Spectral analysis and self-adjusting mechanism for oscillation phenomenon in hydrogen-oxygen continuously rotating detonation engine

The continuously rotating detonation engine(CRDE)is a new concept of engines for aircraft and spacecraft.Quasi-stable continuously rotating detonation(CRD)can be observed in an annular combustion chamber,but the sustaining,stabilizing and adjusting mechanisms are not yet clear.To learn more deeply into the CRDE,experimental studies have been carried out to investigate hydrogen-oxygen CRDE.Pressure histories are obtained during each shot,which show that stable CRD waves are generated in the combustor,when feeding pressures are higher than 0.5 MPa for fuel and oxidizer,respectively.Each shot can keep running as long as fresh gas feeding maintains.Close-up of the pressure history shows the repeatability of pressure peaks and indicates the detonation velocity in hydrogen–oxygen CRD,which proves the success of forming a stable CRD in the annular chamber.Spectrum of the pressure history matches the close-up analysis and confirms the CRD.It also shows multi-wave phenomenon and affirms the fact that in this case a single detonation wave is rotating in the annulus.Moreover,oscillation phenomenon is found in pressure peaks and a self-adjusting mechanism is proposed to explain the phenomenon.     

机器人技术在机械加工中的应用

机器人取代机床从事机械加工已成为自动化加工发展的一大趋向。本文在分析工业机器人应用现状的基础上,提出了机器人加工系统存在的一些问题,还对并联机床的发展作了展望。     

高等院校贷款的风险规避与对策

高等院校为适应扩大招生规模的需要，大量举债，目前高校贷款总额已达1500亿-2000亿之间；银行认为贷款安全而主动与高校合作，可以得到回报；政府将为高校贷款（高校为公益事业）承担巨大风险。从高等院校公用、专项经费看，许多院校无力偿还贷款。希望各高校、银行、政府能够有所警示和启迪。     

浅谈银行信贷资产债权维护的配套设置

本文主要从强化商业银行内控、建立信贷资产债权保全机制、营造诚实信用环境三方面论述维护银行信贷资产债权的配套措施。     

Adaptive mesh refinement computation of acoustic radiation from an engine intake

A block-structured adaptive mesh refinement (AMR) method was applied to the computational problem of acoustic radiation from an aeroengine intake. The aim is to improve the computational and storage efficiency in aeroengine noise prediction through reduction of computational cells. A parallel implementation of the adaptive mesh refinement algorithm was achieved using message passing interface. It combined a range of 2nd- and 4th-order spatial stencils, a 4th-order low-dissipation and low-dispersion Runge–Kutta scheme for time integration and several different interpolation methods. Both the parallel AMR algorithms and numerical issues were introduced briefly in this work. To solve the problem of acoustic radiation from an aeroengine intake, the code was extended to support body-fitted grid structures. The problem of acoustic radiation was solved with linearised Euler equations. The AMR results were compared with the previous results computed on a uniformly fine mesh to demonstrate the accuracy and the efficiency of the current AMR strategy. As the computational load of the whole adaptively refined mesh has to be balanced between nodes on-line, the parallel performance of the existing code deteriorates along with the increase of processors due to the expensive inter-nodes memory communication costs. The potential solution was suggested in the end.     

欧洲一体化进程中的重大危机与解决机制

欧洲一体化是人类历史上第一个以国家联盟为基础的区域一体化国际组织,它不仅在实现欧洲和平、推动欧洲经济和社会发展方面具有重要意义,而且对世界经济和政治产生了深远的影响。欧洲一体化进程并非一帆风顺,出现过一些重大危机,但每次危机都被化解。正确处理建设中的危机与危机中建设之间的关系,原则性与灵活性相结合,以动态目标推动欧洲一体化进程,集团性和开放性相结合的整合机制,构建一个不可逆转的一体化框架体制,形成了欧洲一体化进程中化解危机的有效机制。     

高校协同创新型人才培养机制问题研究

高校协同创新型人才培养问题是基于胡锦涛在庆祝清华大学建校100周年大会上的重要讲话基础上,我国启动的“2011计划”过程中,伴随着我国协同创新问题的研究而出现的,它在协同创新领域的研究中具有重要的意义和地位.主要在分析了高校协同创新型人才的特点的基础上,提炼出高校协同创新型人才培养要素,根据各要素的作用,最终总结了构建高校协同创新型人才培养的机制.     

Ni含量对CuNiAl合金导电率及摩擦性能的影响

采用熔铸法制备CuNiAl合金,Cu含量为95wt%,Ni/Al原子比分别为1:3、1:2、1:1、2:1、3:1的CuNiAl合金。利用涡流电导仪和磨损试验机测量了不同状态合金的导电率。研究发现:CuNiAl合金随着Ni含量的逐渐增加,导电率减小,合金的黏着磨损减弱,磨粒磨损现象明显增加。     

Virtual target guidance-based distributed model predictive control for formation control of multiple UAVs

The paper proposes a Virtual Target Guidance (VTG)-based distributed Model Predictive Control (MPC) scheme for formation control of multiple Unmanned Aerial Vehicles (UAVs). First, a framework of distributed MPC scheme is designed in which each UAV only shares the information with its neighbors, and the obtained local Finite-Horizon Optimal Control Problem (FHOCP) can be solved by swarm intelligent optimization algorithm. Then, a VTG approach is developed and integrated into the distributed MPC scheme to achieve trajectory tracking and obstacle avoidance. Further, an event-triggered mechanism is proposed to reduce the computational burden for UAV formation control, which takes into consideration the predictive state errors as well as the convergence of cost function. Numerical simulations show that the proposed VTG-based distributed MPC scheme is more computationally efficient to achieve formation control of multiple UAVs in comparison with the traditional distributed MPC method.     

VSV调节机构阻滞力和调节精度的归因分析

基于ANCF方法和摩擦力的NURBS表达算法，构建了考虑装配间隙、尺寸公差、关键件柔性、热影响以及接触摩擦等因素的复杂VSV调节机构的刚柔耦合动力学模型，并依据部件空间分布关系和参数化表述开发了VSV调节机构的快速自动化建模流程，大大提升了建模效率。分别对VSV调节机构的单级模拟气动实验及热态联调实验状态进行了对比仿真，结果表明，所构建的VSV调节机构模型在阻滞力仿真方面具有较高的可信度，且气动力引起的摩擦力矩是造成机构阻滞力、角度调节迟滞和调节精度下降的主要原因，气动力矩对机构阻滞力和角度迟滞影响不明显，关键件柔性对阻滞力影响较小，但却是调节精度降低的内在因素。