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| 1 | PHYSICAL MODELING FOR THE MECHANISMS OF BEAD FORMATION DEFECTS BASED ON THE STABILITY OF LIQUID METAL显示文摘Based on the theory of stability of the liquid metal under the action of surface tension,a physical mod- el is established for the mechanisms of the bead formation deferct’ humping’, which is generated during high - speed welding.A boundary function is introduced to correct the model,theoretical results got by the model correspond well with the experimental phenomena. A two - dimensional conducting model is adoopted in the simulation of the temperature field during high - speed welding.Finally, the factors acting upon the stability of liquid metal are analyzed. | S. Y. Yin L. Feng J. Z. Ding and S. J. Chan( 1) Beijing Polytechnic University, Beijing 100022, China 2) National Key Laboratory of Advanced Wdlding Production Technology, HIT, Harbin 150001, China) | 2000 | Acta Metallurgica Sinica(English Letters)2000，13，1： | 28 |
| 2 | State-of-the-art review on frequency response of wind power plants in power systems显示文摘With an increasing penetration of wind power in the modern electrical grid, the increasing replacement of large conventional synchronous generators by wind power plants will potentially result in deteriorated frequency regulation performance due to the reduced system inertia and primary frequency response. A series of challenging issues arise from the aspects of power system planning,operation, control and protection. Therefore, it is valuable to develop variable speed wind turbines(VSWTs) equipped with frequency regulation capabilities that allow them to effectively participate in addressing severe frequency contingencies. This paper provides a comprehensive surveyon frequency regulation methods for VSWTs. It fully describes the concepts, principles and control strategies of prevailing frequency controls of VSWTs, including future development trends. It concludes with a performance comparison of frequency regulation by the four main types of wind power plants. | Ziping WU Wenzhong GAO Tianqi GAO Weihang YAN Huaguang ZHANG Shijie YAN Xiao WANG | 2018 | Journal of Modern Power Systems and Clean Energy2018，6，1： | 26 |
| 3 | 全功率变流器可变速抽水蓄能机组的功率调节特性分析显示文摘全功率变流器(full size converter,FSC)可变速抽水蓄能技术是控制电网负荷频率,平衡可再生能源发电波动的有效手段。在介绍三电平FSC可变速抽水蓄能机组整体结构的基础上,给出了机侧变流器和网侧变流器的模型和控制策略。在确定由于电网需求而产生的参考功率的基础上,提出了FSC可变速抽水蓄能机组在发电模式和电动模式时有功功率和无功功率的控制策略。针对所建立的FSC可变速抽水蓄能机组模型,采用冲击响应傅立叶变换法,给出了机组的频谱特性,对照风电波动频谱特性,阐述了全功率机组对可再生能源引起的电网波动控制的有效性。最后对抽水蓄能机组在抑制风电出力波动中的作用进行了仿真验证。 | 畅欣 韩民晓 郑超 | 2016 | 电力建设2016，37，4： | 21 |
| 4 | Measures against the adverse impact of natural wind on air-cooled condensers in power plant显示文摘The natural wind plays disadvantageous roles in the operation of air-cooled steam condensers in power plant.It is of use to take various measures against the adverse effect of wind for the performance improvement of air-cooled condensers.Based on representative 2×600 MW direct air-cooled power plant,three ways that can arrange and optimize the flow field of cooling air thus enhance the heat transfer of air-cooled condensers were proposed.The physical and mathematical models of air-cooled condensers with various flow leading measures were presented and the flow and temperature fields of cooling air were obtained by CFD simulation.The back pressures of turbine were calculated for different measures on the basis of the heat transfer model of air-cooled condensers.The results show that the performance of air-cooled condensers is improved thus the back pressure of turbine is lowered to some extent by taking measures against the adverse impact of natural wind. | YANG LiJun,DU XiaoZe & YANG YongPing Key Laboratory of Condition Monitoring and Control for Power Plant Equipment of Ministry of Education of China,North China Electric Power University,Beijing 102206,China | 2010 | Science China(Technological Sciences)2010，53，5： | 21 |
| 5 | Influence of obstacle disturbance in a duct on explosion characteristics of coal gas显示文摘In combination with experimental research,numerical simulation is performed to investigate the influence law of the obstacles in a duct on the explosion flame of premixed coal gas and air. The numerical method uses upwind WENO scheme and two-step chemical reaction model. The interaction mechanism is addressed between the compression wave from reflection on the right end of the duct and flame propagation. The reflected wave is found to result in the decrease of flame velocity. On this basis,we analyze the mechanism of the obstacles on flame as well as the law of flow field variation thus caused. The results suggest that,due to the obstacles,deflagration wave is repeatedly reflected,combustible gas mixture is fully compressed,temperature and pressure rise,chemical reaction speed increases,and hence flame intensity is strengthened. At the same time,a tripe point forms as a result of wall reflection of the deflagration wave from the obstacles and furthermore local flame speed increases. As the triple point propagates forward,the flame speed gradually decreases due to dissipation of energy. These conclusions provide a valuable theoretical foundation for the prediction of explosion field,prevention of fire and explosion and effective control of the com-bustion speed and flame propagation speed in detonation propulsion. | WANG Cheng1,MA TianBao1 & LU Jie2 1 State Key Laboratory of Explosion Science and Technology,Beijing Institute of Technology,Beijing 100081,China 2 Taiyuan Gas Company,Taiyuan 030024,China | 2010 | Science China(Physics,Mechanics & Astronomy)2010，53，2： | 16 |
| 6 | 高速铁路轨道静态精密检测若干技术问题探讨显示文摘轨道静态精密检测直接服务于轨道精调作业,是确保轨道高平顺性的关键施工环节之一。结合国内多条客运专线轨道静态精密检测的实践,探讨了轨道静态精密检测过程中的一系列精度控制措施,同时就绝对平顺性与相对平顺性概念进行了对比分析,并就相对平顺性提出了一种简化处理方法。 | 王国民 马文静 | 2010 | 铁道勘察2010，36，6： | 16 |
| 7 | Wheat breeding in northern China: Achievements and technical advances显示文摘Common wheat is the major cereal crop that underpins the food safety of China. Both winter wheat and spring wheat are grown on ~24 million ha. This review aims to summarize the current status of wheat production and breeding progress in the northern wheat production areas of the country, and to review recently advanced technologies being applied in wheat breeding, including the use of dwarf-male-sterile(DMS) wheat, speed breeding and specialized wheat breeding SNP chips. Crossing is the initial step in most breeding programs. DMS wheat is a convenient tool for large scale production of hybrid seed. Speed breeding or accelerated generation turnover attempts to reduce the time taken in cultivar development. Several different SNP chips are high-throughput, genome-wide genotyping platforms for breeding and research. | Hongjie Li Yang Zhou Wenli Xin Yiqin Wei Junling Zhang Lilei Guo | 2019 | The Crop Journal2019，7，6： | 16 |
| 8 | Effect of RANS Turbulence Model on Aerodynamic Behavior of Trains in Crosswind显示文摘The numerical simulation based on Reynolds time-averaged equation is one of the approved methods to evaluate the aerodynamic performance of trains in crosswind.However,there are several turbulence models,trains may present different aerodynamic performances in crosswind using different turbulence models.In order to select the most suitable turbulence model,the inter-city express 2(ICE2)model is chosen as a research object,6 different turbulence models are used to simulate the flow characteristics,surface pressure and aerodynamic forces of the train in crosswind,respectively.6 turbulence models are the standard k-ε,Renormalization Group(RNG)k-ε,Realizable k-ε,Shear Stress Transport(SST)k-ω,standard k-ωand Spalart-Allmaras(SPA),respectively.The numerical results and the wind tunnel experimental data are compared.The results show that the most accurate model for predicting the surface pressure of the train is SST k-ω,followed by Realizable k-ε.Compared with the experimental result,the error of the side force coefficient obtained by SST k-ωand Realizable k-εturbulence model is less than 1%.The most accurate prediction for the lift force coefficient is achieved by SST k-ω,followed by RNG k-ε.By comparing 6 different turbulence models,the SST k-ωmodel is most suitable for the numerical simulation of the aerodynamic behavior of trains in crosswind. | Tian Li Deng Qin Jiye Zhang | 2019 | Chinese Journal of Mechanical Engineering2019，32，5： | 13 |
| 9 | ON BASIC EQUATIONS OF WATER HAMMER显示文摘ONBASICEQUATIONSOFWATERHAMMER￥YangJian-dong,WuRong-qiao(WuhanUniversityofHydraulicandElectricEngineering,Wuhan430072,P.R.Chin... | Yang Jian-dong,Wu Rong-qiao(Wuhan University of Hydraulic and Electric Engineering,Wuhan 430072,P.R. China) | 1996 | Journal of Hydrodynamics1996，8，2： | 11 |
| 10 | 论高速铁路测量网布设技术显示文摘《高速铁路工程测量规范》已于2009年12月1日颁布实施,'三网合一'是构建高速铁路测量体系的基本原则。简要介绍了高速铁路精密工程测量'三网合一'的概念,对提出高速铁路测量'三网合一'必要性进行了论述,并就高速铁路测量如何实现'三网合一'进行了探讨。 | 苏全利 | 2010 | 铁道勘察2010，36，6： | 10 |
| 11 | Phase transformation refinement of coarse primary carbides in M2 high speed steel | Fu-sheng PAN Wei-qing WANG Ai-tao TANG Li-zhi WU Ting-ting LIU Ren-ju CHENG | 2011 | Progress in Natural Science:Materials International2011，21，2： | 10 |
| 12 | Effects of key factors of rotary triboelectrostatic separator on efficiency of fly ash decarbonization显示文摘On the basis of understanding the principle of rotary triboelectrostatic separation, dynamic analysis of charged fly ash particles aimed at determining the key factors and separation experiments to improve decarbonization efficiency had been carried out Variables of electrode plate voltage and corrected wind speed are the key factors which affect the decarbonization efficiency on the separation of fly ash, The results of separation experiments show that:(1) With the plate voltage increasing, the efficiency of decarbonization continuously rises and in its selected range, the optimal voltage level is 45 KV;(2) The corrected wind speed can impact the efficiency of decarbonization significantly: with the speed increasing, the efficiency of decarbonization shows a trend of first decline, then increase and decrease again, and in its selected range, the optimal speed is 2.0 m/s. This study is of significance for the improvement of rotary triboelectrostatic separation performance and its decarbonization separation efficiency. | Tao Youjun Zhang Ling Tao Dongping Xian Yushuai Sun Qixiao | 2017 | International Journal of Mining Science and Technology2017，27，6： | 10 |
| 13 | Short-term local prediction of wind speed and wind power based on singular spectrum analysis and locality-sensitive hashing显示文摘With the growing penetration of wind power in power systems, more accurate prediction of wind speed and wind power is required for real-time scheduling and operation. In this paper, a novel forecast model for shortterm prediction of wind speed and wind power is proposed,which is based on singular spectrum analysis(SSA) and locality-sensitive hashing(LSH). To deal with the impact of high volatility of the original time series, SSA is applied to decompose it into two components: the mean trend,which represents the mean tendency of the original time series, and the fluctuation component, which reveals the stochastic characteristics. Both components are reconstructed in a phase space to obtain mean trend segments and fluctuation component segments. After that, LSH is utilized to select similar segments of the mean trend segments, which are then employed in local forecasting, so that the accuracy and efficiency of prediction can be enhanced. Finally, support vector regression is adopted forprediction, where the training input is the synthesis of the similar mean trend segments and the corresponding fluctuation component segments. Simulation studies are conducted on wind speed and wind power time series from four databases, and the final results demonstrate that the proposed model is more accurate and stable in comparison with other models. | Ling LIU Tianyao JI Mengshi LI Ziming CHEN Qinghua WU | 2018 | Journal of Modern Power Systems and Clean Energy2018，6，2： | 10 |
| 14 | Model test on dynamic characteristics of invert and foundation soils of high-speed railway tunnel显示文摘A dynamic model test(CL = 4) at different velocities of train,namely different loading frequencies,is carried out to study the dynamic characteristics of a high-speed railway tunnel invert and its foundation soils.Not only are the accelerations,dynamic coefficients,dynamic stresses of the invert and foundation soils emphatically analyzed,their relationship with the velocity of the train are discussed in detail.Through laboratory testing,the attenuation of vibration propagating from up the rails is obtained and the calculation formula of the speed influence coefficient of the tunnel invert is preliminarily established.The depth of the foundation soils influenced by vibration is also determined in this study.It is shown that the responses of the tunnel invert and foundation soils to vibration are slightly increased with the velocity of the train;circumferential stresses in the bottom of the invert are tensile stresses and maximum stresses appear under the foot of the rails;the dynamic soil pressures of the foundation decrease quickly with the distance away from the tunnel invert and an exponential relationship exists between them. | Huang Juan Yuan Tieying Peng Limin Yu Jun Ding Zude | 2015 | Earthquake Engineering and Engineering Vibration2015，14，3： | 10 |
| 15 | Backstepping Control of Speed Sensorless Permanent Magnet Synchronous Motor Based on Slide Model Observer显示文摘This paper presents a backstepping control method for speed sensorless permanent magnet synchronous motor based on slide model observer. First, a comprehensive dynamical model of the permanent magnet synchronous motor(PMSM) in d-q frame and its space-state equation are established. The slide model control method is used to estimate the electromotive force of PMSM under static frame, while the position of rotor and its actual speed are estimated by using phase loop lock(PLL) method. Next,using Lyapunov stability theorem, the asymptotical stability condition of the slide model observer is presented. Furthermore, based on the backstepping control theory, the PMSM rotor speed and current tracking backstepping controllers are designed, because such controllers display excellent speed tracking and anti-disturbance performance. Finally, Matlab simulation results show that the slide model observer can not only estimate the rotor position and speed of the PMSM accurately, but also ensure the asymptotical stability of the system and effective adjustment of rotor speed and current. | Cai-Xue Chen Yun-Xiang Xie Yong-Hong Lan | 2015 | International Journal of Automation and computing2015，12，2： | 10 |
| 16 | GE light speed 16排螺旋CT常见故障的维修和体会显示文摘多排螺旋CT目前已广泛应用于临床,使用过程中会遇到各种各样故障,在熟练掌握多排螺旋CT的基本原理,工作结构,及相关计算机知识的基础上,可以对多排螺旋CT机很多常见故障进行快速及时修复,大大提高了设备使用率,保证临床工作的顺利进行。本文简要阐述了我院GE light speed 16排螺旋CT在使用过程中常见的故障现象、诊断分析、解决方法和体会。为相关专业技术人员提供一定的参考和借鉴。 | 苏根元 王萍萍 于小晶 | 2011 | 中国医学装备2011，8，9： | 9 |
| 17 | Experimental study of an insert and its influence on churning losses in a high-speed electro-hydrostatic actuator pump of an aircraft显示文摘The speed of an Electro-Hydrostatic Actuator(EHA) pump can recently reach 20000 r/min, and its churning losses increase obviously with an increasing speed, which results in low efficiency and thus increasing heat in aircraft EHA systems. In order to reduce churning losses at high speeds, more attention should be given to the design of an insert. In this paper, the effect of an insert with different design parameters on churning losses is investigated through Computational Fluid Dynamics(CFD) simulation and experiments by calculating the difference between churning losses torques of the test pump with and without the insert based on a high-speed churning losses test rig.Analytical results show that the gap between the insert and the cylinder is critical for churning losses reduction. It is found that the churning losses of the test pump can be reduced with a decreasing gap between the cylinder block and the insert at high speeds. This is because the insert can decrease the turbulence occurrence at high speeds. The results can be used for flow field analysis and optimization of the high-speed EHA pump and provide a new method for improving efficiency of high-speed EHA pumps. | Junhui ZHANG Ying LI Bing XU Min PAN Qun CHAO | 2019 | Chinese Journal of Aeronautics2019，32，8： | 9 |
| 18 | VALENCE ELECTRON STRUCTURE OF HIGH PROPERTY HIGH SPEED RESISTANCE STEEL AND ITS COMPOSITION DESIGN显示文摘Theempiricalelectrontheory of solidsand molecules( EET) and theimproved TFDtheory wereapplied tocalculatethe phasestructurefactorsand interfaceconjunction factorsofcom mon alloying elementsin high speed impact resistance ( HSIR) steel. According tothese va lenceelectron structure parametersitis deduced thatthe alloying elements of high propertyHSIRsteelshould be Mn, Cr, Ni and Mo. The microscopicstructure ofthesteel with this compositionisthe mixtureof martensite, bainiteand austeniteafter quenching andlow tem peraturetempering.Itspropertiesare:σb = 1750 MPa,σ0 2 = 1460 MPa,δ5 = 12 7 % , AKV(at 40 ℃, cross direction) = 21J, which exceed the requirement of design. For the thick plateof high property HSIRsteel,itissuggestedto add alittleamountof Cu on thebasisofabovecomposition . | Z.L. Li1,2) ,C.X.Ma2) and Z.L.Liu1) 1) Department of Materials Science and Engineering,Liaoning Institute of Technology,Jinzhou 121001 ,China 2) Collage of Science, Northeast University ,Shenyang,110006 , China | 1999 | Acta Metallurgica Sinica(English Letters)1999，12，4： | 8 |
| 19 | Numerical study on the restriction speed of train passing curved rail in cross wind显示文摘The results of numerical investigations of aerodynamic forces and moment coefficients of flow passing a simplified train geometry under different wind speeds are summarized. To compute numerically the different coefficients, the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations, combined with the k-ε turbulence model, were solved using finite volume technique. The pres-sure-velocity fields were coupled using the SIMPLE algorithm. At each iteration the pressure correction was obtained by solving a velocity divergence-derived Poisson-like equation. With the computed aerodynamic forces, the formula of the restriction speed at which the train passed curved rail in cross wind was deduced to analyse the influences of aerodynamic forces on the restriction speed. Results of numerical investigations showed that aerodynamic lift and overturn moment increased more and more rapidly with train speed and wind speed. The enhancement trends showed nonlinear phenomena and enhanced risk in the course of train movement. When the train travels at a high speed and encounters a huge cross wind, the influence involved by nonlinear risk increment will extremely impair safety of train. The following conclusion can also be drawn: The effect of aerodynamic lift makes restriction speed reduce, however, the influences of aerodynamic drag to the limit train speed rest on the direction of wind flow. When the wind blows from inner rail to outer rail, aerodynamic forces shall reduce the restriction speed, by contraries, when the wind blows from outer rail to inner rail, aerodynamic forces shall increase the restriction speed. | CHEN RuiLin ZENG QingYuan ZHONG XinGu XIANG Jun GUO XiaoGang ZHAO Gang | 2009 | Science China(Technological Sciences)2009，52，7： | 8 |
| 20 | Bifurcation\instability forms of high speed railway vehicles显示文摘The China high speed railway vehicles of type CRH2 and type CRH3, modeled on Japanese high speed Electric Multiple Units (EMU) E2 series and Euro high speed EMU ICE3 series possess different stability behaviors due to the different matching re-lations between bogie parameters and wheel profiles. It is known from the field tests and roller rig tests that, the former has a higher critical speed while large limit cycle oscillation appears if instability occurs, and the latter has lower critical speed while small limit cycle appears if instability occurs. The dynamic model of the vehicle system including a semi-carbody and a bogie is established in this paper. The bifurcation diagrams of the two types of high speed vehicles are extensively studied. By using the method of normal form of Hopf bifurcation, it is found that the subcritical and supercritical bifurcations exist in the two types of vehicle systems. The influence of parameter variation on the exported function Rec1(0) in Hopf normal form is studied and numerical shooting method is also used for mutual verification. Furthermore, the bifurcation situation, subcritical or supercritical, is also discussed. The study shows that the sign of Re(λ) determinates the stability of linear system, and the sign of Rec1(0) determines the property of Hopf bifurcation with Rec1(0)>0 for supercritical and Rec1(0)<0 for subcritical. | DONG Hao ZENG Jing XIE JianHua JIA Lu | 2013 | Science China(Technological Sciences)2013，56，7： | 7 |
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