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Collision efficiency of two nanoparticles with different diameters in Brownian coagulation

Applied Mathematics and Mechanics(English Edition) 2011年第8期32卷 1019-1028页

作者：王玉明林建忠 Institute of Fluid Measurement and Simulation China Jiliang University State Key Laboratory of Fluid Power Transmission and Control Zhejiang University

The collision efficiency of two nanoparticles with different diameters in the Brownian coagulation is investigated. The collision equations are solved to obtain the collision efficiency for the dioctyl phthalate nanoparticle with the diameter changing from 100 nm to 750 nm in the presence of the van der Waals force and the elastic deformation force. It is found that the collision efficiency decreases as a whole with the increase of both the particle diameter and the radius ratio of two particles. There exists an abrupt increase in the collision efficiency when the particle diameter is equal to 550 nm. Finally, a new expression is presented for the collision efficiency of two nanoparticles with different diameters.

关键词： nanoparticle Brownian coagulation collision efficiency different diameters van der Waals force elastic force

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Synergistic utilization of coal and other energy- key to low carbon economy

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能源前沿 2011年第1期5卷 1-19页

作者： Weidou NI Zhen CHEN State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Thermal EngineeringTsinghua UniversityBeijing 100084China

In China, coal is a dominant component of energy mix, and it is expected to remain as such over the next 30 to 40 years. Coal is expected to be used even more in power generation. The direct combustion of coal already has been causing severe pollution and ecological degradation, and it is quite difficult to address the need to reduce greenhouse gas (GHG) given the direct combustion of coal. Therefore, the polygeneration system based on coal gasification, which is one of the major examples of synergistic utilization of coal, is proposed. It is a comprehensive solution to meet the energy challenges China is facing. Furthermore, the synergy of fossil fuels (especially coal) with renewable energy, the synergy of different kinds of energy for energy storage, the synergy of centralized and distributed supply of different kinds of energy, and the synergy of different kinds of energy in smart energy grid (power, gas, heat, and water) are the keys to making China a low-carbon economy. Carbon dioxide (CO2) mitigation in China should begin from the coalchemical industry given their accumulated relevant experiences. The mitigation process should gradually be transformed into the 'IGCC + polygeneration + CCUS'.The objectives of this paper are to describe the synergistic utilization of coal, and to analyze the synergy of coal with other energy resources, and to propose the scientific and technological problems to achieve these synergies.

关键词： synergy clean and efficient utilization of coal coal-based polygenration CO2 mitigation energy storage

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Nanosecond Repetitively Pulsed Dielectric Barrier Discharge in Air at Atmospheric Pressure

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Plasma Science and Technology 2011年第5期13卷 591-595页

作者：邵涛章程牛铮于洋严萍周远翔 Institute of Electrical Engineering Chinese Academy of Sciences Key Laboratory of Power Electronics and Electric Drive Chinese Academy of Sciences State Key Laboratory of Control and Simulation of Power Systems and Generating Equipment Electrical Engineering DepartmentTsinghua University

Dielectric barrier discharge （DBD） between two cylindrical glass containers with salt water generated by a nanosecond repetitively pulsed power generator is reported. The electrical parameters, luminous images and spectrum diagnosis are presented. It is shown that the DBD possesses a large discharge current and an intense optical emission from the nitrogen second positive system below 400 nm. The gas temperature remains very close to room temperature regardless of pulse polarity. Luminous photographs with a short exposure time down to 2 ns indicate that no filament is observed and the discharge is homogeneous.

关键词： dielectric barrier discharge nanosecond pulse homogeneous discharge atmospheric pressure air emission spectrum

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Generation of Atmospheric Pressure Plasma by Repetitive Nanosecond Pulses in Air Using Water Electrodes

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Plasma Science and Technology 2011年第6期13卷 735-739页

作者：邵涛于洋章程姜慧严萍周远翔 Institute of Electrical Engineering Chinese Academy of Sciences Key Laboratory of Power Electronics and Electric Drive Chinese Academy of Sciences State Key Laboratory of Control and Simulation of Power Systems and Generating Equipment Electrical Engineering DepartmentTsinghua University

Dielectric barrier discharge （DBD） excitated by pulsed power is a promising method for producing nonthermal plasma at atmospheric pressure. Discharge characteristic in a DBD with salt water as electrodes by a home-made unipolar nanosecond-pulse power source is presented in this paper. The generator is capable of providing repetitive pulses with the voltage up to 30 kV and duration of 70 ns at a 300 Ω resistive load. Applied voltage and discharge current are measured under various experimental conditions. The DBD created between two liquid electrodes shows that the discharge is homogeneous and diffuse in the whole discharge regime, Spectra diagnosis is conducted by an optical emission spectroscopy. The air plasma has strong emission from nitrogen species below 400 nm, notably the nitrogen second positive system.

关键词： non-thermal plasma dielectric barrier discharge pulsed power nanosecondpulse pulse repetition frequency atmospheric pressure air emission spectra.

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A neutral-point potential balancing algorithm for five-level ANPC converters

A neutral-point potential balancing algorithm for five-level...

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2011 International Conference on Electrical Machines and systems, ICEMS 2011

作者： Wang, Kui Li, Yongdong Zheng, Zedong State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing 100084 China

ISBN: (纸本)9781457710445

Five-level active neutral-point-clamped (ANPC) converter is a newly emerging topology which can overcome the drawbacks of traditional neutral-point clamped (NPC) converters and flying-capacitor (FC) converters. Its dc-link is subdivided into two equal parts and the main problem is the neutral-point (NP) potential balancing. In this paper, a NP potential balancing algorithm based on zero-sequence voltage injection is presented. By calculating the NP currents of all key zero-sequence voltages, the most appropriate zero-sequence voltage is selected to generate the demanded NP current. Moreover, by further limiting the span of injected zero-sequence voltages, the NP balancing algorithm can make the two IGBTs connected in series operate at fundamental frequency. A three-phase five-level ANPC inverter prototype was built up and experimental results are presented to verify the validity of this algorithm. © 2011 IEEE.

关键词： power converters

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Detection for voltage fluctuation and flicker calculation based on the instantaneous reactive power theory

Detection for voltage fluctuation and flicker calculation ba...

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International Conference on power Electronics systems and Applications (ICPESA)

作者： Wang, Jidong Liu, Kun Gao, Yanjing Yang, Guanqing Che, Yanbo Key Laboratory of Power System Simulation and Control Tianjin University Ministry of Education Tianjin China

ISBN: (纸本)9781457702051

The voltage flicker which might bring out lighting equipments glitter and images distortion, make people's visual fatigue and adversely affect people's daily lives is caused by the great increase of shocking and nonlinear loads in the power system. In this paper, the causes, detection and measurement of the voltage fluctuation and flicker are analyzed, instantaneous reactive power theory detection method is used for simulation of voltage fluctuations and calculation of short-time flicker value and compared with square detection. The flicker values obtained by instantaneous reactive power theory detection are close to the real value, and the result of simulation shows the effectiveness of this method. © 2011 IEEE.

关键词： Reactive power

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Harmonic analysis method based on multiple modulation zoom analysis and interpolating windowed FFT method

Harmonic analysis method based on multiple modulation zoom a...

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International Conference on power Electronics systems and Applications (ICPESA)

作者： Wang, Jidong Yang, Guanqing Wen, Jing Zhu, Dong Che, Yanbo Key Laboratory of Power System Simulation and Control Ministry of Education Tianjin University Tianjin China

ISBN: (纸本)9781457702051

Since many power electronics equipments and nonlinear loads were accessed, more and more harmonics and inter-harmonics occurred in power system. But when the analyzed signal contains components with frequency close to each other, precise analysis can not be made by traditional harmonics analysis methods such as interpolating windowed FFT method. In this paper, first a new method-multiple modulation zoom analysis based on complex analytic bandpass filter is adopted to make an accurate analysis to this kind of components. Then the remaining components are also analyzed by traditional method. simulations compared to direct interpolating windowed FFT method show that the proposed method can make a much better analysis with higher frequency resolution and so effectiveness of this method is demonstrated. © 2011 IEEE.

关键词： Harmonic analysis

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A grid-connection control scheme of PV system with fluctuant reactive load

A grid-connection control scheme of PV system with fluctuant...

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International Conference on Electric Utility Deregulation and Restructuring and power Technologies

作者： Li, Bin Tian, Xiaohe Zeng, Hongyan Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University Tianjin China

ISBN: (纸本)9781457703638

The fluctuations of reactive load in micro-grid will have a great impact on the supply voltage. In this paper, a novel grid-connection control is proposed in view of this problem, based on a model of a PV system with load paralleled in large system. It can not only make full use of photovoltaic power, but also maintain a stable voltage with a fluctuant reactive load. It adopted double-loop principle in inverter control. The grid-connected current of the PV system and the current of large system are both decoupled into active and reactive component by abc/dq0 transformation to achieve the independent control of active and reactive power. On the one hand, the active component of the PV grid-connected current is adjusted to the reference value given by the Maximum power Point Tracking (MPPT) in order to maintain maximum active power output of PV, the reactive component of the large system current is adjusted in order to maintain a constant reactive power output. Thus a stable supply voltage can be maintained with a fluctuant reactive load, as the supply voltage of the grid-connected PV system is mainly sustained by the large system. On the other hand;the main circuit topology of three-phase reactive power compensation device and three-phase grid-connected inverter is exactly the same. Thus, in support of a reasonable control strategy it can be integrated together with both function of grid connection and reactive power compensation control. These can ensure a stable voltage in the PV system with a fluctuant reactive load paralleled in large system by the regulation of power. Its advantages compared with the simple and traditional unity-power-factor inverter control scheme are validated by simulation with Matlab/Simulink. © 2011 IEEE.

关键词： Reactive power

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A study on capacity of distributed generation and its effect on short circuit current at micro-grid operation mode

A study on capacity of distributed generation and its effect...

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International Conference on Electric Utility Deregulation and Restructuring and power Technologies

作者： Qiang, Jin Shuo, Zhang Yong-Li, Li Key Laboratory of Power System Simulation and Control Ministry of Education Tianjin University Tianjin China

ISBN: (纸本)9781457703638

Now more and more distributed generations will be connected to distributed power system. It's found that different distributed generation has its own operation characteristic such as fluctuation and uncertainty. When micro-grid is to be island the voltage and frequency will change, so different control modes have been used on different distributed generation. Different kinds of distributed generation have different behavior when system operates normally or fault occurs. Classification and equivalence were adopted to deal with all kinds of the distributed generations in system. The distributed generations with same control mode can be combined to an equivalent generation. When system operates on grid-connection mode the short circuit current relies on the capacity of grid so it is rather large for the capacity of distribution grid is much more than that of distributed generations. But when micro-grid operates on island mode the short circuit current may decrease to a relative small value. Over current protection is widely used in distribution system, and the performance of it is dependent on operation mode, so the value estimate of short circuit current is necessary for verification of credibility and selectivity. Two summations of capacity were proposed to estimate the minimum and maximum short-circuit current in island. © 2011 IEEE.

关键词： Distributed power generation

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Study on control Method of Dual-Motor for Steer-By-Wire system

Study on Control Method of Dual-Motor for Steer-By-Wire Syst...

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International Conference on Consumer Electronics, Communications and Networks

作者： Changfu Zong Haiou Xiang Lei He Fei Sha State Key Laboratory of Automotive Simulation and Control Jilin University School of Mechanical and Power Engineering Harbin University of Science and Technology

ISBN: (纸本)9781457714146

In this paper, a structure of the steer-by-wire system with dual steering motors based on FlexRay bus has been proposed for meeting the real-time and reliability requirement of a steer-by-wire system. A control method is proposed to realize the coordinated control of dual steering motors. The control method has been verified experimentally. The results indicate that the control method can effectively achieve coordinated control of the dual steering motors and improve the safety of steer-by-wire vehicles.

关键词： Vehicle Steer-by-wire control method of dual-motor FlexRay bus

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