Mühendislik Fakültesi / Faculty of Engineering

Permanent URI for this collectionhttps://hdl.handle.net/11727/1401

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    Development of A Financial Performance Benchmarking Model for Corporate Firms
    (2015) Ic, Yusuf Tansel; Tekin, Muhtesem; Pamukoglu, Fazil Ziya; Yildirim, S. Erdinc; 0000-0001-9274-7467; AGE-3003-2022; AGQ-5008-2022; AAI-1081-2020
    In this study, we developed a financial performance evaluation model to rank the corporate firms of 24 sectors in the Turkish economy. The developed model is based on the financial ratiosand Technique for Order Preference by Similiarity to Ideal Solution (TOPSIS) approach. This model of ferscorporate firm's rating scores with respect to its competitors belonging to the same industry. The developed model is coded in Visual Basic and tested with real case studies. Financial performance evaluation rankings obtained from TOPSIS, Vise Kriterijumska Optimizacija I Kompromisno Resenje (VIKOR), Grey Relational Grade (GRA), and Multi-Objective Optimization on thebasis of Ratio Analysis (MOORA) methods were compared by using Spearman's rank correlation test. Based on the test results, it was found that the TOPSIS method is the most appropriate method for the evaluation of financial performance. An application is also provided in the paper for illustrative purposes.
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    Time Harmonic Analysis in Electric Power Systems
    (2015) Germec, Kadir Egemen; Erdem, Hamit
    In this study, for time-varying signals in electric power systems, a multi functional system structure involving fundamental frequency detection, phase angle and amplitude estimation of harmonic and interharmonic components have been developed. Due to its simple and open structure, this system provides knowledge of harmonic component values as well as information about at which intervals and to what extend these component values are effective, which is possible with interventions that improve performance. The results of the experimental studies performed by using MATLAB simulation environment show that, this system is convenient and effective for the harmonic analysis of the current and voltage waveforms. Therewith, the individual effects of this time-variant harmonic and interharmonic components could be instantly detected in 3D time-harmonic space.
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    Heterogeneous Vehicle Routing Problem with Simultaneous Pickup and Delivery: Mathematical Formulations and A Heuristic Algorithm
    (2015) Kececi, Baris; Altiparmak, Fulya; Kara, Imdat; 0000-0002-2730-5993; AAF-7020-2021; AAC-4793-2019; ABH-1078-2021; F-1639-2011
    One of the most important operational decisions in the logistics management is to determine the vehicle routes serving the customers. The Vehicle Routing Problem (VRP) can be defined as the determination of the optimal routes which meet the delivery (or pickup) demands from the depot to the customers. In the real life applications of logistics, vehicles in a fleet may differ from each other. In addition, the requirements arising from customers/goods may reveal the necessity to use different vehicles. Besides, companies do care more about the management of reverse flow of products, semi-finished and raw materials because of their economic benefits and as well as legal and environmental liabilities. In this paper, a variant of the VRP is considered with heterogeneous fleet of vehicles and simultaneous pickup and delivery. This problem is referred to Heterogeneous Vehicle Routing Problem with Simultaneous Pickup and Delivery (HVRPSPD). The HVRPSPD can be defined as determining the routes and the vehicle types on each route while minimizing the total cost. In this paper, a polynomial sized flow-based mathematical model is proposed for the HVRPSPD. Since the HVRPSPD is in the class of NP-hard problems, it is difficult to find the optimal solution in a reasonable time even for the moderate size problems. Therefore, a simple and constructive heuristic algorithm is proposed to solve the medium and large scale HVRPSPD s. This algorithm is the adaptation of very well-known Clarke-Wright Savings approach, which has originally developed for the VRP, to the HVRPSPD. The performances of the proposed mathematical model and the heuristic algorithm have been examined on the test problems.
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    Working Posture Analysis in Fuzzy Environment and Ergonomic Work Station Design Recommendations
    (2015) Can, Gulin Feryal; Atalay, Kumru Didem; Eraslan, Ergun; 0000-0002-5667-0391; AAE-7165-2019
    Realization of ergonomic design applications in working environments, makes it possible to preserve the health of employees, provide them working comfort and increase productivity. Therefore ergonomic work station design has an outstanding position in work places. In this study, an investigation was made on work stations in a metal accessor producer, which were found to be inappropriate from point of view of design considerations as a result of an ergonomic condition analysis. Inappropriate designs force workers to repetitively assume dangerous postures. As a result production process slows down and workers experience a feeling of increasing tiredness. Postures of workers were analyzed by The Fuzzy Rapid Entire Body Assessment (BREBA) developed by inserting triangular fuzzy scale to Rapid Entire Body Assessment (REBA). The BREBA method determines the level of risk in whole body caused by postures while prevents potential information loss and allows obtaining more accurate results in a fuzzy environment. In the said working place, 688 posture photographs belonging to four work stations (heat treatment, primary press, secondary press and transportation station) were examined. The consequent assessment suggested that; leg, upper arm and wrist in heat treatment, leg, wrist and torso in pres station, torso and arm were found to be the most enforced body sections. The results pointed out that 52,03% of postures displayed in production process introduced medium level risk and improvements were suggested.
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    Analysis of Deep Neural Network Models for Acoustic Scene Classification
    (2019) Basbug, Ahmet Melih; Sert, Mustafa
    Acoustic Scene Classification is one of the active fields of both audio signal processing and machine learning communities. Due to the uncontrolled environment characteristics and the multiple diversity of environmental sounds, the classification of acoustic environment recordings by computer systems is a challenging task. In this study, the performance of deep learning algorithms on acoustic scene classification problem which includes continuous information in sound events are analyzed. For this purpose, the success of the AlexNet and the VGGish based 4- and 8-layered convolutional neural networks utilizing long-short-term memory recurrent neural network (LSTM-RNN) and Gated Recurrent Unit Recurrent Neural Network (GRU-RNN) architectures have been analyzed for this classification task. In this direction, we adapt the LSTM-RNN and the GRU-RNN models with the 4- and 8-layared CNN architectures for the classification. Our experimental results show that 4-layered CNN with GRU structure improve the accuracy.
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    Classification of Obstructive Sleep Apnea using Multimodal and Sigma-based Feature Representation
    (2019) Memis, Gokhan; Sert, Mustafa
    Obstructive sleep apnea (OSA) is a sleep disorder characterized by a decrease in blood oxygen saturation and waking up after a long time. Diagnosis can be made by following a full night with a polysomnogram device, so there is a need for computer-based methods for the diagnosis of OSA. In this study, a method based on feature selection is proposed for OSA classification using oxygen saturation and electrocardiogram signals. Standard deviation (sigma) based features have been created to increase accuracy and reduce computational complexity. To evaluate the effectiveness, comparisons were made with selected machine learning algorithms. The achievements of the obtained features were compared with Naive Bayes (NB), k-nearest neighborhood (kNN) and Support Vector Machine (SVM) classifiers. The tests performed on the PhysioNet dataset consisting of real clinical samples show that the use of sigma-based features result an average performance increase of 1.98% in all test scenarios.
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    Improvement of the Surface Quality in the Honing Process Using Taguchi Method
    (2016) Yurdakul, Mustafa; Gunes, Serkan; Ic, Yusuf Tansel; 0000-0001-9274-7467; 0000-0002-1562-5738; AGQ-5008-2022; AAA-6966-2021
    Steel cylinders are critical components of hydraulic systems and they are available in various diameters and thicknesses. Defects and discontinuities that remain on the inner body surfaces of the cylinders after turning operation can harm components that move inside the cylinders such as pistons and piston seals. Honing operation is commonly performed after turning operation as a finishing operation to improve inner surface quality of cylinders. Honing operation reduces surface roughness values to acceptable levels. The most critical parameters that are important in the honing operation are honing tool head forward speed, rotational speed of the tool and honing stone grain size. Optimizing these parameters will increase honing operation productivity and provide the best surface roughness values. This study aims to obtain the values of the most critical parameters that provide the best surface quality in the honing operation using Taguchi method.
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    Development of a Computer Application for Multi-Response Taguchi Optimization
    (2016) Ic, Yusuf Tansel; Duran, Hikmet; Kececi, Baris; Ilik, Emrecan; Bilgic, Berkan; 0000-0001-9274-7467; 0000-0002-2730-5993; AGE-3003-2022; F-1639-2011; AAI-1081-2020; AAC-4793-2019; AGQ-5008-2022
    In this study, a computer application has been developed for the parameter optimization problem having maximum three quality characteristics and three parameters having three levels for each parameter. When the quality characteristics and the level of the parameters affecting the problem are obtained, appropriate Taguchi array in accordance with an appropriate experimental design is determined by using the developed application. After the collection of the experimental results for the quality characteristics, multi-response optimization problem is converted to single response problem by using the TOPSIS method. In the developed application any parameter design problems having single, two or three quality characteristic can be optimized.
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    Evaluation of performance levels of students for moodle learning management system in terms of usability Criteria with PSI-Entropy-Marcos integration
    (2022) Yorulmaz, Muhammet; Can, Gulin Feryal
    The study, it is aimed to determine and compare the end-user performances within the scope of achieving the determined objectives while using the Moodle Learning Management System (LMS). Accordingly, considering multiple usability criteria, 18 users were prioritized in terms of their performances in using Moodie LMS. In this direction, Preference Selection Index (PSI) and Entropy integration was used to determine the importance weights of usability criteria, and the Measurement of Alternatives and Ranking according to Compromise Solution (MARCOS) method was used to prioritize the end-users. A new hybrid weighting method has been proposed by integrating the PSI method with the Entropy method, taking into account both the uncertainty in the performance values of the end-users according to the criteria and the preference change values of the criteria. This proposed method is applied for a three-dimensional initial decision matrix Thus, the traditional two-dimensional initial decision matrix which consists of the alternatives and the values that the alternatives take according to the criteria, has been developed and made more flexible. The objective criteria taken into account in the analysis were measured by the Morae V3 program, with the tasks defined as predetermined goals being performed by the users on the Moodie LMS. In addition, the criteria weights obtained from the proposed PSI-Entropy integration were used in the MARCOS method to rank the end-users according to their performance levels.
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    A goal programming approach for multi objective, multi-trips and time window routing problem in home health care service
    (2021) Dengiz, Asiye Ozge; Atalay, Kumru Didem; Altiparmak, Fulya
    The structure of services in the health sector is changed by the epidemic diseases affecting the world, the population growth and developing technologies. Due to the advantages it provides, home health care (HHC) services are increasingly being demanded by patients. With the in-crease in demand for HHC, the interest of researchers in Home Health Care Routing Problem (HHCRP) is also increasing. In this study, HHCRP has been studied based on information gathered from a relevant unit of a State Hospital providing HHC services in Ankara. Due to the limited resources in the hospital under consideration, vehicles often need to be used for multiple rounds. Thus, the HHCRP is considered as a multi-tour routing problem. Besides, the problem has been created with time window constraints in order to ensure that the demands of the patients are met on time. Meantime, meeting all the patient demands and reducing the environmental impacts are two important goals in HHCRP. The reduction of the environmental impacts can be achieved by minimizing the carbon emission of the vehicles used in the HHC. Thus, the problem addressed in this study has been defined as a multi-objective, multi-trip and time-windows home healthcare routing problem (MTTW-HHCRP). Weighted goal programming (GP) method is used to solve the proposed problem. Test problems are randomly generated based on the data and the information obtained from the hospital in Ankara, and the solutions obtained through scenario analysis are evaluated to guide the decision-making process.