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Yayın Thermally assisted OSL from deep traps in Al2O3:C(Pergamon-Elsevier Science Ltd, 2010-03) Polymeris, George S.; Raptis, Spyridoula; Afouxenidis, Dimitrios; Tsirliganis, Nestor C.; Kitis, GeorgeThe present work suggests an alternative experimental method in order to not only measure the signal of the deep traps in Al2O3:C without heating the sample to temperatures greater than 500 degrees C, but also use this signal for high dose level dosimetry purposes as well. This method consists of photo transfer OSL measurements performed at elevated temperatures using the blue LEDs (470 nm, FWHM 20 nm) housed at commercial Riso TL/OSL systems, after the sample was previously heated up to 500 degrees C in order to empty its main TL dosimetric trap. The influence of this procedure on specific features such as glow curve shape and sensitivity of the main TL glow peak was also studied.Yayın Experimental analysis on drilling of Al/Ti/CFRP hybrid composites(Bellwether Publishing, 2021-01-25) Kayihan, Mete; Karagüzel, Umut; Bakkal, MustafaCarbon fiber reinforced composites (CFRP) have superior mechanical properties such as high strength/density ratio, and good damping ability. CFRP which is frequently used in parts in the aviation industry can also be single or stacked together with titanium and aluminum alloys. However, delamination could occur on the CFRP surfaces after drilling which leads to deterioration in mechanical properties. Therefore, in this paper, the effect of process parameters and stack order on cutting force, torque are investigated. The tests were carried out at three different drilling speeds and feed rates on a CNC vertical machine tool by using a solid carbide cutting tool. The results of hole quality indicate that the process outputs are significantly affected by process parameters and stack order. The force and torque values obtained at high drilling speeds and low feed rates are independent of the stack order. However, the stacking order is determined to be the most effective parameter for the thrust force and torque values. The force generated during the Ti/CFRP/Al stack in which the highest force value is approximately 50% higher than the lowest force which occurs on Al/Ti/CFRP stack. The surface roughness value measured during the Al/Ti/CFRP stack is approximately half of the other stack order.Yayın Multiple annular ring capacitive micromachined ultrasonic transducer arrays for forward-looking intravascular ultrasound imaging catheters(American Society of Mechanical Engineers (ASME), 2007) Güldiken, Rasim Oytun; Zahorian, Jaime S.; Balantekin, Müjdat; Karaman, Mustafa; Değertekin, Fahrettin LeventWe investigate multiple-annular-ring CMUT array configuration for forward-looking intravascular ultrasound (FL-IVUS) imaging. This configuration has the potential for independent optimization of each ring and uses the silicon area more effectively without any particular drawback. We designed and fabricated a sample 1mm diameter dual annular ring CMUT test array which consists of 24 transmit and 32 receive elements. For imaging experiments, we designed IC chips that contain 8 transimpedance amplifiers, a multiplexer and a buffer. The real time-pulse echo experiments obtained with designed IC electronics show 26dB Signal to Noise Ratio (SNR) from a 3.5 mm away aluminum reflector in oil. This paper presents our first efforts in obtaining real time imaging with designed IC chips which is one step before CMUT on CMOS implementation.Yayın A model of AlN layer formation during ion nitriding of Al(Springer-Verlag, 2004-11) Dimitrov, Ventzislav IvanovA diffusion model of AlN layer formation by ion nitriding of Al is proposed based on the analysis of atomic transport during the process. This model is reduced to the following. Implantation of N ions to the surface of the specimen, named the reaction zone; extraction of Al from the substrate; diffusion transport of Al to the reaction zone through an AlN layer formed during the process; formation and growth of AlN in the reaction zone; sputtering of the AlN layer. Equations controlling the growth process have been obtained.
