Browsing by Subject "Applied voltages"
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Item Open Access High-voltage optical emission in binary gaseous mixtures of N2(Elsevier, 1995) Zengin, V.; Gökmen, A.; Dinçer, S.; Süzer, Ş.Optical emission in 1:1 binary gaseous mixtures under high voltage displays a varying character depending on pressure, applied voltage polarity, and chemical nature of the mixture. Under negative polarity, in pure N2 and 50% mixture of Ar, O2 and CO2, emission stemming from N2 + is enhanced relative to emission from neutral N2. In mixtures of N2 with gases containing halogens (CCl4, CHCl3, CH2Cl2, CF3H, CF2Cl2 and SF6) a reversal is observed, i.e. the N2 + emission is suppressed. An enhancement factor is defined as the ratio of the emission under negative polarity to positive polarity to quatify this polarity dependence. This enhancement factor varies between 0.01 and 50 depending on the second component in the mixture © 1995 Elsevier Science B.V.Item Open Access Nonlinear equivalent circuit model for circular CMUTs in uncollapsed and collapsed mode(IEEE, 2012) Aydoğdu, Elif; Özgürlük, Alper; Oğuz, H. Kağan; Atalar, Abdullah; Kocabaş, Coşkun; Köymen, HayrettinAn equivalent electrical circuit model valid for collapsed mode operation of CMUT is described. The across and through variables of the circuit model are chosen to be rms force and rms displacement over the surface of the CMUT membrane. The relation between rms displacement and applied voltage is obtained through analytical calculations utilizing the exact force distribution. The radiation impedance of collapsed mode CMUT is included as a load impedance in the circuit model. The resulting equivalent circuit is merged with uncollapsed mode model, to obtain a simulation tool that covers the whole operation range of CMUT. © 2012 IEEE.Item Open Access Silicon-Germanium multi-quantum well photodetectors in the near infrared(Optical Society of American (OSA), 2012) Onaran, E.; Onbasli, M. C.; Yesilyurt, A.; Yu, H. Y.; Nayfeh, A. M.; Okyay, Ali KemalSingle crystal Silicon-Germanium multi-quantum well layers were epitaxially grown on silicon substrates. Very high quality films were achieved with high level of control utilizing recently developed MHAH epitaxial technique. MHAH growth technique facilitates the monolithic integration of photonic functionality such as modulators and photodetectors with low-cost silicon VLSI technology. Mesa structured p-i-n photodetectors were fabricated with low reverse leakage currents of ∼10 mA/cm2 and responsivity values exceeding 0.1 A/W. Moreover, the spectral responsivity of fabricated detectors can be tuned by applied voltage. © 2012 Optical Society of America.Item Open Access Simulation of an integrated microfluidic device for bioparticle wash, separation and concentration(American Society of Mechanical Engineers (ASME), 2013) Çetin, Barbaros; Büyükkoçak, S.; Zeinali, Soheila; Özer, B.Washing, separation and concentration of bioparticles are key operations for many biological and chemical analyses. In this study, the simulation of an integrated microfluidic device is studied. The proposed device has the capability to wash the bioparticles (transferring the bioparticles from one buffer solution to another), to separate the particles based on their dielectric properties and to concentrate the bioparticles. Washing and concentration of bioparticles are performed by acoustophoresis and the separation is performed by dielectrophoresis. For simulating the flow within the microchannel, a computational fluid dynamics model using COMSOL Multiphysics software is implemented. In order to simulate the particle trajectories under ultrasonic and electric field, point-particle assumption is chosen using MATLAB software. To account for the size variation of the bioparticles, particles with normal size distributions are used in-side the microchannel. The effect of the key design parameters such as flow rate, applied voltage etc. on the performance of the device is discussed. Copyright © 2013 by ASME.