Nonlinear optical properties of stimulated Brillouin scattering process in submerged object detection

Nonlinear optical properties of stimulated Brillouin scattering(SBS)to signal detection in water are analyzed.With the threshold characteristics,SBS only occnrs when the high power laser is focused in the SBS cell.When there is an object present in front of the focus,it leads to lower incident intensity and then SBS does not occur.The backward SBS signal depends on the focusing location.The nonlinear optical properties of SBS process in the focusing regime axe analyzed theoretically.With the object coming near to the focusing center,the backward Stokes signal rises up from zero to a maximum,and then grows to saturation.The delay time of the echo signal to pump signal can give the object location.In experiment,the peak position of varying rate of energy can give object location.     

A Communication Multiplexer Problem: Two Alternating Queues with Dependent Randomly-Timed Gated Regime

Two random traffic streams are competing for the service time of a single server (multiplexer). The streams form two queues, primary (queue 1) and secondary (queue 0). The primary queue is served exhaustively, after which the server switches over to queue 0. The duration of time the server resides in the secondary queue is determined by the dynamic evolution in queue 1. If there is an arrival to queue 1 while the server is still working in queue 0, the latter is immediately gated, and the server completes service there only to the gated jobs, upon which it switches back to the primary queue. We formulate this system as a two-queue polling model with a single alternating server and with randomly-timed gated (RTG) service discipline in queue 0, where the timer there depends on the arrival stream to the primary queue. We derive Laplace–Stieltjes transforms and generating functions for various key variables and calculate numerous performance measures such as mean queue sizes at polling instants and at an arbitrary moment, mean busy period duration and mean cycle time length, expected number of messages transmitted during a busy period and mean waiting times. Finally, we present graphs of numerical results comparing the mean waiting times in the two queues as functions of the relative loads, showing the effect of the RTG regime.     

On the efficiency of small-angle Čerenkov second harmonic generation in optical waveguides

It is well known that in the non-depleted pump approximation, the efficiency of a second harmonic generation (SHG) of a guided mode in a non-linear optical waveguide increases quadratically with the interaction length (P ₂ L ²), and linearly (P ₂ L) in the erenkov regime. The efficiency of the erenkov SHG in the waveguide with a non-linear substrate and linear guiding layer is known to be strongly peaked at a particular pump wavelength and a particular waveguide thickness, with the erenkov angle approaching zero. The known theory predicts an infinite efficiency value at the peak, however. In this contribution, a simple integral expression for the SHG efficiency in the erenkov regime is derived. For large erenkov angles and interaction lengths it yields the expected P ₂ L dependence, while in the limit of small erenkov angles the dependence is found to have the form of P L ^3/2, possessing also a finite value at the efficiency peak. The condition determining the accurate position of the efficiency peak in the waveguide thickness–pump wavelength plane is given, too.     

EMD与神经网络在气液两相流流型识别中的应用

本文提出了EMD与Elman神经网络相结合的气液两相流流型识别的新方法.将压差波动信号经验模态分解(EMD)后的固有模态函数(IMF)进行分析、提取IMF能量作为Elman神经网络的输入特征向量,对水平管内的气液两相流流型进行识别.实验结果表明:该方法优于BP网络且稳定、识别率高,具有可行性.     

Global existence and exponential stability for a contact problem between two thermoelastic beams

In this paper we analyze a dynamic unilateral contact problem between two thermoelastic beams. We establish the existence of a weak global-in-time solution, by a penalization method. Moreover, we study the asymptotic behavior of such a solution proving that the energy associated to the system decays exponentially to zero, as time goes to infinity.     

Boundary integral equations in time-dependent bending of thermoelastic plates

The initial-boundary value problems with the Dirichlet and Neumann boundary conditions arising in the theory of bending of thermoelastic plates with transverse shear deformation are reduced to time-dependent boundary integral equations by means of layer potentials. The solvability of these equations is then investigated in Sobolev-type spaces.     

Flow patterns and heat transfer in vertical upward air–water flow with surfactant

Flow patterns, the pressure drag reduction and the heat transfer in a vertical upward air–water flow with the surfactant having negligible environmental impact were studied experimentally in a tube of 2.5 cm in diameter. Visual observations showed that gas bubbles in the air–water solution with surfactant are smaller in size but much larger in number than in pure air–water mixture, at the all flow regimes. The transition lines in the flow regime map for the solution of air–water mixture with surfactant of the 300 ppm concentration are mainly consistent with the experimental data obtained in clear air–water mixture. An additive of surfactant to two-phase flow reduces the total pressure drop and decrease heat transfer, especially in the churn flow regime.     

Oxidative dehydrogenation of propane under steady-state and transient regimes over alumina-supported catalysts prepared from mixed V_2W_4O_（19）~（4-） hexametalate precursors

An integrated approach combining the development of an innovative catalyst and the research of a set of adequate operating conditions for the propane oxidative dehydrogenation (ODH) is described. The experimental set-up, specially designed for steady-state and transient studies is presented. The preparation method, the characterization and the performances in steady-state and transient regimes of catalysts based on V_2W_4O_(19)~(4-) Lindqvist isopolyanion used as a precursor and supported on alumina are reported. The influence of the preparation method of the catalyst and the role of water in the feed gas are more particularly discussed.     

Simultaneous establishing of stationary growth rate and composition of supercritical droplets at isothermal binary condensation in the diffusion-controlled regime

General integral relations expressing the droplet radius and time of the droplet nonstationary growth as nonlinear functions of solution concentration in the droplet have been derived. These relations are valid for a supercritical droplet (i.e., sufficiently large droplet, for which the Laplace pressure effect on the concentration at saturation of vapors is negligible) isothermally growing via stationary diffusion in the mixture of two condensing vapors and an incondensable carrier gas. The initial composition in the droplet may be arbitrary and partial molecular volumes of components are not fixed. Explicit analytical relations have been found for droplet composition and the droplet size as functions of time at small deviations from the stationary concentration in the growing droplet. These relations show that the assumption of the steady droplet growth rate is not valid for non-small deviations from the stationary concentration. Some illustrations of the general nonlinear theory have been done in situation when solution in the droplet can be considered ideal.     

Parameter space of the Rulkov chaotic neuron model

The parameter space of the two dimensional Rulkov chaotic neuron model is taken into account by using the qualitative analysis, the co-dimension 2 bifurcation, the center manifold theorem, and the normal form. The goal is intended to clarify analytically different dynamics and firing regimes of a single neuron in a two dimensional parameter space. Our research demonstrates the origin that there exist very rich nonlinear dynamics and complex biological firing regimes lies in different domains and their boundary curves in the two dimensional parameter plane. We present the parameter domains of fixed points, the saddle-node bifurcation, the supercritical/subcritical Neimark–Sacker bifurcation, stability conditions of non hyperbolic fixed points and quasiperiodic solutions. Based on these parameter domains, it is easy to know that the Rulkov chaotic neuron model can produce what kinds of firing regimes as well as their transition mechanisms. These results are very useful for building-up a large-scale neuron network with different biological functional roles and cognitive activities, especially in establishing some specific neuron network models of neurological diseases.