itüdergisi (E-Journals - İstanbul Teknik Üniversitesi, Istanbul Teknik Uniersity., İTÜ)
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Evaluation of solid waste disposal sites in Istanbul according to landscape planning
Full text linkBu çalışma, İstanbul kenti yerleşik alanları içerisinde kalmış işlev dışı durumdaki eski katı atık alanlarının varlığını çözülmesi gereken temel sorun olarak ele almaktadır. Bu sorun çerçevesinde geliştirilen değerlendirme süreci, “fiziksel uygunluğa dair değerlendirme süreci” ve “planlama uygunluğuna dair değerlendirme süreci” olmak üzere iki aşamalı şekilde ele alınmıştır. Fiziksel uygunluğa dair değerlendirme süreci sonunda, İstanbul kenti katı atık alanları için kritik öneme sahip olan düzenleme ilkeleri dikkate alınarak, atık alanı iç dinamikleri ile uyumlu kullanımların; ekolojik, rekreasyonel ve ticari kullanım olduğu belirlenmiştir. Planlama uygunluğuna dair değerlendirme sürecinde, örnek alanların kentsel dokuya entegrasyonlarını sağlayacak yeni kullanımları belirleyen özgün bir karar destek aracı şekillendirilmiştir. Bu yöntem, katı atık alanları ile etkileşim bölgelerini CBS yardımıyla inceleyerek istatistiksel tekniklerle karşılaştırmaktadır. Oluşturulan karar destek aracı ile katı atık alanlarının düzenlenme öncelikleri saptanmakta ve ekolojik, sosyal, ekonomik potansiyellerine göre uygun yeni kullanım kararları alınabilmektedir. Bu kapsamda değerlendirilmeye alınan beş adet eski katı atık alanından biri kabul edilebilirlik sınırının altında kalarak rezerv açık alan olarak bırakılmış, diğer katı atık alanlarına ise ıslah düzenlemelerinde etkili olan yasal, yönetimsel, planlama ve uygulamaya yönelik etkenlerin değerlendirilmesi sonucunda sürdürülebilir yeni kullanımlar tanımlanmıştır. Anahtar Kelimeler: Eski katı atık alanları, sürdürülebilir planlama, CBS, peyzaj onarımı. This study focuses on the existence of improper solid waste disposal sites in settlements, and difficulties in assigning functions to these underutilized areas. By considering this basic problem, a two phased evaluation process is developed which concerns the phases of "physical suitability" and "planning suitability".In this evaluation process, physical suitability criterion takes the first phase and declares land use types compatible with the restrictive factors of solid waste disposal sites and also critically important principles of hard and soft landscape design. There are four main restrictive factors on redevelopment of solid waste disposal sites and three of these four factors decrease with time as organic material in waste decomposes. Hence solid waste disposal sites are going to be in change for approximately 30 years, after the closure. Regarding this natural stabilization process, former solid waste disposal sites should be redeveloped phase by phase in a transition from extensive to intensive land uses. Change estimation is an important technique for detecting land uses compatible with these restrictive factors. However it is problematic to estimate changes for the former disposal sites of Istanbul as they were initially improper disposal sites. Problems regarding to change estimation narrow the range of land uses compatible with restrictive factors. According to physical suitability criterion, land use types compatible with the former solid waste disposal sites of Istanbul are determined as ecological, recreational and commercial land uses. Planning suitability criterion takes the second phase of this evaluation process and declares the new land uses capable of integrating into urban system regarding the case areas of this study. In this phase, an original decision support tool is constituted for making decisions compatible with dynamics of Istanbul. After digitizing the land use data about the interaction regions of solid waste disposal sites in GIS, the data are evaluated inside a decision matrix. Pre-values obtained from decision matrix are analyzed by statistical methods in order to declare suitable new land uses. Undoubtedly, interpretation of statistical results is needed according to landscape planning principles, and they should be suitable to the legal and administrative situations. In the second half of 1990's, owing to the risks posed on environmental health and safety, 5 irregular solid waste disposal sites were reclaimed according to engineering techniques in Istanbul. However, after their reclamations they left non-functional, hence selected as the case areas of this study. In this study, ecological, social, economic and total potential values are calculated for each of the solid waste disposal sites by the activation of decision support tool consisting of 21 parameters with their own coefficients. By the evaluation process of physical suitability, new land uses compatible with the internal dynamics of solid waste disposal sites are determined. Provided that critically important design principles are utilized, ecological, recreational and commercial land uses are determined as suitable. Ecological, social and economic potentials calculated by the activation of decision support tool, endorse these assigned land uses. Following the statistical analysis of decision support tool's pre-values through Kruskal Wallis H, Mann Whitney U, and One Way ANOVA tests and further analyses of these statistical results, final results about the potentials of solid waste disposal sites are obtained. According to these results, for new uses, it is necessary to arrange Küçükçekmece, Kemerburgaz and then similar sites of Yakacık and Ümraniye, in the order of importance. Aydınlı solid waste disposal site's total potential value is lower than the "limit of acceptability" therefore it is kept separate as a reserve open space. Besides ranking the solid waste disposal sites according to their potentials for opening to new uses, this decision support tool declares about the sustainable use potentials of these sites. Therefore, decisions are made about the transformation of Küçükçekmece disposal site to recreational and commercial multiple use; Kemerburgaz site to ecologically based recreational use; Yakacık site to recreational and commercial multiple use; and Umraniye site to recreational use. This decision support tool is proved to be effective on making decisions about solid waste related problematic sites. Therefore, it is possible to adapt this tool for diverse contaminated sites. By the development of this decision support tool for the entire contaminated sites of Istanbul, it is expected to construct a citywide data base on contaminated sites, hence having positive impact on urban matrix. Keywords: Former solid waste disposal sites, sustainable planning, GIS, landscape restoration
Developing a multi-criteria performance measurement model for construction contractors
Full text linkSon yirmi yılda global ölçekte artan rekabet, müşteri talepleri ve yüksek kalite gereksinimleri inşaat endüstrisini performans ve performans ölçümü kavramları hakkında daha fazla dikkat harcamaya zorlamıştır. İnşaat endüstrisinde performans ölçümü genellikle finansal yönelimli ve performans araştırmaları da büyük oranda proje seviyesine odaklıdır. Ancak son zamanlarda firma seviyesinde performansın değerlendirmesi ve yönetimi için talep artmıştır. İnşaat endüstrisinde firma seviyesinde performans ölçümü kavramsal çerçevesi geliştirmeye odaklı birkaç çalışma sözkonusudur. Diğer endüstrilere kıyasla inşaat endüstrisi performans ölçümü uygulamalarında hiç bir zaman lider olmadığı gibi düşük performansı ile ilgili üne sahiptir. Bugüne kadar pek çok araştırmacı Türk inşaat endüstrisinde düşük performansa sebep olan sorunlara dikkat çekmiştir. Ancak konu ile ilgili olarak Türk yüklenici firmaları özelinde bir “performans ölçme modeli veya sistemi” çalışmasına literatürde rastlanmamıştır. Böylelikle, Türk yüklenici inşaat firmaları için performansın, kendi perspektiflerinden ölçülmesi için bir model geliştirilmesi araştırma problemi olarak seçilmiştir. Araştırmada, üretim ve inşaat endüstrisinde geliştirilmiş performans ölçme model ve kavramsal çerçevelerinin tüm performans boyut ve kriterlerini bir araya getiren, kapsamlı bir model oluşturulması hedeflenmiştir. Bu yaklaşım, içeriksel geçerliliğin sağlanması açısından da önemlidir. AHS (Analitik Hiyerarşi Süreci) yöntemi ile model bileşenlerinin önem ağırlıkları belirlenmiştir. Çok kriterli performans ölçme modeli, performans boyut ve performans kriterlerinden oluşan 3 düzeyli hiyerarşik bir yapıda oluşturulmuştur. Model, yüklenici inşaat firması yöneticilerine performans ölçme sistemlerini oluştururken kullanabilecekleri kapsamlı ve pragmatik bir araç önermektedir. Anahtar Kelimeler: Analitik hiyerarşi süreci yöntemi, performans ölçümü, yüklenici inşaat firmaları.Increased competition, customer demands, and higher quality requirements in the global environment have all forced the construction industry to pay much more attention to the concept of "performance" over the last two decades. The construction industry has mainly relied on financially focused performance measurements, and studies and research have been carried out mostly at the project level. However, recently, the demand for performance evaluation and management at the company level has increased. A few previous efforts have aimed to develop a conceptual framework for firm level performance, but there have been few follow-up studies. In comparison to other industries, construction has not been a leader in performance measurement practice and known worldwide for its poor measurement culture. Hence, it is worthwhile understanding the need for a performance measurement framework for Turkish contractors' context. Many large contractors in Turkey are lacking an effective method to measure their performance. The need for measuring performance in structured and systematic approaches is also a necessity for Turkish construction contractors. Moreover there has not been any investigation for the existing situation of current applications of performance measurement in leading Turkish contractors. In this regards, the main objective of this research is to develop a multi- criteria performance measurement model for contractors. This model, would enable contractors to measure their business performance by using performance dimensions, criteria and related performance indicators which were important for their performance perceptions. The objective of accumulating knowledge by building on the findings of other researchers is a central characteristic of all organizational research. Hence literature reviews carried out for this research and describes the performance dimensions, performance criterias from this knowledge acquisition process step for formulating the multi-criteria performance measurement model. Determination of performance dimensions and criterias by a simple frequency analysis and normative refinement for proposed measurement model was employed. The multi criteria performance measurement model uses the existing performance measurement models, frameworks with the addition of a number of elements and perspectives. Each framework focuses on different facets of performance. Therefore, in developing a comprehensive framework, it is only logical to build upon the principles of the existing frameworks. The logic of the model is to cover all performance perspectives from existing frameworks for comprehensiveness and thus enhancing the initial (content) validity of the formulated framework. Hence, the formulation process started by integrating the performance perspectives of the existing models and frameworks. Considering the inherent complexities of the construction activity itself, only an adequate combination of criteria allows assessing the contractors' performance. Having set out the performance dimensions, related criteria, the research then considered to develop a model that represents the relative importance weights of model constructs by using Analytic Hierarchy Process method (AHP). AHP is primarily a tool for the evaluation of alternatives and the selection of the best alternative. In the current application, however, there are no alternatives per se, and thus AHP, used here to determine the relative weight of each of the construct of the model, is executed short of the final stage in which alternatives would be evaluated according to the weighted attributes. The questionnaire survey, was executed for eliciting the relative weights of the model constructs according to the evaluations from nine upper level managers of world-wide reputable Turkey's leading construction contractors who were served on the AHP expert panel. The section outlines a concise review of AHP fundamentals, followed by a more detailed description of how AHP was specifically applied in the current study. The multi-criteria performance measurement model proposed in this study uses a three-level hierarchical structure to combine performance dimensions and performance criteria. The model focuses on using performance measurement for internal management purposes from the internal measurement point of view. The developed model represents a pragmatic tool capable of supporting construction managers in structuring an in-house performance measurement system by integrating the several key performance indicators. Keywords: Analitic hierarcy process, construction contractors , performance measurement
Image as a narrative in architecture
Full text linkGünümüz görsel kültür ortamında indirgemeci bir yaklaşımla tek katmanlı olarak ele alınan imge kavramının zihinsel soyutlama yeteneğini zayıflattığı, düşünsel üretimin araçsallaştırılmasına neden olduğu düşünülmektedir. Bu bağlamda, mimarlıkta eleştirel düşünceyi tetikleyen imge kavramına farklı disiplinlerin penceresinden bakmak, farklı kavramlarla onu yeniden anlamlandırmak gerekmektedir. Bu çalışmada, nesnel biçimden zihinsel kurgu temsiline uzanan geniş bir yelpazede anlamlandırılan imge sorunsalı, eleştirel bir bakış açısıyla irdelenmekte ve mimarlıkta ilişkisel bilginin üretimine yol açabilecek bir okuma yöntemi önerilmektedir. Gündelik dilde görüntü ve biçim yerine kullanılan imgenin, biçime indirgenen yüzeysel algılama ve düşünme süreçlerine karşın imgeyi bir “anlatı olarak okuma”nın mimarlık bilgisinin üretimi için alternatif bir yaklaşım olabileceği tartışılmaktadır. Anlatı, zamansal deneyimin özelliklerini gösterdiği ölçüde yapılı çevrenin olay örgüsüne gönderme yapar. Anlatı olarak imge, bütüncül bir bakış açısı ile elde edilen mimarlık bilgisine ait “büyük resmi” bir olay örgüsüne dönüştürür. Herhangi bir yapılı çevreye ait imgenin katmanlı yapısı ve bu katmanlar arası ilişkileri bir olay örgüsüne dönüştürme sürecinde anlama, doğrusal düşünme biçimi yerine ağ ilişkisi ile temsil edilen karmaşık bir düşünme biçimini zorunlu kılar. Bu çalışmada imgeyi bir anlatı olarak okuma yöntemi, ilişkisel bilgiye ulaşmada bir örneklem olarak Kayseri Sahabiye Mahallesi imgesi üzerinden önerilmektedir. Tikel bir durum olan Sahabiye Mahallesi örneklemini genellenebilir kuramsal bilgi ile ilişkilendirerek deneyimleme; diğer bir deyişle, yapılı çevrenin katmanlı imge okumasını - tikel ve genel arasında gidip gelme hareketiyle eklenerek çoğalan ilişkisel bilgiye dönüştürme stratejisi, tezin kendine özgü yöntemini açıklamaktadır. Anahtar Kelimeler: Görsel kültür, imge, eleştiri, ilişkisel bilgi, anlatı / olay örgüsü. This study, proposes a method for the use of the "image" in architectural criticism, which is perceived as problematic of being a single layered, reductionist concept and dominating the mental processes figuratively. In everyday language, it is being used to define a wide spectrum of meanings from figural to the mental and expresses the thought, representation and criticism. For this reason, to redefine the concept of image as a narrative became necessary, in the field of architecture. In this study, it is argued that, reading the image as a narrative will recover the concept being shallow and reductionist, as it is understood extensively. It is thought that, reading the image as a narrative can be used as a key concept to generate the architectural knowledge from the built environment. In this context, it is thought that understanding and interpreting the "big picture" of architecture can be presented according to the holistic approach. Consequently, the image is presented with its multi-layered properties and the relations between these layers are important in understanding the meaning of the concept, which emerges within the network relations. This relationship requires both a mental process that will include the subject's background and priorities and the affordances of the environment. The narrative of the image is therefore thought to be emerged as the interactive relationship of the object and the subject. It is thought that, the cities, as living spaces having cultural codes, cannot be understood only by syntactic and analytic methods. Togetherness of the subject and the object is needed in order to solve the puzzle like structures of these environments. In such an understanding, the researcher has to experience the research area using her intentionality and try to find out the relations hidden among the layers of the environment. These relations can be considered as "a fold", as a Deleuzian concept, which allows all the layers reflect each other, and make visible the other. The intentionality of the researcher caused by the synergy of these relations will produce a fertile ground for exploring new layers of meanings that cannot be seen only by looking at. Image, considered as a mental construct, represents the subjective thought and the knowledge of the phenomenon can include many meanings. In architectural criticism, it is important to recognize the word as a loaded concept, and not to prefer or stick one of the meanings. According to the holistic approach, none of them is more important than the other, and the whole is greater than the parts. Reading the image of Sahabiye District in Kayseri as a narrative has been considered as an exemplar in this study. It is difficult to explain how to read the image of Sahabiye District as a narrative because of its multi-layered and complex structure having too many cultural codes superimposed within old and new environments. To recognize the experiential, cultural, historical, textural and social contrasts in the district makes its image multi-layered while reading the image as a narrative. The inexhaustibility of contrast (Ross, 1994), proposes an unlimited energy resulting from the tension of the opposing but complementary concepts. This tension makes each of these concepts being visible simultaneously. Sustainability referring to both continuity and change which represents contrast is another concept facilitates reading the image of Sahabiye District. The researcher, as an old resident of the district has a sustainable experience in there. The first-person phenomenological research method (Seamon, 2003) is adapted in this research in order to understand the deep meaning of this experience. Multi layered character of the image of this district, besides the empathic devotion and the theoretical background of the researcher makes the image of the Sahabiye District an exemplar give rise to relational knowledge. In this research, it is emphasized that reading the image of a build environment as a narrative can be translated to a generalized and sustainable knowledge which is contextual and specific to this environment. Reading the image of Sahabiye District as a narrative therefore exemplifies the proposed method based on web of events which is open to critical knowledge. As an exemplar, narrating Sahabiye District will give rise to an in-between reality concerning singularity and multiplicity and having a potential to move between a specific and general knowledge. As a result, reading the image as a narrative in architectural environments introduces some possibilities for translating the multi-layered structures of the cityscape to critical knowledge that can be used for preservation and gentrification projects. Keywords: visual culture, image, architectural criticism, relational knowledge, narrative / web of event
Effect of pozzolanic materials on the mechanical properties and chloride diffusivity of concrete
Full text linkYapılan deneysel çalışmada iki farklı seri beton üretildi. İlk seri betonlarda; portland çimentosu ince öğütülmüş F tipi uçucu kül ile yerdeğiştirildi, ikinci seri betonlarda ise çimentonun yerdeğiştirilmesi ince öğütülmüş yüksek fırın cürufu ile yapıldı. Çalışmanın ilk bölümünde ince öğütülmüş (Blaine özgül yüzeyi 604 m2/kg) uçucu kül miktarının betonun basınç dayanımına ve hızlı klor geçirimliliğine etkisi incelendi. Sabit 0.35 su/bağlayıcı oranında betonlar üretilerek her üretimdeki toplam bağlayıcı madde miktarı sabit tutuldu ve uçucu kül çimento ile %70’e kadar yerdeğiştirilerek kullanıldı. Uçucu külün çimentoyla yerdeğiştirilmesi bire bir ağırlık esasına göre ve %10’luk adımlarla yapıldı. Üretilen betonların çeşitli yaşlarındaki basınç dayanımları bulundu. Bu betonların üzerinde ayrıca ASTM C 1202 standardına göre hızlı klor geçirimlilik deneyleri de yapıldı. Çimentonun % 40 oranında ince uçucu külle yerdeğiştirilmesi durumunda beton basınç dayanımları yaklaşık aynı oldu. Betonda ince öğütülmüş uçucu kül kullanımı ile klor geçirimlilikleri önemli ölçüde azaldı. Çalışmanın ikinci bölümünde ise; aynı su/çimento oranına sahip betonlarda, çimento ince öğütülmüş yüksek fırın cürufu ile %40, %60 ve %80 oranlarında yerdeğiştirildi. Blaine özgül yüzeyi 5000 cm2/gr olan cürufun çimentoyla yerdeğiştirmesi yine bire bir ağırlık esasına göre yapıldı. Üretilen bu betonlarda ise klor iyonu yayınımı ve elektriksel özdirenç deneyleri yapıldı. Elde sonuçlar cüruf ilave edilmesinin betonların klor iyonu geçirimliliklerinin önemli oranda azalttığını ortaya koydu. Cüruf içeren betonların elektriksel özdirençleri de, sadece portland çimentosu ile üretilen betonlara göre büyük oranlarda arttı. Elektriksel özdirenç ölçümlerinin, yapı inşaa sürecinde, elde edilen beton klor geçirimliliklerinin izlenmesi ve kalite kontrolü için uygun bir yöntem olduğu sonucuna varıldı. Anahtar Kelimeler: Puzolan, mekanik özelikler, dürabilite, klor yayınımı, elektriksel özdirenç.The primary objective of the present work is to study the effects of pozzolans on the mechanical and durability properties of concrete. Fly ash and granulated blast furnace slag were used in the study. In order to utilize the potential of these materials and obtain better concrete performance, pozzolans with smaller particle sizes were used, which were obtained by grinding. The experimental study consists of two parts. In the first part, effects of ground fly ash on the concrete properties were investigated. The effect of ground granulated blast-furnace slag on the chloride diffusivity of concrete was the main focus of the second part of the study. In the first part, a coarse F type fly ash was ground to a Blaine surface area of 604 m2/kg. The test results show that the physical properties such as density and fineness changed. The physical changes due to grinding are: i) the fineness of fly ash increases, ii) there is a remarkable increase in density by reducing the porosity of the fly ash particles, iii) the spherical fly ash particles transform into the mostly irregular shapes; some small fly ash particles keep their original shapes. For investigating the effects of ground fly ash, eight concrete mixtures were prepared using the same batch of ordinary portland cement (OPC) and ground low-lime fly ash. The aggregate grading used in the mixtures of concrete, water-binder ratio, and the maximum particle size of aggregate were kept constant in all concretes, but the partial replacement of cement by fly ash was varied from 0 % (OPC concrete) to 70 %, in steps of 10 %. The replacement was on one to one weight basis. Compressive strengths of the concretes were obtained for different ages. Rapid chloride permeability test was also carried out on the 1 year old specimens. At 28 days, there was little reduction in compressive strength up to 40 % cement replacement by ground fly ash; then significant decrease was recorded for the further fly ash dosages. At 56 and 120 days, however, the compressive strength up to 40 % cement replacement by fly ash was almost identical to that of the no fly ash concrete and for one year it was even higher. Beyond 40 % replacement, the compressive strength decreased significantly for the age of 1 year. The results of the rapid chloride penetration tests indicated that high volume ground fly ash concrete had much better resistance to the penetration of chloride ions. The main objective of the second part of the experimental study was to investigate the effect of ground granulated blast-furnace slag on the chloride diffusivity of concrete. Concretes with constant water/binder ratio were produced, in which an ordinary portland cement was partially replaced by a ground granulated blast-furnace slag with the replacement ratios of 40%, 60% and 80%, respectively. The slag used had a high fineness with a Blaine specific surface of 5000 cm2/gr. Accelerated chloride diffusivity tests based on migration testing were carried out on the concretes. In parallel, testing of electrical resistivity was also conducted. The resistivity of the concretes were obtained by two different test methods; i) two electrode method, and ii) four electrode method. The concretes containing granulated blast - furnace slag showed a significantly better resistance against chloride penetration when compared to that of the pure portland cement. Results proved that slag replacement ratio is a major factor for reducing the chloride diffusivity and the diffusivity decreased with the increasing slag amount. Incorporation of slag had an important effect also on the electrical resistivity of concrete and the resistivity of the concretes containing slag were substantially higher than that of the portland cement concrete. This increase in resistivity became more distinct with the increase in replacement ratio. For a given type of concrete and test conditions, the test results confirmed that there is a linear relationship between chloride diffusivity and electrical resistivity. Hence, as soon as this relationship is established, the test results also confirmed that a monitoring of electrical resistivity may be a very appropriate way for monitoring the chloride diffusivity as part of a general quality control during the concrete construction. Keywords: Pozzolan, mechanical properties, durability, chloride diffusivity, electrical resistivity
Simulation supported analytic hierar-chy approach in public transport mode selection
Full text linkUlaştırma yatırımları ve özellikle de kentiçi koridorlarda gerçekleştirilecek olan toplu taşıma yatırımlarında hangi ulaştırma türünün tercih edileceği son derece önemli bir karardır. Bu tercihte bir bölümü nicel bir bölümü ise nitel olan pek çok faktör etkili olur. Ölçüt olarak kabul edilen bu faktörlerin hepsinin birlikte değerlendirmede etkili olmasını sağlayacak yöntemlerden bir tanesi, bir çok ölçütlü karar verme yöntemi olan analitik hiyerarşi yöntemidir. Bu çalışmada bir kentiçi koridorda, hangi toplu taşıma sisteminin uygulanması gerektiğine ilişkin verilecek olan karar süreci için analitik hiyerarşi yöntemi uygulanmıştır. Öte yandan, toplu taşıma türünün seçimi, seçenek türlerin performanslarının koşullara göre nasıl değişeceği öngörülerek yapılmalıdır. Toplu taşıma sistemlerinde performans göstergelerinden önemli bir tanesi taşıtların yolculuk süreleridir. Taşıtların yolculuk süreleri bir dizi etmene göre değişmektedir. Değişen yolcu talebi, durak aralıkları, ödeme türü ve buna bağlı olarak ödeme süresi, taşıt hızı, yolcuların taşıtlara biniş ve iniş süresi gibi koşullara göre toplu taşıma sistemlerinin performanslarının nasıl değiştiğini görebilmek için bu çalışmada bir simülasyon modeli geliştirilmiştir. Bu simülasyon modeli ile elde edilen sonuçlar, toplu taşıma türleri arasında seçim yapılması amacıyla kullanılan analitik hiyerarşi yöntemine uyarlanmıştır. Analitik hiyerarşi yönteminde, toplu taşıma türü seçimi için göz önüne alınacak diğer ölçütler belirlenmiştir. Ölçütlerin kendi aralarında ve iki toplu taşıma türü seçeneği için ağırlıkları anket ve sayısal değerlerin karşılaştırılması ile saptanmıştır. Bu simülasyon destekli analitik hiyerarşi yöntemi, İstanbul kenti içerisindeki iki koridorda “otobüs yolu” ve “tramvay” seçenekleri için uygulanmıştır.Anahtar Kelimeler: Toplu taşıma, simülasyon, çok ölçütlü karar verme, analitik hiyerarşi yöntemi.Critical decisions that are taken at the stage of planning new transportation investments or improving present transportation systems usually turn out to be selecting one alternative among others. The most important condition in transport mode selection is to make a comparison between different alternatives. This comparison stage is perhaps the most precision-requiring stage in the transport mode selection process. The comparison process has many difficulties. The foremost difficulty is to decide on the factors to be included in the comparison. Some of these factors are quantitative or are capable of being quantified; many others are qualitative. Evaluation of the qualitative factors requires experience and enforces the correct jurisdictions. Therefore, defining the comparison process with just a quantitative model is not meaningful. Accordingly, expressing the results of the comparison analysis with just a single quantitative value would not be accurate. One of the important problems in comparing investment alternatives come out in including the some criteria that cannot be expressed numerically in the analysis. These kinds of criteria are either incorrectly quantified and included in the analysis or they are being tried to be evaluated verbally. In this study, one of the methods that are developed for including both numerical and nonnumeric criteria in the evaluation, the analytical hierarchy method is used. This method is supported by a travel time simulation model; and an application that can be useful in public transport mode selection is made. When deciding on a new investment that is going to be made within an urban public transport system, several criteria, which expand over a broad scale, should be taken into consideration. Since they make non-numerical important factors considerable, using multiple criteria decision making processes will be more meaningful in selecting a public transport mode. Analytical hierarchy method, which is one of multiple criteria decision making methods, is used in this study. This method provides meaningful results because of its simplicity and its ability to be adopted for different conditions. For evaluating some of the varying physical conditions, a simulation model is developed and used. Thus, the proposed method can be called a simulation supported analytic hierarchy method. Forecasting the possible performance of a public transport mode in a corridor has numerous benefits. It is important to forecast the performance in order to make accurate decisions on factors like vehicle frequency, station places and station spacing and in deciding between more than one alternative. The varying performance of a public transport based on characteristics like varying passenger demand, speed, station spacing and boarding/alighting time (according to payment type and other physical factors) system can be forecasted with the help of a simulation model. Such a simulation model is developed in this study. The performance indicator in the model is travel time. The model is run separately for busway and tram systems. In this study, two different examples for an urban corridor on which a public transport system will be built were taken into consideration. The alternatives of “busway” and “tram” were evaluated in the two examples, which are the Beşiktaş-Levent and Taksim-Aksaray corridors. As stated above, the analytical hierarchy method was utilised in deciding on the public transport alternative. In the analytical hierarchy method, first, the weights (w) of each alternative and each criterion should be estimated. A survey was organised in order to receive the experts’ opinions. After assessing the expert opinions gathered through the survey, relative weights of each criterion was determined. In the following step, the weights of each criterion for each of the public transport alternatives were estimated. For quantitative criteria, information from different sources was used; while for non-quantitative criteria, the second part of the survey was utilised. The weights of the criteria at the lower level of the hierarchy, which was defined by the analytical hierarchy method, were estimated for busway and tram alternatives through the method explained above. In the following step, these weights were multiplied by the criteria’s own weights that are placed in the middle level of the hierarchy. The results for each alternative were then summed up in order to find a total weight for each alternative. The results show that the relative weight of the busway is slightly higher than that of the tram’s. With the analytical hierarchy method, the busway is found out to be a more preferable option than the tram. Keywords: Public transport, simulation, multiple-criteria decision making, analytic hierarchy process
Dikiş performansının optimizasyonu için on-line ölçme sisteminin kurulması
Full text linkIn this study, an on-line seam monitoring system has been set up to measure the forces coming out of sewing machine components due to tension of sewing threads and foot presser force in overlock sewing machine. The original presser foot bar has been equipped with strain gauges in order to measure the presser foot force of the machine. Moreover, the original components on the looper threads and the needle thread paths have been replaced with the new ones that are equipped with strain gauges in order to measure the forces generated by the needle thread, upper and lower looper threads. Thus, a system measuring these forces on-line has been established. After, the sewing thread tensions were determined. When the sewing threads pass the thread guide, they will be effected by friction. Therefore, friction forces are considered and in order to see effects of friction, the thread in tension and the thread out tension were determined. Consequently, the sewing thread tensions and the presser foot forces were determined. In this work, the effects of friction and sewing thread's properties on the tensions of the needle thread, upper and lower looper threads, have been analysed and faults coming out during seam process can be determined through this on-line seam monitoring system. Keywords: On-line seam monitoring system, tensions of sewing threads, friction, overlock sewing machine. Bu çalışmada, dikim işlemi sırasında dinamik iplik gerginlikleri ve baskı ayağı kuvvetini ölçmek için on-line ölçme ve izleme sistemi geliştirilmiştir. Öncelikle, dikiş makinasında orijinal baskı ayağı çubuğuna gerilmeölçerler yerleştirilmiştir. İğne, üst lüper ve alt lüper ipliklerinin geçtiği orjinal iplik kılavuzları çıkarılarak, yerlerine üzerlerine gerilmeölçerler yapıştırılan yeni parçalar takılmıştır. Daha sonra, dikiş ipliklerinde oluşan gerginlik kuvvetleri hesaplanmıştır. Dikiş iplikleri kılavuzlardan geçerken oluşan sürtünmenin etkisini görmek için, dikiş ipliği giriş ve çıkış kuvvetleri bulunmuştur. Çalışmada, sürtünmenin ve dikiş ipliği özelliklerinin dikiş ipliği gerginlikleri üzerine etkisi incelenmiş ve dikim işlemi sırasında oluşan dikiş hatalarının on-line izleme sistemi ile belirlenmesi sağlanmıştır. Anahtar Kelimeler: On-line dikiş ölçme sistemi, dikiş ipliği gerginlikleri, sürtünme, overlok dikiş makinası.  
Çok amaçlı karar verme problemlerine etkileşimli bir yaklaşım
Full text linkIn this study, SEMOPS approach, which is an interactive method for solving multiobjective decision making problems, is examined. Water quality management of a river is chosen as an exemplary problem since it has several decision variables, objectives and constraints which are generally nonlinear, and solved interactively by using SEMOPS method. In order to use the known SEMOPS algorithm, a MATLAB based computer program has been developed. And a graphical user interface has also been created to evaluate the results and give the selections which are necessary for the next cycle back to the program properly. The optimum results generated through the program according to defined objectives and constraints for the problem are evaluated by the decision maker in each cycle. And for the next cycle, assignment of the aspiration levels as constraints is performed. These cycles continue until the desired aspiration levels for all objectives are achieved. Using this interactive method enables the decision maker both to revise the aspiration levels according to objectives and to reach the desired results step by step in the solution stages of the problem flexibly. With this computer program, the dialog between the decision maker and the analyst has been eliminated and the spending time until reaching the best compromise solution has considerably been short. Keywords: Multiobjective decision making, Optimization, SEMOPS method. Bu çalışmada; Çok Amaçlı Karar Verme Problemlerinin Çözümü’ne yönelik etkileşimli bir yöntem olan SEMOPS (Sequental Multiobjective Problem Solving) yaklaşımı incelenmektedir. Bir nehrin su kalite yönetimi, çok sayıdaki amaç, kısıt, karar değişkenleri ve nonlineerlikleri nedeniyle örnek seçilmiş ve SEMOPS yöntemiyle etkileşimli olarak çözülmüştür. MATLAB tabanlı genel bir program geliştirilmiş ve sonuçların Karar Verici tarafından sağlıklı bir şekilde değerlendirilmesi ve bir sonraki adımda programa verilmesi gereken seçim bilgilerinin doğru yapılabilmesi için bir kullanıcı arayüzü oluşturulmuştur. Bu etkileşimli yöntemin kullanılması, Karar Vericiye problemin çözümü safhasında hem istek seviyelerini amaçlarına göre yeniden gözden geçirebilmesini hem de arzu ettiği sonuca adım adım ulaşması esnekliğini sağlamaktadır.Anahtar Kelimeler: Çok amaçlı karar verme, optimizasyon, SEMOPS yöntemi
Ammonia and pH inhibition in anaerobic treatment
Full text linkAmonyağın inhibe edici konsantrasyonlarına alıştırılmamış floküler ve granüler aşılarla karakterize edilen farklı anaerobik mikroorganizma gruplarının mezofilik şartlarda pH ve amonyak inhibisyonu karşısındaki davranışları toplam biyogaz üretiminin izlendiği metanojenik aktivite testi kullanılarak belirlenmiştir. Deneyler, dört farklı pH değerinde (6.8, 7.4, 7.8, 8.4) ve 6 farklı Toplam Amonyak Azotu (TAN) konsantrasyonunda (262 mg/l (kontrol), 1000, 1500, 2000, 2500, 3000) yürütülmüştür. Zamana karşı çizilen biyogaz üretim eğrileri kullanılarak eklenik metan üretim eğrileri elde edilmiştir. Eklenik metan üretim eğrilerinin modellenmesinde modifiye edilmiş Gompertz eşitliği kullanılmıştır. Değerlendirmeler sonucunda Gompertz modelinin, deneysel verilerin çok büyük bir kısmına iyi uyum gösterdiği bulunmuştur. Anahtar Kelimeler: Amonyak inhibisyonu, anaerobik arıtma, mezofilik şartlar, metan üretim fazı.The influences of pH and ammonia on methane production in the anaerobic treatment were investigated using two different sludge seeds. One of the seeds had a granular character whereas the other one had a flocular character. The sludge seeds used in the methanogenic activity tests were not exposed to high levels of ammonia at any stage before the tests. Four different pH values (6.8, 7.4, 7.8, 8.4) and six different TAN (Total Ammonia Nitrogen) values (262 mg/L (control), 1000, 1500, 2000, 2500, 3000) were used in the study. Cumulative methane production curves for both of the sludge seeds were obtained using the biogas production curves at four different pH values and six different TAN values. The modified Gompertz equation employed as a model for cumulative methane productions. It was concluded that this equation fits a large fraction of the data very well. At certain combinations of high pH and high TAN values, however, the cumulative methane production data manifested an initial ?hump? that cannot be predicted using the Gompertz equation. With flocular sludge seed, this happened at pH ? 7.8 and with TAN ? 1500-2000 mg/L. With granular sludge seed, this phenomenon was observed only at pH = 8.4 and with TAN ? 1000 mg/L. With both sludges, free ammonia was found to be much more inhibitory than the ammonium ion.Keywords: Ammonia inhibition, anaerobic treatment, mesophilic conditions, methanogenesis
A model for selecting appropriate techniques for information technology investment evaluation ? an application on ERP software selection
Full text linkBilişim Teknolojisi (BT) yatırımlarının fayda ve maliyetlerinin büyük bir kısmı, kolayca sayısallaştırılamamaktadır. Bu yüzden sadece finansal tekniklerle değerlendirildiklerinde, pek çok finansal olmayan fayda ve maliyetlerin hesaba katılmamış olması nedeniyle, sonuçlar, işletme yetkililerinin doğru kararlar almasına yardımcı olamaz. Bu çalışmada, işletmenin yapısına, istek ve önceliklerine, ve yatırımın türüne göre kullanılabilecek en uygun değerlendirme yönteminin seçilmesi için bir model önerilmektedir. Literatür taraması sonunda se [email protected] çilen 45 farklı BT değerlendirme yöntemi detaylı olarak incelenmiştir. İşletmenin yapısını, isteklerini ve yatırımın türünü gösteren kriterler belirlenmiştir. Yöntemlerin, bu kriterlerin hangi düzeyinde kullanılabileceği, model önerisiyle sunulmuştur. Modelin uygulanacağı işletmenin, kriterler hakkında verdiği bilgiler değerlendirmeye alınarak uygun yöntem listesi hazırlanmıştır. Anahtar Kelimeler: Bilişim teknolojisi yatırımları, yöntem seçme, yatırım değerlendirme yöntemleri, kurumsal kaynak planlaması (ERP), anket çalışması. Self-compacting concrete (SCC) has been developed using new generation superplasticizers and different mineral admixtures, and can be consolidated under its own weight without any vibration. It is suitable for high performance and densely reinforced structures as well as in most applications where traditionally vibrated concrete is used. The aim of this study is to investigate the effects of constituent materials on rheological properties of cement paste, mortar and concrete by application of factorial analysis method. Water/binder, mineral admixture/binder, chemical admixture/binder and sand/binder ratios were chosen as variables in the analysis. Slump-flow, viscosity (relative torque viscosity for concrete) and yield shear (relative yield torque for concrete) were rheological parameters and their variations by time up to 90 minutes were recorded. A fly ash and a silica fume were used as fine materials for partial substitution of the normal Portland cement. By the factorial analysis the composition factors significantly influencing the rheological properties are determined. Test results show that, although the cement paste and mortar prepared with self-compacting superplasticizer, act as Bingham materials, the yield torque for the concrete approaches to zero indicating approximately a Newtonian-material behaviour.Keywords: Self-compacting concrete, concrete viscosimeter, workability, rheology, superplasticizer, mineral admixture
Neotectonics of the South Marmara Sub-Region
Full text linkNeotektonik dönemde Kuzey Anadolu Fayı ve kolları, inceleme alanı ve Marmara Bölgesi’nde en etkin tektonik yapıyı oluşturmaktadırlar. KAF, Marmara Bölgesi’nde kuzey ve güney olmak üzere iki kola ayrılır. Bunlardan Marmara Denizi’nin kuzeyinden geçen kol kuzey kol, güneyinden ve inceleme alanından geçen kol ise güney koldur. İnceleme alanında kuzeyde Edincik, Kapıdağı, Bandırma-Mudanya yükselimleri, güneyde Uludağ yükselimi ve Söğütalan platosu yer alır. Bu iki yükselim alanının ortasında doğu-batı uzanımlı bir çöküntü (depresyon) alanı gelişmiştir. Bu yükselim alanları ve çöküntü alanı, neotektonik dönemde Kuzey Anadolu Fayı’nın güney kolunun etkinliği ve kontrolü ile meydana gelmişlerdir. Çöküntü alanı içerisinde ise bir çok çek-ayır biçiminde havzalar oluşmuştur. Bölgede KAF’ın güney koluna ait faylar Yenice-Gönen, Manyas-Mustafakemalpaşa, Uluabat ve Bursa faylarıdır. Sismolojik veriler bölgedeki depremlerin büyük ölçüde KAF’a ait güney kol üzerinde meydana geldiğini, hasar yapıcı ve yıkıcı depremlerin hem doğrultu atımlı hem de eğim atımlı faylar üzerinde oluştuğunu göstermektedir.Anahtar Kelimeler: Güney Marmara Bölgesi, Kuzey Anadolu Fayı, çek-ayır havza, yanal atımlı fay. In neotectonic period, North Anatolian Fault and its branches are the most active in the study area and Marmara Region. NAF is divided into two bracnhes as north and south in the Marmara Region. The northern branch is located in the north of the Sea of Marmara. The southern branch is located in study area and south of the Sea of Marmara. The South Marmara Region has ptwo uplift areas located at southern and northern margins and a depression between these uplifts. The north uplifts are Edincik, Kapıdağı and Bandırma-Mudanya, south uplifts are Uludağ uplift and Söğütalan Plateau. The uplift and depression areas are contrelled by the southern branch of the NAF in the neotectonic period. In the depression area a lot of pull-apart style basins happened. The southern branch of the North Anatolian Fault, which consists of the Yenice-Gönen, Manyas-M.Kemalpaşa, Uluabat and Bursa faults. According to seismological data of South Marmara Region, earthquakes have occured on the southern branch of the NAF and earthquakes show that the faults have not only strike-slip but also normal fault characteristics.Keywords: South Marmara Region, North Anatolian Fault, pull-apart basin, strike-slip faul
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