检索结果-南通市图书馆

维普期刊数据库博看期刊

Digital microstructure insights to phase evolution and thermal flow properties of hydrates by X-ray computed tomography

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2021年第1期64卷 187-202页

作者： zhao zhi ZHOU XiaoPing School of Civil Engineering Chongqing UniversityChongqing 400045China

Natural gas-hydrates are valuable energy resource with rich deposits,and their thermal transport and thermal dynamic mechanical behaviors significantly affect the long-term production process and phase change-based thermal energy storage characteristics of these energy *** paper aims to propose novel relations to predict the thermophysical properties,to investigate the hydrate phase evolution in microstructures,and to study the thermal transport and thermal dynamic mechanical *** formation experiments in sandpack samples and ultrasonic wave tests are conducted with the aid of X-ray CT *** microstructures models and variables are defined to describe the hydrate phase evolution,and novel relations are proposed to accurately predict the thermophysical properties based on the microporosity and ultrasonic wave *** thermal transport and thermal dynamic mechanical properties in microstructures with hydrate,water,residuary pore and grain phases are *** show that the average errors of porosity,P-wave and S-wave velocities between the experimental data and computed results by the proposed relations are less than 5%,indicating the accuracy and reliability of the proposed *** temperature fraction decreases with increasing underground temperature and decreasing hydrate *** thermal stress and thermal displacement increase as temperature and hydrate saturation *** are strong anisotropy for the temperature fraction,thermal stress and thermal displacement during the thermal transport of hydrates.

关键词： X-ray computed tomography imaging hydrate phase evolution transport properties effective thermal conductivity thermal-mechanical properties

Combining SVM and CHMM classifiers for porno video recognition

在线全文

学校读者我要写书评

暂无评论

The Journal of China Universities of Posts and Telecommunications 2012年第3期19卷 100-106页

作者： zhao zhi-cheng School of Information and Communication Engineering Beijing University of Posts and Telecommunications Beijing 100876 China Beijing Key Laboratory of Network System and Network Culture Beijing University of Posts and Telecommunications Beijing 100876 China

Pomo video recognition is important for Intemet content monitoring. In this paper, a novel pomo video recognition method by fusing the audio and video cues is proposed. Firstly, global color and texture features and local scale-invariant feature transform （SIFT） are extracted to train multiple support vector machine （SVM） classifiers for different erotic categories of image frames. And then, two continuous density hidden Markov models （CHMM） are built to recognize porno sounds. Finally, a fusion method based on Bayes rule is employed to combine the classification results by video and audio cues. The experimental results show that our model is better than six state-of-the-art methods.

关键词： pomo video recognition SVM keyframe CHMM audio

P-symmetric Subharmonic Solutions for Nonlinear Hamiltonian Systems

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2024年第6期40卷 1388-1408页

作者： Duan zhi ZHANG zhi Hao zhao School of Mathematical Sciences Nankai UniversityTianjin 300071P.R.China

In this paper,we prove that for each positive k≡1 mod m there exists a P-symmetric kmτ-periodic solution xk for asymptotically linear mτ-periodic Hamiltonian systems,which are nonautonomous and endowed with a *** the P-symmetric Hamiltonian function is semi-positive,one can prove,under a new iteration inequality of the Maslov-type P-index,that xk_(1) and xk_(2) are geometrically distinct for k_(1)/k_(2)≥(2n+1)m+1;and xk_(1),xk_(2) are geometrically distinct for k_(1)/k_(2)≥m+1 provided xk_(1) is non-degenerate.

关键词： P-symmetric subharmonic Hamiltonian systems Maslov-type index theory iteration inequality asymptotically linear

Measuring the anisotropies in astrophysical and cosmological gravitational-wave backgrounds with Taiji and LISA networks

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2024年第12期67卷 61-69页

作者： zhi-Chao zhao Sai Wang Department of Applied Physics College of ScienceChina Agricultural UniversityBeijing 100083China Theoretical Physics Division Institute of High Energy PhysicsChinese Academy of SciencesBeijing 00049China

We investigate the capabilities of space-based gravitational-wave detector networks,specifically Taiji and LISA,to measure the anisotropies in stochastic gravitational-wave background(SGWB),which are characterized by the angular power *** find that a detector network can improve the measurement precision of anisotropies by at most fourteen orders of magnitude,depending on the angular *** doing so,we can enhance our understanding of the physical origins of SGWB,both in astrophysical and cosmological *** assess the prospects of the detector networks for measuring the parameters of angular power *** further find an inevitable effect of cosmic variance,which can be suppressed by a better angular resolution,strengthening the importance of configuring detector *** findings also suggest a potential detection of the kinematic dipole due to Doppler boosting of SGWB.

关键词： stochastic gravitational-wave background anisotropy space-based detector network

Stochastic gravitational wave background due to gravitational wave memory

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2022年第11期65卷 132-139页

作者： zhi-Chao zhao Zhoujian Cao Institute for Frontiers in Astronomy and Astrophysics Beijing Normal UniversityBeijing102206China Department of Astronomy Beijing Normal UniversityBeijing100875China School of Fundamental Physics and Mathematical Sciences Hangzhou Institute for Advanced StudyUniversity of Chinese Academy of SciencesHangzhou310024China

Gravitational wave memory is an important prediction of general relativity, which has not been detected yet. Amounts of memory events can form a stochastic gravitational wave memory background. Here we find that memory background can be described as a Brownian motion in the condition that the observation time is longer than the averaged time interval between two successive memory events. We investigate, for the first time, the memory background of binary black hole coalescences. We only consider the spectrum of the memory background for a relatively low frequency range. So we can use the step function to approximate the waveform for each memory event. Then we find that the spectrum is a power law with index –2. And the amplitude of the power law spectrum depends on and only on the merger rate of the binary black holes. Consequently, the memory background not only provides a brand new means to detect gravitational wave memory but also opens a new window to explore the event rate of binary black hole mergers and the gravity theory. Space-based detectors are ideal to detect the gravitational wave memory background which corresponds to supermassive binary black holes. Since gravitational wave memory is only sensitive to the merger stage of binary black hole coalescence, the memory background will be an ideal probe of the famous final parsec problem.

关键词： gravitational wave memory stochastic background

同方期刊数据库

Encoding reprogrammable properties into magneto-mechanical materials via topology optimization

在线全文

学校读者我要写书评

暂无评论

npj Computational Materials 2023年第1期9卷 1770-1780页

作者： zhi zhao Xiaojia Shelly Zhang Department of Civil and Environmental Engineering University of Illinois Urbana-ChampaignUrbanaILUSA Department of Mechanical Science and Engineering University of Illinois Urbana-ChampaignUrbanaILUSA

The properties of materials and structures typically remain fixed after being designed and *** is a growing interest in systems with the capability of altering their behaviors without changing geometries or material constitutions,because such reprogrammable behaviors could unlock multiple functionalities within a single *** introduce an optimization-driven approach,based on multi-objective magneto-mechanical topology optimization,to design magneto-active metamaterials and structures whose properties can be seamlessly reprogrammed by switching on and off the external stimuli *** optimized material system exhibits one response under pure mechanical loading,and switches to a distinct response under joint mechanical and magnetic *** discover and experimentally demonstrate magneto-mechanical metamaterials and metastructures that realize a wide range of reprogrammable responses,including multi-functional actuation responses,adaptable snap-buckling behaviors,switchable deformation modes,and tunable *** proposed approach paves the way for promising applications such as magnetic actuators,soft robots,and energy harvesters.

关键词： deformation optimization topology

Microscopic cracking behaviors of rocks under uniaxial compression with microscopic multiphase heterogeneity by deep learning

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2023年第4期33卷 411-422页

作者： zhi zhao Yundong Shou Xiaoping Zhou School of Civil Engineering Wuhan UniversityWuhan 430072China National Center for International Research on Deep Earth Drilling and Resource Development Faculty of EngineeringChina University of Geosciences(Wuhan)Wuhan 430074China

Cracking behaviors of rocks significantly affect the safety and stability of the explorations of underground space and deep *** understand deeply the microscopic cracking process and mechanical property of rocks,X-ray micro-computed tomography(X-μCT)is applied to capture the rock *** digital color difference UNet(DCD-UNet)-based deep learning algorithm with 3D reconstruction is proposed to reconstruct the multiphase heterogeneity microstructure models of *** microscopic cracking and mechanical properties are studied based on the proposed microstructure-based peridynamic *** show that the DCD-UNet algorithm is more effective to recognize and to represent the microscopic multiphase heterogeneity of *** damage characteristic index of multiphase rocks increases,transgranular cracks in the same grain phase,transgranular and intergranular cracks of pore-grain phase,intergranular and secondary transgranular cracks and transgranular crack between different grains *** ultimate microscopic failure modes of rocks are mainly controlled by the transgranular cracks-based T1-shear,T3-shear,T1-tension,T2-tension and T3-tension failures,and the intergranular cracks-based T1-tension,T1-shear and T3-shear failures under uniaxial compression.

关键词： X-μCT imaging Deep learning Microscopic multiphase heterogeneity Uniaxial compression Transgranular-intergranular cracks

DQNN: Pore-scale variables-based digital permeability assessment of carbonates using quantum mechanism-based machine-learning

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2022年第2期65卷 458-469页

作者： zhao zhi ZHOU XiaoPing QIAN QiHu School of Civil Engineering Wuhan UniversityWuhan 430072China School of Civil Engineering Chongqing UniversityChongqing 400045China State Key Laboratory of Disaster Prevention and Mitigation of Explosion and Impact PLA University of Science and TechnologyNanjing 210014China

Permeability is a key parameter of rock reservoirs, suggesting the flow characteristics of rock reservoirs. Permeability prediction of carbonate reservoirs is still a great challenge due to its complex pore network and wide range permeability. This work is to establish a digital quantum mechanism-based neural network(DQNN) to study the permeability using the digital porosity,coordination number and pore network size. Experiments and artificial neural network methods(ANN) are applied to validate the accuracy of the proposed DQNN method. In these methods, the pore-scale variables extracted from the micro-CT images of200 carbonate samples are applied. Results show that the permeabilities obtained from experimental, artificial neural network and DQNN methods agree well with each other. Digital pore size, pore throat size and length are better parameters, while coordination number and porosity are relatively secondary parameters for permeability descriptions of carbonate *** with the ANN method, the proposed DQNN method is superior in low computation time and high ability for complicated problems.

关键词： permeability estimation quantum mechanism machine-learning model micro-pore network carbonates

Multivariate statistical analysis for the surface water quality of the Luan River,China

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第1期10卷 142-148页

作者： zhi-wei zhao Fu-yi CUI State Key Laboratory of Urban Water Resource and Environment Harbin Institute of Technology Harbin 150090 China

In order to analyze the characteristics of surface water resource quality for the reconstruction of old water treatment plant,multivariate statistical techniques such as cluster analysis and factor analysis were applied to the data of Yuqiao Reservoir-surface water resource of the Luan River,*** results of cluster analysis demonstrate that the months of one year were divided into 3 groups and the characteristic of clusters was agreed with the seasonal characteristics in North *** factors were derived from the complicated set using factor *** 1 included turbidity and chlorophyll,which seemed to be related to the anthropogenic activities;factor 2 included alkaline and hardness,which were related to the natural characteristic of surface water;and factor 3 included Cl and NO2-N affected by mineral and agricultural *** sinusoidal shape of the score plots of the three factors shows that the temporal variations caused by natural and human factors are linked to seasonality.

关键词： Surface water quality Cluster analysis Factor analysis Temporal variation of scores