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Top 20 Most Read Articles
May 2012
The 20 articles with the most full-text downloads during the month, in descending order.
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EXPERIMENTAL STUDIES ON CRYOGENIC SYSTEM FOR 22.9 KV HTS CABLE SYTEM AIP Conf. Proc. 985, pp. 1217-1224; doi:http://dx.doi.org/10.1063/1.2908476 (8 pages) Online Publication Date: 27 March 2008
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In terms of high transmission capacity with lower voltage, a high temperature superconducting (HTS) cable system is a very attractive challenge for utilities. However, the concomitant cryogenic system for the HTS cable system is one of the tantalizing problems in the operation. The reliability and maintainability of cryogenic system are the key issues to apply it to the real electric power grid. Korea Electric Power Corporation (KEPCO) is making an attempt to verify the applicability of the HTS cable system to improve the efficiency of electric power industry. Since May 2006, a 22.9-kV, 50-MVA, 3-phase, 100-m class HTS cable system with an open cooling system has been operated at the KEPCO Gochang test yard. Concurrently, another HTS cable verification test with the same electrical specification and an hybrid cooling system has been carried out by LS Cable (LSC) Ltd in close proximity to the KEPCO's HTS cable system within Gochang test yard. KEPCO conducts the operation of the open cooling system, and is evaluating the hybrid system of LSC with respect to facility performance and usability. This paper compares the cryogenic performance of both HTS cable systems and discusses cooling test results such as step response. |
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THE RESULTS OF COOLING TEST ON HTS POWER CABLE OF KEPCO AIP Conf. Proc. 985, pp. 1209-1216; doi:http://dx.doi.org/10.1063/1.2908475 (8 pages) Online Publication Date: 27 March 2008
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Due to the inherent characteristics of the superconductivity that allows large power transmission capability, much research on high-temperature superconducting (HTS) power cables has been carried out world-wide. KEPCO (Korea Electric Power Corporation) had installed a three-phase, 100-m class, HTS cable system at Gochang power test center of KEPCO that handles 22.9 kV, 1250 A, 50 MVA. The HTS cable system of KEPCO consists of two terminations, the HTS power cable, and cooling system. Sub-cooled liquid nitrogen is used for the HTS power cable coolant, providing an inlet temperature to the cable during operations from 66 K to 77 K. Circulation cooling tests at different temperatures were performed to investigate operating conditions, and heat losses under alternating-current (AC) load conditions were measured. The results of performance correlated with cooling test will be presented in this paper. |
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Unidirectional Amplification as a Mechanism for Low‐Frequency Hearing in Mammals AIP Conf. Proc. 1403, pp. 507-512; doi:http://dx.doi.org/10.1063/1.3658139 (6 pages) Online Publication Date: 7 November 2011
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Sound detection is achieved in the inner ear, or cochlea, which spatially separates frequencies. The highest frequencies are detected at the organ's base and successively lower frequencies at progressively more apical positions. Although a mechanism termed critical‐layer absorption accounts for the spatial separation of frequencies above 1 kHz, hearing at lower frequencies appears to operate by a distinct mechanism that is poorly understood. We discuss a recently proposed ratchet mechanism for spatial separation of these low frequencies. This mechanism involves the synergistic interplay of two known active processes in the mechanoreceptive hair cells—active hair‐bundle motility and membrane‐based electromotility—to implement unidirectional amplification. It thus represents a mechanical analogue of the operational amplifier in electrical engineering. The mechanism provides a general design principle for unidirectional mechanical amplification that we have also employed to construct an active microphone. |
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Heavy quark potentials derived from lattice QCD AIP Conf. Proc. 1322, pp. 298-306; doi:http://dx.doi.org/10.1063/1.3541995 (9 pages) Online Publication Date: 28 December 2010
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We compute the heavy quark potentials including relativistic corrections by using lattice QCD simulations within the quenched approximation. These results are important nonperturbative inputs of an effective field theory called potential nonrelativistic QCD, which serves for the systematic study of heavy quarkonia. Utilizing the multilevel algorithm and the transfer matrix theory, we determine the potentials at the distances ranged from 0.25 to 1.2 fm. We observe long-range nonperturbative contributions to the potentials as well as a reasonable scaling behavior with respect to the change of lattice spacing. |
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Characterization of ultra-thin oxides using electrical C-V and I-V measurements AIP Conf. Proc. 449, pp. 235-239; doi:http://dx.doi.org/10.1063/1.56801 (5 pages) Online Publication Date: 27 March 2008
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The measurement of electrical parameters from capacitance-voltage (C-V) and current-voltage (I-V) curves provides a fast means of characterizing oxides in MOS capacitors or transistor structures. For ultra-thin oxides (<2 nm), conventional, well-established techniques must be reconsidered and modified due to several increasingly important physical effects including polysilicon depletion and surface quantum mechanical effects. In this work these effects have been incorporated into a rapid analysis program for extracting ultra-thin oxide parameters from measured C-V and I-V data. The technique uses a physically based model of structure charge and potential combined with a non-linear least squares fitting technique to extract device parameters. © 1998 American Institute of Physics. |
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Evaluation of five fracture models in Taylor impact fracture AIP Conf. Proc. 1426, pp. 1125-1128; doi:http://dx.doi.org/10.1063/1.3686477 (4 pages) Online Publication Date: 29 March 2012
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Taylor impact test presented in a previous study on a commercial high strength and super hard aluminum alloy 7A04-T6 are numerically evaluated using the finite element code ABAQUS/Explicit. In the present study, the influence of fracture criterion in numerical simulations of the deformation and fracture behavior of Taylor rod has been studied. Included in the paper are a modified version of Johnson-Cook, the Cockcroft-Latham(C-L), the constant fracture strain, the maximum shear stress and the maximum principle stress fracture models. Model constants for each criterion are calibrated from material tests. The modified version of Johnson-Cook fracture criterion with the stress triaxiality cut off idea is found to give good prediction of the Taylor impact fracture behavior. However, this study will also show that the C-L fracture criterion where only one simple material test is required for calibration is found to give reasonable predictions. Unfortunately, the other three criteria are not able to repeat the experimentally obtained fracture behavior. The study indicates that the stress triaxiality cut off idea is necessary to predict the Taylor impact fracture. |
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AIP Conf. Proc. 1241, pp. 13-17; doi:http://dx.doi.org/10.1063/1.3462628 (5 pages) Online Publication Date: 28 June 2010
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This talk is largely based on the work now published in Riess et al. (2007) |
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AIP Conf. Proc. 1429, pp. 1-1; doi:http://dx.doi.org/10.1063/1.3701893 (1 page)
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Abstract Unavailable
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AIP Conf. Proc. 139, pp. 107-132; doi:http://dx.doi.org/10.1063/1.35565 (26 pages) Online Publication Date: 23 July 2008
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The suitability of using P.I.C. codes to simulate intense ion beam is discussed by presenting examples of their use. The numerical methods employed in these codes, as well as their limitations, are explained and some examples are presented to illustrate possible consequences of these limitations. |
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AIP Conf. Proc. 156, pp. 201-208; doi:http://dx.doi.org/10.1063/1.36456 (8 pages) Online Publication Date: 4 June 2008
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The possibility that muons may be used in a future generation of high‐energy high‐luminosity μ+ μ− and μ‐p colliders is presented. The problem of collecting and cooling high‐intensity muon bunches is discussed and ionization cooling is described. High‐energy collider scenarios are outlined; muon colliders may become superior to electron colliders in the multi‐TeV energy range. |
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Preface: Shock Compression of Condensed Matter - 2011 AIP Conf. Proc. 1426, pp. 1-2; doi:http://dx.doi.org/10.1063/1.3688079 (2 pages) Online Publication Date: 29 March 2012
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There is no abstract for Preface. |
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AIP Conf. Proc. 1218, pp. 207-214; doi:http://dx.doi.org/10.1063/1.3422355 (8 pages)
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NASA at the Johnson Space Center (JSC) in Houston is presently working toward modifying the original forced flow liquid nitrogen cooling system for the thermal shield in the space simulation chamber‐A in Building 32 to work as a natural flow (thermo siphon) system. Chamber A is 19.8 m (65 ft) in diameter and 35.66 m (117 ft) high. The LN2 shroud environment within the chamber is approximately 17.4 m (57 ft) in diameter and 28 m (92 ft) high. The new thermo siphon system will improve the reliability, stability of the system. Also it will reduce the operating temperature and the liquid nitrogen use to operate the system. This paper will present the requirements for the various operating modes. System level thermodynamic comparisons of the existing system to the various options studied and the final option selected will be outlined. A thermal and hydraulic analysis to validate the selected option for the conversion of the current forced flow to natural flow design will be discussed. The proposed modifications to existing system to convert to natural circulation (thermo siphon) system and the design features to help improve the operations, and maintenance of the system will be presented. |
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Jacob’s ladder of density functional approximations for the exchange-correlation energy AIP Conf. Proc. 577, pp. 1-20; doi:http://dx.doi.org/10.1063/1.1390175 (20 pages)
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The ground-state energy and density of a many-electron system are often calculated by Kohn-Sham density functional theory. We describe a ladder of approximations for the exchange-correlation energy as a functional of the electron density. At the lowest rung of this ladder, the contribution to the energy from a volume element of 3-dimensional space is determined by the local density there. Higher rungs or levels incorporate increasingly complex ingredients constructed from the density or the Kohn-Sham orbitals in or around this volume element. We identify which additional exact conditions can be satisfied at each level, and discuss the extent to which the functionals at each level may be constructed without empirical input. We also discuss the research that remains to be done at the exact-exchange level, and present our “dreams of a final theory.” “Jacob left Beer-sheba and went toward Haran. He came to a certain place and stayed there for the night, because the sun had set. Taking one of the stones of the place, he put it under his head and lay down in that place. And he dreamed that there was a ladder set up on the earth, the top of it reaching to heaven; and the angels of God were ascending and descending on it.” © 2001 American Institute of Physics. |
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Stellar polarimetry: Where are we and where are we going? AIP Conf. Proc. 1429, pp. 289-294; doi:http://dx.doi.org/10.1063/1.3701943 (6 pages)
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On the final day of the Stellar Polarimetry conference, participants split up into three "breakout sessions" to discuss the future of the field in the areas of instrumentation, upcoming opportunities, and community priorities. This contribution compiles the major recommendations arising from each breakout session. We hope that the polarimetric community will find these ideas useful as we consider how to maintain the vitality of polarimetry in the coming years. |
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Left‐right symmetry and CP‐violation AIP Conf. Proc. 102, pp. 99-106; doi:http://dx.doi.org/10.1063/1.34159 (8 pages) Online Publication Date: 29 May 2008
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A review of left‐right symmetry and its possible connection to CP‐violation is presented. We also summarize the experimental situation regarding MR, the mass scale of parity restoration and discuss the general features of quark mass matrices in these theories. |
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Study of solar wind transients using IPS AIP Conf. Proc. 471, pp. 321-324; doi:http://dx.doi.org/10.1063/1.58807 (4 pages) Online Publication Date: 10 April 2008
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Interplanetary scintillation (IPS) observations made using the Nagoya University 4 station IPS system in Japan and the Ooty Radio Telescope in India show that both the solar wind velocities and the relative scintillation indices (g-values) are enhanced during the passage of solar wind transients. We have identified a number of these events and tried to trace their origin back to the Sun. In all the cases under discussion, type II radio bursts associated with solar flares were reported by ground radio observatories, which estimated high shock velocities. Based on the time of arrival of the events, it appears that these coronal type II’s were the sources of the interplanetary disturbances (IPD’s) observed by IPS. While, it is not possible to state that there were no CME’s present during these events, it may be equally premature to conclude that no coronal type II bursts can produce interplanetary shocks, as has been stated by (1). © 1999 American Institute of Physics. |
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AIP Conf. Proc. 1426, pp. 402-405; doi:http://dx.doi.org/10.1063/1.3686303 (4 pages) Online Publication Date: 29 March 2012
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Detonator output directed into both ambient air and polymethylmethacrylate (PMMA) windows is simultaneously investigated using ultra-high speed, time-resolved imaging and photonic Doppler velocimetry (PDV) measurements. In air, one-dimensional measurements of detonator cup position are made from timeresolved image sequences and compared to time-integrated velocity curves obtained from the PDV data. The results demonstrate good agreement that validates using the two methods concurrently to measure the motion of the detonator free-surface. In PMMA windows, instantaneous shock velocities are calculated from 1-D time-resolved measurements of shock position and known velocity-Hugoniot data are utilized to map the shock velocity calculations to corresponding values of mass velocity and shock pressure. Simultaneous PDV data describing the motion of the detonator cup/PMMA interface are used to determine the mass velocity and pressure at the interface, and to compare to the mass and shock pressures calculated from the imaging data. Experimental results are in good agreement with empirical detonation- and shock-interaction calculations, as well as 1-D numerical simulations. |
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Two-dimensional imaging velocity interferometry: Technique and data analysis AIP Conf. Proc. 1426, pp. 364-367; doi:http://dx.doi.org/10.1063/1.3686294 (4 pages) Online Publication Date: 29 March 2012
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We describe the data analysis procedures for an emerging interferometric technique for measuring motion across a two-dimensional image at a moment in time, i.e. a snapshot 2d-VISAR. |
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Metalized heterogeneous detonation and dense reactive particle flow AIP Conf. Proc. 1426, pp. 27-34; doi:http://dx.doi.org/10.1063/1.3686215 (8 pages) Online Publication Date: 29 March 2012
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Metalized heterogeneous detonation and subsequent dense reactive particle flow have become a rapidly growing research area. Selected recent developments are reviewed with an emphasis on particle aspects in three parts: detonation-particle interactions, particle reaction and instability of particle dynamics. This includes the breakdown of the CJ detonation, detonation shock interaction effects on wave velocity, critical failure diameter, post-combustion and particle morphology, shocked particle reaction mechanism, critical charge diameter for particle reaction, multiple heat release laws, aerodynamic fragmentation combustion, particle dynamic instability, which leads to clustering, agglomeration and coherent jet structure, and its mechanisms through the role of stochastic particle interactions with shock waves and fluid vorticity and turbulence. These advances have laid down the fundamentals for the next stage of developments. |
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License Plate Recognition System‐Survey AIP Conf. Proc. 1324, pp. 255-260; doi:http://dx.doi.org/10.1063/1.3526208 (6 pages) Online Publication Date: 3 December 2010
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License Plate Recognition (LPR) systems commonly have framework of processing steps such as: Detection of number plate, Segmentation of plate characters and Recognition of each character. Number plate detection is a challenging task due to diversity of plate formats and environmental conditions during the image acquisition. Accuracy of character segmentation and recognition rely on the efficiency of plate detection. Various algorithms are developed for this work. Purpose of this paper is to categorize and brief them. |
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