Efficient molecular model for squeeze-film damping in rarefied air

Based on the energy transfer model(ETM) proposed by Bao et al.and the Monte Carlo(MC) model proposed by Hutcherson and Ye, this paper proposes an efficient molecular model(MC-S) for squeeze-film damping(SQFD) in rarefied air by releasing the assumption of constant molecular velocity in the gap.Compared with the experiment data, the MC-S model is more efficient than the MC model and more accurate than ETM.Besides, by using the MC-S model, the feasibility of the empirical model proposed by Sumali for SQFD of different plate sizes is discussed.It is proved that, for various plate sizes, the accuracy of the empirical model is relatively high.At last, the SQFD of various vibration frequencies is discussed, and it shows that, for low vibration frequency, the MC-S model is reduced to ETM.     

导弹平台测试系统设计方法研究

运用建模的技术对导弹平台测试系统进行模型设计过程中,关键是实现测试系统需求描述模型、结构模型和行为模型等的设计;首先对导弹平台测试系统的工作流程进行了分析,然后在此基础上利用UML建模方法进行测试系统的各项模型设计,通过分解用例图说明测试系统的需求描述模型,分析系统的结构体系及关联关系建立了测试系统的结构模型,运用序列图建立了测试系统的行为描述模型;最后,根据上述模型设计提出了系统的结构及布置关系的设计方案,并且在实际导弹平台测试系统开发中得到了应用,实现了测试系统的各项测试功能;结果表明,采用该建模方法不但能够有效提高系统设计的效率,而且系统在实用性的基础上,还具有复用性及拓展性。     

考虑碳粒表面还原反应的移动火焰锋面(MFF)模型

在原始移动火焰锋面(MFF)模型的基础上,提出一种考虑碳粒表面还原反应的改进MFF模型。该模型给出了包括表面还原反应和 CO容积反应在内的碳粒燃烧反应速率的显式表达式,便于分析和讨论各种工况下碳粒的燃烧状态和影响因素。与原始的 MFF模型和单膜模型相比,所计算的颗粒温度和燃烧速率更符合严格的连续膜模型的预报结果,而计算时间只为连续膜模型的数十万分之一。研究结果表明,改进的 MFF模型是一种简单可行、适于工程应用的碳粒燃烧理论模型。     

混合对流的数值模拟

分别采用(-v'2)-f模型、k-ε模型和室内零方程模型对通风空调中典型的气流组织形式混合对流进行数值模拟.研究表明:在通风入口附近存在一个分离涡,对这个分离涡预测的准确程度是整个计算成败的关键因素.将预测结果和实验进行比较,发现这个涡的尺度介于(-v'2)-f模型和零方程模型预测的结果之间,比k-ε模型预测的结果大.虽然从流场上看,零方程模型预测的结果和实验结果吻合很好,但从模型构造的角度看,它不具备普遍的意义.从对温度场的预测看,(-v'2)-f模型预测结果最好,室内零方程模型次之,k-ε模型结果最差.     

基于拓展分离变量法的非傅里叶传热研究

常规的分离变量方法不能求解非傅里叶传热模型问题,本文对常规分离变量法进行拓展,利用拓展后的方法求解热传导的傅里叶模型,单相位滞后（C-V）模型和双相位滞后（DPL）模型,比较利用三种模型计算温度场的差别.研究C-V模型和DPL模型中温度波动的规律,得到温度波动速度和热流量时间滞后值的关系.     

An exactly solvable model for the large polaron

We present an exactly diagonalizable model Hamiltonian for the large polaron derived by analyzing the variational ansatz by Haga-Larsen (HL) for the Fröhlich Hamiltonian. The lowest energy eigenvalue of the model Hamiltonian for fixed wave numbers reproduces the energy of the variational ansatz by Haga-Larsen and is, therefore, an upper bound with respect to the corresponding energy eigenvalue of the Fröhlich Hamiltonian. This is valid for any momentum which is proven by extending the Haga-Larsen approach. Furthermore, since all integrations can be performed analytically, the model Hamiltonian is easily tractable. The energy eigenvalue spectrum of the model Hamiltonian is studied below and above the phonon-emission threshold. The quality of the model Hamiltonian is determined by the variational ansatz of Haga and Larsen. Incorporating an improved energy-momentum relation, a generalized model Hamiltonian is derived possessing a larger validity range with respect to the coupling strength. Furthermore, a second exactly diagonalizable model Hamiltonian based on improved Wigner-Brillouin perturbation theory due to Warmenbol, Peeters, and Devreese (WPD) is presented. It is briefly demonstrated that one is able to construct all mentioned model Hamiltonians also in the 2D polaron problem. In contrast to the 3D case, where the HL-type model Hamiltonian possesses the higher quality for any momentum, in the 2D case, it works well only for small momenta. For large momenta, only the WPD-type model Hamiltonian describes the energy-momentum relation correctly. We demonstrate the usefulness of the model Hamiltonian concept by exactly calculating the one-electron Green’s function for all mentioned model Hamiltonians and comment why significant advantages of the model Hamilton concept for the treating of low-dimensional systems (planar semiconducting quantum-well structures) can be expected.     

用于脉冲等离子体推力器烧蚀过程仿真的新型机电模型

用于脉冲等离子体推力器(PPT)工作过程仿真的一维机电模型, 具有模型简单、计算周期短等优点, 在PPT设计过程中得到了广泛应用. 本文针对机电模型假设工质烧蚀质量为常数和不考虑烧蚀过程这一局限, 提出了一种采用Teflon一维烧蚀模型计算工质烧蚀质量的改进模型, 并以LES-6 PPT为研究对象进行了仿真. 通过与LES-6 PPT实验数据进行对比, 仿真结果与实验数据符合, 充分验证了模型的可靠性. 此模型能够对Teflon工质在PPT工作过程中的温度变化和烧蚀过程进行仿真, 弥补了机电模型忽略烧蚀过程对仿真结果所造成的影响, 同时, 此模型依然保持了机电模型简单易于实现的优点, 对于脉冲等离子体推力器的设计具有重要意义. 关键词： 脉冲等离子体推力器 机电模型 烧蚀模型 数值仿真     

热损耗条件下导热系数反演模型及实验研究

通过导热反问题反演求解导热系数通常误差较大,本文构建考虑热损耗条件下的虚拟薄板模型精确求解导热系数。首先通过数值算例验证模型的准确性和稳定性,正向问题使用有限差分法进行求解,反问题求解采用人工蜂群算法进行目标函数最优化。然后搭建第二类边界条件下导热正向装置,进行导热系数实例反演和实验研究,并将新模型与理论模型反演结果对比分析。结果表明理论模型反演结果的相对误差约为-14.76%,而新模型下导热系数反演相对误差达到-4.67%。新模型较理论模型反演结果更精确,有效降低了热损耗对反演的影响,提高了反演精度,更符合实际工况。     

一种推广伊辛自旋模型的实空间重正化群理论

本文提出了一种推广的伊辛自旋模型。它包括了伊辛自旋模型、Schofield和Bowers提出的混合自旋模型以及一种特殊的格点稀释伊辛自旋模型作为特例。运用实空间重正化群得到了这个推广模型的相变流图和三个非平庸不动点(一个伊辛不动点,一个三相不动点和一个一级相变不动点)。结果表明:混合自旋模型和伊辛模型属于同一普适类。证实了Schofield和Bowers通过直接对混合自旋模型临界指数的计算所做的结论。 关键词：     

On the algebraic formulation of collective models. I. The mass quadrupole collective model

This paper is the first in a series of three which together present a microscopic formulation of the Bohr-Mottelson (BM) collective model of the nucleus. In this article the mass quadrupole collective (MQC) model is defined and shown to be a generalization of the BM model. The MQC model eliminates the small oscillation assumption of BM and also yields the rotational and CM(3) submodels by holonomic constraints on the MQC configuration space. In addition, the MQC model is demonstrated to be an algebraic model, so that the state space of the MQC model carries an irrep of a Lie algebra of microscopic observables, the MQC algebra. An infinite class of new collective models is then given by the various inequivalent irreps of this algebra. A microscopic embedding of the BM model is achieved by decomposing the representation of the MQC algebra on many-particle state space into its irreducible components. In the second paper this decomposition is studied in detail. The third paper presents the symplectic model, which provides the realization of the collective model in the harmonic oscillator shell model.     

一种新的航天器外露介质充电模型

为综合考虑高能电子辐射与周围等离子体对航天器外露介质充电的影响,在航天器内带电模型的基础上,通过添加边界充电电流来考虑等离子体与航天器介质表面的相互作用,并统一参考电位为等离子体零电位,建立了航天器外露介质充电模型,给出了新模型的一维稳态解法,并与表面充电模型和深层充电模型进行了对比分析.结果表明:新建模型能够综合考虑表面入射电流、深层沉积电流和传导电流对充电的耦合作用过程,实现外露介质表面和深层耦合充电计算,有利于全面评估航天器外露介质的充电问题.     

The Odd Eight-Vertex Model

We consider a vertex model on the simple-quartic lattice defined by line graphs on the lattice for which there is always an odd number of lines incident at a vertex. This is the odd 8-vertex model which has eight possible vertex configurations. We establish that the odd 8-vertex model is equivalent to a staggered8-vertex model. Using this equivalence we deduce the solution of the odd8-vertex model when the weights satisfy a free-fermion condition. It is found that the free-fermion model exhibits no phase transitions in the regime of positive vertex weights. We also establish the complete equivalence of the free-fermion odd 8-vertex model with the free-fermion 8-vertex model solved by Fan and Wu. Our analysis leads to several Ising model representations of thefree-fermion model with pure 2-spin interactions.     

Changing spectrum estimation

An autoregressive (AR) model with time varying coefficients is used for the modeling of non-stationary covariance time series. A stochastically perturbed linear constraint model is presented as a model of time varying AR coefficients. The overall model for the time series is fitted by using the Kalman filter and Akaike's AIC criterion. An estimate of a changing spectrum is obtained by the fitted model and the fixed interval smoother Examples are given to illustrate the procedure.     

交通流双车跟驰模型与数值仿真

基于全速度差(FVD)模型,考虑双前车信息的影响,提出了交通流双车跟驰模型.通过线性稳定性分析,得到了改进模型的稳定性条件. 与FVD模型对比研究表明,改进模型的稳定区域有明显增加.数值模拟结果表明,改进模型通过调节次近邻前车信息,可以避免FVD模型中因为反应系数较小时出现负速度的缺陷.同时也表明次近邻前车对交通流存在不可忽视的影响. 关键词： 交通流 双车跟驰模型 模拟     

Semirealistic models of the cochlea

The aim of this paper is the introduction and comparison of consistent albeit passive mechanical models for the whole cochlea. A widely used transmission line filterbank, which hydrodynamically speaking is a long wave approximation (L model), suffers from a well-known inconsistency: its main modeling assumption is not valid within the resonance region, where most of the overall excitation takes place. In the present paper two approaches to overcome this inconsistency are discussed. One model is the average pressure (AP) model by Duifhuis, the other is obtained by a combination of a long and a short wave approximation (LS model). Considerable differences between the L and the LS model are observed. All models are compared by inserting them into the full integral equation obtained from the hydrodynamic equations and the boundary conditions. Here the LS model fares better than the AP model for small damping, whereas the opposite is true for higher damping. As expected, the L model fails badly in the resonance region.     

Effect of restart at signals on traffic flow through a series of signals

We study the effect of restart at signals on the vehicular traffic controlled by a series of signals. The Nagel–Schreckenberg model (NS model) and Fukui–Ishibashi model (FI model) are applied to the vehicular motion. In the FI model, the step-by-step acceleration is not taken into account but the acceleration effect is included in the NS model. It is shown that the difference between both models results in the restart effect at signals. The extended version of the NS model with signals is formulated by the difference equation. The restart at signals has an effective effect on the traffic flow. The fundamental diagram changes highly by the restart effect. The dependences of mean speed on the cycle time are shown.     

初始模型对含噪动态光散射数据正则化反演结果的影响

分别采用最小模型矩阵、最平坦模型矩阵、最光滑模型矩阵作为初始化模型,对加入5种不同水平随机噪声的90 nm窄单峰、90 nm宽单峰和250 nm窄单峰、250 nm宽单峰颗粒体系的模拟分布进行了正则化反演,并对反演结果进行比较。结果表明：当噪声水平为0时,正则化初始模型的选择对反演结果没有明显影响。随着噪声水平的增加,采用三种初始化模型反演得到的峰值误差和粒度分布误差都随之变大,但采用最平坦模型和最光滑模型反演得到的峰值和粒度分布误差明显小于采用最小初始模型的反演误差。当噪声水平大于0.01时,选择最平坦初始模型获得的粒度分布结果优于采用最光滑初始模型和最小初始模型获得的结果,而采用最光滑初始模型反演得到的峰值优于最平坦初始模型和最小初始模型的反演峰值。因此,采用正则化算法处理含噪动态光散射数据时,为得到最优的粒度分布信息,宜采用最平坦初始模型,若需要获取最准确的峰值信息,则应选择最光滑初始模型。     

Modulation equations for slug flow in vertical pipes

A gas?liquid flow in a long vertical pipe is considered. A new mathematical model of the flow generalizing the known drift-flux model is constructed. The gas velocity and the average flow velocity in this model are connected by the Zuber?Findlay relation. The model is obtained by averaging the quasi-periodic slug flow regime. Contrary to the drift-flux model, it is possible to restore the internal structure of the flow and, in particular, to give the criterion of transition to the new regime.     

Brightness Temperature Emitted by Radiometer Calibration Load at Millimeter Wave Band

In this paper, the DVRT (vector radiative transfer theory of densely distributed random discrete scatters) model to calculate the brightness temperature emitted by radiometer calibration load is presented. It takes the multiple scattering of isolation layer into account, which is neglected by the incoherent homogeneous model often used in calibration. Hence, it works much better than incoherent homogeneous model at millimeter wave band. Furthermore, the iteration of DVRT model is presented, and it proves that the incoherent homogeneous model is just the zero-order solution of DVRT model. Some numerical results are provided in the end.     

边界层转捩区声辐射的预报方法研究

对Lighthill剪切应力脉动模型和Liepmann位移厚度脉动模型进行了讨论,在此基础上,本文提出利用Krane偶极子声源模型对Liepmann单极子声源模型进行改进。数值计算结果表明:作为偶极子声源的Lighthill理论剪切应力脉动模型,预报的噪声级偏低;而作为单极子声源的Liepmann模型,预报的噪声级又偏高;本文提出的两种改进模型预报的噪声级则与Lauchle实验值的一致性较好。