Designing and manufacturing of porous spinal cages using Ti6A14V foamed metal

Thesis (Master)--Izmir Institute of Technology, Mechanical Engineering, Izmir, 2009Includes bibliographical references (leaves: 84-89)Text in English; abstract: Turkish and Englishxiv, 97 leavesOpen cell Ti6Al4V foams with varying porosities (50, 60 and 70%) were prepared at sintering temperatures between 1200 and 1350 °C using ammonium bicarbonate particles (315 - 500 .m) as space holder. Two different biomedical grade commercial, gas atomized spherical Ti6Al4V powders were used to prepare foams. Powder 1 was in size range of between 45 - 150 .m and Powder 2 in size range of between 30 - 90 .m. The foams were sintered under argon atmosphere in a tightly enclosed tube furnace. The resulting cellular structure of the foams showed bimodal pore size distribution, comprising macro pores (300 - 500 .m) and micro pores (1 - 30 .m). Compression tests of foam samples have shown that increasing sintering temperature or decreasing porosity increased the elastic modulus, yield and compressive strength and failure strain. The improvement in the mechanical properties of foams prepared using smaller size Ti6Al4V powder with bimodal particle distribution were attributed to the increased number of sintering necks and contact areas between the particles. The foam prepared with optimum porosity, pore size and mechanical properties for bone in-growth was further used to produce prototype porous spinal cages which are widely used in spinal surgery for vertebrae fixation. The geometries and size of the prototype spinal cages were determined through the measurements taken from human vertebrae. The foams for spinal cage preparation were first prepared in the form of plates and then core-drilled using water jet based on the design geometrical parameters determined for each vertebra segment

Electric Bus Selection with Multicriteria Decision Analysis for Green Transportation

Eren, Tamer/0000-0001-5282-3138; Hamurcu, Mustafa/0000-0002-6166-3946WOS:000531558100202Multicriteria decision-making tools are widely used in complex decision-making problems. There are also numerous points of decision-making in transportation. One of these decision-making points regards clean technology vehicle determination. Clean technology vehicles, such as electric buses, have some advantages compared to other technologies like internal combustion engine vehicles. Notably, electric vehicles emit zero tailpipe emissions, thereby ensuring cleaner air for cities and making these clean technologies preferable to other technologies, especially in highly populated areas for better air quality and more livable cities. In this study, we propose a multicriteria decision-making process using analytic hierarchy process (AHP) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) in the context of an electric bus in the center of Ankara. Six potential electric bus alternatives were evaluated under seven specific criteria. Overall, EV-2 electric buses outperformed other electric bus alternatives based on the chosen criteria. In addition, the stability of the results obtained under different scenarios using this method was established via sensitivity analysis

Strategic Planning Based on Sustainability for Urban Transportation: An Application to Decision-Making

Hamurcu, Mustafa/0000-0002-6166-3946; Eren, Tamer/0000-0001-5282-3138WOS:000537476200088Public transportation is one of the main goals of a developing city. This topic includes not only administrators, but also city residents and the environment, with economic, environmental, and social factors. This paper presents a multicriteria decision-making process for prioritizing alternative public transportation projects in Krkkale, considering the urban type of a developing city. It outlines three planned projects for improvement: "electric municipality bus", "light rail system", and the "modernization of existing vehicles and network optimization". In this study, we use the analytic hierarchy process and fuzzy technique for order preference by similarity to ideal situation (TOPSIS) application to prioritize transportation projects using economic, social, transportation, and environmental sub-criteria. The aim of this study is to select the most suitable project, based on sustainability, for more urban livability in Krkkale city. In the strategic decision-making process, the weights of each sustainability criteria have been determined using analytic hierarchy process (AHP). The fuzzy TOPSIS method has been applied for ranking the proposed alternative projects for Krkkale. Finally, the analytic decision process results are compared, and the electric municipality bus is selected as the best project alternative. The results of this study can not only offer a solution for current needs related to urban planning, but also ensure as a more transparent decision-making process for developing sustainability in developing cities in the near future

Processing and compression testing of Ti6Al4V foams for biomedical applications

Open cell Ti6Al4V foams (60% porosity) were prepared at sintering temperatures between 1,200 and 1,350 °C using ammonium bicarbonate particles (315–500 μm) as space holder. The resulting cellular structure of the foams showed bimodal pore size distribution, comprising macropores (300–500 μm) and micropores (1–30 μm). Compression tests have shown that increasing sintering temperature increased the elastic modulus, yield and compressive strength, and failure strain of foams. The improvements in the mechanical properties of foams prepared using smaller size Ti64 powder with bimodal particle distribution were attributed to the increased number of sintering necks and contact areas between the particles. Finally, the strength of foams sintered at 1,350 °C was found to satisfy the strength requirement for cancellous bone replacement.Technology Development Foundation of Turkey (TTGV) for the grant #TTGV-102/T1

Adaptive nonlinear hierarchical control of a quad tilt-wing UAV

Position control of a quad tilt-wing UAV via a nonlinear hierarchical adaptive control approach is presented. The hierarchy consists of two levels. In the upper level, a model reference adaptive controller creates virtual control commands so as to make the UAV follow a given desired trajectory. The virtual control inputs are then converted to desired attitude angle references which are fed to the lower level attitude controller. Lower level controller is a nonlinear adaptive controller. The overall controller is developed for the full nonlinear dynamics of the tilt-wing UAV and thus no linearization is required. In addition, since the approach is adaptive, uncertainties in the UAV dynamics can be handled. Performance of the controller is presented via simulation results

Scene creation and exploration in outdoor augmented reality

This thesis investigates Outdoor Augmented Reality (AR) especially for scene creation and exploration aspects.We decompose a scene into several components: a) Device, b) Target Object(s), c) Task, and discuss their interrelations. Based on those relations we outline use-cases and workflows. The main contribution of this thesis is providing AR oriented workflows for selected professional fields specifically for scene creation and exploration purposes, through case studies as well as analyzing the relations between AR scene components. Our contributions inlude, but not limited to: i) analysis of scene components and factoring inherintly available errors, to create a transitional hybrid tracking scheme for multiple targets, ii) a novel image-based approach that uses building block analogy for modelling and introduces volumetric and temporal labeling for annotations, iii) an evaluation of the state of the art X-Ray visualization methods as well as our proposed multi-view method. AR technology and capabilities tend to change rapidly, however we believe the relation between scene components and the practical advantages their analysis provide are valuable. Moreover, we have chosen case studies as diverse as possible in order to cover a wide range of professional field studies. We believe our research is extendible to a variety of field studies for disciplines including but not limited to: Archaeology, architecture, cultural heritage, tourism, stratigraphy, civil engineering, and urban maintenance

Prvi zabilježeni slučaj Ixodes ricinus (Acari; Ixodidae) u blavora (Pseudopus apodus; Anguidae) i studije ektoparazita u reptila od prošlosti do danas u Turskoj

Three adult European glass lizards (Pseudopus apodus Klembara) were caught in the garden of Faculty of Veterinary Medicine, Ondokuz Mayis University (Samsun, Turkey) and were observed to have a tick infestation. During macroscopic examination, tick samples were collected from the lateral groove on both sides of the lizard by using blunt-tip tweezers. All the samples were examined under the microscope and belonged to Ixodes ricinus (Linnaeus) larvae and nymphs. This is the first report of a tick species or infestation in European glass lizard. In addition, we provide a detailed review of all studies conducted to date on reptile ectoparasites in Turkey.Tri odrasla blavora (Pseudopus apodus Klembara) uhvaćena su u vrtu Veterinarskog fakulteta, Sveučilišta Ondokuz Mayis (Samsun, Turska) te je otkrivena infestacija krpeljima. Tijekom makroskopskog pregleda, uzorci su prikupljeni iz bočnog utora s obje strane guštera uporabom pincete s tupim vrhom. Tijekom stereo-mikroskopske analize otkriveno je da svi uzorci pripadaju ličinkama i nimfama Ixodes ricinus (Linnaeus). Ova studija prvi je zapis o vrsti krpelja ili infestaciji blavora. Uz to, ova studija provela je detaljnu analizu do sada provedenih studija na ektoparazitima reptila u Turskoj