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Analysis of social network users in order to detect spam usage
No full textInterneto robotai socialiniuose tinkluose yra vis didėjanti problema. Baigiamajame magistro darbe taikomi duomenų gavybos metodai siekiant identifikuoti socialinio tinklalapio robotus. Šio darbo pagrindinis tikslas yra identifikuoti esamus interneto robotus ir pasiūlyti būdą prevencijai taikyti. Išanalizuoti praktikoje taikomų duomenų gavybos metodų, skirtų interneto robotų identifikavimui, veikimo principai, jų privalumai ir trūkumai. Tyrimui atlikti naudojami tinklalapio įvykių žurnalo ir duomenų bazės duomenys. Naudojant naršymo duomenų analizės metodą ir klasterizavimą buvo nustatyti vartotojų ir interneto robotų veiklos skirtumai, pateiktos baigiamojo darbo išvados ir siūlymai. Darbą sudaro 6 dalys: įvadas, interneto socialinių tinklų ir juose aptinkamų interneto robotų literatūros analizė, duomenų gavybos metodų ir programinės įrangos parinkimas, robotų elgesio veiksmų nustatymas, išvados ir siūlymai, literatūros sąrašas.Web robots identification in social networks is an increasing problem. In this master thesis data mining techniques are used to identify web robots in analyzed social network. The main objective of this work is to identify existing web bots and offer a way to prevent them in the future. The practice of applying data mining methods for the identification of online robots, operating principles, their advantages and disadvantages was analyzed in this master thesis. Website log and database data was used to perform the study. Web navigation methods and clustering was used to identify social network web robots. Conclusions and recommendations are provided. Structure: introduction, analysis of the literature, selection of data mining methods and program package, identification of internet robots, conclusions and suggestions, references
Numerical simulation of thermal conductivity and thermal stress in lightweight refractory concrete with cenospheres
No full textThe main objective of this paper was to investigate the heat transfer of modified lightweight refractory concrete at the microscopic scale. In this work, such material was treated as a porous composite based on the compound of calcium aluminate cement and aluminosilicate cenospheres. The presence of air inclusions within the cenospheres was an essential factor in the reduction in thermal performance. Due to the intricacy of the subject investigated, our research employed numerical, theoretical, and experimental approaches. Scanning electron microscopy (SEM) imaging was performed to study the composite microstructure with a special focus on geometry, dimensions, and the distribution of cenospheres. Based on the experimental analysis, simplified geometrical models were generated to reproduce the main features of the composite matrix and cenospheres. A finite element framework was used to determine the effective thermal conductivity of such domains as well as the thermal stresses generated in the sample during the heat flow. A considerable difference in thermal properties was revealed by comparing the simulation results of the pure composite matrix and the samples, indicating a varying arrangement of cenosphere particles. The numerical results were complemented by a theoretical study that applied analytical models derived from the two-phase mixture theory—parallel and Landauer. A satisfactory agreement between numerical and theoretical results was achieved; however, the extension of both presented approaches is required.iss. 1vol. 1
Research of the Combustion Process in a Compression Ignition Engine Fuelled with Liquid and Gaseous Biofuels
No full textDisertacijoje nagrinėjamas dviejų rūšių biodegalų (skystųjų ir dujinių) naudojimo slėginio uždegimo vidaus degimo variklyje efektyvumas, lyginant su iškastiniais degalais, dujas tiekiant kartu su įsiurbiamu oru ir jas uždegant, į cilindrą tiesiogiai įpurškus skystuosius degalus. Pagrindinis tyrimų objektas – dviejų rūšių biodegalų (biodujų ir antros kartos biodyzelino) degimo procesas tiesioginio įpurškimo slėginio uždegimo variklyje, biodujas tiekiant į įsiurbimo kolektorių. Disertacijos tikslas – eksperimentiškai ir teoriškai ištyrus skirtingais dviejų rūšių biodegalais veikiantį slėginio uždegimo variklį, nustatyti dujinių degalų energinės dalies, įpurškimo pradžios momento ir deginių recirkuliacijos (DR) poveikį degimo procesui bei energiniams ir ekologiniams rodikliams. Darbe sprendžiami keli pagrindiniai uždaviniai: eksperimentiškai ištirti degiajame mišinyje esančios dujinių degalų energinės dalies įtaką slėginio uždegimo (SU) variklio energiniams ir ekologiniams rodikliams. Remiantis SU variklio rodiklių pokyčio teorine analize ištirti skirtingos dujinių degalų energinės dalies įtaką degimo procesui esant įvairioms variklio apkrovoms. Remiantis teorinių ir eksperimentinių tyrimų rezultatais pasiūlyti rekomendacijas dviejų rūšių biodegalų sudėčiai, skystųjų degalų įpurškimo pradžios momentui ir DR naudojimo efektyvumui nustatyti. Disertaciją sudaro įvadas, trys skyriai, bendrosios išvados, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai. Įvadiniame skyriuje aptariama tiriamoji problema, darbo aktualumas, aprašomas tyrimų objektas, formuluojamas darbo tikslas bei uždaviniai, pateikiama tyrimų metodika, darbo mokslinis naujumas, darbo rezultatų praktinė reikšmė, ginamieji teiginiai. Įvado pabaigoje pristatomos disertacijos tema autoriaus paskelbtos publikacijos ir pranešimai konferencijose bei disertacijos struktūra. Pirmajame skyriuje apžvelgti moksliniai straipsniai disertacijos tema ir dviejų rūšių degalų naudojimą skatinantys veiksniai. Formuluojamos skyriaus išvados ir tikslinami disertacijos uždaviniai. Antrajame skyriuje pateikiama dviejų rūšių degalų naudojimo SU variklyje tyrimo metodika, naudota įranga bei ekologinių ir energinių rodiklių skaičiavimo metodika. Trečiajame skyriuje pateikti dviejų rūšių degalų naudojimo slėginio uždegimo variklyje eksperimentinių tyrimų ir skaitinio modeliavimo rezultatai.The dissertation deals with the combustion efficiency of dual-biofuels (liquid and gaseous) in a compression ignition internal combustion engine, supplying the gas together with the intake air. The main object of research is the combustion process of dual-fuel, i.e., biogas and second-generation biodiesel, in a direct injection compression ignition engine. The goal of the dissertation is to determine the influence of these fuels on performance and emission indicators after experimental and theoretical research of dual-fuels, i.e., biodiesel and biogas, and to make suggestions on the efficiency of these fuels. The dissertation solves several main tasks: the dual-fuel influence on performance and emission parameters is researched using conventional diesel and alternative fuels (biodiesel, natural gas and biogas), changing the composition of the combustible mixture and the injection timing of liquid fuel. Based on the change of theoretical and mathematical modelling parameters of the compression ignition engine, the influence of dual-fuel on the combustion process was determined to evaluate the economic efficiency of dual-fuel use. The dissertation consists of an introduction, three chapters, a summary of the results, lists of used literature and the author’s publications on the topic of the dissertation. The introductory chapter discusses the research problem and the relevance of the work, describes the object of research, formulates the aim and objectives of the work, presents the research methodology, the scientific novelty of the work, the significance of the results of the work and the defended statements. At the end of the introduction, the author’s publications and conference presentations on the topic of the dissertation are presented, as well as the structure of the dissertation. The first chapter is assigned to a literature review. It looks into the factors promoting the use of dual-fuel, research methodology and results of the use of natural gas and biogas in internal combustion engines. The chapter conclusions are formulated, and the tasks of the dissertation are specified. The second chapter presents a methodology for investigating the use of dual-fuels in internal combustion engines. The third chapter presents the results of experimental studies and numerical modelling of the use of dual-fuel in a compression ignition engine
Purification, Properties Investigation and Immobilization in Nanostructures of Sclerotinia Sclerotiorum Laccase Isoenzymes
No full textIšgryninti nauji Sclerotinia slerotiorum lakazės L241-1 ir L241-2 izofermentai, kurių molekulinės masės (nustatytos SDS-PAGE metodu) atitinkamai lygios 110±10 kDa ir 66±5 kDa. L241-1 izofermentas pasižymi geltonųjų lakazių spektrinėmis savybėmis, sugerties spektre jos neturi smailės 550–700 nm intervale, o L241-2 turi smailę šiame intervale, kas būdinga mėlynosioms lakazėms. Ištirtos L241-1 ir L241-2 izofermentų fiziko-cheminės savybės. L241-1 izofermentas pakankamai stabilus, o L241-2 aktyvumas priklauso nuo terpės, kurioje jis laikomas, ir temperatūros. Ištirtos L241-1 ir L241-2 izofermentų kinetinės savybės, t. y., substratinis specifiškumas tradiciniams lakazių substratams, flavonoidams, hidroksicinaminėms ir hidroksibenzoinėms rūgštims. Nustatytos reakcijos greičio priklausomybės nuo buferinių tirpalų pH. Atlikti įvairių druskų poveikio tyrimai L241-1 ir L241-2 izofermentų aktyvumui ir gauti rezultatai palyginti tarpusavyje. Pastebėta, kad L241-1 labiau atsparus įvairių druskų poveikiui nei L241-2 izofermentas. L241-1 ir L241-2 izofermentai imobilizuoti ant AuND dengtų Au elektrodų ir dengtų nanovamzdeliais anglies elektrodų. Tiesioginė elektronų pernaša nebuvo stebima imobilizavus šiuos izofermentus ant elektrodų. Imobilizavus L241-1 ir L241-2 izofermentus ant FeMND, nustatyta, kad šis metodas labiau tinka L241-1 lakazei, nes yra išsaugomos natyvaus izofermento savybės, priešingai nei L241-2 atveju. Darbą sudaro šešios dalys: įvadas, literatūros apžvalga, eksperimentinė dalis, rezultatai ir jų aptarimas, išvados, literatūra ir priedai. Darbo apimtis 69 p. teksto be priedų, 32 paveikslai, 11 lentelių, 45 bibliografiniai šaltiniai.New Sclerotinia slerotiorum laccase (L241-1 and L241-2) isoenzymes were purified, molecular weights were determined and equal 110 ± 10 kDa and 66 ± 5 kDa respectively. L241-1 isoenzyme is yellow laccase, because absorption spectrum peak in the range 550–700 nm was not observed, but the L241-2 isoenzyme absorption spectra has a peak in this range which is characteristic for blue laccases. Physico-chemical properties of L241-1 and L241-2 isoenzymes were investigated. L241-1 isoenzyme is enough stable and L241-2 activity depends on the medium in which it is stored, and temperature. L241-1 and L241-2 isoenzymes kinetic properties, i. e., the substrate specificity of traditional laccase substrates, flavonoids, hydroxycinnamic and hydroxybenzoic acids were investigated. The reaction rate dependence on the buffer solutions pH were determined. Investigations of different salts influence on L241-1 and L241-2 isoenzymes activity were performed and the results were compared with each other. It was observed that L241-1 is more resistant to the influence of various salts than L241-2 isoenzyme. L241-1 and L241-2 isoenzymes were immobilized on the Au electrode coated by AuNP and on the carbon electrodes coated by nanotubes. Direct electron transfer was not observed when isoenzymes were immobilized on the electrodes. Also L241-1 and L241-2 isoenzymes were immobilized on FeMND, and it was determined that this method is more suitable for L241-1 laccase, because the native isoenzyme properties were saved, unlike the L241-2. Structure: introduction, literature analysis, experimental part, discussion of the results, conclusion, references, appendices. Thesis consist of: 69 p. of text, 32 pictures, 11 tables, 45 bibliographical entries
Analysis of energy demand by a 24-hour store
No full textThe paper presents the balance of electricity consumption and fuel oil consumption of a medium-sized 24-hour store. Measurements of the electricity consumption of the various components of the balance were made for air conditioning, refrigeration, fast food, and especially for indoor and outdoor lighting. Their shares over the 12-month period of measurements were determined. Opportunities to reduce electricity consumption by changing the type of lighting of the facility were identified. Replacement of lighting reduced electricity consumption by 38535.8 kWh, which represented a total reduction of 21.2% in the store’s annual electricity consumption.Taip / Ye
Employee silence and employee voice as distinct constructs: A systematic literature review
No full textA debate among researchers that employee voice and employee silence are distinct constructs is going on for two decades. Furthermore, since 2021 studies are challenging, claimed, and demonstrated through empirical research that voice and silence are independent constructs. In addition, the idea of strategic silence was also presented in the year 2022, supporting this narrative. Hence the main aim of the current study is to provide a holistic picture of all those studies published in the last two decades (2003–2023) claiming voice and silence as unique concepts. For this purpose, the systematic literature review has been developed to know broadly used methodologies, theories, and concepts used in these studies. Furthermore, research gaps have been highlighted where future research is needed. Data were collected through two research databases, Scopus and Web of Science. This paper has expanded the literature in organizing the factual and theoretical knowledge through a systematic literature review for the first time. Thus, it will provide a roadmap for future researchers, human resource practitioners, and managers to understand the concept of voice and silence being unitary constructs and will open future avenues to work on in this sphere
Isolation and Biocidal Profile Determination of Saccharomyces Cerevisiae K2 Mycocin
No full textS. cerevisiae sintetinamo K2 toksino aptikimas ir analizė yra apsunkinti dėl žemo baltymo sintezės lygio, todėl šiame baigiamajame darbe kuriama efektyvi mikocino išskyrimo ir gryninimo sistema, paremta chromatografijos metodais, bei charakterizuotas negryninto K2 baltymo poveikis prieš gamtinius mikroorganizmus. Šiam tikslui pasiekti sekrecinė terpė, kurioje auginamos S. cerevisiae ląstelės, atskirta ir sukoncentruota 25 kartus. Atsižvelgiant į terpėje esančio K2 toksino struktūros ypatybes buvo pritaikyti gelfiltracijos, jonų mainų, hidrofobinės, afininės chromatografijos sorbentai, optimizuotos baltymo sorbavimo ir eliucijos sąlygos. Tikrinant baltymo grynumą elektroforetinės analizės metu bei įvertinant jo aktyvumą, parinkti trys gryninimo etapai, kuriuos sudaro SP-Sepharose katijonų mainų chromatografija, CM Sephadex C50 katijonų mainų chromatografija ir Sephadex G75 gelfiltracija. K2 toksino biocidinės savybės ištirtos prieš 24 skirtingų rūšių mieles, 11 iš jų – jautrios mikocino poveikiui. Darbą sudaro šešios dalys: įvadas, literatūros apžvalga, medžiagos ir metodai, rezultatai ir jų aptarimas, išvados ir literatūros sąrašas. Darbo apimtis: 64 p. teksto be priedų, 36 iliustr., 6 lent., 71 bibliografinis šaltinis, 3 priedai.The detection and analysis of K2 toxin synthesized by S. cerevisiae is complicated due to the low level of protein synthesis. Therefore, in this study, we developed an efficient mycocin isolation and purification steps based on chromatographic methods and characterized the effect of unpurified K2 protein against microorganisms found in nature. To achieve this goal, the synthetic medium in which S. cerevisiae cells were grown was isolated and concentrated 25-fold. Considering structural features of K2 toxin in the medium, protein sorbtion and elution conditions were optimized and different chromatography sorbents (gel filtration, ion exchange, hydrophobic, affinity chromatography) were applied. Three purification steps consisting of SP-Sepharose cation exchange chromatography, CM Sephadex C50 cation exchange chromatography and Sephadex G75 gel filtration were selected by checking the purity of the protein during electrophoretic analysis and evaluating its activity. The biocidal properties of K2 toxin have been studied against 24 different yeast species, 11 of which are sensitive to mycocin. The work consists of six parts: introduction, literature review, materials and methods, results and discussion, conclusions, references. Structure: 64 p. text without appendixes, 36 pictures, 6 tables, 71 bibliographical entries, 3 appendixes
The Living Megastructure in the Baltic Sea
No full textMagistro baigiamojo darbo tikslas – atlikus temos analitinę dalį suprojektuoti gyvenamąją megastruktūrą Baltijos jūroje. Gyvenamoji megastruktūra Baltijos jūroje yra gyvenamoji aplinka, populiarinanti gyvenimo ant vandens idėją. Tai ne tik turistinis – poilsio traukos abjektas, bet ir galimas nuolatinės alternatyvios gyvenamosios vietos sprendimas. Baigiamąjį darbą sudaro analitinė ir projektinė – tiriamoji dalys. Analitinėje dalyje nagrinėjama temos problematika, literatūros šaltiniai, analogai, susiję su gyvenimo ant vandens koncepcija, jos istorija, dabartine praktika. Projektinėje - tiriamojoje dalyje pateikiama situacijos analizė, projekto programa, projekto grafinė dalis su situacijos ir tūrio maketais.The aim of this master thesis is to design the living megastructure in the Baltic sea. The living megastructure is an exceptional setting for popularise the idea of living on water. This is not only tourist atraction, but also alternative permanent living solution. The paper consists of analytical and project parts. Analytical part presents collected main material about theme issues, analogues of living on water, its history and todays practise. Project part consists of location analysis, the programe of project, graphic part of project, situation and building models
The impact of paper sludge waste on physical & mechanical properties of cementitious materials /
No full textThe global production of paper is on the rise, thus leading to increasing amounts of waste in different stages of paper manufacture. Paper sludge waste is the most abundant and there is a big potential to reuse it after appropriate processing. This research paper analyses paper sludge waste fired at 900°C temperature for 2 h in terms of mineral composition, particle density and water demand in cement-based mixtures, as well as the effect of paper sludge waste on the density, ultrasonic pulse velocity, compressive strength and mineral composition of cement-based specimens. In the cement paste mixtures 0%, 2.5%, 5%, 7.5% and 10% of cement was replaced with paper sludge waste fired at 900°C temperature for 2 h. The ratio between water and solid substances was 0.35. Gehlenite and calcium oxide were found to prevail in the mineral composition of paper sludge waste, whereas water demand of cement-based mixture incorporating paper sludge waste increased 30%. The intensity of XRD curves revealed that a higher content (more than 7.5%) of paper sludge waste fired at 900°C temperature for 2 h in the mix increases the amount of portlandite and reduces the amounts of cement minerals: alite and belite. An empirical equation was drawn on the grounds of statistical analysis to calculate the compressive strength according paper sludge waste content fired at 900°C temperature for 2 h. The correlation and determination factors more than 0.9 demonstrate that the change of compressive strength in relation to paper sludge waste content can be described by the second degree polynomial equation and the optimum content of paper sludge waste fired at 900°C temperature for 2 h in the cement matrix is 5%. The highest density and ultrasonic pulse velocity values of cement stone specimens after 28 days of curing were obtained of specimens containing 5% paper sludge waste.iss. 1vol. 292