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Surface activation of colloidal indium phosphide nanocrystals

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Nano Research 2017年第3期10卷 941-958页

作者： yang li Chaodan pu Xiaogang Peng Center for Chemistry of Novel & High-Performance Materials Department of Chemistry Zhejiang University Hangzhou 310027 China

Against general wisdom in crystallization, the nucleation of InP and III-V quantum dots （QDs） often dominates their growth. Systematic studies on InP QDs identified the key reason for this： the dense and tight alkanoate-ligand shell around each nanocrystal. Different strategies were explored to enable necessary ligand dynamics--i.e., ligands rapidly switching between being bonded to and detached from a nanocrystal upon thermal agitation--on nanocrystals to simultaneously retain colloidal stability and allow appreciable growth. Among all the surface-activation reagents tested, 2,4-diketones （such as acetylacetone） allowed the full growth of InP QDs with indium alkanoates and trimethylsilylphosphine as precursors. While small fatty acids （such as acetic acid） were partially active, common neutral ligands （such as fatty amines, organophosphines, and phosphine oxides） showed limited activation effects. The existing amine-based synthesis of InP QDs was activated by acetic acid formed in situ. Surface activation with common precursors enabled the growth of InP QDs with a distinguishable absorption peak between ~450 and 650 nm at mild temperatures （140-180 ~C）. Furthermore, surface activation was generally applicable for InAs and III-V based core/shell QDs.

关键词： quantum dots nanocrystals indium phosphide surface

A simplified approximate model of compressible hypervelocity penetration

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Acta Mechanica Sinica 2018年第5期34卷 910-924页

作者： Wenjie Song Xiaowei Chen pu Chen Department of Mechanics and Engineering Science College of EngineeringPeking UniversityBeijing 100871China Centre for Applied Physics and Technology(CAPT) Peking UniversityBeijing 100871China Advanced Research Institute for Multidisciplinary Science Beijing Institute of TechnologyBeijing 100081China State Key lab of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China

A simplified approximate model considering rod/target material's compressibility is proposed for hypervelocity *** study the effect of shockwaves on hypervelocity penetration whenever the compressibility of the rod is much larger,analogously,and much less than that of the target,*** results show that the effect of shockwaves is insignificant up to 12 km/s,so the shockwave is neglected in the present approximate *** Murnaghan equation of state is adopted to simulate the material behaviors in penetration and its validity is *** approximate model is finally reduced to an equation depending only on the penetration velocity and a simple approximate solution is *** solution of the approximate model is in agreement with the result of the complete compressible *** addition,the effect of shockwaves on hypervelocity penetration is shown to weaken material's compressibility and reduce the interface pressure of the rod/target,and thus the striking/protective performance of the rod/target is weakened,*** also conduct an error analysis of the interface pressure and penetration *** a velocity change of 1.6 times the initial sound speed for the rod or target,the error of the approximate model is very *** metallic rod-target combinations,the approximate model is applicable even at an impact velocity of 12 km/s.

关键词： Compressibility Approximate model Shockwave Hypervelocity penetration Equation of state (EOS)

TESTING lINEAR AND NONlINEAR GRANGER CAUSAlITy IN CSI300 FUTURES AND SPOT MARKETS BASED ON NEW CONCEPTS OF NONlINEAR POSITIVE/NEGATIVE SPIllOVER

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Journal of Systems Science & Complexity 2014年第4期27卷 729-742页

作者： ZHOU pu lU Fengbin WANG Shouyang Risk Management Unit Bank of China Head Office Academy of Mathematics and Systems Science Chinese Academy of Sciences

supported by the National Natural Science Foundation of China under Grant Nos.71125005 70871108 and 70810107020;; Outstanding Talents Funds of Organization Department Beijing Committee of CPC

关键词： China stock market negative volatility spillover nonlinear Granger causality test riskabsorption volatility spillover.

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红沙梁东井田含煤地层特征及沉积环境分析

煤炭技术 2025年第1期44卷 108-110页

作者：王普仲乃亮甘肃煤炭地质勘查院兰州730000

通过对红沙梁东井田下白垩统老树窝群含煤地层展布规律的研究,结合区域构造及沉积环境等方面进行综合分析,结果表明:含煤地层呈现为一个小型煤盆地形态,其含煤性呈中西部好,向四周逐渐变差的趋势;含煤地层沉积环境主要有扇三角洲、湖泊... 详细信息

通过对红沙梁东井田下白垩统老树窝群含煤地层展布规律的研究,结合区域构造及沉积环境等方面进行综合分析,结果表明:含煤地层呈现为一个小型煤盆地形态,其含煤性呈中西部好,向四周逐渐变差的趋势;含煤地层沉积环境主要有扇三角洲、湖泊、湖泊三角洲,其间的三角洲平原泥炭沼泽与滨湖沼泽环境为全区的有利成煤环境,形成了区内的4层可采煤层。

关键词：含煤地层下白垩统沉积环境红沙梁东井田

Effect of Milling Tools on the Microstructure and Property of Cu-Based Composites Prepared by Mechanical Alloying

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Acta Metallurgica Sinica(English letters) 2017年第12期30卷 1155-1162页

作者： Ruo-Shan lei Ming-pu Wang College of Materials Science and Engineering China Jiliang University School of Materials Science and Engineering Central South University

Cu and Nb powders were used as starting materials to produce Cu-Nb and Cu-NbC-WC composites by mechanical alloying. X-ray diffraction, scanning electron microscopy, transmission electron microscopy observations and microhardness measurements have been used to study the effects of milling tools on the phase, microstructure and property of the composites. The results revealed that a single-phase nanocrystalline solid solution was obtained using stainless steel vials and balls （Alloy 1）. Nevertheless, Cu-7 wt% Nb powders milled by tungsten carbon vials and balls exhibited an amorphous phase （Alloy 2）. The as-milled powders were then vacuum hot-pressing sintered. The microstructure of sintered Alloy 1 consisted of Nb nanoparticles and Cu nanograins. Instead, Alloy 2 showed a microstructure with NbC nanoparticles and WC submicron-sized particles dispersed throughout the Cu matrix. Furthermore, Alloy 2 （～ 322 HV） had a higher microhardness than Alloy 1 （～ 302 HV）.

关键词： Mechanical alloying Cu-based composite Mechanical property Nanostructured materials

COUPlING SIMUlATION OF SURFACE FlOW AND SUBSURFACE FlOW OVER POROUS MEDIA

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Journal of Hydrodynamics 2004年第3期16卷 283-289页

作者： ZHANGPei-wen lIUDe-fu SONGyu-pu DepartmentofCivilEngineering DalianUniversityofTechnologyDalian116023China DepartmentofCivilEngineering ChinaThreeGorgesUniversityYichang443002China DepartmentofCivilEngineering DalianUniversityofTechnologyDalian116023China

Mathematical model of water flow over porous media is developed, the computerprogram is compiled , and an example is given to verify the validity of the model. The results ofthe calculation show that the model is very... 详细信息

关键词： seepage runoff porous media

Impedance Analysis of Forging Process and Strategy Study on Compliance for Forging Manipulator

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Chinese Journal of Mechanical Engineering 2013年第4期26卷 651-658页

作者： ZHANG pu yAO Zhenqiang DU Zhengchun State Key lab of Mechanical System and Vibration Shanghai Jiao Tong University

In the field of heavy forging, there are numerous researches on deformation rule in forging process by FEM simulation, however, not many scholars take the equipment constraint and the mutual reaction load between the forging manipulator clamp and the forging blank into account, which will impact on safety of manipulator body and quality of forging blank. This paper presents an impedance model to describe the load and formulates compliance strategies correspondingly to reduce the mutual reaction load for forging manipulator. Firstly, an FEM model of forging process is built. Meanwhile, the clamp of forging manipulator is added to the model as movement constraint and interaction part between the manipulator and the forming process. Secondly, a typical forging process is simulated by changing the movement constraint, and then an impedance model is established to describe the relationship between the load and movement constraint. Finally, two kinds of compliance strategies are formulated according to the impedance model, one is called free compliance, and the other is initiative/passive compliance. The simulation results show that compliance strategies reduce the load amounting to 5 000 kN in z direction between the manipulator clamp and the forging blank obviously, which may lead to serious accidents, such as the capsizing of forging manipulator, the fracture of manipulator clamp, and so on. The proposed research simulates the more real forging process, gets the initiative/passive compliance strategy which is more simple and suitable to the real producing and better for forming a forging process planning and control system in the modern production, and improves the quality and efficiency of heavy forging.

关键词： forging impedance compliance manipulator

Characteristics of two transferable aminoglycoside resistance plasmids in Escherichia coli isolated from pig and chicken manure

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Frontiers of Environmental Science & Engineering 2019年第3期13卷 99-113页

作者： Chengjun pu Xiaoyan Gong ying Sun Beijing Key laboratory of Farmland Soil Pollution Prevention and Remediation College of Resources and Environmental Sciences China Agricultural University Beijing 100193 China

Plasmid-mediated antibiotic resistance genes (ARGs) have recently become a more prominent concern in the global environment. However, the prevalence of aminoglycoside resistance plasmids in the livestock industry is under reported. In this study, two transferable aminoglycoside resistance plasmids, pRKZ3 and pKANJ7, isolated from pig and chicken manure, were characterized. Results showed that pRKZ3 (8236 bp) is a non-conjugative IncQ plasmid and contains genes encoding for plasmid replication and stabilization (repA, repB and repC), mobilization (mob), and antibiotic resistance (arr-3 and aacA). pKANJ7 (30142 bp) is a conjugative IncX plasmid which codes for a type IV secretion system (T4SS). Conjugative transfer experiments showed that the optimal mating time of pKANJ7 was 8 h under the starvation condition, but the number of tranconjugants increased with time under the nutrient condition. Statistical analysis indicated that the two plasmids had little impact on the growth of their hosts, but a relatively high level of fitness cost due to pKANJ7 was observed. We also found that the fitness cost of plasmids depended on their hosts. Compared with pKANJ7, the relative fitness cost index of pRKZ3 varied within a narrow range during the 10 days of competition. The low level of fitness cost of pRKZ3 might contribute to the persistence of the plasmid in the environment. Our study provides new information for understanding the characterizations of antibiotic resistance plasmids (ARPs) in manure sources and helps to clarify the transfer and persistence of ARPs in the environment following the application of manure.

关键词： Escherichia coli Characteristics Aminoglycoside resistance plasmids Transfer Persistence

STATIC STUDy OF CANTIlEVER BEAM STICTION UNDER ElECTROSTATIC FORCE INFlUENCE

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Acta Mechanica Solida Sinica 2004年第2期17卷 104-112页

作者： Zhangyin Zhaoya-pu DepartmentofMechanicalEngineering UniversityofConnecticutStorrsCT06268-3139USA StateKeylaboratoryofNonlinearMechanics InstituteofMechanicsChineseAcademyofScienceBeijing100080.China

The model and analysis of the cantilever beam adhesion problem under the action of electrostatic force are given. Owing to the nonlinearity of electrostatic force, the analytical solution for this kind of problem is not available. In this paper, a systematic method of generating polynomials which are the exact beam solutions of the loads with di?erent distributions is provided. The polynomials are used to approximate the beam displacement due to electrostatic force. The equilibrium equation o?ers an answer to how the beam deforms but no information about the unstuck length. The derivative of the functional with respect to the unstuck length o?ers such information. But to compute the functional it is necessary to know the beam deformation. So the problem is iteratively solved until the results are converged. Galerkin and Newton-Raphson methods are used to solve this nonlinear problem. The e?ects of dielectric layer thickness and electrostatic voltage on the cantilever beam stiction are studied. The method provided in this paper exhibits good convergence. For the adhesion problem of cantilever beam without electrostatic voltage, the analytical solution is available and is also exactly matched by the computational results given by the method presented in this paper.

关键词： micro-cantilever beam adhesion/stiction electrostatic force Galerkin method constraint stationary peel number