On real-time databases: concurrency control and scheduling

In addition to maintaining database consistency as in conventional databases, real-time database systems must also handle transactions with timing constraints. While transaction response time and throughput are usually used to measure a conventional database system, the percentage of transactions satisfying the deadlines or a time-critical value function is often used to evaluate a real-time database system. Scheduling real-time transactions is far more complex than traditional real-time scheduling in the sense that (1) worst case execution times are typically hard to estimate, since not only CPU but also I/O requirement is involved; and (2) certain aspects of concurrency control may not integrate well with real-time scheduling. In this paper, we first develop a taxonomy of the underlying design space of concurrency control including the various techniques for achieving serializability and improving performance. This taxonomy provides us with a foundation for addressing the real-time issues. We then consider the integration of concurrency control with real-time requirements. The implications of using run policies to better utilize real-time scheduling in a database environment are examined. Finally, as timing constraints may be more important than data consistency in certain hard realtime database applications, we also discuss several approaches that explore the nonserializable semantics of real-time transactions to meet the hard deadlines     

太钢电弧炉上应用四星接法MOA的必要性

分析了太钢电弧炉变压器高压侧相间过电压的产生原因，比较了用于限制过电压的避雷器的两种接法．结论是用四垦接法ＭＯＡ限制过电压的效果较显著．     

IC卡在电信领域的应用模式

本文列举了ＩＣ卡在电信领域及一些国家和地区的应用之后，给出了国际ＩＣ卡的应用发展模式，以供有关部门参考。     

新型可调剪切差平行分束偏光器设计

本文给出了一种新型可调的切差平行分束偏光器设计。它调节方便,可获得较大平行分束剪切差,并可一镜多用     

基于矩的异分辨率图象边界检测

（１）本文引入仿射变换，提出了一种用矩算子以民分辨率图象直接进行边界检测的方法，利用同分辨率图象正方形窗口的模板行矩的计算，推导出了相应用的边界参数公式。（２）本文提出一种隐线笥插值矩计算方法，得到一组与正方形窗口对应的正方形模板，避免了费时的预插值过程，（３）对本文提出的方法进行了实验验证，并给出了实验结果。     

Degenerate four-wave mixing spectroscopy excited by ultrashort laser pulses

A new method is described for spectroscopic diagnostics of combustion and explosion products, which makes it possible to study processes occurring at short times in hot and dense molecular gases. Pis’ma Zh. Tekh. Fiz. 23, 16–19 (March 26, 1997)     

A mixed design approach for probabilistic structural durability

In this paper, a mixed approach for probabilistic structural durability design of mechanical systems is proposed. In this approach, a deterministic design optimization that considers structural crack initiation and crack propagation lives at critical points of the structural component as design constraints is performed first. After an optimal design is obtained, a reliability analysis is performed to ascertain if the deterministic optimal design is reliable. If the probability of the failure of the deterministic optimal design is found to be acceptable, a reliability-based design approach that employs a set of interactive design steps, such as trade-off analysis and what-if study, is used to obtain a near-optimal design that is reliable with an affordable computational cost. A 3-D tracked vehicle roadarm is employed to demonstrate the feasibility of the proposed approach.     

高速铝箔分卷机的设计

介绍了一种成功开发及应用的高速铝箔分卷机的主要原理及结构特点。     

也谈轻型钢结构房屋柱基设计

对柱脚抗剪键的设置和计算中所取用的荷载组合提出个人观点,同时对轻钢结构柱脚螺栓受拉计算提出注意事项.