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Top 20 Most Read Articles
June 2007
The 20 articles with the most full-text downloads during the month, in descending order.
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Topic 1: Attracting Girls Into Physics AIP Conf. Proc. 628, pp. 9-12; doi:http://dx.doi.org/10.1063/1.1505270 (4 pages) Online Publication Date: 20 August 2002
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We discuss the problems in attracting girls into physics. We present some of the projects undertaken in various countries to ameliorate the problem, and we conclude with some follow‐up suggestions that can be implemented in all countries. © 2002 American Institute of Physics |
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The Complementary Teaching of Physics and Music Acoustics — The Science of Sound AIP Conf. Proc. 899, pp. 839-839; doi:http://dx.doi.org/10.1063/1.2733580 (1 page) Online Publication Date: 27 April 2007
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The results of some up‐to‐date solutions referring to teaching physics as a part of educational reform in Serbia, can be negative in a great deal to content and scope of teaching process which has existed so far. Basic course and characteristics of those solutions mean decreasing the number of classes of full‐time physics teaching. Such tendencies are unjustified for many reasons, and the basic one is that physics is the foundation of understanding not only natural science, but also art and music (optics and acoustics respectively) and physical education (statics and dynamics). As a result of all this, there is necessity to have natural lessons of physics with the teachers of subjects such as music, art and physical education. The main objective of it is to conclude one good quality teaching cycle, and make student acquire new as well as revise their knowledge in different subjects. © 2007 American Institute of Physics |
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Laser surface texturing of a heterogeneous material: control of the machining quality AIP Conf. Proc. 907, pp. 1205-1210; doi:http://dx.doi.org/10.1063/1.2729678 (6 pages) Online Publication Date: 13 April 2007
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Laser surface texturing has been recently widely used in surface manufacturing. Since 1990’s, many research have been undertaken in this field in particular with the aim of improving surface tribological performances. The resulting surface textures can be either dimples or grooves with various spatial distributions. In this study, a laser textured surface is presented based upon grooves and some dimples. The grooves can have different cross sections: semicircular, rectangular, trapezoidal and triangular. To manage the engraving process of these types of grooves and dimples, different machining strategies have been selected. The laser manufacturing machine is equipped with a galvanometric scanner which allows tilting the laser beam and machining either tilted or vertical surfaces. To characterize the laser textured surfaces, different methods have been used: a roughness profilometry, a scanning electron microscope and a non contacting optical measurements. Thanks to these techniques, some adjustments of the parameters of the CAM and the laser machine have been operated in order to obtain the desired grooves. The difficulty highlighted here is that the engraved material is heterogeneous. The interactions between the laser and the material are not the same for the graphite and the ferrite so the engraved depth is not constant. To increase the surface quality of the laser machining, a laser polishing can be realized by the introduction of an offset between the target surface and the focal point of the laser beam. © 2007 American Institute of Physics |
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Optical properties of p‐type ZnO and ZnMnO doped by N and/or As acceptors AIP Conf. Proc. 893, pp. 339-340; doi:http://dx.doi.org/10.1063/1.2729906 (2 pages) Online Publication Date: 4 May 2007
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ZnO and Zn1−xMnxO doped with N and/or As were fabricated by thermal oxidation of ZnTe or Zn1−xMnxTe films grown by MBE on different substrates. Hall effect measurements demonstrated p‐type conductivity with the high hole concentration. We were able to distinguish between the luminescence of excitons bound either to nitrogen or arsenic acceptor. We also present a magneto‐optical study of p‐type Zn1−xMnxO diluted magnetic semiconductor (DMS). Photoluminescence spectra were used to determine the “giant” Zeeman splitting and to estimate the exchange integral N0(α‐β)∼0.1eV. This is an extremely small value for a II‐VI DMS, and we discuss possible reasons for this effect. © 2007 American Institute of Physics |
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Principles of Creating Data Warehouses in Decision Support Systems of Railway Transport AIP Conf. Proc. 718, pp. 497-507; doi:http://dx.doi.org/10.1063/1.1787353 (11 pages) Online Publication Date: 26 July 2004
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The basic aspect of operation of any transport company is connected with the freight and passenger traffic. Any mistakes in the planning of any transportation process result in a considerable decrease of the efficiency of a company’s operation and of the quality of customers’ service. The search of the effective solutions of the future system functioning on the railway should be based on the forecast of a great number of economic, social and technical characteristics of transport processes. For this purpose it is necessary to create up‐to‐date Data Warehouse, which can store large amounts of information to be used for prediction. The questions of reliability and completeness of source data as well as the account of their temporal nature and the possibility of their flexible usage present the foreground of such systems. The present paper presents a new approach to creating Data Warehouses in the Decision Support Systems. © 2004 American Institute of Physics |
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AIP Conf. Proc. 907, pp. 1430-1435; doi:http://dx.doi.org/10.1063/1.2729716 (6 pages) Online Publication Date: 13 April 2007
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One of the most important problems encountered in die‐casting processes is porosity due to air entrapment in the molten metal during the injection process. The aim of this work is to study experimentally and numerically different air entrapment mechanisms that may take place during the filling of a mould cavity (with rectangular shape) in die‐casting processes. The numerical simulation of the flow in the die cavity is carried out using a CFD code (FLOW‐3D), which is based on a SIMPLE‐like approach to solve the coupling between the momentum and mass conservation equations and a Volume of Fluid (VOF) technique for treating the free surface. Also, filling visualization experiments are carried out on a test bench using water as working fluid in a transparent die model and a high‐speed camera. The die model is specifically designed and constructed to allow an easy modification of the geometrical configuration of the gate to the die cavity. The numerical and experimental results obtained for the air‐water interface evolution are compared for different inlet velocities of the fluid. The purpose is to identify the mechanisms of air entrapment during die filling. © 2007 American Institute of Physics |
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Two‐dimensional Tungsten Photonic Crystals as Thermophotovoltaic Selective Emitters AIP Conf. Proc. 890, pp. 47-55; doi:http://dx.doi.org/10.1063/1.2711719 (9 pages) Online Publication Date: 19 March 2007
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In this work we present the design, fabrication and characterization of photonic crystals (PhC) as selective thermal emitters for thermophotovoltaic (TPV) applications. The focus of our investigation is the development of thermal emitters based on two‐dimensional (2D) PhC in single‐crystal tungsten. We show that controlled periodic patterning can be used to fashion selective tungsten emitters that are well‐matched to the photovoltaic (PV) diode of the system. The simulated emittance comparison of flat single‐crystal tungsten and patterned single‐crystal tungsten indicates potential for nearly doubling the TPV system efficiency. Measured results of a fabricated prototype structure correspond well to the simulated values. The fabrication is accomplished using laser interference lithography and reactive ion etching, the benefits and parameters of which are presented. © 2007 American Institute of Physics |
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Physical Properties of Thin Film Semiconducting Materials AIP Conf. Proc. 795, pp. 196-196; doi:http://dx.doi.org/10.1063/1.2128326 (1 page) Online Publication Date: 31 October 2005
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The physics and chemistry of semiconducting materials is a continuous question of debate. We can find a large stock of well‐known properties but at the same time, many things are not understood. In recent years, porous silicon (PS‐Si), diselenide of copper and indium (CuInSe2 or CIS) and metal oxide semiconductors like tin oxide (SnO2) and zinc oxide (ZnO) have been subjected to extensive studies because of the rising interest their potential applications in fields such as electronic components, solar panels, catalysis, gas sensors, in biocompatible materials, in Li‐based batteries, in new generation of MOSFETS. Bulk structure and surface and interface properties play important roles in all of these applications. A deeper understanding of these fundamental properties would impact largely on technological application performances. In our laboratory, thin films of undoped and antimony‐doped films of tin oxide have been deposited by chemical vapor deposition. Spray pyrolysis was used for ZnO. CIS was prepared by flash evaporation or close‐space vapor transport. Some of the deposition parameters have been varied, such as substrate temperature, time of deposition (or anodization), and molar concentration of bath preparation. For some samples, thermal annealing was carried out under oxygen (or air), under nitrogen gas and under vacuum. Deposition and post‐deposition parameters are known to strongly influence film structure and electrical resistivity. We investigated the influence of film thickness and thermal annealing on structural optical and electrical properties of the films. Examination of SnO2 by x‐ray diffraction showed that the main films are polycrystalline with rutile structure. The x‐ray spectra of ZnO indicated a hexagonal wurtzite structure. Characterizations of CIS films with compositional analysis, x‐ray diffraction, scanning microscopy, spectrophotometry, and photoluminescence were carried out. © 2005 American Institute of Physics |
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AIP Conf. Proc. 628, pp. 3-8; doi:http://dx.doi.org/10.1063/1.1505269 (6 pages) Online Publication Date: 20 August 2002
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Recent Advances in Quasi‐isentropic Compression Experiments (ICE) on the Sandia Z Accelerator AIP Conf. Proc. 620, pp. 1163-1168; doi:http://dx.doi.org/10.1063/1.1483744 (6 pages) Online Publication Date: 3 July 2002
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The Z Accelerator is a pulsed power machine capable of delivering currents to loads of ∼20 MA over times of 100–300 ns. This current produces smoothly increasing, time dependant magnetic pressures that can be applied to specimens allowing quasi‐isentropes for these materials to be inferred. A new load design has been developed that allows this pressure to be uniformly applied to as many as 8 samples simultaneously. Diagnostics have recently been fielded that have resulted in an increased understanding of the magneto‐hydrodynamic effects and our confidence in the utility of this experimental configuration for EOS measurements. Efforts are also underway on Z to provide a capability for shaping the pressure profile applied to the samples which should increase useful sample thicknesses to > 1 mm by eliminating the formation of low‐level shocks. In addition to direct measurements of quai‐isentropic material response, the impulse from this loading technique has been demonstrated to launch macroscopic flyer plates to velocities of ∼21 km/s for high‐pressure Hugoniot studies. Results of ICE measurements on 6061‐T6 aluminum to ∼1 Mbar will be discussed. © 2002 American Institute of Physics |
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Morphology of Si Nanowire Grown via Solid‐Liquid‐Solid Mechanism AIP Conf. Proc. 893, pp. 47-48; doi:http://dx.doi.org/10.1063/1.2729763 (2 pages) Online Publication Date: 4 May 2007
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The silicon nanowires are synthesized from both gold nano‐particle coated silicon substrates and gold thin film deposited ones by simple heating under argon atmosphere without any additional silicon sources. The surfaces of the silicon substrates after process are densely covered with a few to tens of micrometer long nanowires in both cases. When gold nano‐particles were used as catalyst, the total diameter of nanowires is ranged from 50nm to 60nm, which is consist of silicon crystal core 10∼15nm and SiOx sheath of 20∼25nm. Especially, we observed the wedge like surface of silicon substrates after the growth of nanowires. The wedge shape and direction are determined by uneven gold film thickness, movement of gold atoms, and the crystal orientation of silicon substrate. © 2007 American Institute of Physics |
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AIP Conf. Proc. 684, pp. 481-484; doi:http://dx.doi.org/10.1063/1.1627172 (4 pages) Online Publication Date: 23 October 2003
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The performance of the Gold/Platinum (Au/Pt) thermocouple and the Platinum/Palladium (Pt/Pd) thermocouple has received considerable study and it is found that stability of these thermocouples approaches that of Standard Platinum Resistance Thermometers. However there is still some question on the uncertainties due to the different temperature profiles of the furnaces. In this paper results of the measurements on thermal emf variations by means of thermoelectric scanning are reported. Scanning is carried out in a pressure controlled heat pipe at 960 °C over 475 mm along the thermocouples. A Au/Pt thermocouple and three Pt/Pd thermocouples were tested. Pt/Pd thermocouples were subjected to 1000 hours exposure to 1200 °C in different furnaces. As the portion of thermocouple wire previously exposed to around 750 °C crossed the top of the heat‐pipe, a 0.4 K apparent temperature drop was detected. It is found that with this thermoelectric scanning method, the effect of accumulated heat treatment on the Pt/Pd thermocouple can be detected at 960 °C. For Au/Pt no such irregularity is detected, but overall a 0.02 K deviation was observed. © 2003 American Institute of Physics |
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AIP Conf. Proc. 710, pp. 1519-1526; doi:http://dx.doi.org/10.1063/1.1774846 (8 pages) Online Publication Date: 16 July 2004
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Internal irreversibility, hence entropy generation, occurs in cryocoolers due to frictional effects and heat transfer across finite temperature gradients. As these effects are finite in any real system with relative motion between a flowing fluid and the system boundaries, entropy is generated within every component in a cryocooler. The challenge for the designer is to determine, and ultimately minimize, the total rate of entropy generation for the cryocooler, i.e., the sum of all the component entropy generation rates. Of present interest are the comparative entropy generation rates of various Stirling‐class configurations for multistage cryocoolers. This includes Stirling moving displacer systems, pulse tube systems, and “hybrid” combinations of Stirling and pulse tube technologies. As is demonstrated herein, the rate of entropy generation is strongly dependent on the thermodynamic configuration of the refrigerator. Entropy generation rates in each component are affected by configuration because configuration in large part drives the thermodynamic operating conditions, in particular mass flow rate and pressure‐to‐mass flow phase angles, throughout the cryocooler. Thus regenerator friction and heat transfer losses, which tend to dominate the total rate of entropy generation in a cryocooler, are directly impacted by the method of cryocooler staging. The quantitative results of the comparison are presented together with a case study on how entropy generation can be reduced in “hybrid” systems through load shifting. © 2004 American Institute of Physics |
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AIP Conf. Proc. 908, pp. 581-588; doi:http://dx.doi.org/10.1063/1.2740873 (8 pages) Online Publication Date: 25 May 2007
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A roller straightening process is a metal forming technique to improve the geometric quality of products such as straightness and flatness. The geometrical quality can be enhanced by eliminating unnecessary deformations produced during upstream manufacturing processes and minimizing any detrimental internal stress during the roller straightening process. The quality of steel cords can be achieved by the roller straightening depends the process parameters. Such process parameters are the roll intermesh, the roll pitch, the diameter of rolls, the number of rolls and the applied tension. This paper is concerned with the design optimization of the roller straightening process for steel cords with the aid of elasto‐plastic finite element analysis. Effects of the process parameters on the straightness of the steel cord are investigated by the finite element analysis. Based on the analysis results, the optimization of the roller straightening process is performed by the response surface method. The roller straightening process using optimum design parameters is carried out in order to confirm the quality of the final products. © 2007 American Institute of Physics |
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Manipulating molecules with intense lasers AIP Conf. Proc. 500, pp. 3-22; doi:http://dx.doi.org/10.1063/1.1302638 (20 pages)
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Molecules exposed to intense, sub-picosecond laser fields exhibit phenomena such as above threshold ionization, high harmonic generation, bond softening, bond hardening (vibrational trapping) and alignment. They can be deflected, accelerated, focused, trapped and spun. More generally, one can manipulate the outcome of a uni-or bimolecular reaction by the coherent superposition of two or more lasers (coherent control) or by using a sequence of ultrashort laser pulses. This article will take a brief and necessarily limited look at some of these methods of molecular manipulation. © 2000 American Institute of Physics. |
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Topic 6: Balancing Family and Career AIP Conf. Proc. 628, pp. 29-32; doi:http://dx.doi.org/10.1063/1.1505275 (4 pages) Online Publication Date: 20 August 2002
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The considerable challenges involved in balancing family and career have been identified as critical factors in the underrepresentation of women in physics worldwide. We review what were seen in discussion groups at the International Conference on Women in Physics to be the dominant issues for balancing family and career. We summarize the discussions and possible solutions (when possible solutions were found). © 2002 American Institute of Physics |
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Influence of Substrate Nature and Annealing on Electro‐Optical Properties of ZnO Thin Films AIP Conf. Proc. 899, pp. 253-254; doi:http://dx.doi.org/10.1063/1.2733132 (2 pages) Online Publication Date: 27 April 2007
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ZnO thin films were grown on different substrates (glass, quartz, silicon wafers, etc) by vacuum thermal evaporation. Different thermal treatments were performed in order to obtain transparent and conductive or high resistive ZnO tin films. The optical and electrical properties of ZnO thin films are dependent on the crucible temperature, annealing conditions and on the substrate nature. The thin films are transparent and have an electrical resistivity in 10−4 Ωm regio. The annealing process performed in vacuum at 573K or under UV irradiation determines a decrease in the electrical resistivity of films. © 2007 American Institute of Physics |
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Metal‐Semiconductor‐Metal Photodiode Ultraviolet Detector Based on High Quality ZnO AIP Conf. Proc. 893, pp. 1421-1422; doi:http://dx.doi.org/10.1063/1.2730438 (2 pages) Online Publication Date: 4 May 2007
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We present mechanism studies of a new metal‐semiconductor‐metal photodiode ultraviolet detector based on high quality ZnO. The detector structure consists of fringe‐type Schottky contacts between high quality n‐type ZnO and Ti or Au metals. High photoresponsivity has been observed at wavelengths above the band edge, which is explained by the generation and trapping of holes near the surface of ZnO. High rejection in the visible makes the device a potential candidate for visible‐blind UV detectors. © 2007 American Institute of Physics |
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AIP Conf. Proc. 642, pp. 108-110; doi:http://dx.doi.org/10.1063/1.1522598 (3 pages) Online Publication Date: 11 November 2002
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Within the halo experiment conducted at the Low Energy Demonstration Accelerator (LEDA) at Los Alamos National Laboratory, specific beam instruments that acquire horizontally and vertically projected particle‐density distributions out to approximately 105:1 dynamic range are located throughout the 52‐magnet halo lattice. We measure the core of the distributions using traditional wire scanners, and the tails of the distribution using water‐cooled graphite scraping devices. The wire scanner and halo scrapers are mounted on the same moving frame whose location is controlled with stepper motors. A sequence within the Experimental Physics and Industrial Control System (EPICS) software communicates with a National Instruments LabVIEW virtual instrument to control the motion and location of the scanner/scraper assembly. Secondary electrons from the wire scanner 0.033‐mm carbon wire and protons impinging on the scraper are both detected with a lossy‐integrator electronic circuit. Algorithms implemented within EPICS and in Research System’s Interactive Data Language subroutines analyze and plot the acquired distributions. This paper describes this beam profile instrument and describes our experience with its operation. © 2002 American Institute of Physics |
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Proposed Profile Monitor Designs for the Advanced Hydrodynamic Facility (AHF) AIP Conf. Proc. 648, pp. 275-282; doi:http://dx.doi.org/10.1063/1.1524410 (8 pages) Online Publication Date: 26 November 2002
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The AHF consists of a LINAC, a booster ring, a 50 GeV Synchrotron and an elaborate set of beam‐lines for simultaneously delivering a string of 24 proton bunches from 12 different directions to a firing site (fs) chamber in which an explosion is in progress. This paper will discuss profile instrumentation being considered for the fs beam‐lines and the Synchrotron. In the beam‐lines most profiling devices will probably be harps but some fluorescent screen/camera systems may be used. For the Synchrotron RGIPM’s may be used for observing individual bunches. The MCP usually placed in the vacuum for such devices might be replaced by a scintillator viewed by a lens plus multianode PMT. In order to observe individual bunches, it may be necessary to increase the local vacuum pressure using a gas jet, molecular beam or a gas puff. Another option may be to view gas fluorescence with the same optical arrangement as used for the RGIPM. A carbon wire moving with velocities of 1 to 5 m/s is being considered as an intercepting device to observe stored beams consisting of one or two bunches. A quadrupole moment measuring system for determining transverse emittance is being investigated. © 2002 American Institute of Physics |
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GBR - Devon
Chair and Lecturer (2 posts)
Sandia National Laboratories
US - NM - Albuquerque
Post Doc – Nuclear/ Nanoparticle Materials
Syracuse University
US - NY - Syracuse
Postdoc in Experimental CM Physics
University of Rochester
US - NY - Rochester
Biomedical Optics
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