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Gain enhancement in two-stream free electron laser with a planar wiggler and an axial guide magnetic field

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Chinese Physics B 2012年第9期21卷 247-250页

作者： S.Saviz z.Rezaei Farzin m.Aghamir Plasma Physics Research Center Science and Research BranchIslamic Azad University Department of Physics University of Tehran

The theory for a two-stream free electron laser （FEL） consisting of a relativistic electron beam transported alongthe axis of a planar wiggler in the presence of an axial guiding magnetic field is proposed and investigated. The electron trajectories and the small signal gain are derived. The characteristic of the linear gain and the normalized maximum gain are studied numerically. The result shows that the normalized maximum gain is considerably enhanced in comparison with that of the single stream. The effect of the difference between the energies of the two beams in this configuration of FEL is also considered, and we find that the gain is affected by the energy differences between groups 1 and 2.

关键词： wo-stream free-electron laser

Charge and spin-dependent thermal efficiency of polythiophene molecular junction in presence of dephasing

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Chinese Physics B 2015年第10期24卷 576-583页

作者： z.Golsanamlou m.Bagheri Tagani H.Rahimpour Soleimani Department of Physics University of Guilan

The charge and spin-dependent thermoelectric properties of different lengths of polythiophene in a molecular junction are investigated using the B ¨uttiker probe method within Green function formalism in linear response regime. The coupling of the molecular chain to three-dimensional ferromagnetic electrodes is described by a tight-binding model for both parallel and antiparallel spin configurations. The decrease of height of transmission probability peaks and thermoelectric coefficients are observed in the presence of the B ¨uttiker probes. The reduction is more intensive in the strong dephased *** show that the spin magnetothermopower is bigger than the charge magnetothermopower due to the larger difference between the spin thermopowers with respect to the charge ones. In addition, we observed that the kind of carriers participating in the thermoelectric transport depends on the number of the thiophene rings.

关键词： polythiophene Green function thermoelectric coefficients Buttiker probes ferromagnetic elec-trodes

Effect of Yttrium Addition on microstructural Characteristics and Superplastic Behavior of Friction Stir Processed zK60 Alloy

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Journal of materials Science & Technology 2013年第12期29卷 1116-1122页

作者： z.A.Luo G.m.Xie z.Y.ma G.L.Wang G.D.Wang State Key Laboratory of Rolling and Automation Northeastern University Shenyang National Laboratory for materials Science Institute of Metal ResearchChinese Academy of Sciences

As-extruded zK60 and zK60-Y magnesium alloy plates were successfully processed via friction stir processing （FSP） at a tool rotation rate of 1600 r/rain and a traverse speed of 200 mm/min. FSP resulted in the formation of equiaxed recrystallized microstructures with the average grain sizes of ,-8.5 and -4.7 μm in the zK60 and zK60-Y alloys, respectively. moreover, FSP broke and dispersed the mgzn2 and W-phase （mg3zn3Y2） particles and dissolved mgzn2 phase in the FSP zK60 alloy. With the addition of rare earth element yttrium （Y） into the zK60 alloy, the ratio of the high angle grain boundaries （HAGBs） in the FSP alloys increased from 64% to 90%, and a certain amount of twins appeared in the FSP zK60-Y alloy. The maximum elongation of 1200% and optimum strain rate of 3 X 10-3 s-1 achieved at 450 °C in the FSP zK60-Y alloy were substantially higher than those of the FSP zK60 alloy. This is attributed to the fine grains with high ratio of HAGBs and the distribution of a large number of dispersed second phase particles with high thermal stability in the FSP zK60-Y alloy. Grain boundary sliding was identified as the primary deformation mechanism in the FSP zK60 and zK60-Y alloys from the superplastic data analyses and surficial morphology observations.

关键词： magnesium alloy Friction stir processing Rare earth element microstructure Superplasticity

Residual Strains in a Nanometer Thick Cr Film measured on micromachined Beams

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Journal of materials Science & Technology 2009年第1期25卷 77-80页

作者： z.m. zhou Yong zhou Ying Cao Haiping mao Key Laboratory for Thin Film and microfabrication Technology of ministry of Education Research Institute of Micro/Nano Science and Technology Shanghai Jiao Tong University Shanghai 200030 China

A Cr film with a 75 nm thickness sputtered on a Si substrate was used to fabricate microbridge and microcantilever samples with the mEmS （microelectromechanical system） technique. The profile of the buckled beams was measured by using the interference technique with white light and fitted with a theoretical result. The uniform residual strain in the bridge samples was deduced from the variation of buckling amplitude with the beam length. On the other hand, the gradient residual strain was determined from the deflection profile of the cantilever. The residual uniform and gradient strain in the Cr film are about 4.96×10^-3 and 4.2967×10^-5, respectively.

关键词： Residual Strain microelectromechanical system (mEmS) microbridge microcantilever

Robust Watermarking Algorithm for medical Volume Data Based on Polar Cosine Transform and 3D-DCT

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Computers, materials & Continua 2023年第6期75卷 5853-5870页

作者： Pengju zhang Jingbing Li Uzair Aslam bhatti Jing Liu Yen-wei Chen Dekai Li Lei Cao School of Information and Communication Engineering Hainan UniversityHaikou570100China State Key Laboratory of marine Resource Utilization in the South China Sea Hainan UniversityHaikou570100China Research Center for Healthcare Data Science Zhejiang LabHangzhou311121China Graduate School of Information Science and Engineering Ritsumeikan UniversityKyoto5258577Japan

The amount of 3D data stored and transmitted in the Internet of medical Things(IomT)is increasing,making protecting these medical data increasingly ***,there are relatively few researches on 3D data ***,due to the particularity of medical data,strict data quality should be considered while protecting data *** solve the problem,in the field of medical volume data,we proposed a robust watermarking algorithm based on Polar Cosine Transform and 3D-Discrete Cosine Transform(PCT and 3D-DCT).Each slice of the volume data was transformed by PCT to obtain feature row vector,and then the reshaped three-dimensional feature matrix was transformed by *** on the contour information of the volume data and the detail information of the inner slice,the visual feature vector was obtained by applying the per-ceptual *** addition,the watermark was encrypted by a multi-sensitive initial value Sine and Piecewise linear chaotic mapping(SPm)system,and embedded as a zero *** key was stored in a third *** the same experimental conditions,when the volume data is rotated by 80 degrees,cut 25%along the z axis,and the JPEG compression quality is 1%,the Normalized Correlation Coefficient(NC)of the extracted watermark is 0.80,0.89,and 1.00 respectively,which are significantly higher than the comparison algorithm.

关键词： Volume data watermark zero watermark SPm PCT and 3D-DCT

Body Contour in the Post-Bariatric male Patient

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modern Plastic Surgery 2024年第2期14卷 15-22页

作者： Erick zúñiga-Garza Israel Salgado-Adame Claudio D. Rojas-Gutiérrez Laura maría Rodríguez-Barrios Guillermo Álvarez-Sánchez Eduardo Camacho-Quintero Department of Plastic Surgery National Medical Center &#822020 de Noviembre&#8221 Mexico City Mexico

Background: Obesity is currently considered a public health problem. Bariatric procedures have become an important part of obesity management and, consequently, the number of male patients seeking post-bariatric reconstructive procedures have increased. Therefore, the clinical approach and understanding of the body contour of this population have become more relevant. The goal of post-bariatric reconstruction is to enhance the male silhouette through removal of skin and adipose tissue excess, and abdominal rectus diastasis repair. material and methods: We conducted a retrospective study at the Plastic and Reconstructive Surgery Department of the National medical Center “20 de Noviembre”. All male patients referred to our department to start a post-bariatric reconstruction protocol from January 2018 to December 2022 were included in this study. Results: In total, 15 patients who underwent corporal contouring procedures were included;median age was 49.2 years with minimum of 33 years, and a maximum of 57 years. median Body mass index was 28.4 kg/m2 with minimum of 22 kg/m2 and maximum of 38 kg/m2. All patients were treated 18 months after their bariatric surgery. All patients underwent an abdominoplasty as a body contouring procedure. 4 (26.7%) patients presented complications related to the surgery. Conclusion: We described a comprehensive and systematic approach to massive weight loss for male patients, suggesting an abdominal marking based on the patient’s clinical features and the expected results avoiding feminization of the abdominal body contour.

关键词： massive Weight Loss Post-Bariatric male Abdominoplasty Contouring

Spectral measurements of hypervelocity flow in an expansion tunnel

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Acta mechanica Sinica 2019年第1期35卷 24-31,I0002页

作者： C.K.Yuan K.zhou Y.F.Liu z.m.Hu z.L.Jiang State Key Laboratory of High-Temperature Gas Dynamic Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Sciences. University of Chinese Academy of Sciences Beijing 100049China China Academy of Aerospace Aerodynamics Beijing 100074China

Atmospheric reentry vehicles and planetary probes fly through the atmosphere at hypervelocity speed. At such speed, there is a significant proportion of heat load to the vehicle surface due to radiative heating. Accurate prediction needs a good knowledge of the radiation spectrum properties. In this paper, a high-speed camera and spectrograph coupled to an intensified charge-coupled device have bee n impleme nted to inv estigate the rad i at io n flow over a semi-cylinder model. The experiments were carried out in the JF16 expansi on timnel with secondary shock velocity of 7.9 km·s^-1. Results show that the emissio n spectrum comprises several atomic lines and molecular band systems. We give detailed data of the radiation spectrum, shock shape, shock detached distance and radiation intensity varying with space and wavelength. This valuable experimental dataset will be helpful to validate computational fluid dynamics codes and radiation models, which equates to increased prediction accuracy of radiation heating. Also, some suggestions for spectral measurement in hypervelocity flow field were list in the end.

关键词： Spectral measurement Hypervelocity flow Radiation Expansion tunnel

Review on Hydrogen Embrittlement of Press-hardened Steels for Automotive Applications

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Acta metallurgica Sinica(English Letters) 2023年第7期36卷 1123-1143页

作者： z.Wang Q.Lu z.H.Cao H.Chen m.X.Huang J.F.Wang General motors China Science Lab Shanghai201206China Department of mechanical Engineering The University of Hong KongPokfulam RoadHong Kong999077China Key Laboratory for Advanced materials of ministry of Education School of Materials Science and EngineeringTsinghua UniversityBeijing100084China

Press-hardened steel(PHS)with an ultimate tensile strength(UTS)of 1500 mPa has been widely used in automotive body-in-white in the last two decades,due to its ultra-high strength and excellent formability that is achieved by hot stamping ***,the application of PHS with UTS exceeding 1500 mPa in automotive industry could be deferred due to the increased risk of hydrogen *** reduce this kind of risk,recent research efforts have been focused on various ways to optimize the microstructure of *** present review intends to summarize these efforts,to highlight present solutions to address hydrogen embrittlement,and to shed light on directions for future *** influence of microstructure on the hydrogen embrittlement of PHS has been discussed in terms of both the steel substrate and the surface *** substrate part covers the influence of martensite,carbides,inclusions,and retained austenite,while the surface part covers decarburization and oxidation,pre-coating,and trimming.

关键词： Hot stamping Press-hardened steels Coating-free Hydrogen embrittlement Fracture Al-Si coating

Shaped Co^(2+) doped TiO_(2) nanocrystals synthesized from nanotubular precursor: Structure and ferromagnetic behavior

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Journal of Advanced Ceramics 2017年第3期6卷 220-229页

作者： m.VRANJES J.KULJANIN JAKOVLJEVIC z.KONSTANTINOVIC A.POmAR m.STOILJKOVIC m.mITRIC T.RADETIC z.SAPONJIC Vinca Institute of Nuclear Sciences University of BelgradeP.O.Box 52211001 BelgradeSerbia Center for Solid State Physics and New materials Institute of Physics BelgradeUniversity of BelgradePregrevica 11811080 BelgradeSerbia Institut de Ciència de materials de Barcelona CSICCampus UAB08193 BellaterraSpain Faculty of Technology and metallurgy University of BelgradeKarnegijeva 411120 BelgradeSerbia

Co2+ doped TiO2 nanocrystals were synthetized by a hydrothermal treatment procedure applied to precursor dispersion of titania nanotubes and Co2+ ions. mixture of polygonal and prolate spheroid-like nanocrystals was obtained. The results of X-ray diffraction (XRD) analysis showed that resulted nanocrystals retain anatase crystal phase for both dopant concentrations (1.69 and 2.5 at%), but the crystal lattice parameters were affected. Reflection spectra revealed altered optical properties compared to bare TiO2. Room temperature ferromagnetic ordering with saturation magnetic moment in the range of 0.001–0.002 μB /Co was observed for both measured films made of Co2+ doped TiO2 nanocrystals.

关键词： hydrothermal synthesis X-ray diffraction(XRD) transmission electron microscopy(TEm) doped TiO_(2) magnetic properties