African Journal of Science, Technology, Innovation and Development最新文献

{"title":"Review and comparison of methods for limiting leakage currents in single-phase transformerless PV inverter topologies","authors":"W. Kołodziejski, J. Jasielski, S. Kuta, G. Szerszeń, W. Machowski","doi":"10.55225/sti.477","DOIUrl":"https://doi.org/10.55225/sti.477","url":null,"abstract":"Transformerless inverters are widely used in different photovoltaic nonisolated ac module applications, mainly in grid-tied photovoltaic (PV) generation systems, due to the benefits of achieving high efficiency over a wide load range, and low cost. Various transformerless inverter topologies have been proposed to meet the safety requirement of low ground leakage currents, such as specified in the VDE-4105 standard and low-output ac-current distortion. Topology modifications of transformerless full bridge inverters are designed to balance and maintain a constant common mode output voltage, thereby eliminating or reducing leakage currents. This article reviews and compares the different methods for limiting leakage currents in known topologies of the full-bridge transformerless inverters, such as: H4, H5, H6, HERIC, and their improvements. The main topologies and strategies used to reduce the leakage current in transformerless schemes are summarized, highlighting advantages and disadvantages and establishing points of comparison with similar topologies. To compare the properties of different medium to high power inverters, PV inverter topologies were implemented using IGBTs and tested with the same components, same simulation parameters in PSPICE to evaluate their performance in terms of energy efficiency and leakage current characteristics. The detailed power stage operating principles, extended PWM modulator, and integrated universal gate driver with galvanic isolation in the transmission path of control signal for all IGBTs of the inverter, as well isolated and floating bias power supply for gate drivers are described.","PeriodicalId":7557,"journal":{"name":"African Journal of Science, Technology, Innovation and Development","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90934776","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Porównanie wyników badania sondą krzyżakową i penetrometrem tłoczkowym jako przykład lokalnych zależności korelacyjnych","authors":"T. Bardel","doi":"10.55225/sti.443","DOIUrl":"https://doi.org/10.55225/sti.443","url":null,"abstract":"Badania polowe i laboratoryjne gruntów dostarczają dużą ilość danych, jednak większość z nich stanowią parametry pomierzone, które z wykorzystaniem różnych wzorów i korelacji przelicza się na parametry wykorzystywane do projektowania. Stosowanie ogólnych korelacji do ich przeliczania nie zawsze prowadzi do uzyskania kompatybilnych wartości, dlatego pożądane jest poszukiwanie lokalnych zależności korelacyjnych. W niniejszym artykule przedstawiono zależność korelacyjną pomiędzy wytrzymałością na ścinanie bez odpływu uzyskiwaną z sondy krzyżakowej FVT i penetrometru tłoczkowego dla glin zwałowych rejonu Tarnowa. Na podstawie tej korelacji opracowano krzywą zależności oporu wcisku penetrometru tłoczkowego i stopnia plastyczności. Korelację tę wykorzystano następnie przy badaniu mad gliniastych doliny Dunajca, uzyskując wysokie wartości współczynnika korelacji. Otrzymane wyniki potwierdzają przydatność penetrometru tłoczkowego jako metody szybkiego określania wytrzymałości na ścinanie bez odpływu oraz stopnia plastyczności.","PeriodicalId":7557,"journal":{"name":"African Journal of Science, Technology, Innovation and Development","volume":"269 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90772948","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gospodarka odpadami komunalnymi w gminie Skrzyszów","authors":"Tomasz Kolak, Katarzyna Maj-Zajezierska","doi":"10.55225/sti.452","DOIUrl":"https://doi.org/10.55225/sti.452","url":null,"abstract":"W artykule przeanalizowano system gospodarki odpadami komunalnymi w gminie wiejskiej Skrzyszów w latach 2016–2102. Analiza została opracowana na podstawie rocznych sprawozdań tworzonych i publikowanych przez Urząd Gminy. Analiza wykazała, że system selektywnej zbiórki odpadów funkcjonuje prawidłowo oraz mieszkańcy oddają odpady komunalne w PSZOK Pogórska Wola. Co roku wzrasta masa odpadów komunalnych wytworzonych przez mieszkańca gminy Skrzyszów, w roku 2021 wyniosła 309 kg. Analiza frakcji odpadów komunalnych odbieranych z gospodarstw domowych wykazała, że największy udział masowy mają odpady biodegradowalne, wielkogabarytowe oraz opakowania szklane. Podobnie dominującą frakcją wśród odpadów komunalnych oddawanych do PSZOK były odpady gabarytowe, zwłaszcza zużyte opony. Gmina Skrzyszów osiągnęła założone poziomy recyklingu odpadów biodegradowalnych, odpadów budowlanych oraz odpadów papieru, metali, tworzyw sztucznych i szkła określone w Planie Gospodarki Odpadami dla Województwa Małopolskiego na lata 2016–2022.","PeriodicalId":7557,"journal":{"name":"African Journal of Science, Technology, Innovation and Development","volume":"55 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83774456","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On certain weighted Schur type inequalities","authors":"Tomasz Beberok","doi":"10.55225/sti.463","DOIUrl":"https://doi.org/10.55225/sti.463","url":null,"abstract":"In this note we give sharp Schur type inequalities for univariate polynomials with convex weights. Our approach will rely on application of two-dimensional Markov type inequalities, and also certain properties of Jacobi polynomials in order to prove sharpness.","PeriodicalId":7557,"journal":{"name":"African Journal of Science, Technology, Innovation and Development","volume":"74 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76559052","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Morphology of household waste on the example of Sri Lanka and Poland — case study","authors":"E. C. J. Perera, Marek Chyc","doi":"10.55225/sti.454","DOIUrl":"https://doi.org/10.55225/sti.454","url":null,"abstract":"Household waste is a global problem that many countries cannot cope with and deal with difficulty. In many regions of the world, a dynamic increase in the amount of waste generated is observed, which causes significant environmental pollution and excessive use of non-renewable resources. In the case of household waste, important indicators are not only its quantity per person but also its morphology. This study compares the amount of waste generated and its morphology by a household in Sri Lanka (Colombo) and Poland (Tarnów). The presented data comes from 2022, during a time of economic crisis caused initially by the COVID-19 pandemic and then due to the war between Russia and Ukraine. Currently, Sri Lanka is going through one of the greatest economic crises in its history. Poland is currently experiencing high inflation and reduced demand for many consumer goods due to continuous price increases. These events significantly affect the demand for various types of consumer goods and, paradoxically, this may reduce the amount of waste generated. It is important to identify and implement new strategies to recycle or optimize the usage of waste and develop value added products that would, in turn, have a positive impact on the domestic waste awareness. The results of the conducted research indicate a  significant share of biodegradable waste in the stream of generated waste, especially in Sri Lanka. The vast majority of generated waste can be recycled, but sorting is required. Comparing the data obtained from this case study, 71% of food waste is generated in Sri Lanka, whereas 22.1% is generated in Poland. This indicates that Poland produces a significant amount of processed food. Moreover, the recorded plastic waste produced by Polish families is twice that of Sri Lanka. Furthermore, both countries indicate a positive trend to generate more waste in the future despite economic challenges faced locally as well as globally. Therefore, it is vital to understand the amount and morphology of waste as well as to implement more efficient and economical strategies to eliminate negative impacts.","PeriodicalId":7557,"journal":{"name":"African Journal of Science, Technology, Innovation and Development","volume":"62 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88842865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ocena stanu gospodarki odpadami komunalnymi w wybranych gminach na terenie województwa małopolskiego","authors":"Magdalena Irla, A. Kowalska","doi":"10.55225/sti.444","DOIUrl":"https://doi.org/10.55225/sti.444","url":null,"abstract":"Gospodarka odpadami komunalnymi w Polsce ewoluuje od lat 90. XX wieku w kierunku zwiększenia recyklingu i minimalizacji składowania odpadów, zgodnie z hierarchią postpowania z odpadami. Każda gmina dostosowuje system gospodarki odpadami do ogólnych wytycznych, tj. aktów prawnych oraz planów, jednak ilość zebranych odpadów na jednego mieszkańca różni się w poszczególnych gminach w zależności od charakteru gminy, świadomości ekologicznej mieszkańców oraz systemu zbiórki odpadów, w tym lokalizacji i organizacji punktu selektywnej zbiórki odpadów. Osiągnięcie wskazanych przez Unię Europejską poziomów recyklingu danych frakcji wymaga dobrej organizacji systemu zbiórki odpadów oraz współpracy gminy z mieszkańcami, którzy mają istotny wpływ na jakość i ilość materiałów wtórnych uzyskanych w procesie segregacji u źródła. W celu porównania ilości zebranych frakcji odpadów oraz osiągnięcia poziomów recyklingu przeanalizowano dokumenty dotyczące gospodarki odpadami komunalnymi za lata 2013–2020 w wybranych siedmiu gminach województwa małopolskiego.","PeriodicalId":7557,"journal":{"name":"African Journal of Science, Technology, Innovation and Development","volume":"61 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90946505","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Polynomial approximation of regular functions of a quaternionic variable","authors":"J. Szczepański","doi":"10.55225/sti.441","DOIUrl":"https://doi.org/10.55225/sti.441","url":null,"abstract":"We consider Bernstein-Walsh-Siciak-type theorems on the polynomial approximation in the case of regular functions of one quaternionic variable and their applications to the uniform approximation and approximation in Lp norms with respect to measures satisfying the Bernstein-Markov condition.","PeriodicalId":7557,"journal":{"name":"African Journal of Science, Technology, Innovation and Development","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89689819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Decomposition rate of two tea types in two different forestry niches","authors":"J. Fyda, Patrycja Żelazo","doi":"10.55225/sti.399","DOIUrl":"https://doi.org/10.55225/sti.399","url":null,"abstract":"Organic matter decomposition is one of the most important processes associated with flow of energy and recirculation of organic matter in natural environments. Using commercially sold tea bags of Lipton Sencha green tea (SGT) and Lipton Ceylon black tea (CBT) their decomposition was studied in mixed and coniferous forest. At both stations 25 bags of each tea were buried for a period of 3 months. After elapsed time, the bags were dug up, dried, and the mean weight loss of organic material for each tea type and ecosystem was calculated. In the mixed forest the average weight loss of tea bags was 46.8% for Sencha and 32.1% for Ceylon tea and respectively 44.6% and 30.6%, in the coniferous forest. Statistical analysis test (ANOVA) revealed a statistically significant difference (p < 0.05) in rate of decomposition between tea types, however the differences between the decomposition of the same type of tea on both type of forest were insignificant.","PeriodicalId":7557,"journal":{"name":"African Journal of Science, Technology, Innovation and Development","volume":"81 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78657204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of ambient temperature on reproduction ofthe red-headed cricket (Gryllus assimilis)","authors":"N. Hermansa, Kamil Kustra, Magdalena Trela, M. Lis","doi":"10.55225/sti.403","DOIUrl":"https://doi.org/10.55225/sti.403","url":null,"abstract":"Red-headed crickets were kept in glass insectariums equipped with drinkers, food containers and peat boxes for laying eggs. In the first stage of the experiment, the insects were divided into three groups, kept at 20°C, 25°C and 29°C, respectively. Three days after placing the crickets in the insectariums, the eggs were counted. In the second stage, the eggs (15 pcs.) were placed in boxes with peat in insectariums and exposed to the same temperatures as the females were kept at 20°C, 25°C and 29°C respectively, and the time in which the larvae hatch in each container was observed.It was found that the thermal conditions of the environment influence the number of eggs laid by female Gryllus assimilis and the length of the embryonic period in red-headed crickets. It is estimated that in the temperature range of 20–29°C, increasing the temperature by 1°C shortens the time needed to hatch the larvae from the eggs by 2 days.","PeriodicalId":7557,"journal":{"name":"African Journal of Science, Technology, Innovation and Development","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76008716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Examining the continued intention of using the Ugunduzi app in farmer-led research of agro-ecological practices among smallholder farmers in selected areas, Tanzania","authors":"Luambano Kihoma, A. Churi, C. Sanga, E. Tisselli","doi":"10.1080/20421338.2023.2180176","DOIUrl":"https://doi.org/10.1080/20421338.2023.2180176","url":null,"abstract":"Farmer-led research of agro-ecological practices could support smallholder farmers in identifying the best-fit practices to improve crop production. A smartphone based app named Ugunduzi was developed purposefully to support farmers in their research activities. The purpose of this study was to investigate smallholder farmers’ intentions to continue using the Ugunduzi app in the Tanzanian districts of Masasi, Mvomero, and Bagamoyo. Cross-sectional research design was used in which qualitative and quantitative data were collected from 60 smallholder farmers who participated in the research and used the Ugunduzi app. Partial least squares structural equation modelling (PLS-SEM) using SmartPLS 3 was employed to analyze the data. The results indicated that the app could continue to be used by smallholder farmers in the study areas due to its usefulness in supporting them to identify best-fit agro-ecological practices in their areas and to have a better future season plan through records kept in the app. The app also showed great potential for increasing agro-ecological knowledge through sharing information. However, a few difficulties were observed, especially in the early stage of using the app due to some processes involved. From the study findings, it was recommended that, due to its effectiveness observed in supporting farmers, the app be promoted by development actors to be used by many smallholder farmers around the study areas to improve crop production. In order to support farmers in reducing the effort required to use the app, it was recommended that key stakeholders provide farmers more training on effective use of the app.","PeriodicalId":7557,"journal":{"name":"African Journal of Science, Technology, Innovation and Development","volume":"26 1","pages":"720 - 730"},"PeriodicalIF":0.0,"publicationDate":"2023-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73101243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}