Application of stochastic optimal control to the suboptimal design of thrust-mass profiles

Stochastic optimal control techniques are applied to compare the performance of identical medium-range air-to-air missiles which have different thrust-mass profiles. The measure of the performance is the probability of reaching a lock-on-point with a favorable range of guidance and flight parameters, during a fixed time interval [0,t _f ], given that, during the flight, the trajectories of the missile are subjected to a variety of constraints including dynamic pressure constraints.     

小视角对颜色差别阀的影响

在均匀颜色空间的颜色差别计箅中,亮度和色彩的作用是相关且不同的,尤其是在目标尺度对人眼张角(亦称视角)小于30角度分的条件下观察,由于亮度差和色彩差受视角变化的影响程度不同步,使得人眼颜色差别分辨阈亦不确定。本文通过一定的试验和计算,探讨了在不同的亮度差和色彩差的情况下,颜色差别阈受视角影响的变化规律。     

同位网格上不可压流动的反欠松弛压力修正算法

本文提出了同位网格上的不可压流动压力修正算法,其中压力修正值由压力方程所求得。设计了分离式的动量插值方法,有效地避免了松弛因子对计算结果的影响和不合理压力场的出现。提出了构造压力方程的反欠松弛方法,该方法建立了稳定和加速计算收敛的一般途径。对经典算例的计算得到了满意的结果。     

简析"静止液体内部压强公式验证"实验的设计策略

“静止液体内部压强公式验证”在现行教材中有两种实验方法。通过分析实验的设计策略，说明其作用、效果及操作上的困难，指出合理的与不合理诸因素，从而提出改进实验的方法，化难为易，提高实验教学效果。     

The Properties of Light Pressure Force with High Order in Laser Fields

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Acoustic characterization and prediction for fan-duct-plenum-room integrations

This paper investigates mutual influence of duct and room acoustics in the whole fan-duct-plenum-room integrations. Applying the parametric design language of finite element software ANSYS (APDL), dimensional and positional influence on system acoustics has been studied. Models with different room dimensions, duct lengths, duct cross-sections, duct locations, duct discharges and duct elbow were constructed, and their characteristics were compared qualitatively. Results show that small rooms, short ducts, large duct cross-sections and bell mouth duct discharges help to increase room sound pressure levels (SPLs); SPLs in ducts and plenums are sensitive to duct dimensions and duct discharge types but insensitive to duct locations and room dimensions; duct elbows have relatively indistinct acoustic influence in each component. Based on the calculation results, a semi-experimental method was proposed for simply and approximately evaluating indoor acoustic spectra of fan-duct-plenum-room integrations, then an example was used to demonstrate the prediction process. Finally, by adopting several ideal models, sound field constitutions, duct and room wall admittances and duct end reflection were explored quantitatively. This study may give a detailed understanding of fan-duct-plenum-room acoustics for researchers, also it might provide a new, simple and approximate prediction method for professionals to evaluate and improve fan-ducted acoustics.     

Assessing contaminated hydrogen peroxide for safe storage and transportation using the FTAI

Hydrogen peroxide is a very versatile oxidizing agent, and it is also environmentally compatible considering that the products of its exothermic decomposition are oxygen and water.When kept in a clean temperature-controlled environment, the self-reaction (decomposition) rate is extremely low. However, it is well known that even a small amount of contamination will dramatically increase the reaction rate. This paper describes the use of the fast thermal activity interpreter (FTAI) instrument to examine the chemical reactivity of commercially available 50% hydrogen peroxide at two different temperatures (30 and 40°C) both with and without contamination. The results show that at 30°C a small amount of rust (330 ppm) increases the reaction rate of 50% hydrogen peroxide by a factor of 50. When the temperature is increased to 40°C, the reaction rate is further increased by almost a factor of four. The implication for reactivity management is that at this contamination level most practical vessel sizes would require emergency venting capability. An evaluation was then performed to determine the emergency venting requirement for the safe transportation or storage of the contaminated hydrogen peroxide. It was determined that for quantities of the material less than 5 gallons, conventional breather vents would be sufficient to accommodate the gas evolved. However, for larger quantities, a safety relief device would be needed. For example, for a 400-gallon tote bin at 40°C the required minimum vent area is estimated to be 4.3 in², corresponding to a minimum vent diameter of 2.3 inches.     

Asymmetric responses of international stock markets to trading volume

The major goal of this paper is to examine the hypothesis that stock returns and return volatility are asymmetric, threshold nonlinear, functions of change in trading volume. A minor goal is to examine whether return spillover effects also display such asymmetry. Employing a double-threshold GARCH model with trading volume as a threshold variable, we find strong evidence supporting this hypothesis in five international market return series. Asymmetric causality tests lend further support to our trading volume threshold model and conclusions. Specifically, an increase in volume is positively associated, while decreasing volume is negatively associated, with the major price index in four of the five markets. The volatility of each series also displays an asymmetric reaction, four of the markets display higher volatility following increases in trading volume. Using posterior odds ratio, the proposed threshold model is strongly favored in three of the five markets, compared to a US news double threshold GARCH model and a symmetric GARCH model. We also find significant nonlinear asymmetric return spillover effects from the US market.     

Bubble point pressure estimates from Gibbs ensemble simulations

Bubble pressure points of ethanol–1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea refrigerant) mixtures from the third Industrial Fluid Properties Simulation Challenge are computed using publicly available molecular simulation software. Several published force fields are compared against the known answers provided in the contest guidelines and the best force fields are used to make predictions for the unknown results.     

Using the gradients of temperature and internal parameters in Continuum ThermodynamicsIntroduction des gradients de température et de paramètres internes en Thermodynamique des Milieux Continus

In this paper, the possibility of using the gradients of the temperature and of the internal parameters as additional state variables in Continuum Thermodynamics is considered. The expressions of the two principles are discussed and Clausius–Duhem inequality is derived under an appropriate statement of the internal entropy production. Several formulations are proposed and compared to existing results in the literature. To cite this article: P. Ireman, Q.S. Nguyen, C. R. Mecanique 332 (2004).