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Design, modelling, environmental, economic and performance analysis of parabolic trough solar collector (PTC) based cogeneration systems assisted by thermoelectric generators (TEGs)
No full textConcentrating solar power systems (CSP) is a very efficient technology for clean and renewable energy production. It basically works on the principle of focusing the sun's rays with the help of a reflective surface. There are two types of CSP systems: point-focused and line-focused. Point-focused ones are parabolic dish collectors and solar towers. Line-focused ones are parabolic trough collectors (PTCs) and linear Fresnel reflectors. It is possible to reach focus temperatures over 1000 degrees C with point-focused CSPs. Line-focused CSP systems are used to obtain thermal and electrical energy at temperatures below 500 degrees C. Among CSP technologies, PTCs are widely preferred. While it can be used alone, it can also be used in combination with other power generation systems by creating hybrid systems. In this regard, hybrid PTC/TEG energy systems created with thermoelectric generators (TEGs) come to the fore. These systems have higher electrical and thermal efficiency values compared to traditional PTCs. In this study, CSP systems, PTCs, TEGs and hybrid solar energy systems-based PTCs were examined in detail. It is concluded from the study that the total thermal efficiency of PTC-TEG hybrid systems can be enhanced by up to %70 with respect to PTC systems.Turkish Academy of Sciences (TUBA)All contributors who do not meet the criteria for authorship, such as a person who provided purely technical help, writing assistance, or a department chair who provided only general support should be listed in the acknowledgments. Financial and material support should also be recognised in the acknowledgments. Erdem Cuce is grateful to Turkish Academy of Sciences (TUBA) for their financial support to this research
Green Synthesis of Selenium Nanoparticles using Green Coffee Beans: An Optimization Study
No full textIn this study, ultrasonication extraction of some bioactive compounds from green coffee beans was optimized with the response surface method using Box-Behnken experimental design. The best condition was selected as 90.90 W ultrasonic power, 33.63 min sonication time and 30 % solid concentration. The responses obtained under optimum conditions had TPC, DPPH and CUPRAC values identified as 6603.33 +/- 2025.94 ppm GAE, 9638.31 +/- 372.17 ppm TE and 98.83 mmol, respectively. Microwave-assisted selenium nanoparticle production was carried out using the extract obtained under optimized conditions. The produced selenium nanoparticles showed absorbance between 350-400 nm. The surface morphology and size of the nanoparticles were determined by transmission electron microscopy (TEM) and spherical nanoparticles of about 100 nm were produced. Functional groups affecting the reduction were determined by FTIR analysis. In addition, the produced selenium nanoparticles had amorphous (non-uniform) structure and could maintain their stability at high temperatures. imag
The effect of ethnomathematics activities on 6th grade students' attitudes to problem solving
No full textLisansüstü Eğitim Enstitüsü, Matematik ve Fen Bilimleri Eğitimi Ana Bilim Dalı, Matematik Eğitimi Bilim DalıAraştırmanın amacı etnomatematik etkinliklerinin 6. sınıf öğrencilerinin problem çözme tutumlarına etkisini incelemek ve etnomatematiğin dahil edildiği problem çözme etkinliklerine yönelik öğrenci görüşlerini belirlemektir. 2023-2024 eğitim öğretim yılı güz döneminde Samsun ili Ayvacık ilçesinde bir ortaokulda öğrenim gören 6. sınıf öğrencilerinden amaçlı örnekleme yöntemi ile seçilen 40 öğrenci araştırmanın örneklemini oluşturmaktadır. Bu araştırmada nitel ve nicel verilerin birlikte kullanılarak yorumlanmasına dayalı karma araştırma modeli kullanılmıştır. Karma araştırma yönteminin kullanılmasının nedeni nicel araştırma yöntemi ile nitel araştırma yönteminin birlikte daha iyi açıklayabildiği problemlere çözüm bulmaktır. Bu araştırmada etnomatematik etkinliklerinin problem çözme tutumuna etkisini incelemede nitel ve nicel verilerin birbirini destekleme durumlarından faydalanmak amacıyla karma araştırma deseni olarak açıklayıcı desen kullanılmıştır. Araştırmanın nitel kısmında veri toplama aracı olarak, etnomatematik etkinliklerinin matematik öğretiminde kullanılmasına yönelik öğrenci görüşlerini irdeleyen ve araştırmacı tarafından hazırlanan görüşme formu kullanılmıştır. Nicel veriler ise Matematik Problemi Çözme Tutum Ölçeği (MPÇTÖ) yoluyla toplanmıştır. Veri toplama süreci deney ve kontrol grubu öğrencilerine ön test olarak MPÇTÖ'nin uygulanmasıyla başlamıştır. Ardından haftada iki saat olacak şekilde 3 hafta boyunca etnomatematik etkinlikleri deney grubu öğrencilerine uygulanmış, kontrol grubu ise standart öğretime devam etmiştir. Uygulama sonunda MPÇTÖ son test olarak deney ve kontrol gruplarına tekrar uygulanmış ve deney grubu öğrencilerinden seçilen gönüllü 10 öğrenci ile görüşmeler yapılmıştır. MPÇTÖ'nden elde edilen veriler SPSS paket programına aktarılarak bağımsız gruplar t-testi ve bağımlı örneklemler t-testi ile analiz gerçekleştirilmiştir. Nitel veriler ise içerik analizi yoluyla analiz edilmiştir. Araştırma sonucunda deney ve kontrol grubunun ön test puanları arasında anlamlı bir fark görülmezken, son test puanları arasında anlamlı bir fark görülmüştür. Öğrenci görüşmelerinden elde edilen veriler bu bulguları destekler niteliktedir. Öğrenciler görüş olarak etnomatematik etkinlikleriyle problem çözmeye dair duygu, düşünce ve yaklaşımlarında olumlu değişimler bildirmişlerdir. Elde edilen bu bulgular bağlamında etnomatematik etkinliklerinin 6. Sınıf öğrencilerinin problem çözme tutumlarına olumlu bir etkisi olduğu söylenebilir. Bu etkilerin içeriği ve nedenleri elde edilen nitel veriler ışığında tartışılmıştır.The aim of the study is to examine the effects of ethnomathematics activities on the problem-solving attitudes of 6th-grade students and to determine student opinions on problem-solving activities that incorporate ethnomathematics. 40 6th grade students studying in a secondary school in Ayvacık district of Samsun province in the fall semester of the 2023-2024 academic year, selected by purposeful sampling method, constitute the sample of the research. In this research, a mixed research model was used based on the interpretation of qualitative and quantitative data together. The reason for using the mixed research method is to find solutions to problems that are better explained by combining quantitative and qualitative research methods. In this study, an explanatory design was employed as a mixed research method to examine the impact of ethnomathematics activities on problem-solving attitudes, leveraging the complementary nature of qualitative and quantitative data. As a data collection tool for the qualitative data of the study, an interview form prepared by the researcher, which examining students' opinions on the use of applied ethnomathematics activities in mathematics teaching, was used. Quantitative data were collected using the Mathematics Problem-Solving Attitude Scale (MPSAS). The data collection process started with the application of MPSS to the students in the experimental and control groups as a pre-test. Ethnomathematics activities were applied to the students of the experimental group for two hours a week during three weeks and the control group continued their standard education. At the end of the application, MPSAS was applied to the experimental and control group students as a post test, and 10 volunteer students selected from the experimental group were interviewed. The data obtained from MPSAS were transferred to the SPSS package program and analyzed with independent samples t-test and dependent samples t-test. C Analysis of qualitative data was done via content analysis. As a result of the research, while there was no significant difference between the pre-test scores of the experimental and control group students, there was a significant difference between the post-test scores. Data obtained from student interviews support these findings. Students reported positive changes in their feelings, thoughts, and approaches to problem-solving through ethnomathematics activities. In this context, it can be said that ethnomathematics activities have a positive impact on the problem-solving attitudes of 6th-grade students. The content and reasons for these effects were discussed in light of the qualitative data obtained
Investigation of the effect of added vanadium element in casting of Etial 177 aluminum alloys
No full textLisansüstü Eğitim Enstitüsü, Makine Mühendisliği Teknolojileri Ana Bilim Dalı, Makine Mühendisliği Bilim DalıAlüminyum döküm endüstrisinde akıcılık ve mekanik özelliklerin artırılması amacıyla alüminyum alaşımına vanadyum (V) ilavesi önem arz etmektedir. Bu kapsamda yapılan bu çalışmada, Etial 177 alaşımına vanadyum elementi ilave edilerek sıvı metal temizliği, akıcılık ve mekanik özelliklere etkisi deneysel çalışmalarla incelenmiştir. Döküm işlemlerinde kokil kalıba döküm yöntemi kullanılmıştır. Deneylerde Etial 177 standardı alüminyum alaşımına farklı oranlarda V ilavesinin alaşımın özelliklerine etkileri incelenmiştir. Çalışmada V ilave miktarı %0,03, %0,05 ve %0,1 V etki edecek şekilde ve numune döküm işlemlerinde farkın tespit edilebilmesi için ilave edilmeyen ETİAL 177 referans numuneler üretilmiştir. Dökümlerde vakum altında katılaştırma, K-mold kalıbı, mekanik test kalıbı, değişen kesitlere sahip 4 kanallı akıcılık kalıbı ve spiral akıcılık kalıbı kullanılmıştır. Deney alaşımlarının dökümlerinden alınan numunelerinde VAK numunelerinin yoğunluk ölçümlerinde %0,5'in altında gözenek ve K mold kalıplarında 1'in altında K değerine sahip olduğu tespit edilmiştir. İlavesiz ETİAL 177 dökümde %2,76 olan uzama miktarı, artan V miktarı ile artış göstermiş ve %1 V ilavesinde maksimum %7,61'lere varan değere ulaşmıştır. Çekme gerilmesi değerlerinin ilavesiz ETİAL 177 dökümlerde 137 MPa, %0,03 V ilavesinde 159 MPa, %0,05 V ilavesinde 168 MPa ve %0,1 V ilaveli dökümlerde de 185 MPa değerlerine kadar artış gösterdiği gözlenmiştir.In the aluminum casting industry, the addition of vanadium (V) to the aluminum alloy is important in order to increase fluidity and mechanical properties. In this context, in this study, vanadium element was added to Etial 177 alloy and its effects on liquid metal cleanliness, fluidity and mechanical properties were examined through experimental studies. In the casting process, the permanent mold casting method was used. In the experiments, the effects of adding different amounts of V to the Etial 177 standard aluminum alloy on the properties of the alloy were examined. In the study, ETİAL 177 reference samples were produced with the V addition amount to be 0.03%, 0.05% and 0.1% V, and in order to detect the difference in the sample casting processes. Solidification under vacuum, K-mold mold, mechanical test mold, 4-channel flow mold with varying cross sections and spiral flow mold were used in the castings. In the samples taken from the castings of the test alloys, it was determined that VAK samples had pores below 0.5% in density measurements and K values below 1 in K molds. The elongation amount, which was 2.76% in ETIAL 177 casting without addition, increased with increasing V amount and reached a maximum value of 7.61% with 1% V addition. It was observed that the tensile stress values increased up to 137 MPa in ETİAL 177 castings without addition, 159 MPa with 0.03% V addition, 168 MPa with 0.05% V addition and 185 MPa in castings with 0.1% V addition
Türk Yönetim Kültürü Araştırmalarına Organizasyonel Bakış
No full textTürk kültürü araştırmaları, farklı açılardan değerlendirilebilir. Organizasyonda çalışanlar iş faaliyetlerini yerine getirirken, hem yönetim mekanizmasından hem de kültürel değerlerden etkilenir. Bu açıdan Türk yönetim kültürüne organizasyonel bakış, literatüre yeni bir katkı sağlayabilir. Araştırmanın amacı yönetim açısından organizasyondaki iş faaliyetlerinin yerine getirilmesinde, Türk kültürünün etkilerini incelemektedir. Amaç doğrultusunda literatürde yer alan Türk yönetim kültürü araştırmalarına odaklanılmıştır. Araştırmada Web of Science’de yer alan Türk yönetim kültürü makaleleri incelenmiştir. Araştırmanın analiz yöntemi, R programı ve bibliyometrik analizlerden oluşmuştur. Analizde vurgulanan anahtar kelimelere ve kelimelerin birbirleri ile ilişkilerine yer verilmiştir. Türk yönetim kültürü araştırmaları 17.04.2023 tarihinde analiz edilmiştir. Analiz sonucunda literatürde toplam 490 makalenin olduğu tespit edilmiştir. Konuya ilişkin makalelerin 1993-2023 yıllarını kapsadığı, toplam 1369 yazarın araştırma yürüttüğü görülmüştür. Araştırmaların yıllık büyüme oranının %2.34 olduğu, en fazla atıfın 2011 yılında ve yayınlanan makalenin ise 2020 yılında gerçekleştirildiği gözlemlenmiştir. Sonuç olarak yazarların araştırmalarında en fazla vurgu yaptığı kelimeler; Türkiye, kültür, organizasyon kültürü, yönetim, liderlik, iş tatmini, kolektivizm, yenilik, bilgi yönetimi ve kültürlerarası olarak sıralanmıştır. Analiz sonucunda Türkiye ve kültür kavramlarının güçlü ilişkilere sahip olduğu anlaşılmıştır. Araştırmada bu ilişkiye ek olarak yönetim, liderlik, değişim, yükseköğretim, organizasyon kültürü, Türk kültürü ve rekabet eden değerler kelimelerinin de birbirleri ile güçlü ilişkilere sahip olduğu görülmüştür
Investigation of the cognitive development of secondary school 5th, 6th, 7th and 8th grade students related to environmental problems, ecological footprint and water footprint concepts
No full textLisansüstü Eğitim Enstitüsü, Matematik ve Fen Bilimleri Ana Bilim DalıBu çalışmada; ortaokul öğrencilerinin çevre sorunları, ekolojik ayak izi ve su ayak izi kavramlarının bilişsel gelişimlerinin incelenmesi hedeflenmiştir. Çalışmada, nicel araştırma yöntemlerinden gelişimsel araştırma yöntemi kullanılmıştır. 5.sınıf kademesinden 16, 6. sınıf kademesinden 16, 7. sınıf kademesinden 27 ve 8. sınıf kademesinden 21 olmak üzere toplam 80 öğrenci araştırmaya katılmıştır. Veri toplama aracı olarak; çevre sorunlarına, ekolojik ve su ayak izi hakkında senaryolandırılmış açık uçlu sorular ve yarı yapılandırılmış görüşme kullanılmıştır. Çalışmanın birinci aşamasında öğrencilere çevre sorunları, ekolojik ve su ayak izi başlıkları altında senaryolarla hazırlanmış açık uçlu sorular yöneltilmiştir. Verilen yanıtlar literatürdeki tanımlara özdeş bilimsel olarak ifade edilip edilmemesine göre kategorize edilmiştir. Verilen yanıtlara temalar ve kodlar tayin ederek frekansları belirlenmiştir. "Çevre Sorunları" başlığı altında su kirliliği, toprak kirliliği, hava kirliliği kavramları hakkında sorulan soruları 5., 6., 7. ve 8. sınıf öğrencilerinin büyük bir kısmının cevaplayabildikleri tespit edilmiştir. "Ekolojik Ayak İzi" başlığı altında sorulan sorularda öğrencilerin büyük bir kısmının ekolojik ayak izinin bilimsel tanımını yapamadıkları tespit edilmiştir. "Su Ayak İzi" başlığı altında sorulan sorularda öğrencilerin hiç birinin su ayak izinin tanımını bilimsel olarak yapamadıkları görülmüştür. Araştırmanın ikinci aşamasında ise senaryolarla oluşturulmuş açık uçlu sorulara paralel olarak hazırlanmış yarı yapılandırılmış görüşme yapılmıştır. 5., 6., 7. ve 8. sınıflardan beşer öğrenci seçilmiş, toplam 20 öğrenci ile yüz yüze yarı yapılandırılmış görüşme yapılmıştır. Öğrencilerin çevre sorunları hakkında bilgi sahibi oldukları ancak ekolojik ve su ayak izini bilimsel olarak tanımlayamadıkları tespit edilmiştir. Öğrencilerin ekolojik ayak izi ve su ayak izi kavramlarını tanımlamada yeterli olmadıkları görülmüştür. Üst sınıflara geçtikçe bilimsel kelime kullanımı sayısının artışı gözlenmemiştir.This research aims to examine the cognitive development of secondary school 5th, 6th, 7th and 8th grade students' concepts of environmental problems, ecological footprint and water footprint. Developmental research method, one of the quantitative research methods, was used in the study. A total of 80 students, 16 from the 5th grade, 16 from the 6th grade, from the 7th grade and 21 from the 8th grade, participated in the research. Scripted open-ended questions and a semi-structured interview form about environmental problems, ecological footprint and water footprint concepts were used as data collection tools. In the first stage of the study, open-ended questions prepared with scenarios were asked to the students under the headings of environmental problems, ecological footprint and water footprint. The answers given were categorized according to whether they were scientifically expressed or not, identical to the definitions in the literature. Frequencies were determined by assigning themes and codes to the answers given. It has been determined that most of the 5th, 6th, 7th and 8th grade students can answer the questions asked about the concepts of water pollution, soil pollution and air pollution under the title of environmental problems. In the questions asked under the heading of ecological footprint, it was determined that most of the students could not define the ecological footprint. In the questions asked under the title of water footprint, it was seen that none of the students could scientifically define the water footprint. In the second stage of the research, a semi-structured interview prepared in parallel with open-ended questions created with scenarios was conducted. five students from each of the 5th, 6th, 7th and 8th grades were selected, and a face-to-face semi-structured interview was conducted with a total of 20 students. It was determined that students were knowledgeable about environmental problems, but could not define the concepts of ecological footprint and water footprint. It was observed that students were not sufficient in defining the concepts of ecological footprint and water footprint. There was no increase in the number of scientific word usage as we moved to upper grades
Analysis of an actively controlled composite box manipulator without external actuator
No full textThis study focuses on active vibration control for a single-link composite box manipulator by using a single actuator for driving and control actions. Model extraction and system identification techniques are studied to obtain mathematical models of the manipulator. The state space model is extracted from the finite element model using modal analysis conducted in ANSYS, while the system identification approach is an experimental modeling method using the input and output signals of the system. The input signals are defined as triangular and trapezoidal motion profiles, while the output signals are the acceleration signals of the manipulator. Proportional derivative and positive position feedback controllers are implemented on the obtained mathematical models to reduce residual vibrations. The simulation results are successfully verified by experiments, and uncontrolled/controlled results are evaluated with reduction rates.Dokuz Eylul University Research Fund [2019.KB.FEN.023, 2020.KB.FEN.009]The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The authors express their special thanks to Dokuz Eylul University Research Fund for financial support to two separate research projects with the numbers 2019.KB.FEN.023 and 2020.KB.FEN.009. Experimental systems were established with financial support from these projects
A case study comparing seismic retrofitting techniques for a historically significant masonry building's minaret
No full textHistorical masonry structures are extremely susceptible to earthquakes due to their characteristic features. Seismic performance and corresponding damage patterns vary between these buildings. Even though the main structure was undamaged, many minarets suffered damage or collapsed due to the transmission of large forces from the main mass to the minaret and the abrupt changes in cross-section due to the geometry of the minaret. This study uses an ancient masonry mosque as a case study, whose minaret and main building are constructed as a single structure. The mosque's minaret under seismic excitation is the focus of this study. The adopted model is called Alaeddin Bey Mosque in Mus,, T & uuml;rkiye. The seismic performance assessment of the minaret, considering various retrofitting options, is mainly based on four critical parameters: base shear, acceleration, displacement, and maximum tensile forces in all three dimensions. The analyzed retrofitting methods include base isolation located in the basement of the mosque, viscous dampers placed only in the upper part of the minaret, Carbon Fiber-Reinforced Polymer fabric fitted to only the minaret, and steel plates applied to only the minaret. Representative structural models of the mosque have been modelled with SAP2000 software. The main novelty of this study is the use of viscous dampers in the minaret. It is the first time a design methodology has been introduced for viscous damper applications in minarets. This methodology aims to prevent local damage to the minaret due to the forces generated by the dampers, while also considering the constraints of limited internal space within the minaret. The finding of this study shows that viscous damper application yields significantly better results compared to the application of Carbon Fiber-Reinforced Polymer fabric and steel plates. However, although base isolation reduces the tensile stress values throughout the entire mosque to levels well below the material's strength, viscous damper application in the minaret significantly reduces tensile stresses only in the minaret. As a result, viscous dampers are recommended for damage reduction in the minaret only. Otherwise, base isolation should be considered for reducing stress values throughout the entire mosque including the minaret. This study contributes towards the development of new seismic retrofitting methods for historic masonry buildings 'minaret
Organizational Overview of Maslow and Management Research
No full textMaslow's theory of motivation or hierarchy of needs; has been the subject of much research on a global scale in the physiological, psychological, and sociological framework. This situation, especially in terms of organizations (public or private), concerns both the employees and the management mechanism. Maslow and management generally reveal the theoretical and relational results in the policies applied in organizations. In the literature, studies in which studies carried out in Maslow and management research are systematically expressed quite limited. The research was carried out using the R program and bibliometric analysis applications with the help of the WoS database on Maslow and management research. As a result of the research analysis, the most emphasized keywords by the authors; motivation, Maslow, Maslow's hierarchy of needs, needs hierarchy, needs, management, self-actualization, leadership, psychology, innovation, sustainability, job satisfaction, China, satisfaction, commitment, human psychology, human needs, Covid-19, management theory, personality division, hierarchy, Maslow's theory, performance, spirituality, sustainable development, theory, Abraham Maslow, creativity, productivity, quality life, rural, safety, culture, values, need, human resource management, well-being, workplace, academic libraries cold war, behavior, cognition, demand, and development. As a result of the analysis, it was understood that the concepts of management, performance, work, job satisfaction, personality, self, attitudes, environment, healthcare, perceptions, participation, antecedents, and science have strong relationships together. The results obtained in Maslow and management research have revealed that organizational activities are also effective in addition to the needs and psychological aspects of individuals. © 2024 The Authors. Turkish Journal of Counseling Psychology and Guidance is published by Turkish Psychological Counselling and Guidance Association
Machine learning driven optimization and parameter selection of multi-surface HTS Maglev
No full textThis research aims to tackle the challenges posed by precise force measurement for high temperature superconducting (HTS) Maglev systems, including mechanical constraints, step motor limitations, and sensor resolutions. For this aim, six machine learning (ML) models namely Support Vector Machine (SVM), Gaussian Process Regression (GPR), Extreme Gradient Boosting (XGB), Long Short-Term Memory (LSTM), Extreme Machine Learning (EML), and Convolutional Neural Network (CNN) were developed to predict levitation force (Fz) and lateral force (Fx) based on process parameters including permanent magnet width (PMW), field cooling height (FCH), the movement in the z-axis (vertical distance), and the movement in the x-axis (lateral distance). Among six ML models, CNN emerged as the most accurate model, demonstrating smaller root mean square deviation (RMSD) without compromising correlation coefficients. Furthermore, an innovative process window approach was introduced to select process parameters that simultaneously meet the minimum value of Fz and maximum value of Fx, named beta 1 and beta 2, set at 90 N and 0 N, respectively. Within this window, PMW of 30 mm and z values less than 10 mm were found to be consistent for all FCH and x values. The novelty of this study is to formulate the optimisation problem in HTS Maglev using the developed ML model by addressing two specific objectives one of which focuses on maximizing Fz while ensuring Fx remains within a defined tolerance (beta 3), representing the minimum allowable ratio of the levitation force to the total force, and the second problem aims to maximize Fz while obtaining zero Fx. The optimum PMW, FCH, x, and z values were obtained at 30 mm, 30 mm, 4 mm and 5 mm, corresponding to Fz and Fx values of 224.2 N and -53.8 N for option 1. As for option 2, the process parameters were obtained as 28.6 mm, 25.9 mm, 0 mm, and 5 mm, corresponding to Fz and Fx values of 194.2 N and 0 N. It was obtained both experimentally and by the optimization that Fz reaches close its maximum as the Fx gains attractive character. Hence, it is expected that the outcomes of this study will significantly benefit the design of HTS Maglev systems and find valuable applications across various transportation engineering projects.Scientific and Technological Research Council of Turkiye (TUBITAK) [122F432, 118F426]This work was supported by the Scientific and Technological Research Council of Turkiye (TUBITAK), with project numbers of 122F432 and 118F426