DSpace@ATÜ (Adana Alparslan Türkeş Bilim ve Teknoloji Universiti)
Not a member yet
3463 research outputs found
Sort by
Mısır yaprak hastalıklarının tespitinde yapay zeka modellerinin etkinliğinin saptanması
No full textLisansüstü Eğitim Enstitüsü, Yazılım Mühendisliği Ana Bilim DalıMaize is a strategic agricultural product that is of great importance as a source of food and feed; however, leaf diseases cause significant losses in production. The time-consuming nature and high error rate of traditional diagnostic methods have accelerated the search for innovative solutions in agriculture. In this study, the automatic diagnosis of Maize leaf diseases using Convolutional Neural Networks (CNN) was investigated. The dataset obtained from Kaggle, containing images of diseased and healthy leaves, was divided into 80% training, 10% validation, and 10% test sets to compare the performance of different CNN models. The ConvNeXt model demonstrated the highest performance with a 96% accuracy rate, followed by DenseNet with 95% and EfficientNet with 94% accuracy rates. MobileNet stood out with a 92% accuracy rate and low computational cost. The results show that modern CNN architectures provide higher accuracy and efficiency compared to older models. The use of deep learning technologies in agricultural applications holds significant potential in the agricultural sector by offering effective and reliable solutions for disease diagnosis.Mısır, stratejik bir tarım ürünü olarak gıda ve yem kaynağı açısından büyük öneme sahiptir; ancak yaprak hastalıkları, üretimde önemli kayıplara neden olmaktadır. Geleneksel teşhis yöntemlerinin zaman alıcı ve hata oranı yüksek olması, tarımda yenilikçi çözümler arayışını hızlandırmıştır. Bu çalışmada, Evrişimsel Sinir Ağları (CNN) kullanılarak mısır yaprak hastalıklarının otomatik teşhisi incelenmiştir. Kaggle'dan alınan ve hastalıklı ile sağlıklı yaprak görüntülerini içeren veri seti, %80 eğitim, %10 Validation ve %10 Test oranında ayrılarak farklı CNN modellerinin performansları karşılaştırılmıştır. ConvNeXt modeli %96 doğruluk oranıyla en yüksek performansı sergilerken, DenseNet %95 ve EfficientNet %94 doğruluk oranları ile onu takip etmiştir. MobileNet, %92 doğruluk oranı ve düşük hesaplama maliyetiyle öne çıkmıştır. Sonuçlar, modern CNN mimarilerinin eski nesil modellere kıyasla daha yüksek doğruluk ve verim sağladığını göstermektedir. Derin öğrenme teknolojilerinin tarımsal uygulamalarda kullanımı, hastalık teşhisinde etkin ve güvenilir çözümler sunarak tarım sektöründe önemli bir potansiyel taşımaktadır
Askerı̇ gemı̇ler ı̇çı̇n şaft jeneratörünün tasarımı, optı̇mı̇zasyonu ve enerjı̇ verı̇mlı̇lı̇ğı̇ analı̇zi
No full textLisansüstü Eğitim Enstitüsü, Elektrik-Elektronik Mühendisliği Ana Bilim DalıThe maritime sector has become an increasingly significant domain, playing a critical role in global trade. In an effort to mitigate the emissions resulting from the burgeoning volume of maritime trade, the International Maritime Organisation (IMO) has promulgated a series of regulations. In order to comply with these regulations and improve energy efficiency, companies in the sector have concentrated on upgrading existing systems and improving operational processes. The configuration of energy systems on board naval ships is subject to variation depending on operational requirements, ship structure and the geographical regions where the ship will operate. In this context, a comparison of the technical, performance and energy efficiency impacts of 50 Hz and 60 Hz frequency systems used on ships is required. This thesis presents a comprehensive discussion of the role of shaft generators on naval ships and provides a detailed analysis of their impact on power systems, focusing on frequency, voltage characteristics and number of poles. The study goes on to analyse the contribution of shaft generators in meeting mechanical and electrical energy requirements from the perspective of system optimisation and energy efficiency. The analyses performed in ANSYS/Maxwell and Matlab/Simulink demonstrate that the selection of optimal values for naval ships is contingent on the requirements and demands of the specific system in question.Denizcilik sektörü, küresel ticarette kritik bir rol oynayan ve önemi giderek artan bir alan haline gelmiştir. Deniz ticaretinin artan hacminden kaynaklanan emisyonları azaltmak amacıyla Uluslararası Denizcilik Örgütü (IMO) bir dizi yönetmelik yayınlamıştır. Bu düzenlemelere uymak ve enerji verimliliğini artırmak için sektördeki şirketler mevcut sistemlerin iyileştirilmesine ve operasyonel süreçlerin geliştirilmesine odaklanmıştır. Askeri gemilerdeki enerji sistemlerinin konfigürasyonu operasyonel gerekliliklere, gemi yapısına ve geminin faaliyet göstereceği coğrafi bölgelere bağlı olarak değişkenlik göstermektedir. Bu bağlamda, gemilerde kullanılan 50 Hz ve 60 Hz frekanslı sistemlerin teknik, performans ve enerji verimliliği üzerindeki etkilerinin karşılaştırmalı bir analizine ihtiyaç duyulmaktadır. Bu tez, şaft jeneratörlerinin askeri gemilerdeki rolüne ilişkin kapsamlı bir inceleme sunmakta ve frekans, gerilim özellikleri ve kutup sayısına odaklanarak güç sistemleri üzerindeki etkilerinin ayrıntılı bir analizini sağlamaktadır. Çalışma, şaft jeneratörlerinin mekanik ve elektrik enerjisi gereksinimlerini karşılamadaki katkısını sistem optimizasyonu ve enerji verimliliği perspektifinden analiz etmeye devam etmektedir. ANSYS/Maxwell ve Matlab/Simulink'te gerçekleştirilen analizler, askeri gemiler için optimum değerlerin seçiminin söz konusu sistemin gereksinimlerine ve taleplerine bağlı olduğunu göstermektedir
From Boom to Bust: Unravelling the Global Tech Layoffs Phenomenon
No full textThe purpose of this chapter is to provide an extensive overview of the underlying dynamics and socio-economic effects and consequences of the post-pandemic global tech layoffs while contributing to the literature by bringing forward pressing issues, like ‘backdoor layoffs’, and comprehensive insights while identifying the opportunities and challenges. Due to the multi-faceted nature of the phenomenon, an interdisciplinary approach is being employed, combining the empirical findings from various sources, including interviews, social media, and databases, into theoretical frameworks and real-world case studies. A multi-level analysis of the global tech layoffs is conducted through these case studies. As a result, this study reveals the root causes from the top and uncovers various challenges, like economic downturns, uncertainties, corporate strategies, and unethical practices. Moreover, companies are expected to follow the strategies of successful peers, and in the case of workforce reduction, small and medium enterprises follow different trajectories from each other but homogenous trends within their peer groups. This finding indicates that the global tech layoff has a multi-level nature, and each level has diverse needs and expectations to be addressed. At the social level, this chapter defines backdoor layoffs term and delves into their consequences that can exacerbate inequalities, especially for discrimination groups, and create barriers to re-employment. Addressing unethical backdoor layoff practices and creating a more sustainable tech labor market requires a wider participation of stakeholders. Finally, this chapter sheds light on the gaps in the mass layoffs scholarship, offering theoretical frameworks, definitions, and empirical evidence to expand the literature. © 2025 selection and editorial matter, Shilpa Deo and Fatma Feyza Gündüz; individual chapters, the contributors
Estetik Bilim Tarihini Nasıl Etkiledi? Bilimsel Bilgi ve Güzel Arasındaki İlişki Üzerine
No full textGenel bir değerlendirmede, bilim ve estetik arasında belirgin bir ayrım olduğu kabul edilir. Bunun nedeni, estetiğin öznel bir kavram olduğu düşünülen güzeli konu edinmesidir. Bilim ise nesnel bilgiye ulaşma iddiasındadır. Güzel olanın niteliksel özelliği ile ilgilenen estetik ile bilgi nesnelerinin niceliksel (ölçülebilir) yönlerini araştıran bilim pek bağdaştırılmaz. Bu çalışmada, bilim ve estetik arasında oldukça yakın bir ilişki olduğunu iddia ediyorum. Bilimsel ürün (icat, kuram, denklem vb.) ile sanat eseri arasında nasıl bir ilişki olduğunu araştırıyorum. Bilim tarihindeki kimi örneklerle, keşif esnasında ve hipotez/kuram oluştururken, bilim insanlarının çoğu zaman estetik kaygı ile hareket ettiklerini göstermeye çalışıyorum. Bu kaygı nedeniyle, evren çoğu zaman olduğu gibi değil, olması beklendiği gibi tasvir edilmiştir. Bilim tarihinde estetik etki o denli iz bırakmıştır ki, bazen bilimsel gelişimi hızlandırılmış, bazen de gelişimin önünde bir engel olarak durmuştur
Damgalanma bı lı ncı nı n karı yer tatmı nı üzerı ndekı etkı sı nde benlik saygısı ve ı ş yerı yalnızlığının aracılık rollerı : Kadın bankacılar üzerı ne ampı rı k bı r çalışma
No full textLisansüstü Eğitim Enstitüsü, İşletme Ana Bilim DalıBu çalışmanın amacı damgalanma bilinci, iş yeri yalnızlığı, kariyer tatmini ile benlik saygısı arasındaki doğrudan ve dolaylı ilişkileri ortaya koymaktır. Bu amaç doğrultusunda konu ile ilgili yapılmış olan önceki çalışmalar incelenerek araştırma modeli oluşturulmuş ve araştırma hipotezleri geliştirilmiştir. Çalışma kapsamında geliştirilen bu hipotezlerin sınanması amacıyla anket veri toplama yöntemi kullanılmıştır. Bu doğrultuda, Türkiye'deki özel ve kamu bankalarında görev yapan 363 kadın çalışana anket uygulanmıştır. Araştırma bulguları, çalışmanın amacına uygun şekilde keşfedici faktör analizi, korelasyon analizi ve hiyerarşik regresyon analizi kullanılarak elde edilmiştir. Yapılan analizler sonucu elde edilen bulgular araştırma hipotezlerini büyük ölçüde desteklemektedir. Buna göre, damgalanma bilincinin iş yeri yalnızlığı, kariyer tatmini ve benlik saygısı gibi çalışan tutumlarını yordadığı korelasyon analizi sonucu ortaya konulmuştur. Aynı şekilde, iş yeri yalnızlığı ve benlik saygısının da kariyer tatmininin anlamlı birer yordayıcısı olduğu tespit edilmiştir. Ayrıca yapılan hiyerarşik regresyon analizi sonucunda, damgalanma bilinci ile kariyer tatmini arasındaki ilişkide iş yeri yalnızlığı ve benlik saygısının kısmi aracı rolü olduğuna dair bulgular elde edilmiştir. Son olarak, elde edilen bu sonuçlar konu ile ilgili literatürde yer alan çalışmalar bağlamında tartışılarak, gerek örgütler gerekse gelecekte yapılacak çalışmalar için bir takım öneriler sunulmuştur.The aim of this study is to reveal the direct and indirect relationships between stigma consciousness, workplace loneliness, career satisfaction and self-esteem. In line with this purpose, a research model has been established examining previous studies on the subject and research hypotheses have been developed. In order to test these hypotheses developed in the study, questionnaire data collection method was used. A questionnaire has been applied to 363 women employees working in private and public banks in Turkey in this direction. The research findings were obtained by using exploratory factor analysis, correlation analysis and hierarchical regression analysis in line with the purpose of the study. Findings obtained as a result of the analyses support research hypotheses to a large extent. Accordingly, the result of correlation analysis has revealed that stigma consciousness predicted employee attitudes such as workplace loneliness, career satisfaction and self-esteem. Similarly, workplace loneliness and self-esteem were found to be significant predictors of career satisfaction. In addition, as a result of the hierarchical regression analysis, findings were obtained indicating that workplace loneliness and self-esteem has a partial intermediatary role in the relationship between stigma consciousness and career satisfaction. Finally, these results were discussed in the context of the studies in the relevant literature and several suggestions were made for both organizations and future studies
High-Gain Multiport DC-DC Converter Topologies for Renewable Energy Applications: A Comprehensive Review
No full textRenewable energy sources have emerged as favorable alternatives for meeting ever-increasing global energy demand. To harness the maximum efficiency from renewable sources, dc-dc converters play a crucial role. While the design of dc-dc converters varies depending on specific application, certain features such as multiport capability and high gain are generally desirable. Multiport structures offer advantages such as compactness and cost reduction, allowing for the efficient integration of various energy sources, storage units, and loads. On the other hand, high gain characteristics enable the step-up of output voltages from renewable energy sources to usable levels. In recent years, numerous converter topologies proposed to address these requirements and enhance overall system performance. This study aims to assist and provide guidance to researchers in the field by reviewing and comparing the most recent advancements in the design and implementation of multiport high-gain dc-dc converters for renewable energy applications. Through a comprehensive analysis of the existing literature, the primary objective of this study is to facilitate knowledge transfer, identify research gaps, and inspire future research endeavors in this domain. By synthesizing the knowledge gained from these studies, researchers can contribute to ongoing advancement of multiport converter technology in the context of renewable energy applications
Boron modified Ag3PO4 powders for UV and visible light photocatalytic degradation of various dyes
No full textPure and boron modified Ag3PO4 powders with different boron contents (0-5 wt.%) were prepared. XRD, ATR-FTIR, XPS, SEM-EDX, UV-Vis DRS and PL analyses were conducted for the characterization of the prepared powders. Characterization studies indicated the reduction in the band gap energy, the presence of boron and no change in the morphology due to boron modification. The results of photocatalytic experiments showed that boron modification increased the activity of Ag3PO4. The UV light dye degradation efficiency increased from 63% to 84% for methyl orange (MO) and from 41% to 65% for methyl red by 3% boron modification. The reaction rate constant for MO increased by a factor of 1.7. Under visible light, the activity was similarly enhanced by boron modification. The photocatalytic degradation efficiency increased from 31% to 58% and the reaction rate constant increased by a factor of 2.3 by boron modification for MO under low intensity visible light. These results showed that boron modification enhanced the photocatalytic dye degradation activity of Ag3PO4 under both UV and visible light. This enhancement was attributed to the decrease in the band gap energy and the increase in the interaction of the dye molecules with the photocatalyst surface through boron species. [GRAPHICS
Thurston's asymmetric metric on the space of singular flat metrics with a fixed quadrangulation
No full textConsider a compact surface equipped with a fixed quadrangulation. One may identify each quadrangle on the surface with a Euclidean rectangle to obtain a singular flat metric on the surface with conical singularities. We call such a singular flat metric a rectangular structure. We study a metric on the space of unit area rectangular structures which is analogous to Thurston's asymmetric metric on the Teichm & uuml;ller space of a surface of finite type. We prove that the distance between two rectangular structures is equal to the logarithm of the maximum of ratios of edges of these rectangular structures. We give a sufficient condition for a path between two points of the this Teichm & uuml;ller space to be geodesic and we prove that any two points of this space can be joined by a geodesic. We also prove that this metric is Finsler and give a formula for the infinitesimal weak norm on the tangent space of each point. We identify the space of unit area rectangular structures with a submanifold of a Euclidean space and we show that the subspace topology and the topology induced by the metric we introduced coincide. We show that the space of unit area rectangular structures on a surface with a fixed quadrangulation is in general not complete.TUEBIdot;TAK [221N171]; CNRS-TUEBIdot;TAK; Teichmueller Theory of Hyperbolicand Flat Surfaces with Conical Singularities [221N171]The first named author is financially supported by TUB & Idot;TAK. Both authors are supported by CNRS-TUB & Idot;TAK joint project Teichmuller Theory of Hyperbolic and Flat Surfaces with Conical Singularities No. 221N171
A Financing Constraints Paradox? Internal Finance and Capital Structure Link for Tourism Firms: Asian Emerging Market evidence
No full textThe aim of the study is to investigate the relationship between the internal financial and capital structure of an organization in the travel and tourism sector. The study shows how financial constraints on tourism companies affect their ability to finance themselves. The study also shows a relationship between tax shielding and financial leverage. This study analyzes panel data collected over a 21 year period, from 1998 to 2019, from over 100 publicly traded tourism companies in three Asian countries. A panel data methodology and the generalized method of moments estimation (GMM) were used in this empirical study. To support our hypothesis, using a generic method to evaluate parameter estimation will be our most effective method to improve the literature. Overall, the results show that financially stressed tourism firms use their option of debt-free tax avoidance to increase leverage. There is also a positive correlation between tax haven and leverage for firms with limited resources. The correlations between financial leverage and corporate debt supported by the results theoretically support the pecking order. By providing useful insights into the tax shielding of non-debt, which is significantly correlated with leverage for firms operating in tourism, this study closes the gap in firms' capital structure decisions regarding access to finance.JEL Classification: G0, G01, L2
Reduced graphene oxide supported meso-pyridyl BODIPY-Cobaloxime complexes for electrocatalytic hydrogen evolution reaction
No full textCreating innovative catalysts utilizing nonprecious metals for the electrocatalytic hydrogen evolution reaction (HER) poses a significant difficulty. We present a cobaloxime (Cox) complex having pyridine (2-Cox) and tetrafluorophenyl-thio-pyridine (4-Cox) functional groups, which contains a 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) moiety. This combination serves as a catalyst for proton reduction and is immobilized onto reduced graphene oxide (rGO) by pi-pi stacking between the cobaloxime complex and rGO. Moreover, the unique complex's structures were determined through the application of ultraviolet-visible spectroscopy (UV-Vis), Fourier Transform Infrared spectroscopy (FT-IR), X-ray diffraction spectroscopy (XRD), and scanning electron microscopy (SEM). The electrocatalytic activity of the two rGO/2-Cox and rGO/4-Cox electrodes towards hydrogen (H-2) were examined under both alkaline and acidic conditions. The cobaloxime-modified rGO electrodes demonstrate superior electrocatalytic performance for the HER under acidic conditions compared to alkaline conditions. The overpotential at a current density of 10 mA cm(-2) for rGO/2-Cox in 0.5 M H2SO4 is -0.342 V, which is notably lower than the overpotential of rGO/4-Cox (-0.496 V). The Tafel slope for the rGO/2-Cox electrode in a 0.5 M H2SO4 solution is 111 mV.dec(-1), but for the rGO/4-Cox electrode it is 156 mVdec(-1). This discrepancy suggests that the rGO/2-Cox electrode demonstrates better performance in the HER compared to the rGO/4-Cox electrode.Research Fund of the Istanbul Technical University [43721]This work was supported by the Research Fund of the Istanbul Technical University (Project Number: 43721) . The authors thank Prof. Dr. Emin Ciftci for their contribution about XRD measurements