Deformation and regimes of liquid column during water exit of a partially submerged sphere using the front-tracking lattice Boltzmann method

When a solid sphere exits water at a given velocity, the liquid column is pulled out of a liquid reservoir. The present study focuses on the dynamic deformation of the liquid column and on the identification of the liquid column regime on the Weber number and dimensionless time (We-t*) map. The three-dimensional model of water exit has been established on the basis of the lattice Boltzmann method. A mass tracking algorithm was incorporated to capture the free surface, where the liquid–gas​ two-phase flow is simplified to a single-phase free surface flow. The surface tension is included by adding a perturbation term and the gravity as a body force is introduced in form of calculating the equilibrium distribution with an altered velocity. The contact angle condition in numerical simulation is not considered. The accuracy of the numerical results is demonstrated through the comparisons with the prior numerical and the experimental results in the literature. A parametric study has been conducted numerically on the radius and volume and of liquid column. Besides, the relationship between the pinch-off time of a liquid column and the Froude number has been obtained. Moreover, the evolution of the liquid column shape with a wide range of the Weber number and time scales are discussed based on the number of ligaments and droplets. The liquid column exhibits different characteristics and has been divided into three regimes. The transition between different regimes has been analyzed and the critical Weber number is given.     

Multiplexed time-correlated single-photon counting

We review the technique of multiplexed time-correlated single-photon counting whereby multiple fluorescence decay curves are recorded in parallel by statistically time-sharing a single time-to-amplitude converter. Application of the multiplexing technique to measuring the fluorescence lifetime topography of a self-absorbing sample is demonstrated. Further possibilities are discussed for multiplexed optical fiber sensor networks with built-in intelligence for detecting and discriminating between different metal ions in solution.     

A study on heat transfer during thermoplastic composite tape lay-up process

A study on heat transfer during thermoplastic composite tape lay-up process was done. To investigate the relation between major process variables, experiments as well as numerical simulations were performed. A small-scale tape lay-up system was built. A hot nitrogen torch was used to heat the prepreg tape. Right after the torch, a compaction roller was located to bond the prepreg plies. Temperatures inside the composite at four different locations through the thickness were measured, using thermocouples. Experiments were done for different process conditions. Numerical simulations also were performed, using the finite element code developed in this study. A numerical code was run for the same conditions as the experiment. Close agreement was observed between the numerical results and the experimental data.     

THE EFFECT OF DECREASING SYSTEM SIZE ON BIRTH AND DEATH MODELS OF OPEN-ACCESS FISHERIES AND PREDATOR-PREY ECOSYSTEMS

Birth and death simulation, developed by Pielou, is a form of Markov stochastic process for describing the time evolution of populations. Applied to modelling the human element of a fishery, it expresses two features of fishing effort dynamics absent in systems of differential equations: (1) discreteness of events, such as a fishing trip or entry of a vessel into the fleet, and (2) demography stochasticity, expressed as randomness in the time occurrence of successive events. Birth and death simulation is based on randomly selecting the waiting time between events from a negative exponential distribution, derived under the assumption of Markov. Histograms from commercial landings data of waiting times between events of boats returning to port in a Nova Scotia fishery yielded good agreement with the predicted negative exponential. Algorithms are presented for stochastically modelling two processes: (1) catch and (2) the open-access hypothesis for changes in fleet size in response to changing levels of profit. The solutions qualitatively diverge from that predicted by differential equations: As the numbers of vessels and fish schools decline (i.e., as the system size scale shrinks), a birth and death formulation predicts increasing instability of the predator-prey cycle solution about the deterministically stable open-access equilibrium. Open-access models are a form of predator-prey model. In choosing the minimum wilderness preserve area needed to sustain a population of top predators, numbered in the low hundreds, a predator-prey model formulated with differential equations could underestimate instability and thus the risk of extinction, when the discreteness and randomness of predator-prey birth, death, and capture events is significant.     

增益开关半导体激光器在外光注入下脉冲抖动的实验研究

采用增益开关半导体激光器作为注入种子光源来降低另一个增益开关DFB或Fabry-Perot（FP ）半导体激光器的脉冲抖动.相位噪声测量技术表明：增益开关FP激光器在外部脉冲光注入 下，激光脉冲抖动（均方值）由1.2ps降低至830fs；增益开关DFB半导体激光器在外脉冲注 入下，脉冲抖动由12ps降低至1.8ps. 关键词： 半导体激光器 光脉冲产生 时间抖动 光子注入     

EXIT DISTRIBUTION LEAVING A BALL FROM THE CENTER AND BROWNIAN MOTION

It is skowed that if the first exit distribution leaving any ball from the center is theuniform distribution on the sphere, then the Levy process is a scaled Brownian motion.The paper also gives a characterization of a continuous Hunt process by the first exitdistribution from any ball.     

Markov chains with exponentially small transition probabilities: First exit problem from a general domain. II. The general case

In this paper we consider aperiodic ergodic Markov chains with transition probabilities exponentially small in a large parameter . We extend to the general, not necessarily reversible case the analysis, started in part I of this work, of the first exit problem from a general domainQ containing many stable equilibria (attracting equilibrium points for the = dynamics). In particular we describe the tube of typical trajectories during the first excursion outsideQ.     

Determination of solvent recondensation or evaporation in the GC-precolumn by measurement of temperature changes on the column wall

Temperature measurements on the column outer well were used for detecting recondensation or evaporation of solvent inside the precolumn during injection or on-line transfer of large solvent volumes. This facilitates the choice of the most critical parameter of these techniques, i.e. oven temperature. When using the vaporizer/precolumn solvent split/gas discharge system, the dew point of the solvent is determined, either to just prevent solvent recondensation or to limit it to the capacity of the precolumn to retain liquid. In concurrent eluent evaporation through the loop type LC-GC interface, temperature measurement enables the determination of whether or not the flooded zone exceeds a given limit. Fanally, when solvent trapping is used (on-column injector/partially concurrent solvent evaporation evaporation or vaporizer/partial recondensation), temperature measurement near the front end of the flooded zone is used as a signal for accurate closure of the vapor exit shortly before the end of solvent evaporation.     

The Dirichlet problem for stable-like operators and related probabilistic representations

We study stochastic differential equations with jumps with no diffusion part, governed by a large class of stable-like operators, which may contain a drift term. For this class of operators, we establish the regularity of solutions to the Dirichlet problem up to the boundary as well as the usual stochastic characterization of these solutions. We also establish key connections between the recurrence properties of the jump process and the associated nonlocal partial differential operator. Provided that the process is positive (Harris) recurrent, we also show that the mean hitting time of a ball is a viscosity solution of an exterior Dirichlet problem.