Consensus problems for high-order linear time-invariant swarm systems

Consensus problems for high-order continuous-time linear time-invariant swarm systems with directed interaction topologies are investigated. A new method to deal with consensus problems is proposed based on state space decomposition. Two subspaces of a complex space are introduced, namely a consensus subspace and a complement consensus subspace. Based on this decomposition, necessary and sufficient conditions for consensus and consensualizability are presented respectively. An approach for determining and designing the consensus function which may be time-varying is shown. The applications of theoretical results in multi-agent supporting systems are studied.     

Own external atmosphere of space vehicles and its influence on parameters of radio signals of on-board radio systems

We consider the influence of the solar ultraviolet emission on the photoionization of the working body of drainage systems and microthruster units of a space vehicle, which leads to an increase in the decay of radio-waves of its radio systems. It is necessary to choose the working body of the microthruster units of the space vehicle orienting towards the substances with a low photoionization section (hydrazine, methyl alcohol, etc.). When choosing the working frequencies of radio systems it is necessary to orient oneself towards higher frequencies (hundreds and thousands of megahertz).     

事件空间中非完整非保守系统的守恒量存在定理及其逆定理

提出了事件空间中非完整非保守系统守恒定律构成的一般途径.首先，列写系统的运动微分方程，给出积分因子的定义.其次，详细地研究了守恒量存在的必要条件，并建立了事件空间中非完整非保守系统的守恒量存在定理及其逆定理.最后，举例说明结果的应用. 关键词： 事件空间 非完整非保守系统 积分因子 守恒定理     

Conformal invariance and conserved quantities of general holonomic systems in phase space

This paper studies the conformal invariance and conserved quantities of general holonomic systems in phase space. The definition and the determining equation of conformal invariance for general holonomic systems in phase space are provided. The conformal factor expression is deduced from conformal invariance and Lie symmetry. The relationship between the conformal invariance and the Lie symmetry is discussed, and the necessary and sufficient condition that the conformal invariance would be the Lie symmetry of the system under the infinitesimal single-parameter transformation group is deduced. The conserved quantities of the system are given. An example is given to illustrate the application of the result.     

Controlling and synchronizing space time chaos

Control and synchronization of continuous space-extended systems is realized by means of a finite number of local tiny perturbations. The perturbations are selected by an adaptive technique, and they are able to restore each of the independent unstable patterns present within a space time chaotic regime, as well as to synchronize two space time chaotic states. The effectiveness of the method and the robustness against external noise is demonstrated for the amplitude and phase turbulent regimes of the one-dimensional complex Ginzburg-Landau equation. The problem of the minimum number of local perturbations necessary to achieve control is discussed as compared with the number of independent spatial correlation lengths.     

声脉冲法空间电荷测量系统的研究

气体中空间电荷的分布与电晕放电的机理紧密相关, 获取电晕放电过程中空间电荷分布对深入研究电晕放电起始、自持过程有着重要作用, 但是如何准确获得电晕放电过程中的空间电荷分布一直是国际上尚未解决的难题. 本文基于声脉冲法提出一种电场信号解耦算法, 推导了空间电荷在声场中被调制产生的电场信号与声脉冲信号和空间电荷密度之间的数值关系, 讨论了不同测量情况下声发射系统的设计要求; 搭建了一套可用于实时测量针板电极电晕放电空间电荷分布的非接触式测量系统, 该系统主要包括声脉冲发生模块、空间电荷模块及电场信号解耦算法模块. 运用该系统实现了声脉冲激发作用下电场信号的测量, 通过提出的电场信号解耦算法得到了空间电荷密度, 对其测量结果与电晕电流法测量结果进行比较, 验证了电场信号解耦算法的有效性. 该算法可以应用于空间电荷一维、二维和三维测量系统中.     

Unattainability of a purely topological criterion for the existence of a phase transition for nonconfining potentials

The relation between thermodynamic phase transitions in classical systems and topology changes in their configuration space is discussed for a one-dimensional, analytically tractable solid-on-solid model. The topology of a certain family of submanifolds of configuration space is investigated, corroborating the hypothesis that, in general, a change of the topology within this family is a necessary condition in order to observe a phase transition. Considering two slightly differing versions of this solid-on-solid model, one showing a phase transition in the thermodynamic limit and the other not, we find that the difference in the quality or strength of this topology change appears to be insignificant. This example indicates the unattainability of a condition of exclusively topological nature which is sufficient to guarantee the occurrence of a phase transition in systems with nonconfining potentials.     

Constructing symmetric informationally complete positive-operator-valued measures in Bloch space

Here we study the construction of symmetric informationally complete positive-operator-valued measures (SIC-POVMs) in the Bloch space. In this space an SIC-POVM corresponds to a regular simplex, that is a set of real equiangular, unitary vectors. Since the Bloch space also contains vectors which do not describe quantum states, it is necessary to add an extra condition to enforce the members of the simplex to describe pure quantum states. We show that in the case of a three-dimensional quantum systems it is possible to find such a simplex in an analytical way. The solution turns out to be unitarily equivalent to a Weyl-Heisenberg covariant SIC-POVM.     

Relative equilibria in systems with configuration space isotropy

We present a framework for studying Lagrangian and Hamiltonian systems with symmetries, near points with configuration space isotropy. We use twisted parametrisations corresponding to phase space slices based at zero points of (co-)tangent fibres. Given a hyperregular Lagrangian, we find a Legendre transform in the twisted coordinates. For simple mechanical systems, we state necessary and sufficient conditions for the existence of relative equilibria in terms of an augmented-amended potential.     

Conformal Invariance and a New Type of Conserved Quantities of MechanicalSystems with Variable Mass in Phase Space

Conformal invariance and a new type of conserved quantities of mechanical systems with variable mass in phase space are studied. Firstly, the definition and determining equation of conformal invariance are presented. The relationship between the conformal invariance and the Lie symmetry is given, and the necessary and sufficient condition that the conformal invariance would be the Lie symmetry under the infinitesimal transformations is provided.Secondly, a new type of conserved quantities of the conformal invariance are obtained by using the Lie symmetry of the system. Lastly, an example is given to illustrate the application of the results.     

Device-independent tests of classical and quantum dimensions

We address the problem of testing the dimensionality of classical and quantum systems in a "black-box" scenario. We develop a general formalism for tackling this problem. This allows us to derive lower bounds on the classical dimension necessary to reproduce given measurement data. Furthermore, we generalize the concept of quantum dimension witnesses to arbitrary quantum systems, allowing one to place a lower bound on the Hilbert space dimension necessary to reproduce certain data. Illustrating these ideas, we provide simple examples of classical and quantum dimension witnesses.     

Dynamics of the wigner distribution function: conservation of positivity in time

The necessary and sufficient conditions are found under which the Wigner distribution function conserves (i) positivity, and (ii) factorization. The proof is based on the study of the continuous representation of three-dimensional linear-canonical-transformed minimum-uncertainty-states. The validity of (i) and (ii) for all initial conditions leads to quadratic Hamiltonians; when the condition is relaxed to the validity for only some initial conditions, non-quadratic systems are obtained. In all the above cases, the Wigner function is a true probability and follows the classical trajectory in phase space. The calculational advantage of the method here proposed is shown in the study of parabolic tunneling in a uniform magnetic field.     

Aperiodic crystals: A contradictio in terminis?

Although in the prevailing view a necessary condition for having a crystalline phase is lattice periodicity, it has become clear in the last decades that there are physical systems with many properties of the usual crystalline state but without three-dimensional lattice periodicity. Incommensurate modulated crystals have been known now for some time, and a couple of years ago much excitement was raised by the discovery of quasicrystals, systems with long-range order but with five-fold symmetry axes, which exclude lattice periodicity.A discussion is given of the various generalizations of the concept of lattice periodicity. In fact, these go from ordinary periodic crystal st structures to almost chaotic ones. One of these is the notion of quasiperiodicity. Section two deals with a special type of these quasiperiodic systems, tilings or space fillings with tiles or blocks of a small number of types. In section three the symmetry of quasiperiodic systems is discussed. Here the embedding into a higher-dimensional space is the key concept. Section four deals with N-dimensional crystallographic groups that occur as symmetry groups of quasiperiodic systems, so called superspace groups. In section five the diffraction from quasiperiodic systems is treated, and in section six it is shown that in some cases quasiperiodic structures may be approximated by periodic ones, and that periodic systems sometimes are more conveniently described by quasiperiodic ones. The emphasis in the symmetry discussion is on quasicrystals.This is even more so in the remaining sections. Section seven gives a brief account of the many experimental data, section eight describes what is known about the microscopic structure. Imperfections are even more important for quasiperiodic systems than for periodic ones. They are discussed in section nine.Not only microscopically do quasiperiodic systems have similarities with ordinary crystals, but also macroscopically. The morphological laws may be generalized to quasiperiodic systems, as shown in section ten. The consequences of quasiperiodicity on the physical properties is still to a large extent unclear. Mathematically they differ much from periodic systems. A discussion of a number of results is given in section eleven.     

Image acquisition and processing in passive radiovision systems

We consider the principles and methods of radio-thermal imaging in the millimeter wavelength band. An implemented system operating at a wavelength of 3 mm is briefly described, and its parameters are given. A method used to neutralize dynamic aberrations, which is necessary to create high-speed radiovision systems, is described. Super-resolution algorithms, which are the methods of improving the angular (space) resolution by using mathematical processing of the experimental data, are presented. The described results confirm the efficiency of the methods considered. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 8, pp. 664–672, August 2006.     

不同地区大气光学湍流内外尺度测量

 用光学湍流参数自动测量系统对内陆地区和沿海地区光学湍流内外尺度进行了大量的实验观测。分析了湍流尺度的日变化规律,给出了其频数分布。结果表明：两地内尺度的均值为十几mm,外尺度的均值约为2 m;内陆地区内尺度日变化趋势较为复杂,而外尺度的日变化趋势与湍流强度十分相似;沿海地区内外尺度与湍流强度均无明显关系。大气湍流尺度的大小和分布状态是随时间和空间变化的,因此,在估算实际大气湍流对光学系统的影响时,需要实测湍流尺度以便得到准确的结果。     

On the inverse problem in statistical mechanics

For quantum spin systems it is known that for a suitable space of potentials the equilibrium states areW*-dense in the set of all translation invariant states. The problem discussed in this paper is how to recognize such equilibrium states and how to find the corresponding potential. A necessary and sufficient condition for a state to be an equilibrium state for some potential is given in Sect. 3.     

Excitation of waves in magnetoactive plasma by a strongly “spread” inhomogeneous electron beam

The stability of beam-plasma systems is studied assuming that the distribution of beam-electrons in the velocity space corresponds to the first period of the quasilinear relaxation. The necessary condition is derived for the usual quasilinear equations to be applicable within the whole period of quasilinear relaxation.The authors wishes to thank Dr. R. Klíma for his interest in this paper.     

Two-Step Deterministic Remote Preparation of an Arbitrary Quantum State

We present a two-step deterministic remote state preparation protocol for an arbitrary qubit with the aid of a three-particle Greenberger-Horne-Zeilinger state. Generalization of this protocol for higher-dimensional Hilbert space systems among three parties is also given. We show that only single-particle von Neumann measurements, local operations, and classical communication are necessary. Moreover, since the overall information of the quantum state can be divided into two different pieces, which may be at different locations, this protocol may be useful in the quantum information field.     

"Metric" complexity for weakly chaotic systems

We consider the number of Bowen sets necessary to cover a large measure subset of the phase space. This introduces some complexity indicator characterizing different kinds of (weakly) chaotic dynamics. Since in many systems its value is given by a sort of local entropy, this indicator is quite simple to calculate. We give some examples of calculations in nontrivial systems (e.g., interval exchanges and piecewise isometries) and a formula similar to that of Ruelle-Pesin, relating the complexity indicator to some initial condition sensitivity indicators playing the role of positive Lyapunov exponents.