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Determination method of mesh size for numerical simulation of blast load in near-ground detonation

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Defence Technology（防务技术） 2024年第8期38卷 111-125页

作者： Doudou Si Zuanfeng pan Haipeng Zhang College of Civil Engineering Tongji UniversityShanghai 200092China State Key Lab of Disaster Reduction in Civil Engineering Tongji UniversityShanghai 200092China

In order to improve the overall resilience of the urban infrastructures, it is required to conduct blast resistant design for important building structures in the city. For complex terrain in the city, it is recommended to determine the blast load on the structures via numerical simulation. Since the mesh size of the numerical model highly depends on the explosion scenario, there is no generally applicable approach for the mesh size selection. An efficient method to determine the mesh size of the numerical model of near-ground detonation based on explosion scenarios is proposed in this study. The effect of mesh size on the propagation of blast wave under different explosive weights was studied, and the correlations between the mesh size effect and the charge weight or the scaled distance was described. Based on the principle of the finite element method and Hopkinson-Cranz scaling law, a mesh size measurement unit related to the explosive weight was proposed as the criterion for determining the mesh size in the numerical simulation. Finally, the applicability of the method proposed in this paper was verified by comparing the results from numerical simulation and the explosion tests and was verified in AUTODYN.

关键词： Blast load Mesh size effect Numerical simulation Scaled mesh size Verification

Thermal-hydraulic performance analysis and multi-objective optimization of a microchannel with staggered semi-elliptical ribs

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Science China Technological Sciences 2024年第10期67卷 3152-3167页

作者： CUI pan LIU Wei LIU ZhiChun School of Energy and Power Engineering Huazhong University of Science and Technology

To enhance the cooling capacity of traditional microchannels for high heat flux electronic devices,a microchannel design with staggered semi-elliptical ribs is proposed in this *** numerical simulations,the flow characteristics of the designed microchannel are compared with those of a smooth one,and the effects of rib width（Wr）,rib height（Hr）,and rib length（Lr）,on the thermal-hydraulic performance are investigated under laminar flow *** results show that the periodically arranged ribs induce periodic vortices within the microchannel,effectively promoting fluid mixing and enhancing heat *** Hrhave similar effects on microchannel performance,with an increase in them leading to an enhanced thermal performance at the expense of deteriorated hydraulic ***,Lrhas a comparatively weaker influence,with both the heat transfer and flow resistance initially growing with increasing Lrand then *** strike a balance between the two performances,a multi-objective optimization on the three geometrical parameters is conducted at a Reynolds number（Re） *** with simulation data,artificial neural networks are trained as surrogate models,and a multi-objective genetic algorithm is employed to derive the Pareto *** the TOPSIS decision-making method,an optimal compromise solution is determined as Wr=0.2415 mm,Hr=0.0976 mm,and Lr=0.6486 *** testing on the optimized microchannel reveals that it exhibits high heat transfer,middle flow resistance,and excellent overall performance,with the performance evaluation criterion（PEC） falling between 1.572 and 1.723 within the Re range of 220–660.

关键词： heat transfer enhancement microchannel semi-elliptical rib numerical simulation multi-objective optimization

Multiscale method for identifying and marking the multiform fractures from visible-light rock-mass images

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Underground Space 2024年第3期16卷 279-300页

作者： Yongbo pan Junzhi Cui Zhenhao Xu School of Mathematics and Statistics Zhengzhou UniversityZhengzhou 450001China The State Key Laboratory of Scientific and Engineering Computing Academy of Mathematics and Systems Science Chinese Academy of SciencesBeijing 100190China Geotechnical and Structural Engineering Research Center Shandong UniversityJinan 250100China

Multiform fractures have a direct impact on the mechanical performance of rock *** accurately identify multiform fractures,the distribution patterns of grayscale and the differential features of fractures in their neighborhoods are *** on this,a multiscale processing algorithm is *** multiscale process is as *** the neighborhood of pixels,a grayscale continuous function is constructed using bilinear interpolation,the smoothing of the grayscale function is realized by Gaussian local filtering,and the grayscale gradient and Hessian matrix are calculated with high *** small-scale blocks,the pixels are classified by adaptively setting the grayscale threshold to identify potential line segments and *** the global image,potential line segments and mini-fillings are spliced together by progressing the block frontier layer-by-layer to identify and mark multiform *** accuracy of identifying multiform fractures is improved by constructing a grayscale continuous function and adaptively setting the grayscale thresholds on small-scale *** the layer-by-layer splicing algorithm is performed only on the domain of the 2-layer small-scale blocks,reducing the *** using rock mass images with different fracture types as examples,the identification results show that the proposed algorithm can accurately identify the multiform fractures,which lays the foundation for calculating the mechanical parameters of rock masses.

关键词： Visible light rock-mass images Continuous grayscale function Small-scale blocks Multiform fractures

Event-triggered predefined-time control for full-state constrained nonlinear systems: A novel command filtering error compensation method

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Science China(Technological Sciences) 2024年第9期67卷 2867-2880页

作者： pan YingNan CHEN YiLin LIANG HongJing College of Control Science and Engineering Bohai UniversityJinzhou 121013China School of Automation Engineering University of Electronic Science and Technology of ChinaChengdu 611731China Laboratory of Electromagnetic Space Cognition and Intelligent Control Beijing 100089China

In this paper, a command filter-based adaptive fuzzy predefined-time event-triggered tracking control problem is investigated for uncertain nonlinear systems with time-varying full-state constraints. By designing a sliding mode differentiator, the inherent computational complexity problem within the predefined-time backstepping framework is solved. Different from the existing command filter-based finite-time and fixed-time control strategies that the convergence time of the filtering error is adjusted through the system initial value or numerous parameters, a novel command filtering error compensation method is presented,which tunes one control parameter to make the filtering error converge in the predefined time, thereby reducing the complexity of design and analysis of processing the filtering error. Then, an improved event-triggered mechanism(ETM) that builds upon the switching threshold strategy, in which an inverse cotangent function is designed to replace the residual term of the ETM,is proposed to gradually release the controller's dependence on the residual term with increasing time. Furthermore, a tan-type nonlinear mapping technique is applied to tackle the time-varying full-state constraints problem. By the predefined-time stability theory, all signals in the uncertain nonlinear systems exhibit predefined-time stability. Finally, the feasibility of the proposed algorithm is substantiated through two simulation results.

关键词： predefined-time control command filtering error compensation method event-triggered mechanism time-varying full-state constraints uncertain nonlinear systems

A blockchain-based data auditing scheme with key-exposure resistance for IIoT

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Science China(Information Sciences) 2024年第2期67卷 327-328页

作者： pan YANG Jingli REN Henan Academy of Big Data Zhengzhou University

The Industrial Internet of Things(IIoT) enables enterprises to collect data from end devices and outsource the data to cloud servers for flexible data sharing. Public auditing plays an important role in ensuring the integrity of the *** are blockchain-based public auditing schemes that utilize smart contracts to achieve decentralized verification(such as [1]),

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Rethinking the Encoder-decoder Structure in Medical Image Segmentation from Releasing Decoder Structure

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Journal of Bionic Engineering 2024年第3期21卷 1511-1521页

作者： Jiajia Ni Wei Mu An pan Zhengming Chen School of Artificial Intelligence Anhui Polytechnic UniversityWuhu241000China School of Information Science and Engineering HoHai UniversityChangzhou213000China

Medical image segmentation has witnessed rapid advancements with the emergence of encoder-decoder based *** the encoder-decoder structure,the primary goal of the decoding phase is not only to restore feature map resolution,but also to mitigate the loss of feature information incurred during the encoding ***,this approach gives rise to a challenge:multiple up-sampling operations in the decoder segment result in the loss of feature *** address this challenge,we propose a novel network that removes the decoding structure to reduce feature information loss(CBL-Net).In particular,we introduce a Parallel Pooling Module(PPM)to counteract the feature information loss stemming from conventional and pooling operations during the encoding ***,we incorporate a Multiplexed Dilation Convolution(MDC)module to expand the network's receptive ***,although we have removed the decoding stage,we still need to recover the feature map ***,we introduced the Global Feature Recovery(GFR)*** uses attention mechanism for the image feature map resolution recovery,which can effectively reduce the loss of feature *** conduct extensive experimental evaluations on three publicly available medical image segmentation datasets:DRIVE,CHASEDB and MoNuSeg *** results show that our proposed network outperforms state-of-the-art methods in medical image *** addition,it achieves higher efficiency than the current network of coding and decoding structures by eliminating the decoding component.

关键词： Medical image segmentation Encoder-decoder architecture Attention mechanisms Releasing decoder architecture Neural network

Semi-Varying Coefficient panel Data Model with Technical Indicators Predicts Stock Returns in Financial Market

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Journal of Systems Science & Complexity 2024年第4期37卷 1638-1652页

作者： HU Xuemei pan Ying LI Xiang School of Mathematics and Statistics Chongqing Technology and Business UniversityChongqing 400067China Chongqing Key Laboratory of Social Economy and Applied Statistics Chongqing 400067China Research Center for Economy of Upper Reaches of the Yangtse River Chongqing Technology and Business UniversityChongqing 400067China

Accurately predicting stock returns is a conundrum in financial *** this conundrum can bring huge economic benefits for investors and also attract the attention of all circles of *** this paper the authors combine semi-varying coefficient model with technical analysis and statistical learning,and propose semi-varying coefficient panel data model with individual effects to explore the dynamic relations between the stock returns from five companies:CVX,DFS,EMN,LYB,and MET and five technical indicators:CCI,EMV,MOM,ln ATR,ln RSI as well as closing price(ln CP),combine semi-parametric fixed effects estimator,semi-parametric random effects estimator with the testing procedure to distinguish fixed effects(FE) from random effects(RE),and finally apply the estimated dynamic relations and the testing set to predict stock returns in December 2020 for the five *** proposed method can accommodate the varying relationship and the interactive relationship between the different technical indicators,and further enhance the prediction accuracy to stock returns.

关键词： Fixed effects random effects semi-varying coefficient panel data model stock returns technical indicators

人眼安全激光用Er:YAG陶瓷的致密化、显微结构与光学性能

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硅酸盐学报 2013年第10期41卷 1323-1330页

作者：刘强刘婧李江曾燕萍巴学巍潘裕柏程晓农郭景坤江苏大学材料科学与工程学院江苏镇江210031 中国科学院上海硅酸盐研究所透明光功能无机材料重点实验室上海200050

以高纯商业Y2O3、α-Al2O3和Er2O3粉体为原料,以TEOS(正硅酸乙酯)和MgO为烧结助剂,采用固相反应和真空烧结技术制备了0.5%Er:YAG透明陶瓷,并对样品的致密化行为、显微结构演化和光学性能进行了系统的研究。结果表明:1760℃烧结的Er:YAG... 详细信息

以高纯商业Y2O3、α-Al2O3和Er2O3粉体为原料,以TEOS(正硅酸乙酯)和MgO为烧结助剂,采用固相反应和真空烧结技术制备了0.5%Er:YAG透明陶瓷,并对样品的致密化行为、显微结构演化和光学性能进行了系统的研究。结果表明:1760℃烧结的Er:YAG透明陶瓷(保温时间50 h)的结构均匀致密,平均晶粒尺寸约为30μm,几乎没有晶界和晶内气孔。厚度为4 mm的Er:YAG陶瓷样品在1 200 nm处的直线透过率高达83.2%,样品的气孔率低达1.96×10–6。

关键词：稀土离子掺杂钇铝石激光陶瓷固相反应烧结显微结构光学性能

Channel Estimation for Reconfigurable Intelligent Surface Aided Multiuser Millimeter-Wave/THz Systems

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China Communications 2024年第3期21卷 91-103页

作者： Chu Hongyun pan Xue Li Baijiang School of Communications and Information Engineering Xi’an University of Posts and TelecommunicationsXi’an 710121China

It is assumed that reconfigurable intelligent surface(RIS)is a key technology to enable the potential of mmWave *** passivity of the RIS makes channel estimation difficult because the channel can only be measured at the transceiver and not at the *** this paper,we propose a novel separate channel estimator via exploiting the cascaded sparsity in the continuously valued angular domain of the cascaded channel for the RIS-enabled millimeter-wave/Tera-Hz systems,i.e.,the two-stage estimation method where the cascaded channel is separated into the base station(BS)-RIS and the RIS-user(UE)***,we first reveal the cascaded sparsity,i.e.,the sparsity exists in the hybrid angular domains of BS-RIS and the RIS-UEs separated channels,to construct the specific sparsity structure for RIS enabled multi-user ***,we formulate the channel estimation problem using atomic norm minimization(ANM)to enhance the proposed sparsity structure in the continuous angular domains,where a low-complexity channel estimator via Alternating Direction Method of Multipliers(ADMM)is *** findings demonstrate that the proposed channel estimator outperforms the current state-of-the-arts in terms of performance.

关键词： atomic norm minimization cascaded channel estimation convex optimization mmWave/THz reconfigurable intelligent surface(RIS) sparsity