Most of today's optimization efforts aim to reduce costs, time or the number of resources used. However, optimization efforts should consider other factors as important as these, such as facilitating the lives of the disabled, elderly and... more
Most of today's optimization efforts aim to reduce costs, time or the number of resources used. However, optimization efforts should consider other factors as important as these, such as facilitating the lives of the disabled, elderly and pregnant and helping them in their daily lives. In this study, the Nuh Naci Yazgan (NNY) University (Kayseri/Turkey) personnel transport problems were discussed. The NNY University provides a shuttle service to bring employees to school at the start of the work and to leave them at home after work. In order to shorten the collection / distribution time and the total distance travelled, the service vehicle does not leave / pick up all employees in front of their homes. Instead, the employees are picked up / dropped at appropriate locations on an intuitively determined route. Since only the time and cost savings are taken into account when determining the service route, some employees have a long walking distance to the service route. This creates a very important problem, especially for the disabled and pregnant workers. In this study, a new mathematical model is proposed which takes into consideration the physical disadvantages and occupational positions of the employees in order to determine the shortest vehicle route. The results show that the proposed model can significantly reduce walking distances of physically disabled people without compromising the total distance travelled by the vehicle.
Research Interests:
Bed production has an important market in the furniture sector. In spite of the fact that sponge is generally preferred as filler in the production process of beds, increasing prices in recent years and the preference of new materials... more
Bed production has an important market in the furniture sector. In spite of the fact that sponge is generally preferred as filler in the production process of beds, increasing prices in recent years and the preference of new materials with the development of alternative filling materials have increased. Recently it is seen other than sponge, the granule, wadding, and STW are also used as filling material in bed production. From the management point of view, the choice of filler is an important decision problem that depends on the situation of the business and many objective and subjective criteria must be taken into consideration. It is appropriate to examine such a problem with the Analytical Hierarchy Method (AHP) and the ELECTRE method, which have the ability to make quantitative evaluations and synthesize factor weights from subjective judgments. The criteria for selection of the filler material and the extent to which the criterion will affect the evaluation are important decision points. The opinions of experts in bed production were consulted to determine the criteria to be used in the evaluation. The obtained results show that four basic criteria must be taken into consideration in the selection of filler material. In this study, AHP was used for determining the criteria weights, and ELECTRE methods were used for the selection of the best filling material. The results showed that wadding is the optimum filler material for bed production.
Research Interests:
Grey theory is one of the methods used to study uncertainty. The uncertain systems characterized by small sample and poor information are the study object of grey system theory. Multivariable grey prediction models are part of grey... more
Grey theory is one of the methods used to study uncertainty. The uncertain systems characterized by small sample and poor information are the study object of grey system theory. Multivariable grey prediction models are part of grey forecasting system. They are presented if there are mutual relations among the factors in the system. They believe that all the influencing factors are not independent of each other and should be regarded as a whole. In multivariable grey forecasting models, the future value of a variable is tried to be forecasted considering the other influential factors in the system. In this study, deformation consisting on the crest of a Dam is aimed to determine by using multivariable grey prediction models. Özet Gri teori, belirsizliği incelemek için kullanılan yöntemlerden biridir. Sınırlı bilgi ve küçük örnekler ile karakterize edilmiş belirsiz sistemler, gri sistem teorisinin inceleme konusudur. Çok değişkenli gri tahmin modelleri gri tahmin sisteminin parçasıdır. Sistemdeki faktörler arasında karşılıklı ilişkiler varsa onlar temsil edilirler. Etkileyen faktörler birbirinden bağımsız değildir ve bir bütün olarak kabul edilmektedir. Çok değişkenli gri tahmin modeli, bir değişkenin gelecek değerini sistemdeki diğer etkilenen faktörleri göz önüne alarak tahmin etmeye çalışmaktadır. Bu çalışmada, çok değişkenli gri tahmin modeli kullanarak bir barajın kreti üzerinde oluşan deformasyonların tahmin edilmesi amaçlanmıştır.
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Purpose-The purpose of this paper is to examine the effectiveness of the multivariable grey prediction model in deformation forecasting. Design/methodology/approach-Deformation in a dam can be seen because of many factors but without any... more
Purpose-The purpose of this paper is to examine the effectiveness of the multivariable grey prediction model in deformation forecasting. Design/methodology/approach-Deformation in a dam can be seen because of many factors but without any doubt, the most influential factor is the water level. In this study, the deformation level of a point in the Keban Dam crest has been tried to be forecasted depending on the water level by the multivariable grey model GM(1,N). Regression analysis was used to test the accuracy of the prediction results obtained using the grey prediction model. Findings-The results show that there is a great consistency between the grey prediction values and the actual values, and that the GM(1,N) produces more reliable results than the regression analysis. Based on the results, it can be concluded that the GM(1,N) is a very reliable estimation model for limited data conditions. Originality/value-Different from the other studies in the literature, this study investigates deformation in a dam subject to the water level in the dam reservoir. The main contribution of the study to the literature is to suggest a relatively new procedure for estimating the deformation in the dams based on the water level.
Purpose-The purpose of this paper is to present a mixed integer programming model for simple assembly line balancing problems (SALBP) with Type 1 when the annual demand and task durations are uncertain and encoded with grey numbers.... more
Purpose-The purpose of this paper is to present a mixed integer programming model for simple assembly line balancing problems (SALBP) with Type 1 when the annual demand and task durations are uncertain and encoded with grey numbers. Design/methodology/approach-Grey theory and grey numbers are used for illustrating the uncertainty of parameters in an SALBP, where the objective is to minimize the total number of workstations. The paper proposes a 0-1 mathematical model for SALBP of Type 1 with grey demand and grey task durations. Findings-The uncertainty of the demand and task durations are encoded with grey numbers and a well-known 0-1 mathematical model for SALBP of Type 1 is modified to find the minimum number of workstations in order to meet both the lower and upper bounds of the uncertain demand. The results obtained from the proposed mathematical model show a task-workstation assignment that does not distribute precedence relations among tasks and workstations and the sum of task durations in each single workstation is less than or equal to the grey cycle time. Originality/value-The grey theory and grey numbers have not been previously used to identify uncertainties in assembly line balancing problems. Therefore, this study provides an important contribution to the literature.
Project scheduling has been still one of the hottest topics in the management area. The goal of traditional project management is to complete the project at the earliest possible time in accordance with the available resources without... more
Project scheduling has been still one of the hottest topics in the management area. The goal of traditional project management is to complete the project at the earliest possible time in accordance with the available resources without violating priority relations of the activities involved. Unlike traditional project management, this study deals with the possibility of a coalition among the staff available to accomplish tasks of the project. The tasks can be fulfilled by more than one staff members. Staff’s coalition shortens the completion time of the tasks. A natural problem that arises in this case is how to share the income generated. The other side of the problem is concerned with the project owner who wants the project to be completed as early as possible. In this study, a mathematical model proposal is dealt with in order to real-ize the goals of both the project owner and the staffs as much as possible within the complex structure of the situation.
Research Interests:
Motivated by the increasing civilian use of Unmanned Aerial Vehicles (UAVs), this paper considers the simultaneous location and routing of UAVs for multiple missions and different weather conditions. We include modeling and computational... more
Motivated by the increasing civilian use of Unmanned Aerial Vehicles (UAVs), this paper considers the simultaneous location and routing of UAVs for multiple missions and different weather conditions. We include modeling and computational experience inspired by requirements for air surveillance by the Turkish government’s public agencies. We model these demands in multiple mission areas and consider the impact of different weather conditions on the ability to employ UAVs from different geographic locations. We formulate the problem as a two-stage stochastic integer linear program with recourse and get an optimal solution for realistic test instances in a reasonable amount of time using decomposition by weather and mission combinations. We also introduce an optimization-based heuristic with bounds based on our decomposition for larger test instances.
Research Interests:
Hubs are special facilities that serve as switching, transshipment and sorting points in many-to-many distribution systems. In hub location problems, transfers between origin-destination points do not take place directly between each... more
Hubs are special facilities that serve as switching, transshipment and sorting points in many-to-many distribution
systems. In hub location problems, transfers between origin-destination points do not take place directly between
each other, but by means of hubs for the purpose of taking advantages of economies of scale. Thus, it becomes
possible to provide connections to more points with less lines and costs. In this study, a real hub location
problem is studied for a public institution. On the basis of the institutions’ demands and the problems’
requirements, a new dimension has been provided to the capacitated multiple allocation hub location problems
which have significance in the literature. Unlike the studies conducted in the literature, obligation to use hubs
among the origin-destination pairs that are unselected hub is relaxed and the capacities of nodes that are selected
as hubs are provided to be affected by the flows both from the hubs and the spokes.
systems. In hub location problems, transfers between origin-destination points do not take place directly between
each other, but by means of hubs for the purpose of taking advantages of economies of scale. Thus, it becomes
possible to provide connections to more points with less lines and costs. In this study, a real hub location
problem is studied for a public institution. On the basis of the institutions’ demands and the problems’
requirements, a new dimension has been provided to the capacitated multiple allocation hub location problems
which have significance in the literature. Unlike the studies conducted in the literature, obligation to use hubs
among the origin-destination pairs that are unselected hub is relaxed and the capacities of nodes that are selected
as hubs are provided to be affected by the flows both from the hubs and the spokes.
Research Interests:
Bu çalışmada bir kamu kurumuna personel yetiştirmekle sorumlu olan ve dört yıllık eğitim hizmeti sağlayan bir okuldaki eğitim durumu incelenmiştir. Kamu kurumunun ihtiyaç duyduğu insan gücünün tamamı bu okuldan mezun olmaktadır. Bu... more
Bu çalışmada bir kamu kurumuna personel yetiştirmekle sorumlu olan ve dört yıllık eğitim hizmeti sağlayan bir okuldaki eğitim durumu incelenmiştir. Kamu kurumunun ihtiyaç duyduğu insan gücünün tamamı bu okuldan mezun olmaktadır. Bu çalışmanın başta okula alınacak öğrenci miktarlarının belirlenmesi olmak üzere çeşitli insan gücü planlama faaliyetlerinde sıhhatli veriler sağlayacağı değerlendirilmektedir. Çalışmada kamu kurumunun yetişmiş personel sıkıntısı yaşamaması için geleceğe yönelik olarak projeksiyonlar ortaya koyulmuştur. Çalışmada yöntem olarak yöneylem araştırması tekniklerinden Markov Analizi kullanılmıştır. Çalışmanın katkısı kamu kurumu için hayati öneme sahip gerçek bir probleme Markoz Analizi gibi bilimsel bir teknik yardımıyla çözüm önerilmesidir.
Research Interests:
Dams are important engineering structures, therefore dams should be constructed with the rigors of safety in mind. In this paper, the vertical displacement of the crest of Keban Dam in Turkey, is determined using a grey prediction method.... more
Dams are important engineering structures, therefore dams should be
constructed with the rigors of safety in mind. In this paper, the vertical
displacement of the crest of Keban Dam in Turkey, is determined using a grey
prediction method. The grey prediction method is a method that produces
satisfactory results when we do not have enough experience about a system
behaviors. The purpose of this study is to examine the effectiveness of the grey
prediction method in systems where a limited amount of data is available or known.
In this study the Simple Exponential Smoothing (SES) method; a very well-known
prediction method is used for comparison. The results from our investigation
indicate that the grey prediction method produces better results, more in-keeping
with true values.
constructed with the rigors of safety in mind. In this paper, the vertical
displacement of the crest of Keban Dam in Turkey, is determined using a grey
prediction method. The grey prediction method is a method that produces
satisfactory results when we do not have enough experience about a system
behaviors. The purpose of this study is to examine the effectiveness of the grey
prediction method in systems where a limited amount of data is available or known.
In this study the Simple Exponential Smoothing (SES) method; a very well-known
prediction method is used for comparison. The results from our investigation
indicate that the grey prediction method produces better results, more in-keeping
with true values.
Research Interests: Geodesy, Building Surveying, GPS Applications, Deformation and strain, Surveying, and 9 moreGPS, Land Surveying, GPS and civil engineering, Deformation, Crustal Deformation studies using GPS, GNSS and GPS, Grey relational analysis, Geodesy and Global Positioning System (GPS) and Their Applications In Earth Sciences, and Geodetic Deformation Analysis
Research Interests:
Research Interests:
Research Interests:
Research Interests: Engineering, Chemical Engineering, Chemistry, Reference, Systems Engineering, and 21 moreEnergy Efficiency Buildings, Fuzzy Sets, Multi Criteria Decision Making, Fuzzy, Analytic Network Process, Planning, Project evaluation, Mathematical Sciences, Multicriteria decision making, Goal programming, Indian, Material, Task Performance, Planeación, Delphi method, Assignment Problem, Aeropuertos, Fuzzy Goal Programming, Decision Maker, Database, and Heuristic algorithm
Turk Silahli Kuvvetleri (TSK) personeli uzun yillar calisma hayati sonrasinda emeklilige hazirlanirken daha once karsilasmadigi “Nerede yasayacagim? Yasayacagim sehri secerken nelere dikkat etmeliyim?” sorulari ile karsilasmaktadir. Bu... more
Turk Silahli Kuvvetleri (TSK) personeli uzun yillar calisma hayati sonrasinda emeklilige hazirlanirken daha once karsilasmadigi “Nerede yasayacagim? Yasayacagim sehri secerken nelere dikkat etmeliyim?” sorulari ile karsilasmaktadir. Bu calismanin amaci, benzer sorulara cevap arayan TSK personeline, objektif yasam kosullari ve personel tercihlerinin bileskesinden elde edilen bir bolge/sehir secim sistemi gelistirmektir. Bu calismanin TSK emeklisi personelin hayatinin geri kalan bolumunu buyuk olcude etkileyecek olan karmasik bir problemin cozumunde yardimci olacagi degerlendirilmektedir. Ayrica TSK emeklisi personeline yonelik olarak cesitli yatirimlar yapmayi planlayan kuruluslar icin de bu yatirimlari nerelerde yogunlastirmalari gerektigi hususunda onemli bilgiler sunacagi dusunulmektedir.
The success of businesses today is largely dependent on their ability to find solutions to complex problems they encounter. Vehicle selection, which requires considering many objective and subjective criteria, is at the top of these... more
The success of businesses today is largely dependent on their ability to find solutions to complex problems they encounter. Vehicle selection, which requires considering many objective and subjective criteria, is at the top of these problems. The tramway selection problem of a company operating in the public transport sector in Turkey is discussed in this study. The company wants to increase passenger carrying capacity and renew its vehicle fleet. For this purpose, it has to choose from eight alternative vehicles with different superior features. Considering the high costs that may arise from wrong selection, it becomes clear how important it is to use the right method to solve the problem. In this study, the evaluation criteria were determined by taking the opinions of experts first. Then, weights were assigned to the criteria using the Analytical Hierarchy Process (AHP). In the last stage, the best alternative has been tried to be determined by using grey relationship analysis (GRA). It is common to use more than one method to test the reliability of the results in solving multi-criteria decision-making (MCDM) problems. In this study, multi-objective optimization, based on ratio analysis (MOORA), which is one of the most preferred methods to solve MCDM problems, was used to test the accuracy of the results. Although various MCDM methods are used in the literature to solve similar problems, the use of grey relationship analysis has not been encountered. With this aspect, this study has expanded the application of grey theory and made an important contribution to the literature. Another important contribution of the study is that the evaluation criteria for the tramway selection problem have been determined with the help of experts. Finally, this study presents a scientific approach to the solution of a complex real-life problem.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Gunumuz rekabet sartlarinda isletmeleri hedeflerine ulastiracak olan; kurumsallasma faaliyetlerinin gelistirilmesi, yurtici ve yurt disi pazarlarin artirilmasi, taninirlik faaliyetlerinin sistematik olarak yurutulmesi, is sureclerinin... more
Gunumuz rekabet sartlarinda isletmeleri hedeflerine ulastiracak olan; kurumsallasma faaliyetlerinin gelistirilmesi, yurtici ve yurt disi pazarlarin artirilmasi, taninirlik faaliyetlerinin sistematik olarak yurutulmesi, is sureclerinin etkin ve verimli yonetilmesine yonelik gerekli iyilestirme ve gelistirme sureclerinin islerligi gibi tum calisma alanlarinin asil ve dinamik yapisini olusturan ana etken, insan faktorudur. Bu nedenle, isletmelerde personel secimi oldukca onemlidir. Personel secim surecinin basarili sekilde tamamlanmasi, isletmenin verimliligini olumlu yonde etkilerken; yanlis secimler uretim asamasini, kaynaklarin kullanilabilirligini olumsuz yonde etkileyerek musteri ve pazar kayiplarina sebep olacaktir. Personel secimine onem verilmediginde, hem isletme zarara ugrayacak hem de personelin motivasyonu olumsuz etkilenecektir. Personel seciminde nitel degerlendirmelerin yani sira nicel degerlendirmelerin de yapilmasi, isletmeler acisindan hayati oneme sahip olan bu surec...
Research Interests:
Research Interests:
Bu calismada bir kamu kurumuna personel yetistirmekle sorumlu olan ve dort yillik egitim hizmeti saglayan bir okuldaki egitim durumu incelenmistir. Kamu kurumunun ihtiyac duydugu insan gucunun tamami bu okuldan mezun olmaktadir. Bu... more
Bu calismada bir kamu kurumuna personel yetistirmekle sorumlu olan ve dort yillik egitim hizmeti saglayan bir okuldaki egitim durumu incelenmistir. Kamu kurumunun ihtiyac duydugu insan gucunun tamami bu okuldan mezun olmaktadir. Bu calismanin basta okula alinacak ogrenci miktarlarinin belirlenmesi olmak uzere cesitli insan gucu planlama faaliyetlerinde sihhatli veriler saglayacagi degerlendirilmektedir. Calismada kamu kurumunun yetismis personel sikintisi yasamamasi icin gelecege yonelik olarak projeksiyonlar ortaya koyulmustur. Calismada yontem olarak yoneylem arastirmasi tekniklerinden Markov Analizi kullanilmistir. Calismanin katkisi kamu kurumu icin hayati oneme sahip gercek bir probleme Markoz Analizi gibi bilimsel bir teknik yardimiyla cozum onerilmesidir.
Research Interests:
Private Pension System (PPS) has an important place in developed societies. Legal regulations which have been carried out recently made PPS desirable for investors also in our country. Correspondingly the number of PPS companies which... more
Private Pension System (PPS) has an important place in developed societies. Legal regulations which have been carried out recently made PPS desirable for investors also in our country. Correspondingly the number of PPS companies which operate in our country has increased visibly. For investors selecting the best alternative among plenty of PPS companies is an important decision problem
Research Interests:
The existing literature documents that computer simulations can reveal how characteristics of micro-level individuals give rise to macro-level phenomena of systemic wholes. This paper seeks to establish such an important simulation-based... more
The existing literature documents that computer simulations can reveal how characteristics of micro-level individuals give rise to macro-level phenomena of systemic wholes. This paper seeks to establish such an important simulation-based observation as a theoretical result on a sound foundation. Going beyond addressing when holistic phenomena can naturally emerge from micro-level characteristics, this paper investigates how and why many macro-level entities appear to answer market calls through organically gathering micro-level agents into uniformly-oriented operational wholes, even though these agents have inconsistent or even conflicting interests. This paper develops conclusions based on results of systems science and establishes a sufficient condition under which characteristics of micro-level agents can naturally lead to the appearance of macro-level properties of a systemic whole even though the former are heterogeneous and behave in an unintended and uncoordinated manner. Thi...
Research Interests:
Research Interests:
Research Interests: Computer Science, Heuristics, Linear Programming, Multidisciplinary, Modelling and simulation, and 12 moreLocation Allocation, European, Branch and Bound, Location, Upper Bound, Shortest Path, Information Systems Development And Management, Location Problem, LINEAR PROGRAM, Nova, Disaster Recovery Using Operations Research and Management Science, and Heuristic algorithm
Bed production has an important market in the furniture sector. In spite of the fact that sponge is generally preferred as filler in the production process of beds, increasing prices in recent years and the preference of new materials... more
Bed production has an important market in the furniture sector. In spite of the fact that sponge is generally preferred as filler in the production process of beds, increasing prices in recent years and the preference of new materials with the development of alternative filling materials have increased. Recently it is seen other than sponge, granule, wadding and STW are also used as filling material in bed production. From the management point of view, the choice of filler is an important decision problem that depends on the situation of the business and many objective and subjective criteria must be taken into consideration. It is appropriate to examine such a problem with the Analytical Hierarchy Method (AHP) and the ELECTRE method, which have the ability to make quantitative evaluations and synthesize factor weights from subjective judgments.The criteria for selection of the filler material and the extent to which the criterion will affect the evaluation are important decision po...
Research Interests:
Most of today's optimization efforts aim to reduce costs, time or the number of resources used. However, optimization efforts should consider other factors as important as these, such as facilitating the lives of the disabled, elderly... more
Most of today's optimization efforts aim to reduce costs, time or the number of resources used. However, optimization efforts should consider other factors as important as these, such as facilitating the lives of the disabled, elderly and pregnant and helping them in their daily lives. In this study, the Nuh Naci Yazgan (NNY) University (Kayseri/Turkey) personnel transport problems were discussed. The NNY University provides a shuttle service to bring employees to school at the start of the work and to leave them at home after work. In order to shorten the collection / distribution time and the total distance travelled, the service vehicle does not leave / pick up all employees in front of their homes. Instead, the employees are picked up / dropped at appropriate locations on an intuitively determined route. Since only the time and cost savings are taken into account when determining the service route, some employees have a long walking distance to the service route. This create...
Research Interests:
Purpose The purpose of this paper is to examine the effectiveness of the multivariable grey prediction model in deformation forecasting. Design/methodology/approach Deformation in a dam can be seen because of many factors but without any... more
Purpose The purpose of this paper is to examine the effectiveness of the multivariable grey prediction model in deformation forecasting. Design/methodology/approach Deformation in a dam can be seen because of many factors but without any doubt, the most influential factor is the water level. In this study, the deformation level of a point in the Keban Dam crest has been tried to be forecasted depending on the water level by the multivariable grey model GM(1,N). Regression analysis was used to test the accuracy of the prediction results obtained using the grey prediction model. Findings The results show that there is a great consistency between the grey prediction values and the actual values, and that the GM(1,N) produces more reliable results than the regression analysis. Based on the results, it can be concluded that the GM(1,N) is a very reliable estimation model for limited data conditions. Originality/value Different from the other studies in the literature, this study investig...
Motivated by the increasing civilian use of Unmanned Aerial Vehicles (UAVs), this paper considers the simultaneous location and routing of UAVs for multiple missions and different weather conditions. We include modeling and computational... more
Motivated by the increasing civilian use of Unmanned Aerial Vehicles (UAVs), this paper considers the simultaneous location and routing of UAVs for multiple missions and different weather conditions. We include modeling and computational experience inspired by requirements for air surveillance by the Turkish government’s public agencies. We model these demands in multiple mission areas and consider the impact of different weather conditions on the ability to employ UAVs from different geographic locations. We formulate the problem as a two-stage stochastic integer linear program with recourse and get an optimal solution for realistic test instances in a reasonable amount of time using decomposition by weather and mission combinations. We also introduce an optimization-based heuristic with bounds based on our decomposition for larger test instances.
Research Interests:
Research Interests:
Gelecege yonelik senaryolar nasil olusturulur? Gelecegin planlamasi nasil yapilir? Bu sorularin cevabinin verilebilmesi gelecege yonelik belirsizliklerin ortadan kaldirilmasi ile mumkun olacaktir. Senaryo planlama, gelecege yonelik... more
Gelecege yonelik senaryolar nasil olusturulur? Gelecegin planlamasi nasil yapilir? Bu sorularin cevabinin verilebilmesi gelecege yonelik belirsizliklerin ortadan kaldirilmasi ile mumkun olacaktir. Senaryo planlama, gelecege yonelik belirsizlikleri yonetmek ve stratejik planlama surecini verimli hale getirmek amaciyla kullanilan onemli bir yonetim ve sistem surecidir. Calismada, senaryo planlama sureci, ozellikleri ve teknikleri ile ilgili literatur arastirmasi, ornek bir uygulama ile degerlendirme bolumleri yer almaktadir
Dams are important engineering structures, therefore dams should be constructed with the rigors of safety in mind. In this paper, the vertical displacement of the crest of Keban Dam in Turkey, is determined using a grey prediction method.... more
Dams are important engineering structures, therefore dams should be constructed with the rigors of safety in mind. In this paper, the vertical displacement of the crest of Keban Dam in Turkey, is determined using a grey prediction method. The grey prediction method is a method that produces satisfactory results when we do not have enough experience about a system behaviors. The purpose of this study is to examine the effectiveness of the grey prediction method in systems where a limited amount of data is available or known. In this study the Simple Exponential Smoothing (SES) method; a very well-known prediction method is used for comparison. The results from our investigation indicate that the grey prediction method produces better results, more in-keeping with true values.
Research Interests:
Fakru zaruret icinde ve muhtac durumda bulunan vatandaslar ile gerektiginde her ne suretle olursa olsun Turkiye'ye kabul edilmis veya gelmis olan kisilere yardim etmek, sosyal adaleti pekistirici tedbirler alarak gelir dagiliminin... more
Fakru zaruret icinde ve muhtac durumda bulunan vatandaslar ile gerektiginde her ne suretle olursa olsun Turkiye'ye kabul edilmis veya gelmis olan kisilere yardim etmek, sosyal adaleti pekistirici tedbirler alarak gelir dagiliminin adilane bir sekilde tevzi edilmesini saglamak, sosyal yardimlasma ve dayanismayi tesvik etmek maksadiyla her il ve ilcede Sosyal Yardimlasma ve Dayanisma (SYD) vakiflari kurulmustur. SYD Vakiflarina gecmis yillarda yapilan basvurular incelendiginde vakiflarin sahip olduklari kaynaklarin ihtiyacin tamamini karsilamada yetersiz kaldigi gorulmektedir. Mevcut durumda basvuru sahipleri arasindan yardim yapilacak kisilerin secimi vakif mutevelli heyetinin subjektif degerlendirmelerine bagli olarak gerceklestirilmektedir. Oysa bu karar pek cok objektif ve subjektif kriterin birlikte degerlendirilmesini gerektiren onemli bir Cok Kriterli Karar Verme (CKKV) problemidir. Yardima muhtac kisilerin belirlenmesine yonelik olarak literaturde herhangi bir calismaya ra...
Research Interests:
Grey theory is one of the methods used to study uncertainty. The uncertain systems characterized by small sample and poor information are the study object of grey system theory. Multivariable grey prediction models are part of grey... more
Grey theory is one of the methods used to study uncertainty. The uncertain systems characterized by small sample and poor information are the study object of grey system theory. Multivariable grey prediction models are part of grey forecasting system. They are presented if there are mutual relations among the factors in the system. They believe that all the influencing factors are not independent of each other and should be regarded as a whole. In multivariable grey forecasting models, the future value of a variable is tried to be forecasted considering the other influential factors in the system. In this study, deformation consisting on the crest of a Dam is aimed to determine by using multivariable grey prediction models.
Research Interests:
PurposeThis study has two main objectives: (1) to expand the application areas of grey system theory and (2) to select the most livable city in Turkey.Design/methodology/approachChoosing the most livable city is a complex problem that... more
PurposeThis study has two main objectives: (1) to expand the application areas of grey system theory and (2) to select the most livable city in Turkey.Design/methodology/approachChoosing the most livable city is a complex problem that requires many criteria to be considered. It is important to select decision points according to which the criteria selection will be made and to what extent the criteria will affect the evaluation. For this purpose, a questionnaire was prepared to determine the criteria to be used in the assessment. The survey results were evaluated by the factor analysis (FA) and it was found that the criteria included in the survey were grouped under seven factors. Then, criteria weights were assigned to the determined criteria using the analytic hierarchy process (AHP). At the last stage, Turkey's six most popular cities are graded using the grey relational analysis (GRA) to reduce the uncertainty existing in the process of evaluation.FindingsThe obtained result...
The topic of this study is a real life facility location problem in the public sector. A public institution currently has 24 service facilities in a region. There are 55 candidate districts to open a facility in the region. A district... more
The topic of this study is a real life facility location problem in the public sector. A public institution currently has 24 service facilities in a region. There are 55 candidate districts to open a facility in the region. A district that has not a facility receives service from another facility in that region. General management desire to reduce the number of facilities because the existing system no longer provides a cost-effective service. However, opening of new facilities are also considered in case the current facilities fail to fulfil general management's demands. A mathematical programming model is introduced to determine where the facilities will be located, and which districts receives service from which facilities as if there are currently no existing facilities. The solution of the mathematical model shows implicitly which of the existing facilities should be closed and in which districts the new facilities should be opened.
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Gelecege yonelik senaryolar nasil olusturulur? Gelecegin planlamasi nasil yapilir? Bu sorularin cevabinin verilebilmesi gelecege yonelik belirsizliklerin ortadan kaldirilmasi ile mumkun olacaktir. Senaryo planlama, gelecege yonelik... more
Gelecege yonelik senaryolar nasil olusturulur? Gelecegin planlamasi nasil yapilir? Bu sorularin cevabinin verilebilmesi gelecege yonelik belirsizliklerin ortadan kaldirilmasi ile mumkun olacaktir. Senaryo planlama, gelecege yonelik belirsizlikleri yonetmek ve stratejik planlama surecini verimli hale getirmek amaciyla kullanilan onemli bir yonetim ve sistem surecidir. Calismada, senaryo planlama sureci, ozellikleri ve teknikleri ile ilgili literatur arastirmasi, ornek bir uygulama ile degerlendirme bolumleri yer almaktadir
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Purpose The purpose of this paper is to present a mixed integer programming model for simple assembly line balancing problems (SALBP) with Type 1 when the annual demand and task durations are uncertain and encoded with grey numbers.... more
Purpose The purpose of this paper is to present a mixed integer programming model for simple assembly line balancing problems (SALBP) with Type 1 when the annual demand and task durations are uncertain and encoded with grey numbers. Design/methodology/approach Grey theory and grey numbers are used for illustrating the uncertainty of parameters in an SALBP, where the objective is to minimize the total number of workstations. The paper proposes a 0-1 mathematical model for SALBP of Type 1 with grey demand and grey task durations. Findings The uncertainty of the demand and task durations are encoded with grey numbers and a well-known 0-1 mathematical model for SALBP of Type 1 is modified to find the minimum number of workstations in order to meet both the lower and upper bounds of the uncertain demand. The results obtained from the proposed mathematical model show a task-workstation assignment that does not distribute precedence relations among tasks and workstations and the sum of tas...
Project scheduling has been still one of the hottest topics in the management area. The goal of traditional project management is to complete the project at the earliest possible time in accordance with the available resources without... more
Project scheduling has been still one of the hottest topics in the management area. The goal of traditional project management is to complete the project at the earliest possible time in accordance with the available resources without violating priority relations of the activities involved. Unlike traditional project management, this study deals with the possibility of a coalition among the staff available to accomplish tasks of the project. The tasks can be fulfilled by more than one staff members. Staff’s coalition shortens the completion time of the tasks. A natural problem that arises in this case is how to share the income generated. The other side of the problem is concerned with the project owner who wants the project to be completed as early as possible. In this study, a mathematical model proposal is dealt with in order to real-ize the goals of both the project owner and the staffs as much as possible within the complex structure of the situation.
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Decision making process is a process which includes decision makers, actors, environmental factors, objectives, strategies and criteria. In competitive environments, effectiveness of decision process depends on determining all... more
Decision making process is a process which includes decision makers, actors, environmental factors, objectives, strategies and criteria. In competitive environments, effectiveness of decision process depends on determining all environmental factors and evaluating them according to objectives. Decision makers aim to find optimal strategies for conflicting objectives. Game theory is an approach based on mathematics in which strategies of players are evaluated reciprocally by considering environmental effects.In this study, a two-person zero-sum game approach is presented for choosing optimal strategies of actors in competitive environment by balancing objectives reciprocally. This approach refers to evaluation of each objective, creation of decision payoff matrixes by using fuzzy logic mathematical applications and their transformation to final decision payoff matrix subsequently. Finally, optimal strategies and their probabilities are found. A military case study is presented for ill...
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This paper studies a real-life public sector facility location problem. The problem fundamentally originated from the idea of downsizing the number of service centres. However, opening of new facilities is also considered in case the... more
This paper studies a real-life public sector facility location problem. The problem fundamentally originated from the idea of downsizing the number of service centres. However, opening of new facilities is also considered in case the current facilities fail to fulfil general management demands. Two operation research methodologies are used to solve the problem and the obtained results are compared. First, a mathematical programming model is introduced to determine where the new facilities will be located, and which districts get service from which facilities, as if there were currently no existing facilities. Second, the Stochastic Multi-criteria Acceptability Analysis-TRI (SMAA-TRI) method is used to select the best suitable places for service centres among the existing facilities. It is noted that the application of mathematical programming model and SMAA-TRI integration approach on facility location problem is the first study in literature. Compression of outcomes shows that mixe...
Decision making process is a process which includes decision makers, actors, environmental factors, objectives, strategies and criteria. In competitive environments, effectiveness of decision process depends on determining all... more
Decision making process is a process which includes decision makers, actors, environmental factors, objectives, strategies and criteria. In competitive environments, effectiveness of decision process depends on determining all environmental factors and evaluating them according to objectives. Decision makers aim to find optimal strategies for conflicting objectives. Game theory is an approach based on mathematics in which strategies of players are evaluated reciprocally by considering environmental effects.In this study, a two-person zero-sum game approach is presented for choosing optimal strategies of actors in competitive environment by balancing objectives reciprocally. This approach refers to evaluation of each objective, creation of decision payoff matrixes by using fuzzy logic mathematical applications and their transformation to final decision payoff matrix subsequently. Finally, optimal strategies and their probabilities are found. A military case study is presented for ill...
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In this study, a military decision problem is handled by an integrated approach based on game theory and geographical information systems (GIS). The problem can be defined as: finding layout plan for troops who want to maximize... more
In this study, a military decision problem is handled by an integrated approach based on game theory and geographical information systems (GIS). The problem can be defined as: finding layout plan for troops who want to maximize probability of identifying enemies using particular routes to penetrate border line. The problem has been transformed to two-person zero-sum game by some assumptions and solved in four interconnected stages. First, suitable spots in the terrain for monitoring the enemies were identified. Then, visibility percentages of each of the spots were calculated by using GIS for the routes used by enemies to pass the border line. Next, by assuming the calculated visibility ratios as the probability of identifying the enemy, a two-person zero-sum payoff matrix was formed. Finally , linear mathematical model established to obtain optimal strategies with their probabilities. There are many techniques in literature to solve military decision problems but we believe that this study, by holding the peculiarity of the first study in which game theory and GIS are used together, will make a significant contribution to literature and future studies.
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ABSRACT The classic prediction methods take the system behavior as a stochastic process, using probability and statistics, searching the laws of massive historical data. However, since the statistical approaches are efficient with large... more
ABSRACT The classic prediction methods take the system behavior as a stochastic process, using probability and statistics, searching the laws of massive historical data. However, since the statistical approaches are efficient with large volumes of data, they cannot work well in case of plenty information unavailable. The main purpose of the grey system theory is to predict uncertain systems behaviors' with limited number of data. It does differ from statistical analysis method as it does not deal directly with the original data and searches the intrinsic regularity of the data. In this study, deformation consisting on the crest of the Keban Dam in Turkey is aimed to determine by using multivariable grey prediction models GM(0,N) and GM(1,N). The outcomes show that GM(1,N) produces much more reliable results than GM(0,N) on prediction of deformation. The outcomes also confirm that there are very high level of relation between water level and deformation in a dam.
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In this study, contrary to the classical Economic Order Quantity (EOQ) models unit holding and order cost parameters are included in the model as interval grey numbers and the grey prediction model has been used to forecast annual demand... more
In this study, contrary to the classical Economic Order Quantity (EOQ) models unit holding and order cost parameters are included in the model as interval grey numbers and the grey prediction model has been used to forecast annual demand rate. To determine optimal order quantity, total cost function, which is also an interval grey numer mathematical operations. The total cost function has been whitenized first by using equal qeight mean whitenization then fuzzy mathematical programming methods and obtained results have been compared for different cost parameters. The analysis of the results show that for whetinization of interval valued functions equal weight mean whitenization method is better than fuzzy mathematical programming method which needs very complicated mathematical operations.