Research on speckle noise of laser Doppler velocimeter for the vehicle self-contained navigation

A novel multipoint layer-type laser Doppler velocimeter (MLLDV) is designed to measure the velocity of a vehicle for the self-contained navigation system. In order to investigate the speckle's influence on the Doppler spectrum, formulas of time-lagged covariance and speckle broadening were derived for our MLLDV. Simulations and experiments are made for detailed analysis. The results show that the time-lagged covariance of photocurrent is directly proportional to the incident angle, and is inversely proportional to the elevation fluctuation of the ground together with the velocity of the vehicle. Speckle broadening is a function of the vehicle's velocity, the 1/e² Gaussian spot radius and the phase correlation length of the ground. For our MLLDV, Doppler frequency and Doppler broadening are both directly proportional to the velocity of the vehicle. Besides, the ratio between Doppler broadening and the corresponding Doppler frequency is about 0.72% when the speed of the vehicle varies from 0 to 9.6 m/s.     

Complex-valued fractional statistics for D-dimensional harmonic oscillators

A system of isotropic harmonic oscillators obeying the Polychronakos fractional statistics with a complex parameter in a space having the dimension D>1$D>1$ is studied. Temperature dependences of the thermodynamic functions are analyzed in different temperature domains. The nature of the observed phase transitions is clarified. Both numerical and analytical estimates for the critical temperature are made depending on the number of particles, space dimensionality, and statistics parameter. Approximate correspondence with some other fractional statistics types is established.     

塑料光纤拉丝塔控制系统设计

为减小塑料光纤纤芯直径波动造成的非固有散射损耗,设计了一种新型光纤拉丝塔控制系统,详细阐述了其工作原理及软硬件实现过程。采用单片机作为核心处理部件,合理设计传感器测温电路、加热炉温度控制电路、直径测量和控制电路以及友好的人机界面。实验表明系统拉丝芯径范围宽(0.2～3mm),拉制光纤直径均匀,精度可控制在15μm以内。整个系统成本低,实用价值高,满足塑料光纤实验室研究需要,可供实际生产参考。     

Separation of Variables for a Lattice Integrable System and the Inverse Problem

We investigate the relation between the local variables of a discrete integrable lattice system and the corresponding separation variables, derived from the associated spectral curve. In particular, we have shown how the inverse transformation from the separation variables to the discrete lattice variables may be factorized as a sequence of canonical transformations.     

Double peaks on ac magnetization in a superconducting Pb-porous glass nanocomposite

Studies of temperature dependences of ac magnetization were carried out for a superconducting lead-porous glass nanocomposite. Double peaks were found on the imaginary part of ac magnetization which were accompanied with double steps on the real part. The lower-temperature anomalies in ac magnetization differed noticeably when they were obtained upon cooling and warming. The double peaks were treated as two phase transitions in the vortex system: the liquid-solid transition which occurs close to the onset of superconductivity and solid-solid one which is triggered by superconductivity in confined lead islands.     

Structural features of melts in the In-Bi system

A testing device for the resistivity of high-temperature melt was adopted to measure the resistivity of In-Bi system melts at different temperatures. The resistivity of In_xBi_100−x(x=0-100) melt is in linear relationship with temperature, which is within the temperature measuring range. The resistivity of melt lowers with the increase of the In content. Based on Nordheim law and combined with the experimental resistivity of In-Bi melts, we verified the existence of InBi atom clusters and estimated the mole fraction of the InBi atom clusters in the melt, and the estimated value shows fine consistency with the result in literature [1]. The study reveals that the structural feature of In-Bi melts can be briefly divided into two intervals: in the interval of 0-50 at% In, the structural feature of the melt is that InBi atom clusters distribute in matrices, which have similar properties of Bi; in the interval of 50 at%-100 at% In, the structural feature of the melt is that InBi atom clusters distribute in matrices, which have similar properties of In. The content of InBi atom clusters in In₅₀Bi₅₀ melts reaches a higher value when the temperature is cooled down to a point, which is 152 K above the melting point. At the same time, the melts have an obvious fluctuation of concentration, which leads to that the resistivity of the melts deviates from the linear relationship at high temperature.     

∧型四能级系统中的多重电磁诱导光透明研究

运用密度矩阵理论,研究了在外加相干耦合场作用下∧型四能级系统的吸收和色散特性。数值模拟表明：通过调节外加相干场的拉比频率强度,该系统可以单重、双重电磁诱导光透明现象,并在缀饰态表象中给出了定性解释。在双重电磁诱导透明现象中,透明窗的位置和吸收峰值可以通过调节外加相干场的失谐量来进行控制,而且透明点的位置可以连续变化。每个透明窗口在吸收最低时都伴随着高折射率,因此可以在此介质中实现超光速传播。     

Optimally chosen Nakajima–Zwanzig master equation for mean field approximation

We define an ensemble of projection operators, each of which has an exact associated Nakajima–Zwanzig master equation for quantum open system evolution. A mean field approximation for the memory kernels is introduced that yields a completely determined inhomogeneous master equation for every projection operator. A specific projection operator is then chosen so that the master equation optimally matches an abstract mathematical form which preserves positivity, complete positivity, and correctly equilibrates. We study a nitrogen vacancy center in diamond interacting with ¹³C impurities to illustrate the method.     

Admissible consensus and consensualization of high-order linear time-invariant singular swarm systems

Admissible consensus analysis and consensualizing controller design problems for high-order linear time-invariant singular swarm systems are investigated. Firstly, by projecting the state of a singular swarm system onto a consensus subspace and a complement consensus subspace, a necessary and sufficient condition for admissible consensus is presented in terms of linear matrix inequalities (LMIs). An approach to decrease the calculation complexity is proposed, by which only three LMIs independent of the number of agents need to be checked. Then, by using the changing variable method, sufficient conditions for admissible consensualization are shown. An explicit expression of the consensus function is given, and it is shown that the modes of the consensus function can be arbitrarily placed if each agent is R$R$-controllable and impulse controllable and the interaction topology has a spanning tree. Finally, theoretical results are applied to deal with cooperative control problems of multi-agent supporting systems.     

A microfluidic pumping mechanism driven by non-equilibrium osmotic effects

A mechanism is presented which drives a fluid flow using two chemically reacting molecular species and osmotic effects. For concreteness the mechanism is discussed in the context of a tube which at each end has a capping membrane which is permeable to the fluid but impermeable to the two molecular species. The chemical reactions occur at sites embedded in the capping membrane. Labeling the two chemical species A and B, at one end the reactions split each molecule of species B into two molecules of species A. On the other end two molecules of species A are fused together to form a single molecule of species B. A mathematical model of the solute diffusion, fluid flow, and osmotic effects is presented and used to describe the non-equilibrium steady-state flow rate generated. Theoretical and computational results are given for how the flow rate depends on the relative diffusivities of the solute species and the geometry of the system. An interesting feature of the pump is that for the same fixed chemical reactions at the tube ends, fluid flows can be driven in either direction through the tube, with the direction depending on the relative diffusivities of the solute species. The theoretical results are compared with three-dimensional numerical simulations of the pump.