bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of spin‐flip tunneling on temperature and voltage dependence of TMR
Authors: Takada I. , Ozeki J. , Itoh H. , Inoue J. 
Published: December 2007

AbstractWe study the temperature and voltage dependence of the tunnel magnetoresistance (TMR) using a phenomenological theory which takes into account the spin‐flip tunneling. We show that the temperature dependence becomes strong when the spin‐flip tunneling exists. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inhomogeneous spin accumulation in Py/Au/Py spin valve
Authors: Ku Jang Hae , Chang Joonyeon , Eom Jonghwa , Koo Hyuncheol , Han Suk‐Hee , Kim Gyutae 
Published: December 2007

AbstractWe present that inhomogeneous spin accumulation in a Py/Au/Py spin valve is due to the formation of an edge point contact at the interface. Nonlocal measurements with different voltage probe configurations were carried out to understand the effect of probe location on the spin signal. The spin signal is strongly affected by the probe configuration because of inhomogeneous spin current distribution in the channel as well as different channel length depending on the probe position. Inhomogeneous spin accumulation initiating from the point contact induces the different distribution of spin accumulation flowing into a detector. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The contribution of the exchange biased field direction in multilayer thin films to planar Hall resistance
Authors: Hung Tran Quang , Quang Pham Hong , Thanh Nguyen Trung , Sunjong Oh , Bajaj Bharat , CheolGi Kim 
Published: December 2007

AbstractRecently, planar Hall effect (PHE) has been widely pursued due to its application potential for biosensors. Planar Hall sensor is based on the anisotropy magnetoresistance and exhibits many advantages, such as large signal‐to‐noise ratio at low frequencies and high sensitivity at low applied field. The planar Hall resistance (PHR) curve in multilayer thin films with spinvalve structure has pre‐eminent sensitivity when compared to single layer and bilayer thin films. In this work, we report a model for PHR calculation that includes the behaviour of single domain basic structure in the external magnetic field. Our results show a qualitative dependence between PHR curves and the angle (β) between the exchange biased field direction and the easy axis of the free layer. As the β increases the sensitivity of the PHR curves also increases. Further, it is shown that our calculation helps to determine the exchange biased field direction. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hopping conduction behavior with the Coulomb effects in colossal magnetoresistance materials
Authors: Lin C. H. , Young S. L. , Chen H. Z. , Kao M. C. , Horng Lance 
Published: December 2007

AbstractWe report on the temperature dependence of resistivity in La0.7–xPrxPb0.3MnO3 (x =0, 0.5, 0.7) bulk samples in order to explore the hopping transport behavior with the Coulomb effects for the colossal magnetoresistance materials. The experimental observations in La0.7–xPrxPb0.3MnO3 (x =0.5, 0.7) bulk samples reveal the exponential temperature dependence of resistivity ϱ (T) ∞ exp [(T1/T)n ] with n = 1/2, when system was the paramagnetic (PM) insulator at the high temperature range (T>Tp). Evidence for the hopping conduction with Coulomb effects is presented By using the approximate method of the VRH conduction in the localization regime base on Efros and Shklovskii model [A. L. Efros and B. I. Shklovskii, J. Phys. C, Solid State Phys. 8, L49 (1975)], the localization length of eg electrons can be estimated with the relationship, ξ=2.8e2/(4πε0κkBT1). The reasonable results of localization length can be evaluated to explain the possibility of the presence of the Coulomb interactions in these CMR materials. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A first‐principles study of electronic structures and magnetism for a Mn2As(001) surface
Authors: Jin Y. J. , Lee J. I. 
Published: December 2007

AbstractThe electronic structures and magnetic properties of Mn‐terminated Mn2As (001) surfaces were investigated by using the full‐potential linearized augmented plane wave method within the generalized gradient approximation. We considered three different types of Mn‐terminated Mn2As(001) surfaces, i.e., Mn(I)‐term, Mn(II)1‐term, and Mn(II)2‐term. The calculated results showed that the magnetic moment of the surface Mn(II) atom in the Mn(II)1‐term was greatly increased to 4.46 μB which was close to that of the free Mn atom. Those of the surface Mn(I) atom in the Mn(I)‐term and the surface Mn(II) atom in the Mn(II)2‐term were also considerably enhanced to 3.38 and 3.77μB compared with the center (1.97μB) and deep inner (3.23μB) layers, respectively. These results were discussed in relation with the band narrowing at the surfaces and the hybridization between the Mn‐d and As‐p states using the calculated spin polarized layer projected density of states. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quasi‐two‐dimensional superconductivity in wurtzite‐structured InN films
Authors: Ling D. C. , Cheng J. H. , Lo Y. Y. , Du C. H. , Chiu A. P. , Chang C. A. , Chang P. H. 
Published: December 2007

AbstractC‐axis oriented InN films with wurtzite structure were grown on sapphire (0001) substrate by MOCVD method. Superconductivity with transition onset temperature Tc,onset around 3.5 K has been characterized by magnetotransport measurements in fields up to 9 Tesla for films with carrier concentration in the range of 1×1019 cm–3 to 7×1020 cm–3. Among them, the film with a nitridation buffer layer has the highest zero‐resistance temperature Tc0 of 2 K. The normal‐state magnetoresistance follows Kohler's rule ΔR /R ∝ (H /R)2, indicating that there is a single species of charge carrier with single scattering time at all points on the Fermi surface. The extrapolated value of zero‐temperature upper critical field Hc 2ab (0) and Hc 2c (0) is estimated to be 5900 G and 2800 G, respectively, giving rise to the anisotropy parameter γ about 2.1. The angular dependence of the upper critical field is in good agreement with the behavior predicted by Lawrence‐Doniach model in the two‐dimensional (2D) limit strongly suggesting that the InN film is a quasi‐2D superconductor. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Observation of room temperature magnetoresistance in a lateral ferromagnet–semiconductor structure
Authors: Koo Hyun Cheol , Kwon Jae Hyun , Eom Jonghwa , Chang Joonyeon , Han Suk‐Hee 
Published: December 2007

AbstractFor an efficient spin‐transport in a two‐dimensional electron gas system, control of ferromagnet–semiconductor interface resistance is a very crucial factor and the clear spin‐signal is detected in the range of 4 ∼ 50 Ω μm2 in our experiments. The magnetoresistance of the local spin‐valve measurement slowly reduces with increasing temperature, but ΔR /R remains near 1% at room temperature. Based on the experimental results and calculations, our InAs channel system shows strong possibility for a spin transistor application. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical absorption spectra of Fe2+ and Fe3+ in beryl crystals
Authors: Spinolo G. , Fontana I. , Galli A. 
Published: December 2007

AbstractThe cover picture of this issue relates to the article by G. Spinolo et al. on optical absorption spectra of Fe ions in beryl crystals [1]. It shows the low temperature polarized light absorption spectrum of a gem‐quality natural aquamarine, i.e. an iron rich beryl. The relevant achievement is that satisfactory attributions of the numerous peaks of the spectrum may be obtained only assuming that both Fe2+ and Fe3+ are substituted for Al in an octahedral oxygen environment. This result excludes the possibility, proposed by several authors, of alternative locations (tetrahedral or “channel“ sites) for iron in beryl. The paper also discusses the ligand‐to‐metal (probably Fe3+) charge transfer spectrum which was measured in beryl for the first time.The corresponding author Giorgio Spinolo is a Professor of Physics at Milano–Bicocca University, Italy. After early studies on color centers in alkali halides, he became interested in intrinsic optical properties of transition metal halides and later in silica for electronic and photonic applications. Nowadays, his research is devoted to promote a solid state physics approach to study minerals of gemological interest. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nanoparticle semiconductor compositions in the miscibility gap
Authors: Jesser W. A. , Schamp C. T. 
Published: December 2007

AbstractWhen semiconductor alloys are used to engineer devices one may not be able to achieve compositions that could provide desirable properties such as a specific band gap because there exists an immiscibility of the alloys, particularly when compound semiconductors are involved. Bulk phase diagrams are used to predict the solubility limits as a function of temperature and modification of these limits can be achieved through strain of the alloy. Metastable alloys that are single phase can be prepared with compositions in the miscibility gap but these kinetically trapped alloys return to their equilibrium two‐phase state at elevated temperatures. An alternative approach to achieve compositions in the bulk miscibility gap is to prepare samples as nanoparticles with high surface curvature. These individual nanoparticles exhibit phase diagrams considerably different from those of the bulk and do not transform into a two‐phase state as long as the nanoparticles remain isolated. The purpose of this article is to show how phase diagrams in general can be expected to change with decreasing size and how the GaAs‐GaSb alloy in particular experiences changes from bulk behaviour when it is in the form of isolated nanoparticles with high surface curvature. In this paper is presented experimental characterization of GaAs‐GaSb alloy nanoparticles that are prepared by pulsed laser deposition and equilibrated in vacuum and analyzed in an analytical transmission electron microscope to show that compositions can be achieved in the bulk miscibility gap provided the nanoparticles are smaller than about 10 nm across. Further, the lattice parameter of nanoparticle alloys as a function of composition were found to deviate from Vegard's law by several percent in a positive sense, contrary to that for bulk alloys which show a deviation of a negative sign. Finally, the diffusivity of As in GaAsSb was estimated to be 1018 cm2/s, which is several orders of magnitude larger that known for bulk alloys. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural and optical characterization of single‐phase CuIn(Se,S)2 thin films deposited using a two‐step process
Authors: Sheppard C. J. , Alberts V. , Botha J. R. 
Published: December 2007

AbstractCuInSe2 has a band gap of about 1.0 eV, which limits the conversion efficiency of complete CuInSe2/CdS/ZnO devices. In order to increase the conversion efficiency of devices, it is necessary to increase the band gap value of the absorber films to about 1.2 eV. This can be achieved by systematically substituting some indium with a group III element and/or selenium with another group VI elements. The substitution of In and/or Se results in a shrinkage of the lattice parameters and thus an increase in the band gap value of the absorber films. However, this process is extremely complicated, especially for conventional two‐step growth processes in which metallic alloys are exposed to Se and/or S species. In this contribution, the optical and structural properties of homogeneous single‐phase CuIn(Se,S)2 alloys are demonstrated for the novel two‐step deposition process. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A portfolio approach to maintenance: a case study of a residential estate
Authors: Chu L. K. , Leung A. K. Y. , Sculli D. 
Published: December 2007

AbstractThe choice between repairing and replacing a defective piece of equipment is an economic decision that is faced by all maintenance managers, including housing estate managers. Such decisions need to be made within the limits and constraints set by maintenance expenditure budgets and by manpower availability. Our particular problem is concerned with the development of a maintenance policy for a residential estate of the Hong Kong Housing Authority. Our approach is to treat the numerous housing systems as a portfolio and to exploit flexibilities in performing or delaying the repair/replacement of these systems. The cost of a repair/replacement plan for the portfolio is formulated as an integer programme and genetic algorithms (GAs) are employed to generate optimal and sub‐optimal solution plans. The novel features of the approach are the model developed and use of GAs in this particular optimization context. The results and discussion of the case study will help practitioners to better understand the difficulties involved in collecting relevant cost data and in formulating repair/replacement plans for a group of buildings. Copyright © 2007 John Wiley & Sons, Ltd.
Warning procedures for systems that are improving
Authors: García‐Escudero Luis A. , Fernández Miguel A. , Duque Oscar , Zorita Angel L. 
Published: December 2007

AbstractNowadays it is quite usual that systems are correctly maintained. This leads to a decreasing number of failures for the system. In this paper we discuss how to establish warning procedures that take into account features giving the chance of detecting eventual changes of trend in the systems and allowing taking measures before too much damage has actually happened. The proposed procedure is applied to the study of the reliability and maintenance of the railway electric supply system. In this kind of systems, complex and extended, testing the performance of the system and effectiveness of the maintenance tasks has special interest. Copyright © 2007 John Wiley & Sons, Ltd.
Evaluation of boldenone formation and related steroids transformations in veal faeces by liquid chromatography/tandem mass spectrometry
Authors: Arioli Francesco , Gavinelli Matteo P. , Fracchiolla Maria L. , Casati Alessio , Fidani Marco , Ferrer Emilia , Pompa Giuseppe 
Published: December 2007

AbstractIt is established that bovine urine can result positive for boldenone and androstadienedione in consequence of faecal contamination. The simple transfer of steroids to urine is one minor aspect of faecal contamination. A high de novo production of steroids in faeces after deposition and in faeces‐contaminated urine is almost certainly due to microbial activity, although the precursor compounds and transformations leading to the presence of these illegal steroids are unclear. We developed a simple in vitro method – incubation of faecal matter suspended in 0.9% saline – to induce steroid transformations in faeces, and analyzed the products by liquid chromatography/tandem mass spectrometry, without the need for prior extraction. Norethandrolone was the internal standard. The linearity (R2: 0.987–0.999), sensitivity (LODs: 0.3 to 1.0 ng/mL; LOQs: 1.0 to 3.0 ng/mL), precision (intra‐day CVs: 2.6–8.2; inter‐day CVs: 4.5–11.5) and accuracy (percentage recovery: 89–120%) were calculated for the studied steroids. Androstenedione, androstadienedione, α‐ and β‐boldenone, testosterone and epitestosterone transformations were investigated. Mutual interconversion of steroids was observed, although 17β‐hydroxy steroids had low stability compared with 17α‐hydroxy and 17‐keto steroids. The results suggest that this simple in vitro system may be an effective way of studying hormone transformations in faeces and, after analogue studies, in faeces‐contaminated urine. Copyright © 2007 John Wiley & Sons, Ltd.
Estimation of packet losses due to propagation impairments: Application to TCP performance over satellite
Authors: Drougas Athanasios E. , Panagopoulos Athanasios D. , Cottis Panayotis G. 
Published: December 2007

AbstractThe transmission control protocol (TCP) is widely used to provide reliable data transmission due to its congestion and flow control mechanisms that provide reliable error recovery in higher layers. In satellite links, various atmospheric phenomena may lead to high packet loss rate (PLR) degrading the TCP throughput. Modern satellite systems operate at frequencies above 10 GHz, where rainfall is the dominant fading mechanism leading to high bit error ratio and correlated packet losses. In this paper, a mathematical analysis is presented to accurately describe the statistical properties of the packet‐error process in a dynamically varying satellite channel. The proposed method is extended to provide PLR estimations when block forward error correction (FEC) is employed. A new Markov‐based method, based on the previous analysis and adapted to the rain‐faded satellite channel, is also presented for the estimation of TCP SACK throughput and tested against simulation results. Based on the information provided by the packet‐error model, a study between the TCP performance under various FEC schemes and a proposed adaptive FEC scheme has provided indications about the superiority of the proposed model. Copyright © 2007 John Wiley & Sons, Ltd.
Recycling Technology for a Recycling Society and the Consumer's Expected Consciousness: Recycling from the Viewpoint of Four Items of Home Appliances
Authors: Sakurai Toshiaki , Kubo Ryogo , Watanabe Masami , Ogi Hiromi 
Published: December 2007

AbstractThe concept of ‘recycling’ was adopted to solve the overuse of resources by mass production and mass consumption of products in the 20th century. In the latter half of the 20th century, all companies started recycling activities slowly but positively, and some of them established their own recycling plants. This article introduces the processes through which used home appliances are made into materials (for reuse), and the machines, facilities, and methods for such reuse, as well as the results of their actual application by the study of a recycling plant. It is expected that this article would motivate the readers for recycling and to consider and feel what we, consumers, should do. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Design Estimation of the Hybrid Power Source Railway Vehicle based on the Multiobjective Optimization by the Dynamic Programming
Authors: Ogawa Tomoyuki , Yoshihara Hiroaki , Wakao Shinji , Kondo Keiichiro , Kondo Minoru 
Published: December 2007

AbstractThe power source of hybrid railway vehicles consists of both generation and energy storage devices. The hybrid vehicles have a high degree of freedom in the system design because they have different power sources. Therefore, it is difficult to establish generalized design methods of the power system. Various patterns of device capacities of generation and energy storage equipments are available for the hybrid vehicle. And various types of power control strategies are also selectable. With this background, this paper proposes a globally searched design estimation method for hybrid vehicles, which is based on multiobjective optimization by dynamic programming. The proposed method enables us to globally clarify the optimal candidates in accordance with various railway lines from a wide search domain. This results in various design concepts of the hybrid vehicles. Then, this paper confirms that the proposed method provides effective design guidelines for the conceptual design of the hybrid vehicles. Therefore the proposed method is useful for the design problem of hybrid vehicles that have a higher degree of freedom compared to electric railway vehicles. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
IPMSM Position Sensorless Drives Using Robust Adaptive Observer on Stationary Reference Frame
Authors: Hasegawa Masaru , Matsui Keiju 
Published: December 2007

AbstractThis paper presents a novel sensorless control system for an interior permanent magnet synchronous motor (IPMSM) using adaptive observer on a stationary reference frame with its design and some experiments of position sensorless control. In sensorless control of IPMSM, adaptive observer structure and its design remain as one of the open problems. This is because the linear model on the stationary reference frame for IPMSM has not been established so far. As a result, the construction of an adaptive observer seems to be complicated owing to nonlinearity of the IPMSM model. From this viewpoint, a novel linear model of IPMSM on a stationary reference frame is first described in this paper. Second, an adaptive observer design is proposed based on γ‐positive real problem, yielding realization of both robust position estimation and robustly stable speed adaptation with respect to speed adaptation delay. Finally, some experiments with and without load torque at low and middle speed ranges are shown to demonstrate the feasibility and the effectiveness of the proposed system. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Image‐Based Crack Detection for Real Concrete Surfaces
Authors: Yamaguchi Tomoyuki , Nakamura Shingo , Saegusa Ryo , Hashimoto Shuji 
Published: December 2007

AbstractIn this paper, we introduce a novel image‐based approach to detect cracks in concrete surfaces. Crack detection is important for the inspection, diagnosis, and maintenance of concrete structures. However, conventional image‐based approaches cannot achieve precise detection since the image of the concrete surface contains various types of noise due to different causes such as concrete blebs, stain, insufficient contrast, and shading. In order to detect the cracks with high fidelity, we assume that they are composed of thin interconnected textures and propose an image‐based percolation model that extracts a continuous texture by referring to the connectivity of brightness and the shape of the percolated region, depending on the length criterion of the scalable local image processing techniques. Additionally, noise reduction based on the percolation model is proposed. We evaluated the validity of the proposed technique by using precision recall and receiver operating characteristic (ROC) analysis by means of some experiments with actual concrete surface images. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Pursuit‐Escape Particle Swarm Optimization
Authors: Higashitani Mitsuharu , Ishigame Atsushi , Yasuda Keiichiro 
Published: December 2007

AbstractThis paper presents a new Particle Swarm Optimization (PSO) with pursuit and escape behavior. This method takes a cue from the behaviors of schools of sardines and pods of killer whales. When the sardines are attacked by the killer whales, they would behave unusually, that is, the sardines would escape from the killer whales, and on another front, the killer whales would pursue the sardines. By this method, particles are divided into two categories called the pursuit‐particles and the escape‐particles, having interactions with each other. They play the key roles of intensification and diversification, respectively. This allows the particles to avoid local optimal solutions and find a global optimal one, and also achieve an appropriate balance between diversification (global search) and intensification (local search) during the search. Then, the proposed method is validated through numerical simulations using several functions which are well‐known as the optimization benchmark problems by comparing them to powerful methods such as SAPPO, LDIWM, and CFM. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.