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Öğe A coordinated scheduling problem for the supply chain in a flexible job shop machine environment(Springer Heidelberg, 2021) Ceylan, Zeynep; Tozan, Hakan; Bulkan, SerolIn this study, a new coordinated scheduling problem is proposed for the multi-stage supply chain network. A multi-product and multi-period supply chain structure has been developed, including a factory, warehouses, and customers. Furthermore, the flexible job shop scheduling problem is integrated into the manufacturing part of the supply chain network to make the structure more comprehensive. In the proposed problem, each product includes a sequence of operations and is processed on a set of multi-functional machines at the factory to produce the final product. Final products are delivered to the warehouses to meet customers' demands. If the demands of customers are not fulfilled, the shortage in the form of backorder may occur at any period. The problem is expressed as a bi-objective mixed-integer linear programming (MILP) model. The first objective function is to minimize the total supply chain costs. On the other hand, the second objective function aims to minimize the makespan in all periods. A numerical example is presented to evaluate the performance of the proposed MILP model. Five multi-objective decision-making (MODM) methods, namely weighted sum, goal programming, goal attainment, LP metric, and max-min, are used to provide different alternative solutions to the decision-makers. The performance of the methods is evaluated according to both objective function values and CPU time criteria. In order to select the best solution technique, the displaced ideal solution method is applied. The results reveal that the weighted sum method is the best among all MODM methods.Öğe A multi-criteria assessment of the p-median, maximal coverage and p-center location models(Strojarski Facultet, 2017) Karataş, Mümtaz; Razi, Nasuh; Tozan, HakanLocation problems consider locating facilities with the objective of finding their best locations. In most real world problems, it is common that a demand node is required to be covered with multiple facilities in order to ensure a backup supply. The backup supply is necessary especially for public or emergency service location problems where a covered demand may not be serviced if it's designated facility is engaged serving other demands. In this study we consider three classic location models, i.e. p-median, maximal coverage and p-center, and compare their performances with respect to seven decision criteria under Q-coverage requirement. For this purpose, we generate multiple problem instances and solve each instance with the three models for different Q-values. Our numerical results reveal the pros and cons of each model to assist decision makers in determining the most promising model with respect to each assessment criteria.Öğe A multi-criteria decision-making approach for greenovative supplier selection(University of Cincinnati, 2022) Çaloğlu Büyükselçuk, Elif; Tozan, Hakan; Vayvay, ÖzalpIn today's rapidly changing business environment, green and innovative (greenovative) activities have become indispensable elements of sustainable supply network management. Realization of this fact obliges firms to consider greenovative as well as traditional criteria in determining their supplier. This study provides a new greenovative systematic approach to supplier selection for small and medium-sized enterprises. Fuzzy multi-criteria decision-making (FMCDM)-based techniques were used to determine the most appropriate supplier with the proposed model. To show the usability of the model, an application was carried out on an automotive supply company. Analytic Hierarchy Process (AHP) and Fuzzy Analytic Hierarchy Process (FAHP) approaches were used to calculate the weights of the supplier selection criteria. After determining criteria weights, different multi-criteria decision-making (MCDM) techniques that are often encountered in the literature were used to identify the best supplier.Öğe A new decision model approach for health technology assessment and a case study for dialysis alternatives in Turkey(MDPI, 2020) Öztürk, Necla; Tozan, Hakan; Vayvay, ÖzalpBackground: This paper presents a generic Multi-Criteria Decision Analysis (MCDA) model for Health Technology Assessment (HTA) decision-making, which can be applied to a wide range of HTA studies, regardless of the healthcare technology type under consideration. Methods: The HTA Core Model((R)) of EUnetHTA was chosen as a basis for the development of the MCDA model because of its common acceptance among European Union countries. Validation of MCDA4HTA was carried out by an application with the HTA study group of the Turkish Ministry of Health. The commitment of the decision-making group is completed via an online application of 10 different questionnaires. The Analytic Hierarchy Process (AHP) is used to determine the weights. Scores of the criteria in MCDA4HTA are gathered directly from the HTA report. The performance matrix in this application is run with fuzzy Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), fuzzy Vise Kriterijumska Optimizacija I Kompromisno Resenje (VIKOR), and goal programming MCDA techniques. Results: Results for fuzzy VIKOR, fuzzy TOPSIS, and goal programming are 0.018, 0.309, and 0.191 for peritoneal dialysis and 0.978, 0.677, and 0.327 for hemodialysis, respectively. Conclusions: Peritoneal dialysis is found to be the best choice under the given circumstances, despite its higher costs to society. As an integrated decision-making model for HTA, MCDA4HTA supports both evidence-based decision policy and the transparent commitment of multi-disciplinary stakeholders.Öğe A novel fuzzy framework for technology selection of sustainable wastewater treatment plants based on TODIM methodology in developing urban areas(Nature Research, 2022) Eseoğlu, Güneş; Yapsaklı, Kozet; Tozan, Hakan; Vayvay, ÖzalpOptimal technology selection of wastewater treatment plants (WWTPs) necessitates the adoption of data-driven scientific approaches that satisfy the sustainability requirements of the urban ecosystem. Such approaches should be able to provide actionable insights to decision makers constrained by factors such as population growth, land scarcity, and loss of functionality of wastewater treatment plants. The framework in this study proposes a hybrid fuzzy multi-criteria decision making (MCDM) model consisting of the analytical hierarchy process (AHP) and the TODIM (an acronym in Portuguese of interactive and multi-criteria decision-making) by using alpha cut series which takes into account the risk aversion of decision makers (DMs) to overcome uncertainties of environmental conditions. The literature to date indicates that the study is the first to presents how a systematic decision-making process is approached by interpreting the interaction of criteria for the selection of wastewater treatment technology through the membership function of Prospect Theory. The proposed methodology reveals that the prominent reference criterion manipulates other sub-criteria according to the function of risk-aversion behavior. The fuzzy sets based on alpha cut series are employed to evaluate both the criteria weight and the rank of the alternatives in the decision-making process to obtain compromise solutions under uncertainty. The dominance degrees of the alternatives are achieved by fuzzy TODIM integrated with the fuzzy analytic hierarchy process (FAHP) which deals with the uncertainty of human judgements. According to the ranking results determined by the dominance degree of alternatives, anaerobic-anoxic-oxic (A2O) without pre-clarification was the most effective process in relation to the sludge disposal cost (C25) calculated as reference criteria. The ranking of four full-scale WWTPs in a metropolitan city of an EMEA country based on 24 sub-criteria listed under the four main criteria, namely the dimensions of sustainability, is used as a case study to verify the usefulness of the fuzzy approach. Motivated by the literature gap related to the failure to consider the psychological behavior of DMs in technology selection problem for wastewater treatment, it is discussed how the proposed hybrid MCDM model can be utilized by reflecting human risk perception in wastewater treatment technology selection for developing urban areas.Öğe A polyurethane/carbon black composite absorber for low frequency waves(Springer-Verlag Berlin, 2019) Yağımlı, Mustafa; Tozan, Hakan; Esen, H. Ergin; Arca, EminThis study proposes a Polyurethane/Carbon Black composite coating that has the ability of absorbing low frequency waves. The characteristics of coating including contact angle measurements are provided and for performance analyses, a 1 kHz amplitude-modulated signal superimposed on red and green laser beam (whose intensity is changed by square wave) sent to composite coated surface. The reflected beam from the coating was detected by BPW20RF photodetector and signal waves were measured. The results of the analyses illustrated that the composite; coating to a great extent, absorbed the waves.Öğe A review on machine learning applications: CVI risk assessment(2024) Birlik, Ayşe Banu; Tozan, Hakan; Köse, Kevser BanuComprehensive literature has been published on the development of digital health applications using machine learning methods in cardiovascular surgery. Many machine learning methods have been applied in clinical decision-making processes, particularly for risk estimation models. This review of the literature shares an update on machine learning applications for cardiovascular intervention (CVI) risk assessment. This study selected peer-reviewed scientific publications providing sufficient detail about machine learning methods and outcomes predicting short-term CVI risk in cardiac surgery. Thirteen articles fulfilling pre-set criteria were reviewed and tables were created presenting the relevant characteristics of the studies. The review demonstrates the usefulness of machine learning methods in high-risk CVI applications, identifies the need for improvement, and provides efficient support for future prediction models for the healthcare system.Öğe A surface free energy-based characterization of PEG-PLA coating(İstanbul Medipol Üniversitesi Fen Bilimleri Enstitüsü, 2021) Yılmaz, Beyza Özlem; Tozan, HakanThe field of health has a dynamic structure in terms of its basic structure and therefore needs constant change and development. In addition, limited resources in the field of health and increasing health expenditures around the world have increased the need for new approaches in this field. Polymers have played a vital role in the development of new approaches, especially with their increasing market shares. Initially, the use of polymers was limited mainly as implants and medical devices to ensure the smooth functioning of injured or ruptured tissues or organs, and to protect and improve human living conditions. Advances in polymer engineering, such as new coating technologies, have allowed polymers to be used in a wider range of applications. As the application areas of polymers have expanded, their usage patterns have also changed. Polymer-based approaches are also offered to develop targeted therapeutic or diagnostic procedures, through polymer coating of other materials for use in the body. At this point, PEG-PLA are FDA-approved polymers that are often used in polymer coatings. Coating a material with a PEG-PLA mixture in a suitable combination provides different contributions such as wear rate, hydrophilicity, mechanical resistance, and is accepted as one of the promising approaches that minimizes each other's deficiencies. However, one of the most important factors in coating applications is the surface free energy. At this point, the main purpose of this study is to investigate the surface free energies in computer environment by means of static contact measurements of surfaces coated with PEG-PLA mixtures at different rates. As a result of the study, it was observed that the surface free energy decreased as the static contact angle increased. Neumann, Wu, Acid-Base, Fowkes and OWRK methods were used to calculate the surface free energies. SFE measurements in the Neumann method were taken into account, and it was concluded that among the PEG-PLA mixtures in different combinations, the mixture number 5 was the most suitable combination for coating the relevant surface due to its high surface free energy. It is expected that this study will pave the way for the determination of the appropriate combinations for the coating to be made at the point of improving the properties of a material to be used in the field of health, and the effective use of limited resources. Thus, it is expected that the analysis of the coatings made will shed light on future studies on realizing coatings suitable for the surface and providing the desired properties in a cost-effective framework.Öğe Acoustic chamber length performance analysis in ultrasonic pulsating water jet erosion of ductile material(Elsevier, 2019) Nag, Akash; Hloch, Sergej; Ğuha, Dominik; Dixit, Amit Rai; Tozan, Hakan; Petru, Jana; Hromasova, Monika; Müller, MiroslavUltrasonic pulsating water jets are a technological modification of water jet technologies that disintegrate materials at pressures <= 100 MPa. Disintegration occurs at a non-systematically determined standoff distance z [mm] as a result of variable axial jet speeds determined by the acoustic chamber length. Water velocity fluctuations are converted from pressure fluctuations present in the acoustic chamber using a nozzle. Pressure fluctuations are generated by an ultrasonic sonotrode with a frequency of 20 kHz. The impulse travels through the acoustic chamber, which is geometrically designed to vary its length from 0 mm to 25 mm with a mechanical nut. A PWJ system can be tuned within this interval to achieve the desired PWJ performance. Until now, the synergic effects of the standoff distance z [mm] and the acoustic chamber length l(c) [mm] on material interactions have not been clarified in the literature. Therefore, this study discusses how the length of the acoustic chamber lc is related to the nozzle's standoff distance z [mm] from the surface of the material and from the point of achieved maximal depth h [mm]. The length of the chamber was gradually increased by one millimetre from 5 to 22 mm. Subsequently, PWJs with p = 30 MPa and 40 MPa were tested. The robot arm carrying the nozzle head travelled along a programmed trajectory at an angle of 16 degrees starting from z = 5 mm with a traverse speed v = 5 mm/s. It has been found that the effect of acoustic chamber length on the disintegration within an erosion interval has a hyperbolic course.Öğe An integrated framework for non-traditional machining process technology selection in healthcare applications(Strojarski Facultet, 2022) Delice, Elif; Tozan, Hakan; Karadayı, Melis Almula; Harnicarova, Marta; Turan, BaşakIn spite of continuous progress in technical advancement, the conventional machining process became unsatisfactory in the healthcare field due to its disadvantages. This inadequacy lead researchers to consider using the application of nontraditional machining that can machine extremely hard and brittle materials into complicated shapes such as medical devices and implants in healthcare. In this study, the three most popular nontraditional machining process technologies: Laser Beam Machining, Water Jet Machining, and Electrocautery are evaluated to determine the most appropriate technology using the Health Technology Assessment based Multi-criteria Decision-Making framework. HTA is organized evaluation of effects and properties of health technology that enables the application of systematic skills to solve a health problem. HTA's main goal is to raise awareness of new health technologies among decision makers. For these reasons, the HTA core model that enables the production of HTA-related information was utilized.The comparison of selected technologies was carried out via integrating the HTA core model, Best Worst, and Evaluation Based on Distance from Average Solution methods. Finally, a comparison was made to find the most suitable technology to create the necessary infrastructure. As a result, evaluation scores were computed as 0,673; 0,538 and 0,500 for WJM, LBM, and EC, respectively.Öğe An integrated multi-criteria decision making methodology for health technology assessment(Inderscience Enterprises Ltd., 2018) Karataş, Mümtaz; Karacan, İlknur; Tozan, HakanThis study presents a synthesis on the application of multi-criteria decision making (MCDM) methodologies as an innovative tool to provide a more robust and reliable selection or ranking processes for health technology assessment (HTA). HTA is described as the 'systematic' evaluation of health related technologies with respect to multiple criteria. Thus, to carry out effective HTA processes, decision-makers should consider utilising integrated or hybrid decision making processes. In this study, we develop a decision support tool called 'DEMATSEL' which serves as an integrated MCDM methodology in fuzzy environments. Our integrated approach combines four widely-used MCDM methods, viz. fuzzy AHP, fuzzy TOPSIS, fuzzy VIKOR and goal programming. We demonstrate the effectiveness of our proposed novel approach on a fuzzy HTA case study of bariatric surgery selection in Turkey.Öğe An integrated performance measurement framework for restaurant chains: A case study in Istanbul(TMMOB Chamber of Mechanical Engineers, 2022) Pınarbaşı, Ayşegül; Aydın, Umut; Karadayı, Melis Almula; Tozan, HakanCompanies that continue to operate in a competitive market strive the most efficient use of their resources in order to remain competitive. Nowadays, with increasing customer feedback, properly analyzing customer needs and requests and producing services in accordance with expectations have become increasingly important due to the large number of companies competing in the same market, and this is especially important to be at the forefront of competitors in the food services industry. There are risks and uncertainties owing to the continuously changing demand for food service enterprises, the difficulty to regulate interest and comparable charges, the competitive environment, and currency rate hikes. In light of all of these circumstances, restaurants require a versatile tool to effectively measure and analyze their performance. Therefore, this study combines Principal Component Analysis (PCA) and Categorical Data Envelopment Analysis (CAT-DEA) to analyze the performance of 15 dealers in Istanbul, divided into three categories: steakhouse, kebab, and meatball-doner. The results demonstrate that each category has just one efficient restaurant, for a total of three efficient restaurants out of fifteen. In addition to the suggested CAT-DEA-based framework, three research hypotheses are constructed and analyzed to investigate the link between restaurant performance and various environmental factors (or relevant indicators) in the food service industry.Öğe An MCDM-based health technology assessment (HTA) study for evaluating kidney stone treatment alternatives(Springer Science and Business Media Deutschland GmbH, 2021) Erol, Eren; Yılmaz, Beyza Özlem; Almula Karadayı, Melis; Tozan, HakanThe prevalence of kidney stone disease has increased during the last decade due to various reasons such as changes in dietary and water consumption. To overcome this issue, new treatment approaches are being developed. Today, Extracorporeal Shock Wave Lithotripsy (ESWL) and Laser Lithotripsy (LL) are the most popular approaches for the fragmentation of kidney stones. However, the advantages and limitations of these treatment methods are still being questioned by healthcare professionals. A systematic and efficient approach is thus required to help healthcare providers for selecting the best treatment approach. Multi-Criteria Decision-Making (MCDM) techniques are a reliable and powerful approach to respond to the need for such comparative analysis. Hence, the aim of this study is to propose an HTA-based hierarchical evaluation structure for kidney stone treatment methods utilizing the Hierarchical Fuzzy TOPSIS method and conduct a case study on LL and ESWL. The structure consists of 5 main criteria and 24 sub-criteria. The study group for linguistic evaluations consists of medical doctors (nephrologists and urologists) and researchers. Closeness coefficient values are obtained as 0.577 and 0.372 for LL and ESWL, respectively. It is concluded that LL should be selected as the ideal alternative under the proposed hierarchical evaluation structure. The study is expected to bring insights to further studies as well as healthcare providers who are working in the field.Öğe Application of a novel hybrid f-sc risk analysis method in the paint industry(MDPI, 2021) Hacıbektaşoğlu, Süleyman Enes; Mertoğlu, Bülent; Tozan, HakanOccupational health and safety (OHS) activities aim to ensure the full mental and physical well-being of employees in the workplace. For this reason, it is essential to determine the precautions to be taken and the suitability of risk assessments. In this study, f-SC, a novel hybrid risk analysis method using Step-Wise Weight Assessment Ratio Analysis (SWARA) and Complex Proportional Assessment (COPRAS) multi-criteria decision making methods (MCDM) based on fuzzy logic, was developed to perform a classical Fine–Kinney risk analysis method. There are few studies in the literature about the Fine–Kinney method compared to other risk analysis methods such as FMEA and FTA. Therefore, this work aimed to integrate this classical method with the proposed method to obtain more accurate and sensitive results in risk analyses. First, the criteria used in determining the risk score were weighted with the help of 10 OHS experts. As the criteria used in the classical method are evaluated with equal importance, this situation can cause serious errors in the risk scores obtained with the relevant calculations and in the risk priorities based on these calculations. We aimed to minimize the occurrence of such errors by determining the weights of the criteria with the proposed method. f-SWARA was used for this process. The weights of probability, exposure, and severity criteria were obtained as 0.196, 0.285, and 0.518, respectively. Thus, it was determined that severity is an important and effective criterion for calculating the risk score. In the proposed method, after the criterion weights were determined, an analysis of the hazards was conducted with the f-COPRAS method instead of the classical Fine–Kinney method. Contrary to the numerical values used in the classical method, in this method, decision makers use linguistic terms that are more intuitive than numerical values. These linguistic terms were converted into numerical values using this method based on fuzzy logic, and a ranking of hazards was obtained. As a result of the analyses, it was seen that the case study, H7, which had a 0.557 Ni value, was the most dangerous scenario and that H11, which had a 1.000 Ni value, was the least dangerous. In addition, for the same data, analyses were conducted using the fuzzy Vise Kriterijumska Optimizacija I Kompromisno Resenje (VIKOR) method, which has been previously used in the literature, and a comparison was made with the f-SC method to demonstrate the validity of the study. The results of the f-VIKOR and classical Fine–Kinney methods were similar to the developed f-SC method. This research provides three contributions: (1) criteria must be weighted to determine risk scores, (2) using intuitive linguistic terms in scoring criteria made the risk analysis method more sensitive and appropriate, and (3) using MCDM methods instead of classical methods for the risk analyses in the OHS field removes uncertainties.Öğe Application of cardio-forecasting for evaluation of human-operator performance(MDPI AG, 2020) Panda, Anton; Nahornyi, Volodymyr; Valicek, Jan; Harnicarova, Marta; Pandova, Iveta; Borzan, Cristina; Cehelsky, Samuel; Androvic, Lukas; Tozan, Hakan; Kusnerova, MilenaThe paper presents the results of the development of the cardio-forecasting technology, which introduces a new method to monitor the state of human-operator, which is characteristic for the given production conditions and for individual operators, to predict the moment of exhaustion of his/her working capacity. The work aims to demonstrate the unique, distinctive features of the cardio-forecasting technology for predicting an individual limit of his/her working capacity for each person. A unique methodology for predicting individually for each person the moment when he/she reaches the limit of his/her working capacity is based on a spectral analysis of a human phonocardiogram in order to isolate the frequency component located at the heart contraction frequency. The trend of the amplitude of this component is approximated by its model; consequently, the coefficients of the trend model are determined. They include the operator’s operating time until his/her working capacity is exhausted. A methodology for predicting the moment when he/she reaches the limit of his/her working capacity for each person individually and assessment based on this degree of criticality of their condition will be realized as a software application for smartphones using the Android operating system.Öğe Applications of data mining algorithms for customer recommendations in retail marketing(Nova Science Publishers, Inc., 2022) Delice, Elif; Polatlı, Lütviye Özge; Düzdar Argun, İrem; Tozan, HakanIn recent years, researchers have highlighted how large volumes of data can be transformed into information to determine customer behaviors, and data mining applications have become a major trend. It has become critical for organizations to use a tool for understanding the relationships between data to protect their marketplace by increasing customer loyalty. Thanks to data mining applications, data can be processed and transformed into information, and in this way, target audiences can be determined while developing marketing strategies. This chapter aims to increase the market share with products specific to the customer portfolio, introduce strategic marketing tools for retaining old customers, introduce effective methods for acquiring new customers, and increase the retail sales chart, based on purchasing habits of customers. The data set was collected under pandemic conditions during the COVID-19 process and analyzed to support retail businesses in their online shopping orientation. By examining the local customer base, it was assumed that the customer group would display similar behaviors in online or teleordering methods, customer identification and order estimation were made to follow an effective sales policy. Segmentation was performed with data mining applications, and the grouped data were separated according to their similarities. The data set consisting of demographic characteristics and various product information of the enterprise's customers were analyzed with Decision Tree and Random Forest, which are data mining methods, the best performing algorithm in the data set was selected by comparing the performance of the methods. As a result of the findings, appropriate suggestions were given to the business to determine the purchasing tendencies of the customers and to increase the level of effectiveness in sales-marketing strategies. In this way, materials were presented to assist the enterprise in developing strategies to increase the number of sales by taking faster and more accurate action by avoiding the time and expense that would be lost by the trial-error method.Öğe Bir akılcı antibiyotik uygulaması ve uygulama sonrası kullanım tahmini(İstanbul Medipol Üniversitesi, Fen Bilimleri Enstitüsü, 2022) Dikkaya, Seher; Tozan, Hakan; Karadayı, Melis AlmulaAntibiyotiklerin kontrolsüz kullanımı insanların sağlıklı yaşamı ve yaşam kalitesi üzerinde birtakım sorunlara yol açmaktadır. İstenmeyen sonuçların yok edilmesi amacıyla profilaktik antibiyotik kullanımları için sağlık kuruluşlarının birtakım politikalar geliştirmesi ve aksiyon almaları gerekmektedir. Profilaktik antibiyotiklerin akılcı kullanımlarının sağlanması adına OECD, Dünya Sağlık Örgütü ve Türkiye İlaç ve Tıbbi Cihaz Kurumu gibi ulusal ve uluslararası sağlık otoriteleri tarafından kullanım oranlarını konu edinen pek çok rapor yayınlanmıştır. Gerçekleştirilen bazı çalışmalarda profilaktik antibiyotik kullanım miktarları ele alınırken, bazılarında tahmini direnç oranlarını ya da akılcı ilaç kullanımında beş yıllık stratejik planlama üzerinde detaylı değerlendirme yapılmıştır. Tüm çalışmaların ortak amacı profilaktik antibiyotiklerin akılcı kullanımı ile hasta güvenliğinin ve maliyet verimliliğinin sağlanabilmesidir. Antibiyotiklerin akılcı kullanımı uygun antibiyotiğin, uygun zamanda, uygun miktarda, uygun uygulama yolu ve uygun maliyetle kullanılması olarak tanımlanmaktadır. Bu çalışma kapsamında, özel bir üniversite hastanesinde hekimler tarafından istemi yapılan profilaktik antibiyotiklerin, Enfeksiyon Hastalıkları Uzmanı konsültasyonu olmadan kullanımının sınırlandırılması ve bu sınırlandırma sonrasındaki kullanım oranlarının tahmin edilmesi hedeflenmiştir. Geleceğe dair tahminler tespit edilen sorunları azaltılamayacak olsa da sorunlara karşı alınacak önlemlerin belirlenebilmesine imkan sunar. Gerçekleştirilen uygulamada profilaktik antibiyotik kullanım oranları Dünya Sağlık Örgütü tarafından geliştirilen ve dünya çapında kabul görmüş DDD/ATİ yöntemi ile hesaplanarak elde edilmiştir. Hastane bünyesinde uygulanan konsültasyon gerekliliği politikasının profilaktik antibiyotik kullanım oranlarının azaltılması açısından katkı sağlayıp sağlamayacağı hususu irdelenmek istenmiştir. Elde edilen veriler geçmişe ait veriler olması nedeniyle ve geleceğe dair tahmin çıktısı alınmak istenmesi nedeniyle zaman serisi tahmin yöntemleri tercih edilmiştir. Bu doğrultuda, zaman serisi yöntemlerinden Otoregresif Entegre Hareketli Ortalama (Autoregressive Integrated Moving Average-ARIMA) yöntemi kullanılarak gelecek yılın kullanım oranları tahmin edilmiştir. Çalışmada kullanılan ARIMA tahmin modellerinin uygunluğu sorgulanmış ve hata oranları kabul edilebilir seviyede olan tahmin değerleri elde edilmiştir. Model çıktıları üzerinden MAPE, R2 ve AIC değerleri değerlendirmeye tabii tutulmuştur. Gelecek yıl için tahmin edilen veriler üzerinden değerlendirme yapıldığında uygulanan konsültasyon gerekliliği politikasının profilaktik antibiyotik kullanım oranlarının azaltılmasında başarılı olacağına karar verilmiştir.Öğe Defining criteria weights by ahp in health technology assessment(Elsevier Sciences, 2017) Örtürk, N.; Karacan, İlknur; Tozan, Hakan; Vayvay, ÖzalpObjectives: Multi Criteria Decision Making (MCDM) is claimed to be the aid for Health Technology Assessment (HTA) based decision making. Transparent commitment of multi-disciplinary stakeholders is essential to attain public confidence in healthcare decision making. In current deliberative process commitment of stakeholders is not transparent. This research aims to propose a prioritization approach for MCDM applications in HTA by Analytic Hierarchy Process (AHP).Öğe Eritrosit envanter yönetiminde derin pekiştirmeli öğrenme(İstanbul Medipol Üniversitesi, Fen Bilimleri Enstitüsü, 2022) Şengil, Ahmed Arif; Tozan, Hakan; Köse, Kevser BanuDünya çapında en yaygın olarak uygulanan tedavi yöntemlerinden birisi kan transfüzyonudur. Sağlığın korunmasında ve hayatların kurtarılmasında kan ürünlerinin doğru bir şekilde temini çok önemli bir rol oynamaktadır. Her yıl, güvenli ve taze eritrosit erişimi sayesinde yüz binlerce hastanın hayatı kurtarılmaktadır. Dolayısıyla, kan kıtlığı sorununu çözebilmek ve kan talebinin ihtiyaçlarını karşılayabilmek için hastane düzeyinde de verimli bir kan ürünleri talep ve arz yönetimi sağlamak ve kan tedarik düzeyini yükseltmek ciddi bir ihtiyaçtır. Dünya çapında hastanelerin ortak hedefi, hizmet verilebilen hasta sayısını en üst düzeye çıkararak ve kan israfını azaltarak mevcut kan birimlerini daha iyi kullanmaktır. Kanı yönetmek zordur çünkü kan ürünleri bozulabilir ürünlerdir, arz stokastiktir ve talepler oldukça belirsiz bir şekilde gerçekleşmektedir. Ek olarak, eritrositler farklı gruplara ayrılmaktadırlar ve hasta uyumluluğu gerektirmektedirler. Pekiştirmeli öğrenme, dinamik ortamlarda sıralı karar verme problemlerini çözmek için geliştirilmiştir ve envanter yönetimi için ilgi çekici bir yöntemdir. Ölçeklendirilebilir, karmaşık problemlerde dahi optimal politikalara yakınsayabiliyor olmaları sebebiyle pekiştirmeli öğrenme metodları arasından yalnızca derin pekiştirmeli öğrenme yöntemleri dikkate alınmıştır. Son zamanlarda, derin pekiştirmeli öğrenme, birçok disiplinde sıralı karar verme problemleri için büyük potansiyel göstermiştir. Derin pekiştirmeli öğrenme, geleneksel yaklaşımlar kullanılarak elde edilmesi zor olan optimuma yakın politikalar geliştirmek için kullanılabilmektedir. Ancak, Boute ve diğerlerinin (2021) kanıtladığı gibi, derin pekiştirmeli öğrenme algoritmaları, geleneksel yöntemlerle elde edilmesi zor, veya hatta bazı durumlarda imkansız olan optimuma yakın politikalar geliştirmek için kullanılabilmelerine rağmen, envanter kontrol alanında yeterli düzeyde uygulanmamışlardır. Bu çalışma, hastane düzeyinde kan envanteri yönetimini iyileştirmek için pekiştirmeli öğrenme ve derin öğrenmedeki son gelişmelerden yararlanmaktadır. Kan bankası envanter yönetiminde derin pekiştirmeli öğrenme yöntemlerinden yararlanılıp yararlanılamayacağı, veya nasıl yararlanabileceği araştırılmıştır. Bu doğrultuda, İstanbul'da bulunan büyük ölçekli özel bir hastane örnek olarak ele alınarak eritrosit envanter yönetimi farklı kan grupları için derin pekiştimeli öğrenme yöntemi ile modellenmiştir. Kullanılan Proksimal Politika Optimizasyonu [1] algoritmasının tüm kan gruplarında optimale yakın seviyelerde performans gösterebilecek sipariş politikaları yakınsayabildiği gözlemlenmiştir. Derin pekiştirmeli öğrenme yöntemi kullanılarak kan ürünleri envanter yönetiminden sorumlu uzmanlara sipariş kararları konusunda destek olabilecek modeller kurulabileceği tespit edilmiştir.Öğe Experimental measurement of a UAV propeller's thrust(University of Osijek, 2022) Kosa, Patrik; Kisev, Marian; Vacho, Lukas; Toth, Ladislav; Olejar, Martin; Harnicarova, Marta; Valicek, Jan; Tozan, HakanAt present, there are several types of propellers in the field of the use of Unmanned Aerial Vehicles (UAVs) with unknown parameters, where it is necessary to provide information about their thrust, current consumption and maximal rotational speed (RPM). Commonly used methods for measurement of a propeller's thrust are mostly based on the usage of a single purpose system, on short measurements without data storage or on inaccurate sensors. The goal of this article is to develop a universal experimental measuring system for more accurate measurement of propeller's parameters (thrust, current consumption, maximal RPM). For more accurate measurement, the battery voltage, temperature and humidity of the environment were also measured. To acquire, measure and store the data safely on a micro SD card, a processing circuit based on an ATmega2560 microcontroller was developed. This innovative approach allowed to analyse the behaviour of the propeller and to measure the dependencies of the RPM on pulse width, of the current on RPM and of the thrust on RPM at different input conditions. The measurements have shown that the dependencies can be approximated by cubic functions. The mathematical description allows predicting the behaviour of the propeller in unmeasurable conditions.
