检索结果-南通市图书馆

Novel backstepping design for blended aero and reaction-jet missile autopilot

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2008年第1期19卷 148-153页

作者： Liu Zhong jia xiaohong Opto-Electro Technology Development Center Luoyang 471009 P.R. China

The advanced missile uses blended control of nero-fin and reaction-jet to improve missile maneuverability. The blended control design, which is multi-inputs and multi-outputs （MIMO）, severe nonlinear, and model uncertain, is much more complex than conventional nero-fin control. A novel nonlinear backstepping control approach is proposed to design the blended autopilot. Missile model is reformed to a new one by state reconstruction technique so that it is easy to be handled by the backstepping method. Then a Lyapunov function is chosen to avoid oscillation caused in normal backstepping way when control parameters are mismatched. In distribution of both inputs, optimal energy logic is proposed. In addition, a fuzzy cerebellar model articulation controller （FCMAC） neural network is used to guarantee controller robustness to uncertainties. Finally, simulation results demonstrate the efficiency and advantages of the proposed method.

关键词： missile control blended aero-fin and reaction-jet control nonlinear backstepping optimal enery logic.

Real-Time Facial Pose Estimation and Tracking by Coarse-to-Fine Iterative Optimization

在线全文

学校读者我要写书评

暂无评论

Tsinghua Science and Technology 2020年第5期25卷 690-700页

作者： Xiaolong Yang xiaohong jia Mengke Yuan Dong-Ming Yan the Key Laboratory of Mathematics Mechanization Academy of Mathematics and Systems SciencesChinese Academy of SciencesBeijing 100190China the University of Chinese Academy of Sciences Beijing 100049China the National Laboratory of Pattern Recognition Institute of AutomationChinese Academy of SciencesBeijing 100190China

We present a novel and efficient method for real-time multiple facial poses estimation and tracking in a single frame or ***,we combine two standard convolutional neural network models for face detection and mean shape learning to generate initial estimations of alignment and ***,we design a bi-objective optimization strategy to iteratively refine the obtained *** strategy achieves faster speed and more accurate ***,we further apply algebraic filtering processing,including Gaussian filter for background removal and extended Kalman filter for target prediction,to maintain real-time tracking *** general RGB photos or videos are required,which are captured by a commodity monocular camera without any priori or *** demonstrate the advantages of our approach by comparing it with the most recent work in terms of performance and accuracy.

关键词： facial pose recognition facial pose estimation real-time tracking

Wind-proof and sand-fixing effects of Artemisia ordosica with different coverages in the Mu Us Sandy Land,northern China

在线全文

学校读者我要写书评

暂无评论

Journal of Arid Land 2022年第8期14卷 877-893页

作者： PANG Yingjun WU Bo jia xiaohong XIE Shengbo Institute of Desertification Studies Chinese Academy of ForestryBeijing 100091China Institute of Ecological Conservation and Restoration Chinese Academy of ForestryBeijing 100091China Key Laboratory of Desert Ecosystem and Global Change National Forestry and Grassland AdministrationBeijing 100091China Kumtag Desert Ecosystem Research Station National Forestry and Grassland AdministrationDunhuang 736200China Key Laboratory of Desert and Desertification Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China

Wind erosion is a key global environmental problem and has many adverse *** Mu Us Sandy Land of northern China is characterized by an arid climate,where vegetation patches and bare sand patches are usually distributed mosaically,and aeolian activities occur *** plays a significant role in controlling wind *** ordosica is the most dominant native plant species in the Mu Us Sandy *** is urgent to study the wind-proof and sand-fixing effects of Artemisia ordosica in the Mu Us Sandy *** study analyzed the wind-proof and sand-fixing effects of Artemisia ordosica based on the field data of wind regimes,aeolian sediment transport,and surface change of Artemisia ordosica plots with four coverages(denoted as site A,site B,site C,and site D)in the Mu Us Sandy Land during the period from 1 June 2018 to 29 June *** coverages of Artemisia ordosica at site A,site B,site C,and site D were 2%,16%,29%,and 69%,*** annual average wind speeds at 2.0 m height above the ground for site A,site B,site C,and site D were 3.47,2.77,2.21,and 1.97 m/s,*** annual drift potentials were 193.80,69.72,15.05,and 6.73 VU at site A,site B,site C,and site D,*** total horizontal aeolian sediment fluxes during the period from 2-3 June 2018 to 6 June 2019 at site A,site B,site C,and site D were 4633.61,896.80,10.54,and 6.14 kg/m,*** A had the largest surface changes,and the surface changes at site B were significantly weaker than those at site A,whereas the surface changes at site C and site D were *** results indicated that Artemisia ordosica significantly reduced the wind speed,drift potential,aeolian sediment transport,and surface *** higher the coverage of Artemisia ordosica is,the more obvious the effects of wind-proof and *** erosion would be effectively controlled in the Mu Us Sandy Land if the coverage of Artemisia ordosica is greater than 29%.These results provid

关键词： Artemisia ordosica wind-proof sand-fixing wind erosion aeolian sediment flux Mu Us Sandy Land

Spatiotemporal changes in terrestrial water storage in the Beijing-Tianjin Sandstorm Source Region from GRACE satellites

在线全文

学校读者我要写书评

暂无评论

International Soil and Water Conservation Research 2020年第3期8卷 295-307页

作者： Yingjun Pang Bo Wu Yanping Cao xiaohong jia Institute of Desertification Studies Chinese Academy of ForestryBeijing100091China Key Laboratory of Desert Ecosystem and Global Change State Administration of Forestry and GrasslandBeijing100091China The College of Environment and Planning of Henan University Kaifeng475004HenanChina

The Sandstorm Source Control Project in and around the Beijing-Tianjin region was one of the most important ecological projects in *** water storage(TWS)has important impacts on the ecological construction,agriculture,industry,and resident's *** on the Gravity Recovery and Climate Experiment(GRACE)data,meteorological and Moderate Resolution Imaging Spectroradiometer(MODIS)data,etc.,this paper analyzed spatiotemporal characteristics of TWS,groundwater storage,and precipitation,and explored the influencing factors of regional TWS combined with land use and land cover(LULC),social and economic *** most important results were as follows:(1)From 2003 to 2016,TWS in the Beijing-Tianjin Sandstorm Source Region showed a decreasing trend with a rate of 3.14 mm yr-1.(2)The TWS decline was caused mainly by groundwater overexploitation,but not pre-cipitation variation.(3)Spatiotemporal variations of TWS were related to *** area with the most serious decrease of TWS was mainly located in the southwestern part of the region,where farmland percentage and population density were greater.(4)Reducing the percent of farmland and tree planting,and adding the shrub and grass planting,could be a viable choice for the Beijing-Tianjin Sandstorm Source Control *** results provide a scientific basis for regional water resource and ecological management.

关键词： Terrestrial water storage Beijing-Tianjin Sandstorm Source Region Groundwater LULC

Empirical correction of kinetic model for polymer thermal reaction process based on first order reaction kinetics

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2021年第10期34卷 132-144页

作者： Zhaoxiang Zhang Fei Guo Wei Song xiaohong jia Yuming Wang State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084China Joint Research Center for Rubber and Plastic Seals Tsinghua UniversityBeijing 100084China State Key Laboratory of Advanced Forming Technology&Equipment China Academy of Machinery Science&TechnologyBeijing 100044China Tianding Sealing Technology(Beijing)Co. Ltd.Beijing 100072China

Based on the theory of first-order reaction kinetics,a thermal reaction kinetic model in integral form has been *** make the model more applicable,the effects of time and the conversion degree on the reaction rate parameters were *** types of undetermined functions were used to compensate for the intrinsic variation of the reaction rate,and two types of correction methods are *** model was explained and verified using published experimental data of different polymer thermal reaction systems,and its effectiveness and wide adaptability were *** the given kinetic model,only one parameter needs to be *** proposed empirical model is expected to be used in the numerical simulation of polymer thermal reaction process.

关键词： Thermal reaction Polymer processing Reaction kinetics Mathematical modeling Empirical correction

Tool Orientation Optimization and Path Planning for 5-Axis Machining

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science & Complexity 2021年第1期34卷 83-106页

作者： YUAN Chunming MI Zhenpeng jia xiaohong LIN Fengming SHEN Liyong KLMM Academy of Mathematics and Systems SciencesChinese Academy of SciencesBeijing 100190China School of Mathematical Sciences University of Chinese Academy of SciencesBeijing 100049China

Tool path generation is a fundamental problem in 5-axis CNC machining, which consists of tool orientation planning and cutter-contact(CC) point planning. The planning strategy highly depends on the type of tool cutters. For ball-end cutters, the tool orientation and CC point location can be planned separately;while for flat end cutters, the two are highly dependent on each other. This paper generates a smooth tool path of workpiece surfaces for flat end mills from two stages: Computing smooth tool orientations on the surface without gouging and collisions and then designing the CC point path. By solving the tool posture optimization problem the authors achieve both the path smoothness and the machining efficiency. Experimental results are provided to show the effectiveness of the method.

关键词： 5-axis CNC machining flat end cutter tool path planning tool posture optimization

Effect of contact forms on the wear of hard silicon surfaces by soft polymers

在线全文

学校读者我要写书评

暂无评论

Friction 2021年第5期9卷 918-928页

作者： Zhaoxiang ZHANG xiaohong jia Fei GUO Zhongde SHAN Yuming WANG State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084China Joint Research Center for Rubber and Plastic Seals Tsinghua UniversityBeijing 100084China State Key Laboratory of Advanced Forming Technology&Equipment China Academy of Machinery Science&TechnologyBeijing 100044China

The mechanism of hard surfaces worn by soft polymers is not clearly *** this paper,a new hypothesis has been proposed,it holds that the stress acting on the hard surface under certain working conditions is the main reason for wear of the hard surface by a soft *** hypothesis was investigated by changing the contact form between *** this,friction tests between six polymer spheres and smooth,rough,and inclined monocrystalline silicon surfaces were carried *** results show that for the same tribo-pair,the silicon surface will not be worn in some contact forms,but in other contact forms it will be *** believe the wear of hard surface by a soft polymer is the result of the combined stress state action on the hard surface.

关键词： polymers silicon surface wear combined stress

The effect of texture on the shaft surface on the sealing performance of radial lip seals

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2014年第7期57卷 1343-1351页

作者： GUO Fei jia xiaohong GAO Zhi WANG YuMing State Key Laboratory of Tribology Tsinghua University

On the basis of elastohydrodynamic model,the present study numerically analyzes the effect of various microdimple texture shapes,namely,circular,square,oriented isosceles triangular,on the pumping rate and the friction torque of radial lip seals,and determines the microdimple texture shape that can produce positive pumping *** area ratio,depth and shape dimension of a single texture are the most important geometric parameters which influence the tribological *** to the selected texture shape,parameter analysis is conducted to determine the optimal combination for the above three ***,the simulated performances of radial lip seal with texture on the shaft surface are compared with those of the conventional lip seal without any texture on the shaft surface.

关键词： rotary lip seal elastohydrodynamics surface texture pumping rate friction torque

Effects of the radial force on the static contact properties and sealing performance of a radial lip seal

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2014年第6期57卷 1175-1182页

作者： jia xiaohong GUO Fei HUANG Le WANG LongKe GAO Zhi WANG YuMing State Key Laboratory of Tribology Tsinghua University Guangzhou Mechanical Engineering Research Institute Co. Ltd. Eaton Corporation

The radial force is a critical factor to determine the sealing performance of radial lip *** effects of radial force produced by garter spring and interference on the static contact properties and sealing performance of a radial lip seal are investigated by numerical simulations and ***-element analysis and mixed elastohydrodynamic lubrication simulation are *** force,contact width,temperature in the sealing zone,the reverse pumping rate and friction torque are measured.A critical value of interference for a cost-effectively designed radial lip seal is *** force is required to compensate the decrease of the radial force because of the interference and used as a possible way to obtain intelligent control of sealing *** quantitative results gotten in this study could provide guide for the seal design and improvement.

关键词： lip seal radial force static contact properties pumping rate friction torque