Browsing by Author "Dengiz, Berna"

Now showing 1 - 20 of 57

Aintshop Production Line Optimization Using Response Surface Methodology
(2007) Dengiz, Berna; Belgin, Onder; 0000-0001-6702-2608; K-1080-2019
This paper deals with the problem of determining the optimum number of workstations to be used in parallel and workers at some stations using simulation optimization approach in a paint shop line of an automotive factory in Ankara, Turkey. In the optimization stage of the study Response Surface Methodology (RSM) is used to find the optimum levels of considered factors. Simulation model and optimization stage integration is used both to analyse the performance of the current paint shop line and determine the optimum working conditions, respectively, with reduced cost, time and effort.
Airfoil-slat arrangement model design for wind turbines in fuzzy environment
(2020) Atalay, Kumru Didem; Dengiz, Berna; Yavuz, Tahir; Koc, Emre; Ic, Yusuf Tansel
In this study, a multi-element wind turbine blade that consists of NACA 6411 and NACA 4412 leading-edge slat design is investigated computationally. Optimum design parameters of the slatted wind turbine blade leading to maximum value of C-L/C-D related to the turbine power are obtained. In the optimization process, a new fuzzy logic linear programming methodology integrating with fuzzy linear regression and 2D CFD analysis is proposed. The aerodynamic characteristics of the slatted blade are computed by using Incompressible Navier-Stokes equations and k-omega turbulence modeling. Results are compared with the results of linear programming method and direct search optimization method. The computational results reveal that the proposed methodology for performance optimization is more effective than other methods to obtain high-performance value of the C-L/C-D. The maximum value of the C-L/C-D is obtained as 25.1 leading the maximum efficiency of 0.52.
Analysis of the manufacturing flexibility parameters with effective performance metrics: a new interactive approach based on modified TOPSIS-Taguchi method
(2022) Ic, Yusuf Tansel; Sasmaz, Turgut; Yurdakul, Mustafa; Dengiz, Berna; 0000-0001-9274-7467; AGE-3003-2022
Flexibility is one of the most important strategy parameters to achieve a long-term successful performance for a manufacturing company. Studies in the literature aim to operate a manufacturing system at optimum levels of flexibility parameters under its own manufacturing environment. This study aims to present an interactive analysis framework based on TOPSIS and Taguchi parameter design principles for investigating the effects of different levels of flexibility parameters on the performance of a flexible manufacturing cell (FMC). The main performance metric used in this study is manufacturing lead time. Other important metrics to evaluate quality control and inspection policies are also investigated in this study. To conclude, a combined model of an interactive approach based on TOPSIS and Taguchi methods are used to assess the effectiveness of the flexibility parameters for a FMC.
Analysis of the Robustness of the Operational Performance Using a Combined Model of the Design of Experiment and Goal Programming Approaches for a Flexible Manufacturing Cell
(2023) Ic, Yusuf Tansel; Yurdakul, Mustafa; Dengiz, Berna; Sasmaz, Turgut
A combined model of a 2(k) design of experiment (DOE) and goal programming (GP) approaches is presented to determine optimum levels of input variables and analyze their robustness for a multiobjective performance of a flexible manufacturing cell (FMC) in this study. Two main performance metrics, namely, manufacturing lead time (MLT) and surface roughness (SR), are considered performance outputs for the FMC. Machine sequence, robot speed, tool type, and material type are selected as the four input variables on the input side of the proposed model. The study shows that even with a limited number of experiments, one can determine optimum input levels for the multiobjective performance of the FMC and determine their robustness.
Applications of Deep Learning Techniques to Wood Anomaly Detection
(2022) Celik, Yaren; Guney, Selda; Dengiz, Berna; Xu, J; Altiparmak, F.; Hassan, MHA; Marquez, FPG
Wood products and structures have an important place in today's industry. They are widely used in many fields. However, there are various difficulties in production systems where wood raw material is under many processes. Some difficulty and complexity of production processes result in high variability of raw materials such as a wide range of visible structural defects that must be checked by specialists on line or of line. These issues are not only difficult and biased in manual processes, but also less effective and misleading. To overcome the drawbacks of the manual quality control processes, machine vision-based inspection systems are in great of interest recently for quality control applications. In this study, the wood anomaly has been detected by using deep learning. As it will be a distinction-based method on image processing, the Convolution Neural Network (CNN), which is one of the most suitable methods, has been used for anomaly detection. In addition, it will be tried to obtain the most suitable one among different CNN architectures such as ShuffleNet, AlexNet, GoogleNet for the problem. MobileNet, SqueezeNet, GoogleNet, ShuffleNet among considered methods show promising results in classifying normal and abnormal wood products.
Arıza ve tamir durumunda sistem güvenilirliği: Genetik ve memetik algoritmalar
(Başkent Üniversitesi Fen Bilimleri Enstitüsü, 2021) Uzuner Şahin, Merve; Dengiz, Berna
İleri teknolojiye sahip sistemlerin, örneğin iletişim, elektronik, uzay sistemleri gibi modern mühendislik sistemlerinin, giderek karmaşıklaşan yapısı ve işleyiş süreçleri, bu sistemlerin daha etkin bir şekilde değerlendirilmesinin önemini artırmıştır. Karmaşık yapıdaki bu tür sistemlerin tasarımı ve analizi ile ilgili çalışmalarda başarımlarının değerlendirilmesi için alan yazında yaygın olarak kullanılan ölçütlerinden birisi sistem güvenilirliğidir. Sistem güvenilirliği kavramı genel anlamda bir sistemin amacına uygun olarak çalışmasını ifade etmektedir. Problem türlerine bağlı olarak tanımlanan sistem kısıtları altında sistem güvenilirliğinin eniyilenmesi önemli ve her zaman araştırmacıların ilgisini çeken bir problemdir. Alan yazında yaygın olarak kullanılan Yedek Bileşen Tahsis Problemi (YBTP), sistemde yer alan bileşenlere paralel olarak yerleştirilen, kullanıma hazır bileşenler ile daha yüksek güvenilirliğe sahip yeni sistemlerin tasarlanması olarak tanımlanabilir. YBTP NP-zor bir problemdir. YBTP ile ilgili çalışmaların çoğunda genellikle yalnızca arızalar dikkate alınırken, çok az sayıdaki çalışmada arıza ve tamir durumunun sabit arızalanma oranlarıyla dikkate alındığı görülmüştür. Oysa, gerçek hayat problemlerinde sistemi oluşturan bileşenler kullanımdan kaynaklanan yıpranmaya bağlı olarak artan arızalanma oranına sahiptir. Diğer yandan alan yazındaki mevcut YBTP çalışmalarında, hesaplama zorluğu nedeniyle, genellikle bileşenlerin arızalandıktan sonra tamir edilmediği ve dolayısıyla devre dışı kaldığı varsayımı kullanılmaktadır. Doğal olarak bu varsayım sistemlerin ilk tasarımlarında maliyeti artırmaktadır. Gerçek hayatta kullanılan sistemlerde ise, arızalanan bir bileşen sistemin güvenilirliği negatif yönde etkilerken, tamir edilen bileşen sistemin güvenilirliğini pozitif yönde etkilemektedir. Gerçek hayatta kullanılmakta olan bir sistemin bu doğal yapısı dikkate alınarak yüksek güvenilirliğe sahip tasarımlar daha düşük maliyetle elde edilebilir. Ayrıca, YBTP’de güvenilirlik kısıtı olarak kullanılan, n’den k’lı (k-out-of-n) varsayımında “k” parametresi değişen servis sağlayıcı taleplerine bağlı olarak değişkenlik göstermelidir. Bu nedenle YBTP’de “k” parametresinin değişiminin de dikkate alındığı dönemsel talep değişimlerini karşılayacak sistem tasarımlarının oluşturulması önemlidir. Bu tez çalışmasında, artan arızalanma oranları ile ortaya çıkan bozulmaların, tamirlerin ve değişken “k” değerinin dikkate alındığı durumda YBTP’nin eniyilenmesi için Genetik Algoritma (GA) ve Memetik Algoritma (MA) olmak üzere iki metasezgisel algoritma önerilmiştir. Sistem güvenilirliği (amaç fonksiyonu) gerçekçi bir yaklaşımla olayların çıkışına dayalı olarak geliştirilen kesikli olaylı benzetim (KOB) modelinin kullanıldığı kesikli olaylı Monte Carlo benzetimi ile tahmin edilmiştir. KOB modelinin geçerliliği ve geliştirilen GA ve MA’nın etkinlikleri alan yazında yaygın olarak kullanılan test problemleri üzerinde gösterilmiştir. Sayısal analiz sonuçlarına göre, GA ve MA’nın kaliteli çözümler bulduğu; MA’nın GA’ya göre daha iyi sonuçlar verdiği gösterilmiştir. Böylece, arıza ve bozulmanın dikkate alındığı YBTP için daha yüksek güvenilirliğe sahip sistem tasarımlarının daha düşük maliyetle elde edilebildiği probleme özgü iki algoritma, GA ve MA, ilgili alan yazına kazandırılmıştır. Due to the increasing complexity of structures and functions of high-tech systems, such as modern engineering and service systems in the communication, electronics, and space technology fields, the need for effective evaluation tools for such systems has increased in parallel. In the analysis and design of complex systems, the system reliability is one of the performance criteria commonly used in the literature to evaluate performance. The concept of system reliability generally refers to the operation of a system in accordance with its purpose. The reliability optimization of a system with various problem-specific constraints is an important and current problem. The Redundancy Allocation Problem (RAP), which is widely used in the literature, can be defined as the design of new systems with higher reliability using redundant components in a parallel arrangement. The RAP is an NP-hard problem. While most of the studies on RAP generally only consider failures, few studies are based on the assumption that failures and/or repairs occur at constant rates. However, in real-life problems, the components in the system have an increased failure rate due to wear and tear from regular use. Due to the computational difficulty in RAP studies, it is generally assumed that components are not repaired after they fail and thus become out of order. Without an opportunity to repair a failed part, the initial cost of the system increases. Under such circumstances, the system has to be designed with better components (i.e., highly reliable but expensive) to maintain the overall system reliability at the desired level. In real-life applications, a component failure has a negative impact on system reliability. After the failed component is repaired and put back to work, the reliability of the system increases. Structures designed with repair considerations are more realistic, and high reliability can be obtained at a lower cost by using this approach. In addition, the “k” parameter in the metrics (k-out-of-n) is dynamically adjusted according to changing user requirements. The (k-out-of-n) metric is used as a reliability constraint in RAP, and the introduction of a dynamic “k” facilitates the design of adoptable systems to seasonal changes in demand. In this thesis, two metaheuristic algorithms, Genetic Algorithm (GA) and Memetic Algorithm (MA) are proposed to optimize RAP with increasing failure rates, component repairs, and dynamic “k”. The system reliability (objective function value) in the RAP optimization is estimated with a discrete event Monte Carlo simulation with discrete event simulation (DES) model, which is developed according to the occurrence of events with a realistic approach. The validity of the DES model has been demonstrated on the test problems given in the literature. The effectiveness of the developed GA and MA is shown on the test problems that are widely used in the literature. According to the computational analysis, GA and MA found quality solutions. It has been shown that MA gives better results than GA. Thus, problem-specific GA and MA for RAP designs with higher reliability at lower cost, where failure and repair are taken into account, have been developed and brought to the relevant literature.
Automated Tuberculosis Detection Using Pre-Trained CNN and SVM
(2021) Oltu, Burcu; Guney, Selda; Dengiz, Berna; Agildere, Muhtesem
Tuberculosis (TB) is a dreadfully contagious and life-threatening disease if left untreated. Therefore, early and accurate diagnosis is critical for treatment. Today, invasive, expensive, or time-consuming tests are performed for diagnosis. Unfortunately, accurate TB diagnosis is still a major challenge. In the proposed study, a decision support system that can automatically separate normal and TB chest X-ray (CXR) images is presented for objective and accurate diagnosis. In the presented methodology, first various data augmentation methods were applied to the data set, then pre-trained networks (VGG16, MobileNet), were employed as feature extractors from augmented CXR's. Afterward, the extracted features for all images were fed into a support vector machine classifier. In training process, 5-fold cross-validation was applied. As a result of this classification, it was concluded that TB can be diagnosed with an accuracy of 96,6% and an area under the ROC curve (AUC) of 0,99.
Bağımsız denetimde finansal tablolar hesap grupları düzeyinde risk olarak değerlendirilmiş hususlara karşı uygulanacak müteakip denetim prosedürlerini üzerine bir uygulama
(Başkent Üniversitesi Sosyal Bilimler Enstitüsü, 2022) Yörübulut, Ömer Salim; Dengiz, Berna
Küreselleşmenin etkisi ile ticari hayatta ortadan kalkan sınırlar ve teknolojik anlamda yaşanan hızlı gelişmeler neticesinde, farklı coğrafyalarda faaliyet gösteren şirketler açısından, faaliyetlerin çıktısı niteliğindeki finansal tabloların şeffaflığı, doğruluğu son derece önemli bir konu olarak değerlendirilmektedir. Finansal tabloların tüm paydaşlar tarafından anlaşılması ve küresel anlamda kabul görmüş standartlar ile paralellik göstermesi günümüz şirketleri açısından en önemli hususlardan biridir. Bu noktada, bağımsız denetim faaliyetlerinin önemi ortaya çıkmaktadır. Bağımsız denetim, finansal tablo ve eklerinin, genel kabul görmüş raporlama standartlarına uygunluğunu ve doğruluğunu denetleyen, denetim standartları kapsamındaki tekniklerin uygulanması sureti ile şirketlerin kayıt ve belgelerini inceleyen bir süreçtir. Bu çalışmada, bağımsız denetim süreçlerinde risklerin ortaya konulması ve değerlendirilmesine yönelik olarak maddi doğrulama prosedürlerine yönelik uygulama yapılmıştır. Bu örnek uygulama sayesinde bağımsız denetim sektörüne yeni başlayan veya başlayacak olan kişilere, denetim sürecinde belirlenen risklere karşı uygulanabilecek maddi doğrulama prosedürleri ve uygulamaları hakkında bilgi verilmeye çalışılmıştır. As a result of the borders disappearing in commercial life with the effect of globalization and rapid technological developments, the transparency and accuracy of the financial statements, which are the output of their activities, are considered as an extremely important issue for companies operating in different geographies. The understanding of financial statements by all stakeholders and their parallelism with globally accepted standards is one of the most important issues for today's companies. At this point, the importance of independent audit activities emerges. Independent auditing is a process that checks the compliance and accuracy of financial statements and their annexes with generally accepted reporting standards, and examines the records and documents of companies by applying the techniques within the scope of auditing standards. In this study, an application has been made for the subsequent audit procedures to reveal and evaluate the risks in the independent audit processes. Thanks to this sample application, it has been tried to give information about the substantive procedures and practices that can be applied against the risks determined during the audit process, to those who have just started or will start the independent audit industry.
Bir Fizik Tedavi Biriminde Randevu Çizelgeleme ve Karar Destek Sistemi
(Başkent Üniversitesi Fen Bilimler Enstitüsü, 2022) Altınbas, Elif; Dengiz, Berna
Hızlı nüfus artışı ve beraberinde sağlık problemleri, sağlık kurum ve kuruluşlarına olan taleplerdeki artış yoğunluğa sebep olmaktadır. Bu nedenle sağlık kuruluşlarında güvenli ortamların oluşturulması ve en iyi hizmetin sunulması iyi bir planlama ve bu planlamanın uygulanmasının sürdürülebilir olması ile sağlanabilir. Son yıllarda sağlık bakım hizmetleri sunan (sağlık hizmeti üreten) kuruluşlar da üretim sistemlerine benzer şekilde yalın sağlık bakım anlayışını kullanarak daha çok hastaya daha iyi hizmet vermek amacıyla çalışmalar yapmaktadır. Yalın sağlık anlayışı, değer katmayan faaliyetlerin elimine edilmesi anlamına gelmektedir. Dolayısıyla değer katmayan faaliyetlerin saptanarak azaltılması için yönetim ve işleyişte iyileştirmelere ihtiyaç duyulmaktadır. Çalışan nüfusun, yaşlı nüfusunun giderek arttığı ülkemizde fizik tedavi gerektiren hastalıklar da doğal olarak artmaktadır. Bu nedenle fizyoterapi birimlerine olan talep artmakta, endüstri mühendisliği yaklaşımlarının kullanılmadığı bu tür işletmelerde yönetim ve işleyişte problemler ortaya çıkmaktadır. Bu tez çalışmasında, İstanbul’da hizmet veren bir fizik tedavi merkezi ele alınarak sistemde var olan randevu çizelgeleme probleminden kaynaklı hasta ve maliyet kayıplarının en azlanmış (elimine edilmiş) sağlıkta yalın anlayışı ile çalışacak bir Karar Destek Sistemi (KDS) geliştirilmiştir. Önerilen KDS için randevu çizelgeleme problemini çözen hasta hareketine göre (fizyoterapi merkezine yeni başvuran, tedavisi devam etmekte olan ve ayrılan (tedavisi biten veya tedaviyi bırakan)) mevcut kapasiteyi, işletmenin stratejik ve özel kısıtlarını ve Sosyal Güvenlik Kurumunun (SGK) yönetmeliklerini dikkate alan matematiksel model kurulmuş, veri alt yapısı oluşturulmuştur. Böylece yalın sağlık hizmeti sunmak amacıyla günlük hasta oranını en çok yapan en uygun randevu ve tedavi planları oluşturulabilecektir.Rapid population growth and accompanying health problems, and the increase in demands for health institutions and organizations cause too much patient density. For this reason, creating safe environments in health institutions and providing the best service can be achieved with good planning and sustainability of the implementation of this planning. In recent years, organizations that provide health care services (health care providers) have been working to provide better service to more patients by using a lean health care approach, similar to their production systems. Lean health approach means eliminating activities that do not add value. Therefore, improvements in management and operation are needed to identify and reduce non-value adding activities. In our country, where the working population and the elderly population are increasing, diseases that require physical therapy are also increasing naturally. BecauseThe demand for physiotherapy units is increasing, and problems arise in management and functioning in such enterprises where industrial engineering approaches are not used. In this thesis, a Decision Support System (DDS) was developed, which will work with a lean understanding in health, where the patient and cost losses due to the appointment scheduling problem in the system are minimized (eliminated) by considering a physical therapy center serving in Istanbul. A mathematical model has been established and a data infrastructure has been established, taking into account the current capacity, strategic and special constraints of the enterprise, and the regulations of the Health Security System (SGK) according to the patient movement that solves the problem (newly applying to the physiotherapy center and leaving (the treatment is finished or the treatment is discontinued)) . Thus, in order to provide lean health services, the most appropriate appointment and treatment plans with the highest daily patient rate will be created.
Bir işletmede güvenilirlik analizlerine dayalı sistem tasarımı
(Başkent Üniversitesi Fen Bilimleri Enstitüsü, 2015) Uzuner, Merve; Dengiz, Berna
Bu çalıĢmada, Yiğit Akü A.ġ. akü üretim sisteminde, belli bir tip akünün üretildiği üretim hattında var olan problemler belirlenmiĢ ve verimlilik artıĢı sağlayacak yeni tasarım(lar) önerilmiĢtir. Akü üretim sisteminde, üretim aĢamalarının çoğunda oluĢabilecek kimyasal reaksiyonlar nedeniyle aküler etkilenebilmektedir. Bu nedenle akü üretim sistemleri çok dikkatli ve özenli olarak çalıĢılması gereken alanlardır. Akü üretim aĢamalarının hassas ve dikkatli olarak gerçekleĢtirilebilmesi için hem sistem içerisinde görevli operatörlerin hem de sistemde çalıĢan makinelerin sürece uygun ve düzgün Ģekilde çalıĢmaları gerekmektedir. Bunun yanı sıra, üretim sisteminin iĢlevlerini doğru ve düzgün bir Ģekilde yerine getirebilmesi yani güvenilirliğin dolayısıyla kullanılabilirlik oranının yüksek olması sonucu üretilen ürünün doğru ve amacına uygun olarak çalıĢması beklenir. Sistemin ve sistem bileĢenlerinin nitelikli çalıĢma zamanları ve oranlarını analiz etmek için kullanılabilecek yöntemlerden biri güvenilirliktir. Güvenilirlik kavramı, ürünlerin ve sistemlerin güvenilirliği olmak üzere iki ana baĢlık altında incelenebilir. Ürün güvenilirliği, nihai ürünün amacına uygun olarak çalıĢmasını ifade etmek için kullanılırken, sistem güvenilirliği ise bir sistemin amacına uygun olarak çalıĢmasını ifade etmektedir. Bilindiği gibi akü, araçların ana güç elemanıdır. Aküde oluĢabilecek herhangi bir arızanın (uygun çalıĢmamanın) kiĢi ya da kiĢilerin hayatında herhangi bir aksaklığa yol açmadan kısa bir sürede ortadan kaldırılması mümkün olamamaktadır. Bu nedenle güvenilirliklerinin ve kullanılabilirliklerinin yüksek olması istenir. Ürünlerin güvenilirliklerinin yüksek olabilmesi için üretim sistemlerinin güvenilirlik tahminleri önem kazanmaktadır. Sistem tasarımının güvenilirlik değerlendirmesine ii dayalı olarak yapılması üretim sistemlerinde son yıllarda kullanılmakta olan bir yaklaĢımdır. Bu tez kapsamında; sistemi oluĢturan bileĢenlerin güvenilirlikleri ayrı ayrı hesaplanmıĢ ve sistemin güvenilirlik eĢitliği güvenilirlik blok diyagramları kullanılarak elde edilmiĢtir. Elde edilen güvenilirlik eĢitliği kullanılarak daha güvenilir dolayısıyla kullanılabilirliği daha yüksek bir tasarım elde edilmiĢ ve sistemin bu yolla iyileĢtirilmesi sağlanmıĢtır. Ele alınan sistemde hammadde kısıtı olmaması nedeniyle kullanılabilirlik değerine bağlı olarak haftalık üretim miktarı tahmin edilemeyeceği için bu aĢamada benzetim yönteminden yararlanılmıĢtır. Bu çalıĢmada elde edilen bulgularla Yiğit Akü A.ġ., ürün güvenilirlikleri ve bununla bağlantılı olarak sisteminin güvenilirliği hakkında bilgi sahibi olacak, bu güvenilirlik değerlerini mümkün olduğunca yüksek seviyede tutmak için tasarımlarını değiĢtirme çabası içinde olacaktır. Bu tezde, benzetim modeli, mevcut ve önerilen yeni tasarımlardan üretilebilecek ürün sayılarını önceden tahmin edebilmek amacıyla kullanılmıĢtır. Ayrıca, kullanılması önerilen yöntemlerle üretim sisteminin genel kullanılabilirliği ve üretim planlaması dikkate alınarak üretim planının hangi oranda gerçekleĢebileceği bilgisi de elde edilebilmektedir. Bu sayede, uygulamada, firmanın üretim bölümü ile planlama bölümü arasındaki koordinasyonun yürütülmesine yardımcı olacak bilgi sağlanabilmektedir. Bu çalıĢma, kullandığı yöntemler açısından üretim sistemlerinde ilk birkaç uygulamadan biri olup imalat sektöründe çalıĢan mühendislerin benzer yöntemleri kullanmasında rehber olacaktır. In this study, problems are identified and new design(s) has been proposed to ensure increased efficiency for a particular type of battery production line in the battery production system of Yigit Battery Corporation. Batteries can be influenced by the chemical reaction occurring in the majority of production in the battery production systems. Therefore battery production systems need to be studied very carefully and conscientiously. Both workers and machines in system should work properly and correctly to work carefully and sensitively of battery production process. In addition, it is expected to work in accordance with right and scope of the products which are produced in the process, if the production system‟s functions are performed correctly and properly, in other words the process has high reliability and so high avalibility. One of the methods can be used to analyze the quality and rate of system and system components‟ run-time periods is reliability. The concept of reliability can be identified two main part, product reliability and system reliability. Product reliability is used for working according to the purpose of the final product. System reliability is used for working according to the purpose of the system. As is known, the battery is the main power component of the vehicles. Any failure of the battery (not to work appropriately) could not be eliminate in a short time without causing any disruption on a somebodys‟ life. Therefore, it is desired to have high reliability and availability. For having a high product reliability, reliability estimations of production systems are important. Performing system design based on reliability assessment is an approach which is used in production systems in recent years. iv In this thesis, system components‟s reliability are calculated and system reliability equation is obtained using reliability block diagram. More reliable and so high availability system design is obtained with using the equation and in this way system improvement is ensured. In the considered system, there is not any supply constraints about raw material and soweekly production amount could not be estimated using availability. Therefore, in this part, simulation method was used. Yigit Battery Company will have a knowledge about product reliability and system reliability with the findings of this study, and so, it is made an effort to keep a high reliability level as possible. In this thesis, simulation model is used to predict the number of products that can be produced in current system design and proposed new designs. In addition, in according to overall system availability and production plan, it can be had a knowledge about production plan‟s realization with these proposed methods. Thus, in practice, this knowledge can be provided to help company to conduct of coordination between the production department and planning department. In this study, one of the few applications is used these methods in the production systems and it will be guide working engineers in manufacturing sector using similar methods.
Buffer Allocation and Performance Modeling in Asynchronous Assembly System Operations: An Artificial Neural Network Metamodeling Approach
(2007) Altiparmak, Fulya; Dengiz, Berna; Bulgak, Akif A.; 0000-0003-1730-4214; AAF-7020-2021
This article investigates metamodeling opportunities in buffer allocation and performance modeling in asynchronous assembly systems ( AAS). Practical challenges to properly design these complex systems are emphasized. A critical review of various approaches in modeling and evaluation of assembly systems reported in the recently published literature, with a special emphasis on the buffer allocation problems, is given. Various applications of artificial intelligence techniques on manufacturing systems problems, particularly those related to artificial neural networks, are also reviewed. Advantages and the drawbacks of the metamodeling approach are discussed. In this context, a metamodeling application on AAS buffer design/performance modeling problems in an attempt to extend the application domain of metamodeling approach to manufacturing/assembly systems is presented. An artificial neural network ( ANN) metamodel is developed for a simulation model of an AAS. The ANN and regression metamodels for each AAS are compared with respect to their deviations from the simulation results. The analysis shows that the ANN metamodels can successfully be used to model of AASs. Consequently, one concludes that practising engineers involved in assembly system design can potentially benefit from the advantages of the metamodeling approach. (c) 2006 Elsevier B. V. All rights reserved.
Comparative Study for Tuberculosis Detection by Using Deep Learning
(2021) Karaca, Busra Kubra; Guney, Selda; Dengiz, Berna; Agildere, Muhtesem
Tuberculosis (TB) is an infectious disease which becomes a significant health problem worldwide. Many people have been affected by this disease owing to deficiency of treatment and late or inaccuracy of diagnosis. Therefore, accurate and early diagnosis is the very major solution to checking and preventing the disease. A chest x-ray is a main diagnostic tool used to diagnose tuberculosis. This diagnostic method is limited by the availability of radiologists and the experience and skills of radiologists in reading x-rays. To overcome such a challenge, a computer-aided diagnosis (CAD) system is supposed for the radiologist to interpret chest x-ray images easily. In this study, a CAD system based upon transfer learning is developed for TB detection using Montgomery Country chest x-ray images. We used the VGG16, VGG19, DenseNet121, MobileNet, and InceptionV3 pre-trained CNN models to extract features automatically and used the Support Vector Machine (SVM) classifier to the detection of tuberculosis. Furthermore, data augmentation techniques were applied to boost the performance results. The proposed method performed the highest accuracy of 98.9% and area under the curve (AUC) of 1.00, respectively, with the DenseNet121 on augmented images.
Crew Pairing Optimization Based On Hybrid Approaches
(2013) Aydemir-Karadag, Ayyuce; Dengiz, Berna; Bolat, Ahmet
The crew pairing problem (CPP) deals with generating crew pairings due to law and restrictions and selecting a set of crew pairings with minimal cost that covers all the flight legs. In this study, we present three different algorithms to solve CPP. The knowledge based random algorithm (KBRA) and the hybrid algorithm (HA) both combine heuristics and exact methods. While KBRA generates a reduced solution space by using the knowledge received from the past, HA starts to generate a reduced search space including high quality legal pairings by using some mechanisms in components of genetic algorithm (GA). Zero-one integer programming model of the set covering problem (SCP) which is an NP-hard problem is then used to select the minimal cost pairings among solutions in the reduced search space. Column generation (CG) which is the most commonly used technique in the CPP literature is used as the third solution technique. While the master problem is formulated as SCP, legal pairings are generated in the pricing problem by solving a shortest path problem on a structured network. In addition, the performance of CG integrated by KBRA (CG_KBRA) and HA (CG_HA) is investigated on randomly generated test problems. Computational results show that HA and CG_HA can be considered as effective and efficient solution algorithms for solving CPP in terms of the computational cost and solution quality. (C) 2011 Elsevier Ltd. All rights reserved.
A cross entropy approach to design of reliable networks
(2009) Dengiz, Berna; Altiparmak, Fulya; 0000-0003-1730-4214; AAF-7020-2021
One of the most important parameters determining the performance of communication networks is network reliability. The network reliability strongly depends on not only topological layout of the communication networks but also reliability and availability of the communication facilities. The selection of optimal network topology is an NP-hard problem so that computation time of enumeration-based methods grows exponentially with network size. This paper presents a new solution approach based on cross-entropy method, called NCE, to design of communication networks. The design problem is to find a network topology with minimum cost such that all-terminal reliability is not less than a given level of reliability. To investigate the effectiveness of the proposed NCE, comparisons with other heuristic approaches given in the literature for the design problem are carried out in a three-stage experimental study. Computational results show that NCE is an effective heuristic approach to design of reliable networks. (C) 2008 Elsevier B.V. All rights reserved.
Demiryolu araçları temini için teknoloji yönetimi
(Başkent Üniversitesi Fen Bilimleri Enstitüsü, 2016) Öz, Ahmet; Dengiz, Berna
Günümüzde Teknoloji Yönetimi (TY) faaliyetleri ve araçları karar vericiler için giderek önem kazanmaktadır. Teknolojilerin temini ve kullanımı sürecinde TY faaliyet ve araçlarının doğru bir şekilde yönetilmesi karmaşık ve zor gibi görünen faaliyetleri kolaylaştırmakta ve sistemleri daha iyi organize etmektedir. Büyük kamu alımlarında ülke ekonomisine, sanayisine ve araştırma – geliştirme faaliyetlerine olumlu katkıda bulunması amacıyla sivil bir offset programı olan Sanayi İşbirliği Programı (SİP) yürürlüğe girmiştir. Bahsedildiği üzere SİP sözleşmesinde geçen yatırım, ihracat ve teknolojik işbirliği kategorileri gereksinimlerinin karmaşıklığı, bu çalışmada ayrıntılı bir şekilde aktarılan teknoloji yönetimi faaliyetleri ve demiryolu sektöründeki örnek olaylar ile anlaşılır bir zemine oturtulmuştur. Çalışmanın konusu olarak ülkemizde son yıllarda artan demiryolu araçları teminlerinde teknolojileri tanımlamak, seçmek, kullanmak ve paydaşlar arasındaki iş birliklerini artırmak için ekonomik, teknik, işletme kriterleri ile sözleşmelerde geçen fiyat dışı unsurları için önerilerde bulunulmuş ve örnek olaylardan yola çıkarak belirleyici başka kriterler tespit edilmiştir. Son olarak büyük çaplı kamu alımlarında teknolojilerin belirlenmesinden başlayarak seçimi, edinimi, kullanımı, korunması ve ihale sürecinin daha etkin ve verimli yürütülmesi amacıyla demiryolu araçları temin etmek isteyen idareler için referans alınabilecek bir teknoloji yönetimi modeli akış diyagramı şeklinde geliştirilmiştir. More recently, Technology Management (TM) activities and tools have been gained ever-increasingly importance by managers and decision makers. In the process of technology acquisition and exploitation, proper execution of TM tools will be able to lead to make long and complicated processes easier to be managed and to be better organised of systems. For the purpose of more and more contribution to Turkey’s economy, science and research – development capabilities by means of the large public procurements, Industrial Cooperation Program (ICP) as a civil offset regulation has been gone in effect by Rep. of Turkey Ministry of Science, Industry and Technology in 2015. The complexity of matters, such as local industry participation, investment and technological cooperation categories in ICP, are able to be understandable with the help of the case studies and TM principles in the field of railway sector. In this study, firstly; the economic, the technical, the operational criterias, the non-price factors for the contracts and the other determinants on the basis of the case studies were reasonably suggested with the aim of the identification, usage, selection of the technologies and boosting the cooperation among the stakeholders in the growing demand for the rail vehicles in Turkey. Secondly, in the process of the large rail vehicle procurements as TM activities, with the purpose of the identification, the selection, the acquisition, the exploitation, the protection, the learning of the rail vehicle technologies and carrying out ICP contract processes in an effective and an efficient manner; a reference TM model established as a flow diagram was developed in this study for the authorities.
Design Of Reliable Communication Networks: A Hybrid Ant Colony Optimization Algorithm
(2010) Dengiz, Berna; Altiparmak, Fulya; Belgin, Onder; 0000-0003-1730-4214; 0000-0001-6702-2608; AAF-7020-2021; K-1080-2019
This article proposes a hybrid approach based on Ant Colony Optimization (ACO) and Simulated Annealing (SA), called ACO_SA, for the design of communication networks. The design problem is to find the optimal network topology for which the total cost is a minimum and the all-terminal reliability is not less than a given level of reliability. The proposed ACO_SA has the advantages of the ability to find higher performance solutions, created by the ACO, and the ability to jump out of local minima to find better solutions, created by the SA. The effectiveness of ACO_SA is investigated by comparing its results with those obtained by individual application of SA and ACO, which are basic forms of ACO_SA, two different genetic algorithms and a probabilistic solution discovery algorithm given in the literature for the design problem. Computational results show that ACO_SA has a better performance than its basic forms and the investigated heuristic approaches.
Development of A Decision Support System for Robot Selection
(2013) Ic, Yusuf Tansel; Yurdakul, Mustafa; Dengiz, Berna; 0000-0001-9274-7467; 0000-0002-1562-5738; AGE-3003-2022; AAA-6966-2021
With the availability of more different robot types and models along with their separate specifications, selecting the most appropriate robot is becoming more difficult and complicated for companies. Furthermore, a common set of robot selection criteria is not available for the decision makers. In this study, a two-phase robot selection decision support system, namely ROBSEL, is developed to help the decision makers in their robot selection decisions. In development of ROBSEL, an independent set of criteria is obtained first and arranged in the Fuzzy Analytical Hierarchy Process (FAHP) decision hierarchy. In the first elimination phase of the decision support system, the user obtains the feasible set of robots by providing limited values for the 15 requirements. ROBSEL, then, uses FAHP decision hierarchy to rank the feasible robots in the second phase. ROBSEL is illustrated and tested and several critical issues in its practical usage are explored in the paper. The applications of ROBSEL show that ROBSEL is a useful, practical and easy to use robot selection tool and improves robot selection decisions in the companies. (C) 2012 Elsevier Ltd. All rights reserved.
Development of a Decision Support System for Selection of Reviewers to Evaluate Research and Development Projects
(2023) Kocak, Serdar; Ic, Yusuf Tansel; Sert, Mustafa; Atalay, Kumru Didem; Dengiz, Berna
The evaluation of Research and Development (R&D) projects consists of many steps depending on the government funding agencies and the support program. It is observed that the reviewer evaluation reports have a crucial impact on the support decisions of the projects. In this study, a decision support system (DSS), namely R&D Reviewer, is developed to help the decision-makers with the assignment of the appropriate reviewer to R&D project proposals. It is aimed to create an artificial intelligence-based decision support system that enables the classification of Turkish R&D projects with natural language processing (NLP) methods. Furthermore, we examine the reviewer ranking process by using fuzzy multi-criteria decision-making methods. The data in the database is processed primarily to classify the R&D projects and the word embedding model NLP, "Word2Vec". Also, we designed the Convolutional Neural Network (CNN) model to select the features by using the automatic feature learning approach. Moreover, we incorporate a new integrated hesitant fuzzy VIKOR and TOPSIS methodology into the developed DSS for the reviewer ranking process.
The development of a reviewer selection method: a multi-level hesitant fuzzy VIKOR and TOPSIS approaches
(2021) Kocak, Serdar; Ic, Yusuf Tansel; Atalay, Kumru Didem; Sert, Mustafa; Dengiz, Berna; 0000-0001-9274-7467; AGE-3003-2022
This paper proposes a new approach for the selection of reviewers to evaluate research and development (R&D) projects using a new integrated hesitant fuzzy VIKOR and TOPSIS methodology. A reviewer selection model must have a multi-level framework in which reviewer selection strategies and related objectives guide the second level of the reviewer performance ranking process. The model must measure reviewer performance related to the activities that are necessary for the R&D project evaluation to be successful. A novel model is presented in this paper. In the proposed methodology, the aim is to select a reviewer in a hierarchical decision-making structure. The selection criteria values and their weights were obtained using the hesitant fuzzy VIKOR method. For the selection of a suitable reviewer, the conventional TOPSIS model was used. We developed a simpler procedure for effectively performing the reviewer selection process. The new approach was tested with a real case study and satisfactory results were obtained. A comparative analysis is also included in the article for illustrative purposes.
Driver Performance Appraisal Using GPS Terminal Measurements: A Conceptual Framework
(2013) Simsek, Baris; Pakdil, Fatma; Dengiz, Berna; Testik, Murat Caner; 0000-0003-2389-4759; AAE-3672-2019; G-6133-2013
Objective measurement for performance appraisal is vital but rarely conducted in a methodologically sound manner. In this paper, we provide a thorough assessment of how objective and fair performance appraisals of drivers can be conducted. Furthermore, a unique conceptual framework is provided for evaluation of safety interventions and operational performance through monitoring quantitative driver performance measures. The conceptual framework makes use of online-measurements obtained from Global Positioning System (GPS) terminals, and the data are evaluated using statistical process control (SPC) tools. SPC tools are useful in comparing individual driver performance to overall performance as well as for identifying time-dependent factors that influence performance. Quantitative performance measures considered in the study include speed violations, vehicle idle duration, and fuel consumption. As an illustration of the concepts and implementation at a logistics firm is provided. (C) 2012 Elsevier Ltd. All rights reserved.