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Investigation of asynchronous generator application to power oscillation damping.
No full textThe final master's thesis is dedicated to investigating the capabilities of an asynchronous generator to damp active power oscillations arising in the electrical power system. In the first part of the study, a literature review is conducted, in which the importance of power system stability is discussed, along with the classification of power system stability based on the main system parameters. This section also analyzes the causes of active power oscillations and the impact of this process on the system. Since the asynchronous generator is modeled using a wind power plant control algorithm in the final research, a review of wind power plants is also conducted. This review identifies different types of wind power plants and the possibilities for damping power oscillations. In the second part, a model is created to study active power oscillations. This section provides a detailed description of the system components used, their parameters, control algorithms, additional controllers, and testing modes. The model is developed using MATLAB software in the Simulink environment. In the third part, the results of the system and the asynchronous generator are presented, which are obtained by examining the active power oscillation process. The results show that the modified asynchronous generator with a wound rotor can be effective in damping both stable and unstable active power oscillations in the system
Gelation of different phases of probiotic-loaded water-in-oil-in-water emulsion to enhance probiotic survival stability /
No full textThis study aimed to develop water-in-oil-in-water (W1/O/W2) double emulsion gels (DEGs) with Lactiplantibacillus plantarum subsp.plantarum and Limosilactobacillus reuteri encapsulated within the inner aqueous phase (W1), with a focus on improving probiotic viability under adverse environmental conditions. The system incorporated gelling agents to enhance emulsion stability, including whey protein crosslinked with calcium chloride to gel the W2 phase and carnauba wax as an oleogelator to solidify the O phase. Three formulations were investigated: W2-gelled, O-gelled, and dual-phase gelled systems. Our study demonstrated that designed DEGs loaded with probiotics effectively maintained cell count in a sufficient amount (more than 6 log CFU/g) during 56-day storage, heat treatment (at 60 °C and at 72 °C for 1 hr), and four freezing–thawing cycles compared to free cells. During simulated digestion, free probiotic cells exhibited substantial cell reduction, particularly after intestinal digestion, with cell loss ranging from 3.00 to 3.50 lg colony forming unit (CFU)/g. However, encapsulation within DEGs effectively enhanced probiotic survival, minimising cell reduction throughout digestion with cell loss around 1 lg CFU/g. These findings highlight the practical application of W/O/W phase-specific gelling agents to enhance structural integrity and probiotic survival. The DEG matrix outperforms traditional encapsulation, providing superior probiotic stabilisation under stressors
Carbazolyl electron donor and pyridinyl electron acceptor containing derivatives as potential host materials for green organic light-emitting diodes /
No full textHere, we present two series of new electroactive compounds containing electron donors (carbazolyl) and electron acceptor (pyridinyl) fragments as potential host materials. The objective compounds 9-(2-ethylhexyl)-3,6-di [3-(methoxypyridin-3-yl)carbazol- 9-yl]carbazoles RB71 and RB74 were synthesized by an Ullmann coupling reaction between the intermediate derivatives: 9-(2-ethylhexyl)-3,6-diiodocarbazole and corresponding 3-(methoxypyridin-3-yl)-9H-carbazole. Other target derivatives, 9-alkyl-3-[N-(9- alkylcarbazol-3-yl)-N-(4-methylpyridin-2-yl)amino]carbazoles RB70 and RB75, were also prepared, according to the Ullmann reaction method, from 2-amino-4-methylpyridine and the corresponding 3-iodo-9-alkylcarbazole. Thermogravimetric analysis confirmed that the new derivatives are highly thermally stable compounds, with 5% weight loss in the temperature range of 349 ◦C to 488 ◦C. According to differential scanning calorimetry results, some amorphous materials exhibit very high glass transition temperatures exceeding 150 ◦C in some cases, which is a significant advantage for compounds with potential applications in organic light-emitting devices. The electroluminescent properties of devices utilizing the new hosts RB71 or RB70 with 5.0, 10.0, 15.0, and 20.0 wt.% concentrations of the dopant tris(2-phenylpyridine)iridium(III), Ir(ppy)3, were demonstrated. All the PhOLEDs emitted light at approximately 515 nm with CIE coordinates of (0.30, 0.61) due to Ir(ppy)3 emissions. The most efficient device with RB71 host demonstrated a maximum power efficacy of 8.0 lm/W, maximum current efficiency of 12.7 cd/A, and maximal external quantum efficiency of 5.4% with a relatively low turn-on voltage of 4.3 eV, as well as luminance exceeding 4000 cd/m2. Additionally, 15 wt.% Ir(ppy)3 emitter-based PhOLED with RB70 host outperformed the other devices by displaying a maximum power efficacy of 9.6 lm/W, maximum current efficiency of 16.0 cd/A, and maximal external quantum efficiency of 6.7% with a relatively low turn-on voltage of 3.7 eV, as well as luminance reaching 11,200 cd/m2. Some devices seem to exhibit higher efficiencies than those previously reported for OLEDs that utilize a 4,4′-bis(9-carbazolyl)-2,2′-biphenyl (CBP) host
Impact of thermal and ultraviolet treatments on the structural, mechanical, and laser ablation properties of fluorinated ethylene propylene films /
No full textFluorinated ethylene propylene (FEP) films were subjected to heat, UV, and heat–UV treatments. Structural changes that occurred after these treatments were recorded via X-ray diffraction (XRD), microtensile, and laser ablation testing. XRD macromolecular orientation texture analysis revealed changes in the fraction of crystalline components and the degree of anisotropy of the FEP films after being subjected to different processing conditions. Heat treatment at 200 °C affected structural properties by rearranging the crystallites and resulting in a higher degree of anisotropy. By contrast, the UV treatment of FEP resulted in a lower degree of anisotropy. The changes in anisotropy and crystallinity of FEP films significantly affected their Young’s modulus and yield stress. The UV laser ablation threshold values were found to be lower for the heat-treated FEP films
CBL meso-level frame case studies: case study nine: using CBL in a specific extra-curricular model /
No full textInfluence of diallyl disulfide on the properties of biobased antimicrobial vitrimers for microimprint lithography /
No full textThis work contributes to the development of sustainable materials by creating biobased photopolymerized vitrimers with antimicrobial, shape-memory, and self-welding capabilities, essential for industries using light-based manufacturing technologies where petroleum-based materials lacking such properties are currently used. In this study, the influence of the amount of diallyl disulfide, which has antimicrobial properties and forms dynamic bonds, on the vitrimeric behavior and antimicrobial activity of biobased vitrimers synthesized from acrylated epoxidized soybean oil, 2-hydroxy-3-phenoxypropyl acrylate, and diallyl disulfide was determined. The addition of 0.35 mol of diallyl disulfide to a resin containing 1 mol of acrylated epoxidized soybean oil and 1 mol of 2-hydroxy-3-phenoxypropyl acrylate was found to reduce resin viscosity by 55%, photocuring rate by 30% and shrinkage to 0%, and increase polymer flexibility by 53%. These polymers exhibited excellent self-welding and shape-memory properties enabled by dynamic disulfide bond exchange. Antimicrobial tests have shown that resins containing more than 0.05 mol of diallyl disulfide, 1 mol of acrylated epoxidized soybean oil, and 1 mol of 2-hydroxy-3-phenoxypropyl acrylate inhibit the bacterial growth of Escherichia coli by more than 97%, Staphylococcus aureus by more than 49%, as well as the fungal growth of Aspergillus flavus by more than 83%, and Aspergillus niger by more than 38% after 1 h of direct contact with the bacterial or fungal suspensions. Micrometer-scale patterns formed using microimprint lithography confirmed the potential of these vitrimers with diallyl disulfide moieties as antimicrobial advanced engineering materials for applications where flexibility and sustainability are required
Electrically conductive nanoparticle-enhanced epoxy adhesives for localised joule heating-based curing in composite bonding /
No full textThis study investigates the application of carbon nanotube (CNT)-enhanced epoxy adhesives for localised Joule heating-based curing in composite bonding. The electrical, thermal, and mechanical properties of epoxy with 0.25-1 wt% CNT loadings were evaluated. A simple CNT alignment method using DC voltage showed improved electrical conductivity, greatly reducing the percolation threshold. Transient thermal analysis using finite element modelling of representative volume elements revealed that aligned CNTs led to increased localised temperatures near the CNT clusters. The model was validated with infrared thermal imaging analysis, which also showed similar non-linear heat distribution and more uniform heating under higher CNT loading. Additionally, power distribution mapping was evaluated through inverse modelling techniques, suggesting different conductivity zones and cluster distribution within the single-lap joint. The numerical and experimental results demonstrated that CNT alignment significantly enhanced localised conductivity, thereby improving curing efficiency at lower voltages. The lap shear test results showed a peak shear strength of 10.16 MPa at 0.5 wt% CNT loading, 9% higher than pure epoxy. Scanning electron microscopy analysis confirmed the formation of aligned CNT clusters, and how CNT loading affected the failure modes, transitioning from cohesive to void-rich fracture patterns at a higher wt%. These findings establish CNT-enhanced Joule heating as a viable and scalable alternative for efficient composite bonding in aerospace and structural applications
Factors determining employees' adaptation to new technologies.
No full textThe final thesis examines the factors influencing employees’ adaptation to new technologies. The object of the research is an accounting service company in Kaunas, whose employees’ experiences were analyzed using a qualitative research method—semi-structured interviews. The study distinguishes two main groups of factors: problem-oriented (level of technological skills, regular use, perceived practical benefits) and emotion-oriented (motivation, stress management, personal characteristics). The empirical research shows that motivation and the practical application of technologies at work are the main factors facilitating adaptation, while clear instructions and favorable technology design reduce learning barriers. Employees’ personal qualities, such as perseverance and previous experience, also ease the adaptation process. The results of the study reveal that in order to successfully implement technological changes in an organization, it is essential to strengthen employee motivation, provide practical training, and ensure support
Evaluation of the impact of financial technologies on the financial performance of the banking sector in Lithuania.
No full textCurrent financial markets are undergoing rapid changes driven by the development of financial technology, globalisation and the ever-changing needs of consumers, and the banking sector, as a key part of the economy, must constantly adapt to these transformations. Digitalisation processes are fundamentally changing the traditional banking business, encouraging the introduction of new technological solutions. Innovation is not only changing the delivery models of financial services, but also transforming the sources of profitability and risk management mechanisms, underlining the importance of digitisation, automation, customisation, speed and lower costs. The growing interest in financial technology services is driving investment in the financial technology sector, which has a significant impact on both financial markets and the overall economy. In this context, it becomes crucial to analyse the impact of the services of financial technology companies on the financial performance of banks. The problem of this final project stems from a debate in the academic literature, with some researchers arguing that the entry of fintech firms into the market reduces traditional banks' revenues by attracting their customers and increasing competition, while others believe that banks can ensure long-term profitability through the timely adoption of innovations and collaboration with fintech firms. Therefore, it is relevant to identify the impact of financial technology on the financial performance of the banking sector. The first part of the paper examines the importance of assessing the impact of financial technology on the financial performance of the banking sector and justifies the need for the study. The second part of the paper provides a theoretical analysis of the impact of financial technology on the financial performance of the banking sector. The third part formulates the research methodology. The fourth part develops a practical study on the impact of financial technology on the financial performance of the Lithuanian banking sector. The correlation analysis shows that there are both positive and negative correlations between financial technology indicators and the financial performance of the Lithuanian banking sector. This suggests that certain aspects of financial technology may be associated with an increase in the financial performance of the banking sector, while others, on the contrary, may be associated with a decrease in the financial performance of the banking sector. However, it is important to note that not all increases in financial performance are positive and decreases are negative, as changes in financial performance indicators are not interpreted in a straightforward manner. An exception is the NPL ratio, whose decline is considered a positive phenomenon as it reflects a more effective management of credit risk by banks. The regression analysis revealed that while the values of most financial technology indicators are increasing, the indicators reflecting the financial performance of the Lithuanian banking sector are decreasing. This trend can be explained by the fact that the increasing use of financial technology strengthens competition with traditional banks. This may lead to a loss of customers and profits for banks, which has a negative impact on their financial position. The results of the study show that the growth of financial technology has had a negative impact on the financial performance of the Lithuanian banking sector in the period from Q4 2015 to Q3 2024