液体火箭增压输送系统多学科动力学研究

通过多学科动力学建模方法研究,首先建立了平台供气系统机械、气动与控制动力学特征模型,并对不同工况下系统动态性能进行数值仿真,着重研究调压压力、系统阻尼、充压方式、管路特性等对系统动态稳定性的影响,为系统动态稳定性分析及稳定性改进提高提供指导;最后结合某型号飞行过程中增压系统故障问题,建立了冷氦增压系统机械、气动、电磁、热与控制多学科动力学仿真分析模型,通过系统流量及压降分析进行故障定位,进一步探讨多学科动力学仿真在增压输送系统中的应用.     

突发事故下交通拥堵控制策略

突发事故在城市交通网络中经常发生,对交通系统的正常运行带来极大影响,因此研究突发事故下交通拥堵的控制策略具有十分重要的意义.本文研究突发事故下临时性车辆禁行的设计问题.文中建立了临时性车辆禁行设计的双层规划模型,上层目标从交通管理者的角度最小化出行者的系统总阻抗,下层通过基于元胞传输模型的仿真描述在临时性车辆禁行下的出行者的动态路径选择行为,并提出了基于遗传算法的求解方法.计算结果表明,本文提出的临时性车辆禁行控制措施能够有效的降低突发事故所导致的交通拥堵,提高交通网络的系统性能.     

基于零和微分博弈的航天器相对位置容错控制

针对带有执行器偏置故障和失效故障的航天器相对位置控制系统,本文提出了一种基于零和微分博弈的最优容错控制方法.首先,利用线性二次调节设计反馈控制器以保证无故障时系统的渐近稳定性能;其次,将航天器相对位置容错控制问题转换为零和微分博弈问题,结合Hamilton-Jacobi-Issac (HJI)方程和极小极大原则设计最优控制律;最后,利用自适应动态规划方法设计评判网络对最优性能函数进行估计,构成自适应控制信号,保证了系统稳定性和状态最终一致有界.仿真结果表明了本文设计的容错控制律的有效性.     

四轮转向车辆分数阶控制方法研究

四轮转向系统(4WS)可根据前轮转向和车辆的状态通过后轮的转向提高车辆转弯能力, 同样, 利用这一转向系统可以改进车辆的横向稳定性和操纵性能. 当前轮转向相同时四轮转向车辆的转弯半径大于两轮转向, 而且普通的控制方法不考虑前轮转向的动态过程影响. 本文利用分数阶导数理论提出一种新的四轮转向控制方法, 其不仅考虑前轮转角和横摆角速度的大小, 而且也考虑到转向角速度的影响. 同时也给出控制方法的一些设计方法, 数值计算结果验证了该控制方法的有效性. 通过对两轮转向和四轮转向的转弯车辆的侧偏角、车辆绕质心的横摆角速度和转弯半径等动力学和运动学特性的计算结果比较, 本文的控制方法对四轮转向车辆在转向过程中的瞬态响应有所改进, 并减小了转弯半径.     

无人驾驶车辆横向控制策略研究进展

国务院《新一代人工智能发展规划》指出无人驾驶技术是发展新一代人工智能的重点任务之一。以无人驾驶车辆横向控制的试验和相关研究成果为基础,分析了无人驾驶车辆的研究动态,分别从经典控制、现代控制、智能控制、横纵向综合控制4个方面阐述了无人驾驶车辆的横向控制策略。分析结果表明:考虑无人驾驶车辆系统的非线性、时变特性和不确定性,发展数据驱动控制、多种控制策略和智能算法的结合使用将是无人驾驶车辆横向控制的研究热点,特别是横向和纵向动力学的多系统协同控制,将是今后的研究重点。     

轴流压气机变工况导叶/静叶/转速联调规律探索

本文采用实验研究方法,在导静叶可调、三级、低速、轴流压气机实验台上,分析了导叶/静叶安装角调节对压气机设计工况及非设计工况下性能的影响,主要以压气机的效率和稳定裕度作为优化目标考察其规律的变化.研究结果表明：通过优化导/静叶安装角的匹配,可有效改善压气机非设计工况下的性能,尝试了采用DSP（动态数据处理）技术,依据转速与动叶攻角的对应关系,在线实现了导/静叶安装角的调节.     

基于S3C2416的公交电子站牌系统设计

为了提高城市公交的运营效率和服务质量,让乘客及时了解公交车实时车况,设计了一种基于S3C2416微处理器的新型公交电子站牌系统,并对该系统的组成、工作原理、关键技术及主要模块的软硬件设计进行了详细的阐述.系统以ARM为嵌入式硬件平台,采用当前先进的嵌入式技术和GPRS无线网络通信技术,实现了车辆到站预报、车辆到站提示、公交站点查询、公交车次查询等功能.测试结果表明,该系统性能良好、实时性强、稳定性高,具有巨大的市场价值.     

基于模糊PID的数字控制在DC／DC变换器中的应用

针对DC／DC变换器这种非线性系统,提出了一种基于模糊PID的数字控制方法。该方法通过对输出电压的偏差及偏差变化率的识别,进行模糊推理,实现对PID控制器参数的在线调节。电流连续模式和断续模式下的Buck变换器仿真结果表明,该方法能有效减小系统的超调量,提高系统的响应速度,缩短系统的调节时间,增强控制系统的动态性能。     

随机非线性系统二次跟踪型风险灵敏度指标下的满意输出反馈控制设计

在无限时区跟踪型风险灵敏度(risk-sensitive)指标下, 研究了一类严格反馈随机非线性系统的满意输出反馈控制问题. 所用指标函数为实际中常见的二次型函数, 而非为回避控制器设计及闭环系统性能分析的本质困难而采用的四次型函数. 对任意给定的风险灵敏度参数和期望指标值, 利用积分反推(integrator backstepping)方法构造性地给出了一个输出反馈控制器, 使得闭环系统在概率意义下有界, 并且风险灵敏度指标不大于所给的期望值.     

雷达信号的加速度分辨性能分析

针对以导弹和卫星等高速飞行器为平台的雷达信号处理应用中所面临的非匀速相对运动所引起的多项式相位调制给雷达信号处理带来的影响, 提出并研究了加速度模糊函数和加速度分辨力的有关概念. 并以加速度模糊函数为分析工具, 讨论了雷达信号的加速度分辨性能, 分析了未知加速度对线性相位匹配滤波器输出信噪比和Doppler频率估计精度的影响, 给出了加速度与最优相参积累时间之间的定量关系, 讨论了二次相位匹配滤波器对加速度参数搜索估计的性能.     

掘进机新型液压油箱的设计与应用

液压油液的温升与污染是制约液压系统可靠性与液压元件寿命的关键。为了减小因油箱的设计缺陷而引起的油液污染速度快,温升高的问题,对EBZ230掘进机泵站闭式油箱进行改进设计。通过样机的应用与实验证明了这种新型的油箱系统能更有效地降低油液的污染速度与等级、更平稳更快速地冷却油液,对提高整机液压系统可靠性与稳定性有非常积极的意义。该油箱结构亦可应用于有着相似要求的液压设备中,具有较高的推广价值。     

深海海水液压系统的研究现状与前景

分析了在深海工具中以海水为压力介质的液压系统与传统的油压系统相比所具有的突出优越性,并介绍了深海液压系统在国内外的研究发展现状及其当前急需解决的几个关键技术难题和未来发展前景。     

板材液压拉深试验装置开发

开发了一种用于板材液压拉深成形性能研究的试验装置,包括拉深模具及液压控制系统。该装置不需要复杂的外部供液系统、压边系统及凸模导向系统,在普通的单动压力机上就能实现对不同材料及尺寸板材的普通拉深和液压拉深试验。初步的试验表明,该装置结构简单、操作方便、工作可靠,满足板材液压拉深试验要求,能够有效的改善板材的成形性能。     

Polar transport of the plant hormone auxin – the role of PIN-FORMED (PIN) proteins

The PIN-FORMED (PIN) protein family is a group of plant transmembrane proteins with a predicted function as secondary transporters. PINs have been shown to play a rate-limiting role in the catalysis of efflux of the plant growth regulator auxin from cells, and their asymmetrical cellular localization determines the direction of cell-to-cell auxin flow. There is a functional redundancy of PINs and their biochemical activity is regulated at many levels. PINs constitute a flexible network underlying the directional auxin flux (polar auxin transport) which provides cells in any part of the plant body with particular positional and temporal information. Thus, the PIN network, together with downstream auxin signalling system(s), coordinates plant development. This review summarizes recent progress in the elucidation of the role of PIN proteins in polar auxin transport at the cellular level, with emphasis on their structure and evolution and regulation of their function. Received 28 December 2006; received after revision 16 February 2007; accepted 26 March 2007     

Peritoneal macrophages from adjuvant arthritic rats enhance tumour cell growth in vitro.

Peritoneal macrophages from rats with adjuvant arthritis enhance the incorporation of 3H-thymidine in 2 tumour cell lines in vitro. Maximal enhancement is found during the development of the secondary lesions, and it is suggested that the immunologic commitment of the macrophages could interfere with their regulation of tumour cell proliferation in vivo.     

Lactoferrin

Lactoferrin (LF) is a member of the transferrin family that is expressed and secreted by glandular epithelial cells and is found in the secondary granules of neutrophils. Originally viewed as an iron-binding protein in milk, with bacteriostatic properties, it is becoming increasingly evident that LF is a multifunctional protein to which several physiological roles have been attributed. These include regulation of iron homeostasis, host defense against a broad range of microbial infections, anti-inflammatory activity, regulation of cellular growth and differentiation and protection against cancer development and metastasis. While iron binding is likely central to some of the biological roles of LF, other activities, including specific interactions with mammalian receptors and microbial components, also contribute to the pleoitropic functional nature of this protein. In this article, recent advances in the understanding of these functions at the cellular and molecular level are discussed.     

Assembly of MHC class I peptide complexes from the perspective of disulfide bond formation

Assembly of functional major histocompatibility complex (MHC) class I peptide complexes within the endoplasmic reticulum is critically important for the development of an adaptive immune response. The highly regulated loading of peptides onto MHC class I molecules is controlled by a multi-component chaperone system called the MHC class I peptide loading complex. The recent identification of the thioredoxin family member ERp57 as a component of the loading complex led to an interesting question: Why is there a thiol-disulfide oxidoreductase inside a complex dedicated to inserting peptides into a receptor binding site? Most recently, specific ERp57-mediated disulfide bond rearrangements have been identified inside the loading complex. What these biochemical events mean for the peptide loading process remains a matter of conjecture. While several important questions wait to be answered, this review intends to summarize our current view of the oxidative folding of MHC class I molecules and addresses the question of how the receptor ligand interaction might be regulated by thiol-based redox reactions.     

利用Hydrus-1D反推土壤水力参数方法分析

预测分析非饱和土壤水分运动特征必须首先获得土壤水力参数,而且土壤水力参数的准确性决定着与这些参数有关的土壤水分运动的数值模型的准确性。本文依据一维积水入渗试验的累积入渗量资料利用Hydrus-1D软件反推土壤水力特性参数,利用反推的土壤水力特性参数和Hydrus-1D软件对一维积水入渗过程的累积入渗量、入渗率、湿润深度、含水量分布进行模拟并与实测值进行对比,结果显示,土壤累积入渗量、入渗率、湿润锋、含水量分布的实测数据与模拟数据之间的平均相对误差均在2％～15％之间,软件模拟数据与试验实测教据基本吻合,这说明利用Hydrus-1D软件在反推土壤水力特性参数及模拟土壤水分运动方面是可行的。     

Melatonin,mitochondria and hypertension

Melatonin, due to its multiple means and mechanisms of action, plays a fundamental role in the regulation of the organismal physiology by fine tunning several functions. The cardiovascular system is an important site of action as melatonin regulates blood pressure both by central and peripheral interventions, in addition to its relation with the renin–angiotensin system. Besides, the systemic management of several processes, melatonin acts on mitochondria regulation to maintain a healthy cardiovascular system. Hypertension affects target organs in different ways and cellular energy metabolism is frequently involved due to mitochondrial alterations that include a rise in reactive oxygen species production and an ATP synthesis decrease. The discussion that follows shows the role played by melatonin in the regulation of mitochondrial physiology in several levels of the cardiovascular system, including brain, heart, kidney, blood vessels and, particularly, regulating the renin–angiotensin system. This discussion shows the putative importance of using melatonin as a therapeutic tool involving its antioxidant potential and its action on mitochondrial physiology in the cardiovascular system.     

基于Solidworks／Matlab的液压伺服扭转试验机系统联合建模与仿真

针对液压伺服扭转试验机系统，提出一种基于Solidworks／Matlab的系统联合建模与仿真方法，通过机构的实体造型建立机构模型并进行仿真。该建模方法具有较高的准确性与便捷性。分别在位置闭环与力闭环控制器的作用下，对系统的响应性能进行仿真分析，验证了液压伺服扭转试验机系统的可行性，为液压扭转试验机系统的设计提供理论依据。