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Discrete numerical modeling of granular materials considering crushability

Journal of Mountain Science 2017年第4期14卷 758-770页

作者： QIAN jian-gu gu jian-bo gu Xiao-qiang HUANG Mao-song Key Laboratory of Geotechnieal and Underground Engineering of Ministry of Education Tongji UniversityShanghai 200092China Department of Geotechnical Engineering Tongji UniversityShanghai 200092China

The aim of this study is to numerically investigate the influence of particle breakage on the mechanical behavior of granular materials using a discrete element method(DEM). To enable particle crushing, non-crushable elementary particles are boned together to represents the granular aggregates which can be crushed when the external force exceeds its strength. The flaw of the aggregate was also modeled by randomly distributed void. Single particle crushing tests were carried out to determine the distribution of particle strength. The results of single particle crushing tests illustrate that the simulated single particle fracture strength and pattern agree well with the Weibull's distribution *** oedometer tests, drained monotonic and cyclic triaxial tests were also carried out to investigate the crushing of the aggregates and the associated mechanical behaviors. The effect of confining pressure on the crushing of aggregates and the mechanical behavior was also analyzed. It was found that the peak stress and dilation decrease significantly when particle crushing was *** deformation behavior of the specimen is essentially controlled by two factors: particle rearrangement-induced dilation and particle crushing-induced contraction. The increase of permanent strain and the reduction of dilation were observed during cyclic loading and they tend to reach a stable state after a certain number of cycles. The crushing of aggregate is most significant in the first two cycles. The results also indicated that for the same axial strain the volumetric strain and the bound breakage in the cyclic loading tests are significantly larger than that in the monotonic loading tests,especially at high cyclic stress ratio.

关键词： DEM simulation Granular materials Crushing Monotonic and Cyclic triaxial test

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NASTCNN: a spatio-temporal convolutional neural network with non-local attention mechanism for image-induced brain activity pattern recognition

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Optoelectronics Letters 2025年

作者： TAN Xiangxin SHAO Mingxiong ZENG Ke gu Yue School of Computer Science and Engineering， Tianjin University of Technology Engineering Research Center of Learning-Based Intelligent System (Ministry of Education)， Tianjin University of Technology Krembil Research Institute， University Health Network

Deciphering the brain’s visual processing mechanisms has always been a hot topic. Using neural signal patterns to predict the corresponding external visual stimuli is crucial in understanding the interaction of real visual scenes. There are some challenges in the study of image-induced brain activity pattern recognition based on electroencephalogram (EEG)， e.g. how to fully utilize the effective features of EEG signals to improve the classification， and how the frequency and the length of EEG effect the model performance. We design an experimental paradigm that minimizes the interaction between visual stimuli， and propose a spatio-temporal convolutional neural network with non-local attention mechanism (NASTCNN) for image-induced brain activity pattern recognition. The framework utilizes non-local feature extraction operations to realize global information interaction between EEG signals over long distances and enhance the feature expression of some important information. Our model achieves the best performance on both MNIST-EEG and ImageNet-EEG datasets. The classification results are 24.00% and 50.10% respectively， higher than the random probability. We also analyze the effects of different EEG frequency bands and time subsequences of different lengths on the classification performance and which brain regions are activated over time. The results show that when full frequency band and entire length sequence are selected， the classification result is optimal. The occipital region is essential for processing visual tasks， and the temporal region and some frontal regions also play important role in the later stage of visual decoding. This research can help us better understand the visual processing mechanism of the brain.

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An approach to the capsule endoscopic robot with active drive motion

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2011年第3期12卷 223-231页

作者： Da-qiang gu yong ZHOU Department of Mechanical Engineering Zhejiang University Hangzhou 310027 China

Commercialized capsule-type endoscopes move passively by peristaltic waves (and gravity),which makes it difficult for doctors to diagnose the areas of interest more thoroughly and *** resolve this problem of passivity,it is necessary to find a special locomotion principle,which fits the gastrointestinal (GI) *** this paper,a legged locomotive mechanism with shape memory alloy (SMA) actuation based on the peristaltic principle is proposed,and then the structure of the locomotion mechanism is *** on the preliminary results,the design,modeling,and fabrication of an SMA microactuation concept for application in an endoscopic capsule are given,as well as the SMA spring and legged component design,which is the core section of the system *** used the pseudo-rigid-body model (PRBM) to analyze nonlinear and large deflections of the SMA legged ***,a prototype endoscope with an SMA spring and six legged components was designed and *** is 15 mm in diameter and 33 mm in total length,with a hollow space to house other parts needed for endoscopy such as a camera,a radio frequency (RF) module,and *** testing,the locomotive mechanism was effective in a plastic tube environment.

关键词： Capsular endoscopy Shape memory alloy (SMA) Microactuation Locomotion

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Characterization and evaluation of UV-irradiation aging of urushi by micro-UV/Py-GC/MS system

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Science China(Technological Sciences) 2023年第8期66卷 2258-2270页

作者： WANG Na gu An LEI yong Department of Conservation Science The Palace MuseumBeijing 100009China

Lacquer is the main raw material of lacquerware,while UV-irradiation is an important factor leading to its *** order to investigate the aging behavior of urushi lacquer film under UV-irradiation,and to propose parameters that can be used to evaluate its aging degree,the micro-UV/Py-GC/MS system has been applied in the present work to enrich and identify volatile products released by urushi film during aging on the one hand,and to investigate micro-amount and conventional urushi films with different aging degrees on the other hand,in addition,representative historical samples have also been *** products released by urushi film demonstrate that during UV-irradiation,polysaccharides wrapping urushiol polymer would be first degraded to generate furans and alcohols,and then urushiol polymer would undergo photo-oxidation and break of molecular chain,mainly generating oxidation products including aldehydes,organic acids,and ketones,as well as a small number of alkyl benzenes and ***-GC/MS analysis of micro-amount urushi films with different aging degrees indicates that UVirradiation is more destructive to aliphatic chains in urushiol polymer,but it also can accelerate the polymerization of microamount urushi ***-GC/MS analysis of conventional urushi films indicates that with the increase of aging degree,the total chromatographic peak area ratio of hydrocarbons to benzene derivatives gradually increases,the peak area ratio of 3-pentadecenyl-catechol to 3-pentadecyl-catechol gradually decreases,and the peak area ratio of aging products of urushiol to 3-pentadecyl-catechol gradually *** above parameters were further used to evaluate the aging degree of two urushicontained samples separately collected from the surface and interior of a carved lacquer panel in the Forbidden City,and evaluation results are in accord with the natural aging law and further verify the reliability of the proposed *** results of the pre

关键词： urushi UV-irradiation aging micro-UV/Py-GC/MS aging degree evaluation

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Entropy majorization, thermal adiabatic theorem, and quantum phase transitions

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Frontiers of physics 2012年第2期7卷 244-251页

作者： Shi-jian gu (1) 1. Department of Physics and Institute of Theoretical Physics The Chinese University of Hong Kong Hong Kong China

Let a general quantum many-body system at a low temperature adiabatically cross through the vicinity of the system＇s quantum critical point. We show that the system＇s temperature is signif- icantly suppressed due to both the entropy majorization theorem in quantum information science and the entropy conservation law in reversible adiabatic processes. We take the one-dimensional transverse-field Ising model and the spinless fermion system as concrete examples to show that the inverse temperature might become divergent around the systems＇ critical points. Since the temper- ature is a measurable quantity in experiments, it can be used, via reversible adiabatic processes at low temperatures, to detect quantum phase transitions in the perspectives of quantum information science and quantum statistical mechanics.

关键词： quantum phase transition entropy majorization

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Cortical Mechanisms of Multisensory Linear Self-motion Perception

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Neuroscience Bulletin 2023年第1期39卷 125-137页

作者： Luxin Zhou yong gu CAS Center for Excellence in Brain Science and Intelligence Technology Institute of NeuroscienceChinese Academy of SciencesShanghai200031China University of Chinese Academy of Sciences Beijing100049China

Accurate self-motion perception,which is critical for organisms to survive,is a process involving multiple sensory *** two most powerful cues are visual(optic flow)and vestibular(inertial motion).Psychophysical studies have indicated that humans and nonhuman primates integrate the two cues to improve the estimation of self-motion direction,often in a statistically Bayesian-optimal *** the last decade,single-unit recordings in awake,behaving animals have provided valuable neurophysiological data with a high spatial and temporal resolution,giving insight into possible neural mechanisms underlying multisensory self-motion ***,we review these findings,along with new evidence from the most recent studies focusing on the temporal dynamics of signals in different *** show that,in light of new data,conventional thoughts about the cortical mechanisms underlying visuo-vestibular integration for linear self-motion are *** propose that different temporal component signals may mediate different functions,a possibility that requires future studies.

关键词： Multisensory integration Self-motion perception Vestibular Optic flow

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A Framework of Convergence Analysis of Mini-batch Stochastic Projected Gradient Methods

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Journal of the Operations Research Society of China 2023年第2期11卷 347-369页

作者： jian gu Xian-Tao Xiao School of Sciences Dalian Ocean UniversityDalian 116023China School of Mathematical Sciences Dalian University of TechnologyDalian 116023China

In this paper,we establish a unified framework to study the almost sure global convergence and the expected convergencerates of a class ofmini-batch stochastic(projected)gradient(SG)methods,including two popular types of SG:stepsize diminished SG and batch size increased *** also show that the standard variance uniformly bounded assumption,which is frequently used in the literature to investigate the convergence of SG,is actually not required when the gradient of the objective function is Lipschitz ***,we show that our framework can also be used for analyzing the convergence of a mini-batch stochastic extragradient method for stochastic variational inequality.

关键词： Stochastic projected gradient method Variance uniformly bounded Convergence analysis

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Across-wind loads and effects of super-tall buildings and structures

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Science China(Technological Sciences) 2011年第10期54卷 2531-2541页

作者： gu Ming QUAN yong State Key Laboratory of Disaster Reduction in Civil Engineering Tongji University Shanghai 200092 China

Across-wind loads and effects have become increasingly important factors in the structural design of super-tall buildings and structures with increasing height. Across-wind loads and effects of tall buildings and structures are believed to be excited by inflow turbulence, wake, and inflow-structure interaction, which are very complicated. Although researchers have been focusing on the problem for over 30 years, the database of across-wind loads and effects and the computation methods of equivalent static wind loads have not yet been developed, most countries having no related rules in the load codes. Research results on the across-wind effects of tall buildings and structures mainly involve the determination of across-wind aerodynamic forces and across-wind aerodynamic damping, development of their databases, theoretical methods of equivalent static wind loads, and so on. In this paper we first review the current research on across-wind loads and effects of super-tall buildings and structures both at home and abroad. Then we present the results of our study. Finally, we illustrate a case study in which our research results are applied to a typical super-tall structure.

关键词： super-tall building and structure across-wind aerodynamic force across-wind aerodynamic damping across-wind effects across-wind quivalent static wind loads case study

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Fidelity spectrum:A tool to probe the property of a quantum phase

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Chinese Physics B 2016年第3期25卷 84-90页

作者： Wing Chi Yu Shi-jian gu Department of Physics and ITR The Chinese University of Hong KongHong KongChina

Fidelity measures the similarity between two states and is widely adapted by the condensed matter community as a probe of quantum phase transitions in many-body systems. Despite its success in witnessing quantum critical points, information about the fine structure of a quantum phase one can get from this approach is still limited. Here, we proposed a scheme called fidelity spectrum, By studying the fidelity spectrum, one can obtain information about the characteristics of a phase. In particular, we investigated the spectra in the one-dimensional transverse-field Ising model and the two- dimensional Kitaev model on a honeycomb lattice. It was found that the sPectra have qualitative differences in the critical and non-critical regions of the two models. From the distributions of them, the dominating k modes in a particular phase could also be captured.

关键词： quantum phase.transitions quantum information quanfized spin models

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GdCl₃ abates hepatic ischemia-reperfusion injury by inhibiting apoptosis in rats

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Hepatobiliary & Pancreatic Diseases International 2009年第5期8卷 518-523页

作者： jian-Yi Li Xi gu Wen-Hai Zhang Shi Jia yong Zhou Department of General Surgery Shengjing Hospital China Medical University Shenyang 110004 China.

BACKGROUND:Gadolinium chloride(GdCl3)is a specific inhibitor of Kupffer cells(KCs),which are important promoters of various liver *** is therefore of interest to explore the role of KCs in liver ischemia-reperfusion injury and their relations with apoptosis caused by ischemia-reperfusion injury. METHODS:One hundred male Wistar rats(190-210 g, 6-7 weeks old)were divided into two groups at random, GdCl3 group and control *** were collected at 0.5,1,6,12,and 24 hours from each group after *** alanine aminotransferase(ALT)and aspartate aminotransferase(AST)were measured by an automatic biochemical ***-αin serum was measured by enzyme-linked immunosorbent assay(ELISA). Malondialdehyde(MDA)in the liver mitochondria was measured by a colorimetric *** changes in the liver and immunohistochemical staining for caspase-3 were observed under an optical *** ratio of apoptotic cells was measured by TdT-mediated dUTP nick-end labeling(TUNEL),and ultrastructural features of apoptosis were observed with a transmission electron microscope(TEM). RESULTS:The levels of ALT in the GdCl3 group were lower than those in the control group after reperfusion for 0.5, 1,6 and 12 hours(P<0.05);and the levels of AST in the GdCl3 group were lower than those in the control group after reperfusion for 6 and 12 hours(P<0.05).The levels of TNF-αin the GdCl 3 group were lower than those in the control group after reperfusion for each time(P<0.05). The concentrations of MDA after reperfusion in the GdCl3 group were lower than those in the control group after reperfusion for 6,12 and 24 hours(P<0.05).After reperfusion for 0.5,1,6 and 12 hours,the integral optical density(IOD)of caspase-3-positive cells was lower in theGdCl3 group than in the control group(P<0.05).After reperfusion for 1,6,and 12 hours,the IOD of cells stained by TUNEL in the GdCl3 group was lower than that in the control group(P<0.05). CONCLUSIONS:GdCl3

关键词： gadolinium chloride Kupffer cell ischemia-reperfusion injury caspase-3 apoptosis

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