Uludag University Academic Repository
Not a member yet
50710 research outputs found
Sort by
Exploring the tribological properties and wear morphology of high-temperature mxene/cmc nanofluid as a high-performance and environmentally lubricant
No full textThis research investigates the tribological properties of an MXene/Carboxymethyl Cellulose (CMC) water-based nanofluid as a high-performance and environmentally sustainable automotive coolant. The study examines the nanofluid's tribological characteristics and wear morphology under high-temperature conditions. The nanofluid was prepared by mixing MXene powder with water and then sonicated. CMC was also added to enhance viscosity. The pinon-disk tribometer was employed to investigate the friction coefficients (CoF) at high temperatures by using a heater and 10 N normal load. The disks were placed in a reservoir filled with nanofluid. As soon as the temperature reached 65°C, the tribological test was conducted for a total of 25 minutes at a sliding velocity of 0.2 m/s. The results of this study show that the addition of MXene and CMC provides low COF even at high temperatures. Moreover, from the wear morphology, the high stability of the MXene/CMC nanofluid could prevent the disk from corroding and result in minimal damage. These results have promising implications for the potential use of MXene/CMC nanofluid as an advanced automotive coolant, offering good tribological performance at high temperatures, which are essential qualities for modern, sustainable automotive coolants
CEO salary gap, board gender diversity and audit quality: UK experience
No full textThis study investigates the relationship between CEO salary gaps and audit quality, focusing on auditor size (Big 4) and audit fees. Additionally, it examines the moderating role of board gender diversity (BGD) in shaping these relationships. The current study utilizes a sample of 384 UK firms from the industry, energy, and basic materials sectors, constructing an unbalanced panel of 3,840 firm-year observations covering the period 2014-2023. The study uses Logit regression and Generalized Least Squares to provide empirical insights into the impact of CEO salary gap on audit quality. The findings of the study suggest that firms with a larger CEO salary gap are more likely to recruit the Big 4 auditors, and these auditors are more inclined to charge high audit fees, potentially leading to improved audit quality. Moreover, the findings indicate that BGD plays an active role in moderating the relationship between CEO salary gap and both Big 4 auditors and audit fees. This research extends existing studies by investigating how CEO compensation disparities influence audit decisions, a topic that has not been fully explored in prior literature. Second, it addresses the underexplored moderating role of board gender diversity in shaping the relationship between CEO salary gaps and audit quality. By incorporating board gender diversity as a moderating variable, the study provides a more nuanced understanding of how diversity shapes corporate governance outcomes
Highly-miniaturized spacecraft "PlanarSat": Evaluating prospects and challenges through a survey of femto & atto satellite missions
No full textAs satellite technology advances, there has been a notable trend towards miniaturization, leading to the development of increasingly smaller satellites such as femtosatellites and attosatellites. A new emerging form of such satellites is often called ChipSat, with unique designs that utilize both surfaces of a single plane to maximize functionality within limited dimensions. Initially, the term ChipSat referred to system-on-a-chip satellites but it has since expanded to include centimeter and millimeter scale spacecraft. To provide a clearer terminology, this paper introduces the term "PlanarSat" for such a planar spacecraft. Despite the challenges in deployment and the constraints, such as cost, size, access to space, and capabilities, of miniaturized subsystems, these satellites represent a significant shift in space technology, aiming for costeffective solutions and innovative mission capabilities. This study reviews thirty sub-100-gram satellites, analyzing their design, deployment, and potential for future advancements in a comparative manner. In this study, satellite independence was defined based on system-wise independence, highlighting operational autonomy irrespective of physical connections. The survey's findings highlight technological advancements and potential applications for these very small spacecraft, which are pushing the boundaries of what is feasible with smaller satellites and how these satellites were or planned to be delivered to orbit. The analysis results provide a basic cost comparison, providing information on hardware and launch costs, taking the instantaneous data rate as a reference point, underscoring the need for a new systems engineering approach to the design of such satellites
Performance evaluation of fresh food cold chain logistics service providers using a fuzzy DEMATEL-based fuzzy VIKOR method: A case study in Kenya
Get PDFTaze ürünler veya çabuk bozulan gıdalar, muhafazası zor olan ve meyve, sebze, et, deniz ürünleri ve işlenmiş gıdalar gibi kategorileri içeren gıdalardır. Meyve ve sebzeler genellikle çiğ, taze kesilmiş veya asgari düzeyde işlenmiş olarak tüketilir. Etkili soğuk zincir yönetimi, tüketicilere ulaştırılan taze gıdaların kalitesinin sağlanması açısından hayati öneme sahiptir. Taze meyve ve sebze endüstrisi, dinamik ve oldukça rekabetçi bir sektör olup, özellikle gelişmekte olan ülkelerde kalite sorunları ve gıda güvenliğine yönelik tehditlerle karşı karşıyadır. Yetersiz soğuk zincir altyapısı nedeniyle, gelişmekte olan ülkelerde meyve, sebze ve süt ürünleri de dahil olmak üzere bozulabilir gıdaların %40’ı, tüketicilere ulaşmadan kaybedilmektedir. Gıda kaybı ekonomiye, çevreye, topluma ve gıda güvenliğine zarar verir. Gıda soğuk zincirleri gıda kaybını ve israfını azaltmada önemli bir rol oynar. Soğuk zincir lojistik sistemleri kurmak için önemli miktarda maddi ve finansal kaynak gerektiğinden, firmalar genellikle soğuk zincir lojistik hizmet sağlayıcılar ile çalışmaktadırlar. Bu bağlamda, hizmet sağlayıcılar stratejik hedeflere ulaşmaya ve rekabet avantajları elde etmeye yardımcı olur. Afrika'da çiftçilerin yetiştirdiği gıdanın yaklaşık üçte biri soğutma eksikliği, pazara erişimin zayıf olması ve diğer ilgili faktörler nedeniyle kaybolmaktadır. Meyve ve sebzelerin yıllık gıda kayıplarının %40 ila %50 olduğu tahmin edilmektedir. Bu çalışmada, Bütünleşik Çok Kriterli Karar Verme tekniği kullanılarak Kenya'da soğuk zincir lojistik hizmet sağlayıcılarının seçiminin öznelliği ve belirsizliği analiz edilmiştir. Bu yaklaşıma dayanarak, tez Kenya'daki taze ürün lojistik hizmet sağlayıcılarını Çok Kriterli Karar Verme (ÇKKV) yöntemini kullanarak değerlendirmeyi amaçlamaktadır. Önerilen üç aşamalı yaklaşım, taze gıda soğuk zincir sağlayıcılarını seçme kriterlerinin sistematik bir literatür incelemesi ve bir uzman toplantısı yolu ile belirlendiği ilk aşama ile başlar. Kriterler, ikinci aşamada bulanık DEMATEL yöntemi ile hesaplama yapılarak ağırlıklandırılır. Üçüncü aşama, bulanık VIKOR yöntemi kullanılarak alternatif soğuk zincir lojistik hizmet sağlayıcılarının değerlendirilmesini ve seçilmesini içerir. Çalışmanın analiz bölümünde, taze gıda için lojistik hizmet sağlayıcılarını seçerken performansı etkilemek için 17 farklı kriter kullanılmıştır. Çalışma analiz sonucunda, kriterler ağırlıklarının arasında hizmet kalitesi ve gıda güvenliği (C5), en önemli en önemli faktör olduğu tespit edilmiştir. Bununla birlikte Soğuk zincir altyapı ve ekipman kapasitesi (C6), hükümet politikası yasaları ve düzenlemeleri (C14) ve risk faktörü (C17) kriterlerin de kritik öneme sahip olduğu belirlenmiştir. Bulanık VIKOR yöntemi kullanılarak elde edilen sıralama sonuçları, lojistik hizmet sağlayıcıları içinden en iyi alternatifin LSP2 olduğunu göstermektedir.Fresh produce, or perishable foods, is challenging to preserve and includes categories such as fruit, vegetables, meat, seafood, and processed foods. Fruits and vegetables are often consumed raw, freshly cut, or minimally processed. Effective cold chain management is essential to ensure the quality of fresh food delivered to consumers. The fresh fruit and vegetable industry is a dynamic and highly competitive sector that struggles with quality issues and threatens food safety in developing countries. Due to inadequate cold chain infrastructure, up to 40 percent of perishable goods, including fruit, vegetables, and dairy products, are lost before they reach consumers in developing countries. Food loss hurts the economy, the environment, society, and food security. Food cold chains play a crucial role in reducing food loss and waste. As considerable material and financial resources are required to set up cold chain logistics systems, companies often appoint cold chain logistics partners as service providers. In this context, the service providers help to achieve strategic goals and gain competitive advantages. In Africa, about a third of the food farmers grow is lost due to lack of refrigeration, poor m arket access, and other related factors. Annual food losses of fruit and vegetables are estimated at 40 to 50 percent. Using an integrated Multicriteria Decision Making technique, this study analyzed subjectivity and uncertainty in selecting cold chain logistics service providers in Kenya. Based on this approach, the thesis aims to evaluate fresh produce logistics service providers in Kenya using the multicriteria decision-making (MCDM) technique. The proposed three-phase approach starts with the first phase, in which the criteria for selecting fresh food cold chain providers are identified through a systematic literature review and an expert meeting. The criteria are calculated and weighed using the fuzzy DEMATEL method in the second phase. The third phase comprises evaluating and selecting alternative cold chain logistics service providers using the fuzzy VIKOR method and the performance of a sensitivity analysis. In the analysis part of the study, 17 different criteria were used to influence performance when selecting logistics service providers for fresh food. As a result of the study analysis, it was determined that service quality and food safety (C5) were the most important factors among the criteria weights. However, cold chain infrastructure and equipment capacity (C6), government policy laws and regulations (C14) and risk factor (C17) criteria were also determined to be of critical importance. The ranking results obtained using the fuzzy VIKOR method show that LSP2 is the best alternative for the logistics service provider
Dynamic torsional response of viscoelastic porous nanorods with viscoelastic boundary constraints
Get PDFIn this study, the torsional vibration behavior of a viscoelastic porous nanorod has been analyzed using a semi-analytical solution method under viscoelastic boundary conditions. The Kelvin-Voigt model has been employed to represent viscoelastic behavior, while the modified couple stress theory has been adopted to account for size effects. The equation of motion of the viscoelastic porous nanorod has been derived in accordance with Hamiltonian principle, and the problem has been solved using higher order derivatives obtained through Fourier series and Stokes' transforms. Unlike previous studies in the literature, the proposed method has enabled the calculation of frequencies for various boundary conditions from a single eigenvalue problem. The accuracy of the results has been verified by comparison with existing studies and then analyses for the viscoelastic porous nanorod with viscoelastic boundary conditions presented in a series of tables and graphs. The analyses have revealed that the influence of the dimensionless damping parameter on frequency becomes more pronounced as the size parameter increases, while the porous parameter plays a significant role in the dynamic behavior of nanorods
Evaluation of caries detection on bitewing radiographs: A comparative analysis of the improved deep learning model and dentist performance
No full textObjectivesThe application of deep learning techniques for detecting caries in bitewing radiographs has gained significant attention in recent years. However, the comparative performance of various modern deep learning models and strategies to enhance their accuracy remains an area requiring further investigation.MethodsThis study explored the capabilities of 11 widely used YOLO (You Only Look Once) object detection models to automatically identify enamel and dentin caries from bitewing radiographs. To further optimize detection performance, the YOLOv9c model's backbone architecture was refined, reducing both model size and computational requirements. The enhanced model was assessed alongside six dentists, using the same test dataset for direct comparison.ResultsThe proposed YOLOv9c model achieved the highest performance among the evaluated models, with recall, precision, specificity, F1-score, and Youden index values of 0.727, 0.651, 0.726, 0.687, and 0.453, respectively. Notably, the YOLOv9c model surpassed the performance of the dentists, as indicated by its recall and F1-score values.ConclusionsThe proposed YOLOv9c model proved to be highly effective in detecting enamel and dentin caries, outperforming other models and even clinical evaluations by dentists in this study. Its high accuracy positions it as a valuable tool to augment dentists' diagnostic capabilities.Clinical SignificanceThe results emphasize the potential of the YOLOv9c model to assist dentists in clinical settings, offering accurate and efficient support for caries detection and contributing to improved patient outcomes
Happiness across cultures: Considering the relationship between general well-being and hofstede's culture dimensions
No full textThis paper examines the relationships between Hofstede's culture dimensions and happiness at both the country and individual levels. Study 1 was conducted with the scores of 60 countries obtained from open-source datasets. Results indicated that countries with lower collectivism and power distance scores had higher levels of happiness, after controlling for income level. Study 2, a survey-based research, tested the relationships between internalized culture dimensions by Turkish people living in T & uuml;rkiye (n = 312) or Dutch people living in the Netherlands (n = 201) and happiness-related variables. After controlling for demographics, (i) Turkish people with higher long-term orientation, masculinity and power distance scores were more satisfied with their lives; (ii) Turkish people with higher long-term orientation score and lower power distance score had higher psychological well-being; (iii) Turkish people with higher long-term orientation and masculinity scores felt more grateful for the life they have. Additionally, (i) Dutch people with higher long-term orientation score had higher psychological well-being; (ii) Dutch people with lower power distance score felt more grateful for the life they have. The current studies demonstrate that, even after controlling for countries' income level and individuals' demographic characteristics, culture dimensions are associated with happiness at the country level in Study 1 and happiness-related variables at the individual level in Study 2. The results provide meaningful insights and practical implications for policymakers, educators, and mental health professionals who aim to enhance happiness through culturally sensitive approaches and to develop more sustainable social systems
Impact of microplastic contamination on phosphorus availability, alkaline phosphatase activity, and polymer degradation in soil
No full textMicroplastics (MPs) are emerging contaminants that can significantly impact soil nutrient dynamics, particularly phosphorus (P) cycling, which is critical for maintaining soil fertility and ecosystem productivity. However, limited information is available on how different microplastic types and concentrations specifically influence phosphorus dynamics and microbial enzyme activity in soils. Microplastic contamination may alter P cycling by directly supplying phosphorus or indirectly influencing microbial activity and enzyme function through changes in soil structure and aggregation. This study examined the short-term impacts of three widely used microplastic polymers-polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET)-on soil phosphorus forms and alkaline phosphatase activity (APA), a key enzyme in phosphorus transformation. Incubation experiments were conducted at two concentrations (0.5% and 5%) over 30 and 60 days. The results indicated that the impact of microplastics on soil phosphorus dynamics varied according to both polymer type and contamination dose. Microplastics increased available phosphorus (AP) and APA levels compared to control soils, indicating a stimulatory effect on microbial processes. This may be due to the temporary accumulation of phosphorus on MP surfaces, which can stimulate phosphatase activity. Over time, however, both AP and APA levels declined, suggesting that degradation products released from MPs and organic matter may have altered the activity of the microbial communities responsible for P cycling. FTIR analysis revealed clear degradation of microplastics, with PET showing the most pronounced chemical transformation. PP exhibited moderate degradation, while PE demonstrated the highest resistance to environmental breakdown. These degradation processes likely released functional groups (e.g., carboxyl, carbonyl, hydroxyl) and low-molecular-weight compounds into the soil, modifying microbial processes and phosphorus chemistry. Particularly in PET-amended soils, these degradation products may have enhanced phosphate complexation or mobilization, contributing to higher levels of available phosphorus at the end of the incubation time. Understanding the polymer-specific and concentration-dependent effects of microplastics is critical for accurate ecological risk assessment in terrestrial ecosystems
İsviçre, Neuchâtel’deki Le Boudry Kalesi’nde korunmuş Convivium mozaiği
No full textThis paper deals with the complete study of the mosaic with a convivium scene, which has been preserved since 2003 at the Musée de la vigne et du vin at the Le Boudry Castle (Neuchâtel, Switzerland), but which has not been the subject of an in-depth analysis. Thus, the architectural context with a large stibadium and a pavement of asárôtos oîkos, the servants and the various objects used for the preparation and service of food and drink, the guests and the three mensae of sumptuous and expensive materials, covered with white linen tablecloths. Considering the testimonies of some ancient authors, some of these representations, which offer an exceptional scene of a convivium, and also the parallels of two wall- paintings from 4th century AD, can be used to state that the mosaic must have come from the territories of the eastern part of the Empire, dating to the third quarter of the 4th century AD.Bu makale, 2003 yılından bu yana İsviçre’nin Neuchâtel kantonundaki Le Boudry Kalesi’nde yer alan Musée de la Vigne et du Vin’de korunan, ancak bugüne dek kapsamlı biçimde incelenmemiş olan convivium sahneli mozaik üzerine bütüncül bir değerlendirmeyi konu edinmektedir. Çalışmada, büyük bir stibadium ile asárôtos oîkos tipinde döşenmiş bir tabanın oluşturduğu mimari kontekst; yiyecek ve içeceklerin hazırlanması ile servisine hizmet eden görevliler ve kullanılan çeşitli gereçler; davetliler ve beyaz keten örtülerle kaplanmış, zengin ve pahalı malzemeden yapılmış üç mensa ayrıntılı biçimde ele alınmaktadır. Antik yazarların bazı tanıklıkları ve İS 4. yüzyıla ait iki duvar resmi ile kurulan paralellikler, convivium sahnesinin sıra dışı nitelikteki tasvirini desteklemektedir. Bu veriler ışığında, mozağin İmparatorluğun doğu eyaletlerinden gelmiş olması gerektiği ve İS 4. yüzyılın üçüncü çeyreğine tarihlendiği sonucuna varılmaktadır