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Analysis on ignition and extinction of n-heptane in homogeneous systems

Science china(Technological Sciences) 2005年第5期48卷 556-569页

作者： LIU Yongfeng1 & PEI Pucheng2.1. Mechanical and Electrical Engineering Department, beijing Institute of Civil Engineering and Architec-ture, beijing 100044,{2. 2. state key laboratory of automotive safety and energy, tsinghua university, beijing 100084,{2. 1. Mechanical and Electrical Engineering Department Beijing Institute of Civil Engineering and Architecture 100044 Beijing China 2. state key laboratory of automotive safety and energy Tsinghua University 100084 Beijing China

To calculate ignition delay times, the governing equations about species and temperature, which are in a closed volume based on the theory of thermal explosion and in a continuously stirred flow reactor, are deducted. The method referred to steady state assumptions is based on the observation that due to very fast chemical processes in combustion problems many chemical species and reactions are in a quasi-steady state or partial equilibrium. When a species is assumed to be in the steady state, the corresponding differential equation can be replaced by an algebraic relation, which reduces the computational costs. The steady state solution of the reactor equations describes the three ignition temperature regimes and get “S-shaped curve”. The reduced simplified 4-step mechanism for n-heptane from 1011 elementary reactions leads with the steady state assumptions to linear differential equations, which is solved. The simulation results of the 4-step reduced mechanism for n-heptane are fitted well with the experiment data. At last, two important parameters are discussed thoroughly and the temperature perturbation is given. It reduces the computational efforts considerably without losing too much accuracy and further supplies numerical methods for turbulent combustion in the diesel engine.

关键词： ignition delay times, thermal runaway, steady state assumptions, continuously stirred flow reactor.

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Optimization of gasoline hydrocarbon compositions for reducing exhaust emissions

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Journal of Environmental Sciences 2009年第9期21卷 1208-1213页

作者： SHEN Yitao,SHUAI Shijin,WANG Jianxin,XIAO Jianhua state key {2. of automotive safety and energy,tsinghua university,beijing 100084,china [a]state key {2. of automotive safety and energy Tsinghua University Beijing 100084 China

Effects of hydrocarbon compositions on raw exhaust emissions and combustion processes were studied on an engine test bench. The optimization of gasoline hydrocarbon composition was discussed. As olefins content increased from 10.0% to 2..0% in volume, the combustion duration was shortened by about 2.degree crank angle （°CA）, and the engine-out THC emission was reduced by about 15%. On the other hand, as aromatics content changed from 35.0% to 45.0%, the engine-out NOx emissions increased by 4%. An increment in olefins content resulted in a slight increase in engine-out CO emission, while the aromatics content had little effect on engine-out total hydrocarbon （THC） and CO emissions. Over the new European driving cycle （NEDC）, the THC, NOx and CO emissions of fuel with 2..0% olefins and 35.0% aromatics were about 45%, 2.% and 19% lower than those of fuel with 10.0% olefins and 40.0% aromatics, respectively. The optimized gasoline compositions for new engines and new vehicles have low aromatics and high olefins contents.

关键词： optimization hydrocarbon composition exhaust emissions olefins aromatics

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Research and development on transonic compressor of high pressure ratio turbocharger for vehicle internal combustion engines

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Science china(Technological Sciences) 2010年第7期53卷 1817-1823页

作者： ZHENG XinQian, ZHANG YangJun & YANG MingYang state key {2. of automotive safety and energy, tsinghua university, beijing 100084, china 1. state key {2. of automotive safety and energy Tsinghua University Beijing 100084 China

The pressure ratio required for a turbocharger centrifugal compressor increases with internal combustion engine power density. High pressure ratio causes a transonic flow field at the impeller inducer. Transonic flow narrows the stable flow range and de-teriorates stage efficiency. In this work, an advanced high pressure ratio transonic compressor was designed. The experimental results show that the maximum pressure ratio of this turbocharger is about 4.2. the maximum efficiency is above 80% and the stable flow range at the designed rotating speed is up to 34%. A turbocharger with this transonic compressor has been applied to some vehicle research actually, and improved power density by 40%.

关键词： turbocharger internal combustion (IC) engine compressor high pressure ratio transonic

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Lion pride optimizer:An optimization algorithm inspired by lion pride behavior

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Science china(Information Sciences) 2012年第10期55卷 2369-2389页

作者： WANG Bo,JIN XiaoPing & CHENG Bo state key {2. of automotive safety and energy,tsinghua university,beijing 100084,china 1. state key {2. of automotive safety and energy Tsinghua University Beijing 100084 China

In this paper,we report a novel optimization algorithm,lion pride optimizer(LPO),which is inspired by lion pride *** framework is mainly based on lion prides’ evolution process and group living *** a lion pride,brutal competition of individuals happens among male lions both within and among prides;on the other hand,each member plays an important role in the persistence of a lion *** on this framework,concepts from lion prides behavior,e.g.,the strongest males occupy nearly all mating resources,and if a new cohort of males is able to take over a pride,they will seek to kill young cubs sired by their predecessors,are employed metaphorically to design optimum searching strategies for solving continuous optimization *** the studies of the algorithm property,it is found that the LPO algorithm is not sensitive to most parameters,which shows the robustness of the algorithm and the parameters are not *** tendency of the algorithm is not *** is found that the pride update strategy and brutal competition of individuals are two main factors that contribute to the performance of *** to the test results on 2. famous benchmark functions,the LPO algorithm has better performance than the other seven state-of-the-art algorithms on both unimodal and multimodal benchmark functions;in the test of high-dimensional multimodal problems,LPO outperforms the other five algorithms on all benchmark functions.

关键词： animal behavior evolutionary algorithm lion pride optimization swarm intelligence

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Analysis micro-mechanism of burrs formation in the case of nanometric cutting process using numerical simulation method

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Science china(Technological Sciences) 2007年第2期50卷 129-137页

作者： HAN XueSong & HU YuanZhong state key {2. of Tribology, tsinghua university, beijing 100084, china 1. state key {2. of Tribology Tsinghua University Beijing 100084 China

Burrs (exit failure), being one of the important factors influencing the final precision of workpiece, have been widely studied. Today, with the development of manufacturing technology, the depth of cut falls into the range of nanometer or subnanometer, there may be some different disciplines dominating the burrs generation process. Molecular dynamics (MD) emthod, which is different from continuous mechanics, plays an important role in describing microscopic world. Take the example of single crystal copper, this paper carries out MD analysis micro-mechanism of burrs generation process. The results show that the burrs geometry depends on the type of workpiece (ductile or brittle). The depth of cut is decreased in the case of positive burrs generation process while the depth of cut is increased in case of negative burrs generation process. keywords burr - molecular dynamics - micro-mechanism Supported by china Postdoctor Science Foundation (Grant No. 2.060390458)

关键词： burr molecular dynamics micro-mechanism

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ADAPTIVE VARIABLE STRUCTURE CONTROLLERS AND APPLICATION TO ENGINE IDLE SPEED CONTROL SIMULATION

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Chinese Journal of Mechanical Engineering 2003年第2期16卷 171-174页

作者： Hui Qing Quyang Minggaostate key {2. of automotivesafety and energy,tsinghua university,beijing 100084, china state key {2. of automotive safety and energy Tsinghua University Beijing 100084 China

A neural-network-based adaptive variable structure control methodology isproposed for the tracking problem of nonlinear discrete-time input-output systems. The unknowndynamics of the system are approximated via radial basis function neural networks. The control lawis based on sliding modes and simple to implement. The discrete-time adaptive law for tuning theweight of neural networks is presented using the adaptive filtering algorithm with residueupper-bound compensation. The application of the proposed controller to engine idle speed controldesign is discussed. The results indicate the validation and effectiveness of this approach.

关键词： variable structure control adaptive control neural networks nonlineardiscrete-time systems idle speed control

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Degradation of 4-chlorophenol in aqueous solution by γ-radiation and ozone oxidation

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Science china Chemistry 2006年第2期49卷 186-192页

作者： HU Jun1, WANG Jianlong1,2.& CHEN Rong1 1. laboratory of Environmental Technology, Institute of Nuclear energy Technology,{2., beijing 100084, china 2. state key Joint laboratory of Environmental Simulation and Pollution Control,{2., beijing 100084, china Correspondence should be addressed to Wang Jianlong 1. laboratory of Environmental Technology Institute of Nuclear Energy Technology Tsinghua University Beijing 100084 China 2. state key Joint {2. of Environmental Simulation and Pollution Control Tsinghua University Beijing 100084 China

The degradation of 4-chlorophenol (4-CP) by using gamma rays generated by a 60Co source in the presence of O3 was investigated. The radiolysis of 4-CP and the kinetics of 4-CP min-eralization were analyzed based on the determination of total organic carbon (TOC). The influence of initial 4-CP concentration and the free radicals scavengers (such as NaHCO3 and t-butanol) on the 4-CP degradation was also studied. The results showed that when the radiation rate was 336 Gy·min?1, 4-chlorophenol at concentration of 10 mg·L?1 could be completely degraded at the radiation dose of 2.kGy. The degradation of 4-chlorophenol could be described by a first-order reaction model, the rate constant of 4-CP degradation by combined ozonation and radiation was 0.1016 min?1, which was 2.4 times higher than the sum of radiation (0.02.4 min?1) and ozonation (0.0137 min?1). It re-vealed that the combination of radiation and ozonation resulted in synergistic effect, which can re-markably increase the degradation efficiency of 4-CP.

关键词： radiolysis, 4-chlorophenol, priority pollutant, degradation, O3, synergistic effect, kinetics.

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state of the art:Mechanical behavior of soil-structure interface

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Progress in Natural Science:Materials International 2009年第10期19卷 1187-1196页

作者： Ga Zhang,Jianmin Zhang state key {2. of Hydroscience and Engineering,tsinghua university,beijing 100084,china [a]state key {2. of Hydroscience and Engineering Tsinghua University Beijing 100084 China

The monotonic and cyclic behavior of a soil-structure interface has a significant effect on the mechanical response of a soil-structure interaction ***,the behavior of the interface should be investigated with focusing on the individual characters different from other geomaterials.A brief introduction and critical review are presented on the state of the art of monotonic and cyclic behavior of soil- structure interface,including the test device and measurement techniques,fundamental rules and deformation mechanism,constitutive models and their applications in the numerical *** tendencies of the investigation on the interface are also predicted in this paper.

关键词： Interface Soil Mechanical behavior Test Constitutive model Numerical analysis

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Measuring-basis-encrypted six-state quantum key distribution scheme

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Progress in Natural Science:Materials International 2006年第1期16卷 84-89页

作者： CHEN Pan1, DENG Fuguo1, WANG Pingxiao1 and LONG Guilu1,2.(key laboratory for Quantum Information and Measurements and Department of Physics,{2., beijing 100084, china 2. key laboratory for Atomic and Molecular NanoSciences,{2., beijing 100084, china) [a]Department of Physics Tsinghua University Key Laboratory for Quantum Information and Measurements Beijing China [b]tsinghua university Key Laboratory for Atomic and Molecular NanoSciences Beijing China

A six-state quantum key distribution scheme with measuring-basis encryption technique, which is based on the six-state protocol and the MBE protocol, is proposed. In this modified six-state quantum key distribution protocol, Alice and Bob use a control key to synchronize the use of their measuring-basis so that they always use the same measuring-basis. This modified six-state quantum key distribution protocol retains the advantage of higher security and at the same time has a higher efficiency.

关键词： quantum key distribution measuring-basis encrypted six-state security.

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Atomistic simulations of the effect of a void on nanoindentation response of nickel

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Science china(Physics,Mechanics & Astronomy) 2010年第9期53卷 1716-1719页

作者： ZHU PengZhe,HU YuanZhong & WANG Hui state key {2. of Tribology,tsinghua university,beijing 100084,china 1. state key {2. of Tribology Tsinghua University Beijing 100084 China

Three-dimensional molecular dynamics simulations have been performed to investigate the effect of a void on the nanoindentation of nickel thin *** radius and depth of the void are varied to explore how they influence the *** simulation results reveal that the presence of a void softens the material and allows for a larger indentation depth at a given load compared to the no void *** radius and depth of the void have a major effect on the indentation behaviors of the thin *** is also observed that the void will collapse during the nanoindentation of crystal with *** when the indentation depth is sufficiently large,the void will *** is found that the indentation depth needed to make the void disappear depends on the void size and location.

关键词： nanoindentation molecular dynamics simulations void

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