高阶离散时间多智能体系统的量化一致性

研究高阶线性多智能体系统在有向量化链路信息拓扑下的一致性问题,首先提出了包含智能体自身与其邻居量化信息的线性一致性协议,其次利用提出的线性变换,将一致性问题转化为稳定性问题,基于稳定性理论,得到基于矩阵Schur稳定性的充要条件,并得到依赖于信息拓扑、系统动态和整个系统初始状态的一致性函数,最后,通过求解代数Riccati不等式,提出增益矩阵的设计过程.

离散承载体系的材料力学方法

离散承载体系的材料力学方法汪进（安徽工学院机械系，合肥２３００６９）材料力学研究的是构件受载后的应力和变形，这里的构件是指连续、均质、弹性的“杆件”，其截面通常为单连通的几何图形，如圆、圆环、矩形、工字型等（图１）。在工程上，有些受载对象不是连续构件...

有限元离散化变分原理及精化元法

对线性和几何非线性有限元离散体系，建立了放松单元间协调约束的不协调元和杂交变分原理．由此建立了精化不协调元和精化杂交元方法，保证了收敛、无病态和高精度．

多种流形覆盖方式耦合的数值流形法及其应用

为了更好地利用数值流形法(NMM)模拟连续和非连续问题,根据NMM数学覆盖选择的灵活性,将有限元网格作为一种数学覆盖方式生成流形覆盖系统以避免细小流形单元的出现,并提出了将单个材料体描述为一个流形单元的独立覆盖方法。运用多种覆盖方式相耦合的方法模拟了混凝土的细观拉压模型,以及一个复杂结构岩质边坡模型,模拟结果较好地再现了相应的力学变形破坏过程。多种覆盖方式的耦合使得构建的NMM模拟模型更加合理;独立覆盖方式的使用降低了构建离散体系NMM模型的复杂程度,并减少了模型中的单元数量以及不连续面上的接触数量,提高了模拟计算效率。

Direct Numerical Simulation of Particle Dispersion in Gas-Solid Compressible Turbulent Jets

A numerical method was developed to directly simulate the compressible, particle-laden turbulent jets.The fourth order compact finite difference schemes were used to discretize the space derivatives. The Lagrangian method was adopted to simulate the particle motion based on one-way coupling. It is found that the turbulent intensity profiles attain self-similar status in the jet downstream regions. At the Stokes number of 1, particles are concentrated largely in the outer boundaries of the large-scale vortex structures with the most uneven distribution and the widest dispersion in the lateral direction. Particles at the much smaller Stokes numbers are distributed evenly in the flow field, and the lateral dispersion is also considerable. Distribution of particles at much larger Stokes numbers is more uniform and the lateral dispersion becomes small. In addition, the inflow conditions have different effects on the particle dispersion. The direct numerical simulation (DNS) results accord with the previous experiments and numerical studies.

A discrete multi-swarm optimizer for radio frequency identification network scheduling

Due to the effectiveness, simple deployment and low cost, radio frequency identification （RFID） systems are used in a variety of applications to uniquely identify physical objects. The operation of RFID systems often involves a situation in which multiple readers physically located near one another may interfere with one another＇s operation. Such reader collision must be minimized to avoid the faulty or miss reads. Specifically, scheduling the colliding RFID readers to reduce the total system transaction time or response time is the challenging problem for large-scale RFID network deployment. Therefore, the aim of this work is to use a successful multi-swarm cooperative optimizer called pseo to minimize both the reader-to-reader interference and total system transaction time in RFID reader networks. The main idea of pS20 is to extend the single population PSO to the interacting multi-swarm model by constructing hierarchical interaction topology and enhanced dynamical update equations. As the RFID network scheduling model formulated in this work is a discrete problem, a binary version of PS20 algorithm is proposed. With seven discrete benchmark functions, PS20 is proved to have significantly better performance than the original PSO and a binary genetic algorithm, pS20 is then used for solving the real-world RFID network scheduling problem. Numerical results for four test cases with different scales, ranging from 30 to 200 readers, demonstrate the performance of the proposed methodology.

Grayscale image encryption algorithm based on chaotic maps

A new image encryption/decryption algorithm has been designed using discrete chaotic systems as aSP (Substitution and Permutation) network architecture often used in cryptosystems. It is composed of two mainmodules: substitution module and permutation module. Both analyses and numerical results imply that the algo-rithm has the desirable security and efficiency.

Improved Consensus Speed for Discrete-Time Multi-agent Systems

The consensus problem of a linear discrete-time multi- agent system with directed communication topologies was investigated. A protocol was designed to solve consensus with an improved convergence speed achieved by designing protocol gains. The clo6ed-loop multi.agent system converged to an expected type of consensus function, which was divided into four types： zero, non- zero constant vector, bounded trajectories, and ramp trajectories. An algorithm was further provided to construct the protocol gains, which were determined in terms of a classical pole placement algorithm and a modified algebraic Riccati equation. Finally, an example to illustrate the effectiveness of theoretical results was presented.

Optimization of volume to point conduction problem based on a novel thermal conductivity discretization algorithm

A conduction heat transfer process is enhanced by filling prescribed quantity and optimized-shaped high thermal conductivity materials to the substrate. Numerical simulations and analyses are performed on a volume to point conduction problem based on the principle of minimum entropy generation. In the optimization, the arrangement of high thermal conductivity materials is variable, the quantity of high thermal-conductivity material is constrained, and the objective is to obtain the maximum heat conduction rate as the entropy is the minimum.A novel algorithm of thermal conductivity discretization is proposed based on large quantity of calculations.Compared with other algorithms in literature, the average temperature in the substrate by the new algorithm is lower, while the highest temperature in the substrate is in a reasonable range. Thus the new algorithm is feasible. The optimization of volume to point heat conduction is carried out in a rectangular model with radiation boundary condition and constant surface temperature boundary condition. The results demonstrate that the algorithm of thermal conductivity discretization is applicable for volume to point heat conduction problems.

二维颗粒气体在堆积过程中的能量耗散

通过高速摄像的方法观测了玻璃颗粒组成的准二维气态颗粒流的冷凝耗散过程,并和理想情况下的均匀耗散的颗粒流体理论作了比较,实验发现气态颗粒部分在耗散堆积过程中近似地满足高斯分布;从动能的结果来看,实际耗散过程和流体理论所预测的不同.实验发现冷凝分为两个阶段:当动能的贡献以气体颗粒为主时,发现颗粒以恒定的速度堆积,动能耗散主要由其中以气态分布的颗粒的沉积速率α,颗粒温度T和气态部分的平动速度νg决定;当气态颗粒数目趋向于0,能量耗散主要来自于密堆颗粒的表面层部分,耗散速度和表面层的"黏性"有关,堆积速率和能量耗散速度都会随着时间呈指数的衰减.

Parallel architecture and optimization for discrete-event simulation of spike neural networks

Spike neural networks are inspired by animal brains,and outperform traditional neural networks on complicated tasks.However,spike neural networks are usually used on a large scale,and they cannot be computed on commercial,off-the-shelf computers.A parallel architecture is proposed and developed for discrete-event simulations of spike neural networks.Furthermore,mechanisms for both parallelism degree estimation and dynamic load balance are emphasized with theoretical and computational analysis.Simulation results show the effectiveness of the proposed parallelized spike neural network system and its corresponding support components.

Coupled two-dimensional discrete element and multibody dynamic modeling for interaction of the soil and rough shaped rigid bodies

The study of soil and rigid body system interactions is very important for the exploration of the Moon and Mars worldwide.The discrete element method(DEM)is a relatively accurate simulation method to study dry sand soil mechanical properties.However,it is not suitable for bodies that are in mutual contact,connected due to constraints or have complex inertia properties due to their geometry.An efficient combination of the two-dimensional discrete element and multibody dynamic modeling method is proposed to solve the problem,in which the contacts and frictions among the granular spheres and the multibody system,including the smooth and rough rigid bodies,are taken into account.In this work,the soil field is modeled by a two-dimensional DEM,and the dynamics of the constrained rigid body system are modeled by the Cartesian method.A detection algorithm is developed to address the interactions between spherical discrete elements and roughly shaped rigid bodies.The advantage of this coupled method is that it enables the simultaneous capture of both responses.Finally,the program is verified by simulation experiments of the three-ball collision and the collision among the rectangular bars and the three balls.Based on this,the movement of the toothed wheel in the granular matter is analyzed,and the results show that the wheel with six teeth and 30°inclination has the fastest forward speed.In extraterrestrial objects,the wheel grip worsens,but the forward speed first increases and then decreases with decreasing gravity acceleration and loads on wheels,which proves that the coupled two-dimensional DEM and multibody dynamic program is effective in solving engineering problems.

Collisional Efect on Weibel Instability with Semi-Relativistic Maxwellian Distribution Function

In this paper, the Coulomb collisional effect of electron-ion on the growth rate of Weibel instability is investigated based on the semi-relativistic Maxwellian distribution function in dense and unmagnetized plasma. An analytical expression was derived for the dispersion relation of Weibel instability for two limit cases [ξ = ω＇/k‖T‖ 〉〉 1 and ｜ξ｜ 〈〈 1. In limit ｜ξ｜ 〉〉 1 the dispersion relation only includes a real part and in limit ｜ξ｜ 〈〈 1 the imaginary part of the frequency of waves＇ instability plays a role in the dispersion relation. In limit ｜ξ｜ 〈〈 1, the two quantities μ and η, that are due to the relativistic and collisional effects, will appear in the growth rate of Weibel instability. The growth rate of Weible istability will be increased through decreasing the Coulomb collisional frequency and also increasing the temperature anisotropic parameter in strong relativistic limit.

Leader-Following Consensus for Discrete-Time Multi-Agent Systems with Parameter Uncertainties Based on the Event-Triggered Strategy

In this paper, the leader-following consensus for discrete-time nmlti-agent systems with parameter uncertainties is investigated based on the event-triggered strategy. And the parameter un- certainty is assmned to be norm-bounded. A consensus protocol is designed based on the event-triggered strategy to make the multi-agent systems achieve consensus without continuous communication among agents. Each agent only needs to observe its own state to determine its own triggering instants under the triggering function in this paper. In addition, a sufficient condition for the existence of the event- triggered consensus protocol is derived and presented in terms of the linear matrix inequality. Finally, a numerical example is given to illustrate to efficiency of the event-triggered consensus protocol proposed in this paper.

Discrete time transfer matrix method for dynamics analysis of complex weapon systems

Efficient, precise dynamic modeling and analysis for complex weapon systems have become more and more important in their dynamic design and performance optimizing. As a new method developed in recent years, the discrete time transfer matrix method of multibody system is highly efficient for multibody system dynamics. In this paper, taking a shipboard gun system as an example, by deducing some new transfer equations of elements, the discrete time transfer matrix method of multibody sys- tem is used to solve the dynamics problems of complex rigid-flexible coupling weapon systems successfully. This method does not need the global dynamic equations of system and has the low order of system matrix, high computational efficiency. The proposed method has advantages for dynamic design of complex weapon systems, and can be carried over straightforwardly to other complex mechanical systems.

Rapid proton diffusion in hydroxyl functionalized imidazolium ionic liquids

There is considerable interest in using ionic liquids(ILs) as protic electrolytes. However, the reported proton transfer rate in ILs is quite slow. In this study, we report functionalizing imidazolium ILs with alcohol hydroxyls, aiming at constructing hydrogen bonding networks in the electrolyte, can stimulate fast proton hopping transfer. For demonstration, the diffusion of proton and Cl. in 1-(3-hydroxypropyl)-3-methylimidazolium tetrafluoroboride(C_3OHmimBF_4) were studied using cyclic voltammetry and potentiostatic method at 30 °C. The diffusion coefficient of proton is about one order of magnitude higher than that of Cl. in the same electrolyte, and about 5 times that of proton in the non-hydydroxyl 1-(butyl)-3-methylimidazolium tetrafluoroboride(BmimBF_4) when normalized to the diffusion coefficients of Cl. in respective ILs. In the meantime, 1H NMR spectra revealed a strong hydrogen bonding interaction between proton and C_3OHmimBF_4 which is absent between proton and BmimBF_4, thus the significantly higher diffusion coefficient of proton in C_3OHmimBF_4 may suggest the formation of effective hydrogen bonding networks, enabling rapid proton hopping via the Grotthuss mechanism.