Locked discrete event systems: How to model and how to unlock

To model qualitative aspects of discrete event systems, i.e., the order of the events is of sole importance, we use a triple consisting of the set of all possible events (the alphabet), the set of all behavior (possible strings of events), and the set of all tasks (completed behavior). We use this view to model synchronous as well as asynchronous connection of systems. Moreover, it is easy to define notions like deadlock and livelock in this view. We give a method to construct a second system that, in connection with the original system, gets rid of its deadlock and/or livelock. A state-space representation is introduced. In this representation computations can be done effectively.     

Thermomechanical stress fields in high-temperature fibrous composites. I: Unidirectional laminates

This two-part paper presents a closed-form procedure for evaluation of estimates of local thermomechanical stress fields in two-phase fibrous composites and laminates. The first part is concerned with a unidirectional elastic laminate subjected to uniform mechanical loads and to uniform changes in temperature. Both phases are assumed to be elastic, with temperature-dependent moduli and expansion coefficients; the solution reflects the influence of thermomechanical interactions. Exact solutions are not possible for any real system, because the local geometry is not known in detail. Instead, estimates of the fields are found from a modified Mori-Tanaka approximation. Examples are presented for two SiC/Ti---Al---Nb composites. Local stresses of interest are found after cooling from fabrication to room temperature. The presence of local yielding, and the influence of coupling terms on the local stress magnitudes are examined. Extension of the results to laminated plates is presented in Part II (Dvorak, G.J., Chen, T. & Teply, J., Composites Science and Technology, 43 (1992) 359–368, this issue).     

翻领成型器领口曲线的程序计算展开法

根据翻领成型器领口曲线的数学模型，介绍一种利用计算器复杂公式存贮的特殊功能，预编程序计算相关参数。然后画领口曲线展开图的方法。     

一种便于观测的信号抽样及复原方法

利用倍频器，将重复频率与连续信号ｔ（ｔ）的频率相同的方波进行若干次倍频后，对连续信号进行抽样，从而获得离散的抽样信号ｆｓ（ｔ），再利用有源低通滤波器使其复原成连续信号ｆ（ｔ）。避免了一般抽样器不便于观测的缺点。     

Convergence of iterated boolean sums of simultaneous approximants

Explicit error estimates are given for the iterated Boolean sum of a sequence of simultaneous approximants; the rate of convergence is shown to be improved for smooth functions. The general results are applied in the case of the Bernstein, Durrmeyer and Stancu operators.     

可行性研究财务评价中利息的计算

介绍了可行性研究财务评价中利息计算的内容和方法。     

神经网络离散变结构控制的算法及其应用

本文首次将自适应线性神经元（Ａｄａｌｉｎｅ）用于离散变结构控制。以滑模面Ｓ（ｋ）＝０作为Ａｄａｌｉｎｅ元的希望输出，作为Ａｄａｌｉｎｅ元的实际输出，通过ＬＭＳ算法在线调整权值可保证滑态可达条件的满足。应用所提出的控制策略对泵控马达速度伺服系统进行控制，仿真表明控制效果是令人满意的。     

扩展有限递归进程模型

主要讨论离散事件动态系统的建模问题。由ＫＩｎａｎ和ＰＶａｒａｉｙａ提出的有限递归进程（ＦＲＰ）是描述并发离散事件动态系统的有力工具，但在其ＦＲＰ中，没有定义对数据变量的操作和条件转移算子。本文扩展ＦＲＰ包括这两方面内容。最后举例说明扩展ＦＲＰ的描述能力。     

Prediction of evaporation heat transfer coefficient and pressure drop of refrigerant mixtures

A study on the prediction of heat transfer coefficient (HTC) and pressure drop of refrigerant mixtures is reported. HTCs and pressure drops of prospective mixtures to replace R12 and R22 are predicted on the same cooling capacity basis. Results indicate that nucleate boiling is suppressed at qualities greater than 20.0% for all mixtures and evaporation becomes the main heat transfer mechanism. For the same capacity, some mixtures containing R32 and R152a show 8.0–10.0% increase in HTCs. Some mixtures with large volatility difference exhibit as much as 55.0% reduction compared with R12 and R22, caused by mass transfer resistance and property degradation due to mixing (32.0%) and reduced mass flow rates (23.0%). Other mixtures with moderate volatility difference exhibit 20.0–30.0% degradation due mainly to reduced mass flow rates. The overall impact of heat transfer degradation, however, is insignificant if major heat transfer resistance exists in the heat transfer fluid side (air system). If the resistance in the heat transfer fluid side is of the same order of magnitude as that on the refrigerant side (water system), considerable reduction in overall HTC of up to 20% is expected. A study of the effect of uncertainties in transport properties on heat transfer shows that transport properties of liquid affect heat transfer more than other properties. Uncertainty of 10.0% in transport properties causes a change of less than 6% in heat transfer prediction.     

Unrestricted Hartree-Fock approximation of the extended emery model

We use an unrestricted self-consistent Hartree-Fock approach to calculate the nature of doping states in the three-band Hubbard model. It turns out that for physically relevant parameter values one hole is localized within a small spin-polarized region where five Cu spins are aligned in the same direction. The spin polarization and binding energy between these spinpolaronic states are investigated as a function of different parameters including a Holstein-type electron-phonon coupling on the Cu sites. At higher doping concentration we observe the occurrence of afmon states where the holes are localized in a ring-shaped area. Inside this ring the antiferromagnetic order parameter has inverse sign with respect to the residual antifer-romagnetically ordered plane.