检索结果-南通市图书馆

Simulation study on cavity growth in ductile metal materials under dynamic loading

在线全文

学校读者我要写书评

暂无评论

Frontiers of physics 2013年第4期8卷 394-404页

作者： Ai-guo Nu Guang-cai zhang Yang-Jun Ying Xi-Jun Yu National Key Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics P. O. Box 8009-26 Beijing 100088 China

Cavity growth in ductile metal materials under dynamic loading is investigated via the material point method. Two typical cavity effects in the region subjected to rarefaction wave are identified：（i） part of material particles flow away from the cavity in comparison to the initial loading velocity, （ii） local regions show weaker negative or even positive pressures. Neighboring cavities interact via coalescence of isobaric contours. The growth of cavity under tension shows staged behaviors. After the initial slow stage, the volume and the dimensions in both the tensile and transverse directions show linear growth rate with time until the global tensile wave arrives at the upper free surface. It is interesting that the growth rate in the transverse direction is faster than that in the tensile direction. The volume growth rate linearly increases with the initial tensile velocity. After the global tensile wave passed the cavity, both the maximum particle velocity in the tensile direction and the maximum particle velocity in the opposite direction increase logarithmically with the initial tensile speed. The shock wave reflected back from the cavity and compression wave from the free surface induce the initial behavior of interracial instabilities such as the Richtmyer-Meshkov instability, which is mainly responsible for the irregularity in the morphology of deformed cavity. The local temperatures and distribution of hot spots are determined by the plastic work. Compared with the dynamical process, the heat conduction is much slower.

关键词： material point method cavity growth dynamic loading interracial instability

Lattice Boltzmann model for combustion and detonation

在线全文

学校读者我要写书评

暂无评论

Frontiers of physics 2013年第1期8卷 94-110页

作者： Bo Yan Ai-guo Xu Guang-cai zhang Yang-Jun Ying Hua Li National Key Laboratory of Computational Physics Institute of Applied Physics and Co~putational Mathe'maties P. O. Box 8009-26 Beijing 100088 China

In this paper we present a lattice Boltzmann model for combustion and detonation. In this model the fluid behavior is described by a finite-difference lattice Boltzmann model by Gan et al. [Physica A, 2008, 387: 1721]. The chemical reaction is described by the Lee-Tarver model [Phys. Fluids, 1980, 23: 2362]. The reaction heat is naturally coupled with the flow behavior. Due to the separation of time scales in the chemical and thermodynamic processes, a key technique for a successful simulation is to use the operator-splitting scheme. The new model is verified and validated by well-known benchmark tests. As a specific application of the new model, we studied the simple steady detonation phenomenon. To show the merit of LB model over the traditional ones, we focus on the reaction zone to study the non-equilibrium effects. It is interesting to find that, at the von Neumann peak, the system is nearly in its thermodynamic equilibrium. At the two sides of the von Neumann peak, the system deviates from its equilibrium in opposite directions. In the front of von Neumann peak, due to the strong compression from the reaction product behind the von Neumann peak, the system experiences a sudden deviation from thermodynamic equilibrium. Behind the von Neumann peak, the release of chemical energy results in thermal expansion of the matter within the reaction zone, which drives the system to deviate the thermodynamic equilibrium in the opposite direction. From the deviation from thermodynamic equilibrium, Δm*, defined in this paper, one can understand more on the macroscopic effects of the system due to the deviation from its thermodynamic equilibrium.

关键词： lattice Boltzmann method Lee-Tarver model viscous detonation deviation from equilibrium

Steroid hormone 20-hydroxyecdysone disturbs fat body lipid metabolism and negatively regulates gluconeogenesis in Hyphantria cunea larvae

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Insect Science 2023年第3期30卷 771-788页

作者： Sheng-Yu zhang Han Gao Ankarjan Askar Xing-Peng Li guo-cai zhang Tian-Zhong Jing Hang Zou Hao Guan Yun-He Zhao Chuan-Shan Zou School of Forestry Northeast Forestry UniversityHarbinChina Beiua University JilinChia

The steroid hormone 20-hydroxyecdysone(20E)has been described to regulate fat body lipid metabolism in insects,but its accurate regulatory mechanism,especially the crosstalk between 20E-induced lipid metabolism and gluconeogenesis remains largely ***,we specially investigated the effect of 20E on lipid metabolism and gluconeogenesis in the fat body of Hyphantria cunea larvae,a notorious pest in *** analysis showed that a total of 1907 lipid species were identified in the fat body of *** larvae assigned to 6 groups and 48 lipid *** differentially abundant lipids analysis showed a significant difference between 20E-treated and control samples,indicating that 20E caused a remarkable alteration of lipidomics profiles in the fat body of *** *** studies demonstrated that 20E accelerated fatty acidβ-oxidation,inhibited lipid synthesis,and promoted ***,the activities of pyruvate carboxylase,phosphoenolpyruvate carboxykinase,fructose-1,6-bisphosphatase,and glucose-6-phosphatase were dramatically suppressed by 20E in the fat body of *** *** well,the transcriptions of genes encoding these 4 rate-limiting gluconeogenic enzymes were significantly downregulated in the fat body of *** larvae after treatment with *** together,our results revealed that 20E disturbed fat body lipid homeostasis,accelerated fatty acidβ-oxidation and promoted lipolysis,but negatively regulated gluconeogenesis in *** *** findings might provide a new insight into hormonal regulation of glucose and lipid metabolism in insect fat body.

关键词： 20-hydroxyecdysone Hyphantria cunea fat body lipidomics analysis lipid metabolism gluconeogenesis

Value Iteration-Based Distributed Adaptive Dynamic Programming for Multi-Player Differential Game With Incomplete Information

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2025年第2期12卷 436-447页

作者： Yun zhang Yuqi Wang Yunze cai the Department of Automation Shanghai Jiao Tong University the Key Laboratory of System Control and Information Processing Ministry of Education of China the National Key Laboratory of Air-based Information Perception and Fusion

In this paper, a distributed adaptive dynamic programming(ADP) framework based on value iteration is proposed for multi-player differential games. In the game setting,players have no access to the information of others' system parameters or control laws. Each player adopts an on-policy value iteration algorithm as the basic learning framework. To deal with the incomplete information structure, players collect a period of system trajectory data to compensate for the lack of information. The policy updating step is implemented by a nonlinear optimization problem aiming to search for the proximal admissible policy. Theoretical analysis shows that by adopting proximal policy searching rules, the approximated policies can converge to a neighborhood of equilibrium policies. The efficacy of our method is illustrated by three examples, which also demonstrate that the proposed method can accelerate the learning process compared with the centralized learning framework.

关键词： Distributed adaptive dynamic programming incomplete information multi-player differential game (MPDG) value iteration

Experimental study on failure precursory characteristics and moisture content effect of pre-cracked rocks under graded cyclic loading and unloading

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2025年第2期35卷 249-264页

作者： Wei zhang Dongxiao zhang Weiyao guo Baoliang zhang School of Architecture and Engineering Liaocheng UniversityLiaocheng 252000China College of Energy and Mining Engineering Shandong University of Science and TechnologyQingdao 266590China

It is important to analyze the damage evolution process of surrounding rock under different water content for the stability of engineering rock *** on digital speckle correlation(DSCM),acoustic emission(AE)and electromagnetic radiation(EMR),uniaxial hierarchical cyclic loading and unloading tests were carried out on sandstones with different fracture numbers under dry,natural and saturated water content,to explore the fracture propagation,failure precursor characteristics and damage response mechanism under the influence of water content *** results show that with the increase of water content,the peak stress and crack initiation stress decrease gradually,and the decreases are 15.28%-21.11%and 17.64%-23.04%,*** peak strain and crack initiation strain increase gradually,and the increases are 19.85%-44.53%and 19.15%-41.94%,*** precracked rock with different water content is mainly characterized by tensile failure at different loading ***,with the increase of water content,the proportion of shear cracks gradually increases,while acoustic emission events gradually decrease,the dissipative energy and energy storage limits of the rock under peak load gradually decrease,and the charge signal increases significantly,which is because the lubrication effect of water reduces the friction coefficient between crack surfaces.

关键词： Damage mechanisms Pre-cracked rocks Crack propagation Water-rock interaction Graded cyclic loading and unloading

Zooplankton community composition in summers of 2021and 2022 in the northern East China Sea and Yellow Sea,and their linkage with abiotic and biotic factors

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Oceanology and Limnology 2025年第1期43卷 159-176页

作者： Dongjie guo Fang zhang Shuangyan zhang Song SUN CAS Key Laboratory of Marine Ecology and Environmental Sciences Institute of OceanologyChinese Academy of SciencesQingdao 266071China College of Marine Science University of Chinese Academy of SciencesQingdao 266071China Jiaozhou Bay National Marine Ecosystem Research Station Institute of OceanologyChinese Academy of SciencesQingdao 266071China

The northern East China Sea and Yellow Sea are highly dynamic marginal seas,serving as important fishing grounds and primary areas for *** zooplankton community structure,including abundance,biovolume,and normalized biovolume size spectra(NBSS)within this ecosystem in summers 2021 and 2022 was assessed through ZooScan digital imaging *** abundances of zooplankton in summers 2021 and 2022 were 3364.22±2190.53 and 4435.52±2520.06 inds./m^(3),respectively,whereas the corresponding biovolumes were 649.10±519.63 and 1064.86±1254.87 mm^(3)/m^(3),*** copepods as the dominant zooplankton functional group in terms of abundance in both years,while chaetognath and medusae were the dominant groups in terms of *** dominance of medusae and chaetognath in terms of biovolume,along with the flatter slopes of NBSS compared to a stable community,indicated that more energy accumulated in gelatinous organisms within the study *** were significant positive relationships between temperature and tunicates or medusae,with a significantly higher population size observed in summer 2022 than in *** lower abundance and biovolume of zooplankton,mainly of small copepods,in summer 2021 may be related to the larger population size of the large jellyfish and the proliferation of green *** investigation provided basic data and fundamental insights for achieving a comprehensive understanding of zooplankton community structure and their long-term dynamics.

关键词： zooplankton community spatial distribution global warming Nemopilema nomurai Ulva prolifera

Doubly-Fed Pumped Storage Units Participation in Frequency Regulation Control Strategy for New Energy Power Systems Based on Model Predictive Control

在线全文

学校读者我要写书评

暂无评论

Energy Engineering 2025年第2期122卷 765-783页

作者： Yuanxiang Luo Linshu cai Nan zhang School of Electrical Engineering Northeast Electric Power UniversityJilin132012China

Large-scale new energy grid connection leads to the weakening of the system frequency regulation capability,and the system frequency stability is facing unprecedented *** order to solve rapid frequency fluctuation caused by new energy units,this paper proposes a new energy power system frequency regulation strategy with multiple units including the doubly-fed pumped storage unit(DFPSU).Firstly,based on the model predictive control(MPC)theory,the state space equations are established by considering the operating characteristics of the units and the dynamic behavior of the system;secondly,the proportional-differential control link is introduced to minimize the frequency deviation to further optimize the frequency modulation(FM)output of the DFPSU and inhibit the rapid fluctuation of the frequency;lastly,it is verified on theMatlab/Simulink simulation platform,and the results show that the model predictive control with proportional-differential control link can further release the FM potential of the DFPSU,increase the depth of its FM,effectively reduce the frequency deviation of the system and its rate of change,realize the optimization of the active output of the DFPSU and that of other units,and improve the frequency response capability of the system.

关键词： Doubly-fed pumped storage unit model predictive control proportional-differential control link frequency regulation

CHARACTERIZATION, DEVELOPMENT AND EXPLOITATION OF ESTDERIVED MICROSATELLITES IN GOSSYPIUM RAIMONDII ULBRICH

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science Bulletin 2006年第5期51卷 557-561页

作者： WANG Changbiao, guo Wangzhen, cai caiping & zhang Tianzhen National Key Laboratory of Crop Genetics & Germplasm Enhancement, Cotton Research Institute, Nanjing Agricultural University, Nanjing 210095, China National Key Laboratory of Crop Genetics & Germplasm Enhancement Cotton Research Institute Nanjing Agricultural University Nanjing China

Microsatellite DNA or simple sequence repeats (SSRs) can be derived from expressed se- quence tags (ESTs). These markers are important for gene mapping as well as marker-assisted selection (MAS). To develop EST-SSRs for cotton gene map- ping, we selected and characterized functional markers in Gossypium raimondii, which consisted of 58906 non-redundant EST sequences from NCBI. Among them there were 2620 microsatellite se- quences containing 2818 EST-SSRs, which amoun- ted to 4.45% of the non-redundant starting sequence population. This incidence was equivalent to one EST-SSR in every 14.8 kb of G. raimondii genetic material. Among the different motifs ranging from 1 to 6 bp, trinucleotide repeats were most abundant (38.31%), followed by dinucleotide repeats (24.09%) and mononucleotide repeats (23.35%). Among all identified motif types, A/T had the highest frequency (18.67%), followed by AT/TA (14.83%). Among the compound motifs, tandem trinucleotides occurred with the highest frequency (48.65%). In all, we identi- fied 1554 EST-SSRs primer pair sequences. 300 of them were randomly selected to screen the poly- morphisms between the mapping parents G· hirsutum acc. TM-1 and G· barbadense cv. Hai7124, to con- struct linkage groups in cultivated allotetraploid cot- ton. Among them, 129 (43%) primer pairs were found to have polymorphisms. Using these EST-SSRs we can compare EST-SSR distributions among different cotton species and various chromosomal locations.

关键词： Gossypium raimondii Ulbrich EST-SSRs distribution molecular marker polymorphism.

Model tests and numerical analysis of emergency treatment of cohesionless soil landslide with quick-setting polyurethane

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Mountain Science 2025年第1期22卷 110-121页

作者： zhang Zhichao TANG Xuefeng HUANG Rufa cai Zhenjie GAO Anhua Key Laboratory of Geohazard Prevention of Hilly Mountains Ministry of Natural Resources of ChinaFuzhou 350002China Technology Innovation Center for Monitoring and Restoration Engineering of Ecological Fragile Zone in Southeast China Ministry of Natural ResourcesFuzhou 350001China Fujian Construction Research Engineering Consulting Co. Ltd.Fuzhou 350100China Xin Zhongkun Construction Engineering Co. LTDLongyan 364399China Fujian Jiakang Construction Engineering Co. LTDLongyan 364199China

Shotcrete is one of the common solutions for shallow *** works by forming a protective layer with high strength and cementing the loose soil particles on the slope surface to prevent shallow ***,the solidification time of conventional cement paste is long when shotcrete is used to treat cohesionless soil *** idea of reinforcing slope with polyurethane solidified soil(i.e.,mixture of polyurethane and sand)was *** tests and finite element analysis were carried out to study the effectiveness of the proposed new method on the emergency treatment of cohesionless soil *** loading on the crest of the slope was applied step by step until landslide was triggered so as to test and compare the stability and bearing capacity of slope models with different *** simulated slope displacements were relatively close to the measured results,and the simulated slope deformation characteristics were in good agreement with the observed phenomena,which verifies the accuracy of the numerical *** the condition of surcharge loading on the crest of the slope,the unreinforced slope slid when the surcharge loading exceeded 30 k Pa,which presented a failure mode of local instability and collapse at the shallow layer of slope *** reinforced slope remained stable even when the surcharge loading reached 48 k *** displacement of the reinforced slope was reduced by more than 95%.Overall,this study verifies the effectiveness of polyurethane in the emergency treatment of cohesionless soil landslide and should have broad application prospects in the field of geological disasters concerning the safety of people's live.

关键词： Cohesionless soil landslide Polyurethane Emergency treatment Reinforcement effect Model test Finite element analysis