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Optimal allocation and sizing of distributed generations and capacitor banks at multiple voltage levels of a distribution network : doctoral thesis
No full textOvaj doktorski rad istražuje optimalan razmještaj distribuiranih izvora i kondenzatorskih baterija na više naponskih razina distribucijske mreže s ciljem poboljšanja tehničkih i ekonomskih karakteristika sustava. Ključna svrha je dodatno smanjenje gubitaka radne snage i poboljšanje naponskog profila uz kontrolu investicijskih troškova. Zbog kompleksnosti sustava s transformatorima i različitim naponskim razinama razvijena je nova metoda optimizacije koja uzima u obzir gubitke na transformatorima i utjecaj na napone na različitim naponskim razinama. Simulacije su pokazale da ovaj pristup može značajno unaprijediti učinkovitost razmještaja distribuiranih izvora i kondenzatorskih baterija u odnosu na tradicionalne metode koje
uzimaju u obzir samo impedancije, gubitke i nadomjesne modele mreže jedne naponske razine. Također, pokazano je da pristup s uključivanjem modela transformatora i razmatranjem utjecaja distribuiranih izvora i kompenzacijskih prigušnica može poboljšati performanse kod distribucijskih sustava s problemima porasta napona. Ovaj pristup može se koristiti i za razmještaj prigušnica uz
distribuirane izvore, a ne samo kod kondenzatorskih baterija. Naglašena je važnost preciznog modeliranja svih elemenata distribucijske mreže. Rezultati istraživanja nude smjernice te ukazuju na potencijal daljnjeg razvoja i primjene u elektroenergetskim sustavima. Rad pridonosi razvojem nove metode optimizacije razmještaja distribuiranih izvora i kondenzatorskih baterija u distribucijskim mrežama s više naponskih razina. Ključni doprinosi uključuju modifikaciju genetskog algoritma za bolji razmještaj izvora i baterija, integraciju modela transformatora te ekonomsku evaluaciju. Ovaj rad pruža temelj za buduća istraživanja i inovacije u optimizaciji distribucijskih mreža.This doctoral dissertation explores the optimal placement of distributed generation and capacitor banks across multiple voltage levels of the distribution network, aiming to enhance the technical and economic characteristics of the system. The objective is to reduce real power losses and improve the voltage profile while controlling investment costs. Due to the complexity of systems involving transformers and various voltage levels, a new optimization method has been developed that accounts for transformer losses and voltage impacts across different levels. Simulations show that this approach significantly improves the efficiency of distributed generation and capacitor bank placement compared to traditional methods, which consider only impedance, losses, and equivalent models for a single voltage level. Additionally, it has been shown that including transformer models and considering the impact of distributed generations and shunt reactors enhances performance in systems with voltage rise issues. This approach applies to the placement of shunt reactors alongside distributed generations, not just capacitor banks. Precise modeling of all network elements is emphasized. The research results offer guidelines and suggest potential for further development in power systems. This dissertation contributes by developing a new optimization method for placing distributed generations and capacitor banks in multi-voltage-level networks. Key contributions include the modification of genetic algorithms, integration of transformer models, and economic evaluation. This research provides a foundation for future studies and innovations in network optimization
On-Line Survey About Autonomic Dysreflexia in Individuals with Spinal Cord Injury in Croatia
No full textBackground/Objectives: Autonomic dysreflexia (AD) is a clinical syndrome affecting persons with spinal cord injury (SCI). The aim of the study was to present the experience of individuals with SCI and AD in Croatia. Single-center questionnaire study. Setting: Faculty of Medicine, University of Rijeka, Rijeka, Croatia. Persons with SCI were divided into those with an SCI at T6 and above (n = 41) and those with an SCI at T7 and below (n = 29). Based on anamnestic data, patients with an SCI at T6 and above were further divided into those with and without self-reported clinical symptoms of AD (respectively: n = 33 and n = 8). Methods: The online survey included 23 questions of various types. It consisted of a general (demographic) section, section with specific questions about AD, and a section on self-assessment and quality of life. Based on the answers, the experience and knowledge of AD among individuals with an SCI in Croatia was assessed. Results: A total of 70 individuals with an SCI completed the whole survey. The average age was 40.6 years. The patients were predominantly male (72.9%) and mostly with a traumatic SCI (84.3%). Of the 70 individuals with an SCI, 35 (50%) reported they were familiar with AD, with the majority indicating that the internet was their primary source of information. Among those with an SCI who were unaware of AD, most (34/35 = 97.1%) wanted to learn about AD. The self-assessed quality of life was insignificantly better in patients with an SCI below T6 than in those with higher lesions. Patients with AD reported different symptoms and the most frequently reported symptom was a headache (70%). In 64% of participants, the primary trigger of AD were issues with the urinary bladder. In most individuals (55%), symptoms were not recognized by the healthcare providers. The individuals with AD were dissatisfied with the information about AD they received from doctors or nurses. Overall, 61% of all participants with AD rated their quality of life as good. Conclusions: Persons with an SCI are not adequately informed about AD. In most persons with AD, their symptoms are not properly recognized by healthcare providers. Our results suggest the need for more education of healthcare professionals about AD
European Guideline on Chronic Nausea and Vomiting—A UEG and ESNM Consensus for Clinical Management
No full textIntroduction: Chronic nausea and vomiting are symptoms of a wide range of gastrointestinal and non-gastrointestinal conditions. Diagnosis can be challenging and requires a systematic and well-structured approach. If the initial investigation for structural, toxic and metabolic disorders is negative, digestive motility and gut-brain interaction disorders should be assessed. United European Gastroenterology (UEG) and the European Society for Neurogastroenterology and Motility (ESNM) identified the need for an updated, evidence-based clinical guideline for the management of chronic nausea and vomiting. Methods: A multidisciplinary team of experts in the field, including European specialists and national societies, participated in the development of the guideline. Relevant questions were addressed through a literature review and statements were developed and voted on according to a Delphi process. Results: Ninety-eight statements were identified and voted following the Delphi process. Overall agreement was high, although the grade of scientific evidence was low in many areas. Disagreement was more evident for some pharmacological treatment options. A diagnostic algorithm was developed, focussing on the differentiating features between gastrointestinal motility and gut-brain interaction disorders with predominant nausea and vomiting. Conclusion: These guidelines provide an evidence-based framework for the evaluation and treatment of patients with chronic nausea and vomitin
The Relationship Between the Modulation of Intestinal Microbiota and the Response to Immunotherapy in Patients with Cancer
No full textThe intestinal microbiota is an important part of the human body, and its composition can affect the effectiveness of immunotherapy. In the last few years, the modulation of intestinal microbiota in order to improve the effectiveness of immunotherapy has become a current topic in the scientific community, but there is a lack of research in this area. In this review, the goal was to analyze the current relevant literature related to the modulation of intestinal microbiota and the effectiveness of immunotherapy in the treatment of cancer. The effects of antibiotics, probiotics, diet, and fecal microbial transplantation were analyzed separately. It was concluded that the use of antibiotics, especially broad-spectrum types or larger quantities, causes dysbiosis of the intestinal microbiota, which can reduce the effectiveness of immunotherapy. While dysbiosis could be repaired by probiotics and thus improve the effectiveness of immunotherapy, the use of commercial probiotics without evidence of intestinal dysbiosis has not yet been sufficiently tested to confirm its safety for cancer for immunotherapy-treated cancer patients. A diet consisting of sufficient amounts of fiber, as well as a diet with higher salt content positively correlates with the success of immunotherapy. Fecal transplantation is a safe and realistic adjuvant option for the treatment of cancer patients with immunotherapy, but more clinical trials are necessary. Modulating the microbiota composition indeed changes the effectiveness of immunotherapy, but in the future, more human studies should be organized to precisely determine the types and procedures of microbiota modulation
Reference Intervals for Common Biochemistry and Hematology Parameters in Early Pregnancy—A Prospective Study
No full textBackground: The aim of this study was the determination of reference values for the common laboratory parameters in early pregnancy using a direct method and to assess their clinically significant difference, which was compared to the reference intervals for non-pregnant women with respect to the reference change value (RCV). Methods: This study was conducted from September 2022 to December 2023 at the Clinical Department of Laboratory Diagnostics, Clinical Hospital Centre RIJEKA, Croatia. The inclusion criteria were as follows: age ≥ 18 years, singleton pregnancy, normal ultrasound examination, and prenatal screening. The exclusion criteria were as follows: recent illness, pregnancy-related complications, medically assisted reproduction, and medication use. The reference intervals were established using the non-parametric percentile method according to the CLSI EP28-A3c recommendation. The reference values were compared to those of non-pregnant women and judged against RCV values based on biological variation. Additionally, we tested the influence of food consumption and oral supplements. Results: The data of 299 participants were included in the study. Laboratory tests whose changes are clinically relevant lower in early pregnancy are as follows: hemoglobin, MCV, hematocrit, MCH, urea, creatinine, albumin, alkaline phosphatase, lactate dehydrogenase, sodium, and magnesium. The clinically relevant higher values are as follows: RDW, total leukocyte count, neutrophil granulocytes, monocytes, CRP, total cholesterol, triglycerides, and amylase. UIBC has a wider reference range. The consumption of food and supplements has no clinically significant influence in relation to the RCV. Conclusions: Establishing reference intervals in pregnancy remains a challenge due to the metabolic changes during pregnancy, as well as its clinical significance
The Role of Instagram Usage and Loneliness in the Relationship Between Digital Stress and Well-Being Among Young People
No full textCilj ovog istraživanja bio je ispitati efekte intenziteta korištenja Instagrama i usamljenosti na odnos digitalnog stresa i psihološke dobrobiti kod mladih osoba. Istraživanje je provedeno na 247 studenata, od kojih je 85.8 % ženskog, a 13.8 % muškog spola. Ispitanici pripadaju dobnoj skupini od 18 do 28 godina (M = 22.07, SD = 2.14). Za potrebe istraživanja korištene su sljedeće mjere: Multidimenzionalna skala digitalnog stresa, Skala usamljenosti, Skala intenziteta korištenja Instagrama i Indeks dobrobiti Svjetske zdravstvene organizacije, te su prikupljeni demografski podaci. Rezultati hijerarhijske regresijske analize pokazali su statistički značajan negativan doprinos usamljenosti i spola, te statistički značajan pozitivan doprinos intenziteta korištenja Instagrama u objašnjenju psihološke dobrobiti. Dobivena je statistički značajna interakcija između intenziteta korištenja Instagrama i preopterećenosti informacijama na psihološku dobrobit, dok moderatorski učinci nisu potvrđeni za ostale dimenzije digitalnog stresa. Konkretno, kod mladih osoba koje iskazuju nizak stres zbog preopterećenosti informacijama, visok intenzitet korištenja Instagrama povezan je s povećanjem psihološke dobrobiti, što nije slučaj kod mladih koji iskazuju visoku razinu preopterećenosti informacijama. Suprotno očekivanjima, usamljenost nije pokazala moderatorsku ulogu u odnosu između digitalnog stresa i psihološke dobrobiti. Doprinos ovog istraživanja je u razumijevanju kompleksnog odnosa između digitalnog stresa i psihološke dobrobiti, te pružanje temelja za razvoj intervencija usmjerenih na specifične potrebe mladih korisnika društvenih mreža.The aim of this study was to examine the effects of Instagram usage intensity and loneliness on the relationship between digital stress and psychological well-being among young people. The research was conducted on 247 students, with 85.8% identifying as female and 13.8% as male. The participants belonged to the age group of 18 to 28 years (M = 22.07, SD = 2.14). The following measures were used for the study: the Multidimensional Digital Stress Scale, the Three-Item Loneliness Scale, the Instagram Intensity Scale, and the WHO-5 Well-being Index, along with demographic data collection. Results of hierarchical regression analysis showed a statistically significant negative contribution of loneliness and gender, as well as a statistically significant positive contribution of Instagram usage intensity in explaining psychological wellbeing. A statistically significant interaction emerged between Instagram usage intensity and connection overload in relation to psychological well-being, while moderating effects were not confirmed for other dimensions of digital stress. Specifically, among young people experiencing low stress due to connection overload, high Instagram usage intensity was associated with increased psychological well-being. However, this was not the case for those experiencing high levels of connection overload. Contrary to the expectations, loneliness did not show a moderating role in the relationship between digital stress and psychological well-being. This study contributes to a better understanding of the complex relationship between digital stress and psychological well-being, layingthe foundation for developing interventions tailored to the specific needs of young social media users
Maintenance and inspections of LNG system on modern container ships
No full textStroži ekološki propisi i napredak tehnologije doveli su do razvoja i upotrebe alternativnih pogonskih goriva u pomorstvu. Ukapljeni prirodni plin postao je glavni izbor kod naručivanja novih brodova na pogon alternativnim gorivima. U ovom diplomskom radu prikazane su komponente i karakteristike sustava goriva ukapljenog prirodnog plina kod modernih kontejnerskih brodova. Opisano je redovno održavanje i pregledi komponenti sustava, te inspekcijski pregledi takvih brodova. Dan je osvrt na dodatne rizike na brodu i pripremu posade.Strict environmental regulations and the advance of technology led to the evolution and use of alternative marine fuels. Liquified natural gas has become a main choice when ordering a new-building vessel powered by an alternative fuel. This master thesis describes the components and main properties of liquified natural gas fuel system. Regular maintenance and inspections of the fuel system, and inspections of such vessels are described. Review of additional risks on board and crew preparation has been given
Modeli isplativosti proizvodnje vodika i njegove integracije u plinsku mrežu
No full textIn the energy transition, hydrogen is considered one of the key elements that could
enable the realization of a carbon-neutral economy by 2050. The research within this
doctoral thesis includes an analysis of the profitability of building an electrolyzer for
the production of yellow and green hydrogen, making maximum use of the existing
infrastructure. The goal is to formulate models that will analyze the potential location
of an unpromising thermal power plant, the location of a wind power plant located
near the gas transportation network, and the location of a large hydrogen consumer.
The production price and quantity of hydrogen as output variables of the models will
test the hypothesis about the impact of hydrogen in the energy transition in terms of
reduced CO2 emissions and utilization of the existing gas infrastructure.
Two economic models investigate the possibility of integrating hydrogen into the gas
network, i.e. the first model analyzes the justification of investing in an electrolyzer
at the location of the thermal power plant, and the second model analyzes the impact
of hydrogen production on the total income of the wind power plant. An alternative
to the integration of hydrogen into the gas network is a third economic model that
calculates the justification of hydrogen production at the point of consumption, i.e. a
model where electricity is transmitted to the point of hydrogen consumption, instead
of transporting hydrogen through the gas system.
Economic models represent a tool that enables the comparison of the production
price of hydrogen with the prices of fossil alternatives. If the production price of
hydrogen is uncompetitive, the share of necessary subsidies is calculated in terms
of the justification of the investment and the achievement of decarbonization goals.
The research results will provide new scientific insights and help in making
investment and regulatory decisions on investing in hydrogen production by water
electrolysis for greater utilization and efficiency of the existing energy infrastructure,
while respecting the goals of climate neutrality.U energetskoj tranziciji vodik se smatra jednim od ključnih elemenata koji bi mogao
omogućiti ostvarenje ugljično-neutralnog gospodarstva do 2050. godine. Istraživanje
u okviru ovog doktorskog rada obuhvaća analizu isplativosti izgradnje elektrolizatora
za proizvodnju žutog i zelenog vodika maksimalno iskorištavajući postojeću
infrastrukturu. Cilj je formulirati modele koji će analizirati potencijalnu lokaciju
neperspektivne termoelektrane, zatim lokaciju vjetroelektrane koja se nalazi u blizini
plinske transportne mreže te lokaciju velikog potrošača vodika. Proizvodna cijena i
količina vodika kao izlazne varijable modela testirat će hipotezu o utjecaju vodika u
energetskoj tranziciji glede smanjena emisija CO2 i iskorištvanja postojeće plinske
infrastrukture.
Dva ekonomska modela istražuju mogućnost integracije vodika u plinsku mrežu,
odnosno prvi model analizira opravdanost ulaganja u elektrolizator na lokaciji
termoelektrane, a drugi model analizira utjecaj proizvodnje vodika na ukupni prihod
vjetroelektrane. Alternativa integraciji vodika u plinsku mrežu je treći ekonomski
model koji izračunava opravdanost proizvodnje vodika na mjestu potrošnje, odnosno
model gdje se električna energija prenosi do mjesta potrošnje vodika, umjesto
transporta vodika plinskim sustavom.
Ekonomski modeli predstavljaju alat koji omogućuje usporedbu proizvodne cijene
vodika sa cijenama fosilnih alternativa. Ukoliko je proizvodna cijena vodika
nekonkurentna, izračunava se udio potrebnih subvencija u pogledu opravdanosti
ulaganja i ostvarenja dekarbonizacijskih ciljeva.
Rezultati istraživanja pružiti će nove znanstvene uvide te pomoći pri donošenju
investicijskih i regulatornih odluka o ulaganju u proizvodnju vodika elektrolizom vode
za veću iskoristivost i učinkovitost postojeće energetske infrastrukture, uvažavajući
pritom ciljeve klimatske neutralnosti
Planning navigation in coastal areas, approchnig waterway and port areas
No full textPlaniranje plovidbe u ovom završnom radu prezentirano je tako da se razmatraju svi elementi bitni za plovidbu i planiranje putovanja bez obzira na to u kojem dijelu svijeta se plovidbeni put planira, uzimajući u obzir sposobnosti i obučenost posade te manevarske sposobnosti broda. Bitni su i čimbenici koji utječu na planiranje plovidbe te odluke koje se u planiranju plovidbe donose dok je plan u izradi ali i u toku plovidbe. Greške koje se događaju u plovidbi i planiranju plovidbe mogu dovesti u opasnost brod i posadu s toga je bitna obuka posade u planiranju i provođenju plana te prilagodba tehnologijama koji se na brodu nalaze.Planning navigations in this final paper is presented that all aspects important for navigation and planning navigation witout conserning on part of world that is made for, considering abilities and training of crew and manouvering abilities of ship. Importans of factors which affects on planning navigation and decidions that are made during navigation planning and also during voyage while navigation plan is performing. Errors that can be made in performing navigation and making navigation plans can lead to endanger ship and crew on board so it is important to train crew in making navigation plans and performing plans in navigation and ajuting technologies that are on bord ship
Seasonality in Camping Tourism : Guest Motivation and Preferences of Campsite Attributes in Low Season
No full textThis research provides insight in the seasonality of the camping industry, the customer motivation to travel and preferences of campsite attributes of campers staying in the Costa Brava campsites in Catalunya, Spain, during the low season. While previous research has predominantly focused on high season camping behaviour, this study addresses the gap in understanding guest motivations and preferences in campsite attributes outside the peak months.
Using a quantitative approach supported by exploratory interviews, data was collected from 121 international camping guests across three coastal campsites. The research applies the Relevance-Determinance Analysis framework (Mikulić et al., 2017) to identify which campsite attributes are are not only important to guests, but also influence their overall satisfaction with the destination.
Key findings reveal that low season campers are typically retired international travelers, often staying for extended periods with their own camping equipment and, in many cases, pets. Their primary motivations include good weather, peacefulness, lower prices, and fewer crowds. The most valued campsite attributes are sanitary facilities, cleanliness, safety, and staff friendliness—core services that significantly impact satisfaction. Interestingly, wellness areas and entertainment facilities, often highlighted in season extension strategies, were rated as less relevant by this segment.
The study also identifies notable differences in attribute preferences based on accommodation type and pet ownership, providing campsite managers with practical insights for service improvement. Overall, the research contributes to the academic understanding of seasonal variability in tourism preferences and offers actionable recommendations for campsite managers and destination managers aiming to reduce seasonality and increase guest satisfaction in the low season