Ticari Bilimler Fakültesi / Faculty of Commercial Science
Permanent URI for this collectionhttps://hdl.handle.net/11727/2074
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Item Reduced-Order Modeling For Heston Stochastic Volatility Model(HACETTEPE JOURNAL OF MATHEMATICS AND STATISTICS, 2024) Kozpinar, Sinem; Uzunca, Murat; Karasozen, BulentIn this paper, we compare the intrusive proper orthogonal decomposition (POD) with Galerkin projection and the data-driven dynamic mode decomposition (DMD), for Heston's option pricing model. The full order model is obtained by discontinuous Galerkin discretization in space and backward Euler in time. Numerical results for butterfly spread, European and digital call options reveal that in general DMD requires more modes than the POD modes for the same level of accuracy. However, the speed-up factors are much higher for DMD than POD due to the non-intrusive nature of the DMD.Item Factors Determining Consumer Concerns About Clothing Industry Problems(2023) Erol boyaci, Gulay; Senturk ozer, Leyla; HOC-6390-2023Although the public concern towards unsustainable current production and consumption is growing, the inadequacy of global regulations on sustainability issues puts the responsibility on consumers. However, despite their concerns, some consumers need help shopping from sustainable brands. The current research examines some antecedents of consumer concern towards the clothing industry's environmental and sweatshop issues. Data is obtained from 372 Turkish fast fashion consumers through online platforms. Level of exposure to informative posts on social media platforms, the perceived knowledge and belief towards the issues positively affect concern. Also, decreasing concern towards these problems with advancing age is observed in Turkiye.Item The Intellectual Structure of the Information Systems Field: Research Styles and Publication Patterns of North American and European Paradigms(2022) Ozkoc, Esma Erguner; Kefkir, Teoman Ahmet; Kirkbesoglu, Erdem; https://orcid.org/0000-0002-6781-9753; AAG-1506-2021; ABI-3973-2020This paper identifies the researches that have had the greatest impact on the Information Systems (IS) discipline and analyses the changes that have taken place in the intellectual structure of this discipline within the ongoing paradigmatic debates between Europe and North America. The methodology applies citation analysis and social network analysis to the articles published in four European and North American journals with the highest impact factors in the IS field. The findings of the study reveal a significant difference between the research styles and publication patterns of European and North American research traditions.Item Angiotensin receptor neprilysin inhibitor for patients with heart failure and reduced ejection fraction: Real-world experience from Turkey (ARNi-TR)(2021) Ekici, Berkay; Yaman, Mehmet; Kucuk, Murathan; Dereli, Seckin; Yenercag, Mustafa; Yigit, Zerrin; Bas, Mehmet Memduh; Karavelioglu, Yusuf; Cakmak, Huseyin Altug; Kivrak, Tarik; Ozkan, Hakan; Altin, Cihan; Sabanoglu, Cengiz; Demirkan, Burcu; Atas, Ali Ekber; Kilicaslan, Fethi; Altay, Hakan; Tengiz, Istemihan; Erkan, Aycan Fahri; Kilicaslan, Baris; Olgun, Fatih Erkam; Durakoglugil, Murtaza Emre; Alhan, Aslihan; Zoghi, Mehdi; 34308869Objective: Heart failure (HF) is a growing public health problem with high morbidity and mortality. Recently, angiotensin receptor neprilysin inhibitor (ARNi) has emerged as a promising treatment for HF with reduced ejection fraction (HFrEF). Here, we shared our experience with the use of ARNi in HFrEF from multiple centers in Turkey. Methods: The ARNi-TR is a multicenter, nonintervention al, retrospective, observational study. Overall, 779 patients with HF from 22 centers in Turkey who were prescribed sacubitril/valsartan were examined. Initial clinical status, biochemical and echocardiographic parameters, and New York Heart Association functional class (NYHA-FC) values were compared with follow-up values after 1 year of ARNi use. In addition, the effect of ARNi on number of annual hospitalizations was investigated, and the patients were divided into 2 groups, depending on whether ARNi was initiated at hospitalization or under outpatient clinic control. Results: N-terminal pro-brain natriuretic peptide (NT-proBNP), left-ventricle ejection fraction (LV-EF), and NYHA-FC values improved significantly in both groups (all parameters, p<0.001) within 1-year follow-up. In both groups, a decrease in hemoglobin A1c (HbA1c) values was observed in ARNi use (p<0.001), and a decrease in daily diuretic doses and hospitalizations owing to HF were observed after ARNi use (all comparisons, p<0.001). Hypotension (16.9%) was the most common side effect in patients using ARNi. Conclusion: The ARNi-TR study offers comprehensive real-life data for patients using ARNi in Turkey. The use of ARNi has shown significant improvements in FC, NT-proBNP, HbA1c levels, and LV-EF. Likewise, reductions in the number of annual hospitalizations and daily furosemide doses for HF were seen in this study.Item Temel istatistik yöntemleri(2018) Cula, Serpil; Muluk, ZehraItem Young tableaux and Arf partitions(2019) Tutas, Nesrin; Karakas, Halil İbrahim; Gumusbas, NihalThe aim of this work is to exhibit some relations between partitions of natural numbers and Arf semigroups. We also give characterizations of Arf semigroups via the hook-sets of Young tableaux of partitions.Item Staff Task-Based Shift Scheduling Solution with an ANP and Goal Programming Method in a Natural Gas Combined Cycle Power Plant(2019) Ozder, Emir Huseyin; Ozcan, Evrencan; Eren, Tamer; 0000-0002-1895-8060; Q-4772-2017Shift scheduling problems (SSPs) are advanced NP-hard problems which are generally evaluated with integer programming. This study presents an applicable shift schedule of workers in a large-scale natural gas combined cycle power plant (NGCCPP), which realize 35.17% of the total electricity generation in Turkey alone, as at of the end of 2018. This study included 80 workers who worked three shifts in the selected NGCCPP for 30 days. The proposed scheduling model was solved according to the skills of the workers, and there were nine criteria by which the workers were evaluated for their abilities. Analytic network process (ANP) is a method used for obtaining the weights of workers' abilities in a particular skill. These weights are used in the proposed scheduling model as concepts in goal programming (GP). The SSP-ANP-GP model sees employees' everyday preferences as their main feature, bringing high-performance to the highest level, and bringing an objective functionality, and lowering the lowest success of daily choice. At the same time, the model introduced large-scale and soft constraints that reflect the nature of the shift requirements of this program by specifying the most appropriate program. The required data were obtained from the selected NGCCPP and the model solutions were approved by the plant experts. The SSP-ANP-GP model was resolved at a reasonable time. Monthly acquisition time was significantly reduced, and the satisfaction of the employees was significantly increased by using the obtained program. When past studies were examined, it was determined that a shift scheduling problem of this size in the energy sector had not previously been studied.Item Employee deviant behavior: role of culture and organizational relevant support(2019) Kalemci, R. Arzu; Kalemci-Tuzun, Ipek; Ozkan-Canbolat, Ela; 0000-0001-6979-2040; ABB-5350-2020Purpose The purpose of this paper is to increase the knowledge and understanding of organizational and supervisory support in the context of employee deviant workplace behavior (DWB) by examining the potential associations of employees' cultural value orientations. This paper aims to: clarify DWB; review perceived organizational support (POS) and perceived supervisory support (PSS); discuss the meaning of employees' cultural value orientations (individualism-collectivism, power distance and paternalism); use the fuzzy logic model to analyze relationships between DWB and POS, as well as PSS and employees' cultural value orientations. Design/methodology/approach This research applies a fuzzy-set qualitative comparative analysis. Findings The results show the role of employee perceived organizational and supervisory support and cultural dimension (power distance and paternalism) configurations on employee DWB. Originality/value The main originality of this study is to further increase the understanding of organizational and supervisory support in the context of employee DWB by examining the potential associations of employees' cultural value orientations. This study extends the previous research by providing evidence that organizational and supervisory support influences employees' DWB.Item Sustainable Personnel Scheduling Problem Optimization in a Natural Gas Combined-Cycle Power Plant(2019) Ozder, Emir Huseyin; Ozcan, Evrencan; Eren, Tamer; 0000-0002-1895-8060; Q-4772-2017This paper deals with a sustainable personnel scheduling problem of personnel working in a large-scale natural gas combined-cycle power plant in Turkey. The proposed model focuses on employee complaints due to unfair work schedules and the results of balanced assignments based on power plant interruptions. Eighty personnel work in three shifts at this natural gas combined-cycle power plant. The model is solved with respect to some of the workers' skills, and there are 20 criteria regarding skills. The analytic network process method is used to get the weights of workers' skills, which are calculated and included in the model. Goal programming is used in this paper. Our proposed model gives cost minimization and fair work schedules for the power plant. Compared with the literature, the number and set of criteria are unique in terms of personnel competency in the energy sector. Minimizing cost and imbalanced assignments was achieved by the proposed model for the first time without considering the sector.Item Platform-switched implants vs platform-matched implants placed in different implant-abutment interface positions: A prospective randomized clinical and microbiological study(2019) Uraz, Ahu; Isler, Sila C.; Cula, Serpil; Tunc, Samet; Yalim, Mehmet; Cetiner, Deniz; 31808297Background Placement of the implant-abutment interface (IAI) away from the bone crest has been suggested to have positive impacts on maintenance of peri-implant tissues. Purpose To assess the effects of platform-switched and platform-matched implants, taking into consideration the IAI at different positions relative to the bone crest, on clinical, radiographic, and microbiological outcomes during 12 months following functional loading. Materials and Methods The present prospective randomized study was performed upon 70 patients. Group I (n = 23) implants presenting a platform-switched implant-abutment connection design was inserted 1 mm subcrestally. Group II (n = 22) implants with similar properties were inserted crestally. Group III (n = 25) implants presenting a platform-matched approach with an internal hexagon connection design was inserted crestally. The periodontal parameters were assessed at baseline, and 3, 6, and 12 months postloading. Radiographic marginal bone level (MBL) changes were analyzed at the 12-month follow-up. The amount of DNA copies of Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Tannerella forsythia, Provetalla intermedia and total bacterial mean load in peri-implant sulcus fluid (PISF) were assessed at the same periods. Results There were no significant differences among the groups with respect to the periodontal parameters for all time periods. At 12-month follow-up, the MBL changes were 0.16 +/- 0.29 mm and 0.17 +/- 0.23 mm for group I, 0.15 +/- 0.25 mm and 0.17 +/- 0.26 mm for group II, 0.17 +/- 0.26 mm and for group III in mesial and distal sites, respectively. The mean total bacterial load was found significantly higher for group III compared to the other groups in the three interval times (P < .05). Conclusion Implants restored with platform-switching and platform-matching performed equally regarding clinical and radiographic outcomes. Platform-matched implants inserted at the crestal level presented higher the mean bacterial total load in PISF.