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A time−space porosity computational model for concrete under sulfate attack

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Frontiers of Structural and Civil Engineering 2023年第10期17卷 1571-1584页

作者： Hui song Jiankang CHEN Jiangxi Provincial Key Laboratory of Hydraulic&Civil Engineering Infrastructure Security Nanchang Institute of TechnologyNanchang 330099China Zhejiang Provincial Engineering Research Center for the Safety of Pressure Vessel and Pipeline Ningbo UniversityNingbo 315211China Ningbo University Donghai Academy Ningbo 315211China

The deterioration of the microscopic pore structure of concrete under external sulfate attack(ESA)is a primary cause of ***,little effort has been invested in exploring the temporal and spatial development of the porosity of concrete under *** study proposes a mechanical–chemical model to simulate the spatiotemporal distribution of the porosity.A relationship between the corrosion damage and amount of ettringite is proposed based on the theory of volume *** addition,the expansion strain at the macro-scale is obtained using a stress analysis model of composite concentric sphere elements and the micromechanical mean-field ***,considering the influence of corrosion damage and cement hydration on the diffusion of sulfate ions,the expansion deformation and porosity space−time distribution are obtained using the finite difference *** results demonstrate that the expansion strains calculated using the suggested model agree well with previously reported experimental ***,the tricalcium aluminate concentration,initial elastic modulus of cement paste,corrosion damage,and continuous hydration of cement significantly affect concrete under *** proposed model can forecast and assess the porosity of concrete covers and provide a credible approach for determining the residual life of concrete structures under ESA.

关键词： expansion deformation porosity internal expansion stress external sulfate attack mechanical–chemical coupling model

A TVD Type Wavelet-Galerkin Method for Hamilton-Jacobi Equations

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Acta Mathematicae Applicatae Sinica 2007年第2期23卷 303-310页

作者： Ling-yan Tang song-he song Department of Mathematics and System Science Science School National University of Defense Technology Hunan 410073 China

In this paper, we use Daubechies scaling functions as test functions for the Galerkin method, and discuss Wavelet-Galerkin solutions for the Hamilton-Jacobi equations. It can be proved that the schemes are TVD schemes. Numerical tests indicate that the schemes are suitable for the Hamilton-Jacobi equations. Furthermore, they have high-order accuracy in smooth regions and good resolution of singularities.

关键词： Hamilton-jacobi equation wavelet-galerkin method daubechies wavelet TVD method

Nonlocal stress gradient formulation for damping vibration analysis of viscoelastic microbeam in thermal environment

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Applied Mathematics and Mechanics(English Edition) 2023年第5期44卷 773-786页

作者： Hai QING Huidiao song State Key Laboratory of Mechanics and Control for Aerospace Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China

An integral nonlocal stress gradient viscoelastic model is proposed on the basis of the integral nonlocal stress gradient model and the standard viscoelastic model,and is utilized to investigate the free damping vibration analysis of the viscoelastic BernoulliEuler microbeams in thermal ***'s principle is used to derive the differential governing equations and corresponding boundary *** integral relations between the strain and the nonlocal stress are converted into a differential form with constitutive *** size-dependent axial thermal stress due to the variation of the environmental temperature is derived *** Laplace transformation is utilized to obtain the explicit expression for the bending deflection and *** the boundary conditions and constitutive constraints,one can get a nonlinear equation with complex coefficients,from which the complex characteristic frequency can be determined.A two-step numerical method is proposed to solve the elastic vibration frequency and the damping *** effects of length scale parameters,viscous coefficient,thermal stress,vibration order on the vibration frequencies,and critical viscous coefficient are investigated numerically for the viscoelastic Bernoulli-Euler microbeams under different boundary conditions.

关键词： damping vibration size effect integral nonlocal stress gradient model standard viscoelastic model Laplace transformation

A Note for Estimation About Average Differential Entropy of Continuous Bounded Space-Time Random Field

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Chinese Journal of Electronics 2022年第5期31卷 793-803页

作者： song Zhanjie ZHANG Jiaxing Georgia Tech Shenzhen Institute Tianjin University Tianjin Key Laboratory of Brain-Inspired Intelligence Technology Tianjin University School of Mathematics Tianjin University

In this paper, we mainly study the discrete approximation about average differential entropy of continuous bounded space-time random field. The estimation of differential entropy on random variable is a classic problem, and there are many related studies. Space-time random field is a theoretical extension of adding random variables to space-time parameters, but studies on discrete estimation of entropy on space-time random field are relatively few. The differential entropy forms of continuous bounded space-time random field and discrete estimations are discussed, and three estimation forms of differential entropy in the case of random variables are generated in this paper. Furthermore, it is concluded that under the condition that the entropy estimation formula after space-time segmentation converges with probability1, the average entropy in the bounded space-time region can also converge with probability 1, and three generalized entropies are verified respectively. In addition, we also carried out numerical experiments on the convergence of average entropy estimation based on parameters,and the numerical results are consistent with the theoretical results, which indicting further study of the average entropy estimation problem of space-time random fields is significant in the future.

关键词： average differential entropy differential entropy forms average entropy estimation problem random processes entropy estimation formula random variable approximation theory space-time segmentation space-time parameters bounded space-time region entropy continuous bounded space-time random field

From octahedral structure motif to sub-nanosecond phase transitions in phase change materials for data storage

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Science China(Information Sciences) 2018年第8期61卷 132-146页

作者： Zhitang song Sannian song Min ZHU Liangcai WU Kun REN Wenxiong song songling FENG State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Micro-system and Information Technology Chinese Academy of Sciences

Phase change random access memory(PCRAM) has been successfully applied in the computer storage architecture, as storage class memory, to bridge the performance gap between DRAM and Flashbased solid-state drive due to its good scalability, 3 D-integration ability, fast operation speed and compatible with CMOS technology. Focusing on phase change materials and PCRAM for decades, we have successfully developed 128 Mb embedded PCRAM chips, which can meet the requirements of most embedded systems.3 D Xpoint(3 D PCRAM), invented by Intel and Micron, has been regarded as a new breakthrough in the last 25 years since the application of NAND in 1989, which represents state-of-the-art memory *** technology has some remarkable features, such as the confined device structure with 20 nm size, the metal crossbar electrodes to reduce the resistance variations in PCRAM arrays, and the ovonic threshold switching selector that can provide a high drive current and a low leakage current. A good understanding of phase change mechanism is of great help to design new phase change materials with fast operation speed,low power consumption and long-lifetime. In this paper, we firstly review the development of PCRAM and different understandings on phase change mechanisms in recent years, and then propose a new view on the mechanism, which is based on the octahedral structure motifs and vacancies. Octahedral structure motifs are generally found in both amorphous and crystalline phase change materials. They are considered to be the basic units during phase transition, which are severely defective in the amorphous phase. These configurations turn into more ordered ones after minor local rearrangements, the growth of which results in the crystallization of rocksalt(RS) phase with a large amount of vacancies in the cation sites. Further driven by thermodynamic driving force, these vacancies move and layer along certain directions; consequently, the metastable RS structure transforms in

关键词： phase change memory phase change materials octahedral structure motif fast crystallization speed phase change mechanism

Numerical study on the optimal power distribution of server racks in a data center

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Building Simulation 2023年第6期16卷 983-995页

作者： MengXuan song Kai Chen School of Energy and Materials Shanghai Key Laboratory of Engineering Materials Application and EvaluationShanghai Polytechnic UniversityShanghai201209China Shanghai Thermophysical Properties Big Data Professional Technical Service Platform Shanghai Engineering Research Center of Advanced Thermal Functional MaterialsShanghai201209China Key Laboratory of Enhanced Heat Transfer and Energy Conservation of the Ministry of Education School of Chemistry and Chemical EngineeringSouth China University of TechnologyGuangzhou510640China

Data centers,as the infrastructure of all information services,cost tremendous amount of *** the hot spot temperature in the data center room is benefit to prevent overheating of devices,and to increase cooling system *** this paper,we study the problem of optimal power distribution among racks for minimal hot spot *** temperature rise matrix(TRM)model is used for the purpose of fast estimation of the thermal *** accuracy of the model is evaluated by conducting numerical simulations of computational fluid dynamics(CFD).Using the TRM model,optimal distributing of heating power is converted into a linear programming problem,which can be solved by highly efficient algorithms,such as ***,with realistic constraints including rack idle power and power upper limit,an iteration method is proposed to calculate the optimal power distribution along with the optimal on/off states of the *** solutions are discussed and validated by comparing with CFD *** show that the TRM model is acceptable in evaluating temperature rises in the forced-convection-dominated scenarios,and the proposed method is able to obtain optimal power distributions under various levels of total power demand.

关键词： data center numerical simulation temperature rising matrix power distribution optimization

Possible Involvement of Reactive Oxygen Species Scavenging Enzymes in Desiccation Sensitivity of Antiaris toxicaria Seeds and Axes

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Journal of Integrative Plant Biology 2008年第12期50卷 1549-1556页

作者： Hong-Yan Cheng song-Quan song Institute of Botany the Chinese Academy of Sciences Beijing 100093 China

The relationships among desiccation sensitivities of Antiaris toxicaria seeds and axes, changes in activities of superoxide dismutase （SOD）, ascorbate peroxidase （APX）, catalase （CAT）, glutathione reductase （GR） and dehydroascorbate reductase, （DHAR）, production rate of superoxide radical （.O2^-）, and the contents of hydrogen peroxide （H2O2） and thiobarbituric acid （TBA）-reactive substance were studied. Desiccation tolerance of seeds and axes decreased with dehydration. Desiccation tolerance of axes was higher than that of seeds, and that of epicotyls was higher than radicles. Activities of SOD, CAT and DHAR of seeds increased during the initial phase of dehydration, and then decreased with further dehydration, whereas activities of APX and GR decreased with dehydration. These five enzyme activities of axes, however, increased during the initial phase of dehydration, and then decreased with further dehydration. The rate of superoxide radical production, and the contents of H2O2 and TBA-reacUve products of seeds and axes gradually increased with dehydration. These results show that the A. toxicaria seed is a typical recalcitrant seed. Loss of desiccation tolerance in seeds and axes was correlated with the increase in .O2- production rate, content of H2O2 and TBA-reactive products, and the decline of antioxidant enzyme activities of seeds and axes.

关键词： Antiaris toxicaria antioxidant enzyme content of H2O2 and thiobarbituric acid-reactive product O2^- production rate recalcitrant seed.

Species and Organ Diversity in the Effects of Hydrogen Peroxide on Superoxide Dismutase Activity In Vitro

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Journal of Integrative Plant Biology 2006年第6期48卷 672-678页

作者： Hong-Yan Cheng song-Quan song Xishuangbanna Tropical Botanical Garden the Chinese Academy of Sciences Mengla Yunnan 666303 China Institute of Botany the Chinese Academy of Sciences Beijing 100093 China

Superoxlde dlsmutase （SOD） is ubiquitous in aerobic organisms and constitutes the first link In the enzyme scavenging system of reactive oxygen species. In the present study, species and organ diversity of SOD activity In a solution and In an in-gel assay system, as well as the effects of hydrogen peroxide （H202） on SOD activity, were Investigated. In a solution assay system, SOD activity of jackfruIt root, shoot, leaves, axes, and cotyledons, of maize embryos and endosperms, of mung bean leaves and seeds, of sacred lotus axes and cotyledons, and of rice and wheat leaves was Increased by 1-15 mmol/L H2O2. However, SOD activity In rice root and seeds, maize roots and leaves, mung bean roots and shoots, and wheat seeds was decreased by 1-15 mmol/L H2O2. The SOD activity of wheat root and soybean roots, leaves, axes, and cotyledons was Increased by 1-4 mmol/L H2O2, but was decreased by concentrations of H2O2 〉4 mmol/L. The SOD activity of soybean shoots was not affected by 1-15 mmol/L H2O2. The SOD activity In crude mltochondrla of jackfruIt, maize, and upas seeds, as well as In purified mitochondria of jackfruIt, was also Increased by 1-15 mmol/L H2O2. In the In-gel assay system, the SOD In jackfruIt cotyledons was comprised of Mn-SOD, Cu/Zn-SOD, and Fe-SOD, the crude mltochondria of jackfruit seeds and maizes embryo was comprised of Mn-SOD and Cu/ Zn-SOD, and the crude mltochondria of maize seeds was comprised of Mn-SOD only. In the present study, H2O2 markedly Inhibited Cu/Zn-SOD and Fe-SOD activity.

关键词： hydrogen peroxide inhibitor informative in-gel assay system solution assay system species and organ diversity superoxide dismutase activity.

Identification of Linear Systems Using Binary Sensors with Random Thresholds

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Journal of Systems Science & Complexity 2024年第3期37卷 907-923页

作者： HUANG Zhiyong song Qijiang School of Mathematics Renmin University of ChinaBeijing 100872China School of Mathematics Sino-French InstituteRenmin University of ChinaBeijing 100872China

In this paper,the problem of identifying autoregressive-moving-average systems under random threshold binary-valued output measurements is *** the help of stochastic approximation algorithms with expanding truncations,the authors give the recursive estimates for the parameters of both the linear system and the binary *** reasonable conditions,all constructed estimates are proved to be convergent to the true values with probability one,and the convergence rates are also established.A simulation example is provided to justify the theoretical results.

关键词： α-mixing binary sensor quantized system stochastic approximation stochastic thresh-old strongly consistent system identification