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Conference Object Citation - Scopus: 1Piezoelectric Ultrasonic Motors Using Bulk Pzt and Utilizing Two Orthogonal Bending Modes of a Hollow Cylinder (part 2)(2005) Cagatay,S.; Uchino,K.; Koc,B.Our main objective was to design, fabricate and characterize piezoelectric ultrasonic motors for micromechatronic devices. Three different prototypes were fabricated. The stator part of the motors was composed of a composite structure; metal and piezoelectric ceramic plates. Owing to the partially square/partially circular outside surface, the stator had two degenerated bending modes that were orthogonal to each other. First stator was 10 mm in length. The outer and inner diameters were 2.4 mm and 1.6 mm, respectively. Dimensions of the second stator had been reduced by 50%. In the final design, length of the stator had reached to 4 mm and the rotor part of the motor had been changed from a solid rod to a spring. In addition, an optimization process was conducted on improving the displacement range of the stator of the piezoelectric micro-motor. When both modes were excited at a single resonance frequency, the resultant wobbling motion will provide higher displacement values, which in turn will provide higher torque.Conference Object Citation - WoS: 10Production of Anorthite From Kaolinite and Caco3 Via Colemanite(Trans Tech Publications Ltd, 2004) Mergen, A; Kayed, TS; Bilen, M; Qasrawi, AF; Gürü, MBoron oxide has been found to be useful flux for the preparation of dense anorthite ceramics (CaO.Al2O3.2SiO(2)). Inexpensive starting materials of kaolinite, calcium carbonate and silica were used for anorthite ceramic production. Colemanite (2CaO.3B(2)O(3).5H(2)O) was added into the mixtures and the effects of colemanite upon the transformation towards anorthite and on the densification were investigated between 900-1400 degreesC. Single phase anorthite ceramic formed at lower temperatures in boron containing mixtures. Boron containing powder compacts were sintered above 90% theoretical density at 1350 degreesC.Article Citation - Scopus: 15Software Quality Assurance Models in Small and Medium Organisations: a Comparison(Inderscience Publishers, 2006) Mishra,A.; Mishra,D.Presently, the majority of software development including outsourcing is carried out by small- and medium-sized software development organisations all over the world. These organisations are not capable of bearing the cost of implementing available software quality models like CMM, SPICE, ISO, etc. Therefore, there is a need to address this problem. In this paper, we have tried to compare the main characteristics, benefits, and limitations of the models for small and medium software development organisations. We believe that this effort will contribute towards the development of a standardised quality improvement model for small- and medium-sized software development organisations. Copyright © 2006 Inderscience Enterprises Ltd.Article Citation - WoS: 2Citation - Scopus: 5Scattering of Plane Waves at the Junction of Two Corrugated Half-Planes(Taylor & Francis inc, 2005) Serbest, AH; Kara, A; Lueneburg, E; Lüneburg, ErnstIn this paper, the boundary conditions given by Weinstein ( 1969) are employed to simulate two corrugated half-planes with the same slot height but different slot width. The scattering mechanism at the junction of these half-planes is investigated via the Fourier transform technique, which leads to two coupled Wiener - Hopf equations. The solution of the Wiener - Hopf system is obtained by the Daniele - Khrapkov method and some numerical results are presented about the analysis of the scattered field.Conference Object Citation - Scopus: 25Blockage/Shadowing and Polarization Measurements at 2.45ghz for Interference Evaluation Between Bluetooth and Ieee 802.11 Wlan(2001) Kara,A.; Bertoni,H.L.We present measurement results at 2.45 GHz to evaluate blockage shadowing and fading effects due to furniture and people next to terminals for short range indoor communication systems. The followings are the results: people crossing the link near to a terminal can cause fading up to 20dB which is more than furniture blockage measured of about 5-13dB depending on objects over the links, polarization coupling was also measured by using dual polarized antenna at receiving end, and coupling is higher for obstructed links, which suggests polarization diversity.Conference Object Citation - Scopus: 2Influence of Heat Treatment and Grinding Conditions on Surface Residual Stresses in the Production of Rollers(Trans Tech Publications Ltd, 2006) Güley,V.; Tekkaya,A.E.; Savaş,T.; Özhan,F.; Gueley, VolkanThe aim of this study is to investigate surface residual stresses after heat treatment and grinding processes in the production of rollers. The residual stresses were measured using the X-ray diffraction method utilizing chromium radiation, which has an average penetration depth of 5 μm incident on AISI-E52100 (100Cr6) ball bearing steel. Taguchi design of experiments (DOE) is applied to define the set of experiments for grinding, which facilitates evaluation of the individual influences of process parameters on residual stresses and also eliminates unnecessary experiments. Response of residual stresses to each parameter is evaluated with the help of the results of residual stress measurements by X-ray diffraction. In grinding with aluminum oxide wheels, it was concluded that the lower the cutting speed and the higher the workpiece speed the higher the magnitude of surface compressive residual stresses. Higher compressive stresses were measured in axial direction compared to the circumferential direction after the grinding process.Conference Object Citation - WoS: 2Influence of Heat Treatment and Grinding Conditions on Surface Residual Stresses in the Production of Rollers(Trans Tech Publications Ltd, 2006) Gueley, Volkan; Tekkaya, A. Erman; Savas, Turhan; Ozhan, FeridunThe aim of this study is to investigate surface residual stresses after heat treatment and grinding processes in the production of rollers. The residual stresses were measured using the X-ray diffraction method utilizing chromium radiation, which has an average penetration depth of 5 mu m incident on AISI-E52100 (100Cr6) ball bearing steel. Taguchi design of experiments (DOE) is applied to define the set of experiments for grinding, which facilitates evaluation of the individual influences of process parameters on residual stresses and also eliminates unnecessary experiments. Response of residual stresses to each parameter is evaluated with the help of the results of residual stress measurements by X-ray diffraction. In grinding with aluminum oxide wheels, it was concluded that the lower the cutting speed and the higher the workpiece speed the higher the magnitude of surface compressive residual stresses. Higher compressive stresses were measured in axial direction compared to the circumferential direction after the grinding process.Article Citation - WoS: 1Citation - Scopus: 3Political Instability, Public Investment and Macroeconomic Performance(Economics Bulletin, 2005) Ismihan, Mustafa; Ozkan, F. Gulcin; Department of BusinessThis paper attempts to provide a framework to explain both the lower share of current spending in large fiscal adjustments and the potential expansionary effects of fiscal contractions. We distinguish between current spending and productivity enhancing public investments and analyze the potential determinants of the policy maker's choice for the composition of overall public spending. Using this framework, we also link the overall macroeconomic performance to the public spending decisions. Our results suggest that raising current spending at the expense of public investment is associated with less favourable performance in terms of not only inflation and output but also, interestingly, future 'current' spending.Conference Object Citation - Scopus: 2Comparison of the Deep Drawability of Aluminum and Steel Using Numerical Simulation Experiments(American Institute of Physics Inc., 2005) Sönmez,C.; Tekkaya,A.E.; Gür,C.H.Sheet metal forming processes, especially deep drawing processes give diverse results by various materials. Extreme differences occur between steel sheets and aluminum sheets. The main causes of these differences are variances in micro- and macroscopic material properties, such as anisotropy. In this study, the behavior of two distinct materials, steel and aluminum alloy, during an axisymmetrical cup drawing operation has been studied numerically. For this purpose, finite element (FE) simulations of a simple cup drawing process, which was studied in the benchmarks of the NUMISHEET 2002 have been conducted using a commercial dynamic-explicit FE-analysis package. The materials analyzed have been 6111-T4 aluminum alloy and mild steel graded as deep drawing quality. Basic process parameters, which are the blank holding force and the lubrication condition, have been varied to obtain a "successful" product and the process windows for these two materials have been compared and investigated. Thickness distributions in the blank, force requirements for the process and product quality have been used for the basis of comparison. The results are also compared with an analytical model developed by Ramaekers. © 2005 American Institute of Physics.Conference Object Influence of Heat Treatment and Grinding Conditions on Surface Residual Stresses in the Production of Rollers(Trans Tech Publications Ltd, 2006) Güley,V.; Tekkaya,A.E.; Savaş,T.; Özhan,F.The aim of this study is to investigate surface residual stresses after heat treatment and grinding processes in the production of rollers. The residual stresses were measured using the X-ray diffraction method utilizing chromium radiation, which has an average penetration depth of 5 μm incident on AISI-E52100 (100Cr6) ball bearing steel. Taguchi design of experiments (DOE) is applied to define the set of experiments for grinding, which facilitates evaluation of the individual influences of process parameters on residual stresses and also eliminates unnecessary experiments. Response of residual stresses to each parameter is evaluated with the help of the results of residual stress measurements by X-ray diffraction. In grinding with aluminum oxide wheels, it was concluded that the lower the cutting speed and the higher the workpiece speed the higher the magnitude of surface compressive residual stresses. Higher compressive stresses were measured in axial direction compared to the circumferential direction after the grinding process.
