Browsing by Subject "Commerce"

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1970'ten itibarenTürkiye'nin fındık üretimi ve ihracatı
(Bilkent University, 2018) Kurucu, Mehmet Bora; Akçakuş, Didem; Akgün, Ela Nur; Elmas, İbrahim; Özkan, Selen
Bu araştırma, Türkiye’deki 1970 yılından 2000 yılına kadar gerçekleşen fındık ihracatını ve üretimini konu almaktadır. Araştırmada fındık ihracatı ve üretimi ile ilgili istatistikler sunuldu, aynı zamanda birçok farklı açıdan ele alınıp yorumlandı. örneğin Türkiye 1980 öncesi dönemde ihracat konusunda içe dönük bir politika izlerken, 1980 sonrasında ise fındık ihracatına verdiği önemi büyük oranda arttırmış ve yabancı ülkelere mal satımını arttırmıştır. Bu ve bunu gibi bunun gibi değişimlerin sebepleri ve analizleri araştırmanın temeli olmuştur.
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Ankara'nın yerel markası: Seğmen Reçelleri (1938-)
(Bilkent University, 2018) Arslanboğa, Gizem; Emecan, Ali Galip; Güven, Ceren; Özyurt, Barkın; Yaman, Şevval
1938 yılında Seğmen ailesinin Eskişehir Sivrihisar’dan Ankara’ya göç etmesiyle bakkal olarak ticari hayata adım atan Seğmen Kardeşler A.ş. günümüze kadar gelişimini devam ettiren bir markadır. Cumhuriyet tarihine paralel olarak gelişen Seğmen, zaman içerisinde reçel, bal gibi ürünlerin evlerden çıkarak fabrikalarda üretilmesinin ve teknolojinin gelişmesiyle farklı teknikler uygulayarak bu ürünlerin çeşitlendirilmesinin öncülerinden biri olmuştur. Bu projede hayatta olan son kurucu dahil şirket bünyesindeki toplam dört üst düzey yönetici ile görüşülerek ve şirket arşivi ayrıntılı olarak incelenerek gerekli doküman ve fotoğraflar temin edilmiştir. Toplanılan verilere dayanarak Seğmen Reçelleri’nin kuruluş ve gelişim aşamaları, Ankara’nın ticaret hayatına katkıları, aile şirketi olmasının önemi, şirketin günümüzdeki hali ve yurtdışındaki ekonomik ilişkileri anlatılmıştır. Bu yazı aynı zamanda Seğmen’in kurulduğu yıllarda Ankara’daki yaşamı ve tatlı sektöründeki gelişimi göstermektedir.
Open Access
Bidding structure, market efficiency and persistence in a multi-time tariff setting
(Elsevier, 2016) Avci-Surucu, E.; Aydogan, A. K.; Akgul, D.
The purpose of this study is to examine the fractal dynamics of day ahead electricity prices by using parametric and semi parametric approaches for each time zone in a multi-time tariff setting in the framework of bidding strategies, market efficiency and persistence of exogenous shocks. We find that that electricity prices have long term correlation structure for the first and third time zones indicating that market participants bid hyperbolically and not at their marginal costs, market is not weak form efficient at these hours and exogenous shocks to change the mean level of prices will have permanent effect and be effective. On the other hand, for the second time zone we find that price series does not exhibit long term memory. This finding suggests the weak form efficiency of the market in these hours and that market participants bid at their marginal costs. Furthermore this indicates that exogenous shocks will have temporary effect on electricity prices in these hours. These findings constitute an important foundation for policy makers and market participants to develop appropriate electricity price forecasting tools, market monitoring indexes and to conduct ex-ante impact assessment.
Open Access
A catalog of stream processing optimizations
(Association for Computing Machinery, 2014) Hirzel M.; Soulé R.; Schneider S.; Gedik, B.; Grimm, R.
Various research communities have independently arrived at stream processing as a programming model for efficient and parallel computing. These communities include digital signal processing, databases, operating systems, and complex event processing. Since each community faces applications with challenging performance requirements, each of them has developed some of the same optimizations, but often with conflicting terminology and unstated assumptions. This article presents a survey of optimizations for stream processing. It is aimed both at users who need to understand and guide the system's optimizer and at implementers who need to make engineering tradeoffs. To consolidate terminology, this article is organized as a catalog, in a style similar to catalogs of design patterns or refactorings. To make assumptions explicit and help understand tradeoffs, each optimization is presented with its safety constraints (when does it preserve correctness?) and a profitability experiment (when does it improve performance?). We hope that this survey will help future streaming system builders to stand on the shoulders of giants from not just their own community. © 2014 ACM.
Open Access
Discrete time/cost trade-off problem: a decomposition-based solution algorithm for the budget version
(Pergamon Press, 2010-04) Hazır, O.; Haouari, M.; Erel, E.
This paper investigates the budget variant of the discrete time/cost trade-off problem (DTCTP). This multi-mode project scheduling problem requires assigning modes to the activities of a project so that the total completion time is minimized and the budget and the precedence constraints are satisfied. This problem is often encountered in practice as timely completion of the projects without exceeding the budget is crucial. The contribution of this paper to the literatures is to describe an effective Benders Decomposition-based exact algorithm to solve the DTCTP instances of realistic sizes. Although Benders Decomposition often exhibits a very slow convergence, we have included several algorithmic features to enhance the performance of the proposed tailored approach. Computational results attest to the efficacy of the proposed algorithm, which can solve large-scale instances to optimality.
Open Access
Discrimination against teenagers in the mall environment: a case from Ankara, Turkey
(Libra Publishers, 2009-02) Mugan, G.; Erkip, F.
Teenagers spend much of their leisure time at shopping malls which is a result of factors such as parental constraint due to the incivility of the streets, financial dependence, and limited financial resources. Migros, a shopping mall in Ankara was chosen as the sit for this research wiht the main purpose of studying discrimination patterns against teenagers in the mall environment. The research was carried out through observation and in-depth interviews with 104 teenagers. Results indicate that, although they have some complaints, most of the teenagers do not perceive discrimination in the mall, unlike their foreign counterparts.
Open Access
Dynamic risk spillovers between gold, oil prices and conventional, sustainability and Islamic equity aggregates and sectors with portfolio implications
(Elsevier B.V., 2017) Mensi, W.; Hammoudeh, S.; Al-Jarrah, I. M. W.; Sensoy A.; Kang, S. H.
This paper investigates the time-varying equicorrelations and risk spillovers between crude oil, gold and the Dow Jones conventional, sustainability and Islamic stock index aggregates and 10 associated disaggregated Islamic sector stock indexes (basic materials, consumer services, consumer goods, energy, financials, health care, technology, industrials, telecommunications and utilities), using the multivariate DECO-FIAPARCH model and the spillover index of Diebold and Yilmaz (2012). We also conduct a risk management analysis at the sector level for commodity-Islamic stock sector index portfolios, using different risk exposure measures. For comparison purposes, we add the aggregate conventional Dow Jones global index and the Dow Jones sustainability world index. The results show evidence of time-varying risk spillovers between these markets. Moreover, there are increases in the correlations among the markets in the aftermath of the 2008–2009 GFC. Further, the oil, gold, energy, financial, technology and telecommunications sectors are net receivers of risk spillovers, while the sustainability and conventional aggregate DJIM indexes as well as the remaining Islamic stock sectors are net contributors of risk spillovers. Finally, we provide evidence that gold offers better portfolio diversification benefits and downside risk reductions than oil. © 2017 Elsevier B.V.
Open Access
Examining proactive strategic decision-making flexibility in new product development
(Wiley-Blackwell Publishing, 2012) Kandemir, D.; Acur, N.
While strategic flexibility is widely accepted as a prerequisite for a firm's success, its application in strategic decision making to a firm's new product development (NPD) activities is limited to only a few studies. Furthermore, many organizations still have difficulties creating proactive strategic flexibility in their decision-making processes. Past research studies have largely ignored the relationship between strategic decision-making flexibility and firms' resources and/or capabilities and success in the context of NPD. This study advances strategic flexibility by adopting the proactive approach of NPD decision-making flexibility and by examining its role in translating organizational resources and capabilities into NPD success. This study draws upon the resources, capabilities (i.e., flexibility), and performance framework to show how proactive strategic decision-making flexibility plays a crucial role in developing new products that can create new opportunities and comply with market needs. Therefore, this research aims to (1) develop an operational definition of strategic decision-making flexibility and (2) propose a framework to understand the drivers and the subsequent new product performance outcomes of strategic decision-making flexibility. This study adopts the proactive perspective of strategic decision-making flexibility and defines it as a capability that enables firms to develop NPD strategies to respond to future changes in the environment. The analysis, based on data collected from 103 European firms, shows that that the effects of long-term orientation, strategic planning, internal commitment, and innovative climate on proactive strategic decision-making flexibility are significant. The findings indicate specifically the roles of both champions and gatekeepers, who infuse a firm's knowledge with a clear understanding of its resources, constraints, and market needs, thereby enhancing decision makers' motivation to behave proactively to precipitate transformation. The results also reveal a positive association between proactive strategic decision-making flexibility and NPD performance outcomes. As such, strategic flexibility provides firms with an ability to adapt to changing environments and to create new market opportunities, product, and technological arenas, and to deliver successful new products. When firms open new market, technological, and product arenas, they can easily foresee their new demands and changes and successfully deliver new products, meeting customer needs/demands, and offering benefits such as quality, cost, and timeliness. This study therefore provides a valuable reference point for future research in strategic decision-making flexibility in NPD.
Open Access
Expected gain-loss pricing and hedging of contingent claims in incomplete markets by linear programming
(Elsevier, 2010) Pınar, M. Ç.; Salih, A.; Camcı, A.
We analyze the problem of pricing and hedging contingent claims in the multi-period, discrete time, discrete state case using the concept of a "λ gain-loss ratio opportunity". Pricing results somewhat different from, but reminiscent of, the arbitrage pricing theorems of mathematical finance are obtained. Our analysis provides tighter price bounds on the contingent claim in an incomplete market, which may converge to a unique price for a specific value of a gain-loss preference parameter imposed by the market while the hedging policies may be different for different sides of the same trade. The results are obtained in the simpler framework of stochastic linear programming in a multi-period setting, and have the appealing feature of being very simple to derive and to articulate even for the non-specialist. They also extend to markets with transaction costs.
Open Access
Generalized Hurst exponent approach to efficiency in MENA markets
(Elsevir BV, 2013) Sensoy, A.
We study the time-varying efficiency of 15 Middle East and North African (MENA) stock markets by generalized Hurst exponent analysis of daily data with a rolling window technique. The study covers a time period of six years from January 2007 to December 2012. The results reveal that all MENA stock markets exhibit different degrees of long-range dependence varying over time and that the Arab Spring has had a negative effect on market efficiency in the region. The least inefficient market is found to be Turkey, followed by Israel, while the most inefficient markets are Iran, Tunisia, and UAE. Turkey and Israel show characteristics of developed financial markets. Reasons and implications are discussed.
Open Access
Growth optimal investment with threshold rebalancing portfolios under transaction costs
(IEEE, 2013) Tunc, S.; Donmez, M.A.; Kozat, Süleyman S.
We study how to invest optimally in a stock market having a finite number of assets from a signal processing perspective. In particular, we introduce a portfolio selection algorithm that maximizes the expected cumulative wealth in i.i.d. two-asset discrete-time markets where the market levies proportional transaction costs in buying and selling stocks. This is achieved by using 'threshold rebalanced portfolios', where trading occurs only if the portfolio breaches certain thresholds. Under the assumption that the relative price sequences have log-normal distribution from the Black-Scholes model, we evaluate the expected wealth under proportional transaction costs and find the threshold rebalanced portfolio that achieves the maximal expected cumulative wealth over any investment period. © 2013 IEEE.
Open Access
Hub location under competition
(Elsevier, 2016) Mahmutogullari, A. I.; Kara, B. Y.
Hubs are consolidation and dissemination points in many-to-many flow networks. Hub location problem is to locate hubs among available nodes and allocate non-hub nodes to these hubs. The mainstream hub location studies focus on optimal decisions of one decision-maker with respect to some objective(s) even though the markets that benefit hubbing are oligopolies. Therefore, in this paper, we propose a competitive hub location problem where the market is assumed to be a duopoly. Two decision-makers (or firms) sequentially decide locations of their hubs and then customers choose one firm with respect to provided service levels. Each decision-maker aims to maximize his/her own market share. We propose two problems for the leader (former decision-maker) and follower (latter decision-maker): (r|Xp)hub − medianoid and (r|p)hub − centroid problems, respectively. Both problems are proven to be NP-complete. Linear programming models are presented for these problems as well as exact solution algorithms for the (r|p)hub − centroid problem. The performance of models and algorithms are tested by computational analysis conducted on CAB and TR data sets.
Open Access
Mixed-integer second-order cone programming for lower hedging of American contingent claims in incomplete markets
(2013) Pınar, M. Ç.
We describe a challenging class of large mixed-integer second-order cone programming models which arise in computing the maximum price that a buyer is willing to disburse to acquire an American contingent claim in an incomplete financial market with no arbitrage opportunity. Taking the viewpoint of an investor who is willing to allow a controlled amount of risk by replacing the classical no-arbitrage assumption with a "no good-deal assumption" defined using an arbitrage-adjusted Sharpe ratio criterion we formulate the problem of computing the pricing and hedging of an American option in a financial market described by a multi-period, discrete-time, finite-state scenario tree as a large-scale mixed-integer conic optimization problem. We report computational results with off-the-shelf mixed-integer conic optimization software.
Open Access
News releases and stock market volatility: intraday evidence from borsa Istanbul
(Elsevier Inc., 2015) Solakoglu, M. N.; Demir, N.
In this study, we investigate the effect of public information arrival on return volatility for Borsa Istanbul (BIST) using intraday, 60-min returns between October 3, 2013 and March 31, 2014. Stock return and return volatility is expected to react to news arrival if such news causes market participants to adjust their portfolios. To measure new information arrival, we count the number of daily news headlines for Turkey, the United States, and a sample of European countries with close trading ties with Turkey. Furthermore, we focus on economic news and particularly on news on real economy and inflation. In addition, along with the BIST100 index, which is the most commonly used market portfolio index, we also utilize Second National Market (SNM) index. Our results show that news arrival influences return volatility negatively, and it has no significant effect on index returns. Moreover, return volatility responds significantly to negative surprises in GDP and inflation announcements. Finally, we do not provide evidence that indicates differences in the usage of information that arrives to the market between BIST100 and SNM investors. © 2015 Elsevier Inc. All rights reserved.
Open Access
Optimal investment under transaction costs: A threshold rebalanced portfolio approach
(IEEE, 2013) Tunc, S.; Donmez, M. A.; Kozat, S. S.
We study how to invest optimally in a financial market having a finite number of assets from a signal processing perspective. Specifically, we investigate how an investor should distribute capital over these assets and when he/she should reallocate the distribution of the funds over these assets to maximize the expected cumulative wealth over any investment period. In particular, we introduce a portfolio selection algorithm that maximizes the expected cumulative wealth in i.i.d. two-asset discrete-time markets where the market levies proportional transaction costs in buying and selling stocks. We achieve this using 'threshold rebalanced portfolios', where trading occurs only if the portfolio breaches certain thresholds. Under the assumption that the relative price sequences have log-normal distribution from the Black-Scholes model, we evaluate the expected wealth under proportional transaction costs and find the threshold rebalanced portfolio that achieves the maximal expected cumulative wealth over any investment period. Our derivations can be readily extended to markets having more than two stocks, where these extensions are provided in the paper. As predicted from our derivations, we significantly improve the achieved wealth with respect to the portfolio selection algorithms from the literature on historical data sets under both mild and heavy transaction costs.
Open Access
Organization and functioning of liberalized electricity markets: An overview of the Dutch market
(Elsevier Ltd, 2015) Tanrisever, F.; Derinkuyu, K.; Jongen, G.
Abstract In this paper, we examine the organization and the functioning of the Dutch electricity market. First we describe the organization of the Dutch electricity supply chain and the role of the main market participants including the transmission system operator, distribution system operators, program responsible parties and metering companies. We then describe the organization of financial trading and clearing mechanism of electricity through the organized futures exchange (The European Energy Derivatives Exchange), and the spot market (Amsterdam Power Exchange) which includes the day-ahead market and intra-day markets. We also detail the functioning of the imbalance market and reserve capacity management in the Netherlands. Through a set of numerical analysis, we provide an exploratory analysis of the APX day-ahead spot prices and the real-time imbalance prices using electricity price data from 2002 to 2013. We observe the price spikes both in the day-ahead and imbalance markets usually occur around 6-10 AM and 5-7 PM. We also observe that in the imbalance market system overages happen significantly more often than shortages pointing out that the market tends to buy more than what is demanded. This could be explained by the risk attitude of the market participants in the imbalance market.
Open Access
Robust scheduling and robustness measures for the discrete time/cost trade-off problem
(Elsevier, 2010) Hazır, O.; Haouari, M.; Erel, E.
Projects are often subject to various sources of uncertainties that have a negative impact on activity durations and costs. Therefore, it is crucial to develop effective approaches to generate robust project schedules that are less vulnerable to disruptions caused by uncontrollable factors. In this paper, we investigate the robust discrete time/cost trade-off problem, which is a multi-mode project scheduling problem with important practical relevance. We introduce surrogate measures that aim at providing an accurate estimate of the schedule robustness. The pertinence of each proposed measure is assessed through computational experiments. Using the insights revealed by the computational study, we propose a two-stage robust scheduling algorithm. Finally, we provide evidence that the proposed approach can be extended to solve a complex robust problem with tardiness penalties and earliness revenues. © 2010 Elsevier B.V. All rights reserved.
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Şefik Yılmaz Dizdar biyografisi
(Bilkent University, 2020) Bıçkıcılar, Alper; Ercanoğlu, Berke; Uzuner, Elif; Öztürk, Mısra Kübra; Ceylan, Sena
Şefik Yılmaz Dizdar 1939 yılında Safranbolu’nun Akçasu Mahallesinde doğdu. Çocukluğunu ve ilköğretim hayatını Safranbolu’da geçirdikten sonra İzmir İktisadi ve Ticari İlimler Akademisini bitirdi. İki sene süren askerliğini de tamamlayıp iş hayatına Karabük Demir Çelik Fabrikasında başladı. 1961-1979 yılları arasında Karabük Demir Çelik İşletmelerinde farkı pozisyonlarda çalıştı. İstifasından sonra demir çelik ticareti yapmak için İstanbul'a taşındı ve o dönemde süregelen İran-Irak Savaşı sonucunda demir çelik piyasasında oluşan fırsatları değerlendirdi. Bu sektörde elde ettiği sermaye sayesinde ortağı Mustafa Küçükle tekstil alanına girerek Türkiye ekonomisine katkıda bulunmuştur. Memleketi olan Safranbolu’ya kültürel, ticari ve turizm alanlarında katkıda bulunan Şefik Yılmaz Dizdar, bugün hayatına Safranbolu’da devam etmektedir
Open Access
Soccer and stock market risk: empirical evidence from the Istanbul stock exchange
(Sage Publications, Inc., 2013) Berument, Hakan; Ceylan, N. B.
There is an emerging but important literature on the effects of sport events such as soccer on stock market returns. After a soccer team's win, agents discount future events more favorably and increase risk tolerance. Similarly, after a loss, risk tolerance decreases. This paper directly assesses risk tolerance after a sports event by using daily data from the three major soccer teams in Turkey (Beşiktaş, Fenerbahçe and Galatasaray). Results provide evidence that risk tolerance increases after a win, but similar patterns were not found after a loss. © Psychological Reports 2013.
Open Access
Strategic alignment and new product development: drivers and performance effects
(Wiley-Blackwell Publishing, 2012) Acur, N.; Kandemir, D.; Boer H.
Strategic alignment is widely accepted as a prerequisite for a firm's success, but insight into the role of alignment in, and its impact on, the new product development (NPD) process and its performance is less well developed. Most publications on this topic either focus on one form of alignment or on one or a limited set of NPD performance indicators. Furthermore, different and occasionally contradictory findings have been reported. NPD scholars have long argued for the importance of fit between context and NPD activities. However, this body of literature suffers from the same weakness: most publications have a limited scope and the findings are not always consistent with results reported previously. This study addresses these deficiencies by examining (1) the effects of various internal and external factors on different forms of alignment, and (2) the effects of these forms of alignment on a set of NPD performance indicators. Strategic planning and innovativeness appear to affect technological, market, and NPD-marketing alignment positively. Environmental munificence is negatively associated with NPD-marketing alignment, but has no effect on the two other forms of alignment. Technological change has a positive effect on technological alignment, a negative effect on NPD-marketing alignment, but no effect on market alignment. These findings suggest that internal capabilities are more likely to be associated with the development of strategic alignment than environmental factors are. Furthermore, technological and NPD-marketing alignment affect NPD performance positively, while market alignment does not have any significant performance effects.