprint used was the Global Warming Potential (GWP). In the framework of health safety investigations CSS was analyzed for pesticide- and heavy metal residues. For pesticide determination extraction was conducted by quick, easy, cheap, effective, rugged and safe (QuEChERS) method. After that, pesticide residues were quantified by gas- or liquid chromatography coupled to a triple quadrupole (QqQ) mass spectrometry (GC-MS/MS, LC-MS/MS). Regarding the heavy metals, CSS was digested using MAE digestion and concentrations of metals were assessed by inductively coupled plasma coupled to a mass spectrometer as a detector (ICP-MS). MAE was performed by using a closed microwave extraction system and UAE was performed with the probe using deionized water as extraction agent. For the design of the experiment the input parameters were time (3, 6 and 9 min) and ultrasound probe amplitude (50, 75 and 100%)/microwave strenght (100, 150 or 200 W) with the condition that the temperature should not exceed 40 °C (to prevent protein denaturation). This approach resulted in obtaining a total of 9 MAE/UAE extracts. The main output parameter was the protein yield, while the content of polyphenols was also monitored. Each extraction was performed in duplicate. Protein concentration was determined by the Lowry method which is based on the reaction of Cu2+ with peptide bonds of proteins in an alkaline medium, resulting in Cu2+ being reduced to Cu+ that is monitored spectophotometrically. Quantitative analysis of amino acids was performed using the Waters AccQ•Tag method according to the manufacturer's instructions and included hydrolysis, derivatization of amino acids with AccQ•Fluor derivatization reagent and HPLC quantitative analysis. As a part of protein characterization, gel filtration chromatography and SEC-HPLC analysis were performed where a mixture of proteins with known molecular weight has been used to determine the molecular weight of the samples. Total phenolic content was determined spectrophotometrically by the colorimetric reaction of the Folin-Ciocalteu reagent. In this particular reaction, the reagent, which is a mixture of phosphotungstic and phosphomolybdic acid, reacts with the phenoxide ion from the sample. In the process, the phenoxide ion is oxidized, and mentioned reagent is reduced to tungsten and molybdenum oxides, which are colored blue and can be monitored spectrophotometrically. GWP of the UAE/MAE processes utilized for obtaining CSS extracts was calculated using the life cycle assessment (LCA) method. The main environmental impacts of the processes utilized for obtaining CSS extracts are related to the consumption of electricity, which primarily depends on the power and time required for extraction. For a complete GWP
calculation, it was necessary to additionally collect data on greenhouse gas emissions that occur during different phases of the CSS life cycle. Data were obtained from the CCaLC2 database.
Results. Based on the comparison of the levels of pesticides and heavy metals with maximal permissible concentrations set for food and dietary supplements, CSS samples can be considered safe and applicable for the use as secondary raw material. Out of the 265 pesticides analyzed, only three pesticides were detected in the analyzed samples: flutriafol (0.012 ± 0.002 mg/kg), imidacloprid (0.016 ± 0.002 mg/kg) and piperonyl butoxide (0.002 ± 0,000 mg/kg). Out of the heavy metals analysed, nickel (2.495 ± 0.055 mg/kg) had the highest concentration in the samples used, while lead (0.249 ± 0.077 mg/kg), arsenic (0.107 ± 0.018 mg/kg) and cadmium (0.106 ± 0.002 mg/kg) were present in significantly lower concentrations. Determined concentrations of flutriafol, imidacloprid and piperonyl butoxide residues, as well as nickel, lead, arsenic and cadmium were lower compared to maximal permissible levels. In the second part of investigations UAE and MAE procedures for extraction of proteins from CSS were optimized and compared. The tested conditions ranged from 3-9 min with 50% -100% amplitude for UAE (samples U1-U9) and 3-9 min with 100-200 W of power for MAE (samples M1-M9). Analysis of variance showed that all factors - ultrasound amplitude/microwave power (A), extraction time (B) and their mutual relationship (AB), had a significant effect on the total protein yields. The highest protein yield (1.10 ± 0.08 mg/L) was obtained by UAE with 3-minute extraction at an amplitude of 100%. In the case of MAE protein yields were significantly lower compared to UAE - the highest yield (0.77 ± 0.07 mg/L) was obtained during 9-minute extraction at 200 W. During extraction optimization, the content of polyphenols in obtained extracts was also monitored, as they are considered as valuable bioactive components for food functionalization. In UAE the highest yield of polyphenols was obtained after 9-minute extraction at 75 % amplitude (525.7 ± 0.03 mg GAE/100 g), and in MAE after 6-minute extraction at 150 W (677.8 ± 0.03 mg GAE/100 g). However, under the mild range of tested conditions (optimized for protein extraction) none of the tested factors (neither the microwave power nor the extraction time) showed significant effect on total polyphenol yields (p > 0.05). The influence of the relationship between independent variables (AA, AB, BB) was also examined, but it was not statistically significant (p > 0.05). Extracts containing the highest amounts of proteins (both obtained by MAE and UAE) were further submitted to additional determination of amino-acid composition and protein structure. CSS protein extracts contained all essential amino acids indicating acceptable protein quality and
the potential for the use in human nutrition (except no data was obtained for tryptophan (Trp) and cysteine (Cys) due to degradation that occurs during protein hydrolysis). The most abundant amino acids were: Asx (joint concentration of aspartic acid and asparagine) with concentrations of 539.66 and 533.0 μmol/L; Pro - with concentrations of 485.6 and 488.5 μmol/L; and Glx, (the joint concentration of glutamic acid and glutamine) with concentrations of 403.9 and 440.9 μmol/L, independently of the type of the extraction procedure. In the view of the protein characterization, the goal was to determine if isolated proteins contained Barwins domain, in which case they might be considered as potential sources of bioactive peptides (BAPs). BAPs can exhibit antioxidative, antimicrobial, immunomodulatory, and antihypertensive properties, which makes them valuable in terms of developing functional foods aimed at enhancing human health and preventing chronic diseases. Different protein structures were separated on the SDS among which the largest protein mass was 70.2 kDa (uncharacterized protein), and the lowest was 15.7 kDa. The smallest protein (15.7 kDa) contained Barwin’s domain which makes it interesting not only nutritionally but also as potential BAPs precursor. Considering the increasing importance of applying sustainable practices and considering the sustainability of proposed methodology, together with its economic benefits, UAE and MAE processes for obtaining protein extracts were also assessed in terms of their GWP. Namely, the bare fact of reusing waste as the source of valuable compounds presents sustainable approach – however techniques applied in that process can differ significantly, particularly in terms of solvent usage, energy consumption and consequently GWP. Our analysis showed significantly higher energy consumption of MAE compared to UAE resulting in higher GWP. The sample M2 with a GWP of 15.50 g CO2e had the highest GWP. On the other side the highest UAE GWP (sample U3) was 4.95 g CO2. GWPs obtained for 9 UAE extraction conditions ranged from 131 - 495 g CO2e/ kg of waste. Analysis showed that GWP increases with an increase in the sample's treatment time and amplitude, but the increase is more intense with increasing time. For reliable calculations, LCA needs to consider the whole life cycle of the product. Since after protein extraction 50% of raw material remains as waste, the total GWP of extracting the bioactive components from CSS and dumping the remains was calculated to be 509.5 g CO2e/kg waste. In the case of composting the remaining waste, the total GWP can be reduced to 231.0 g CO2e/kg of waste.
Conclusions. Valorisation of the CSS as a secondary raw material for obtaining polyphenol-rich protein extracts can be considered as sustainable approach based on obtained yields and
GWP of developed processes. In addition to high yields, obtained samples contained proteins with excellent amino acid composition and containing Barwin’s domain indicating potential for functional food ingredients. Both UAE and MAE can be applied for extracting proteins from CSS, where UAE results with approximately 30% higher yields compared to optimal MAE results. Additionally, GWP of MAE-assisted extraction is three times higher compared to UAE. Obtained results highlight the need to objectively analyze the "green" aspects of processing techniques, as significant differences exist among them. It also underscores the importance of considering GWP and other ecological footprint markers as key parameters during the development and optimization of processing methodologies
Modeliranje i upravljanje lebdećim vjetroenergetskim sustavom zasnovanim na Magnusovu efektu
No full textAirborne wind energy systems (AWE systems) are systems that use the energy of the wind at altitudes beyond the reach of conventional wind turbines, or at locations where erecting a conventional wind turbine is prohibitively complex, by using an airborne device (aircraft) instead of turbine blades and ropes (tethers) instead of a turbine-carrying tower. Compared with conventional wind turbines, AWE systems provide access to stronger and steadier high-altitude winds to realize significantly larger energy production and facilitate a smaller ratio of construction material per unit of produced energy. Achieving their required autonomous operation necessitates a well-designed control system, which is usually based on a mathematical model of system dynamics. This thesis considers an AWE system using the Magnus effect to induce aerodynamic forces driving a ground-based generator through a rope. The thesis first develops a system dynamics model, including the specific components such as the airborne device, the rope connecting the airborne module with the ground-based winch, and the winch connected to the generator. The emphasis is on the airborne module motion in the vertical plane aligned with the wind direction, making the planar motion dynamics model the main modelling contribution. Models of different complexities with respect to tether modelling accuracy are developed and compared regarding their utilization in subsequent control system development. The resulting model is then applied in simulation and optimization-based analyses, where an optimization problem is formulated to optimize the two control variables, the speed of rotation of the airborne module cylinder and the speed or force of the unwinding tether, to maximize energy produced during a continuously repeatable operating cycle. Next, the obtained optimal behaviour of the system is physically interpreted to provide the physical foundation required for control system synthesis. The physical insights obtained in this manner are then used to design a control system yielding energy production close to optimal. The emphasis is on supervisory control strategy accounting for dynamics of low-level cylinder motor and generator control systems. Finally, the developed control strategy is assessed and analysed in simulations regarding energy production quality and robustness against main operational parameters. Based on the corresponding comparative analysis, the final recommendations for implementing the control strategy are provided.Lebdeći vjetroenergetski sustavi (LVE sustavi) su sustavi kojima se koristi energija vjetra na nadmorskim visinama iznad dosega konvencionalnih vjetroturbina, uz upotrebu lebdećeg tijela umjesto lopatica turbina te užadi umjesto tornja koji nosi turbinu. Time se pristupa vjetrovima bitno veće prosječne snage i stalnijeg intenziteta nego kod vjetrova bliže tlu, istovremeno smanjujući masu materijala za gradnju komponenti sustava te omogućavajući korištenje energije vjetra na lokacijama na kojima bi izgradnja konvencionalnih vjetroturbina bilo suviše kompleksna ili skupa. U svjetlu značajnog i stalnog povećanja potrošnje električne energije praćenog relativno malim padom udjela fosilnih goriva u strukturi njezinih izvora, sve izraženijih problema s klimom i okolišem uzrokovanih izgaranjem fosilnih goriva, te intenziviranja globalnih napora za rješavanje tih problema, navedene prednosti LVE sustava daju snažan poticaj njihovu razvoju.
Dva osnovna teorijska režima rada LVE sustava su (i) režim otpora, kod kojeg se generatori nalaze na lebdećem tijelu te koriste silu aerodinamičkog otpora i (ii) režim uzgona, kod kojeg se generator nalazi na tlu gdje ga pokreće uže prenošenjem aerodinamičke sile uzgona. Odatle slijedi osnovna podjela LVE sustava, na sustave s nošenim generatorima (NOG), s jednim ili više generatora na lebdećem tijelu, te sustave s nepokretnim generatorima (NEG), s generatorom fiksiranim na tlu. Kod NOG sustava užad koja povezuje lebdeće tijelo s tlom ima dvostruku ulogu mehaničke i električke veze i približno je konstantne duljine. Kod NEG sustava uže je namotano na vitlo preko kojeg ciklički pokreće generator te primarno obavlja ulogu mehaničke veze. Dvije daljnje značajne podjele LVE sustava su ona s obzirom na vrstu lebdjelice, na sustave s čvrstim lebdjelicama, nalik avionima i jedrilicama, i sustave s fleksibilnim lebdjelicama, poput zmajeva i jedara sličnih padobranskim krilima, te ona s obzirom na namjenu, koja može biti proizvodnja električne energije ili pogon vozila, najčešće brodova.
Razvoj LVE sustava uključuje, među ostalim: (i) modeliranje i simulaciju dinamike sustava, (ii) optimalno upravljanje sustavom, te (iii) uključivanje u elektroenergetski sustav i s time povezano skladištenje intermitiranog izvora energije na vremenskoj skali radnog ciklusa. Kod svih vrsta sustava, jedan od ključnih zahtjeva za ostvarivanje autonomnog rada u širokom rasponu radnih uvjeta je onaj za visokokvalitetnim regulacijskim sustavom, čija se sinteza najčešće temelji na matematičkom modelu dinamike sustava i često kao međukorak uključuje optimiranje, kojim se nastoji pronaći način za optimalno (maksimalno) korištenje raspoložive
energije vjetra. To se općenito ispunjava postizanjem što većih aerodinamičkih sila kroz ostvarivanje povoljne trajektorije lebdeće jedinice u odnosu na brzinu vjetra, uz korištenje raznovrsnih aktuatora (npr. onih za zatezanje užadi koja razapinje fleksibilna jedra, zakrilcima na čvrstim krilima i sl.).
Ovaj rad nastao je u okviru FP7 projekta HAWE (High Altitude Wind Energy) te istražuje regulaciju NEG sustava kod kojeg je lebdeće tijelo valjak lakši od zraka koji, pokretan elektromotorom, rotira u struji vjetra, čime se djelovanjem Magnusovog efekta ostvaruje aerodinamička sila koja pokreće generator. Navedeni se sustav svojim aerodinamičkim obilježjima i izvedbom znatno razlikuje od većine ostalih LVE sustava. Primjerice, lebdjelica rotacijom ostvaruje znatnu silu uzgona i bez translatornog gibanja, promjenom brzine vrtnje valjka omogućuje se izravnija promjena aerodinamičkih koeficijenata, pogodna je za jednostavnije ostvarivo ravninsko gibanje (nasuprot prostornog), čime se ujedno bitno olakšava modularnu gradnju lebdeće jedinice (tj. upotrebu više lebdjelica na jednom užetu).
U radu je za HAWE koncept razvijen u okviru FP7 projekta provedeno matematičko modeliranje dinamike sustava, uključujući za njega specifične komponente, kao što su lebdeća jedinica, uže koje spaja lebdeću jedinicu s vitlom na tlu, te vitlo povezano s generatorom. Dobiveni model je zatim primijenjen u simulacijskoj analizi sustava te u optimizacijskoj studiji s ciljem istraživanja optimalnog upravljanja sa stanovišta maksimiziranja proizvodnje energije. Na temelju fizikalnih uvida dobivenih analizom optimizacijskih rezultata provedena je sinteza sustava regulacije za postizanje proizvodnje energije bliske optimalnoj. Konačno, razvijena strategija ispitana je putem računalnih simulacija. U skladu s navedenim, rad je podijeljen na poglavlja kako slijedi.
Poglavlje 1 – Uvod opisuje motivaciju za istraživanje LVE sustava općenito te HAWE sustava kao specifičnog sustava, daje pregled stanja područja, definira hipotezu disertacije s očekivanim znanstvenim doprinosima te pruža sažet prikaz strukture rada.
Poglavlje 2 – Model procesa i osnovna strategija upravljanja daje pregled matematičkog i simulacijskog modeliranja dinamike HAWE sustava. Izvedeni su modeli tri glavna podsustava koja uključuju (i) lebdeću jedinicu koja za ostvarivanje potrebnih aerodinamičkih sila koristi Magnusov efekt, (ii) uže koje u sustav unosi prostorno raspodijeljene i vremenski promjenjive učinke elastičnosti, inercije i aerodinamičkog otpora, te (iii) vitlo i generator, koji mogu biti povezani izravno ili korištenjem posebne transmisije. Uključeni su svi relevantni mehanički i aerodinamički efekti pri ravninskom gibanju, poput spomenute distribucije mase i
aerodinamičkog otpora duž užeta, pri čemu su aerodinamički koeficijenti preuzeti iz literature odnosno popratnih materijala dobivenih od partnera na projektu HAWE. Naglasak je na gibanju lebdeće jedinice u vertikalnoj ravnini u kojoj leži vektor brzine vjetra, što glavnim rezultatom ovog poglavlja čini model dinamike sustava pri ravninskom gibanju. U prilogu poglavlju je dodatno dan osvrt na mogućnost ostvarivanja prostornog gibanja korištenjem više valjaka ugrađenih u jednu lebdjelicu, što je bitno prvenstveno zbog mogućnosti stabilizacije sustava u slučaju bočnih udara vjetra te za izbjegavanje štetnog uvijanja užeta uslijed rotacije lebdjelice. Modeli različite kompleksnosti (s obzirom na stupanj pojednostavljenja podmodela užeta) implementirani su i ispitani u programskom okruženju MATLAB/Simulink. Poglavlje uključuje i prikaz postojeće, osnovne strategije upravljanja HAWE sustavom, koja koristi konstantne brzine užeta pri izvlačenju i uvlačenju, kao reference za poboljšanja ostvarena u ostatku rada.
Poglavlje 3 – Optimiranje upravljačke trajektorije opisuje provedbu optimizacijske studije i fizikalnu analizu dobivenih rezultata. Na temelju razvijenog 2D modela dinamike sustava i poznatih fizikalnih ograničenja, formuliran je optimizacijski problem te provedeno optimiranje upravljačkih varijabli (brzine vrtnje valjka lebdeće jedinice te sile ili brzine užeta koje se odmata s vitla) s ciljem maksimiziranja proizvodnje energije tijekom kontinuirano ponovljivog radnog ciklusa. U tu je svrhu korišten optimizacijski programski paket TOMLAB, koji za definiranje problema izravnog optimalnog upravljanja i njegovo pretvaranje u problem nelinearnog programiranja (NLP) koristi modul TOMLAB/PROPT, a za rješavanje dobivenog NLP problema algoritam SNOPT (engl. Sparse Nonlinear OPTimizer). Dobiveni rezultati optimiranja analizirani su kako bi se fizikalno protumačilo optimalno ponašanje sustava, s naglaskom na oblik optimalne trajektorije gibanja lebdeće jedinice, čime je dobivena fizikalna osnova potrebna za sintezu regulacijskog sustava. Analiza je s jedne strane temeljena na analitičkoj primjeni modela dinamike sustava, a s druge na numeričkim simulacijama u programskom paketu MATLAB/Simulink.
Poglavlje 4 – Upravljačka strategija opisuje sintezu regulacijskog sustava. Polazeći od temeljne nadređene strategije regulacije za postizanje osnovne funkcionalnosti sustava, formalno je definirana osnovna logika za koordinaciju podređenih regulatora brzine vrtnje motora lebdeće jedinice i generatora. Uz tako dobivenu osnovu, provedena je sinteza složenije strategije zasnovane na uvidima dobivenima u optimizacijskoj studiji (Poglavlje 3). S obzirom na potrebu za poštivanjem svih praktičnih radnih ograničenja, vezanih primjerice uz brzine i opterećenja unutar sustava, istražene su mogućnosti unapređenja osnovne koordinacijske
logike imajući u vidu različite dinamičke karakteristike (vremenske konstante) motora lebdeće jedinice i generatora.
Poglavlje 5 – Simulacijski scenariji ispitivanja upravljačke strategije i zaključci o izboru konačne upravljačke strategije daje analizu kvalitete i robusnosti predložene strategije regulacije. Simulacijski rezultati primjene razvijene praktične strategije regulacije uspoređeni su s rezultatima optimiranja, te s rezultatima temeljne strategije regulacije. Promatrani su iznos proizvedene energije i robusnost (ostvarivost) željenog načina upravljanja s obzirom na promjenu radnih parametara sustava, prvenstveno položaja lebdeće jedinice u odnosu na vitlo te duljine odmatanja užeta, koja može biti zadana kao ukupna ili kao radna (odmotana tijekom ciklusa, uz različit početni položaj lebdeće jedinice). Na temelju odgovarajuće komparativne analize, provedene pomoću programskog paketa MATLAB/Simulink, dane su konačne preporuke za implementaciju regulacijske strategije LVE sustava HAWE. Također, u prilogu poglavlju analizirana je mogućnost konfiguriranja polja (farmi) HAWE jedinica na ograničenoj površini s obzirom na minimalnu potrebnu udaljenost između generatorskih stanica na tlu i prevladavajući smjer vjetra.
Poglavlje 6 – Zaključak daje sažetak rezultata opisanih u radu kao i mogućih daljnjih istraživanja te opisuje glavne doprinose istraživanja, koji uključuju (i) postavljanje upravljanju namijenjenog dinamičkog modela HAWE sustava, uključujući razvoj podmodela užeta s prostorno raspodijeljenim i vremenski promjenjivim parametrima, (ii) optimiranjem potpomognut pronalazak optimalne strategije upravljanja HAWE sustavom, uz korištenje brzine vrtnje valjka lebdeće jedinice te brzine odmatanja užeta s vitla kao dviju raspoloživih upravljačkih varijabli i (iii) sintezu praktično primjenjivog regulacijskog sustava koji daje proizvodnju energije blisku optimalnoj. Dobiveni rezultati potvrđuju temeljnu hipotezu rada da se proizvodnja energije dobivena upravljanjem uz konstantnu brzinu izvlačenja užeta može značajno povećati naprednijom, a u primjeni i dalje provedivom strategijom upravljanja, uz istovremeno poboljšanje koordinacije rada generatora i motora koji pokreće valjak lebdjelice
Konceptualni model umjetnoga prihranjivanja krškoga vodonosnika otoka Visa : doktorski rad
No full textVis is a small, remote karst island in the Adriatic Sea with unique geological and hydrogeological features that have enabled the formation of karst aquifers from which highquality groundwater is abstracted, resulting in the island's autonomous water supply. Local groundwater resources are recharged solely by precipitation and are very vulnerable to climate change, seawater intrusion, and seasonal overexploitation. Currently, the water supply system satisfies the demand of the local population, but a fivefold increase in demand during the summer tourist season exerts high stress on freshwater resources, and several reductions for consumers have occurred in the last decades. The water supply system of Vis consists of five wells drilled in the Korita well field (~42 l/s) in the central part of the island, two wells (K1 and B1; ~5 l/s) in the Komiža hinterland, and the coastal spring Pizdica (~3 l/s). The need for alternative water management solutions yielded managed aquifer recharge (MAR) and early warning system for seawater intrusion (EWS) as potential options for increasing the safety and resilience of the island’s groundwater resources. Interdisciplinary field and laboratory investigations, combining geological, hydrogeological, hydrological, geophysical, structural-geological, and socio-economic methods, were utilized to develop robust conceptual models for MAR and EWS. Results indicated that the Central Vis aquifer, a heterogeneous, unconfined, and karstified carbonate aquifer dominated by flow through densely fractured rock mass, could be artificially recharged from the surface by the infiltration pond method. As a source water for MAR, storm and flood water runoff from the surrounding hills could be collected, retained, and infiltrated from the existing channel structure in the Korita valley. The proposed MAR solution is economically justifiable but risky due to the inherent properties of karst systems and the lack of representable case studies highlighting best practices. Moreover, increased hydraulic conductivity along the main fault zone (i.e., Komiža-Vis fault) highlights the eastern direction as the most probable and dangerous with respect to seawater intrusion to the Central Vis aquifer. Hence, an ideal location and design for an EWS was hypothesized. A combination of MAR and an EWS could provide a basis for sustainable management of the island's karst aquifer, preventing and mitigating the potential deterioration of groundwater quantitative and chemical status, particularly in light of the rapidly changing climate and rising anthropogenic pressures in the Mediterranean region.Otok Vis, mali pučinski krški otok u središnjem dijelu Jadranskog mora, ima jedinstvene geološke i hidrogeološke značajke, što je omogućilo nastanak krških otočkih vodonosnika. Zahvaljujući tome, otok je samodostatan po pitanju vodoopskrbe koja se osigurava iz pet bušenih zdenaca u centralnom dijelu otoka (vodocrpilište Korita; ~42 l/s) te u manjoj mjeri iz dva bušena zdenca (K1 i B1; ~5 l/s) i priobalnog izvora Pizdice (~3 l/s) u blizini Komiže. Glavne litološke jedinice na otoku Visu su (i) vulkanogeno-sedimentno-evaporitni kompleks Komiškog zaljeva (tzv. Komiški dijapir) trijaske starosti, sačinjen od gipsa, dolomitno-gipsnih breča, krškog detritusa te raznih vulkanskih i klastičnih stijena, (ii) razlomljeni i okršeni vapnenci i dolomiti kredne starosti te (iii) kvartarne naslage, sačinjene od crvenice, padinskih naslaga, te eolskog pijeska. Reljef otoka Visa karakteriziraju tri morfološki uzdignuta grebena i dvije doline u kojima su razvijena krška polja. Najviši vrh je Hum (576 m n.v.), smješten u zapadnom dijelu otoka. Geološke strukture i reljef su orijentirani približno u smjeru zapad-istok (tzv. hvarsko pružanje struktura). Najznačajniji i najproduktivniji vodonosnik (tzv. centralni viški vodonosnik) je u krednim vapnencima srednje do visoke propusnosti te je idealno smješten u središnjem dijelu otoka (vodocrpilište Korita), gdje je zaštićen od značajnijeg prodora mora nepropusnim stijenama komiškog dijapira sa zapadne strane te niskopropusnim karbonatima ispunjenim sekundarnim materijalom (pjeskovitim produktom trošenja dolomita i glinenim česticama iz kvartarnih crvenica) s južne strane. Donja granica vodonosnika izgrađena je od dolomita i/ili dolomitičnog vapnenca te je praktički nepropusna. Podzemna voda nalazi se na otprilike 120 m dubine a generalni smjer tečenja je prema istoku. Sjeverni, istočni i južni obalni pojasi otoka su uglavnom hidrogeološki beznačajni, budući da dolazi do potpunog prodora mora i zaslanjenja kroz visokopropusne vapnence. Iako trenutačni kapacitet crpljenja u vodocrpilištu Korita i zdencima na zapadnoj strani otoka zadovoljava većinu potražnje, intenzivan ljetni turizam i klimatske promjene vrše značajan pritisak na resurse podzemne vode tijekom sušne sezone. Posljedično, tijekom proteklog desetljeća došlo je do povremenih redukcija za potrošače. U ovom radu istražene su mogućnosti primjene i uspostave sustava umjetnog prihranjivanja vodonosnika (eng. managed aquifer recharge – MAR) kako bi se povećala količina podzemne vode u centralnom viškom vodonosniku te sustava ranog uzbunjivanja (eng. early warning system - EWS) za prodor morske vode kako bi se spriječilo potencijalno pogoršanje kemijskog stanja podzemne vode. Umjetno prihranjivanje vodonosnika je naziv za skup metoda kojima se višak površinske vode (npr. poplavna i bujična voda, pročišćena otpadna voda, desalinizirana voda) prikuplja te prihranjuje u vodonosnik putem upojnih zdenaca ili infiltracijskih zona. Iako se različite metode MAR-a primjenjuju u vodonosnicima s međuzrnskom poroznošću diljem svijeta, njihova primjena u kompleksnim krškim vodonosnicima, koje karakterizira hidraulička anizotropija i heterogenost, predstavlja značajan izazov. Budući da u svijetu postoji svega nekoliko primjera MAR-a u karbonatnim stijenama, ne postoje opsežne studije koje predlažu prikladne metode istraživanja i izvedbe takvih sustava. Kako bi se istražile mogućnosti primjene MAR-a i EWS-a te uspostavili konceptualni modeli njihove izvedbe, provedena su opsežna interdisciplinarna terenska i laboratorijska istraživanja. Na temelju reambulacije geoloških i hidrogeoloških karata i podataka, analize hidrauličkih parametara te trasiranja, izrađen je novi konceptualni hidrogeološki model otoka. Definirana su dva glavna slijeva na otoku: slijev vodocrpilišta Korita te slijev izvora Pizdice. Nadalje, određeni su glavni smjerovi tečenja i prividne brzine toka podzemne vode od 150-200 m/dan unutar centralnog viškog vodonosnika. Na temelju novih saznanja izrađena je hidrogeološka karta te hidrogeološki profil otoka Visa. Od 2019. uspostavljen je kontinuirani i periodički (mjesečni) monitoring hidrokemijskih parametara (ionski sastav, pH, elektrolitička vodljivost). Na vodocrpilištu Korita kakvoća podzemne vode je izvrsna i pripada Ca-HCO3 hidrokemijskom facijesu u svim hidrološkim uvjetima. Glavni procesi koji utječu na kemijski sastav podzemne vode unutar centralnog viškog vodonosnika su otapanje karbonatnih stijena, miješanje s morskom vodom i ionska izmjena. Analize aktivnosti tricija u uvjetima hidrološkog minimuma i maksimuma pokazale su da je podzemna voda mješavina sub-moderne i moderne vode, s vremenom zadržavanja od 15 do 40 godina. Stabilni fizikalno-kemijski parametri, unatoč ispodprosječnim oborinama tijekom promatranog perioda, ukazali su na to da centralni viški vodonosnik ima visoku sposobnost zadržavanja te polaganog otpuštanja, uz značajne rezerve podzemne vode koje su relativno otporne na duže sušne periode i intenzivni režim crpljenja tijekom ljeta. Geofizičkim i strukturno-geološkim istraživanjima utvrđene su debljine kvartarnog pokrivača, gornje i donje zone trošenja vapnenca (tj. epikrške zone) i kompaktnih vapnenačkih vodonosnika te su određeni glavni diskontinuiteti (slojevi, pukotine, rasjedi) i krški elementi (kaverne, kanali) koji utječu na infiltraciju oborine i tok podzemne vode. Na temelju meteoroloških podataka s postaje u Komiži izrađena je hidrološka analiza slijeva vodocrpilišta Korita. Iako se prosječna godišnja količina oborine ne može smatrati malom (951 mm), zbog relativno visoke temperature zraka i gustog biljnog pokrova evapotranspiracija iznosi gotovo 66%, što rezultira efektivnom oborinom i prihranjivanjem vodonosnika od 326 mm godišnje. Također, primijenjene su simulacije budućih klimatskih uvjeta dobivene iz regionalnih klimatskih modela Aladin, Promes i RegCM, uz statističke korekcije i uklanjanje sustavnih pogrešaka za otok Vis. Rezultati sva tri modela ukazuju na statistički značajan porast srednje godišnje temperature zraka od 3 do 4 °C do kraja stoljeća, dok oborina ne pokazuje statistički značajan trend. Opažene promjene u temperaturnom i evapotranspiracijskom režimu mogu dovesti do značajnog gubitka vodnih resursa na otoku Visu uz smanjenje protoka na slijevu od 20-40%. Uz nepovoljne klimatske scenarije, značajan problem predstavlja i kontinuirani rast turizma te se predviđa da će potražnja vode porasti za 20% u skorijoj budućnosti. Na temelju povoljnih geoloških, hidroloških, i hidrogeoloških čimbenika, kao i definiranih potreba za osiguravanjem dodatnih količina podzemne vode, uspostavljen je konceptualni model MAR-a. Kao najprikladnije rješenje odabrana je metoda infiltracijskog jezera, koja bi se uspostavila unutar vodocrpilišta Korita, u uskoj dolini gdje su prisutni stari i zapušteni kanali koji prikupljaju bujične i poplavne vode s okolnih brda te ih evakuiraju u smjeru mora. Kako bi se osigurao prostor za prikupljanje vode, nužno je sagraditi pregradnu branu na završetku kanala te je nužno ukloniti gusto raslinje i nepropusno tlo. Prikupljena voda bi se potom pasivno i difuzno infiltrirala kroz propusno tlo i epikršku zonu do saturirane zone. Prilikom infiltracije nužno je izbjeći preferentne puteve tečenja poput krških kanala i jama, kako bi se izbjeglo naglo i diretno prihranjivanje u saturiranu zonu, što bi moglo dovesti do onečišćenja vodonosnika i neželjenih kemijskih reakcije (npr. otapanje karbonatnog vodonosnika uslijed miješanja voda različitih sastava). Glavni rizici i nesigurnosti primjene MAR-a povezani su s hidrološkim čimbenicima (tj. dostatnost vode za umjetno prihranjivanje), heterogenošću vodonosnika (tj. prisutnost krških kanala koji bi brzo ispustili infiltriranu vodu iz vodonosnika), učinkovitost infiltracijskog jezera i neželjene kemijske reakcije (tj. otapanje vodonosnika i onečišćenje). Kako bi se spriječilo pogoršanje kakvoće i kemijskog statusa centralnog viškog vodonosnika i podzemne vode uslijed smanjenog prihranjivanja uzrokovanog klimatskim promjenama i povećanom potražnjom, nužno je uspostaviti sustav ranog uzbunjivanja za prodor mora. Iako je centralni viški vodonosnik zaštićen od prodora mora sa zapadne i južne strane te nepropusnom dolomitnom podinom, trasiranjem je utvrđena hidraulička anizotropija u smjeru glavnog rasjeda na otoku (rasjedna zona Komiža-Vis), duž kojeg je pretpostavljen glavni smjer prodora mora (I-Z). Stoga, sustav ranog uzbunjivanja bi se trebao uspostaviti nizvodno od vodocrpilišta Korita, unutar krškog polja Dol. Sustav može biti sačinjen od jednog ili više bušenih zdenaca, opremljenih automatskim mjeračima elektrolitičke vodljivosti i hidrostatskog tlaka s telemetrijskim odašiljačem. Uspostavom ovakvog sustava značajno bi se unaprijedilo poznavanje uvjeta u zoni miješanja slane i slatke vode te bi se znatno smanjio rizik od zaslanjivanja vodonosnika u slučaju povećanja režima crpljenja na vodocrpilištu Korita. Kombinacija umjetnog prihranjivanja vodonosnika i sustava ranog uzbunjivanja na prodor mora mogla bi pružiti osnovu za održivo upravljanje krškim vodonosnikom otoka Visa, sprječavajući i ublažavajući potencijalno pogoršanje količinskog i kemijskog stanja podzemnih voda, posebno u svjetlu klimatskih promjena koje se brzo mijenjaju i rastućih antropskih pritisaka u mediteranskoj regiji