Theses (Faculty of Science and Technology)
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A DE Természettudományi és Technológiai Kar Tanácsának 2009. november 25.-i határozata alapján a jövőben elektronikus formában is elhelyezésre kerülnek a szakdolgozatok a Debreceni Egyetem Egyetemi és Nemzeti Könyvtár által működtetett egyetemi archívumban, a DEAba. A szakdolgozatok az archívumból kizárólag a Debreceni Egyetem IP-címeiről hozzáférhetőek, azokat nem lehet kinyomtatni, és azokból szövegrészeket nem lehet kiemelni.
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Megjelenítve 1 - 20 (Összesen 744)
Tétel Korlátozottan hozzáférhető A study and simulations of short interest rates and some effects on the market instruments using Vasicek ModelSukkar, Izzat; GÁLL, József; DE--Természettudományi és Technológiai Kar--Matematikai IntézetStudying the movements of short interest rates is a very important research field. Almost all banks and investment institutes borrow or lend money with floating interest rates. Thus, this study is essential to measure the risk and hedge it or to speculate a possible gain in the future. In this work we will focus on researching the short interest rates movements using Vasicek model and review some other models. Simulations for the interest rates and market instruments are presented using the Vasicek model in R.Tétel Korlátozottan hozzáférhető Identifying Suitable Hospitals for Solar-Powered Green Hydrogen Integration in Debrecen, HungaryMagraby, Ahmed; Túri, Dr. Zoltán Krisztián; Lázár, Dr. István; DE--Természettudományi és Technológiai Kar--Földtudományi IntézetThis thesis evaluates the feasibility of integrating solar-powered green hydrogen systems into hospitals in Debrecen, Hungary, by combining GIS-based spatial analysis with solar-radiation modeling. It first identifies suitable hospital rooftops and nearby sites using multiple Digital Elevation Models (SRTM, Copernicus, ALOS) and land-cover, urban-density, and protected-area data to create a national “suitability” map. Focusing on three local facilities, in Vitro Building, Kenézy Gyula Hospital, and Medicover Debrecen, it calculates 10-year average solar radiation values (approximately 626, 792, and 686 kWh/m², respectively) via ArcGIS Pro’s Raster Solar Radiation tool. Case studies from the Netherlands’ Rijnstate and Spain’s Viamed San José hospitals demonstrate real-world green hydrogen integration. Results show strong technical viability for Debrecen’s hospitals to generate clean hydrogen and medical-grade oxygen on-site, potentially reducing carbon emissions and enhancing energy security. The work contributes a reproducible geospatial methodology for planning decentralized renewable-hydrogen energy in critical-infrastructure settings.Tétel Korlátozottan hozzáférhető First order systems of ordinary differential equations having a given four-dimensional Lie group as their symmetry groupMaingi, Stephen Wachira; Figula, Ágota; DE--Természettudományi és Technológiai Kar--Matematikai IntézetWe determine systems of the first order ordinary differential equations such that their group of symmetries contains the four-dimensional filiform Lie subgroup. The solutions of the obtained systems of first order ordinary differential equations are computed using the infinitesimal generators of their symmetries. We also determine the equivalent second order systems and compare them with the equation of geodesics in an arbitrary coordinate frame of a Riemannian space it turns out that the second order systems describe motions of a particle moving in a fluid. The motion is caused by a viscous force depending only on the velocity. We also investigate Kundt structures in the four-dimensional Lie algebra g_4.1. We determine the corresponding three-dimensional abelian and non-abelian subalgebras of the Lie algebra g_4.1. We investigate the left invariant Lorentz metrics corresponding to these subalgebras and find out which pairs of the Lie algebras and their corresponding left invariant Lorentz metrics are of Kundt type.Tétel Korlátozottan hozzáférhető Optimizing burn area mapping with Sentinel-2: A comparative evaluation of spectral indices for accurate and efficient post-fire delineationMutune, James Muinde; Bertalanné Balázs, Boglárka; DE--Természettudományi és Technológiai Kar--Földtudományi IntézetThis study evaluates Sentinel-2 imagery for wildfire detection and post-fire assessment by comparing spectral indices (NDVI, BAI, BAIS2, CSI, NBR) using the separability index and accuracy metrics validated with PlanetScope data. The differenced Normalized Burn Ratio (dNBR) was most effective, achieving 90.7% accuracy and a Kappa of 0.8. Future research should explore machine learning methods, test indices across ecosystems, assess temporal stability, develop field validation databases, and integrate Sentinel-2 with other sensors like SAR and UAVs to improve fire mapping and overcome cloud cover issues.Tétel Korlátozottan hozzáférhető Accuracy constraints of different UAV sensor data of a landslide survey in HungaryNkunzi Rugamba , Fabrice; Bertalan, Laszlo; DE--Természettudományi és Technológiai Kar--Földtudományi IntézetThis study is about using modern technology to study and measure landslides, which are very dangerous events where rocks, soil, or mud slides down hills or mountains. Landslides can cause serious problems. Because they destroy homes, roads, farms and sometimes even take people’s lives. In many places around the world. These particular events they often happen mostly during heavy rain or because of different human activities like farming, deforestation and poor building methods. This topic was chosen in order to solve real-life problem in my country Rwanda and to gain skills in using smart technology to keep people safe. The study has several goals like how to detect landslide using LIDAR technology and different methods for analyzing results, get real results, and reduce landslide impact using remote sensing and 3D point cloud technology. This study uses remote sensing technology like LIDAR. INSAR and UAVs. These tools allowed the scanning from the sky without needing to go to dangerous place. Lidar uses laser beams to measure the land’s shape. Drones take many pictures, and special software is like Agisoft Metashape turns these images into 3D models. The study was done into steps where, the first step was fly the drone over the study area to take many high-quality pictures. These pictures were cleaned and processed to remove vegetation so that the land could be seen clearly. Then LIDAR and structure from motion (SFM) method were used to create 3D point cloud. Millions of small points and these points shows the land’s surface very Cleary. These point clouds were turned into digital elevation models (DEMs). DEMs are 3D maps that show the height and shape of the land. Finally, software’s like SAGA GIS, Arc GIS, Cloud compare, QGIS and past were used to analyze and get Statistical results and basic terrain analysis.Tétel Korlátozottan hozzáférhető Classification of Urban Areas Between 1986-2022 with Machine Learning in Atlantico ColombiaPardo Gomez, Alexandra Carolina; Abriha, Dávid; DE--Természettudományi és Technológiai Kar--Földtudományi IntézetMachine Learning algorithms are currently being studied for their applications on image classification procedures, where with the help of training and test data, remote sensed images land covers can be classified. In this study two Machine Learning methods are being tested and evaluated to analyze their performance on urban cover classification: Support Vector Machine and Random Forest. To accomplish it, three images of different time periods (1986, 2000 and 2022) from the Atlantico Department in Colombia were obtained, training and test data generated, and the algorithms were tuned and evaluated. Finally, the results from this procedure was analysed and discussed.Tétel Korlátozottan hozzáférhető Quasi-Arithmetic Means and its ApplicationsRotich, Jemimah; Szokol, Patricia; DE--Természettudományi és Technológiai Kar--Matematikai IntézetThe motivation was to introduce quasi-arithmetic means and explore their key properties. The study also explores how quasi-arithmetic means contribute to risk assessment and decision-making, especially within the context of investment portfolio management. These means provide a flexible framework for preference aggregation, enabling investors to tailor risk-return trade-offs according to their individual goals. In portfolio optimization, these means serve several critical roles. They enhance risk-adjusted return calculations, support customized utility-based decision-making, refine capital allocation strategies, and improve the aggregation of nonlinear risks.Quasi-arithmetic means offer a powerful and adaptable tool for financial decision-making.Tétel Korlátozottan hozzáférhető Continuity concepts for set valued mappings with applications in Game TheoryOtieno, Vanessa Achieng; Boros, Zoltán; DE--Természettudományi és Technológiai Kar--Matematikai IntézetThe main idea of this thesis is to demonstrate the connections of various semi-continuity properties to each other as well as to present that one can involve such results into game theory in a natural way. We investigate upper hemi-continuous set valued mappings in order to obtain selection and fixed point theorems. We apply Kakutani's fixed point theorem to the best response mapping of a concave game in order to obtain a general existence theorem in game theory. Specific pairs of interval valued mappings with semi-continuous limits are investigated as well.Tétel Korlátozottan hozzáférhető Mathematical models for monopoly and oligopoly strategiesOmwenga, Elvis Onguti; Boros, Zoltán; DE--Természettudományi és Technológiai Kar--Matematikai IntézetIn this thesis some details of mathematical models related to or describing the behavior of producers at not totally competitive markets are elaborated. The focus is on presenting how the developments in Game Theory made it possible to consider it as a conjoint framework of all formerly introduced Oligopoly Market models in Mathematical Economy. In particular, we present the concepts of strategic games and Nash Equilibrium. We determine the best response mappings and the equilibrium in Cournot's and Bertrand's Duopoly Markets with linear demand. Oligopoly Markets are investigated as well.Tétel Korlátozottan hozzáférhető Constructing the Efficient Frontier: An Empirical Analysis of Hungarian Stock Market PortfoliosSusanti, Susi; Gáll József Mihály; DE--Természettudományi és Technológiai Kar--Matematikai IntézetThis thesis investigates the evolution of optimal portfolio construction and systematic risk in the Hungarian equity market across two periods: 2013–2015 and 2023–2025. Using Modern Portfolio Theory, it examines the efficient frontier, Minimum Variance and Tangency Portfolios, and beta estimation for OTP Bank relative to both the BUX index and the tangency portfolio. The results reveal a notable improvement in the risk-return profile of optimal portfolios in the more recent period, driven by enhanced diversification and more stable market conditions. Beta estimates show OTP’s increasing sensitivity to market-wide movements, while its alignment with the tangency portfolio remains weak.Tétel Korlátozottan hozzáférhető HYBRID WI-FI AND LORA-BASED IOT SYSTEM FOR INDOOR ENVIRONMENTAL MONITORINGKwasu, Nissi; István, Csarnovics; DE--Természettudományi és Technológiai Kar--Fizikai IntézetThis thesis presents the design and implementation of a hybrid Wi-Fi and LoRa-based IoT system for indoor environment monitoring. It uses ESP32 microcontrollers and a range of digital and analog sensors to measure parameters like temperature, humidity, AQI, UV light, noise, and light intensity. Custom PCBs were designed and fabricated to integrate the sensors and microcontrollers efficiently. Sensor data is transmitted via Wi-Fi and LoRa to a central node, which displays real-time values through a web interface using WebSocket communication. All collected data is stored in a MySQL database for long-term analysis and trend tracking. Evaluation showed strong performance in power efficiency, data acquisition accuracy, and communication reliability. The system provides a scalable, low-cost solution for continuous environmental monitoring in indoor spaces.Tétel Korlátozottan hozzáférhető Studies on the Effect of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Spike Protein on Macrophage PolarizationAbu-leil, Sofia; Mahdi, Mohamed; Al-Muffti, Aya; DE--Természettudományi és Technológiai Kar--Biológiai és Ökológiai IntézetThis thesis investigates the impact of the SARS-CoV-2 spike (S) protein on macrophage polarization and cytokine secretion. The spike protein, central to viral entry and the primary antigen in most COVID-19 vaccines, was studied using transfection of THP-1-derived macrophages. Our findings showed that spike expression did not significantly shift macrophages toward either M1 or M2 phenotypes. However, a modest but statistically significant increase in IFN-α secretion was observed in M2-polarized cells. No such increase was seen in M1 macrophages. These findings contribute to a broader understanding of how spike protein may subtly influence immune responses, with implications for viral pathogenesis and vaccine design.Tétel Korlátozottan hozzáférhető Investigation of Carbon Nanodots in Yeast Toxicity TestOrtea, Hannah Grace; Prokisch, József; Nguyen, Duyen; DE--Természettudományi és Technológiai Kar--Biológiai és Ökológiai IntézetThis study investigated the toxicity of carbon nanodots (CNDs) derived from biomolecular precursors namely glycine, urea, lysine, and citric acid synthesized using thermal processing. The investigation of toxicity of these CNDs samples was done by measuring the foam height progression of the yeast suspensions which is indicative of the model organism's metabolic activity by CO2 production. The statistical models used showed no significant difference on the foam height measurements between the groups at each time point over the course of the whole experiment. However, strong statistical significance on the differences of the measurements between different timepoints under all conditions was observed. The findings suggest that the CNDs have no toxic effect on the model organism since normal yeast foaming activity was still evident upon the addition of the sample CNDs. While this study is limited to short-term exposure, the results could serve as a starting point for further research into the long-term effects of nanomaterials on microbial respiration and possibly beyond that, by beginning an understanding on how nanomaterials and biological systems interact.Tétel Korlátozottan hozzáférhető Nutrient availability and its impact on the growth of Flavobacterium and Pseudomonas in autoclaved lake water and hydra mediumNuryyeva, Bahar; Tökölyi , Jácint; DE--Természettudományi és Technológiai Kar--Biológiai és Ökológiai IntézetThis thesis showed how nutrient availability affects the growth dynamics of two Hydra-associated bacterial species, Flavobacterium and Pseudomonas , using autoclaved lake water (ALW) and Hydra medium (HM). The initial hypothesis, predicting higher growth in nutrient-rich ALW, was only partially supported. Flavobacterium showed slightly higher CFU counts in ALW, while Pseudomonas unexpectedly grew more in HM. However, neither result was statistically significant. These results suggest that factors beyond nutrient content, such as metabolic preferences or substrate specificity, may influence bacterial proliferation. The limited number of replicates likely reduced the study's statistical power, emphasizing the need for larger sample sizes in future experiments. Overall, the research shows that microbes can respond to their environment in complex ways, and careful planning is important when designing such experiments.Tétel Korlátozottan hozzáférhető Compensatory Growth in Hydra oligactis and the Effect of CuSO4Mohamed Shihab, Randa; Tökölyi, Jácint; DE--Természettudományi és Technológiai Kar--Biológiai és Ökológiai IntézetIn this experiment, we carried out direct body size manipulation on Hydra oligactis to observe compensatory growth, and test the toxicity of the resulting hydras to Copper (II) Sulfate. We divided them into two groups, namely the Reduced and Control. The Reduced group had a body portion excised while the Control was simply cut once and put back together. Hydras were left to rejoin on a capillary needle for 1-2 hours or more if necessary. They were photographed and the size was measured with ImageJ before and after this procedure, as well as before the CuSO4 toxicity test. We also observed the morphological changes in hydra due to CuSO4 using the Wilby (1988) scale 48hrs after this test. Welch’s t-tests and a Kruskal Wallis test was carried out to asses the significance of results obtained. Our results show that Reduced hydra did undergo a decrease in body size due to grafting one day after, and half of them have undergone compensatory growth within this group. However, compensatory growth was not visible as compared to the Control group. Furthermore, when the Wilby scores from the CuSO4 toxicity test were observed, we found that both groups showed similar results in terms of toxicity. Therefore, compensatory growth was not found to have any effect on CuSO4 toxicity.Tétel Korlátozottan hozzáférhető Effects of antimicrobial treatment on the mortality rates of Hydra oligactis at varying temperaturesIevlev, Andrei; Tökölyi, Jácint; DE--Természettudományi és Technológiai Kar--Biológiai és Ökológiai IntézetIn conclusion, the presence of bacteria significantly affects Hydra longevity. Bacteria-free Hydra oligactis can survive significantly longer compared to those with an intact microbiome when undergoing starvation at low temperature, indicating that the native microbiome has a net cost to longevity in this context. Keeping the hydras at 12 °C made them die sooner, suggesting that warmer conditions speed up this process due to a higher metabolic cost. At the same time, reintroducing the microbiome after antibiotic treatment seems to have a harmful effect, which highlights the importance of a finely balanced native microbiota. Rather than protecting the host from dying, the microbiome might take part in age-associated decline – possibly by opportunistic overgrowth or insufficient support of host tissue maintenance when the host is subjected to stressful conditions. Our results provide experimental evidence supporting the idea that Hydra’s immortality (or mortality) is not a fully intrinsic trait but is a result of symbiotic relations with its microbial partners.Tétel Korlátozottan hozzáférhető Quantification of Carbon Dioxide DegassingYounes, Yassin; István, Csige; DE--Természettudományi és Technológiai Kar--Fizikai IntézetI will study gases released from soil. Emissions of volcanic-related CO2 are themselves potentially dangerous because these gases originate from deep near-surface layers. Understanding gas flows under the surface helps us design protections against them. The sources of CO2 are investigated.Tétel Korlátozottan hozzáférhető Investigation of aerosol pollution in different types of buses in DebrecenMakau, Faith Mumbua; Angyal , Anikó; Enikő , Papp; DE--Természettudományi és Technológiai Kar--Fizikai IntézetThis study examines aerosol pollution in Debrecen's various bus fleets. It draws attention to the abundance of particulate matter in the interior of both diesel and electric buses. Data was obtained using the optical particle sizer (OPS) and subsequently adjusted through a number of computations to produce useful data. Later, this data was utilised to illustrate the concentration differences between different stops in the two bus types during the spring and autumn seasons. The electric and diesel buses were compared, as well as the spring and autumn seasons.Tétel Korlátozottan hozzáférhető Synthesis of half sandwich-type osmium and ruthenium complexes as potential anticancer agents with C-(galactopyranosyl)formaldehyde benzoylhydrazonesTrinh, Huyen Anh; Tóth, Marietta; Tóth, Éva; DE--Természettudományi és Technológiai Kar--Kémiai IntézetDuring this work sugar containing half-sandwich of osmium and ruthenium metal complexes have been synthesized and patented. Some have shown (sub)micromolar cytostatic activity against carcinoma, lymphoma and sarcoma cancer cells as well as antibacterial activity against multiresistant Gram positive bacteriaTétel Korlátozottan hozzáférhető Synthesis of sugar-based half sandwich-type platinum-group metal complexes as potential anticancer agentsGikoshvili, David; Vágvölgyiné Tóth, Marietta; Juhászné Tóth, Éva; DE--Természettudományi és Technológiai Kar--Kémiai IntézetCancer is one of the deadliest diseases. Conventional platinum-based medicine has limitations due to toxicity and long-term cell resistance. Sugar-based drugs may be the answer to the problem along with changing the core metal of complex medications