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Dynamic tensile behaviors of AZ31B magnesium alloy processed by twin-roll casting and sequential hot rolling

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Transactions of Nonferrous Metals Society of China 2016年第11期26卷 2846-2857页

作者： Ping ZHOU Elmar BEEH Meng WANG Horst E. FRIEDRICH German Aerospace Center (DLR) Institute of Vehicle Concepts Pfaffenwaldring 38-40 70569 Stuttgart Germany

The dynamic tensile behavior of twin-roll cast-rolled and hot-rolled AZ31B magnesium alloy was characterized over strainrates ranging from 0.001 to 375 s^-1 at room temperature using an elaborate dynamic tensile testing method, and the relationshipbetween its mechanical properties and microstructures. It is observed that the sheet has a strong initial basal fiber texture andmechanical twinning becomes prevalent to accommodate the high-rate deformation. The yield strength and ultimate tensile strengthmonotonically increase with increasing the strain rate, while the strain hardening exponent proportionally decreases with increasingthe strain rate due to twinning-induced softening. The total elongation at fracture distinctly decreases as the strain rate increasesunder quasi-static tension, while the effect of strain rate on the total elongation is not distinct under dynamic tension. Fractographicanalysis using a scanning electron microscope reveals that the fracture is a mixed mode of ductile and brittle fracture.

关键词： magnesium alloy twin-roll casting dynamic tensile strain-rate sensitivity fractography

Adapting Backward Error Recovery to Parallel Real Time Systems

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Journal of Computer Science & Technology 1992年第3期7卷 257-267页

作者：周笛 Lehrstuhl für Prozessrechner der Technischen Universitat München Franz-Joseph Str. 38/III 8000 München 40 Germany

The problem of adapting backward error recovery to parallel real time systems is discussed in this paper. Because of error propagation among different cooperating processes, an error occurring in one process may influence some important outputs in other processes. Therefore, a local output has to be delayed until its validity is confirmed globally. Since backward error recovery adopts redundancy of computing time instead of processing equipment, the variation of the actual execution time of a cooperating process may be very large if it works in an unreliable environment. These problems are the primary obstacles to be removed. Previous studies focus their attentions on how to eliminate domino-effect dynamically. But backward error recovery cannot be applied directly in parallel real time systems even under the condition that no domino-effect exists. How to reduce output delays efficiently if no domino-effect remains? How to estimate this delay time? How to calculate the actual execution time of every process and how to schedule these processes under an unstable condition? These problems were omitted in literature unfortunately. The interest of this paper is to provide satisfactory solutions to these problems to make it possible to adopt backward error recovery efficiently in parallel real time systems.

关键词： very time Adapting Backward Error Recovery to Parallel Real Time Systems real

2 Tbit/s based coherent wavelength division multiplexing passive optical network for 5G transport

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Optoelectronics Letters 2021年第5期17卷 308-312页

作者： Abed Barzaq Isaac Ashour Waseem Shbair Fady IEl-Nahal Islamic University of Gaza GazaPalestine Al-Quds Open University GazaPalestine KN Circet Dublin D22 YP38Ireland

Future high-speed mobile communication systems require low latency and high capacity *** wavelength division multiplexing(WDM)passive optical network(PON)scheme is expected to play a vital role in these *** this paper,coherent WDM-PON scheme based on dual-polarization 16-quadrature amplitude modulation(DP-16 QAM)transceiver has been *** aim of this scheme is to build a 2 Tbit/s(125 Gbit/s/λ×16 wavelengths)network that will be used in the construction of the transport architecture of fifth generation(5 G)and beyond 5 G(B5 G)cellular networks either in mobile front haul(MFH)or mobile back haul(MBH).The results indicate that the proposed scheme is very adequate for both 5 G and B5 G cellular networks requirements.

关键词： WDM QAM Tbit/s based coherent wavelength division multiplexing passive optical network for 5G transport PON

Numerical Methods for Solving Space Fractional Partial Differential Equations Using Hadamard Finite-Part Integral Approach

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Communications on Applied Mathematics and Computation 2019年第4期1卷 505-523页

作者： Yanyong Wang Yubin Yan Ye Hu Department of Mathematics Luliang University38 Binghe North East RoadLuliangShanxi 033000China Department of Mathematics University of ChesterCHI 4BJ ChesterUK

We introduce a novel numerical method for solving two-sided space fractional partial differential equations in two-dimensional *** approximation of the space fractional Riemann-Liouville derivative is based on the approximation of the Hadamard finite-part integral which has the convergence order O(h^3-a),where h is the space step size and α∈(1,2)is the order of Riemann-Liouville fractional *** on this scheme,we introduce a shifted finite difference method for solving space fractional partial differential *** obtained the error estimates with the convergence orders O(τ+h^3-a+h^β),where τ is the time step size and β>0 is a parameter which measures the smoothness of the fractional derivatives of the solution of the *** the numerical methods for solving space fractional partial differential equations constructed using the standard shifted Griinwald-Letnikov formula or higher order Lubich's methods which require the solution of the equation to satisfy the homogeneous Dirichlet boundary condition to get the firstorder convergence,the numerical method for solving the space fractional partial differential equation constructed using the Hadamard finite-part integral approach does not require the solution of the equation to satisfy the Dirichlet homogeneous boundary *** results show that the experimentally determined convergence order obtained using the Hadamard finite-part integral approach for solving the space fractional partial differential equation with non-homogeneous Dirichlet boundary conditions is indeed higher than the convergence order obtained using the numerical methods constructed with the standard shifted Griinwald-Letnikov formula or Lubich's higher order approximation schemes.

关键词： Riemann-Liouville fractional derivative Space fractional partial differential equation Error estimates

A Distributed Error Recovery Technique and Its Implementation and Application on UNIX

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Journal of Computer Science & Technology 1990年第2期5卷 127-138页

作者：周笛徐向文 a Doctoral student of Tsinghua University BeijingChina. Techniche Universitüt München Lehrstuhl für Prozessrecher Franz-Josephstr.38/Ⅲ8000 München 40West Germany

This paper presents a checkpoint setting technique to eliminate domino effect in backward recovery in distributed systems,which is very efficient,powerful,widely applicable and easy to be *** theoretical analysis,an implementation on UNIX system and a package for software fault-tolerance are in- *** the problems of checkpoint management and process termination are discussed.

关键词： Pro very A Distributed Error Recovery Technique and Its Implementation and Application on UNIX

Crashworthiness Optimization of Steel-Magnesium Hybrid Double-Hat-Shaped Tubes

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Automotive Innovation 2018年第3期1卷 247-254页

作者： Guojun Zheng Zhiyuan Fan Hui Zhang Ping Zhou School of Automotive Engineering Dalian University of TechnologyDalian 116024China German Aerospace Centre(DLR)-Institute of Vehicle Concepts Pfaffenwaldring 38-4070569 StuttgartGermany

The double-hat-shaped magnesium tube was difficult to use in actual applications due to its frangible material *** alloy and traditional steel were integrated into a new hybrid thin-walled double-hat-shaped tube to improve vehicle *** classes of hybrid tubes were examined,namely Hybrid-I(steel top hat and magnesium alloy bottom hat)and Hybrid-II(magnesium alloy top hat and steel bottom hat).The energy absorption characteristics and crashworthiness optimization of the thin-walled hybrid structures were investigated under three-point bending conditions through experiments and ***-objective optimization design for the two hybrid tubes was implemented to elucidate their lightweight *** showed that the specific energy absorption of Hybrid-I tube and Hybrid-II tube was approximately 44.7%and 12.7%higher than that of the double-hat-shaped DC04 tube,*** Hybrid-I tube had better crashworthiness and lightweight properties compared with Hybrid-II ***-I tube also had better lightweight properties than single-material steel tube and reduced wall thickness compared with magnesium alloy tube.

关键词： Lightweight design Magnesium alloy Hybrid double-hat-shaped tube Crashworthiness Steel

An elasto-visco-plastic constitutive model of polypropylene incorporating craze damage behavior and its validation

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Journal of Central South University 2017年第6期24卷 1263-1268页

作者： GUI Zhong-xiang HU Xiao WANG Zi-jian The 38th Research Institute of China Electronics Technology Group Corporation Hefei 230088China State Key Laboratory of Materials Processing and Die&Mould Technology Huazhong University of Science and TechnologyWuhan 430074China

An elasto-visco-plastic constitutive model incorporating the craze damage behavior was developed for the polypropylene(PP), by using the plastic failure model applied for the concrete, to capture the craze yielding and stress-whitening phenomena. In addition, the developed constitutive model was implemented into finite element codes in Abaqus to simulate the tensile deformation. The standard uniaxial tensile tests were carried out. The stress-strain curves from the uniaxial tensile tests show that the stress keeps decreasing after yielding and the yield stress rises with the increasing of the strain rate. It is worth noting that the craze damage is more visible with higher strain rate. The stress-whitening can be seen clearly around the fracture. The uniaxial tensile tests using specially designed specimen with circular holes weakening were performed for the validation of the developed model. The simulation results of the tensile deformation of the hole-weakened specimen suggest that the stress-whitening could be attributed to the equivalent visco-plastic strain. By comparing between the simulation analysis and the experimental results, the proposed model can describe the stress whitening phenomenon with good accuracy.

关键词： elasto-visco-plastic constitutive model craze yielding stress-whitening finite element implementation

Effects of inositol hexaphosphate on proliferation of HT-29 human colon carcinoma cell line

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World Journal of Gastroenterology 2006年第26期12卷 4137-4142页

作者： Ying Tian Yang Song Qingdao University Medical College 38 Dengzhou Road Qingdao 266021 Shandong Province China

AIM： To investigate the effects of inositol hexaphosphate （IP6） on proliferation of HT-29 human colon carcinoma cell line. METHODS： Cells were exposed to various concentrations （0, 1.8, 3.3, 5.0, 8.0, 13.0 mmol/L） of IP6 for a certain period of time. Its effect on growth of HT-29 cells was measured by MTT assay. The expressions of cell cycle regulators treated with IP6 for 2 d were detected by imrnunocytochemistry. RESULTS： IP6 inhibited the HT-29 cell growth in a dose- and time-dependent manner. Analysis of cell cycle regulator expression revealed that IP6 reduced the abnormal expression of P53 and PCNA and induced the expression of P21. CONCLUSION： IP6 has potent inhibitory effect on proliferation of HT-29 cells by modulating the expression of special cell cycle regulators.

关键词： Phytic Acid Colonic neoplasms Cell proliferation

Forms of potassium and chlorine from oxy-fuel co-combustion of lignite coal and corn stover

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Carbon Resources Conversion 2019年第2期2卷 103-110页

作者： Chansa Oris Zhongyang Luo Wennan Zhang Chunjiang Yu State Key Laboratory of Clean Energy Utilization Zhejiang University38 Zheda RoadHangzhouZhejiang 310027China Department of Chemical Engineering Mid Sweden University85170 SundsvallSweden

In this work,the forms of potassium and chlorine from oxy-fuel co-combustion of lignite coal and corn stover under atmospheric pressure were *** order to check transitional stage,the feedstocks were combusted stepwise,first by pyrolysis to form coke under N2 environment and later by coke combustion into the ash at 850℃ in O_(2)/CO_(2) *** results show that an increase in blend ratio from 15%to 40%results in an increase in water-soluble potassium in the feedstock and the ashes from 0.15%to 0.4%and 0.015%to 0.038%in weight *** water-soluble potassium is present mainly as KCl and *** ammonium acetate soluble potassium,a similar trend to water-soluble potassium is presented but with a much lower content of *** bound potassium in the fuel matrix exists,likely in the form of AlKSi_(2)O_(6).Chlorides are present mainly in the form of KCl which is the dominant water-soluble compound.

关键词： Co-combustion(biomas&coal) Oxyfuel combustion Chemical fractionation Phase-mineral identifications