德国联邦物理技术研究院(PTB)气体微流量计量评介

在真空技术应用中 ,高精度气体微流量计用于连续膨胀法校准系统压力的产生、漏孔漏率的测量以及真空泵抽速的测定。PTB先后研制了三代气体微流量计 ,第一代为手动型 ,第二代为半自动型 ,第三代为全自动型。本文详细介绍了PTB研制的气体微流量计的性能和特点 ,并介绍了气体微流量计在真空漏孔的漏率测量方面的应用。另外 ,还介绍了PTB最近研制的大气压力下漏孔漏率测量系统的性能和特点     

储运罐区计算机监测系统的开发与应用

储运罐区计算机监测系统是石化企业自动控制的薄弱环节。中国石油集团公司抚顺石油一厂使用ZYG-101型电子智能液位仪，以及使用FIX组态软件完成该系统的数据库组态、工艺流程显示、实时和历史趋势显示、报警和报表等处理过程，通过二次表的串行口与计算机进行通信，由计算机实时监测每个罐的各种重要参数。运行证明：该系统测量误差小，数据实时性好．易于存储及远程传送，较理想地达到储运罐区的自动检测功能。     

Optimum power-saving method for power MOSFET width of DC/DC converters

An optimum power metal-oxide-semiconductor field effect transistor (MOSFET) width technique is proposed for enhancing the efficiency characteristics of switching DC-DC converters. By implementing a one-cycle buck DC-DC converter, it is demonstrated that the dynamic power MOSFET width controlling technique has a much improved power reduction whether the load current is light or heavy. The maximum efficiency of the buck converter is ~92% with a 3% efficiency improvement for the heavy load condition. The efficiency is further improved by ~16% for the light load condition as a result of the power reduction from the large power MOSFET transistors. Also proposed is a new error-correction loop circuit to enable a better load regulation than that of previous designs. Compared with the adaptive gate driver voltage technique, the optimum power MOSFET width can achieve a significant improvement in power saving. It is also superior to the low-voltage-swing MOSFET gate drive technique for switching DC-DC converters     

Preparation and characterization of cuprous iodide nanoparticles

A new technique for the preparation of CuI nanoparticles from CuSO₄ and KI ethanol solutions has been developed. Preparation conditions were optimized through a series of experiments. Under these conditions, the yield of CuI reached 95.39%. The product was characterized and the reaction kinetics was studied. The results show that the product takes a roughly spherical shape with an average particle size of less then 50 nm. The activation energy of the formation of CuI is found to be E _a = 0.58 × 10² kJ/mol, and the preexponential factor in the Arrhenius equation is k ₀ = 7.43 × 10¹⁶ mol/(l s). The text was submitted by the authors in English.     

加油站油品用体积交接存在的问题及建议

叙述了目前加油站在实行按任意温度下的体积交接，由于未考虑油品体积随温度、压力、密度的变化，出现了零售损耗很大的问题。建议加油站在现阶段采用“准标准体积”交接；在由体积转换为质量计算加油站损溢时，使用油库当月发出的平均密度；当财会核销损溢时，不使用盘存的体积和固定密度进行计算的方法，而使用实际盘点的质量数，以真实反映加油站的当期损溢。     

应用于空间关联规则挖掘的ILP方法

文章介绍了应用于空间关联规则挖掘的ILP方法。ILP方法全称为归纳逻辑程序设计,这种方法有利于从空间领域发现有价值的知识,系统地研究地理层的层次结构,处理诸多空间对象的空间特性。这种方法已在一个ILP系统SPADA中实现,该文将通过SPADA应用空间数据的一些实例来说明ILP方法的特点。     

Improving Cost Estimates of Construction Projects Using Phased Cost Factors

Central to cost-based competition is the capability to accurately predict the cost of delivering a project. Most literature on cost estimation focuses on specific estimation methods as generic techniques and little attention has been paid to the unique requirements at each project stage. This note attempts to identify the critical factors for effective estimation at various stages of typical construction projects. Drawing from organization control theory and cost estimating literature, this note develops a theoretical framework that identifies the critical factors for effective cost estimation during each project phase of a conventional construction project. The underlying logic is that as a cost estimating effort progresses, both task programmability and output measurability improve. As a result, control effort will shift from input-oriented control to a combination of output and behavior control.     

A Critique of the ANSI Standard on Role-Based Access Control

In 2004, the American National Standards Institute approved the Role-Based Access Control standard to fulfill "a need among government and industry purchasers of information technology products for a consistent and uniform definition of role based access control (RBAC) features". Such uniform definitions give IT product vendors and customers a common and unambiguous terminology for RBAC features, which can lead to wider adoption of RBAC and increased productivity. However, the current ANSI RBAC Standard has several limitations, design flaws, and technical errors that, it unaddressed, could lead to confusions among IT product vendors and customers and to RBAC implementations with different semantics, thus defeating the standard's purpose.