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DEM investigation of strength and critical state behaviours of granular materials under true triaxial loadings

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Particuology 2024年第2期85卷 198-212页

作者： Minyi Zhu Guobin Gong Jun Xia stephen Wilkinson Department of Civil Engineering Xi'an Jiaotong-Liverpool UniversityChina Department of Civil Engineering and Industrial Design University of LiverpoolLiverpoolUK Faculty of Engineering and Information Sciences University of Wollongong in DubaiUnited Arab Emirates

This paper investigates the strength and critical state(CS)behaviours of granular materials via DEM simulations of true triaxial drained tests under three different loading modes including constant b(in-termediate stress ratio)tests with constantσ'1(major principal stress),constant p(mean pressure)and constantσ'3(minor principal stress)*** this end,a series of samples are generated with the same particle size distribution,and with the confining stresses ranging from 100 kPa to 900 *** CS is achieved for all *** the macroscopic behaviours and the microscopic behaviours are examined and compared considering different loading modes,confining stresses and intermediate stress ratios(b).The critical state lines(CSLs)are found to be unique and independent of the loading modes,but dependent on the b *** CSLs with b=0 and b=1 form the two boundaries of CSLs respectively beyond which CSLs under all other b tests cannot go *** different strength criteria are examined and compared in terms of both peak and CS *** Mohr-Coulomb strength criterion is found to be only suitable for axisymmetric loading *** Lade-Duncan criterion is only suitable for describing peak strengths,which is dependent on the loading modes and confining *** Satake criterion and Matsuoka-Nakai criterion are the more appropriate strength criteria for describing CS failures,indicating that the CS values of both the Satake parameter and the Matsuoka-Nakai parameter describe an inherent property that characterizes the CS failure for a given type of *** CS mechanical coordination number is fitted by a curved line for a given b value,which is unique regardless of the loading *** peak and CS values of both major and minor principal fabric tensors decrease with increasing b values,while they increase with increasing b values for the intermediate principal fabric tensor.

关键词： Discrete element method Intermediate stress ratio Dilation Critical state Failure criterion

DCFNet:Discriminant Correlation Filters Network for Visual Tracking

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Journal of Computer Science & Technology 2024年第3期39卷 691-714页

作者：胡卫明王强高晋李兵 stephen Maybank State Key Laboratory of Multimodal Artificial Intelligence Systems Institute of AutomationChinese Academy of Sciences Beijing 100190China Department of Computer Science and Information Systems Birkbeck CollegeLondon WC1E 7HXU.K.

CNN(convolutional neural network)based real time trackers usually do not carry out online network update in order to maintain rapid tracking *** inevitably influences the adaptability to changes in object *** filter based trackers can update the model parameters online in real *** this paper,we present an end-to-end lightweight network architecture,namely Discriminant Correlation Filter Network(DCFNet).A differentiable DCF(discriminant correlation filter)layer is incorporated into a Siamese network architecture in order to learn the convolutional features and the correlation filter *** correlation filter can be efficiently updated *** previous work,we introduced a joint scale-position space to the DCFNet,forming a scale DCFNet which carries out the predictions of object scale and position *** combine the scale DCFNet with the convolutional-deconvolutional network,learning both the high-level embedding space representations and the low-level fine-grained representations for *** adaptability of the fine-grained correlation analysis and the generalization capability of the semantic embedding are complementary for visual *** back-propagation is derived in the Fourier frequency domain throughout the entire work,preserving the efficiency of the *** evaluations on the OTB(Object Tracking Benchmark)and VOT(Visual Object Tracking Challenge)datasets demonstrate that the proposed trackers have fast speeds,while maintaining tracking accuracy.

关键词： correlation filter convolutional neural network(CNN) visual tracking

Role of intravascular ultrasound and optical coherence tomography in intracoronary imaging for coronary artery disease:a systematic review

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Journal of Geriatric Cardiology 2024年第1期21卷 104-129页

作者： Maruf Sarwar stephen Adedokun Mahesh Anantha Narayanan Department of Cardiovascular Sciences White River HealthBatesvilleARUSA Division of Cardiology University of Tennessee at MemphisTNUSA University of Arkansas Medical Sciences Little RockARUSA

Coronary angiography has long been the standard for coronary imaging,but it has limitations in assessing vessel wall anatomy and guiding percutaneous coronary intervention(PCI).Intracoronary imaging techniques like intravascular ultrasound(IVUS)and optical coherence tomography(OCT)can overcome these *** uses ultrasound and OCT uses near-infrared light to visualize coronary pathology in unique ways due to differences in temporal and spatial *** techniques have evolved to offer clinical utility in plaque characterization and vessel assessment during ***-analyses and adjusted observational studies suggest that both IVUS and OCT-guided PCI correlate with reduced cardiovascular risks compared to angiographic guidance *** IVUS demonstrates consistent clinical outcome benefits,OCT evidence is less *** has progressed from early motion detection to high-resolution systems,with smaller compatible *** utilizes near infrared light to achieve unparalleled resolutions,but requires temporary blood clearance for optimal *** visualization and guidance make IVUS and OCT well-suited for higher risk PCI in patients with diabetes and chronic kidney disease by allowing detailed visualization of complex lesions and ensuring optimal stent deployment and positioning in PCI for patients with type 2 diabetes and chronic kidney disease,improving *** and recent advancements in zero-and low-contrast OCT techniques can reduce nephrotoxic contrast exposure,thus helping to minimize PCI complications in these high-risk patient *** and OCT provide valuable insights into coronary pathophysiology and guide interventions precisely compared to angiography *** have comparable clinical outcomes,emphasizing the need for tailored imaging choices based on clinical *** refinement and integration of intravascular imaging will likely play a pivotal role in optimizing coronary interventions and outcomes.

关键词： coronary anatomy limitations

维普期刊数据库

Rapid growth in a large Cambrian apex predator

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National Science Review 2024年第3期11卷 128-136页

作者：吴雨 stephen Pates Daniel Pauly 张兴亮傅东静 State Key Laboratory of Continental Dynamics and Shaanxi Key Laboratory of Early Life and Environment Department of Geology Northwest University Department of Zoology University of Cambridge Institute for the Oceans and Fisheries University of British Columbia Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences

Despite the importance of ontogenetic data on early diverging euarthropods to our understanding of the ecology and evolution of past life, the data are distinctly lacking, as reconstructing life histories of fossil animals is often challenging. Here we report the growth trajectory of frontal appendages of the apex predator Amplectobelua symbrachiata, one of the most common radiodont arthropods from the early Cambrian Chengjiang biota(c. 520 Ma) of China. Analysis of 432 specimens(9.1–137.1 mm length; 1.3–25.6 mm height) reveals that appendages grew isometrically, with an estimated maximum size of the whole animal of c. 90 cm. Individuals grew rapidly compared to extant arthropods, as assessed using the electronic length-frequency analysis(ELEFAN) approach. Therefore, we show that the Cambrian apex predator A. symbrachiata was an extremely fast-growing arthropod, with an unusual life history strategy that formed as part of the escalatory ‘arms race’ that shaped the Cambrian explosion over 500 Ma.

关键词： stem-group Euarthropoda Radiodonta post-embryonic development growth dynamics Cambrian Explosion

A REDUCED ORDER SCHWARZ METHOD FOR NONLINEAR MULTISCALE ELLIPTIC EQUATIONS BASED ON TWO-LAYER NEURAL NETWORKS

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Journal of Computational Mathematics 2024年第2期42卷 570-596页

作者： Shi Chen Zhiyan Ding Qin Li stephen J.Wright Mathematics Department University of Wisconsin-MadisonMadisonWI 53706USA Department of Mathematics University of California-BerkeleyBerkeley CA 94720USA Mathematics Department and Discovery Institute University of Wisconsin-Madison MadisonWI 53706USA Computer Sciences Department University of WisconsinMadisonWI 53706USA

Neural networks are powerful tools for approximating high dimensional data that have been used in many contexts,including solution of partial differential equations(PDEs).We describe a solver for multiscale fully nonlinear elliptic equations that makes use of domain decomposition,an accelerated Schwarz framework,and two-layer neural networks to approximate the boundary-to-boundarymap for the subdomains,which is the key step in the Schwarz ***,the boundary-to-boundary map requires solution of boundary-value elliptic problems on each *** leveraging the compressibility of multiscale problems,our approach trains the neural network offline to serve as a surrogate for the usual implementation of the boundary-to-boundary *** method is applied to a multiscale semilinear elliptic equation and a multiscale p-Laplace *** both cases we demonstrate significant improvement in efficiency as well as good accuracy and generalization performance.

关键词： Nonlinear homogenization Multiscale elliptic problem Neural networks Do-main decomposition

Neuropeptide cholecystokinin:a key neuromodulator for hippocampal functions

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Neural Regeneration Research 2025年第7期20卷 1991-1992页

作者： Fengwen Huang stephen Temitayo Bello Department of Neuroscience City University of Hong KongKowloon TongHong Kong Special Administrative RegionChina Center for Regenerative Medicine and Health Hong Kong Institute of Science&InnovationChinese Academy of SciencesHong Kong Special Administrative RegionChina

Spatial memory is crucial for survival within external surroundings and wild *** hippocampus,a critical hub for spatial learning and memory formation,has received extensive investigations on how neuromodulators shape its functions(Teixeira et al.,2018;Zhang et al.,2024).However,the landscape of neuromodulations in the hippocampal system remains poorly understood because most studies focus on classical monoamine neuromodulators,such as acetylcholine,serotonin,dopamine,and *** neuropeptides,comprising the most abundant neuromodulators in the central nervous system,play a pivotal role in neural information processing in the hippocampal ***(CCK),one of the most abundant neuropeptides,has been implicated in regulating various physiological and neurobiological statuses(Chen et al.,2019).CCK-A receptor(CCK-AR)and CCK-B receptors(CCK-BR)are two key receptors mediating the biological functions of CCK,both of which belong to class-A sevenfold transmembrane G protein-coupled receptors(Nishimura et al.,2015).CCK-AR preferentially reacts to sulfated CCK,whereas CCK-BR binds both CCK and gastrin with similar affinities(Ding et al.,2022).The expression patterns of CCK-AR and CCK-BR are distinct,implying that CCK has various functions in target *** instance,CCK-AR is widely expressed in the GI and brain subregions and is hence implicated in the control of digestive function and satiety ***,CCK-BR is abundantly and widely distributed in the central nervous system,which majorly regulates anxiety,learning,and memory(Ding et al.,2022).However,the roles of endogenous CCK and CCK receptors in regulating hippocampal function at electrophysiological and behavioral levels have received less attention.

关键词： abundant functions modulator

Exploring the synergy of the eyebrain connection:neuromodulation approaches for neurodegenerative disorders through transcorneal electrical stimulation

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Neural Regeneration Research 2024年第10期19卷 2097-2098页

作者： Antara Verma stephen K.Agadagba Leanne Lai-Hang Chan Department of Electrical Engineering City University of Hong KongKowloonHong Kong Special Administrative RegionChina Centre for Eye and Vision Research Ltd. Hong Kong Special Administrative RegionChina Pennsylvania State University University ParkPAUSA

The connection and interaction between the eye and the brain are crucial to understanding brain disorders(Marchesi et al.,2021).Both the eye and the brain have a limited regenerative capacity as there are few progenitor cells,and nerve cells do not ***,neurodegeneration implicates irreversible damage to the central nervous system,as observed in several neurodegenerative diseases(Marchesi et al.,2021).

关键词： stimulation degenerative

维普期刊数据库

Effect of austenitizing condition on mechanical properties,microstructure and precipitation behavior of AISI H13 steel

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Journal of Iron and Steel Research(International) 2024年第1期31卷 143-156页

作者： An-gang Ning Yang Liu Rui Gao stephen Yue Ming-bo Wang Han-jie Guo College of Materials Science and Engineering Taiyuan University of TechnologyTaiyuan030024ShanxiChina Department of Mining and Materials Engineering McGill UniversityMontrealQCH3A 0C5Canada ASSAB Tooling Technology(Chongqing)Co. Ltd.Chongqing401120China School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing100083China

The effects of austenitizing temperature(1223,1303,and 1373 K)and holding time(1-1500 s)on the microstructure,mechanical properties,and precipitation behavior of the H13 hot work die steel were *** results indicate a softening phenomenon when H13 steel is austenitized at 1303 K beyond 900 s and 1373 K beyond 600 s,*** the sample held for 1200 s,the tensile strength is found capable of reaching up to 2.2 GPa when quenched from a temperature above 1303 ***,prior-austenite grain size increases with the increase in austenitizing *** kinetic behavior of the precipitates(mainly MC-type carbides)in H13 steel could be elaborated through the principles set forth by the Arrhenius and Avrami ***,the comprehensive strengthening of the H13 steel was discussed in *** results show that the activation energy of the transformed fraction of carbides is higher than that of the diffusion process for common alloying elements(Cr,V,Mo,and Ni)found in the *** suggests that it would be difficult for precipitates to dissolve into the matrix when H13 steel is austenitized at high *** the increasing austenitizing temperature,the precipitation fraction decreases,and the dislocation density *** dislocation strengthening is regarded as the dominant strengthening contributed to yield strength in as-quenched H13 steel.

关键词： H13 steel Austenitizing Mechanical property Precipitation behavior Comprehensive strengthening

Gastroesophageal reflux following peroral endoscopic myotomy for achalasia:Bumps in the road to success

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World Journal of Gastroenterology 2024年第29期30卷 3461-3464页

作者： David Itskoviz stephen David Howard Malnick Kaplan Medical Center Institute of Gastroenterology and HepatologyHebrew University Medical School of JerusalemRehovot 76100Israel Kaplan Medical Center Department of Internal Medicine CHebrew University Medical School of JerusalemRehovot 76100Israel

Achalasia can significantly impair the quality of *** clinical presentation typically includes dysphagia to both solids and liquids,chest pain,and *** can be delayed in patients with atypical presentations,and they might receive a wrong diagnosis,such as gastroesophageal reflux disease(GERD),owing to overlapping symptoms of both *** the cause of achalasia is poorly understood,its impact on the motility of the esophagus and gastroesophageal junction is well *** treatment modalities have been utilized,with the most common being surgical Heller myotomy with concomitant fundoplication and pneumatic balloon ***,peroral endoscopic myotomy(POEM)has gained popularity as an effective treatment for achalasia,despite a relatively high incidence of GERD occurring after treatment compared to other *** magnitude of post-POEM GERD depends on its definition and is influenced by patient and procedure-related *** longterm sequelae of post-POEM GERD are yet to be determined,but it appears to have a benign course and is usually manageable with clinically available *** risk factors for post-POEM GERD and modifying the POEM procedure in selected patients may improve the overall success of this technique.

关键词： Achalasia Per-oral endoscopic myotomy Gastroesophageal reflux Pneumatic dilatation Heller myotomy Proton pump inhibitor Acidic fermentation