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Determination and Temperature Dependence of Plateau Modulus for Polymerization of Propylene to Isotactic Polypropylene with Ultra-high Molecular Weight under Catalysis of Ziegler-Natta Catalyst

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Chemical Research in Chinese Universities 2005年第2期21卷 227-231页

作者： DINGjian DINGXue-jia XURi-wei YUDing-sheng MaterialsCollege BeijingUniversityofChemicalTechnologyBeijing100029P.R.China

The viscoelastic behavior of isotactic polypropylene with ultra-high molecular weight(UHPPH) and broad molecular weight distribution(MWD), produced in the presence of Ziegler-Natta catalyst, was investigated by means of oscillatory rheometry at 180 and 200 ℃, whose loss modulus(G″) plots at 180 and 200 ℃ versus the natural logarithm of angular frequency(ω) present a pronounced maximum at 34.35 and 69.21 rad/s, respectively, and do not show a maximum peak at 0.01-100 rad/s for Ziegler-Natta catalyzing ethylene-propylene random copolymerization(PPR) with a conventional molecular weight and broad MWD. The fact indicates that the high molecular weight is responsible for a maximum peak of G″(ω) vs. lnω curves for UHPPH. This makes it possible to determine the plateau modulus(G 0_N) of UHPPH from a certain experimental temperature G″(ω) curve directly. For UHPPH, the G 0_N determined to be 4.28×10 5 and 3.62×10 5 Pa at 180 and 200 ℃, respectively, decreases with the increase of temperature and is independent of the molecular weight, which directly confirms reputation theoretical prediction that the G 0_N has no relation to the molecular weight.

关键词： Isotactic polypropylene Ultra-high molecular weight Broad molecular weight distribution Plateau modulus

Dynamic modelling and robust current control of wind-turbine driven DFIG during external AC voltage dip

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2006年第10期7卷 1757-1764页

作者： HU jia-bing HE Yi-kang Department of Electrical Engineering Zhejiang University Hangzhou 310027 China

Doubly-Fed Induction Generator （DFIG）, with vector control applied, is widely used in Variable-Speed Constant- Frequency （VSCF） wind energy generation system and shows good performance in maximum wind energy capture. But in two traditional vector control schemes, the equivalent stator magnetizing current is considered invariant in order to simplify the rotor current inner-loop controller. The two schemes can perform very well when the grid is in normal condition. However, when grid disturbance such as grid voltage dip or swell fault occurs, the control performance worsens, the rotor over current occurs and the Fault Ride-Through （FRT） capability of the DFIG wind energy generation system gets seriously deteriorated. An accurate DFIG model was used to deeply investigate the deficiency of the traditional vector control. The improved control schemes of two typical traditional vector control schemes used in DFIG were proposed, and simulation study of the proposed and traditional control schemes, with robust rotor current control using Internal Model Control （IMC） method, was carded out. The validity of the proposed modified schemes to control the rotor current and to improve the FRT capability of the DFIG wind energy generation system was proved by the comparison study.

关键词： Wind energy generation Variable-Speed Constant-Frequency (VSCF) Doubly-Fed Induction Generator (DFIG) Fault Ride-Through (FRT) Internal Model Control (IMC)

Pressure evolution in shock-compacted granular media

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Petroleum Science 2023年第6期20卷 3736-3751页

作者： jia-Rui Li Jun-sheng Zeng Kun Xue State Key Laboratory of Explosive Science and Technology Beijing Institute of TechnologyBeijing100081China Institute of Applied Physics and Computational Mathematics Beijing100094China

The pressure evolution associated with the transient shock-induced infiltration of gas flow through granular media consisting of mobile particles is numerically investigated using a coupled Eulerian–Lagrangian *** coupling between shock compaction and interstitial flow has been revealed.A distinctive two-stage diffusing pressure field with deflection occurring at the tail of the compaction front is found,with corresponding spikes in both gaseous velocity and temperature profiles emerging within the width of the compaction *** compaction front,together with the deflection pressure,reaches a steady state during the later *** analytical prediction of the steady deflection pressure that considers the contributions of porosity and the non-isothermal effect is *** isothermal single-phase method we developed,combining the porosity jump condition across the compaction front,shows consistent pressure evolution with the non-isothermal CMP-PIC one under weak shock strength and low column ***,the microscale mechanism governing the formation of not only pressure deflection but also gaseous velocity and temperature spikes within the width of the compaction front has been *** aforementioned evolutions of the flow field are shown to arise from the nozzling effects associated with the particle-scale variations in the volume fraction.

关键词： Shock compaction Pressure evolution Transport in porous media Transient gas infiltration Mobile granular column

Analysis of energy pile groups subjected to non-uniform thermal loadings

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Underground Space 2023年第2期9卷 91-104页

作者： kang Fei Shi-jia Ding Hong-Yu Qin Department of Civil Engineering Yangzhou UniversityYangzhouJiangsu 225127China College of Science and Engineering Flinders UniversityAdelaide SA5042Australia

Sequentially coupled thermal-stress finite element analyses were performed to investigate the mechanical behaviors of an energy pile group subjected to non-uniform thermal *** group effect was highlighted by comparing the thermo-mechanical responses with those of the single pile *** to the thermal interactions between piles,the group piles’temperatures were higher than that of the isolated single *** only part of the piles served as heat exchangers,i.e.,the pile group was thermal loaded unevenly,there were dif-ferential deformations between the heated and the non-heated *** to the pile-raft-pile interaction,the axial forces of the piles chan-ged *** location of the heated pile had an important influence on the thermally induced axial force,while the effect of the soil’s coefficient of thermal expansion was not *** by the numerical result,a simplified method was proposed to capture the main characteristics of energy pile groups and to facilitate the *** proposed method was developed in the framework of the traditional load transfer approach,and the pile-raft-pile interaction was *** applying different temperature increments to dif-ferent piles,the non-uniform thermal loading was *** proposed method was verified by comparing with the finite element anal-ysis results and the data collected from the literature.

关键词： Energy pile group Non-uniform thermal loading Group effect Thermo-mechanical response

Dynamic modeling and direct power control of wind turbine driven DFIG under unbalanced network voltage conditions

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第12期9卷 1731-1740页

作者： jia-bing HU Yi-kang HE Lie XU School of Electrical Engineering Zhejiang University Hangzhou 310027 China Department of Electronics and Electrical Engineering University of Strathclyde Glasgow G40PG UK

This paper proposes an analysis and a direct power control (DPC) design of a wind turbine driven doubly-fed induction generator (DFIG) under unbalanced network voltage conditions. A DFIG model described in the positive and negative synchronous reference frames is presented. Variations of the stator output active and reactive powers are fully deduced in the presence of negative sequence supply voltage and rotor flux. An enhanced DPC scheme is proposed to eliminate stator active power oscillation during network unbalance. The proposed control scheme removes rotor current regulators and the decomposition processing of positive and negative sequence rotor currents. Simulation results using PSCAD/EMTDC are presented on a 2-MW DFIG wind power generation system to validate the feasibility of the proposed control scheme under balanced and unbalanced network conditions.

关键词： Doubly-fed induction generator (DFIG) Wind turbine Direct power control (DPC) Stator voltage oriented (SVO) Unbalanced network

Enhanced control of DFIG-used back-to-back PWM VSC under unbalanced grid voltage conditions

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第8期8卷 1330-1339页

作者： HU jia-bing HE Yi-kang NIAN Heng School of Electrical Engineering Zhejiang University Hangzhou 310027 China

This paper presents a unified positive-and negative-sequence dual-dq dynamic model of wind-turbine driven doubly-fed induction generator(DFIG) under unbalanced grid voltage conditions. Strategies for enhanced control and operation of a DFIG-used back-to-back(BTB) PWM voltage source converter(VSC) are proposed. The modified control design for the grid-side converter in the stationary αβ frames diminishes the amplitude of DC-link voltage ripples of twice the grid frequency,and the two proposed control targets for the rotor-side converter are alternatively achieved,which,as a result,improve the fault-ride through(FRT) capability of the DFIG based wind power generation systems during unbalanced network supply. A complete unbalanced control scheme with both grid-and rotor-side converters included is designed. Finally,simulation was carried out on a 1.5 MW wind-turbine driven DFIG system and the validity of the developed unified model and the feasibility of the proposed control strategies are all confirmed by the simulated results.

关键词： Unbalanced grid voltage Doubly-fed induction generator (DFIG) Back-to-back (BTB) Fault-ride through (FRT) Voltage source converter (VSC)

Revision of the photometric parameters of BS Cassiopeiae

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Research in Astronomy and Astrophysics 2010年第6期10卷 569-576页

作者： jia-jia He sheng-Bang Qian Miloslav Zejda Zdenek Mikulasek National Astronomical Observatories / Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Graduate University of the Chinese Academy of Sciences Beijing 100049 China Key Laboratory for the Structure and Evolution of Celestial Objects National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Institute of Theoretical Physics and Astrophysics Masaryk University Kotlarska 2 611 37 Brno Czech Republic Observatory and Planetarium of J. Palisa VSB- Technical University Ostrava Czech Republic

Seven charge-coupled device （CCD） photometric times of light minimum of the overcontact binary BS Cas which were obtained from 2007 August to November and one CCD light curve in the R band which was observed on 2007 September 24 and October 15, are presented. It is found that the light curve ofBS Cas has characteristics like a typical EW-type light variation. The light curve obtained by us is symmetric and shows total eclipses, which is very useful for determining photometric parameters with high precision. Photometric solutions were derived by using the 2003 version of the Wilson-Devinney code. It shows that BS Cas is a W-subtype overcontact binary （f = 27.5% ± 0.4%） with a mass ratio of q = 2.7188± 0.0040. The temperature difference between the two components is 190 K. Analysis of the 042 curve suggests that the period of AE Phe shows a long-term continuous decrease at a rate of dP/dt = - 2.45 × 10^-7 d yr^- 1 The long-time period decrease can be explained by mass transfer from the primary to the secondary.

关键词： stars binaries close -- stars binaries eclipsing -- stars individual BS Cas

Numerical analysis of added mass and damping of elastic hydrofoils

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Journal of Hydrodynamics 2020年第5期32卷 1009-1023页

作者： jia-sheng Li Ye-gao Qu Hong-xing Hua School of Naval Architecture and Ocean Engineering Huazhong University of Science and TechnologyWuhan 430074China Hubei Provincial Engineering Research Center of Data Techniques and Supporting Software for Ships(DTSSS) Wuhan 430074China State Key Laboratory of Mechanical System and Vibration Shanghai Jiao Tong UniversityShanghai 200240China

A numerical model is proposed for analyzing the effects of added mass and damping on the dynamic behaviors of *** coupled fluid-structure interactions(FSIs)of hydrofoils are analyzed by using the 3-D panel method for the fluid and the finite element method for the *** added mass and damping matrices due to the external fluid of the hydrofoil are asymmetric and computational *** computational inefficiencies associated with these asymmetric matrices are overcome by using a modal reduction technique,in which the first several wet mode vectors of the hydrofoil are employed in the analysis of the FSI *** discretized system of equations of motion for the hydrofoil are solved using the Wilson-6 *** present methods are validated by comparing the computed results with those obtained from the finite element *** is found that the stationary flow is sufficient for determining the wet modes of the hydrofoil under the condition of single-phase potential flow and without phase *** the case of relatively large inflow velocity,the added damping of the fluid can significantly affect the structural responses of the hydrofoil.

关键词： Fluid-structure interaction(FSI) hydroelastic response hydrofoil added mass added damping

Electrolytic alloy-type anodes for metal-ion batteries

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Rare Metals 2021年第2期40卷 329-352页

作者： Xian-Yang Li jia-kang Qu Hua-Yi Yin Key Laboratory for Ecological Metallurgy of Multimetallic Mineral of Ministry of Education School of MetallurgyNortheastern UniversityShenyang110819China Key Laboratory of Data Analytics and Optimization for Smart Industry Ministry of EducationNortheastern UniversityShenyang110819China

Alloy-type metals/alloys hold the promise of increasing the energy density of metal-ion batteries(MIBs)because of their theoretical high gravimetrical *** and semimetal-analogs are typical alloy-type ***,the large-scale extraction of semimetals(Si,Ge)and semimetal-analogs(Sb,Bi,Sn)by traditional metallurgical routes highly relies on using reducing agents(e.g.,carbon,hydrogen,reactive metals),which consumes a large number of fossil fuels and produces greenhouse gas *** addition,the common metallurgical methods for extracting semimetals involve relatively high operating temperatures and therefore produce bulk metal ingots solidified from the liquid ***,the commonly used electrode materials in batteries are fine ***,directly producing semimetal powders would be more energy *** addition,semimetals are good candidates to host alkali/alkaline-earth ions through the alloying process because the electronegativity of semimetals is ***,preparing semimetal powders via an environment-sound manner is of great interest to provide sustainable anode materials for MIBs while reducing the ecological ***-cost and high-output capacity anode powder materials,as well as straightforward and environmental-benign synthetic methods,play key roles in enabling the energy conversion and storage technologies for real applications of *** technologies offer new strategies to extract semimetals using electrons as the reducing agent that comes from renewable ***,the morphologies and structures of the electrolytic products can be rationally tailored by tuning the electrode potentials,electrolytes,and operating *** this regard,using the one-step green electrochemical method to prepare high-capacity and cheaper alloy-type metalloids for MIB anodes can fulfill the requirements for developing *** review critically overviews recent developments and advances in the elect

关键词： Electrochemical extraction Alloy-type anodes Metal-ion batteries Manufacture strategies Morphologies and structures