WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7150

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1994 - 199972000 - 2009160

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End date: 2009Department: search.filters.department.İzmir Institute of Technology. Mechanical Engineering

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Now showing 1 - 10 of 167
  • Conference Object
    Problem of Cracked Infinite Hollow Cylinder With Two Rigid Inclusions
    (Civil-Comp Press, 2000) Artem, Hatice Seçil; Geçit, Mehmet Ruşen
    This paper is concerned with the fracture of an axisymmetric hollow cylindrical bar containing rigid inclusions. The cylinder is under the action of uniformly distributed axial tension applied at infinity. The hollow cylinder contains a ring-shaped crack at the symmetry plane whose surfaces are free of tractions and two ring-shaped rigid inclusions with negligible thickness symmetrically located on both sides of the crack. Geometry and the loading is symmetric about z-axis. Along the rigid inclusions displacements are constant and continuous whereas stresses have jumps. The inner and the outer surfaces of the cylinder are free of tractions It is assumed that the material of the cylinder is linearly elastic and isotropic. The mixed boundary conditions of the problem lead the analysis to a system of three singular integral equations for crack surface displacement derivative and normal and shear stress jumps on rigid inclusions. These integral equations are solved numerically and the stress intensity factors at the edges of the crack and at the edges of the inclusions are calculated. Results are presented in graphical form.
  • Conference Object
    Kinematic and Dynamic Analysis of a New Type of Spatial 6-Dof Parallel Structure Manipulator
    (China Machine Press, 2004) Alizade, Rasim; Bayram, Çağdaş
    This paper addresses the dynamics and kinematics of a 6xUPS type parallel structure manipulator that consists of six branches and a platform. The problem of forward and inverse displacement analysis is considered on the base of solution of the forward displacement problem for each UPS branch as a serial manipulator. Basic dynamics equations have also been considered. The values of reduced moments and forces have been determined that provides the required input forces and moments. Thus, we deal with inverse dynamics problems. Dynamic model of this type of spatial manipulator is described by a system of six non-linear differential equations of second order with applying Lagrange-Euler methods.
  • Conference Object
    Citation - WoS: 7
    Modeling of Low Temperature Geothermal District Heating Systems
    (Taylor and Francis Ltd., 2004) Yıldırım, Nurdan; Gökçen, Gülden
    In this work, low temperature geothermal district heating systems with heat pumps have been studied and compared with fuel-oil boiler heating systems for intermittent and continuous regimes according to the optimum indoor air temperature and operational cost. Izmir Institute of Technology (IZTECH) Campus is taken as a case study. Various heat pump and boiler configurations are studied to meet required duty. Operational cost analysis for each alternative is conducted. According to the results, for IZTECH Campus the best alternative, which gives the optimum indoor air temperature and the lowest operational cost, is heat pump continuous regime.
  • Conference Object
    Heat Load Factor for Geothermal District Heating System Design
    (National Technical University of Athens, 2006) Yıldırım, Nurdan; Gökçen, Gülden
    Design of heating systems using conventional fuels is based on peak load which is calculated according to the coldest outdoor design temperature. But in geothermal district heating system design it is common practice to use a heat load factor between 0.6-0.7 since the resource is continues, cheap and system can be run for 24 hours a day. Heat load factor can be defined as a ratio of actual heat load to design heat load of the system. In this study, a geothermal district heating system is designed for Izmir Institute of Technology Campus, Izmir, Turkey and simulated for a heat load factor range of 0.5-1. For the Campus case, the heat load factor is determined as 0.53-0.0.67 based on indoor air temperature and operational cost.
  • Conference Object
    Cash Flow Forecasting by Using Time Series Methods in Geothermal District Heating Systems: Balcova - Narlidere Case
    (National Technical University of Athens, 2006) Erdoğmuş, Abdullah Berkan; Özerdem, Barış
    Cash flow forecasting is one of the difficult and important tasks in an economic evaluation of a geothermal investment. Geothermal district heating systems are characterized by a high capital cost. In addition, relatively low operation and maintenance costs occur throughout their life. The aim of this research is to estimate the potential cash flows for Balcova - Narlidere Geothermal District Heating System by using historical data accumulated over a period of time and several forecasting methods: moving average, exponential smoothing, adjusted exponential smoothing and curve fitting functions. Mean absolute percentage deviation (MAPD) which is the most common approach to select the appropriate method to a particular time series is used in the selection of the most suitable model. Alternative methods are compared with each other regarding to their MAPD values. It is found that the models represented by exponential curve fitting functions have smaller MAPD values and give better results in cash flow forecasting of investment investigated.
  • Conference Object
    Tıbbi Uygulamalar için Özgün Yapılı Haptik Cihaz Tasarımı
    (Institute of Electrical and Electronics Engineers Inc., 2009) Selvi, Özgün; Bilgincan, Tunç; Kant, Yalkın; Dede, Mehmet İsmet Can
    Robotik sistemler hassasiyet gerektiren işlerde gün geçtilçe günlük hayatımızın bir parçası olmaya başladı. Bu işler genellikle herhangi bir operatör tarafından yapılamayacak kadar hassasiyet gerektiren işler olduğundan dolayı robotik teknolojiye ihtiyaç vardır. Bir robotik alanı olan Haptik teknolojisi, operatör ile çevrenin etkileşimini kuvvet geri beslemesi ile sağlayarak uygulamanın hassasiyet seviyesini arttırmaktadır. Bugünkü haliyle haptik teknoloji tıbbi operasyonlarda yardımcı sistem olarak ve birçok uzaktan kumandalı operasyonlarında (teleoperasyon) kullanılmaktadır. Aynı zamanda haptik teknoloji askeri ve tıbbi eğitim amaçlı sanal gerçeklik programlarında kullanılmaktadır. Bu çalışmanın amacı sistemin hassasiyetini arttırabilecek yapısal olarak yeni bir haptik cihaz tasarlamaktır. Bu kapsamda, önceden gerçekleştirilmiş robot tasarımları araştırıldı ve kavramsal tasarımlar gelistirildi. Sonuç olarak seçilen tasarım sanal ortam da oluşturuldu ve simülasyonu yapıldı, ve ilk prototipi imal edildi
  • Article
    Citation - WoS: 4
    Citation - Scopus: 3
    A new hybrid CVT design: CVPSTs
    (Inderscience Enterprises Ltd., 2002) Özdemir, Serhan; Schueller, John
    Automotive transmissions match the speed and the torque of the power source to the speed and torque requirements of the load. Properly designed continuously variable transmissions (CVTs) have shown promise to improve efficiency and performance. This work discusses some existing CVTs and proposes a new hybrid continuously variable power split transmission (CVPST). The speed relationships are analysed in power split and power recirculation mechanisms, the problem of geared neutral phenomenon with recirculating transmissions are identified and these two separate issues are left out as a topic for another paper. A new 'all-in-one' CVPST transmission incorporating power split and power recirculation is proposed.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 1
    ANN model predicts floor tile properties
    (American Ceramic Society, 2004) Akkurt, Sedat; Özcan, Selçuk
    [No abstract available]
  • Article
    Citation - WoS: 56
    Citation - Scopus: 63
    Processing, Characterization and Photocatalytic Properties of Cu Doped Tio2 Thin Films on Glass Substrate by Sol-Gel Technique
    (Elsevier Ltd., 2006) Çelik, Erdal; Gökçen, Z.; Azem, N. Funda Ak; Tanoğlu, Metin; Emrullahoğlu, O. F.
    The present paper describes processing, properties and photocatalytic application of Cu doped TiO2 thin films on glass substrate. Cu doped TiO2 coatings were successfully prepared on glass slide substrates using sol-gel method. The obtained solutions exhibit acidic characteristics. The phase structure, thermal, microstructure and surface properties of the coatings were characterized by using XRD, DTA/TG, SEM and AFM. Their adhesion properties and spectroscopic analysis were investigated by a scratch tester and UV-vis spectroscopy. Four different solutions were prepared by changing Cu/Ti ratios. Glass substrates were coated by solutions of Ti-alkoxide, Cu-chloride, glacial acetic acid and isopropanol. The obtained gel films were dried at 300 degrees C for 10 min and subsequently heat-treated at 500 degrees C for 5 min in air. The oxide thin films were annealed at 600 degrees C for 60min in air. TiO2, CuO, Cu4Ti, Ti3O5 and Cu3TiO4 phases were found in the coating. The organic matters were burned at temperatures between 200 and 350 degrees C and TiO2 crystallization was formed at 450 degrees C. The weight loss of the powder during process up to 600 degrees C is approximately 70%. The microstructural observations demonstrated that CuO content was led an improved surface morphology while thickness of the film and surface defects were increased in accordance with number of dipping. According to AFM results, it was found that as the Cu/Ti content increases the surface roughness of the films increases. In addition structural, thermal and microstructural results, it was found that the films of 0.73 ratio have better adhesion strength to the glass substrate among other coatings. The oxide films were found to be active for photocatalytic decomposition of metylene blue. (c) 2006 Published by Elsevier B.V.
  • Article
    Citation - WoS: 171
    Characteristics of Brick Used as Aggregate in Historic Brick-Lime Mortars and Plasters
    (Elsevier Ltd., 2006) Böke, Hasan; Akkurt, Sedat; İpekoğlu, Başak; Uğurlu, Elif
    Mortars and plasters composed of a mixture of brick powder and lime have been used since ancient times due to their hydraulic properties. In this study, raw material compositions, basic physical, mineralogical, microstructural and hydraulic properties of some historic Ottoman Bath brick-lime mortars and plasters were determined by XRD, SEM-EDS, AFM, TGA and chemical analyses. The mineralogical and chemical compositions, microstructures, morphologies and pozzolanicities of the brick powders and fragments used as aggregates in the mortars and plasters were examined to find out the relationship between hydraulic properties of the mortars and the bricks. The characteristics of bricks used in the bath domes were also determined to investigate whether the brick aggregates used in mortar and plasters were prepared from these bricks. The results indicated that the mortars and plasters were hydraulic owing to the presence of crushed brick powders that have good pozzolanicity. The brick powders bad high pozzolanicity because they contained high amounts of calcium-poor clay minerals in their raw materials that were fired at low temperatures. On the other hand, bricks used in the domes had poor pozzolanicity with different mineralogical and chemical compositions from bricks used in mortars and plasters. Based on the results of the analysis, it was thought that the bricks manufactured with high amounts of clays were consciously chosen in the preparation of hydraulic mortars and plasters. (C) 2006 Elsevier Ltd. All rights reserved.