Mühendislik ve Doğa Bilimleri Fakültesi Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.13091/1624

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Citation - Scopus: 5
Achieving Shojinka by Integrated Balancing of Multiple Straight Lines With Resource Dependent Task Times
(Springer New York LLC, 2019) Atasagun, Y.; Kara, Y.; Can Atasagun, Gözde
The concept of Shojinka, which is an important element of Just in Time production system, is attaining flexibility on the number of workers in a workshop due to demand variations. Even though Just in Time production system adopts U-shaped line layout, traditional straight lines can be combined and balanced in an integrated manner to obtain the advantages of Shojinka. In this case, the problem, which is called Integrated Balancing of Multiple Straight Lines, arises. On the other hand, the basic assumption of assembly line balancing is that every task’s time is fixed. However, in practice, different resource alternatives such as equipment or assistant worker may be available to process a task with different times. The problem in this case is to assign tasks and resources to stations that minimise total cost. In this study, a binary integer mathematical model is presented for integrated balancing of multiple straight lines, assuming that task times are resource dependent. The proposed model is illustrated and validated using several examples. An experimental analysis is also conducted to emphasize the advantages of the integrated balancing concept, compared to the situation in which the lines are balanced independent from each other. The experimental results show that, when multiple straight assembly lines are balanced in an integrated manner with resource dependent task times, an average total cost improvement of 23.105% can be obtained compared to the independent balances of the lines. This is a significant improvement that emphasizes the importance of balancing multiple straight lines in an integrated manner, to take the advantages of shojinka and to adhere to the main philosophy of Just in Time. © Springer Nature Switzerland AG 2019.
Citation - Scopus: 2
Advanced Applications of Green Materials for Gas Separation and Storage
(Elsevier, 2020) Kırbıyık Kurukavak, Çisem; Kuş, Mahmut
Extraordinary increase in global energy demand and supply, thus the environmental pollution, is one of the most important problem for today’s modern life. Gas separation and storage applications are closely related to control of the greenhouse gas and to use of clean and renewable energy. The development of green materials with desired combination properties and corresponding methods for target applications, which can minimize the environmental impact by using renewable sources has been having a growing attention over the last decades. Green and eco-friendly techniques, also called as “green chemistry, " focus on the processes and products, which reduce the use of hazardous substances and nonrenewable sources. Membrane separation, absorption, and physical adsorption for gas separation, purification, and storage are considered to be energy-efficient, low-cost, renewable, and environmental-friendly for a sustainable future. In this section, we highlight the details of these green techniques in gas separation and storage applications. © 2021 Elsevier Ltd. All rights reserved.
Citation - Scopus: 2
Advanced Applications of Green Materials in Bioelectronics Applications
(Elsevier, 2020) Yılmaz, Tuğbahan; Kuş, Mahmut
Green materials have great potential to become a primary research area for bioelectronic integration. Over the last three decades, bioelectronic applications have been getting great interest due to their low cost, flexible, nontoxic, large-volume electronic components that are sustainable, biocompatible, biodegradable, and bioresorbable. Therefore the versatility of bioelectronics applications, such as organic field-effect transistors and biosensors, promises a bright future. This chapter will highlight recent progress in the natural materials and some of their applications in bioelectronics devices. The key strategies and the forecast perspectives of this research field are also briefly summarized. © 2021 Elsevier Ltd. All rights reserved.
Altınapa Stromatolit ve Onkolitlerinin (konya) Oluşumu, Tipleri ve Jeoturizm Potansiyeli
(Gece Kitaplığı, 2020) Parlar, Şeyda; Eren, Yaşar
Asbestos Exposure in Urban Renewal
(Duvar Yayınları, 2022) Özdemir, Sıtkı Alper; Çöğürcü, Mustafa Tolga; Arslan, Mehmet Akif
Autogenous Self-Healing Assessment of 1-Year Cementitious Composites
(Springer Science and Business Media B.V., 2021) Yildirim, Gurkan; Ulugol, Huseyin; Ozturk, Oguzhan; Sahmaran, Mustafa
Traditional concrete materials are prone to cracking and as cracks form, durability issues arise which reduce the expected service life of the materials followed by structures incorporating them. This, in many occasions, may lead to repetitive repair and maintenance or even re-construction of certain structural/non-structural sections and structures. Thus, it is highly desirable to reduce the chance and/or further development of cracking. Engineered Cementitious Composites (ECC) are feasible materials to suppress cracking formation and progression through their strain-hardening response under uniaxial tensile loading conditions. Even at the stage of failure, these materials exhibit micron-size cracks which significantly improve the capability to resist against detrimental durability issues. Moreover, these microcracks are constantly reported to be closed through autogenous healing mechanisms with no external interference from outside which significantly improve the mechanical and durability performance and service life of these materials and structures incorporating them. However, the performance of autogenous self-healing in ECC is called into question, especially for late-age specimens since reactions which produce products to plug the micro-size cracks stabilize as the specimens get more and more mature. To clarify this subject, in this study, 1-year-old specimens produced from ECC mixtures incorporated with different mineral admixtures (i.e. Class-F fly ash and ground granulated blast furnace slag) were tested for their self-healing performance. For self-healing evaluation, specimens which were severely preloaded for creating microcracks, were subjected to four different curing conditions which included "Water", "Air", "CO2-water" and "CO2-air" for 90 additional days beyond initial 1 year. Tests used for self-healing assessments were electrical impedance (EI) and rapid chloride permeability (RCP). Results indicate that water is a must-have component for enhanced autogenous self-healing efficiency. "CO2-Water" curing results in the most effective self-healing performance regardless of the composition of ECC mixtures. By properly adjusting mixture proportions and curing conditions, microcracks as large as nearly half a millimeter (458 mu m) can be healed in only 30 days of further curing. Overall, results clearly suggest that late-age autogenous self-healing capability of ECC can be made as effective as the early-age with proper further environmental conditioning and mixture design.
Citation - Scopus: 8
Characterization of Bionanocomposites
(Elsevier, 2021) Kırbıyık Kurukavak, Çisem; Yılmaz, Tuğbahan
Bionanocomposites have gained a great interest from researchers as they offer remarkable properties to be used in different fields, including biology, materials science, chemistry, and nanotechnology. However, it is well known that the specific application can only be determined if their structure is illuminated at the atomic level. This chapter describes a brief overview of some spectroscopic and morphologic characterization techniques to understand the morphology, microstructure, and intermolecular interactions of bionanocomposites. © 2021 Elsevier Ltd All rights reserved.
Citation - Scopus: 11
Design and Synthesis of Metal Oxide-Polymer Composites
(Elsevier, 2022) Kaya Güzel, Gülcihan; Deveci, Hüseyin
Recently, metal oxide-polymer composites have received significant attention in many industrial fields. The combination of metal oxides (commonly used TiO2, ZnO, Fe3O4, and Al2O3) with a polymer matrix governs to produce high-performance metal oxide-polymer composites by in situ polymerization, sol-gel method, solution blending, or melt blending. Design of the metal oxide-polymer composites is essential to meet requirements for tailored productions of the composite materials. Many design parameters such as metal oxide characteristics and alignment, polymer matrix structure, amount of metal oxide/polymer matrix, surface modifications, and production conditions considerably affect interactions between a metal oxide and polymer matrix. Good compatibility of metal oxide with polymer matrix through homogeneous dispersion of the metal oxide in the matrix provides synergistic effects on the properties of the composites. The authors represented the design and synthesis of the metal oxide-polymer composites in detail in this chapter. Enhanced mechanical, electrical, optical, magnetic, thermal, barrier, and antibacterial properties of the metal oxide-polymer composites were briefly mentioned depending on design parameters. © 2022 Elsevier Inc. All rights reserved.
Citation - Scopus: 1
Determination of Autogenous Self-Healing Capability of Cementitious Composites Through Non-Destructive Testing
(Springer Science and Business Media B.V., 2021) Yıldırım, Gürkan; Öztürk, Oğuzhan; Ulugöl, H.; Hatem, M.; Şahmaran, Mustafa
Unlike conventional concrete and fiber reinforced concrete, Engineered Cementitious Composites (ECC) display closely spaced multiple microcracks through strain/deflection-hardening response when subjected to tension-based loadings. These multiple microcracks allow ECC to be characterized with inherent autogenous self-healing capability. With the emergence of cement-based composites exhibiting multiple tight cracking, possibility for favoring the intrinsic self-healing behavior increased. Self-healing phenomenon in cementitious composites is being studied extensively nowadays. Although, great number of tests utilized to evaluate the self-healing mechanism in cementitious composites, implementation can be time consuming in some occasions and results from different tests may not always well-suit. Thus, different from other studies in literature, direct electrical impedance (EI) measurements were used in the present study to evaluate the self-healing performance of ECC mixtures along with rapid chloride permeability test (RCPT) and resonant frequency (RF) measurements. Experimental results revealed that EI testing is rather easy to perform and takes very limited time but it seems that the method itself is markedly influenced by anything modifying ionic state of specimens. Therefore, it looks like a hard task to very accurately assess the self-healing performance of ECC specimens considering the fact that both ongoing hydration and calcium carbonate precipitation which are regarded to be the main mechanisms contributing to the autogenous self-healing significantly changes the specimens’ pore solution chemistry. Well-fitting exponential relationship exists between EI and RCPT measurements at different ages regardless of the mixture and specimen type. However, results from RF tests do not correlate either with EI or RCPT results which is attributed to the different parameters having paramount influence on the individual tests. Although results from different tests do not always correlate well among themselves, three different tests used for the present study are capable of monitoring the self-healing behavior with differing efficiencies. © 2021, The Author(s), under exclusive license to Springer Nature Switzerland AG.
Citation - WoS: 1
Citation - Scopus: 1
Determination of Autogenous Self-Healing Capability of Cementitious Composites Through Non-Destructive Testing
(Springer Science and Business Media B.V., 2021) Yildirim, Gurkan; Ozturk, Oguzhan; Ulugol, Huseyin; Hatem, Muhammed; Sahmaran, Mustafa
Unlike conventional concrete and fiber reinforced concrete, Engineered Cementitious Composites (ECC) display closely spaced multiple microcracks through strain/deflection-hardening response when subjected to tension-based loadings. These multiple microcracks allow ECC to be characterized with inherent autogenous self-healing capability. With the emergence of cement-based composites exhibiting multiple tight cracking, possibility for favoring the intrinsic self-healing behavior increased. Self-healing phenomenon in cementitious composites is being studied extensively nowadays. Although, great number of tests utilized to evaluate the self-healing mechanism in cementitious composites, implementation can be time consuming in some occasions and results from different tests may not always well-suit. Thus, different from other studies in literature, direct electrical impedance (EI) measurements were used in the present study to evaluate the self-healing performance of ECC mixtures along with rapid chloride permeability test (RCPT) and resonant frequency (RF) measurements. Experimental results revealed that EI testing is rather easy to perform and takes very limited time but it seems that the method itself is markedly influenced by anything modifying ionic state of specimens. Therefore, it looks like a hard task to very accurately assess the self-healing performance of ECC specimens considering the fact that both ongoing hydration and calcium carbonate precipitation which are regarded to be the main mechanisms contributing to the autogenous self-healing significantly changes the specimens' pore solution chemistry. Well-fitting exponential relationship exists between EI and RCPT measurements at different ages regardless of the mixture and specimen type. However, results from RF tests do not correlate either with EI or RCPT results which is attributed to the different parameters having paramount influence on the individual tests. Although results from different tests do not always correlate well among themselves, three different tests used for the present study are capable of monitoring the self-healing behavior with differing efficiencies.
Development of Empirical Equations To Predict the Strength Properties of Rocks With Non-Destructive Test Techniques
(Bidge Yayınları, 2023) Balcı, Mehmet Can; İnce, İsmail; Bozdağ, Ali
Dünya’da ve Türkiye’de Obruk Oluşumları; Tanım, Sınıflandırma ve Oluşum Koşulları
(Orient Yayınları, 2023) Arık, Fetullah
Effect of Binary-Use Mineral Admixtures for the Advanced Autogenous Self-Healing Behavior of Fiber-Reinforced Cementitious Composites
(Springer Science and Business Media B.V., 2021) Öztürk, Oğuzhan; Roig-Flores, M.
This paper comprises the enhanced self-healing properties of fiber-reinforced cementitious composites by taking advantage of synergistic effect of using different mineral admixtures. To do this, single and binary use of metakaolin (MK) and zeolite (Z) were utilized in cement-based mixtures, and early age self-healing behavior of specimens was assessed based on sorptivity tests. The autogenous self-healing performance of each mixture was also evaluated via crack width assessments by using a video microscope. Results were compared with the sound and preloaded specimens having different crack width levels. In addition, mechanical properties of four different mixtures were evaluated by conducting experiments on 7 and 28 days. The multiple crack width closures and sorptivity coefficients of preloaded specimens indicated that an effective combination of MK and Z can trigger a higher level of self-healing in comparison with reference mixture. However, single-use of Z in mixtures was also promising for achieving autogenous self-healing attributes compared to mixtures containing only MK and to reference mixtures. Having said that, this behavior should also be addressed for different pre-cracking and prolonged curing age of each mixture. © 2021, RILEM.
Fire Resistant Material Recommendation for Sidings of Educational Buildings
(Duvar Yayınları, 2022) Özdemir, Sıtkı Alper; Çöğürcü, Mustafa Tolga; Arslan, Mehmet Akif
Citation - Scopus: 5
Future Perspectives of Perovskite Solar Cells: Metal Oxide-Based Inorganic Hole-Transporting Materials
(Elsevier, 2020) Kaya, İsmail Cihan; Akin, S.; Sönmezoğlu, Savaş
The hybrid organic-inorganic metal halide perovskite solar cell (PSC) is a promising and emerging technology with certified efficiency currently reaching above 25%. Despite unprecedented development, PSCs based on operationally instable and extremely expensive organic hole-transporting materials (HTMs) such as N 2, N 2', N 2', N 7, N 7, N 7', N 7'-octakis(4-methoxyphenyl)-9, 9'-spirobi[9H-fluorene]-2, 2', 7, 7'-tetramine or poly[bis(4-phenyl)(2, 4, 6-trimethylphenyl)amine] are far from commercialization. There is an urge to develop new sustainable materials to combat these issues associated with organic-based HTMs. This chapter focuses on the significance of metal oxide-based inorganic functional materials as HTMs in different PSC architectures. The first section of the chapter presents the basics of PSC technology, including working principles, device structures, components, and challenging issues. The following section introduces sustainable hole conductors as well as an outline of the current routes to enhance long-term operational stability and reduce material cost using innovative approaches. The prerequisites of a novel HTM and compatibility with neighboring layers are also briefly discussed. In the last section, highly promising metal oxide-based inorganic HTMs and current progress are highlighted comprehensively to illustrate the importance of inorganic materials in terms of the state-of-the-art of PSCs. Overall, this chapter provides a roadmap of the current demands and future research directions to address the main critical concerns of PSCs that must be tackled to mitigate the major barriers on the pathway to upscaling applications. © 2021 Elsevier Inc. All rights reserved.
Citation - Scopus: 2
Gaussian Regression Models for Day-Level Forecasting of Covid-19 in European Countries
(Springer Science and Business Media Deutschland GmbH, 2022) Özkaya, Umut; Öztürk, Şaban
Coronavirus (COVID-19) outbreak has reached a global disease and has begun to threaten all over the world. No vaccine or drug has been developed to treat the outbreak, still. According to the data of the World Health Organization (WHO), the COVID-19 virus can be easily transmitted through respiratory droplets and contact routes. States need to take necessary measures to control the outbreak. In this study, pandemic data for eight countries in the European region are analyzed between 22 January 2020 and 30 April 2020. These countries are Belgium, Netherlands, Germany, UK, Spain, France, Italy, and Turkey. The number of cases is taken into consideration in the selection of countries. Gaussian regression analysis is preferred for the COVID-19 outbreak analysis. A comparative analysis is performed using Ard-Exponential kernel function, Rational-Quadratic kernel function, and Squared Exponential kernel functions. The quasi-Newton algorithm is used to optimize regression models. Confirmed death and recovered case data are processed in the scope of the analysis. The first 90 days of the data are used for the training of Gaussian regression models. The last nine days are evaluated for prediction. Mean Absolute Error (MAE), Median Error (ME), Mean Squared Error (MSE), and Root Mean Squared Error (RMSE) error metrics are used for metric of performance. In general, it is seen that the Ard-Exponential kernel with Gaussian Regression (AEGR) method obtained high metric performances for all cases and countries. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.
Geçmişten Geleceğe Tıbbi Jeoloji
(Orient Yayınları, 2023) Arık, Fetullah
Citation - WoS: 11
Hazelnut (Corylus avellana) Oil
(SPRINGER INTERNATIONAL PUBLISHING AG, 2019) Topkafa, Mustafa; Ayyıldız, Hamide Filiz; Kara, Hüseyin
Hazelnut (Corylus avellana), which is present since pre-agricultural times, belongs to the Betulaceae family and cultivated in many countries, such as Turkey, USA, Azerbaijan, Georgia, Spain, Portugal and France as well as in regions with temperate climate of the northern hemisphere. Hazelnut, which is annually produced approximately 850,000 tons worldwide, is used in chocolate, bakery products, snacks, and edible oil industry. The most important nutrients in the hazelnut are lipids, protein, carbohydrate, phytosterols, vitamins and minerals. The most concentrated content of these components is the oil (50-70%). Hazelnut oil is used in food, cake-biscuit, paint, cosmetics, and soap industry. In this chapter, potential and economic value of hazelnut, production methods of oil, chemical and nutritional properties, nutrient value and chemical composition of hazelnut oil are discussed. In addition, triglyceride, fatty acid, tocopherols, sterols and volatile compounds composition of hazelnut oil were highlighted. The health effects of bioactive lipids such as the proper functioning of the human body, growth and physiological functions are reported in the main headings. The chemical profile of hazelnut oil is very similar to olive oil, wherein olive oil is adulterated with hazelnut oil. For this reason, adulteration of olive oil with hazelnut oil is evaluated in last main heading.
History, Experiments and Design of Self Compacting Concrete
(Eğitim Yayınevi, 2022) Cengiz, Salih; Kamanlı, Mehmet
Citation - Scopus: 1
Integrated Production and Transportation Scheduling Problem With Multiple Plants, Multiple Vehicles and Perishable Products
(Springer Science and Business Media Deutschland GmbH, 2022) Can Atasagun, Gözde; Karaoğlan, İsmail
The integrated production and transportation scheduling problem is one of the interesting topics in the literature. This paper addresses Integrated Production and Transportation Scheduling Problems with Multiple Plants, Multiple Vehicles, and Perishable Products (PTSP-MP-MV). To the best of our knowledge, this problem has not been studied in the literature. In this problem, each plant has a different capacity and a different production rate. There is a single machine and a limited number of homogeneous vehicles in each plant. Each vehicle can be used more than once because of the vehicle capacity and planning horizon restrictions. Only one type of product is produced, and this product has a limited lifespan. The objective of the problem is to minimize the total cost including production, distribution, and vehicle costs. We propose a mixed integer programming (MIP) formulation for the problem and strengthen it with several valid inequalities to improve lower bounds. The performance of the formulation is calculated using a newly generated set of test instances. Computational results show that small-sized instances with 5 and 10 customers can be solved optimally in less than 90 s. Satisfactory results are obtained for the test instances up to 20 customers whose optimality gap values are calculated as 0.54% nearly 1 h. It is also shown that the valid inequalities are improved lower bounds about 3%. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.

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