运载火箭全箭动特性三维建模技术

目前国内运载火箭动力学特性建模以梁模型为主,但梁模型是对运载火箭三维结构的一种简化,存在若干弊端.采用三维建模方法可以克服这些弊端.总结了作者近几年开展的运载火箭三维建模的研究工作,提出了运载火箭三维建模方法,包括硬壳与半硬壳结构建模方法、夹芯结构建模方法、发动机架及发动机建模方法、燃料液体建模方法、非结构质量建模方法以及连接建模方法.尤其针对液体建模,提出了燃料液体杆单元建模方法,使液体建模工作大为简化.通过工程实例应用以及和试验的对比,证明了建模方法的适用性.同时也提出了运载火箭建模当中的不确定因素.     

Stock market volatility and the forecasting performance of stock index futures

This study attempts to apply the general equilibrium model of stock index futures with both stochastic market volatility and stochastic interest rates to the TAIFEX and the SGX Taiwan stock index futures data, and compares the predictive power of the cost of carry and the general equilibrium models. This study also represents the first attempt to investigate which of the five volatility estimators can enhance the forecasting performance of the general equilibrium model. Additionally, the impact of the up‐tick rule and other various explanatory factors on mispricing is also tested using a regression framework. Overall, the general equilibrium model outperforms the cost of carry model in forecasting prices of the TAIFEX and the SGX futures. This finding indicates that in the higher volatility of the Taiwan stock market incorporating stochastic market volatility into the pricing model helps in predicting the prices of these two futures. Furthermore, the comparison results of different volatility estimators support the conclusion that the power EWMA and the GARCH(1,1) estimators can enhance the forecasting performance of the general equilibrium model compared to the other estimators. Additionally, the relaxation of the up‐tick rule helps reduce the degree of mispricing. Copyright © 2008 John Wiley & Sons, Ltd.     

The ‘nec plus ultra’ of precision measurement: Geodesy and the forgotten purpose of the Metre Convention

Geodesy—the determination of the size and shape of the earth—has often been the science operating at the frontier of precision in the measurement of length. Its contribution to the technologies and standards of length measurement has, however, been underestimated in the literature. That, instead, places emphasis on the on the creation and international acceptance of the metric system as a whole. By new research into the standards-in-use of the community of geodesists, I rediscover the original purpose of the Metre Convention of 1875, and show for the first time the significant influence of geodesy on the standardisation of length measurement thereafter. I emphasise the role of the coherence of the web of measurement in the context of change and improvement in standards.     

Greek angles from Babylonian numbers

Models of planetary motion as observed from Earth must account for two principal anomalies: the nonuniform speed of the planet as it circles the zodiac, and the correlation of the planet’s position with the position of the Sun. In the context of the geometrical models used by the Greeks, the practical difficulty is to somehow isolate the motion of the epicycle center on the deferent from the motion of the planet on its epicycle. One way to isolate the motion of the epicycle center is to determine the longitude and time of oppositions of the planet with the mean Sun. A Greek astronomer might have realized that the predictions of mean oppositions by Babylonian models could serve as useful proxies for real empirical observations. It is shown that a Greek astronomer with a reasonable understanding of Babylonian System A models for the outer planets and the Sun–Moon could have used those models to estimate approximate values for the eccentricity e and longitude of apogee A required for geometrical models. The same method would work for the inner planets if conjunctions were observable, but they are not, and the variation of the observable synodic events—first and last morning and evening visibilities—is dominated more by the motion of the planet in latitude than the nonuniform motion of the epicycle center.     

The Chemistry of the Universe: Historical Roots of Modern Cosmochemistry

During the second half of the twentieth century, the domain of geochemistry has greatly expanded and the field is today often seen as a branch of an extended chemistry of the Earth, called cosmochemistry. This paper is a historical introduction to cosmochemistry in which the wider cosmic aspects are surveyed up to about 1915, when nuclear physics changed the scene. These wider aspects or themes include, firstly, the attempts to determine the relative abundances of the elements, secondly, the extension of geochemistry to include physical geochemistry, thirdly, the study of meteorites and, fourthly, the spectroscopic study of the stars within the astrochemical tradition. Because of the lack of reliable data, a great deal of the protocosmochemistry described in the present paper was speculative. Nonetheless, by 1915 the contours of the cosmochemistry of the future were just visible and the developments here singled out can thus be seen as belonging to the prehistory of modern cosmochemistry.     

基于iSCSI协议的远程灾备安全模型研究

本文分析了基于iSCSI协议的灾备模型的特点及其存在的安全隐患。为了解决该模型存在的安全问题，提出了基于iSCSI协议的远程灾备安全模型。其主要设计思想是在传输线路和本地存储网络以及远程灾备网络的接口处设置防火墙．用以提高两个存储网络的抗攻击能力，利用VPN来对传输的数据进行加密，从而保证数据的安全。最后通过实验验证了该模型数据传输的安全性和具有良好的抗攻击能力。     

基于MAXScript的三维海面动画生成研究

随着计算机技术的发展,三维动画影片已经逐步替代传统二维动画走上历史舞台。3DS MAX作为目前流行的三维动画制作软件被广泛使用在实际制作海面动画场景的过程中,人工手动调节该类动画场景工作量非常大,为了解决该问题,本文应用3DS MAX软件内置脚本语言(MAXScript)编写程序,结合3DS MAX内部波纹扭曲体函数来生成具有随机性海浪的海面并通过设置参数来制作海面动画。本文的开发结果直接应用在实际的动漫项目制作中,节省了场景制作的时间,而且系统设定的界面便于用户调用软件内部功能,为制作提高了效率。     

The Whewell-Mill debate on predictions,from Mill's point of view

John Stuart Mill, in his debate with William Whewell on the nature and logic of induction, is regarded as being the first to dismiss the supposed value of successful predictions as merely psychological. I shall argue that this view of the Whewell-Mill debate on predictions misconstrues Mill’s position and argument. From Mill’s point of view, the controversial point was not the question whether predictions ‘count more’ than ex-post explanations but the alleged assertion by Whewell that the successful predictions of the wave theory of light prove the existence of the ether. Mill argued that, on the one hand, the predictions of the wave theory of light do not and cannot provide evidence for the existence of the ether; as evidence for the laws of the theory, on the other hand, the predictions are superfluous, the laws being already well-confirmed. Mill actually endorsed a requirement of independent support closely resembling Whewell’s requirements for hypotheses; the controversy on the value of predictions is a product of the 20th century.     

Revisions of time varying seasonal filters

The main purpose of this study is to analyse the magnitude and the nature of the revisions that the time varying seasonal filters of the X-II and X-II-ARIMA methods introduce in the current seasonally adjusted series The total revision is measured by the mean absolute difference of the transfer functions corresponding to the forecasting and the concurrent seasonal filters with respect to the central‘final’seasonal filter. To take into consideration the fact that the spectrum of a typical economic time series peaks at the low and seasonal frequencies, the revision measures are calculated for selected frequency intervals associated to the trend-cycle, seasonal variations and the irregular component.     

Mitosenverteilung in der larvalen Rumpfepidermis vonSalamandra maculosa Laur.

Summary In the larval epidermal trunk region ofSalamandra maculosa, the total number of mitoses of both sides is approximately the same. This applies to the differentiated Leydig cells as well as to the rest of the epidermis cells.With respect to the meristic segmentation of the trunk, we find within the single segments a regular rise of the mitotic rate, which alternates from one side to the other.From the total number of mitoses found in the epidermis of the trunk, approximately 40% can be accounted for to the dorsal and 60% to the ventral region of the trunk. The number of cells is the same for both the ventral and dorsal region.     

高原列车车窗压差自平衡装置的研究与设计

高原列车由于经常往返于高原与平原之间,车窗中空玻璃内外的压差频繁变化,导致玻璃表面发生频繁往复的微变形,不但影响车厢的气密性,更降低了车窗及车窗贴膜的使用寿命,徒增了铁路运行成本。现行的高原列车,尚没有理想的装置可对其影响进行有效控制。车窗压差自平衡装置的研制,是针对现行高原列车车窗结构的改进。通过设计气压测控系统,实时监测外界大气压的变化,调整中空玻璃内的气压,从鬲使内外压差达到平衡,补偿车窗玻璃表面的微变形。     

冲击荷载作用下CRTSⅢ型板式轨道-路基系统动力特性研究

应用ABAQUS有限元软件建立CRTSⅢ型板式轨道-路基动力分析模型,计算了在落轴冲击荷载作用下CRTSⅢ型板式轨道-路基系统的动力响应,并将仿真计算结果与试验结果进行了对比,验证了模型的可靠性.在此基础上,研究了扣件刚度、路基基床弹性模量、自密实混凝土弹性模量以及长期服役状态下混凝土弹性模量的降低对轨道-路基系统动力特性的影响规律.结果表明:扣件刚度对各部件振动加速度影响较大,路基基床弹性模量对其影响较小;轨道结构在服役过程中混凝土弹性模量的降低会引起轨道板加速度有较大的增幅,应引起重视.     

On the mechanism of the involvement of endothelium in reactive hyperemia

Experiments on anesthetized dogs and on vascular test-preparations demonstrated that reactive hyperemia (RH) was accompanied by the appearance of vasodilator in the blood, and that the level increased with the duration of occlusion of the artery. Removal of the endothelium of the part of the vascular bed studied using saponin, decreased the RH and relaxation of a test-preparation. A rise of pressure in the vascular bed, and a decrease in the deformability of the endothelium resulting from pretreatment with dimerized glutaraldehyde, affected both the hyperemia and the reaction of the vascular preparation in a similar way. It was concluded that the RH resulted from the secretion of vasoactive substances by the endothelium in response to a fall in intravascular pressure.     

西部大开发过程中存在的若干问题及其对策研究

实施西部大开发战略，加快西部发展，逐步缩小各地区之间的发展差距，实现区域经济协调发展，最终达到各地区经济普遍繁荣和全体人民共同富裕，既是社会主义本质特征要求，亦是国民经济持续协调发展的内在需要。近年来，虽然西部大开发已经取得了举世瞩目的成就，但仍然存在着许多问题。本文针对存在的若干问题进行了深入的揭露与研讨，同时提出了若干有益的对策建议。     

隧道围岩施工监测及位移动态模拟分析

为了研究不同支护结构参数和不同开挖方法对围岩位移的影响,以百勺洋隧道为研究对象,通过现场实测、回归分析和数值模拟的技术手段,以大型非线性有限元软件ADINA为研究工具,建立有限元模型。通过改变锚杆支护相关参数和开挖方法,进行大量模拟运算。运算结果表明,随着锚杆长度的增加,地表点下沉量不断减小,隧道的底鼓幅度也逐渐减小,边墙的收敛量也逐渐减小;随着锚杆间距的增加,顶端最大下沉点的竖直方向沉降值增大,边墙收敛值也增大;开挖方法不同时,随着开挖步数的减少,地表下沉值增加,隧道底鼓现象也越明显。开挖步数越多,洞周收敛值越小。     

基于交叉效率Malmquist指数的我国家电上市企业TFP分析

针对基于传统DEA模型的Malmquist指数存在不够客观和精确的缺陷，提出基于交叉效率模型的Malmquist指数。利用该指数对我国家电上市企业在2005～2009年期间的生产效率进行分析，结果表明，家电行业总体的生产效率在稳步提升，但在2008年受到了金融危机的负面影响；规模越小的企业，技术进步给其带来的影响越积极，而中间规模企业生产效率的提高则同时来自技术效率和技术进步。     

信息系统功能增强的多活性代理方法研究

本文在现有多活性代理复杂信息系统理论及其方法的研究基础上,进一步阐述了多活性代理理论体系的基本概念、活性代理的内涵;提出了活性度的概念、特性以及表征;基于活性度的研究,讨论了通过代理活性保持、协商协调增强信息系统的活性方法.首先,从组成复杂信息系统的集合、空间等概念出发,明确了多活性代理复杂信息系统理论体系所涉及的基本概念,以及这些基本概念之间的关系;其次,根据复杂信息系统功能层次上特点与活性自组织机理,提出了代理活性度的概念,并详细探讨了代理活性度的特性、表征及应用实例;同时,从活性的丧失、感知、调整以及判断决策等几个方面给出了多活性代理复杂信息系统活性保持策略;最后,本文详细探讨了多活性代理功能保持的协商协调机理、方法.上述研究成果进一步完善了多活性代理理论体系,并初步给出了代理活性和系统活性的定量表征表示方法,为进一步开展多活性代理复杂信息系统的理论和应用研究奠定了基础.     

非对称双向中继X网络中基于最大化和速率的干扰对齐与中继处理算法

双向中继X网络相对于传统无线通信网络可以实现更高的自由度.然而,基于迫零算法的中继处理算法仅考虑了消除干扰成分,忽略了对期望信号的影响,从而使得网络的和速率有待提高.特别地,当用户发送功率越低,其和速率劣势越明显.针对上述问题研究其干扰对齐方案,并给出了优化的联合考虑期望信号和干扰信号的中继处理算法.首先,通过利用用户矢量信号之间的空间关系,给出网络和速率的数学模型;其次,通过矩阵分析及数值分析理论将最大化网络和速率的中继预编码设计问题转化为线性搜索最优值问题,并用极限值方法近似网络目标函数;再次,进一步将双向网络的目标函数近似为单向网络用户参数的线性组合,大大降低算法复杂度;最后,基于优化的线性搜索最优值问题,得到最大化网络和速率的中继预编码矩阵.仿真结果表明:相较于现有的中继处理方案,本文方案明显改善了网络和速率,同时还简化了最大化网络和速率带来的算法复杂度.     

Pre- and post-natal ontogeny of neutral endopeptidase 24-11 ('enkephalinase') studied by in vitro autoradiography in the rat.

Neutral endopeptidase (NEP, enkephalinase, CALLA) which is present in various neural and non-neural tissues, is able to cleave a variety of regulatory peptides. The distribution of NEP has been studied during rat pre- and post-natal development by autoradiography after in vitro binding of the tritiated inhibitor [3H]HACBO-Gly to whole-body and organ sections. In the central nervous system (CNS), where the presence of NEP has been related to the termination of the action of enkephalins, the external layer of the olfactory bulbs is the only structure prominently labeled before birth. Other CNS structures rich in NEP in the adult, such as the nigrostriatal tract, are progressively labeled after birth. Outside the CNS, the progressive appearance of NEP in the kidney, the lungs and the salivary glands suggests its concomitant involvement in adult physiological functions, including fluid balance control, possibly by cleaving the atrial natriuretic peptide (ANP) and other peptides. On the other hand, transient or enhanced expression of NEP is observed during the development of several organs such as the sensory organs, the heart and the major blood vessels, the intestine, the bones and the genital tubercle. In addition to the still incompletely known physiological functions of the enzyme, the developmental pattern of its expression in several tissues strongly suggests a modulatory role for NEP in the ontogeny of a large number of organs.     

大型直线振动筛横梁结构动力学分析

针对某大型直线振动筛频繁出现横梁断裂问题,应用ANSYS软件,对横梁结构进行了模态分析和谐响应分析,指出结构设计中存在问题。提出横梁结构改进方案,对改进后结构动力学性能进行分析,并与原设计横梁结构的动力学性能进行比较。结果表明：横梁断裂属于低应力断裂;横梁结构静力分析与动力分析的应力值差异较大,采用静力准则的结构设计不能保证结构可靠性;改进后的横梁结构应力状态得到改善,疲劳寿命提高。