基于恢复系数的碰撞过程模型分析

论述了恢复系数的含义及作用,并在此基础上介绍了几种碰撞过程模型.通过详细推导恢复系数与模型参数之间的关系,使得不同的碰撞过程模型可统一用恢复系数表示能量损失,并用接触刚度表示变形.这也阐明了碰撞过程模型与刚性模型之间的区别和联系,把动态接触理论和古典碰撞理论统一了起来.通过对一个单球碰撞系统进行数值仿真,不仅验证了关系推导的正确性,而且对各种模型从精度、效率、微观接触过程等方面进行了比较.     

利用DMSM方法求解弹性撞击恢复系数

给出了物体与细长杆或梁弹性碰撞恢复系数的一种求解方法。在研究碰撞问题时,把碰撞物作为靶体的附加质量,从而把碰撞问题转化为常规的振动问题求解．两个撞击物的分离时刻根据撞击力为零得到．结论如下：只考虑弹性碰撞时,恢复系数不仅与靶体的材料性质有关,还与碰撞物体质量比、靶体的支承条件有关,但与碰撞的初始速度无关．     

Delay time compensation based on coefficient of restitution for collision hybrid motion simulator

A hybrid motion simulator embeds a hardware experiment in a numerical simulation loop. However, it is often subjected to the inherent problem of an energy increase in the collision of two pieces of hardware in a loop because of the delay time. This paper proposes a delay time compensation method based on contact dynamics model for a collision hybrid motion simulator under delay time and establishes a compensation method for coupled translational and rotational motion. The model developed in this paper describes linear uniform motion of a floating object during the period of the delay time until the force and torque are observed and non-linear motion according to environmental stiffness after the initial delay time period in contact. By using the above model, compensation parameters are designed based on desired coefficient of restitution with iterative calculation. The proposed method achieves accurate delay time compensation and simultaneously realizes a variable desired coefficient of restitution over a wide range of frequencies. Furthermore, the compensation method for multi-dimensional motion is established under the assumption that the friction effect is very small. The efficiency of the proposed method is verified through collision experiments for the coupled motion in two dimensions.     

Analytical model of variable characteristic of coefficient of restitution and its application to ball trajectory planning

In this article, we investigate the behavior of the coefficient of restitution (COR) which is an important parameter in many impact-related fields. In many cases, the COR is considered as a constant value, but it varies according to many variables. In this paper, we introduce an analytical variable COR model considering aerodynamics along with its verification through experiment. To introduce and analyze the variable characteristic of the COR model, the collision phenomenon between a pendulum and two kinds of ball is employed as an example and aerodynamics such as drag force is considered for analyzing the after-effect of the collision. Collision velocity of the pendulum, dynamic parameters of colliding bodies, contact time, drag coefficient, the air density, and the cross-sectional area of the ball are found as the typical variables of analytical COR model. This observation generalizes the result in previous researches. To verify new COR model, the travel distances for the curve-fitted constant COR model and the curve-fitted variable COR model are compared through simulation and experiment. Moreover, comparison between constant COR and variable COR is presented in several points of view. Finally, using the variable COR model, the travel distance of the ball for given collision velocity can be estimated.     

Compensation for dead band of force measurement based on the coefficient of restitution in a hybrid simulator

In order to develop space robotic technologies, the feasibility and reliability of the systems have to be verified by repetitive operation tests. A hybrid simulator (also referred to as a Hardware-in-the-loop simulator) is one of the effective ways to examine orbital operations on the ground. The simulator embeds a hardware experiment in a numerical simulation loop. However, it is known that the hybrid simulator has a serious problem that energy increase arises in contact with a hardware experiment in the loop. In general, the energy increase in the hybrid simulator occurs due to the dead time in the system. However, this paper presents that dead band in force/torque measuring also causes the energy increase. The dead band in the force/torque measuring is necessary to avoid unexpected motion of the hybrid simulator due to the noise data in the force/torque sensor. This paper proposes two compensation methods for the energy increase problem due to the dead band. The first method is to insert a virtual damper to absorb the increased energy during the contact. The second method is to extrapolate force/torque data that is lost through the dead band processing right after the contact. The experimental verification with uniaxial contact in hybrid simulator is carried out to validate the proposed compensation methods.     

On a statistical damage constitutive model for rock materials

A statistical damage constitutive model for rocks with strain softening behaviour is put forward, using the theory of continuous damage mechanics together with statistical mesoscopic strength theory based on maximum entropy distribution. In statistical constitutive modelling, the probabilistic distribution of mesoscopic element strength in rocks is a critical piece of information, which was conventionally described by various empirical distributions among which the Weibull distribution was extensively used. In this paper, an alternative and universal distribution, i.e. maximum entropy distribution, is proposed to describe the statistical property of mesoscopic strength in rocks. By incorporating the entropy distribution information into a damage variable, the paper derives a new constitutive model, which is verified by conventional triaxial experiments and dynamic experiments on rock specimens. To illustrate suitability and flexibility, the new model is compared to the well-established Weibull-distribution-based models.     

采煤机参数与煤岩硬度关系公式修正系数研究

针对当前煤矿综采工作面采煤机无法自动、准确识别煤岩性状的问题,分析了采煤机截割电动机参数与反映煤岩硬度的普氏系数的关系公式,得出两者近似成比例线性关系;通过实测数据,得到关系公式中修正系数的取值范围;最后通过实际应用验证了根据修正系数推断出的普氏系数与实际情况相符。     

A stickiness coefficient for longitudinal data

In this paper, we introduce the stickiness coefficient, a summary statistic for time-course and longitudinal data, which is designed to characterize the time dynamics of such data. The stickiness coefficient provides a simple, intuitive and informative measure that captures key information contained in time-course data. Under the assumption that the data are generated by the trajectories of a smooth underlying stochastic process, the stickiness coefficient illuminates the relationship between the value of the process at one time with the value it assumes at another time via a single numeric measure. In particular, the stickiness coefficient summarizes the extent to which deviations from the mean trajectory tend to co-vary over time. The estimation scheme we propose will allow for estimation even in the case that the longitudinal data are sparsely observed at irregular times and may be corrupted by noise. We demonstrate an estimation procedure for the stickiness coefficient and establish asymptotic consistency as well as asymptotic convergence rates. We illustrate the resulting stickiness coefficient with some theoretical calculations as well as several economic and health related data examples.     

A two-temperature model of hydrate-bearing rock

A two-temperature model for describing the temperature field of a heat source in a hydrate-bearing rock is proposed. For the water/ice phase, the enthalpy formulation of the Stefan problem is used. Numerical simulation is accomplished through the finite element method.     

A correlation coefficient for intuitionistic fuzzy sets

Intuitionistic fuzzy sets are a generalization of the ordinary fuzzy sets in which we have both a membership function μ and a nonmembership function ν. In this article we consider the problem of defining a correlation coefficient between two intuitionistic fuzzy sets. We show that by interpreting an intuitionistic fuzzy set as an ensemble of ordinary fuzzy sets we are able to derive a simple, intuitively satisfying correlation coefficient between two intuitionistic fuzzy sets. We show the reasonableness of the results obtained by examining several test cases. © 2004 Wiley Periodicals, Inc.     

基于摩擦系数的扩散模型

根据分子间摩擦系数与组分自扩散系数关系,提出一个新的互扩散系数模型。模型分为3部分：组成项、自扩散系数和化学势与组分关系。采用文献自扩散系数值,并用不同状态方程以计算化学势与组分关系,模拟1 132～1 810℃之间不同组成二氧化碳气体混合物的互扩散系数,并与实验值做了比较。结果表明采用Peng-Robinson(PR),Redlich-Kwong(RK)及Van der Waals(VdW)方程计算化学势与组分关系而得到的模拟结果优于Virial方程,且平均误差在5%之内。     

一种重力敏感器阻尼系数测试方法

当重力敏感器内部充满阻尼液时,其表体内弹性系统的阻尼系数由阻尼液粘度和敏感器内部结构共同决定.提出了一种实际测量重力敏感器阻尼系数的测试方法.分析了重力敏感器的阻尼系数和内部结构的关系,给出了敏感器工作原理模型,推导出敏感质量振幅的函数关系式.通过在力矩线圈上施加不同频率、不同幅值的激励源信号并测试敏感质量振幅的方式,绘制出不同阻尼系数下敏感质量的振幅-频率关系曲线,将之与理论函数曲线对照来确定相应的阻尼系数值.试验结果表明:该阻尼系数测试方法能够有效地测试出充满不同粘度阻尼液的重量敏感器的阻尼系数,为阻尼液粘度的选取和控制回路的设计提供参考.     

A modal decomposition of the Hopf normal form coefficient

The local stability of a nonlinear dynamical system at an equilibrium point with a pair of purely imaginary eigenvalues can be assessed through the computation of a cubic Hopf normal form coefficient, assuming the remaining eigenvalues have negative real parts. In this paper, a modal decomposition of the Hopf coefficient is proved. The decomposition provides a new methodology for analyzing the Hopf cubic normal form coefficient in a formal way. The framework is illustrated by nonlinear stability analysis of two control designs where it is shown that the Hopf coefficient can be stabilized through modal nonlinear feedbacks     

一种基于聚集系数的社区发现算法

社区划分一直是复杂网络研究中的一个热门话题,社区的快速准确划分为研究复杂网络的性质提供了良好的基础。传统的社区发现方法都是在全局复杂网络的基础上进行社区划分,随着网络中节点的增加,网络规模的变大,社区发现变得更为复杂。提出了一种局部社区发现算法,该算法无需知道整个复杂网络的全部信息,只需从一个待求节点出发,考察其与邻接节点的紧密程度,逐步将邻接点添加到社区中,得到该节点所在的社区结构。同时,该算法还可实现全局网络的社区发现。利用该算法分别对Zachary空手道俱乐部网络和海豚社会网络进行社区发现,实验结果表明了该算法的准确性与可行性。     

A flexible coefficient smooth transition time series model

We consider a flexible smooth transition autoregressive (STAR) model with multiple regimes and multiple transition variables. This formulation can be interpreted as a time varying linear model where the coefficients are the outputs of a single hidden layer feedforward neural network. This proposal has the major advantage of nesting several nonlinear models, such as, the self-exciting threshold autoregressive (SETAR), the autoregressive neural network (AR-NN), and the logistic STAR models. Furthermore, if the neural network is interpreted as a nonparametric universal approximation to any Borel measurable function, our formulation is directly comparable to the functional coefficient autoregressive (FAR) and the single-index coefficient regression models. A model building procedure is developed based on statistical inference arguments. A Monte Carlo experiment showed that the procedure works in small samples, and its performance improves, as it should, in medium size samples. Several real examples are also addressed.     

A program to calculate a general recoupling coefficient

Title of adaptation: ADAPT TO INTEGER ARITHMETIC Adaptation number: 0002 Reference to original program:Catalogue number: AAGD; Title: NJSYM; Ref. in CPC: 1 (1970) 241 Author of original program: P.G. Burke Computer: ICL 1906A, Installation: Oxford University; Oxford, England; IBM 370/165; C.I.R.C.E., Orsay, France. Operating system: GEORGE 3 No. of cards required to effect adaptation (including directive cards): 176 Card punching code: EBCDIC     

A digital rock density map of New Zealand

Digital geological maps of New Zealand (QMAP) are combined with 9256 samples with rock density measurements from the national rock catalogue PETLAB and supplementary geological sources to generate a first digital density model of New Zealand. This digital density model will be used to compile a new geoid model for New Zealand. The geological map GIS dataset contains 123 unique main rock types spread over more than 1800 mapping units. Through these main rock types, rock densities from measurements in the PETLAB database and other sources have been assigned to geological mapping units. A mean surface rock density of 2440 kg/m³ for New Zealand is obtained from the analysis of the derived digital density model. The lower North Island mean of 2336 kg/m³ reflects the predominance of relatively young, weakly consolidated sedimentary rock, tephra, and ignimbrite compared to the South Island’s 2514 kg/m³ mean where igneous intrusions and metamorphosed sedimentary rocks including schist and gneiss are more common. All of these values are significantly lower than the mean density of the upper continental crust that is commonly adopted in geological, geophysical, and geodetic applications (2670 kg/m³) and typically attributed to the crystalline and granitic rock formations. The lighter density has implications for the calculation of the geoid surface and gravimetric reductions through New Zealand.     

基于量子态系数矩阵的纠缠判定准则

量子纠缠的判定问题（也称为可分性判定问题）是量子纠缠理论中的核心问题之一。越来越多的两体纠缠判定准则被提出,但其中大部分都难以理解和计算,或是难以应用到任意多体量子系统中。为此,对于一个任意的多体量子纯态,基于其系数矩阵提出了一个纠缠判定准则。通过考察一个量子态的系数矩阵的秩,就可以断定该状态是可分态还是纠缠态。通过具体的实例表明,所提出的方法可以找到一个多体量子态的具体可分形式,并且简单易懂、方便计算。     

Infographic restitution of the historic centre of the Spanish town of Oviedo

Our historic town centres possess an evocative quality that has recently led to considering these town centres a subject of scientific research, overtaking, if not contradicting, the romantic vision by which they obtained importance in the Western world from the late 18th century.Thus, the present work is framed in the existing and ultimately consolidated method of European universities, which analyse, with an increasing scientific rigour from many different perspectives, the knowledge of the abundant and rich historic town centres that geographically define our living environment.This study focuses on the reconstruction of the urban shape of the town of Oviedo in a series of stages that are marked by the cartographic data collected during the time of the study and that involve substantial changes to the urban fabric of the town. The study attempts to be a historical analysis of urban transformation. This research established a systematic study of earlier times when the urban form offered space patterns different from existing patterns. Using the current structure of the historic centre of Oviedo and the analysis of its pathologies throughout history as a starting point, this study considers the possibility of a methodical study of the past.This project presents the coexistence of parallel textual and visual accounts, which can be read together, as a new methodology to understand the spatial formation and transformation of urban landscapes.     

高电源抑制比低温漂带隙基准源设计

设计并实现了一种新的高PSRR、低TC带隙基准源。重点研究了带隙基准源电源抑制能力,尤其是高频PSRR,达到宽频带范围PSRR高性能指标。采用0.35μm BiCMOS工艺进行仿真,结果表明,PSRR在1 Hz频率下达-108.5 dB,在15 MHz频率下达-58.9 dB;采用二次温漂补偿电路使得带隙基准源常温下输出参考电压1.183 V,在-40℃⁹5℃温度范围内,温漂系数低达1.5 ppm/℃。