考虑桥载设备使用的机场和航空公司运行成本研究

分析了桥载设备在机场和航空公司推广所面临的问题和原因,从航空公司运行的角度讨论桥载设备的使用能否有效地节约航空公司运行成本,分析了不同机型使用桥载设备的成本优化率;然后从机场运行的角度构建了桥载设备静态投资回收周期计算模型,重点讨论了桥载设备套数和使用时间对其静态投资回收周期的影响.实践表明,使用桥载设备代替APU可实现机场、航空公司、旅客三赢:机场可收取桥载设备使用费增加收入,能在较短的时间内回收桥载设备的投资成本;航空公司可有效地节省燃油和APU维修等运行费用;使用桥载设备后可减少碳氮气体排放和噪声污染,改善旅客的航空体验.研究结果能够增强机场和航空公司使用桥载设备的信心和决心,能有效地推动民航节能减排政策在机场的实施.     

线性主动结构及模态(Ⅱ)——离散系统及梁

在“线性主动结构及模态(Ⅰ)”中给出了主动结构的基本概念及模态的若干属性的基础上,对主动离散系统及主动梁的属性做了进一步的讨论,包括稳定性和正交性,并用具体实例对模态做了解释．将伴随结构概念在梁结构中推广,具体讨论了两种配置的主动梁,它们分别代表离散传感和作动及分布传感和作动的配置,并给出了用主动梁振型和伴随主动梁振型表示的正交性条件．用实例给出了同位和非同位主动刚度梁的特征值随反馈大小的变化．     

用数学规划的方法优化跳台滑雪的起跳动作

本文以风洞实验、高速摄影和测力实验得到的有限的、离散的数据为依据,采用多刚体系统动力学理论和数学规划的方法,对跳台滑雪(以下简称跳雪)的起跳动作进行分析和优化,提出了跳雪起跳的最优技术动作.文中给出算例,与国内、外有关文献的结果比较,说明本文的计算与优化是合理的.     

资源禀赋视角下政府与企业互动行为演化分析

针对政府与企业资源的异质性,从资源禀赋的视角,对政府与企业互动的不同模式(随机合作型、政策驱动型、技术推动型、协作共赢型)的界定与分析,构建政府与企业互动行为的演化博弈模型,明确政府与企业在不同模式下的互动行为演化路径。研究结果表明:政府与企业不同互动模式存在显著差异,不同类型企业与政府之间的互动对应着某种互动模式;不同互动模式的产生和演化契合政企互动关系的发展历程;协作共赢型互动模式是政府与企业互动行为演化的高级阶段,有利于政府与企业形成紧密的合作,激发政府政策资源与企业技术资源的协同效应。     

基于零售商过度自信的存货质押博弈决策模型

存货质押是中小企业短期融资的有效手段,而企业对需求的过度自信会影响融资企业和银行的决策,从而影响到企业和银行的预期收益。针对过度自信环境下的存货质押决策问题,建立过度自信零售商和银行的存货质押博弈决策模型,采用Stackelberg博弈分析期望需求和需求波动性两方面过度自信对零售商销售努力、订货量和银行质押率的影响。研究表明:过度自信零售商融资更为激进,过度自信程度越高,对资金需求越大,投入销售努力越高,采购量越大,预期利润与实际利润之间的偏差越大;在低利润市场环境下,质押率随着过度自信的增加而降低,在高利润市场环境下,质押率会随着预测精度过度自信的增加而增加,随着期望需求过度自信的增加而下降。     

Mechanism of the increase in strength and heat resistance of oriented polymeric materials modified by graft copolymerization with vinyl monomers

The mechanical properties and structures of oriented films and fibers composed of polyethylene, polymethyl methacrylate, and other amorphous and crystalline polymers modified by the synthesis of uniformly distributed graft and block copolymers of methyl methacrylate, acrylonitrile, vinylidene chloride and other monomers have been the subject of a comparative investigation. The effect of the grafted polymers on the molecular mobility, relaxation processes, and solubility of the materials is explained by reference to a universal physical "crosslinking" mechanism. A theory of the interrelation between the structure and physical properties of the materials, the nature of the polymers, and the grafting conditions is developed and used to analyze the experimental data on a broad range of systems.V. I. Lenin Belorussian State University, Minsk. Translated from Mekhanika Polimerov, No. 6, pp. 968–975, November–December, 1973.     

变截面二维功能梯度微梁的振动和屈曲特性北大核心CSCD

基于修正的偶应力理论和Timoshenko梁理论,应用变分原理建立了变截面二维功能梯度微梁的自由振动和屈曲力学模型.模型中包含金属组分和陶瓷组分的材料内禀特征尺度参数,可以预测微梁力学行为的尺度效应.采用Ritz法给出了任意边界条件下微梁振动频率和临界屈曲载荷的数值解.数值算例表明:微梁厚度减小时,无量纲一阶频率和无量纲临界屈曲载荷增大,尺度效应增强.锥度比对微梁一阶频率的影响与边界条件密切相关,同时,对应厚度和对应宽度锥度比的影响也有明显差异.变截面微尺度梁无量纲一阶频率随着陶瓷和金属的材料内禀特征尺度参数比的增加而增大,且不同边界条件时增大程度不同.厚度方向和轴向功能梯度指数对微梁的一阶频率和屈曲载荷也有显著的影响.     

Shape design sensitivity of a membrane

The dependence of the static response and the eigenvalues of a membrane on its shape is characterized. A transformation function is defined to determine the shape of the membrane. Differential operator properties and transformation techniques of integral calculus are employed to show that the static response and the eigenvalues of the system depend in a continuous and differentiable way on the shape of the membrane. Explicit and computable formulas are presented for the derivative (first variation) of the structural response and the eigenvalues with respect to the shape. A rigorous proof is provided, and the shape design sensitivity of a typical integral functional is determined.The author is indebted to Professor E. J. Haug for his comments and stimulating interest in the paper.     

Physical entropy, information entropy and their evolution equations

Inspired by the evolution equation of nonequilibrium statistical physics entropy and the concise statistical formula of the entropy production rate, we develop a theory of the dynamic information entropy and build a nonlinear evolution equation of the information entropy density changing in time and state variable space. Its mathematical form and physical meaning are similar to the evolution equation of the physical entropy: The time rate of change of information entropy density originates together from drift, diffusion and production. The concise statistical formula of information entropy production rate is similar to that of physical entropy also. Furthermore, we study the similarity and difference between physical entropy and information entropy and the possible unification of the two statistical entropies, and discuss the relationship among the principle of entropy increase, the principle of equilibrium maximum entropy and the principle of maximum information entropy as well as the connection between them and the entropy evolution equation.     

Periodic solutions and bifurcations in an impact inverted pendulum under impulsive excitation

A class of periodic motions of an inverted pendulum with rigid lateral barriers is analysed under the hypothesis that the system is forced by impulsed periodic excitation. Due to the piece-wise linear nature of the problem, the existence and the stability of the cycles are determined analytically. It is found that they depend on both classical (saddle-node and period-doubling) and non-classical bifurcations, the latter involving a ‘synchronization' between impulses and impacts which leads to the sudden disappearing of the orbits. Attention is paid to the physical interpretation of these bifurcations, and to the determination of analytical criteria for their occurrence. We study how the relative position (with respect to the excitation amplitude) of the local bifurcations determines the system response and the bifurcation scenario. Symmetric and unsymmetric excitations are considered and the regions of stability of the periodic solutions are analytically determined. Finally, a comparison with the case of harmonic excitation is presented showing both analogies and differences, and highlighting how the impulsed excitation allows to obtain stable periodic responses at higher values of the excitation amplitude.     

基于信用额度和外生违约概率的出口海陆仓融资质押率优化

质押率优化是出口海陆仓融资决策的核心内容。针对出口商信用、出口商与进口商外生违约以及质押物价值波动三重叠加风险下的出口海陆仓融资决策问题,在设定出口商信用额度,且给定出口商和进口商外生违约概率的前提下,依据双重Stackelberg博弈原理,以供应链协同均衡下的出口商、进口商和船公司的期望利润最大化为目标,建立了质押率与订货量及货物价格联动优化模型,设计了微分法和逆向归纳法求解模型。算例验证了模型和方法的适用性和有效性。敏感性分析结果表明质押率与出口商信用额度呈负相关关系,对出口商和进口商外生违约概率不敏感。研究结论可为出口海陆仓融资优化决策提供科学参考。     

Two-boundary problems for a Poisson process with exponentially distributed component

For a Poisson process with exponentially distributed negative component, we obtain integral transforms of the joint distribution of the time of the first exit from an interval and the value of the jump over the boundary at exit time and the joint distribution of the time of the first hit of the interval and the value of the process at this time. On the exponentially distributed time interval, we obtain distributions of the total sojourn time of the process in the interval, the joint distribution of the supremum, infimum, and value of the process, the joint distribution of the number of upward and downward crossings of the interval, and generators of the joint distribution of the number of hits of the interval and the number of jumps over the interval. __________ Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 58, No. 7, pp. 922–953, July, 2006.     

Propagation of weak perturbations in cracked porous media

A three-velocity, three-pressure mathematical model is proposed which enables one to study wave processes in the case of a double porosity, deformable, fluid-saturated medium. This model takes account of the differences in the velocities and pressures in pore systems of different characteristic scales of the pores, fluid exchange between these pore systems and the unsteady forces due to interphase interactions. It is established that a single transverse and three longitudinal waves: one deformation wave and two filtration waves, propagate in such a medium. The existence of two filtration waves is associated with the two different characteristic scales of the pores and the difference in the velocities and pressures of the fluid in these pore systems. The filtration waves decay considerably more rapidly than the deformation and transverse waves. The velocities of the deformation and transverse waves are mainly determined by the elastic moduli of the skeleton. The velocity and decay of the first filtration wave depend strongly on the intensity of the interphase interaction force while the velocity of the second filtration wave depends strongly on the rate of mass exchange between the pores and the cracks. The rate of decay of the second filtration wave is significantly higher than that of the first filtration wave.     

基于演化博弈论的环卫自律组织激励机制研究

我国部分城市开始推进市容环境卫生责任区制度,并探索建立环卫自律组织。本文将自律组织和组织成员作为博弈双方建立演化博弈模型,并引入激励机制;然后计算博弈双方在不同收益下的选择意愿,进行稳定性分析;最后运用MATLAB仿真分析参数变化对演化结果和路径的影响。结果表明,合理的激励机制大大提高了组织成员的积极性,并将激励机制设置为正激励与负激励,其中正激励包括荣誉激励、资金激励两者并行激励。同时,上级政府部门需加强对自律组织的监管,大力宣传环卫自律自治,提高组织成员的自律自治意识,使环卫自律组织的管理运行更加顺畅。     

基于故障树和混沌粒子群算法的锻压机床故障诊断方法

锻压机床由于生产效率高和材料利用率高的特点,被广泛应用于各领域.然而,锻压机床发生故障时,其故障种类繁多、故障数据量大,所以对锻压机床故障源的快速、准确诊断较困难.针对该问题,文章提出一种将故障树分析法和混沌粒子群算法相融合的方法,对锻压机床的故障源进行故障诊断.该方法是先通过故障树分析法对锻压机床的故障进行分析从而得到故障模式及其故障概率,然后由得到的故障模式和已知的故障维修经验分析归纳出故障模式的学习样本,再根据得到的故障概率运用混沌粒子群算法的遍历性快速、准确地诊断出锻压机床发生故障的精确位置.文章提出的方法以锻压机床的伺服系统为例进行了故障诊断实验,将该实验结果与遗传算法、粒子群算法进行对比.实验结果表明,文章的算法在锻压机床伺服系统的故障诊断中准确度更高、速度更快.     

The Arab Spring: A simple compartmental model for the dynamics of a revolution

We introduce a simple compartmental model for the dynamics of a revolution in dictatorial regimes that employ censorship and police repression. A defining property of the model is the use of visibility and policing terms that feature rapid transitions as a function of the size of the revolution, for which we provide conceptual and network-based mathematical justifications. The complete mathematical classification of the dynamical behaviour of the model leads to a division in parameter space that is interpreted naturally in terms of stability of the regime (stable police state, meta-stable police state, unstable police state, and failed state). We show that these dynamical properties of the model are generic for a broad class of visibility and policing functions that feature rapid transitions. We investigate how the model can be applied to the peaceful revolutions of the Arab Spring in Tunisia and Egypt, taking into account the influence of the Internet and new media on the visibility of the revolution and the ensuing reduced effectivity of censorship. Within the model this leads to significant, discontinuous changes in regime stability, which greatly increase the probability of realized revolutions. These properties of the model inform possible answers to questions on causes and timing of the Arab Spring revolutions, and the role of the Internet and new media. The broader relevance of the model classification is also investigated by applying it to the current political situation in some other countries with regimes that employ censorship and police repression.     

车站咽喉通过能力可视化计算集成系统的研究

在对国内外咽喉道岔通过能力计算方法比较与分析基础上 ,论文提出了车站咽喉通过能力可视化计算集成系统的系统结构和功能设计 ,应用图论和网络优化技术对车站咽喉布置、咽喉及车站作业过程进行抽象建模 ,建立了咽喉作业占用安排网络优化和咽喉作业能力的复合递阶决策模型 .该研究综合运用上述模型、算法、计算机信息处理技术和图形技术 ,可视化模拟咽喉作业情况 ,实现了核心基础数据计算机模拟采集、作业优化安排和最大可实现能力的查定及优化 ,并将结果以图形方式输出 .通过实例验证表明 ,计算结果合理可信 ,可用于车站咽喉能力的评价检验 .     

Mathematical modeling of industrial aluminum electrolysis

The problem of aluminum electrolysis is discussed. The mathematical model of an industrial electrolyzer presented in the paper is written under the assumption that the electrolyte and metal media are immiscible. At the basis of the mathematical statement is a three-dimensional, nonstationary, and nonlinear system of magnetic hydrodynamics equations which is written separately in the aluminum medium and in the electrolyte medium with a geometric account for wall accretion, skull, and arrangement of anodes. The proposed system allows one to model various forms of anodes, the number of anodes in a bath, and their sizes. Interfaces of media are connected by a viscous friction. Initial values of speeds and electromagnetic fields in the media and the medium interface are considered as set. On the skull, bottom, and anodes the attachment conditions are set. The speed of change of a magnetic field in the metal and electrolyte on the interface is considered zero. On the basis of a numerical method of solution of the system of equations, there is a well-proved method of division over physical processes. The analysis of results of the numerical experiment has shown that it is actually possible to allocate a ??middle?? layer for modeling of the electrolysis process. The proposed model allows one to investigate media behavior upon the occurrence of a long anode effect due to sharp reduction of the electric conductivity of the electrolyte and subsequent sharp growth of the electric-field strength.     

Analyzing connections between teacher and student topic-specific knowledge of lower secondary mathematics

The interpretive cross-case study focused on the examination of connections between teacher and student topic-specific knowledge of lower secondary mathematics. Two teachers were selected for the study using non-probability purposive sampling technique. Teachers completed the Teacher Content Knowledge Survey before teaching a topic on the division of fractions. The survey consisted of multiple-choice items measuring teachers’ knowledge of facts and procedures, knowledge of concepts and connections, and knowledge of models and generalizations. Teachers were also interviewed on the topic of fraction division using questions addressing their content and pedagogical content knowledge. After teaching the topic on the division of fractions, two groups of 6th-grade students of the participating teachers were tested using similar items measuring students’ topic-specific knowledge at the level of procedures, concepts, and generalizations. The cross-case examination using meaning coding and linguistic analysis revealed topic-specific connections between teacher and student knowledge of fraction division. Results of the study suggest that students’ knowledge could be associated with the teacher knowledge in the context of topic-specific teaching and learning of mathematics at the lower secondary school.     

基于韧性度的低轨卫星通信网络抗毁性度量及优化

低轨卫星通信网络的抗毁性是描述网络安全可靠的有效工具,在网络体系结构设计和路由策略等领域得到了广泛的应用。根据低轨卫星通信网络中卫星在轨道平面内移动,需要不断进行切换的特点,从建立抗毁性测度模型以及网络抗毁性优化两个角度来评估和提高网络抗毁性,提出一种基于韧性度的低轨卫星通信网络抗毁性度量方法。通过对移动模型以及切换模型的结构分析,对每种结构以一定概率出现的低轨卫星通信网络,应用韧性度函数,求得网络在某个时刻及某一段时间段内的抗毁性,并针对切换模型的不足之处进行优化,用赋权韧性度来体现优化的效果,得到了优化后的网络抗毁性。以铱星系统为应用实例进行仿真,结果表明:任意时刻网络的抗毁性跟拓扑结构的韧性度值有关,并且是一种线性关系,即随着韧性度的增加,其抗毁性也增加。通过对铱星通信系统切换模型的优化,网络的抗毁性与平均抗毁性都得到了提升,说明本文所构建模型的有效性和实用性。