氧—乙炔火焰钎焊在LF21铝合金上的应用

从铝钎焊机及具体工艺操作方面进行阐述，解决了LF21防锈铝用氧－乙烯火焰作为热源进行钎焊的工艺问题。     

连续出矿与大块物料振动输送机的发展概况

在对连续出矿和连续运搬设备进行介绍的基础上，对大块物料矿用振动输送机的国内外研制概况和发展方向进行了论述。指出它是２１世纪一种很有发展前途的新型矿山设备。     

低频采油技术及应用效果

介绍了低频采油技术的作用机理及其基本作业参数的选择，以两口采油井和一口注水井的低频脉冲处理情况为例，分析了其作用效果及孤东油田适合于低频处理的注、采井的油藏条件。     

Alternative regional specification and convergence of U.S. regional growth rates

We apply absolute beta convergence techniques to cross sectional per capita income data for alternative specifications of U.S. regions in order to detect whether U.S. regional growth rates are converging over relatively recent time periods. We also explore whether estimates of convergence differ between economic and political region specifications. We show that convergence of growth rates across regions of the U.S. has continued in modern times (1969–1997) for almost any regional specification and for all time frames considered. We do find, however, some difference in convergence rates between economic and political regions. Convergence coefficients, however, are remarkably similar across alternative economic region specifications. An earlier version of this paper was presented in February 2003 at the 42nd annual meetings of the Western Regional Science Association in Rio Rico, Arizona. We would like to thank our session participants in Rio Rico and three anonymous referees for helpful comments. Any remaining errors or oversights, however, are entirely our responsibility.     

Security services for applications of OSI in banking

The protection of financial information has always been critical to success in banking. Security has become much more visible now that the automation and interconnection of banking processes is becoming widespread. Most financial institution are moving towards international systems interworkng, eventually using products based on the Open Systems Interconnection model. Thus, it is essential that basic security services be incorporated into the OSI architecture. This paper reviews security needs for banking communications, surveys on-going standardization work in TC68 (Banking) and TC97/SC21, and concludes that the planned security services in OSI should satisfy banking requirements if completed quickly.     

Do vertical tax externalities lead to tax rates being too high? A note

When both vertical and horizontal externalities are at work in a federation, they generally distort levels of taxation in opposite directions. This article is an extension of the Keen and Kotsogiannis (Am Econ Rev March: 363–370, 2002) model. It focuses on state tax policy when states provide an industrial public good increasing firms’ marginal productivity rather than a residential public good intended to households. We find that some results related to whether equilibrium state taxes are likely to be too high or too low are much more complex when state-provided industrial public goods are considered. First, we show that in the presence of industrial public goods, a dominant vertical externality may result in state tax rates being too low (and not too high as it is the case with residential public goods). Second, we find that under certain conditions, horizontal and vertical externalities may point in the same direction and reinforce each other towards tax rates being too high or too low.     

基于AT89C51单片机的钢丝绳张力无线监测系统

设计了一个基于AT89C51单片机的罐笼钢丝绳张力在线监测系统,利用AT89C51单片机良好的软硬件资源,并采用了可在微机或单片机之间进行全双工无线通信的数传收发模块SA68D21DL,使数据传输及时,误码率低。该系统实现了在线监测张力,当张力超出限值时,及时报警,预防重大恶性事故的发生,并具有储存报警记录的功能,可打印成报表。     

Suboptimal robust synthesis for MIMO plant under coprime factor perturbations

Suboptimal robust synthesis for MIMO nominal system under coprime factor perturbations is considered in classical and non-classical statements. In the classical statement, weights of perturbations and upper bound on magnitude bounded exogenous disturbance are assumed to be known to controller designer. Suboptimal synthesis within ε tolerance is reduced to the solution of log₂(1/ε) standard mixed sensitivity problems of ℓ₁ optimization. In the non-classical statement, the upper bounds on perturbations and exogenous disturbance are to be estimated from measurement data and suboptimal synthesis is reduced to the solution of 1/ε mixed sensitivity problems.     

车21井区裂缝性油藏地质建模与工程设计一体化研究

为研究车21井区人工裂缝在地层中与天然裂缝沟通情况及裂缝真实展布形态,实现车21井区石炭系裂缝性油藏的经济有效开发,基于地质工程一体化研究思路,在建立储层真三维空间模型基础上,考虑油藏在纵向上岩性的展布和平面属性分布的非均质性,在真三维岩石力学储层中进行压裂裂缝模拟,形成了从地质建模到裂缝模拟的一体化研究流程。结果表明:真三维地质力学模型可真实表征储层岩石力学性质,CHHW2101、CHHW2102井的平均最小水平主应力分别为22.0 MPa和26.0 MPa,与2口井的井底停泵压力23.0 MPa与27.0 MPa相吻合。真三维裂缝模拟技术可更高效、更精准、更直接地对裂缝模拟效果进行评价,判断与天然裂缝连通情况。研究结果可为车21井区后续压裂井提供理论和技术支撑,填补中国国内一体化压裂的空白。