The Experts below are selected from a list of 216 Experts worldwide ranked by ideXlab platform
Yakichi Higo - One of the best experts on this subject based on the ideXlab platform.
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micromechanical characterization of deformation behavior in ferrous lath martensite
Journal of Alloys and Compounds, 2013Co-Authors: Akinobu Shibata, Takashi Nagoshi, Masato Sone, Yakichi HigoAbstract:Abstract Local deformation behavior around the Block Boundary of lath martensite structure was studied through a micro-bending test and microstructural observation. When the misorientation of operated slip systems across the Block Boundary is small, the relief corresponding to the Block Boundary appeared by deformation. This suggested that the slip transferred directly across the Block Boundary. In the case of the large misorientation of operated slip systems across the Block Boundary, however, there is no evidence that slips were transferred directly across the Block Boundary. The small misorientation of operated slip systems across the Block Boundary also induced the obvious load drop in the load–displacement curve of micro-bending test. We considered that the flow stress at the region above the Block Boundary was decreased due to the transfer of pile-up dislocations across the Block Boundary after reaching some critical stress, resulting in the load drop in the load–displacement curve.
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evaluation of the Block Boundary and sub Block Boundary strengths of ferrous lath martensite using a micro bending test
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: Akinobu Shibata, Takashi Nagoshi, Masato Sone, Yakichi HigoAbstract:Abstract We report our investigation of the Block Boundary and sub-Block Boundary strengths of lath martensite evaluated through a micro-bending test. The sub-Block boundaries contribute very little to the macroscopic strength of the lath martensite. In contrast, the presence of a Block Boundary in the specimen greatly increased the strength. In addition, the Block Boundary induced a serrated flow and load drop after yielding in the load–displacement curve. The load drop and serrated flow were attributable to dislocation pile-up and subsequent propagation of dislocations across the Block Boundary. In a microstructural observation of specimens after deformation, we found that a Block Boundary significantly restricts the motion of dislocations, while a sub-Block Boundary does not. We concluded that the Block Boundary is the most effective grain Boundary for strength in lath martensite.
Akinobu Shibata - One of the best experts on this subject based on the ideXlab platform.
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micromechanical characterization of deformation behavior in ferrous lath martensite
Journal of Alloys and Compounds, 2013Co-Authors: Akinobu Shibata, Takashi Nagoshi, Masato Sone, Yakichi HigoAbstract:Abstract Local deformation behavior around the Block Boundary of lath martensite structure was studied through a micro-bending test and microstructural observation. When the misorientation of operated slip systems across the Block Boundary is small, the relief corresponding to the Block Boundary appeared by deformation. This suggested that the slip transferred directly across the Block Boundary. In the case of the large misorientation of operated slip systems across the Block Boundary, however, there is no evidence that slips were transferred directly across the Block Boundary. The small misorientation of operated slip systems across the Block Boundary also induced the obvious load drop in the load–displacement curve of micro-bending test. We considered that the flow stress at the region above the Block Boundary was decreased due to the transfer of pile-up dislocations across the Block Boundary after reaching some critical stress, resulting in the load drop in the load–displacement curve.
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evaluation of the Block Boundary and sub Block Boundary strengths of ferrous lath martensite using a micro bending test
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: Akinobu Shibata, Takashi Nagoshi, Masato Sone, Yakichi HigoAbstract:Abstract We report our investigation of the Block Boundary and sub-Block Boundary strengths of lath martensite evaluated through a micro-bending test. The sub-Block boundaries contribute very little to the macroscopic strength of the lath martensite. In contrast, the presence of a Block Boundary in the specimen greatly increased the strength. In addition, the Block Boundary induced a serrated flow and load drop after yielding in the load–displacement curve. The load drop and serrated flow were attributable to dislocation pile-up and subsequent propagation of dislocations across the Block Boundary. In a microstructural observation of specimens after deformation, we found that a Block Boundary significantly restricts the motion of dislocations, while a sub-Block Boundary does not. We concluded that the Block Boundary is the most effective grain Boundary for strength in lath martensite.
Gene Cheung - One of the best experts on this subject based on the ideXlab platform.
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Arbitrarily Shaped Motion Prediction for Depth Video Compression using Arithmetic Edge Coding
2016Co-Authors: Ismael Daribo Member, Dinei Florencio, Senior Member, Gene CheungAbstract:Abstract—Depth image compression is important for com-pact representation of 3D visual data in “texture-plus-depth” format, where texture and depth maps from one or more viewpoints are encoded and transmitted. A decoder can then synthesize a freely chosen virtual view via depth-image-based rendering (DIBR) using nearby coded texture and depth maps as reference. Further, depth information can be used in other image processing applications beyond view synthesis, such as object identification, segmentation, etc. In this paper, we leverage on the observation that “neighboring pixels of similar depth have similar motion ” to efficiently encode depth video. Specifically, we divide a depth Block containing two zones of distinct values (e.g., foreground and background) into two arbitrarily shaped regions (sub-Blocks) along the dividing Boundary before performing sep-arate motion prediction (MP). While such arbitrarily shaped sub-Block MP can lead to very small prediction residuals (resulting in few bits required for residual coding), it incurs an overhead to transmit the dividing boundaries for sub-Block identification at decoder. To minimize this overhead, we first devise a scheme called arithmetic edge coding (AEC) to efficiently code boundaries that divide Blocks into sub-Blocks. Specifically, we propose to incorporate the Boundary geometrical correlation in an adaptive arithmetic coder in the form of a statistical model. Then, we propose two optimiza-tion procedures to further improve the edge coding perfor-mance of AEC for a given depth image. The first procedure operates within a code Block, and allows lossy compression of the detected Block Boundary to lower the cost of AEC, with an option to augment Boundary depth pixel values matching the new Boundary, given the augmented pixels do not adversely affect synthesized view distortion. The second procedure operates across code Blocks, and systematically identifies Blocks along an object contour that should be coded using sub-Block MP via a rate-distortion optimized trellis. Experimental results show an average overall bitrate reduction of up to 33 % over classical H.264/AVC. I
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arbitrarily shaped motion prediction for depth video compression using arithmetic edge coding
IEEE Transactions on Image Processing, 2014Co-Authors: Ismael Daribo, Dinei Florencio, Gene CheungAbstract:Depth image compression is important for compact representation of 3D visual data in texture-plus-depth format, where texture and depth maps from one or more viewpoints are encoded and transmitted. A decoder can then synthesize a freely chosen virtual view via depth-image-based rendering using nearby coded texture and depth maps as reference. Further, depth information can be used in other image processing applications beyond view synthesis, such as object identification, segmentation, and so on. In this paper, we leverage on the observation that neighboring pixels of similar depth have similar motion to efficiently encode depth video. Specifically, we divide a depth Block containing two zones of distinct values (e.g., foreground and background) into two arbitrarily shaped regions (sub-Blocks) along the dividing Boundary before performing separate motion prediction (MP). While such arbitrarily shaped sub-Block MP can lead to very small prediction residuals (resulting in few bits required for residual coding), it incurs an overhead to transmit the dividing boundaries for sub-Block identification at decoder. To minimize this overhead, we first devise a scheme called arithmetic edge coding (AEC) to efficiently code boundaries that divide Blocks into sub-Blocks. Specifically, we propose to incorporate the Boundary geometrical correlation in an adaptive arithmetic coder in the form of a statistical model. Then, we propose two optimization procedures to further improve the edge coding performance of AEC for a given depth image. The first procedure operates within a code Block, and allows lossy compression of the detected Block Boundary to lower the cost of AEC, with an option to augment Boundary depth pixel values matching the new Boundary, given the augmented pixels do not adversely affect synthesized view distortion. The second procedure operates across code Blocks, and systematically identifies Blocks along an object contour that should be coded using sub-Block MP via a rate-distortion optimized trellis. Experimental results show an average overall bitrate reduction of up to 33% over classical H.264/AVC.
I J Wassell - One of the best experts on this subject based on the ideXlab platform.
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adaptive Block compressive sensing toward a real time and low complexity implementation
IEEE Access, 2020Co-Authors: Joseph Zammit, I J WassellAbstract:Adaptive Block-based compressive sensing (ABCS) algorithms are studied in the context of the practical realisation of compressive sensing on resource-constrained image and video sensing platforms that use single-pixel cameras, multi-pixel cameras or focal plane processing sensors. In this paper, we introduce two novel ABCS algorithms that are suitable for compressively sensing images or intra-coded video frames. Both use deterministic 2D-DCT dictionaries when sensing the images instead of random dictionaries. The first uses a low number of compressive measurements to compute the Block Boundary variation (BBV) around each image Block, from which it estimates the number of 2D-DCT transform coefficients to measure from each Block. The second uses a low number of DCT domain (DD) measurements to estimate the total number of transform coefficients to capture from each Block. The two algorithms permit reconstruction in real time, averaging 8 ms and 26 ms for 256 × 256 and 512 × 512 greyscale images, respectively, using a simple inverse 2D-DCT operation without requiring GPU acceleration. Furthermore, we show that an iterative compressive sensing reconstruction algorithm (IDA), inspired by the denoising-based approximate message passing algorithm, can be used as a post-processing, quality enhancement technique. IDA trades off real-time operation to yield performance improvement over state-of-the-art GPU-assisted algorithms of 1.31 dB and 0.0152 in terms of PSNR and SSIM, respectively. It also exceeds the PSNR performance of a state-of-the-art deep neural network by 0.4 dB and SSIM by 0.0126.
Chengjian Zhang - One of the best experts on this subject based on the ideXlab platform.
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solving nonlinear functional differential and functional equations with constant delay via Block Boundary value methods
Mathematics and Computers in Simulation, 2019Co-Authors: Xiaoqiang Yan, Chengjian ZhangAbstract:Abstract This paper deals with the numerical solutions of nonlinear functional-differential and functional equations (FDFEs) with constant delay. The Block Boundary value methods (BBVMs) are extended to solve the FDFEs. Under the suitable conditions, it is shown that the extended BBVMs are uniquely solvable and globally stable. Moreover, the method can be convergent of order p whenever the Lipschitz condition holds and this method is preconsistent and p -order consistent. With several numerical examples, the theoretical results and computational validity of the extended BBVMs are further confirmed.
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Convergence and stability of Block Boundary value methods applied to nonlinear fractional differential equations with Caputo derivatives
Applied Numerical Mathematics, 2019Co-Authors: Yongtao Zhou, Chengjian ZhangAbstract:Abstract In this paper, by combining the p-order Block Boundary value methods with the m-th Lagrange interpolation, a class of new numerical methods for solving nonlinear fractional differential equations with the γ-order ( 0 γ 1 ) Caputo derivatives are obtained. It is proved under some appropriate conditions that the induced methods are convergent of order min { p , m − γ + 1 } and globally stable. Several numerical examples are given to illustrate the theoretical results and the computational effectiveness and accuracy of the methods.
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The adapted Block Boundary value methods for singular initial value problems
Calcolo, 2018Co-Authors: Huiru Wang, Chengjian ZhangAbstract:This paper deals with the numerical methods for solving singular initial value problems. By adapting the Block Boundary value methods (BBVMs) for regular initial value problems, a class of adapted BBVMs are constructed for singular initial value problems. It is proved under some suitable conditions that the adapted BBVMs are uniquely solvable, stable and convergent of order p, where p is the consistence order of the methods. Several numerical examples are performed to verify the stability, efficiency and accuracy of the adapted methods. Moreover, a comparison between the adapted BBVMs and the IEM-based iterated defect correction methods is given. The numerical results show that the adapted BBVMs are comparable.
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Block Boundary value methods applied to functional differential equations with piecewise continuous arguments
Applied Numerical Mathematics, 2017Co-Authors: Chengjian ZhangAbstract:Abstract This paper deals with a class of functional differential equations with piecewise continuous arguments. Block Boundary value methods (BBVMs) are extended to solve this class of equations. It is shown under the Lipschitz condition that the order of convergence of an extended Block Boundary value method coincides with its order of consistency. Moreover, we study the linear stability of the extended methods and give the corresponding asymptotical stability criterion. In the end, with several numerical examples, the theoretical results and the computational effectiveness of the methods are further illustrated.
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Block Boundary value methods for solving volterra integral and integro differential equations
Journal of Computational and Applied Mathematics, 2012Co-Authors: Hao Chen, Chengjian ZhangAbstract:Reducible quadrature rules generated by Boundary value methods are considered in Block version and applied to solve the second kind Volterra integral equations and Volterra integro-differential equations. These extended Block Boundary value methods are shown to possess both excellent stability properties and high accuracy for Volterra-type equations. Numerical experiments are presented and the efficiency, accuracy and stability of the schemes are confirmed.