Home About us Contact
|
Home About us Contact | ||
|
|
||
Polarization Characteristics (polarization + characteristic)
Selected AbstractsPolarization characteristics and property distributions of a proton exchange membrane fuel cell under cathode starvation conditionsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2010Dongsoo Ko Abstract Property distribution and polarization characteristics of a proton exchange membrane fuel cell (PEMFC) under cathode starvation conditions were investigated numerically and experimentally for a unit cell. The polarization curves of a lab-scale PEMFC were measured with increasing current density for different cell temperatures (40°C, 50°C, and 60°C) at a relative humidity of 100%. To investigate the local temperature, water content and current density on the membrane, and gas velocity in the channel of the PEMFC, numerical studies using the es-pemfc module of the commercial flow solver STAR-CD, which were matched with experimental data, were conducted. Temperature, current density on the membrane, and water content in the MEA were examined to investigate the effect of cell temperature on performance under the cathode starvation condition. At cathode starvation conditions, the performance of a higher cell temperature condition might drop significantly and the mean temperature on the membrane increase abruptly with increasing cell temperature or current density. Copyright © 2009 John Wiley & Sons, Ltd. [source] First observation of natural circular dichroism spectra in the extreme ultraviolet region using a polarizing undulator-based optical system and its polarization characteristicsJOURNAL OF SYNCHROTRON RADIATION, Issue 4 2009Masahito Tanaka Natural circular dichroism (CD) spectra in the extreme ultraviolet (EUV) region down to a wavelength of 80,nm have been observed for the first time, using an alanine thin film deposited on sodium salicylate coated glass as a sample. Calibrated EUV-CD spectra of l -alanine exhibited a large negative peak at around 120,nm and a positive CD signal below 90,nm, which were roughly predicted by theoretical calculations. A CD measurement system with an Onuki-type polarizing undulator was used to obtain the EUV-CD spectra. This CD system, the development of which took five years, can be used to observe even weak natural CD spectra. The polarization characteristics of this system were also evaluated in order to calibrate the recorded CD spectra. [source] Theoretical and experimental study of polarization characteristics of polarization maintaining fiber based on wavelength-sweeping modulationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2010Zuo-Liang Duan Abstract We analyze theoretically the polarization characteristics of polarization maintaining fiber and study the basic measurement principles of beat length and polarization extinction ratio of this kind of optical fiber. According to the dependence of the phase difference between two orthogonally polarized modes (denoted as HE and HE) transmitted in the polarization maintaining fiber on the light wavelength, we propose the wavelength-sweeping modulation method to measure the beat length and the model birefringence. Based on this technique, the beat length and polarization extinction ratio of the PANDA polarization maintaining fibers (PMFs) (provided by Yangtze Optical Fiber and Cable Company, Wuhan, China) were investigated in detail. Experimental results show good consistent with the theoretical ones. We find that this method shows high measurement precision with the advantages of clear measurement principle and easy to operate. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1466,1469, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25244 [source] RF characteristics of spaceborne antenna mesh reflecting surfaces: Application of periodic method of momentsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2005Amane Miura Abstract This paper describes a numerical-analysis methodology for RF characterization of various mesh reflecting surfaces used as the reflector surface of spaceborne antennas. Two mesh reflecting surfaces, which demonstrate different polarization characteristics, are studied. Because the mesh reflecting surface has a periodic weaving structure, periodic MoM with RWG basis and testing functions is applied, which allows only one periodic cell of mesh surface to be simulated. The analysis of transmission and reflection losses indicated that Single Satin mesh was much better than Single Atlas mesh, in terms of independence of transmission or reflection loss on polarization. This is because Single Satin mesh model has denser strips than the Single Atlas mesh model. Therefore, for any polarization direction, there is always at least one strip with its axis along or nearly along the incident electric field. The methodology and results presented in this paper are useful for accurate performance prediction of mesh reflector antennas. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 365,370, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21171 [source] Intraoperative Study of Polarization and Evoked Response Signals in Different Endocardial Electrode DesignsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 7 2001CHING LAU LAU, C., et al.: Intraoperative Study of Polarization and Evoked Response Signals in Different Endocardial Electrode Designs. Some new generation pacemakers use an algorithm based on evoked response (ER) detection to verify beat-to-beat capture and to enable automatic adjustment of output. This is a prospective acute study of polarization signal (PS) and ER in nine currently available electrodes. Intraoperative testing of ventricular bipolar electrodes used the Autocapture (AC) algorithm. The intrinsic R wave, PS, ER, acceptance of AC function, and stimulation thresholds (STs) were obtained. Ventricular electrodes were categorized as follows: titanium nitride (TiN)-coated passive and active fixation, high impedance (HI), passive fixation (VP), iridium oxide-coated titanium (IROX) (VI), and platinum helix (PH) active fixation. Acute testing was performed in 217 patients with an average age of 74.26 years, 59.6% were men with primary pacing indication-SSS (46.3%). There were no significant differences found with respect to R wave and threshold between the various electrodes. PH active-fixation electrodes had significantly higher ER and PS than other groups including the TiN-coated active-fixation electrodes. TiNcoated electrodes (active and passive fixation) had significantly lower PS than other electrodes. As a result, TiN electrodes had a significantly higher functional rate of AC (91.7%), whereas PH had the lowest rate (0%). In conclusion, (1) polarization characteristics are significantly different for commercially available ventricular electrodes, (2) certain physical features at the tissue to electrode interface like TiN coating appears to be more important in determining PS than electrode tip size and fixation method, and (3) the current algorithm for AC requires electrodes that provide low polarization for satisfactory performance. [source] Polarization properties in deep-ultraviolet AlGaN quantum wells with various substrate orientationsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2010A. Atsushi Yamaguchi Abstract It is known that emission polarization in AlGaN quantum wells (QWs) on c-plane substrates switches from in-plane polarization to c -axis polarization with increasing Al composition. This behaviour is unfavourable for light extraction from c-plane based light emitting diodes (LEDs). Previously, we proposed theoretically that this unfavourable polarization can be changed into favourable in-plane polarization by decreasing well width and/or introduction of compressive strain in c-oriented AlGaN-QWs. In this work, we have investigated the substrate orientation dependence of polarization properties in such AlGaN QWs by numerical calculation using the 6,×,6 k·p Hamiltonian. It is shown that even small inclination of c-plane substrate makes a drastic change in the polarization characteristics and that the use of the vicinal substrates as well as semipolar and nonpolar substrates could be beneficial in improving optical device performance. [source] Linear polarization in small radio sourcesASTRONOMISCHE NACHRICHTEN, Issue 5-6 2006A. Rossetti Abstract Polarimetric observations at 5 and 8.4 GHz have been performed for 3 CSS quasars. These observations are part of a programme aimed at studying the polarization characteristics of the core regions, jets, and lobes in such objects and at possibly finding of jet-cloud interactions in CSSs. The behaviour of the fractional polarization and of the observed polarization angle as a function of ,2 provides information on the density distribution of the ISM embedding the radio source, on its clumpiness and on the ordered and random components of the interstellar magnetic field. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||