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Crosslinking Kinetics of Polyethylene with Small Amount of Peroxide and Its Influence on the Subsequent Crystallization Behaviors

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Chinese Journal of Polymer Science 2016年第9期34卷 1117-1128页

作者：牛艳华 Wen-bin Liang Yin-ling Zhang Xue-lian Chen Shih-yaw lai Guang-xian Li Du-jin wang College of Polymer Science and Engineering State Key Laboratory of Polymer Materials Engineering of ChinaSichuan UniversityChengdu 610065China Performance Material Center National Institute of Clean-and-low-carbon Energy(NICE)Beijing 102209China CAS Key Laboratory of Engineering Plastics Beijing National Laboratory for Molecular SciencesInstitute of ChemistryChinese Academy of SciencesBeijing 100190China

Crosslinking reactions of high density polyethylene with low peroxide concentrations ranging from 0.1 wt% to 1.0 wt% at temperatures of 170, 180 and 190 ℃ were monitored by rheological measurements. A critical gel forms at the peroxide concentration of 0.2 wt%, where the transition from long chain branching generation to crosslinking network formation could occur. Rheokinetics of crosslinking can be fitted well by Ding-Leonov＇s model. The curing rate k2 at the earlier stage exhibits about 3 times acceleration per 10 ~C with increasing temperature, while the equilibrium modulus G＇ at the fully cured stage is almost independent of temperature. Influences of crosslinking on the subsequent crystallization behaviors were detected by DSC measurements. Above the critical gel concentration, crystallization is largely retarded as evidenced by the lower crystallization temperature Tc and crystallinity Xc due to the network formation. The secondary crystallization valley located at the temperature near 80 ℃ can be observed above the critical concentration, which becomes more evident with the increasing peroxide concentration and curing temperature. This phenomenon provides another evidence of crystallization retardation by the crosslinking network.

关键词： Polyethylene Rheology Crosslinking kinetics Crystallization.

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Multicriteria optimization problems of finite horizon stochastic cooperative linear-quadratic difference games

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Science China(Information Sciences) 2022年第7期65卷 197-209页

作者： Chenchen peng Weihai ZHANG College of Electrical Engineering and Automation Shandong University of Science and Technology

This paper investigates the Pareto optimality of the regular and the indefinite stochastic cooperative linear-quadratic difference games in a finite time horizon. We derive a general form and a linear property of the solution to the linear stochastic difference system by defining several sequences of bounded and linear operators. The performance criteria's convexity can be guaranteed naturally under the weighted matrices' constraints for the regular cooperative game, and the weighting technique can well characterize the Pareto optimality. We also establish a novel convexity criterion for the cost functionals of the indefinite cooperative game, in which we find that the minimization of the performance criteria's weighted sum is equivalent to the Pareto optimal strategies. To derive all the Pareto optimal strategies and solutions, we present a computing algorithm using the weighted difference Riccati equation and the weighted difference Lyapunov equation for the regular and the indefinite cases. We present a practical example in the economy to validate the results.

关键词： multicriteria optimization problems Pareto optimality cooperative difference games discrete-time stochastic LQ theory the difference Riccati equation the difference Lyapunov equation

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Impedance-based Stability Criterion for the Stable Evaluation of Grid-connected Inverter Systems with Distributed Parameter Lines

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CSEE Journal of Power and Energy Systems 2023年第1期9卷 145-157页

作者： Xianghua peng Honggeng Yang College of Electrical Engineering Sichuan UniversityChengdu610065SichuanChina

For a multi-inverter grid-connected system,the stability of the point of common coupling(PCC)voltage is evaluated considering the distribution parameters of the transmission ***,the systems on both sides of the PCC are equalized,a smallsignal equivalent circuit similar to the“current source-grid”is established,and a mathematical model for the voltage of the PCC is ***,using Euler’s formula and Nyquist stability criterion,the PCC voltage stability of the grid-connected system is evaluated by the impedance analysis method under the premise that the single-side excitation is *** addition,the gridconnected conditions causing PCC voltage instability are studied.A phase compensation method based on an impedance phase compensation control strategy is *** stability of the grid-connected system is improved by compensating the phase margin at the equivalent impedance crossover-section frequency on both sides of the grid-connected system ***,a simulation circuit is built to simulate and analyze the proposed model and phase compensation *** simulation results verify the accuracy and effectiveness of the theoretical analysis.

关键词： Distributed parameter line impedance-based approach impedance phase compensation multi-inverter grid connection PCC voltage model small-signal equivalent circuit

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Numerical simulation of fluid flow and free surface fluctuations during wheel and belt casting process

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Journal of Iron and Steel Research International 2024年第5期31卷 1117-1126页

作者： Kun Gao Yan peng National Engineering Research Center for Equipment and Technology of Cold Strip Rolling Yanshan UniversityQinhuangdao066004HebeiChina

The unstable fluid flow and severe free surface fluctuations in the wheel and belt caster can affect the quality of the cast *** lower level height tends to entrap inclusions in the molten *** the other hand,the higher level height makes the production process more dangerous due to the overflow of high temperature fluid from the mold.A computational model of the molten metal pouring process was *** transient fluid flow and free surface fluctuations behavior were calculated using the three-dimensional large eddy simulation model and the volume of fluid *** results show that the flow velocity of the main jet gradually decreases under the influence of the low kinetic energy fluid in the *** is an obvious oscillation in the tail of the jet,while the flow field is asymmetric in *** jet is closer to the inside radius side due to the Coanda effect,and there is a recirculation zone on the inside radius and the outside radius respectively,according to the 10 s time-averaged *** with the industrial observation and simulation results,the shape of the free surface is a wave that varies with *** addition,the free surface height is lowest and the flow velocity is highest in the region near the jet.

关键词： Fluid flow Free surface Wheel and belt caster Large eddy simulation Volume of fluid method

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Kinematics and Mechanical Properties Analyses on Vibration Converter of Intelligent Damper forDrill Strings

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Advances in Applied Mathematics and Mechanics 2013年第5期5卷 671-687页

作者： Xiaohua Zhu Chunlin lai College of Mechatronic Engineering Southwest Petroleum UniversityChengdu 610500SichuanChina

Taking vibration converter of intelligent damper for drill strings as the study object,this paper analyzes the influential factors of motion state of the ball and conducts an explicit dynamics simulation by establishing a mechanics model of vibration *** study basis is Newton’s laws of motion,d’alembert’s principle and hertz contact *** we use world coordinate system,rotating coordinate system and Frenet coordinate system to deduce kinematics equations of vibration *** ultimate result demonstrates that the axial velocity and maximum contact stress change with the increment of ball diameter and helix *** also proves the validity of our derived kinematics and mechanical models and provides a good consultant value for the design and theoretical arithmetic of vibration converter for intelligent damper of drill strings.

关键词： Intelligent damper vibration converter kinematics analysis contact stress

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Electrochemical transformation of biomass-derived oxygenates

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Science China Chemistry 2023年第4期66卷 1011-1031页

作者： peng Zhou Jie Zhang School of Chemistry Monash UniversityClaytonVictoria 3800Australia

Replacing conventional fossil resources with renewable raw materials for chemical production and energy generation is crucial for achieving the carbon-neutral goal and alleviating the emerging energy *** has been considered as one of the most promising candidates for this purpose owing to its great natural abundance and inherent ability to fix CO_(2) in the form of multicarbon ***,biomass conversion through an electrochemical route is intriguing because of its operability near ambient conditions,flexible scalability(suitable for distributed manufacturing and even domestic use)and green generation of oxidative or reductive equivalents instead of wasteful and possibly explosive or flammable ***,recent progress in electrochemical transformation of biomass,including hydrogenation and amination,is reviewed with the emphasis on catalysts and strategies for enhancing catalytic *** advances in mechanistic understanding using in-situ spectroscopy are also briefly ***,recommendations for the directions for future development are also provided.

关键词： biomass utilization electrochemical hydrogenation reductive amination catalyst in-situ spectroscopy mechanism

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Larger in-plane upper critical field and superconducting diode effect observed in topological superconductor candidate InNbS_(2)nanoribbons

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Nano Research 2024年第7期17卷 6686-6694页

作者： Bo Zheng Changlong wang Xukun Feng Xiaozhen Sun Shasha wang Dawei Qiu Xiang Ma Ruimin Li Guanglei Cheng Lan wang Yalin Lu peng Li Shengyuan A.Yang Bin Xiang Department of Materials Science and Engineering CAS Key Lab of Materials for Energy ConversionAnhui Laboratory of Advanced Photon Science and TechnologyUniversity of Science and Technology of ChinaHefei 230026China Research Laboratory for Quantum Materials Singapore University of Technology and DesignSingapore 487372Singapore School of Microelectronics University of Science and Technology of ChinaHefei 230052China CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences University of Science and Technology of ChinaHefei 230026China Lab of Low Dimensional Magnetism and Spintronic Devices School of PhysicsHefei University of TechnologyHefei 230009China Research Laboratory for Quantum Materials IAPMEUniversity of MacaoMacaoChina

Recently,the coexistence of topology and superconductivity has garnered considerable ***,the dimensionality of these materials is crucial for the realization of topological quantum ***,the naturally grown materials,especially with one-dimensional feature that exhibits the coexistence of topology and superconductivity,still face challenges in terms of experimental realization and scalability,which hinders the fundamental research development and the potential to revolutionize quantum ***,we report the first experimental synthesis of quasi-one-dimensional InNbS_(2)nanoribbons that exhibit the coexistence of topological order and superconductivity via a chemical vapor transport ***,the inplane upper critical field of InNbS_(2)nanoribbons exceeds the Pauli paramagnetic limit by more than 2.2 times,which can be attributed to the enhanced spin-orbit coupling and the weakened interlayer interaction between the NbS_(2)layers induced by the insertion of In atoms,making InNbS_(2)exhibit spin-momentum locking similar to that of monolayer NbS_(2).Moreover,for the first time,we report the superconducting diode effect in a quasi-one-dimensional superconductor system without any inherent geometric *** measured maximum efficiency is manifested as 14%,observed atμ0H≈±60 mT,and we propose that the superconducting diode effect can potentially be attributed to the presence of the nontrivial topological *** work provides a platform for studying exotic phenomena in condensed matter physics and potential applications in quantum computing and quantum information processing.

关键词： topological order superconductivity nanoribbon superconducting anisotropy superconducting diode

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Bioorthogonal chemistry based on-demand drug delivery system in cancer therapy

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Frontiers of Chemical Science and Engineering 2023年第4期17卷 483-489页

作者： Lan Lin lai Jiang En Ren Gang Liu State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics&Center for Molecular Imaging and Translational Medicine School of Public HealthXiamen UniversityXiamen 361102China

Benefiting from the advantage of taking place in biological environments without interfering with an innate biochemical process,the bioorthogonal reaction that commonly contains the“bond formation”and“bond cleavage”system has been widely used in targeted therapy for a variety of ***,several prominent cases based on the bioorthogonal reaction that tailoring the metabolic glycoengineering tactics to modified cells for cancer immunotherapy,and the innovative tactics for reducing the metal ions’toxic and side effects with microneedle patches will be *** on these applications,the complexities,potential pitfalls,and opportunities of bioorthogonal chemistry in future cancer therapy will be evaluated.

关键词： bioorthogonal reaction cancer therapy metabolic glycoengineering bioorthogonal catalytic patch

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Grafting polymeric sulfur onto carbon nanotubes as highly-active cathode for lithium–sulfur batteries

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Journal of Energy Chemistry 2020年第3期29卷 27-33页

作者： Junfeng Wu Siyu Ding Shihai Ye Chao lai Institute of New Energy Material Chemistry School of Materials Science and EngineeringNational Institute for Advanced MaterialsNankai UniversityTianjin 300350China School of Chemistry and Materials Science Jiangsu Normal UniversityXuzhou 221116JiangsuChina

Lithium–sulfur(Li–S)batteries are being explored as promising advanced energy storage systems due to their ultra-high energy ***,fast capacity fading and low coulombic efficiency,resulting from the dissolution of polysulfides,remain a serious *** to weak physical adsorptions or barriers,chemical confinement based on strong chemical interaction is a more effective approach to address the shuttle ***,we devise a novel polymeric sulfur/carbon nanotube composite for Li–S battery,for which 2,5-dithiobiurea is chosen as the stabilizer of long-chain *** offers chemical bonds which bridge the polymeric sulfur and carbon *** obtained composite can deliver an ultra-high reversible capacity of 1076.2 m Ahg^-1(based on the entire composite)at the rate of 0.1 C with an exceptional initial Coulombic efficiency of 96.2%,as well as remarkable cycle *** performance is mainly attributed to the reaction reversibility of the obtained polymeric sulfur-based composite during the discharge/charge *** was confirmed by density functional theory calculations for the first time.

关键词： Lithium–sulfur batteries Polymeric sulfur Carbon nanotubes DFT calculations High capacity

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Ultrafast dynamics of photoexcited carriers and coherent phonons in ultrathin Bi;Te;thermoelectric films

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Science China(Physics,Mechanics & Astronomy) 2022年第1期65卷 71-77页

作者： Zemin Xu Jiandong Yao Guowei Yang Tianshu lai State Key Laboratory of Optoelectronic Materials and Technologies School of PhysicsSun Yat-sen UniversityGuangzhou 510275China State Key Laboratory of Optoelectronic Materials and Technologies Nanotechnology Research CenterSchool of Materials Science&EngineeringSun Yat-sen UniversityGuangzhou 510275China

The ultrafast dynamics of photoexcited carriers and coherent phonons in ultrathin Bi;Te;thermoelectric films are studied through transient differential transmission *** ultralow frequency coherent optical phonon at 0.16 THz emerges,especially in ultrathin films,and it is ascribed to interlayer breathing *** can divide the ultrathin films into two groups which have outof-phase vibration along the normal of a film plane,causing a destructive interference between in-plane propagating thermal waves in the two groups of quintuple layers,and thus possibly reducing the thermal conductivity of the ultrathin *** excitation power dependence of ultrafast dynamics reveals carrier-carrier scattering dominating thermalization,which provides a microscopic understanding of the reported high electrical conductivity and anomalously high power factor of ultrathin Bi;Te;films at room temperature.

关键词： electron-electron interactions coherent phonons carrier dynamics thermoelectric effects

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