88 research outputs found
Modeling of carbon credit prices using regime switching approach
No full textSemra Ağralı (MEF Author)In this study, we analyze the price dynamics of carbon certificates that are traded under the European Union's Emissions Trading System (EU-ETS). With the aim of investigating the joint relations among carbon, electricity, and fuel prices, we model historical prices using several methods and incorporating structural changes, such as econometric time series, regime switching, and multivariate vector autoregression models. We compare the results of the structural model with the results of traditional Markov switching and autoregressive models with breaks and present performance analysis based on the mean average percentage error, root mean squared error, and coefficient of determination. According to these performance tests, models with regimes outperform the approaches where breaks are defined using ex ante dummy variables. Moreover, we conclude that among regime switching models, univariate models are better than multivariate counterparts for modeling carbon price series for the analysis of both in-sample and out-of-samples. Published by AIP Publishing.WOS:0004372803000422-s2.0-85049234517Science Citation Index Expanded - Social Sciences Citation IndexArticleUluslararası işbirliği ile yapılmayan - HAYIRMayısYÖK - 2017-1
Nonlinear benefit-cost optimization-based selection of insulation material and window type: A case study in Turkey
No full textSemra Ağralı (MEF Author)In this study, we maximize the energy savings of a hypothetical household by choosing an optimal insulation material with its optimal thickness and also the optimal window type. We develop a nonlinear mixed integer optimization model that maximizes the net present value of the benefits obtained by insulation over the lifespan of the house. Savings are calculated based on the gains from the electricity usage for air conditioning during cooling-required days and the fuel usage for heaters in heating-required days. The heat transfer calculations consider conductive, convective, and radiative components simultaneously. The optimization model takes the climate conditions of the region where the house is located, the consumer's desired indoor temperature, and the properties of the insulation options; then, it returns a combination of selected insulation materials with its optimum thickness and window type as output. We applied the optimization model developed to hypothetical houses in four different climatic regions of Turkey for different lifespans. For all reasonable lifespans, the model choses stonewool as the ideal insulation material. For high interest rates, single windows or double-glazed windows are preferable, but as the interest rate decreases and the net present value of the energy-savings increases, the model prefers triple-glazed windows as the ideal material. Erzurum, a city in climatic region 4, characterized by very cold winters and cool summers, was found to require the highest optimum insulation thickness, and the economic return resulting from the above-mentioned energy-saving actions was also found to be the highest in the case of Erzurum. In all the regions, the energy-saving investments were found to be feasible via applying the feasibility assessment techniques of net present value and payback period. The model developed in this study is applicable to any household as long as the required input data are available. Published by AIP Publishing.WOS:0004190002000332-s2.0-85038567088Science Citation Index ExpandedArticleUluslararası işbirliği ile yapılmayan - HAYIRKasımYÖK - 2017-1
Energy Investment Planning at a Private Company: A Mathematical Programming-Based Model and Its Application in Turkey
No full textSemra Ağralı (MEF Author)We consider a mid-sized private electricity generating company that plans to enter the market that is partially regulated. There is a cap and trade system in operation in the industry. There are nine possible power plant types that the company considers to invest on through a planning horizon. Some of these plants may include a carbon capture and storage technology. We develop a stochastic mixed-integer linear program for this problem where the objective is to maximize the expected net present value of the profit obtained. We include restrictions on the maximum and minimum possible amount of investment for every type of investment option. We also enforce market share conditions such that the percentage of the total investments of the company over the total installed capacity of the country stay between upper and lower bounds. Moreover, in order to distribute the investment risk, the percentage of each type of power plant investment is restricted by some upper bound. We tested the model for a hypothetical company operating in Turkey. The results show that the model is suitable to be used for determining the investment strategy of the company.WOS:0004132478000032-s2.0-85037056874Science Citation Index Expanded - Social Sciences Citation IndexArticleUluslararası işbirliği ile yapılmayan - HAYIRKasımYÖK - 2017-1
An optimization model for carbon capture & storage/utilization vs. carbon trading: A case study of fossil-fired power plants in Turkey
No full textSemra Ağralı (MEF Author)We consider fossil-fired power plants that operate in an environment where a cap and trade system is in operation. These plants need to choose between carbon capture and storage (CCS), carbon capture and utilization (CCU), or carbon trading in order to obey emissions limits enforced by the government. We develop a mixed-integer programming model that decides on the capacities of carbon capture units, if it is optimal to install them, the transportation network that needs to be built for transporting the carbon captured, and the locations of storage sites, if they are decided to be built. Main restrictions on the system are the minimum and maximum capacities of the different parts of the pipeline network, the amount of carbon that can be sold to companies for utilization, and the capacities on the storage sites. Under these restrictions, the model aims to minimize the net present value of the sum of the costs associated with installation and operation of the carbon capture unit and the transportation of carbon, the storage cost in case of CCS, the cost (or revenue) that results from the emissions trading system, and finally the negative revenue of selling the carbon to other entities for utilization. We implement the model on General Algebraic Modeling System (GAMS) by using data associated with two coal-fired power plants located in different regions of Turkey. We choose enhanced oil recovery (EOR) as the process in which carbon would be utilized. The results show that CCU is preferable to CCS as long as there is sufficient demand in the EOR market. The distance between the location of emission and location of utilization/storage, and the capacity limits on the pipes are an important factor in deciding between carbon capture and carbon trading. At carbon prices over $15/ton, carbon capture becomes preferable to carbon trading. These results show that as far as Turkey is concerned, CCU should be prioritized as a means of reducing nationwide carbon emissions in an environmentally and economically rewarding manner. The model developed in this study is generic, and it can be applied to any industry at any location, as long as the required inputs are available. (C) 2018 Elsevier Ltd. All rights reserved.WOS:0004307847000312-s2.0-8504410277029574208Science Citation Index ExpandedArticleUluslararası işbirliği ile yapılmayan - HAYIRHaziranYÖK - 2017-1
Examination of influential observations in penalized spline regression
No full textIn parametric or nonparametric regression models, the results of regression analysis are affected by some anomalous observations in the data set. Thus, detection of these observations is one of the major steps in regression analysis. These observations are precisely detected by well-known influence measures. Pena's statistic is one of them. In this study, Pena's approach is formulated for penalized spline regression in terms of ordinary residuals and leverages. The real data and artificial data are used to see illustrate the effectiveness of Pena's statistic as to Cook's distance on detecting influential observations. The results of the study clearly reveal that the proposed measure is superior to Cook's Distance to detect these observations in large data set
Semra Ertan - Word and Body as Instruments of Socio-Political Protest
No full textThe bachelor thesis is dedicated to Semra Ertan, a poet and activist of Turkish origin, who lived since the 1970s with her parents in Germany, who worked there as guest workers (Gastarbeiter). In 1982, Ertan publicly set herself on fire in Hamburg. Although the publication of her poetry collection in 2020 aroused interest in both Germany and Turkey in her work and life's destiny, academic research is still lacking. The thesis aims to present the person and work of Semra Ertan as a topic that has not yet been researched. The student will first outline the development of the situation of the Turkish guest workers in Germany since the bilateral agreement between Germany and Turkey, introduce the author herself, and in the main part of the thesis will analyze her poems as such and the relationship between Semra Ertan's poems and her self-immolation. Thesis will try to answer the question of whether and how aspects of the author's life can be seen in her poems. To answer this question, in addition to the thematic analysis of the poems the approaches of the social contextual studies of literature as outlined by Josef Šebek will be used.Bakalářská práce je věnována Semře Ertan, básnířce a aktivistce tureckého původu, která žila od sedmdesátých let 20. století s rodiči v Německu, kteří zde pracovali jako hostující dělníci (Gastarbeiter). V roce 1982 se Ertan v Hamburku veřejně upálila. Přestože vydání její básnické sbírky v roce 2020 vzbudilo v Německu i v Turecku zájem o její tvorbu i životní osudy, odborné zpracování dosud chybí. Práce si klade za cíl představit osobu a dílo Semry Ertan jakožto téma v akademickém prostředí doposud nezpracované. Studentka nejprve nastíní vývoj situace tureckých pracovních sil v Německu od uzavření bilaterální smlouvy mezi SRN a Tureckem, představí samotnou autorku a v hlavní části práce pak bude analyzovat její básně jako takové a také vztah mezi básněmi Semry Ertan a jejím sebeupálením. Pokusí se odpovědět na otázku, zda a jakým způsobem lze v básních spatřovat aspekty autorčina života. K zodpovězení této otázky bude vedle tematické analýzy básní využívat přístupy sociálně kontextového studia literatury, jak je nastiňuje Josef Šebek.Department of Middle Eastern StudiesKatedra Blízkého východuFilozofická fakultaFaculty of Art
Determinants Of Electricity Consumption Based On The Nuts 2 Regions Of Turkey: A Panel Data Approach
No full textPrevious studies have focused on the relationship in recent years between electricity consumption and socio-economic indicators, but little attention has been paid to regional differences in Turkey. This study determines the electricity consumption indicators of Turkey based on the Nomenclature of Territorial Units for Statistics (NUTS 2) regions during 2004-2011. To achieve this objective, panel data regression models, including socioeconomic indicators (gross value added, and import and export amounts) were developed. The study represents the first instance of regional knowledge for electricity consumption using the panel data approach. The empirical results show that electricity consumption for the NUTS 2 regions can be modelled using fixed effects models with standard errors obtained by the White estimator. The study reveals that regional development leads to increases in electricity consumption. Furthermore, electricity demand has grown impressively in line with regional economic developments in Turkey.Wo
Evaluation of Cytotoxicity and Mutagenicity of Wastewater from Istanbul: Data from Hospitals and Advanced Wastewater Treatment Plant
No full textWastewater (WW) carry considerable amount of chemicals that could have mutagenic or cytotoxic effect from hospital discharges to aquatic environment. Our objective was to determinate the possible mutagenic and toxic effects of hospital originated WWs and effectiveness of the wastewater treatment plants (WTP) functions. In the study the mutagenic and cytotoxic potential of three hospitals and influent/effluent of a treatment plant WW collected in Istanbul and was examined using AMES, XTT, and lactate dehydrogenase (LDH) assays. Mutagenic effects were detected at both hospital discharges and advanced biological wastewater plant. We observed no cytotoxic effect in fibroblasts for LDH and XTT assays whereas high cytotoxicity for all samples was found in hepatocytes by XTT assay. According to the results even if advanced technology is used for treatment of WW, mutagenic and cytotoxic effects still remain, and the present technologies need to be further improved
The Efficiency Analysis of Non-life Insurance Companies Active in Turkey
No full textThis paper evaluates the technical effi ciencies of non-life insurance companies, which are active in Turkey in 2007, using Data Envelopment Analysis (DEA). DEA, which is a nonparametric method, facilitates to examine different input-output components. DEA is a
management evaluation tool that assists in identifying the most efficient and ineffi cient decision making units (DMUs) in the best practice frontier. In this study, as inputs of 23 non-life insurance companies, the number of agents, the number of brokers, fi xed assets,
shareholders’ equity and as outputs the investment incomes, premiums received are used. Empirical results of BCC and CCR models, which are DEA models, show that the most efficient insurance company is RAY
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