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Chinese Physics B 2020年第8期29卷 108-114页

作者： Y Y Wu x L zhu H Y yang z G Wang Y H Li B T Wang School of Nuclear Science and Technology Lanzhou UniversityLanzhou 730000China Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China Spallation Neutron Source Science Center Dongguan 523808China School of Materials Science and Engineering Hunan University of Science and TechnologyXiangtan 411201China Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China

Sulfide nanocrystals and their composites have shown great potential in the thermoelectric(TE)field due to their extremely low thermal *** a solid and hollow metastable Au2S nanocrystalline has been successfully ***,we study the TE properties of this bulk Au2S by first-principles calculations and semiclassical Boltzmann transport theory,which provides the basis for its further experimental *** results indicate that the highly twofold degeneracy of the bands appears at theΓpoint in the Brillouin zone,resulting in a high Seebeck ***,Au2S exhibits an ultra-low lattice thermal conductivity(~0.88 W·m^-1·K^-1 at 700 K).At 700 K,the thermoelectric figure of merit of the optimal p-type doping is close to 1.76,which is higher than 0.8 of zrSb at 700 K and 1.4 of PtTe at 750 *** work clearly demonstrates the advantages of Au2S as a TE material and would greatly inspire further experimental studies and verifications.

关键词： first principles calculation thermodynamic transport properties

Rational design of chemically complex metallic glasses by hybrid modeling guided machine learning

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npj Computational Materials 2021年第1期7卷 1242-1251页

作者： z.Q.zhou Q.F.He x.D.Liu Q.Wang J.H.Luan C.T.Liu Y.yang Department of Mechanical Engineering College of EngineeringCity University of Hong KongKowloonHong KongChina College of Mechatronics and Control Engineering Shenzhen UniversityShenzhenChina Laboratory for Structures Institute of Materials ScienceShanghai UniversityShanghaiChina Department of Materials Science and Engineering College of EngineeringCity University of Hong KongKowloonHong KongChina Department of Advanced Design and System Engineering College of EngineeringCity University of Hong KongChina

The compositional design of metallic glasses(MGs)is a long-standing issue in materials science and ***,traditional experimental approaches based on empirical rules are time consuming with a low *** this work,we successfully developed a hybrid machine learning(ML)model to address this fundamental issue based on a database containing~5000 different compositions of metallic glasses(either bulk or ribbon)reported since *** the prior works relying on empirical parameters for featurization of data,we designed modeling guided data descriptors in line with the recent theoretical models on amorphization in chemically complex alloys for the development of the hybrid classification-regression ML *** hybrid ML modeling was validated both numerically and *** importantly,it enabled the discovery of MGs(either bulk or ribbon)through the ML-aided deep search of a multitude of quaternary to scenery alloy *** computational framework herein established is expected to accelerate the design of MG compositions and expand their applications by probing the complex and multi-dimensional compositional space that has never been explored before.

关键词： alloy glasses metallic

MICROSTRUCTURES AND PROPERTIES OF RECIPROCATINGLY ExTRUDED Mg-6.4zn-1.1Y ALLOYS

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Acta Metallurgica Sinica(English Letters) 2008年第1期21卷 37-42页

作者： z.M. zhang C.J. xu x.F. Guo School of Materials Science ＆ Engineering Xi＇an University of Technology Xi＇an 710048 China

An icosahedral Mg3 Yzn6 quasicrystalline phase can be produced in Mg-zn- Y system alloys when a proper amount of zn and Y is contained, and it is feasible to prepare the quasicrystal phase-reinforced low-density magnesium alloy. In this article, phase constituents and the effect of reciprocating extrusion on microstructures and properties of the as-cast Mg-6.4zn-1.1 Y alloy are analyzed. The microstructure of the as-cast Mg-6.4zn-1.1 Y alloy consists of the α-Mg solid solution, icosahedral Mg3Yzn6 quasicrystal, and Mg3 Y2zn3 and Mgzn2 compounds. After the alloy was reciprocatingly extruded for four passes, grains were refined, Mg3 Y2 zn3 and Mgzn2 phases dissolved into the matrix, whereas, Mg3 Yzn6 precipitated and distributed uniformly. The alloy possesses the best performance at this state; the tensile strength, yield strength, and elongation are 323.4 MPa, 258.2 MPa, and 19.7%, respectively. In comparison with that of the as-cast alloy, the tensile strength, yield strength, and elongation of the reciprocatingly extruded alloy increase by 258.3%, 397.5%, and 18 times, respectively. It is concluded that reciprocating extrusion can substantially improve the properties of the as-cast Mg-6.4zn-1.1 Y alloy, particularly for elongation. The high performance of the Mg-6.4zn-1.1 Y alloy after reciprocating extrusion can be attributed to dispersion strengthening and grain-refined microstructures.

关键词： Reciprocating extrusion Mg-zn- Y alloy Icosahedral quasicrystal

Cyanobacterial bloom dynamics in Lake Taihu

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Journal of Environmental Sciences 2015年第6期27卷 249-251页

作者： Katherine z. Fu Birget Moe xing-Fang Li x. Chris Le Division of Analytical and Environmental Toxicology Department of Laboratory Medicine and Pathology University of Alberta

Lake Taihu is the third largest freshwater lake in China and serves as an important drinking water source for the local populace;however,decades of excessive nutrient loading fueled by anthropogenic activities have resulted in hypertrophic conditions,promoting the annual formation of nuisance phytoplankton blooms（Chen et al.,2003;Duan et al.,2009）

关键词： Cyanobacteria Blue-green algae Microcystin Natural toxins Water quality Nutrients Nitrogen and phosphorus Carbon dioxide

STUDY ON PROPERTIES OF PULSE ELECTRODEPOSITED RE-Ni-W-P-SiC COMPOSITE COATINGS

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Acta Metallurgica Sinica(English Letters) 2007年第2期20卷 111-116页

作者： z.C. Guo x.Y. zhu R.D. xu Faculty of Materials and Metallurgical Engineering Kunming University of Science and Technology Kunming 650093 China

The effects of pulse frequency f and duty cycle r on the deposition rate, composition, morphology, and hardness of pulse electrodeposited RE （rare earth）-Ni-W-P-SiC composite coatings have been studied. The results indicate that pulse current can improve the deposition rate of RE-Ni-W-P-SiC composite coatings; W, P, and SiC contents in the coating decrease with the increase of pulse frequency and reach the lowest value at f = 33Hz, whereas the RE content in the composite coatings increases with the increase of pulse frequency. SiC content decreases with the increase of duty cycle, W content reaches the lowest value, and P content reaches the highest value at r = 0.4; pulse current and RE can lead to smaller size of the crystalline grains; however, the effects of different pulse frequency and duty cycle on the morphologies of RE-Ni-W-P-SiC composite coatings are not obvious. The hardness of RE-Ni-W-P-SiC composite coatings is the highest when the duty cycle is at 0.6 and 0.8 and pulse frequency is at 50Hz. At the same pulse frequency, the hardness of RE-Ni-W-P-SiC composite coatings at r= 0.8 is higher than that at r= 0.6.

关键词： frequency duty cycle electrodeposition RE-Ni-W-P-SiC composite coating

MICROSTRUCTURE OF Mg-6.4zn-1.1Y ALLOY FABRICATED BY RAPID SOLIDIFICATION AND RECIPROCATING ExTRUSION

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Acta Metallurgica Sinica(English Letters) 2008年第1期21卷 30-36页

作者： z.M. zhang C.J. xu x.F. Guo School of Materials Science ＆ Engineering Xi＇an University of Technology Xi＇an 710048 China

In order to explore the methods to prepare high-strength quasicrystal-reinforced magnesium alloys, the flakes of rapidly solidified Mg-6.4zn-1.1 Y magnesium alloy with a thickness of 50-60μm were obtained by a melt spinning single-roller device, and the flakes were then processed into rods by reciprocating extrusion and direct extrusion. The microstructure of the alloy was analyzed by optical microscope and SEM, and the constituent phases were identified by xRD. Phase transformation and its onset temperature were determined by differential thermal analyzer （DTA）. The analysis result shows that rapid solidification for *** alloy can inhibit the eutectic reactions, broaden the solid solubility of zn in α-Mg solute solution, and impede the formation of Mg3 Y2zn3 and Mgzn2 compounds, and thus help the icosahedral Mg3 Yzn6 quasicrystal formed directly from the melt. The microstructure of the flakes consists of the α-Mg solid solution and icosahedral Mg3 Yzn6 quasicrystal. Dense rods can be made from the flakes by two-pass reciprocating extrusion and direct extrusion. The interfaces between flakes in the rods can be welded and jointed perfectly. During the reciprocating extrusion and direct extrusion process, more Mg3 Yzn6 compounds are precipitated and distributed uniformly, whereas the rods possess fine microstructures inherited from rapidly solidified flakes. The rods contain only two phases： α- magnesium solid solution as matrix and fine icosahedral Mg3 Yzn6 quasicrystal which disperses uniformly in the matrix.

关键词： Magnesium alloy Rapid solidification Reciprocating extrusion Quasicrystal

Behavior of High Performance PVA Fiber Reinforced Cement Composites in Triaxial Compression

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武汉理工大学学报 2010年第17期32卷 179-185页

作者： LI Y LIANG x W LIU z J xi'an University of Architecture and Technology Xi'an 710055China Henan Polytechnic University Jiaozuo 454003China

Based on an extensive experimental program,the paper studies the behavior of HPFRCC under triaxial compression. The experimental parameters are lateral confining pressure and PVA fiber content by volume. The test results indicate that ultimate strength and peak strain are significantly improved with the increases of confining pressure. The confining effect introduced by the fibers becomes minor in triaxial compression tests,where there is relatively high external confining pressure. The axial stress-strain curves with different confining pressure and different PVA fiber content by volume are obtained. Lateral confining pressure constraints the lateral expansion of HPFRCC,so there is a big plastic deformation with its ultimate strength improved. At lower confining pressure,PVA fiber content by volume has some effect on the decreased section of stress-strain curve. According to test results,the paper establishes formula of confining pressure with ultimate strength and axial peak strain respectively.

关键词： PVA high Performance fiber reinforced cement composites ultimate strength deformation property

STUDY ON MORPHOLOGY OF CHROMIUM IN CHILLED Cu-0.14%-2.0%Cr ALLOYS

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Acta Metallurgica Sinica(English Letters) 2004年第5期17卷 655-660页

作者： H.W.yang z.K.Fan SchoolofMaterialScienceandEngineering Xi＇anUniversityofTechnologyXi＇an710048China SchoolofMaterialScienceandEngineering Xi＇anUniversityofTechnologyXi＇an710048China

The morphology of chromium in chilled Cu-Cr alloys with 0.14%-2.0% Cr has been studied. The results showed that eutectic Cr phase takes a fibrous shape, and pre-eutectic Cr is dendritic in the studied chilled Cu-Cr alloy. During solute treatment of the eutectic and super-eutectic Cu-Cr alloys, only part of chromium particles dissolved in copper phase, some fiber and dendritic chromium still remained. Forging before solute treatment can reduce the size of primary Cr particles, which benefits the aging structure.

关键词： morphology of Cr Cu-Cr alloy chilling forging

The Joint Control of Variable Speed and On-Ramp Metering for Urban Expressway

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Journal of Systems Engineering and Electronics 2001年第3期12卷 25-30页

作者： Ma, J. Liu, x. Rong, J. Li, z. Transportation Research Center Beijing Polytechnic University Beijing 100022 China

The traffic performance of urban expressway is subject to non-recurring and recurring events, which may cause heavy congestion and vehicles long queuing on ramps. The low performance may bring more traffic delay to the whole network of urban road. This paper presents a new method, the joint control of variable speed control and on-ramp metering, which attempts to improve the level of traffic operations on urban expressway. By analyzing traffic flow on urban expressway, an optimum control strategy of variable speed and on-ramp metering is established in the paper.

关键词： Function evaluation Highway traffic control Intelligent control Mathematical models Motor transportation Parameter estimation Ramp generators Speed control

RESEARCH ON THE SELECTION OF FRICTION MODELS IN THE FINITE ELEMENT SIMULATION OF WARM ExTRUSION

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Acta Metallurgica Sinica(English Letters) 2003年第2期16卷 90-96页

作者： x.B.Lin H.S.xiao z.L.zhang National Die and Mold CAD Engineering Research Center Shanghai Jiao Tong University1954 Hua Shan RoadShanghai 200030ChinaNational Die and Mold CAD Engineering Research CenterShanghai Jiao Tong University1954 Hua Shan RoadShanghai 200030ChinaNational Die and Mold CAD Engineering Research CenterShanghai Jiao Tong University1954 Hua Shan RoadShanghai 200030China

During the process of finite element simulation of precision warm forging, the selection of friction models has a direct effect on the precision accuracy of finite element simulation results. Among all the factors which influence the selection of friction models, the distribution rule of normal stress at the tool-workpiece interface is a key one. To find out the distribution rule of normal stress at the tool-workpiece interface, this paper has made a systematic research on three typical plastic deformation processes: forward extrusion, backward extrusion, and lateral extrusion by a method of finite element simulation. Then on the base of synthesizing and correcting traditional friction models, a new general friction model which is fit for warm extrusion is developed at last.

关键词： friction model warm extrusion finite element simulation