WoS İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12469/4465

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Citation - WoS: 6
Citation - Scopus: 6
Gamma-Robust electricity market equilibrium models with transmission and generation investments
(SPRINGER HEIDELBERG, 2021) Çelebi, Emre; Krebs, Vanessa; Schmidt, Martin
We consider uncertain robust electricity market equilibrium problems including transmission and generation investments. Electricity market equilibrium modeling has a long tradition but is, in most of the cases, applied in a deterministic setting in which all data of the model are known. Whereas there exist some literature on stochastic equilibrium problems, the field of robust equilibrium models is still in its infancy. We contribute to this new field of research by considering Gamma-robust electricity market equilibrium models on lossless DC networks with transmission and generation investments. We state the nominal market equilibrium problem as a mixed complementarity problem as well as its variational inequality and welfare optimization counterparts. For the latter, we then derive a Gamma-robust formulation and show that it is indeed the counterpart of a market equilibrium problem with robustified player problems. Finally, we present two case studies to gain insights into the general effects of robustification on electricity market models. In particular, our case studies reveal that the transmission system operator tends to act more risk-neutral in the robust setting, whereas generating firms clearly behave more risk-averse.
Citation - WoS: 1
A Serbian Princess in Ottoman Palace: Mileva Olivera Lazarevic
(Ahmet Yesevi University, 2017) Keskin, Mustafa Çağhan
Born as the daughter of the serbian Knez Lazar taken into the Ottoman palace marrying Bayezid I (The Thunderbolt) who gave her father's execution order became the slave of Timur (Tamerlane) after the Battle of Ankara and when set free turning back to her country Olivera had a life full of trauma and tragedies resembling a romantic adventure According to the serbian she was a hero who sacrificed herself for her country according to the Ottomans she was a bad woman who adapted Bayezid to alcohol and entertainment according to European orientalist myths she was a princess who was despised by barbarians to whom was taken captive. This study aims to reveal the image of Olivera reflected in the works of contemporary Ottoman Byzantine Serbian Timurid and European sources narratives and arts with a focus on the life story of Olivera who although was essentially a member of the Ottoman dynasty did not have any monographs about her in Turkey.
Citation - Scopus: 2
Detection of Multiple Primary Systems Using Daa Uwb-Irs
(IEEE, 2009) Erküçük, Serhat; Lampe, Lutz; Schober, Robert
Underlay ultra wideband (UWB) systems have to be able to detect the presence of primary systems operating in the same band for detect-and-avoid (DAA) operation. In this paper the performances of joint and independent detection of multiple primary systems are investigated assuming that the primary systems are potentially dependent (e.g. frequency division duplex uplink-downlink communications). Joint detection is performed based on generating the maximum a posteriori (MAP) decision variables at the receiver where some bias terms are used with these variables in order to achieve a desired trade-off between the detection and false alarm probabilities. Independent detection is performed based on the Neyman-Pearson (NP) test which optimizes system threshold values individually in order to achieve the best detection probability for a given false alarm probability value. When the two detection schemes are compared it is shown that the gain of joint detection depends on the joint system activity values and the considered receiver operating characteristic (ROC) region where the complementary ROC curves illustrate the trade-off between missdetection and false alarm probabilities.
Citation - WoS: 6
Citation - Scopus: 7
An Interactive Memetic Algorithm for Production and Manufacturing Problems Modelled as a Multi-Objective Travelling Salesman Problem
(Taylor & Francis Ltd, 2012) Samanlıoğlu, Funda; Ferrell, William G.; Kurz, M. E.
In this paper a preference-based interactive memetic random-key genetic algorithm (PIMRKGA) is developed and used to find (weakly) Pareto optimal solutions to manufacturing and production problems that can be modelled as a symmetric multi-objective travelling salesman problem. Since there are a large number of solutions to these kinds of problems to reduce the computational effort and to provide more desirable and meaningful solutions to the decision maker this research focuses on using interactive input from the user to explore the most desirable parts of the efficient frontier instead of trying to reproduce the entire frontier. Here users define their preferences by selecting among five classes of objective functions and by specifying weighting coefficients bounds and optional upper bounds on indifference tradeoffs. This structure is married with the memetic algorithm - a random-key genetic algorithm hybridised by local search. The resulting methodology is an iterative process that continues until the decision maker is satisfied with the solution. The paper concludes with case studies utilising different scenarios to illustrate possible manufacturing and production related implementations of the methodology.
Citation - WoS: 8
Citation - Scopus: 11
An Improved Adaptive Subspace Tracking Algorithm Based on Approximated Power Iteration
(IEEE-INST Electrical Electronics Engineers Inc, 2018) Wu, Qiang; Zheng, Jian-Sheng; Dong, Zhicheng; Panayırcı, Erdal; Wu, Zhi-Qiang; Ren, Qingnuobu
A subspace tracking technique has drawn a lot of attentions due to its wide applications. The main objective of this approach is to estimate signal or noise subspace basis for the sample covariance matrix. In this paper we focus on providing a fast stable and adaptive subspace tracking algorithm that is implemented with low computational complexity. An alternative realization of the fast approximate power iteration (FAPI) method termed modified FAPI (MFAPI) is also presented. Rather than solving an inverse square root of a matrix employed in the FAPI the MFAPI applies the matrix product directly to ensure the orthonormality of the subspace basis matrix at each recursion. This approach yields a simpler derivation and is numerically stable while maintaining a similar computational complexity as compared with that of the FAPI. Furthermore we present a detailed mathematical proof of the numerical stability of our proposed algorithm. Computer simulation results indicate that the MFAPI outperforms many classical subspace tracking algorithms particularly at the transient-state step.
ON THE INVERSE POINT-SOURCE PROBLEM OF THE POISSON EQUATION
(Istanbul Univ, Fac Engineering, 2005) Yilmaz, Melek; Sengul, Metin; Geckinli, Melih
In this work, a basic inverse heat conduction problem of a simple 2-D model with steady state heat source is taken into view. The physical problem is for a square region with uniform thermophysical properties and a point heat source of unit magnitude. To obtain boundary data, temperature probes are placed at the midpoints of the sides of the square domain. The objective of the inverse problem is to estimate the coordinates of the point source with the least amount of data. Initially, the inverse problem is analyzed to determine the main causes that render the problem ill conditioned. As for the solution, among the methods that has been tried so far, the best results are obtained from a backpropagating ANN with four- probe data. When white Gaussian noise is added to the measurements, no catastrophic failure has been observed.
Citation - WoS: 12
Citation - Scopus: 14
Elastic Percolation of Swollen Polyacrylamide (paam)-Multiwall Carbon Nanotubes Composite
(Taylor & Francis Ltd, 2012) Evingür, Gülşen Akin; Pekcan, Önder
Polyacrylamide (PAAm)-multiwalled carbon nanotube (MWNT) composites were prepared via free radical cross-linking copolymerization with different amounts of MWNTs varying in the range between 0.1 and 50 wt%. The mechanical properties of swollen PAAm-MWNT composites were characterized by the tensile testing technique. A small content of embedded nanotubes dramatically changes the compressive elastic modulus of the composites. Compressive elastic modulus dramatically increases up to 1wt% MWNT on increasing nanotube content and then decreases presenting a critical MWNT value indicating that there is a sudden change in the material elasticity. The critical exponent y of elasticity below the critical MWNT content 1 wt% is found to be 0.58 which is consistent with the suggestions of percolation in the superelastic percolation network for PAAm-MWNT composite.
Citation - WoS: 11
Citation - Scopus: 15
Assessing and Selecting Sustainable Refrigerated Road Vehicles in Food Logistics Using a Novel Multi-Criteria Group Decision-Making Model
(Elsevier Science inc, 2024) Gorcun, Omer Faruk; Tirkolaee, Erfan Babaee; Kucukonder, Hande; Gargf, Chandra Prakash
In recent years, food loss and waste (FLW) have become an essential issue at the top of the international community's agenda. Since more people are afflicted by this problem every day, the global population would be forced into poverty and starvation without finding an immediate solution. Therefore, in order to decrease FLW, well-designed and sustainable food and cold supply chains (FCSCs) are needed. Additionally, refrigerated transportation systems can be crucial in developing sustainable supply chains. According to some empirical research, the technological capabilities of reefer vehicles or trailers differ significantly. Thus, selecting the reefer vehicle is a complex decision-making problem and selecting appropriate reefer vehicles may have a critical role in constructing successful supply chain systems and reducing food waste and loss. The current research proposes an efficient, robust and practical decision-making framework that can overcome uncertainties to tackle this decision-making problem. The managerial and strategic implications of the study also aid in decreasing FLW and restructuring FSC for industrial context and support to the UN's sustainable development goals (SDGs). Later, an exhaustive sensitivity analysis was conducted to examine the developed model's validity and application, confirming the model's robustness and dependability.
Citation - WoS: 3
Citation - Scopus: 3
Markdown Optimization in Apparel Retail Sector
(Springer international Publishing Ag, 2020) Yildiz, Sevde Ceren; Hekimoglu, Mustafa
Price discounts, known as markdowns, are important for fast fashion retailers to utilize inventory in a distribution channel using demand management. Estimating future demand for a given discount level requires the evaluation of historical sales data. In this evaluation recent observations might be more important than the older ones as majority of price discounts take place at the end of a selling season and that time period provides more accurate estimations. In this study, we consider a weighted least squares method for the parameter estimation of an empirical demand model used in a markdown optimization system. We suggest a heuristic procedure for the implementation of weighted least squares in a markdown optimization utilizing a generic weight function from the literature. We tested the suggested system using empirical data from a Turkish apparel retailer. Our results indicate that the weighted least squaresmethod is more proper than the ordinary least squares for the fast fashion sales data as it captures price sensitivity of demand at the end of a selling season more accurately.
Citation - WoS: 10
Citation - Scopus: 9
Viewpoint: Historic Urban Landscape Approach for Sustainable Urban Development
(Routledge Journals Taylor & Francis Ltd, 2018) Erkan Kösebay, Yonca
[Abstract Not Available]
Citation - WoS: 17
Citation - Scopus: 16
Hyperuricemia in hypothyroidism: Is it associated with post-insulin infusion glycemic response?
(Tohoku Univ Medical Press, 2003) Dariyerli, Nuran; Andican, Gülnur; Çatakoğlu, Alp Burak; Hatemi, Hüsrev; Burçak, Gülden
This experimental study was designed to examine whether hyperuricemia in hypothyroidism is associated with insulin resistance. For induction of hypothyroidism rabbits (n = 12) were administered methimazole orally (75 mg/100 g food) for 30 days. T-3 T-4 and TSH values measured in plasma prior to and at the end of the experimentation period revealed the establishment of hypothyroidism. In the euthyroid and hypothyroid states of rabbits crystalline porcine insulin was administered (0.1 unit/kg body weight) intraperitoneally and plasma glucose was measured at 0 15 30 45 and 60 minutes. Sum of post insulin infusion glucose values was considered to reflect insulin resistance. Creatinine clearance (GFR) and uric acid clearance (C-uA) were determined. Additionally triglycerides were measured in plasma and Mg2+ both in erythrocytes and in plasma. Due to hypothyroidism: i) The glycemic response to insulin was not altered. ii) GFR and C-uA were both decreased but C-uA/GFR unchanged. iii) Triglycerides in plasma decreased. iv) Mg2+ concentration increased in plasma whereas decreased in erythrocytes. Several associations were observed between the variables on correlation analysis. On the basis of our data it could be suggested that insulin resistance does not exist in hypothyroidism. Hyperuricemia observed in hypothyroidism should be considered to be secondary to decreased renal excretion but not as an indicator of insulin resistance. (C) 2003 Tohoku University Medical Press.
Citation - WoS: 5
Citation - Scopus: 6
Effect of Lcst on the Swelling of Paam-Nipa Copolymers: a Fluorescence Study
(Springer, 2012) Evingür, Gülşen Akin; Pekcan, Önder
Temperature sensitive copolymers were prepared by free radical crosslinking copolymerization in aqueous solution with different molar percentage of N-isopropylacrylamide (NIPA) and acrylamide (AAm) monomers. NN'-methylenebis (acrylamide) (BIS) and ammonium persulfate (APS) were used as a crosslinker and an initiator respectively. The steady-state fluorescence (SSF) technique was used to determine the low critical phase transition temperature (LCST) for PAAm-NIPA copolymers. Swelling experiments were performed in water at various temperatures by real time monitoring of pyranine (Py) fluorescence intensity I which decreased as swelling proceeded. The Stern-Volmer equation is modified for low quenching efficiencies to interpret the behavior of pyranine intensity during the swelling of PAAm-NIPA copolymers. The Li-Tanaka equation was used to determine the swelling time constants tau (1) and the cooperative diffusion coefficients D (0) from fluorescence intensity weight and volume variations of the copolymers at various temperatures. It was observed that tau (1) first increased up to LCST and then decreased
Citation - Scopus: 1
Multi-Agent Model of Electricity Networks - a Perspective on Distribution Network Charges
(Institute of Electrical and Electronics Engineers Inc., 2019) Pisica, Ioana; Ceylan, Oğuzhan
In the UK, DNOs are regulated by Ofgem to use two common distribution use of system charging methodologies: Common Distribution Charging Methodology and Extra-High Voltage Distribution Charging Methodology. To account for the changing landscape of the energy sector, Ofgem has recently published a consultation paper on changes to DUoS charging structure. This paper looks into the implications of distribution network charging in consumer-level adoption of low carbon technologies and vice-versa, using an agent-based model approach.
Citation - WoS: 4
Citation - Scopus: 7
Atomic Force Microscopy and Spectroscopy Studies of Annealed Ce/Ti Mixed Oxide Thin Films Prepared by Sol-Gel Process
(Elsevier Science Bv, 2006) Ghodsi, Farhad E.; Tepehan, Fatma Zehra; Tepehan, Galip Gültekin
Mixed Ce/Ti/Zr oxide thin films with a molar ratio of 0.5:0.25:0.25 were prepared using the sol-gel process and deposited on glass substrates by the dip coating technique. The effect of heat treatment temperature on surface morphology of the films was examined by atomic force microscopy AFM. The optical transmittance and reflectance of the films were measured over the spectral range from 350 to 1000 nm. The refractive index and extinction coefficient and thickness of the films were determined as a function of the heat treatment temperature. The refractive index increased from 1.51 to 2.02 at lambda = 600 nm and the extinction coefficient values increased from 0.006 to 0.094 while the thickness of the films decreased from 81 nm to 45 nm when annealing temperature increased from 100 degrees C to 500 degrees C. The results show that the optical properties and surface morphology of the mixed Cc/Ti/Zr oxide thin films were affected by annealing temperature. (c) 2006 Elsevier B.V. All rights reserved.
Citation - WoS: 2
Citation - Scopus: 5
Performance of Space-Time Coded Systems With Transmit Antenna Selection
(IEEE, 2007) Güçlüoğlu, Tansal; Duman, Tolga M.
We deal with transmit antenna selection for space-time coded (STC) systems over multiple input multiple output (MIMO) channels. Using pairwise error probability analysis and simulation results we show that transmit antenna selection based on received power levels does not reduce the achievable diversity order for full rank STCs. Initially we prove the results for Rayleigh flat fading channels and then we state our expectations for the case of frequency selective (FS) fading. In addition to the study of full rank codes we also consider rank deficient space-time codes and determine achievable diversity orders with transmit antenna selection.
Citation - WoS: 27
Citation - Scopus: 32
A Fuzzy-Based Method for Objects Selection in Blockchain-Enabled Edge-Iot Platforms Using a Hybrid Multi-Criteria Decision-Making Model
(Mdpi, 2022) Gardas, Bhaskar B.; Heidari, Arash; Navimipour, Nima Jafari; Unal, Mehmet
The broad availability of connected and intelligent devices has increased the demand for Internet of Things (IoT) applications that require more intense data storage and processing. However, cloud-based IoT systems are typically located far from end-users and face several issues, including high cloud server load, slow response times, and a lack of global mobility. Some of these flaws can be addressed with edge computing. In addition, node selection helps avoid common difficulties related to IoT, including network lifespan, allocation of resources, and trust in the acquired data by selecting the correct nodes at a suitable period. On the other hand, the IoT's interconnection of edge and blockchain technologies gives a fresh perspective on access control framework design. This article provides a novel node selection approach for blockchain-enabled edge IoT that provides a quick and dependable node selection. Moreover, fuzzy logic to approximation logic was used to manage numerical and linguistic data simultaneously. In addition, the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), a powerful tool for examining Multi-Criteria Decision-Making (MCDM) problems, is used. The suggested fuzzy-based technique employs three input criteria to select the correct IoT node for a given mission in IoT-edge situations. The outcomes of the experiments indicate that the proposed framework enhances the parameters under consideration.
Citation - WoS: 1
Citation - Scopus: 1
A Possible Transformation of Tourism Education: A Chaos Theory Perspective
(Elsevier Sci Ltd, 2024) Kirlar-Can, Burcin; Ertas, Mehmet; Kozak, Metin; Altinay, Levent
Recently, there has been a likely transformation from traditional face-to-face education to distance education and hybrid models. Higher tourism education has undergone these changes concordantly as it incorporates an applied field. Therefore, an atmosphere of uncertainty and chaos has arisen in universities. The study approaches the effects of the pandemic on the education system through the perspective of chaos theory. The data were collected from tourism academics, one of the pillars of the higher education system. Semi-structured in-depth interviews were conducted with 21 lecturers. Study findings revealed that the lack of compulsory attendance reduced student participation in online classes. Accordingly, low student attendance resulted in the lack of lecturer-student interaction in courses, negatively impacting lecturer motivation and highlighting the inefficiency of distance education. The study also provides clues regarding differences and managerial implications experienced by public and foundation universities during the pandemic.
Citation - WoS: 34
Citation - Scopus: 32
Effect of Intracellular Loop 3 on Intrinsic Dynamics of Human 2-Adrenergic Receptor
(Bmc, 2013) Ozcan, Ozer; Uyar, Arzu; Doruker, Pemra; Akten, Ebru Demet
Background: To understand the effect of the long intracellular loop 3 (ICL3) on the intrinsic dynamics of human beta(2)-adrenergic receptor, molecular dynamics (MD) simulations were performed on two different models, both of which were based on the inactive crystal structure in complex with carazolol (after removal of carazolol and T4-lysozyme). In the so-called loop model, the ICL3 region that is missing in available crystal structures was modeled as an unstructured loop of 32-residues length, whereas in the clipped model, the two open ends were covalently bonded to each other. The latter model without ICL3 was taken as a reference, which has also been commonly used in recent computational studies. Each model was embedded into POPC bilayer membrane with explicit water and subjected to a 1 mu s molecular dynamics (MD) simulation at 310 K. Results: After around 600 ns, the loop model started a transition to a very inactive conformation, which is characterized by a further movement of the intracellular half of transmembrane helix 6 (TM6) towards the receptor core, and a close packing of ICL3 underneath the membrane completely blocking the G-protein's binding site. Concurrently, the binding site at the extracellular part of the receptor expanded slightly with the Ser207-Asp113 distance increasing to 18 angstrom from 11 angstrom, which was further elaborated by docking studies. Conclusions: The essential dynamics analysis indicated a strong coupling between the extracellular and intracellular parts of the intact receptor, implicating a functional relevance for allosteric regulation. In contrast, no such transition to the very inactive state, nor any structural correlation, was observed in the clipped model without ICL3. Furthermore, elastic network analysis using different conformers for the loop model indicated a consistent picture on the specific ICL3 conformational change being driven by global modes.
Citation - WoS: 2
Citation - Scopus: 2
Anomalous Pancreaticobiliary Junction (apbj) With the Drainage of the Uncinate Process Into the Minor Papilla: Demonstration by Mri
(BRITISH INST RADIOLOGY, 2005) Başaranoğlu, Metin; Balcı, Numan Cem; Kloer, Hans Ulrich
We report a case of a 30-year-old patient with anomalous pancreaticobiliary junction (APBJ) that has not been described before. The patient had a clinical history of recurrent attacks of pancreatitis cholangitis and cholecystitis that were confirmed by abnormal laboratory values. Endoscopic retrograde cholangiopancreatography revealed a 20 mm long junction of choledoc and pancreatic duct and uncinate process draining into the minor papilla. On MR cholangiopancreatography strictures at the junction of hepatic duct increased gallbladder wall thickness and intraductal stone in the pancreatic duct were demonstrated as complementary findings. Other MRI findings included decreased signal intensity of the pancreas consistent with fibrosis from past pancreatitis attacks and atrophy of the left liver lobe.
Citation - WoS: 22
Citation - Scopus: 22
Gelation Mechanisms
(World Scientific Publ Co Pte Ltd, 2012) Pekcan, Önder; Kara, Selim
In this paper, we survey the gelation mechanisms for various polymeric systems which are classified by the type and the strength of the cross-linkages. These are the "irreversible" gels that are cross-linked chemically by covalent bonds and the "reversible" gels that are cross-linked physically by hydrogen or ionic bonds and by the physical entanglement of polymer chains. Some of the natural polymer gels fall into the class of physical gels, among which the red algae that has attracted attention for various applications is discussed in detail. Various composite gels, formed from mixture of physical and chemical gels are also discussed in the last section of the article. Theoretical models describe the gelation as a process of random linking of subunits to larger and larger molecules by formation of an infinite network, where no matter what type of objects are linked, there is always a critical "gel point" at which the system behaves neither as a liquid nor as a solid on any length scale. The Flory-Stockmayer theory and percolation theory provide bases for modeling this sol-gel phase transition. The experimental techniques for measuring the critical exponents for sol-gel phase transitions in different polymeric systems are introduced and the validation of various theoretical predictions are surveyed.

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