S7-226PLC与MM440变频器在光缆护套机中的应用

本文介绍了由西门子S7—226PLC与MM440变频器组成的电气控制系统在光缆护套机速度控制中的应用。并对该系统的控制原理作了详细的阐述。     

天铁炼钢厂四流中间包流场的水模实验及优化

介绍了天铁炼钢厂中间包水模实验原理和过程，分析了斜、直、圆三种型式挡渣墙模拟结果，提出了合理的挡渣控流方案，在生产实践中使用效果良好。     

Synthesis of selenium nanoparticles in the presence of silk fibroin

This paper describes a solution-phase approach to the synthesis of selenium nanoparticles by reducing selenious acid solution with ascorbic acid in the presence of silk fibroin. The monodispersed spherical selenium colloid particles obtained were very stable in silk fibroin solution and characterized by Atomic force microscopy and X-ray techniques. The influences of temperature and ultrasonication on the morphology of selenium nanoparticles were also discussed. The experiments showed that the selenium nanoparticles with various morphologies could be obtained under different temperatures and the appropriate ultrasonication time was 60 min. This result indicated that the silk fibroin molecules intimately associated with the surface of the selenium particles and controlled the growth particles.     

印品质量控制中的密度测量与色度测量

在印刷品质量控制中为了得到更多的可靠数值,越来越多地选择用仪器测量法来代替主观评价法.这就是密度测量法和色度测量法.     

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.     

Developing Cost Response Models for Company-Level Cost Flow Forecasting of Project-Based Corporations

The difficulty in applying the standard curve (S-curve) and cost-schedule integration (CSI) techniques for company-level cost flow forecasting in a project-based industry is the prerequisite of forecasting future unknown individual projects and contract classifications. By analyzing cost flows at the company level through a pool of macroeconomic and internal financial data, this paper proposes an innovative approach to firm-specific model estimation. First, a series of data transformations introduce linear relationships between cost, macroeconomic, and internal financial variables. Second, multivariate regression analysis is employed for initial model building. Third, for the purposes of model restructuring, a subsequent application of Yule–Walker estimates and incomplete principal component analysis is used. This paper uses a sample of four project-based construction firms to demonstrate model performance. Using this methodology, mean absolute percentage error (MAPE) values of the forecasting models range from 0.27 to 0.60%. As such, the transformed cost, macroeconomic, internal financial data could strongly predict company-level cost flow forecasting. While converting the predicted cumulative cost data to periodic cost flows, the MAPE values were augmented, ranging from 7.04 to 17.55%, thus, requiring future research.     

电梯门机控制系统的运行曲线设计

为了实现电梯轿厢门的开门和关门快速且平稳地运行，介绍了一种基于高性能微型机的门机控制系统结构和门位移的检测原理，以门位移量作为控制系统的反馈量，对门机运行速度进行了分区设计。在高速附近的变化区，门机速度匀速变化时，进行了门机开门和关门控制曲线的计算，推导出运行位移与门机速度具有二次曲线的关系，进而对微型机控制的软件流程进行了设计，达到了门机高低速运行的平稳过渡。最后，给出了实际运行系统的主电路电压波形。     

激光平网雕刻机设计

研制了用于制作平面网版的激光雕刻机，设计了雕刻机用CO2激光器、光路系统及单片机控制系统，探讨了将图像文件转化为控制命令文件的方法。     

承钢棒材连轧线计算机控制系统

主要介绍了承钢棒材连轧线计算机控制系统，其中包括了系统的硬件配置，控制功能及控制说明。     

实时多任务操作系统响应性能预估和测试

本文给出了作者开发的一个单处理机实时多任务操作系统的响应性能（响应时间，同步时间）的实验结果和／或估算。与国外同期文献发表的数据相比，指标先进。