Stress in Leached Phase-Separated Glass

When a phase-separated glass is leached, stresses develop because of release of thermal stresses, creation of surface area, ion exchange, and hydration. Analyses are presented for the thermal stresses, including the portion that develops on cooling from the heat-treatment temperature to the setting temperature of the less viscous phase. During leaching, the interfacial energy of the residual phase increases, so that phase tends to contract. A more important effect is the contraction caused by removal of alkali and B₂O₃ from the residual phase during leaching. The extent of removal of B₂O₂ decreases with heat-treatment time, t_H , because the scale of the microstructure increases as t^1/3_H. The change in residual B₂O₂ content with t_H is shown to be consistent with diffusion-controlled ion exchange. The dependence of stress on t_H in partially leached glasses, measured by Drexhage and Gupta, results principally from the change in extent of ion exchange; the reduction in surface area with increasing t_H also has a significant effect on the stresses.     

风管摩擦阻力的直接计算方法

提出用高精度的反映密度、黏度和温度关系的经验公式和Colebrook公式计算风管摩擦阻力系数的方法。分析和算例表明，用该方法计算，计算结果比采用常用工程设计方法更为准确，为应用计算机进行风道设计提供了直接、简便的方法。     

"十五"后三年电力供需形势将十分严峻

根据详实的材料分析中国当前电力供需形势。虽然于2003年全国发电量将提前两年达到“十五”计划目标，但现在电力建设规模严重不足。预计“十五”后三年电力供需形势将十分严峻。当务之急是迅速开工建设一批大中型发电项目。     

Dead-beat Response in Multi-variable Systems

In this paper linear sampled data multi-variable synthesis is considered by the use of state difference equations. Murphy and Meksuwan's “1963” of approach is generalized for multi-variable systems. The non-interaction condition limits the achievement of dead-beat response depending on the nature of the input and the order of the individual transfer functions of the system. The method is general and can be applied to any polynominal input and also when non-linearities are present just after the compensator.     

Generalized Closed Loop Loci of Peak Amplitude,Phase and Frequency of a Third-order Control System

The generalized curves of closed loop peak magnitude, phase and frequency are derived here for a third-order control system. The regions in the parametric plane in which peak magnitudes exist and where the system is stable are also described     

Identification via Non-linear Filtering

Non-linear filtering problems are being recognized more arid more as significant. Generally, an exact solution is not available but must be approximated. However, this paper gives the exact non-linear filter associated with identifying a scalar stochastic dynamical system, dx(t)/dt=ax(t)+ξ(t), disturbed by gaussian white noise ξ(t) when the system state x(t) is observed in an additive gaussian white noise environment, i.e. z(t)=x(t)+η(t) is observed over the interval of time 0≤t≤T<∞. The plant parameter, a, is assumed to have the prior probability density P_A .(a). The solution, is obtained by giving the conditional probability density functional p(az(t), 0≤t≤T<∞). The minimum mean-square-error estimate, that is, the Bayes estimate or conditional expectation, is given along with the minimum-mean-square-error. Limiting cases are described.

This approach is a variation on the eigenfunction expansion schemes used in the stochastic signals in noise-detection problems by Helstrom and others. This approach circumvents solving various forms of the Fokker-Planck type of partial differential equations, for the conditional probability density. In general, the partial differential equations are highly coupled and non-linear.     

多管式低阻高效空气过滤器的阻力特性研究

介绍了一种多管式高效空气过滤器。在不同风量下对各种试验规格过滤器的阻力和过滤效率进行了实验测定，分析了过滤器结构形式对其阻力的影响，讨论了阻力的变化规律。结果表明：该过滤器具有阻力低、效率高的特点，是一种适应我国国情，节能、价廉、有实用价值的新型空气过滤设备。     

介质阻挡放电与脉冲电晕放电净化气态污染物的试验研究

利用自行研制的介质阻挡及脉冲电晕放电低温等离子体发生器对空气中氨、硫化氢、甲苯等5种气态污染物进行净化，并探讨了两种放电方式的原理和特点。试验结果表明：与介质阻挡放电相比，脉冲电晕放电具有更好的净化效果。     

变风量空调系统控制方法及试验台搭建

介绍了变风量(VAV)空调系统的特点,分析了VAV系统末端控制、AHU等的控制方法,着重对末端控制方法与AHU控制方法进了多种形式的比较,并以实际工程实例加以说明。