检索结果-南通市图书馆

Chinese Journal of Aeronautics 2024年第10期37卷 275-293页

作者： Qi yu Wanchun CHEN wenbin yu School of Astronautics Beihang UniversityBeijing 102206China

In the scenario that a solid-fuel launch vehicle maneuvers in outer space at high angles of attack and sideslip for energy management,Approximate Analytical Solutions(AAS)for the threedimensional(3D)ascent flight states are derived,which are the only solutions capable of considering time-varying Mass Flow Rate(MFR)at *** uneven MFR makes the thrust vary nonlinearly and thus increases the difficulty of the problem *** AAS are derived based on a 3D Generalized Ascent Dynamics Model(GADM)with a normalized mass as the independent *** simplify some highly nonlinear terms in the GADM,several approximate functions are introduced carefully,while the errors of the approximations relative to the original terms are regarded as minor ***,a finite series with positive and negative exponents,called Exponent-Symmetry Series(ESS),is proposed for function approximation to decrease the highest exponent in the AAS so as to reduce computer round-off *** calculate the ESS coefficients,a method of seeking the Optimal Interpolation Points(OIP)is proposed using the leastsquares-approximation *** to the artful design of the approximations,the GADM can be decomposed into two analytically solvable subsystems by a perturbation method,and thus the AAS are obtained ***,to help implement the AAS,two indirect methods for measuring the remaining mass and predicting the burnout time in flight are put forward using information from *** results verify the superiority of the AAS under the condition of time-varying MFR.

关键词： Approximate analytical solutions 3D ascent trajectory Solid-fuel launch vehicle Uneven thrust Energy management

Current-Aided Multiple-AUV Cooperative Localization and Target Tracking in Anchor-Free Environments

在线全文

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2023年第3期10卷 792-806页

作者： Yichen Li wenbin yu Xinping Guan Department of Automation Shanghai Jiao Tong UniversityShanghai 200240 Key Laboratory of System Control and Information Processing Ministry of Education of ChinaShanghai Jiao Tong UniversityShanghai 200240China IEEE

In anchor-free environments,where no devices with known positions are available,the error growth of autonomous underwater vehicle(AUV)localization and target tracking is unbounded due to the lack of references and the accumulated errors in inertial *** paper aims to improve the localization and tracking accuracy by involving current information as extra *** first integrate current measurements and maps with belief propagation and design a distributed current-aided message-passing scheme that theoretically solves the localization and tracking *** on this scheme,we propose particle-based cooperative localization and target tracking algorithms,named CaCL and CaTT,*** AUV localization,CaCL uses the current measurements to correct the predicted and transmitted position information and alleviates the impact of the accumulated errors in inertial *** target tracking,the current maps are applied in CaTT to modify the position prediction of the target which is calculated through historical *** effectiveness and robustness of the proposed methods are validated through various simulations by comparisons with alternative methods under different trajectories and current conditions.

关键词： Anchor-free belief propagation cooperative localization current-aided target tracking

3D Localization for Multiple AUVs in Anchor-Free Environments by Exploring the Use of Depth Information

在线全文

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2024年第4期11卷 1051-1053页

作者： Yichen Li wenbin yu Xinping Guan the Department of Automation Shanghai Jiao Tong UniversityShanghai 200240 the Key Laboratory of System Control and Information Processing Ministry of Education of ChinaShanghai Jiao Tong UniversityShanghai 200240China

Dear Editor,This letter investigates the cooperative localization problem for multiple autonomous underwater vehicles(AUVs)in underwater anchor-free environments,where AUV localization errors grow without bound due to the accumulated errors in inertial measurements(termed accumulated errors hereafter)and the lack of anchors(with known positions).

关键词： AUVs underwater hereafter

A progress review of practical soot modelling development in diesel engine combustion

在线全文

学校读者我要写书评

暂无评论

Journal of Traffic and Transportation Engineering(English Edition) 2020年第3期7卷 269-281页

作者： Feiyang Zhao Wenming Yang wenbin yu Department of Mechanical Engineering National University of SingaporeSingapore 117575Singapore

Great efforts have been made over the last few decades in understanding of the mechanisms and phenomenology of soot formation and burnout in combustion *** this paper,theoretical advances in modelling soot formation and oxidation under engine circumstance are surveyed based on the published works,particularly focus on the practical soot modelling coupled with engine computational fluid dynamics(CFD)numerical *** types of soot models can be divided up into three main groups:empirical,semi-empirical and detailed soot *** the development of computing technology and increasingly comprehensive soot fundamental knowledge,the semi-empirical phenomenological soot model with major generic processes of soot formation was proposed,which is one of the most extensively investigated soot models in recent *** is highlighted with solving mathematical equations to get soot particle number density,soot volume and mass *** coupled with fuel chemistry,the detailed soot model seeks to predict soot characteristics based on molecule structure,bringing further insight of the soot evolution and transient behavior of soot-relevant ***,the sooting tendency from engine combustion fueled with alternative and oxygenated fuels are able to be further explored,which is conductive to propose new engine technologies for soot mitigation and future fuel strategy.

关键词： Engine combustion Alternative fuel Numerical modelling Soot formation

The Compaction Characteristics of Hot Mixed Asphalt Mixtures

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2014年第5期29卷 956-959页

作者：高英 HUANG Xiaoming yu wenbin School of Transportation Southeast University Zhuhai Highway Bureau

The quality of compaction is important to the performance of hot mixed asphalt （HMA） pavement. Most premature failures of asphalt pavement are concerned with poor compaction. Compaction characteristic of lIMA mixtures were studied. Compaction tests were done with typical widely used HMA mixtures, including dense gradation asphalt mixtures with different nominal maximum aggregate size （AC13,AC20,AC25）, and mixtures with different gradation （AC13, SMA13,Supl3 and OGFC13）. HMA mixtures were sampled at different compaction temperature and Marshall blow numbers, varying between 60 and 175 ~C and between 15 and 75 lows, respectively. The compaction characteristics of these mixtures were evaluated. The results showed that the Marshall stability and volumetric properties were significantly affected by the compaction temperature. Mixtures with the same NMAS but different type of gradation need different compaction energy to get the designed density.

关键词： compaction characteristic hot mixed asphalt compaction temperature marshall blow number gradation

The effects of clay minerals and organic matter on nanoscale pores in Lower Paleozoic shale gas reservoirs, Guizhou, China

在线全文

学校读者我要写书评

暂无评论

Acta Geochimica 2018年第6期37卷 791-804页

作者： yuantao Gu Quan Wan wenbin yu Xiaoxia Li Zhongbin yu State Key Laboratory of Ore Deposit Geochemistry Institute of Geochemistry Chinese Academy of Sciences School of Resource and Environment Henan University of Engineering

In organic-rich gas shales, clay minerals and organic matter(OM) have significant influences on the origin, preservation, and production of shale gas. Because of the substantial role of nanoscale pores in the generation,storage, and seepage of shale gas, we examined the effects of clay minerals and OM on nanoscale pore distribution characteristics in Lower Paleozoic shale gas *** the Niutitang and Longmaxi shales as examples, we determined the effects of clay minerals and OM on pores through sedimentation experiments. Field emission–scanning electron microscopy combined with low-pressure N2 adsorption of the samples before and after sedimentation showed significant differences in pore location and pore size distribution between the Niutitang and Longmaxi shales. Nanoscale pores mostly existed in OM in the Longmaxi shale and in clay minerals or OM–clay composites in the Niutitang shale. The distribution differences were attributed largely to variability in thermal evolution and tectonic development and might account for the difference in gas-bearing capacity between the Niutitang and Longmaxi reservoirs. In the nanoscale range, mesopores accounted for 61–76% of total nanoscale pore *** developed nanoscale pores in OM were distributed in a broad size range in the Longmaxi shale, which led to good pore connectivity and gas *** narrow pores(i.e., pores \ 20 nm) in OM–clay composites were found in the Niutitang shale, and might account for this shale's poor pore connectivity and low gas production efficiency. Enhancing the connectivity of the mesopores(especially pores \ 20 nm and those developed in OM–clay composites) might be the key to improving development of the Niutitang shale. The findings provide new insight into the formation and evolutionary mechanism of nanoscale pores developed in OM and clay minerals.

关键词： Nanoscale pore Clay minerals Organic matter OM-clay composites Pore distribution characteristics Pore connectivity

Effects of mixture inhomogeneity and combustion temperature on soot surface activity and soot formation in diesel engines

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2014年第3期57卷 452-460页

作者： ZHAO FeiYang yu wenbin PEI YiQiang SU WanHua State Key Laboratory of Engines Tianjin University

The soot surface growth plays significant role on the soot mass accumulation,which starts with H(hydrogen)atom abstraction forming activated soot surface sites,and is followed by the acetylene addition *** this study,the effect of the mixture inhomogeneity and combustion temperature on the soot surface activity and soot formation was investigated by developing a new multi-step phenomenological(MSP)soot model of diesel engines.A new detailed soot surface growth mechanism was proposed by correlation analysis of combustion parameters with soot *** inhomogeneity coefficient of soot surface activityαCH and the specific rate of soot surface growth R CH were derived to highlight the effect of inhomogeneity of mixture and combustion temperature on soot *** predicted diesel engine-out soot agreed well with experimental findings in wide ranges of combustion *** the case of lower engine load with single fuel injection and higher EGR(exhaust gas recirculation)rate,it had quiet homogeneous mixtures before ignition when the combustion temperature dominated the soot surface *** medium engine load with multi-pulse fuel injections,it got mixture slightly stratified before ignition and revealed that the mixture inhomogeneity became more dominated on soot surface activity than the combustion *** increased soot surface activity led to increased soot *** the full engine loads with single fuel injection but quite high boost pressure over 0.4 MPa,it led to the combustion conditions of higher mixture density and higher mixture heat capacity,which benefits the mixture *** decay rate of soot surface activity became lower due to the decreased combustion temperature and the soot surface activity decreased due to improved mixture *** addition,the lowered intake oxygen concentration due to usage of EGR played a role to lower the specific rate of soot surface growth R CH,but to increase the soot surface acti

关键词： soot model soot surface growth soot surface activity mixture inhomogeneity soot emission diesel engine

Optimal terminal guidance for exoatmospheric interception

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2016年第4期29卷 1052-1064页

作者： yu wenbin Chen Wanchun Yang Liang Liu Xiaoming Zhou Hao School of Astronautics Beihang University

In this study, two optimal terminal guidance (OTG) laws, one of which takes into account the final velocity vector constraint, are developed for exoatmospheric interception using optimal control theory. In exoatmospheric interception, because the proposed guidance laws give full consideration to the effect of gravity, they consume much less fuel than the traditional guidance laws while requiring a light computational load. In the development of the guidance laws, a unified optimal guidance problem is put forward, where the final velocity vector constraint can be considered or neglected by properly adjusting a parameter in the cost function. To make this problem analytically solvable, a linear model is used to approximate the gravity difference, the difference of the gravitational accelerations of the target and interceptor. Additionally, an example is provided to show that some achievements of this study can be used to significantly improve the fuel efficiency of the pulsed guidance employed by the interceptor whose divert thrust level is fixed. (C) 2016 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.

关键词： Exoatmospheric interception Explicit guidance Guidance Optimal control Proportional navigation Pulsed guidance

Mineral Surface after Reaction with Aqueous Solution at High Temperatures and Pressures

在线全文

学校读者我要写书评

暂无评论

Acta Geologica Sinica(English Edition) 2000年第2期74卷 406-411页

作者： ZHANG Xuetong ZHANG Ronghua HU Shumin yu wenbin Open Research Laboratory of Geochemical Kinetics Chinese Academy of GeologicalSciences26 Baiwanzhuang RoadBeijing 100037

This work presents new experimental results on surface chemistry of reacting minerals and interface kinetics between mineral and aqueous solutions. These experiments were carried out using a flow reactor (packed bed reactor) of an open system as well as a continuous stirred tank reactor, CSTR. The authors measured reaction rates of such minerals as zeolite, albite and carbonate (rhodochrosite, dolomite) in various solutions, and tested corresponding mineral surface by using SEM, XPS, SIMS, etc. This paper mainly presents the experimental results of zeolite dissolution in water and in low pH solutions at room temperature, and dolomite dissolution at elevated temperatures. The results show that the release rates of Si, Al and Na of zeolite are different in most cases. The incongruent dissolution of zeolite is related to surface chemical modifications. The Na, Al and Si release rates for dissolution of albite and zeolite in water and various solutions were measured as a function of temperature, flow velocity, pH and solution composition in the reaction system. In most cases, dissolutions of both albite and zeolite are incongruent. Dissolution of dolomite is also incongruent in most cases and varied with T, pH, and nature of aqueous solutions. For dolomite dissolution, the release rates of Mg are less than those of Ca at high temperatures as T increases from 25 to 300°C. SIMS study indicates that the contents of Al, Na and Si in the leached layer of zeolite or albite surface, change with the distance from the surface, exhibiting a non-linear behaviour within a thickness range of 1000%. The distributions of Ca, Mg, Mn, H and Cl in the leached surface layer of carbonate have a non-linear behaviour too.

关键词： mineral surface kinetics liquid/solid interface reaction

Existing form and effect of zirconium in pure Mg,Mg-Yb,and Mg-Zn-Yb alloys

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2009年第3期28卷 289-296页

作者： yu wenbin HE Hong LI Chunmei LI Qing LIU Zhiyi QIN Bing School of Materials Science and Engineering Southwest University Chongqing 400715 China School of Materials Science and Engineering Central South University Changsha 410083 China

The existing form and grain refining effects of small zirconium addition in pure Mg, Mg-Yb and Mg-Zn binary alloys, and Mg-Zn-Yb ternary alloy （ZK60-Yb） were investigated. The results show that Zr element exists mainly in single and cluster particles of pure α-Zr or Zn-Zr compounds inside grains and at grain boundaries. Only the particles located in the interior of grains can act as the nucleus for α-Mg growth and effectively promote the formation of fine equiaxed grains. The broken and dispersed Zr-rich particles produced during the hot extrusion process can form nebulous banded structure in which these fine particles may act as obstacles to dislocation motion in wrought magnesium alloys.

关键词： magnesium alloys zirconium grain refinement microstructure ytterbium