The Experts below are selected from a list of 171231 Experts worldwide ranked by ideXlab platform
Hailin Zhang - One of the best experts on this subject based on the ideXlab platform.
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hypothesis testing based fast converged blind estimation of transmit antenna number for mimo systems
IEEE Transactions on Vehicular Technology, 2018Co-Authors: Tao Li, Yongzhao Li, Leonard J Cimini, Hailin ZhangAbstract:Multiple-input multiple-output technology brings new challenges for detecting signal parameters in some intelligent systems. An accurate estimation of the transmit-antenna number is the prerequisite for estimating other signal parameters. Employing random matrix theory, we propose two hypothesis testing based algorithms to blindly estimate the transmit-antenna number. By exploiting hypothesis testing, the blind estimation problem is converted to a location problem, which seeks the location of the boundary between the signal subspace and the noise subspace of the Received Sample covariance matrix. Then, the estimated transmit-antenna number is determined by the dimension of the signal subspace. Extensive simulations verify that the two proposed algorithms perform better under a wide range of signal-to-noise ratios and Sample lengths, compared with conventional algorithms based on Akaike information criterion, minimum description length, and predicted eigenvalue threshold.
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estimation of transmit antenna number with different space frequency transmission schemes for mimo ofdm systems
Electronics Letters, 2018Co-Authors: Tao Li, Yongzhao Li, Mingjun Gao, Hailin ZhangAbstract:A hypothesis testing based algorithm is proposed to estimate the transmit-antenna number with different space-frequency transmission schemes for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. The ranks of Received Sample covariance matrices composed by every two adjacent subcarriers can be estimated by utilising the statistical property of the largest noise eigenvalue. With a series of the estimated values of the ranks, the number of transmit antennas is determined by a decision mechanism, which is designed based on the frequencies of the rank values. Simulations demonstrate that the proposed algorithm performs well without the prior knowledge of the space-frequency transmission scheme.
Mohamed Khitouni - One of the best experts on this subject based on the ideXlab platform.
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Study of the microstructure and texture heterogeneities of Fe–48wt%Ni alloy severely deformed by equal channel angular pressing
Journal of Materials Science, 2019Co-Authors: Rabeb Lachhab, Mohamed Ali Rekik, Anne-laure Helbert, Hiba Azzeddine, Thierry Baudin, François Brisset, Mohamed KhitouniAbstract:A Fe–48wt%Ni alloy was processed by severe plastic deformation using equal channel angular pressing process. A stacking of 9 sheets was introduced and pressed up to two passes into die with an inner angle of Φ = 90º and outer arc of curvature ψ = 17° at room temperature following route A. The same material in bulk form was also ECAPed up to one pass. The microstructure and the texture were investigated by means of electron backscattered diffraction and X-ray diffraction, respectively. To evaluate the mechanical response, Vickers microhardness was carried out. The given analyses concern the as-Received Sample, the peripheral and the central plates of the pressed stacks and the upper, the middle and the lower parts of the pressed bulk material. The deformation was heterogeneous, and variations in texture and microstructure, resulting from different efficiencies in the shearing process, were locally noted. For the stacks Samples, the microstructure evolved from equiaxed grains of 9 μm with high fraction of high-angle grain boundaries (around 90%) to a heterogeneous fine grain structure with an average grain size of 3 μm after two passes. On the contrary, for the bulk Sample, the evolution was to a banded structure after one pass. Results of mechanical property show that microhardness increased significantly from 147 Hv before deformation to mean values of 244 (after one pass) and 235 Hv (after two passes) for the bulk and stacked Samples, respectively. The Hall–Petch effect and dislocation density were evaluated as most responsible in material strengthening.
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Study of the microstructure and texture heterogeneities of Fe–48wt%Ni alloy severely deformed by equal channel angular pressing
Journal of Materials Science, 2019Co-Authors: Rabeb Lachhab, Mohamed Ali Rekik, Anne-laure Helbert, Hiba Azzeddine, Thierry Baudin, François Brisset, Mohamed KhitouniAbstract:A Fe-48wt%Ni alloy was processed by severe plastic deformation using equal channel angular pressing process. A stacking of 9 sheets was introduced and pressed up to two passes into die with an inner angles of Φ=90º and outer arc of curvature ψ= 17° at room temperature following route A. The same material in bulk form was also ECAPed up to one pass. The microstructure and the texture were investigated by means of electron backscattered diffraction and X-ray diffraction, respectively. To evaluate the mechanical response, Vickers microhardness was carried out. The given analyses concern the as-Received Sample, the peripheral and the central plates of the pressed stacks and the upper, the middle and the lower parts of the pressed bulk material. The deformation was heterogeneous and variations in texture and microstructure, resulting from different efficiencies in the shearing process, were locally noted. For the stacks Samples, the microstructure evolved from equiaxed grains of 9 μm with high fraction of high-angle grain boundaries (around 90%) to a heterogeneous fine grain structure with an average grain size of 3 m after two passes. On the contrary, for the bulk Sample, the evolution was
Tao Li - One of the best experts on this subject based on the ideXlab platform.
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hypothesis testing based fast converged blind estimation of transmit antenna number for mimo systems
IEEE Transactions on Vehicular Technology, 2018Co-Authors: Tao Li, Yongzhao Li, Leonard J Cimini, Hailin ZhangAbstract:Multiple-input multiple-output technology brings new challenges for detecting signal parameters in some intelligent systems. An accurate estimation of the transmit-antenna number is the prerequisite for estimating other signal parameters. Employing random matrix theory, we propose two hypothesis testing based algorithms to blindly estimate the transmit-antenna number. By exploiting hypothesis testing, the blind estimation problem is converted to a location problem, which seeks the location of the boundary between the signal subspace and the noise subspace of the Received Sample covariance matrix. Then, the estimated transmit-antenna number is determined by the dimension of the signal subspace. Extensive simulations verify that the two proposed algorithms perform better under a wide range of signal-to-noise ratios and Sample lengths, compared with conventional algorithms based on Akaike information criterion, minimum description length, and predicted eigenvalue threshold.
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estimation of transmit antenna number with different space frequency transmission schemes for mimo ofdm systems
Electronics Letters, 2018Co-Authors: Tao Li, Yongzhao Li, Mingjun Gao, Hailin ZhangAbstract:A hypothesis testing based algorithm is proposed to estimate the transmit-antenna number with different space-frequency transmission schemes for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. The ranks of Received Sample covariance matrices composed by every two adjacent subcarriers can be estimated by utilising the statistical property of the largest noise eigenvalue. With a series of the estimated values of the ranks, the number of transmit antennas is determined by a decision mechanism, which is designed based on the frequencies of the rank values. Simulations demonstrate that the proposed algorithm performs well without the prior knowledge of the space-frequency transmission scheme.
Rabeb Lachhab - One of the best experts on this subject based on the ideXlab platform.
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Study of the microstructure and texture heterogeneities of Fe–48wt%Ni alloy severely deformed by equal channel angular pressing
Journal of Materials Science, 2019Co-Authors: Rabeb Lachhab, Mohamed Ali Rekik, Anne-laure Helbert, Hiba Azzeddine, Thierry Baudin, François Brisset, Mohamed KhitouniAbstract:A Fe–48wt%Ni alloy was processed by severe plastic deformation using equal channel angular pressing process. A stacking of 9 sheets was introduced and pressed up to two passes into die with an inner angle of Φ = 90º and outer arc of curvature ψ = 17° at room temperature following route A. The same material in bulk form was also ECAPed up to one pass. The microstructure and the texture were investigated by means of electron backscattered diffraction and X-ray diffraction, respectively. To evaluate the mechanical response, Vickers microhardness was carried out. The given analyses concern the as-Received Sample, the peripheral and the central plates of the pressed stacks and the upper, the middle and the lower parts of the pressed bulk material. The deformation was heterogeneous, and variations in texture and microstructure, resulting from different efficiencies in the shearing process, were locally noted. For the stacks Samples, the microstructure evolved from equiaxed grains of 9 μm with high fraction of high-angle grain boundaries (around 90%) to a heterogeneous fine grain structure with an average grain size of 3 μm after two passes. On the contrary, for the bulk Sample, the evolution was to a banded structure after one pass. Results of mechanical property show that microhardness increased significantly from 147 Hv before deformation to mean values of 244 (after one pass) and 235 Hv (after two passes) for the bulk and stacked Samples, respectively. The Hall–Petch effect and dislocation density were evaluated as most responsible in material strengthening.
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Study of the microstructure and texture heterogeneities of Fe–48wt%Ni alloy severely deformed by equal channel angular pressing
Journal of Materials Science, 2019Co-Authors: Rabeb Lachhab, Mohamed Ali Rekik, Anne-laure Helbert, Hiba Azzeddine, Thierry Baudin, François Brisset, Mohamed KhitouniAbstract:A Fe-48wt%Ni alloy was processed by severe plastic deformation using equal channel angular pressing process. A stacking of 9 sheets was introduced and pressed up to two passes into die with an inner angles of Φ=90º and outer arc of curvature ψ= 17° at room temperature following route A. The same material in bulk form was also ECAPed up to one pass. The microstructure and the texture were investigated by means of electron backscattered diffraction and X-ray diffraction, respectively. To evaluate the mechanical response, Vickers microhardness was carried out. The given analyses concern the as-Received Sample, the peripheral and the central plates of the pressed stacks and the upper, the middle and the lower parts of the pressed bulk material. The deformation was heterogeneous and variations in texture and microstructure, resulting from different efficiencies in the shearing process, were locally noted. For the stacks Samples, the microstructure evolved from equiaxed grains of 9 μm with high fraction of high-angle grain boundaries (around 90%) to a heterogeneous fine grain structure with an average grain size of 3 m after two passes. On the contrary, for the bulk Sample, the evolution was
Razieh Samadipour - One of the best experts on this subject based on the ideXlab platform.
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A Study on Structural, Corrosion, and Sensitization Behavior of Ultrafine and Coarse Grain 316 Stainless Steel Processed by Multiaxial Forging and Heat Treatment
Journal of Materials Engineering and Performance, 2018Co-Authors: Seyed Rahim Kiahosseini, Seyyed Javad Mohammadi Baygi, Gholamreza Khalaj, Ali Khoshakhlagh, Razieh SamadipourAbstract:Cubic specimens from AISI 316 stainless steel were multiaxially forged to 15 passes and annealed at 1200 °C for 1, 2, and 3 h and finally sensitized at 700 °C for 24 h. Examination of Samples indicated that the hardness of the annealed Samples was reduced from 153 to 110, 81, and 74 HV for as-Received Sample and under 1, 2, and 3 h of annealing, and increased from 245 to 288 HV for Samples forged at 3 and 7 passes. However, no significant changes were observed in a large number of passes and at about 300 HV. Degree of sensitization of Samples was increased to approximately 27.3% at 3-h annealing but reduced to 1.23% by 15 passes of MF. The potentiodynamic polarization test shows that the breakdown potentials decreased with annealing time from 0.6 to − 102 (mV/SCE) for as-Received and 3-h annealed specimen. These potentials increased to approximately − 16.5 mV with the increase in MF passes to 15. These observations indicated that the chromium carbide deposition affects Cr-depleted zone, which can subsequently affect the degree of sensitization and pitting corrosion resistance of AISI 316 austenitic stainless steel.
