Forward dynamics simulation of human body under tilting perturbations

Human body uses different strategies to maintain its stability and these strategies vary from fixed-foot strategies to strategies which foot is moved in order to increase the support base. Tilting movement of foot is one type of the perturbations usually is exposed to human body. In the presence of such perturbations human body must employ appropriate reactions to prevent threats like falling. But it is not clear that how human body maintains its stability by central nervous system (CNS). At present study it is tried that by presenting a musculoskeletal model of human lower extremity with four links, three degrees of freedom (DOF) and eight skeletal muscles, the level of muscle activations causes the maintenance of stability, be investigated. Using forward dynamics solution, leads to a more general problem, rather than inverse dynamics. Hence, forward dynamics solution by forward optimization has been used for solving this highly nonlinear problem. To this end, first the system’s equations of motion has been derived using lagrangian dynamics. Eight Hill-type muscles as actuators of the system were modeled. Because determination of muscle forces considering their number is an undetermined problem, optimization of an appropriate goal function should be practiced. For optimization problem, the characteristics of genetic algorithms as a method based on direct search, and the direct collocation method, has been profited. Also by considering requirements of problem, some constraints such as conservation of model stability are entered into optimization procedure. Finally to investigate validation of model, the results from optimization and experimental data are compared and good agreements are obtained.     

Running error for the evaluation of rational Bézier surfaces through a robust algorithm

Running error analysis of the corner cutting algorithm for rational Bézier surfaces is carried out and the sharpness of the corresponding error bounds is shown.     

Strong convergence of the forward–backward splitting method with multiple parameters in Hilbert spaces

Many problems arising from machine learning, signal & image recovery, and compressed sensing can be casted into a monotone inclusion problem for finding a zero of the sum of two monotone operators. The forward–backward splitting algorithm is one of the most powerful and successful methods for solving such a problem. However, this algorithm has only weak convergence in the infinite dimensional settings. In this paper, we propose a new modification of the FBA so that it possesses a norm convergent property. Moreover, we establish two strong convergence theorems of the proposed algorithms under more general conditions.     

正渗透过程中纳米碳管膜的盐水通道行为

以纳米碳管(CNT)仿生构筑正渗透(FO)膜, 采用分子动力学模拟的方法考察水和盐在由CNT(6,6)、CNT(7,7)、CNT(8,8)、CNT(9,9)、CNT(10,10)、CNT(11,11)等不同尺寸纳米碳管构筑膜中, 于2.5、3.75、5.0mol·L^-1等不同汲取液浓度下的传递行为. 纳秒级的模拟得到水分子在不同尺寸纳米碳管膜内的分布, 水通量的变化以及盐截留等情况. 模拟结果表明, 由CNT(8,8)构筑的正渗透膜表现出优异的通水阻盐性能.     

Robust and reliable forward–reverse logistics network design under demand uncertainty and facility disruptions

There are two broad categories of risk, which influence the supply chain design and management. The first category is concerned with uncertainty embedded in the model parameters, which affects the problem of balancing supply and demand. The second category of risks may arise from natural disasters, strikes and economic disruptions, terroristic acts, and etc. Most of the existing studies surveyed these types of risk, separately. This paper proposes a robust and reliable model for an integrated forward–reverse logistics network design, which simultaneously takes uncertain parameters and facility disruptions into account. The proposed model is formulated based on a recent robust optimization approach to protect the network against uncertainty. Furthermore, a mixed integer linear programing model with augmented p-robust constraints is proposed to control the reliability of the network among disruption scenarios. The objective function of the proposed model is minimizing the nominal cost, while reducing disruption risk using the p-robustness criterion. To study the behavior of the robustness and reliability of the concerned network, several numerical examples are considered. Finally, a comparative analysis is carried out to study the performance of the augmented p-robust criterion and other conventional robust criteria.     

Using PSO for a walk of a biped robot

This paper is a presentation of a work that consists to model a biped robot walk in simulation. The specific objective is to develop a strategy based on an evolutionary method. The chosen architecture to represent the biped includes ten degrees of freedom on ten articulations between seven links. This evolutionary method is a generation of articulation angles using a particle swarm optimization (PSO). This work invokes also the direct kinematic principle. The PSO guarantees the stability of the biped by using a constraint on the center of mass (CoM) and the polygon of support. Results show that this method is tempting for a high level development.     

X射线与CsI:Na转换屏作用规律的研究

本文用MonteCarlo方法模拟了轫致辐射X光子与CsI:Na转换屏的作用过程.给出了正向散射光子的角分布以及正向出射光子的能谱分布,指出正向散射光子的主要成分是CsI:Na的特征辐射光子,其能量为33.17和35.98keV.此外,还对吸收光子数与管电压和CsI:Na层厚度的关系进行了说明.     

Full asymptotics and Laurent series of layer potentials for Laplace's equation on the half‐space

We combine the calculus of conormal distributions, in particular the Pull‐Back and Push‐Forward Theorems, with the method of layer potentials to solve the Dirichlet and Neumann problems on half‐spaces. We obtain full asymptotic expansions for the solutions, show that boundary layer potential operators are elements of the full b‐calculus and give a new proof of the classical jump relations. En route, we improve Siegel and Talvila's growth estimates for the modified layer potentials in the case of polyhomogeneous boundary data. The techniques we use here can be generalised to geometrically more complex settings, as for instance the exterior domain of touching domains or domains with fibred cusps. This work is intended to be a first step in a longer program aiming at understanding the method of layer potentials in the setting of certain non‐Lipschitz singularities that can be resolved in the sense of Melrose using manifolds with corners and at applying a matching asymptotics ansatz to singular perturbations of related problems.     

ψ-混合随机变量序列的重对数律

本文讨论了同分布的 -混合序列其共同分布属于稳定分布(非高斯情形)吸引场部分和的Chover型重对数律.特别地当分布函数属于稳分布的正则吸引场时,得到了部分和及后置和更精细的结果,即积分检验的结果,由此立即可推出相应的Chover型重对数律.     

Forward equations for reflected diffusions with jumps

In this paper we obtain the forward equations associated with the evolution of the density, if it exists, of reflected diffusions on the positive orthant with jumps which form a marked point process whose random jump measure possesses a stochastic intensity. These results generalize the so-called generalized Dynkin equations for piecewise deterministic jump processes due to Davis. We then consider the stationary case where the existence of a stochastic intensity is not needed. The techniques are based on local times and the use of random jump measures. We discuss the application of these results to problems arising in queuing and storage processes as well as stationary distributions of diffusions with delayed and jump reflections at the origin.This research was supported in part by the Quebec-France Cooperative Research Program and by the Natural Sciences and Engineering Research Council of Canada under Grant OGP 0042024.