Method to Characterize the Air Flow and Water Removal Characteristics During Vacuum Dewatering. Part II—Analysis and Characterization

This is part II of a study reported earlier on a method to characterize the air flow and water removal characteristics during vacuum dewatering. This article presents experimental data and analysis of results from the use of a cyclically actuated vacuum dewatering device for removing moisture from wetted porous materials such as paper with the intermittent application of vacuum and accompanying air flow though the material. Results presented include sheet moisture content as a function of residence time and hence water removal rate under a variety of process conditions. Also, experimental results on air flow through the wet porous structure and hence the role and importance of air flow during vacuum dewatering are presented. Vacuum dewatering process conditions include exit solids content between 11 and 20% solid under applied vacuum conditions of 13.5 to 67.7 kPa (4 to 20 in. Hg). Regression analysis indicated that the exit sheet moisture content exhibited a nonlinear relationship with residence time with exit solids reaching a plateau after a certain residence time. Final moisture content correlated linearly with the average overall flow rate of air through the paper sample and the basis weight of the material.     

重视过程控制工程安装材料的选择

本文结合工程介绍了自动化仪表工程设计中常用安装材料的正确选择方法和选择不当可能造成的危害。     

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.     

In Situ Performance Testing of Deteriorating Water Tanks for Durability Assessment

Reports of failure of existing concrete structures due to a lack of durability, rather than a deficiency in structural strength, has made concrete technologists, engineers, and researchers focus research on the parameters influencing durability performance with respect to time. Systematic performance monitoring, with respect to chosen durability parameters of existing concrete structures, will decide the direction of future research in this area. Inferences based on laboratory simulations and testing need to be confirmed by in situ field measurements and studies. In situ condition rating and performance monitoring surveys have been conducted by many researchers, scientists, and professional associations, and reported in literature. Inferences of few such studies are summarized and discussed. Deterioration of concrete structures constructed in recent times is observed at relatively faster rates, and has been mainly attributed to cracking. Cracking is associated with the use of faster-hydrating portland cements with increased fineness and the tricalcium silicate (C3S) content to support the high speed of modern construction. In the present research, a case study of deteriorated water tank structures situated in the semitropical region of India is presented. Some selected parameters—such as concrete cover, carbonation depth, chloride concentration, compressive strength, etc. which influence long term durability of structures—have been measured.     

定向爆破拆除框架式水塔

高 2 7m的水塔建于 193 4年 ,其顶部水罐由 12根钢筋混凝土柱支撑。在倒向侧 7根立柱上形成不同高度的爆破切口 ,背向侧倾倒中心线上的一根立柱上形成小爆破切口 ,其余 4根立柱底部打贯通孔 ,使水塔准确定向倾倒。文中讨论了立柱切口高度的计算 ,爆破参数的确定 ,并介绍了所采用的安全措施。     

焊接试样的焊缝外形尺寸对爆炸试验的影响

选用水面舰艇用９４５钢和潜艇用９２１Ａ钢，研究了不同焊缝外形尺寸对爆炸试验中三缺口试样的中央缺口开裂行为的影响。通过大量的试验数据，确定了开裂判据ｅ≤ｅ_ｍ，为试验前预示中央缺口开裂与否提供了可靠的依据。     

Catalytic oxidation of sulphide ions to elementary sulphur in aqueous solutions over transition metal oxides

The catalytic activity of a wide range of transition metal oxides in oxidation of sulphide ions by air in aqueous medium was studied. Some specific features of the reaction mechanism on some of the studied oxides were considered. The transition metal oxides are promising catalysts for practical application. Some of these oxides will allow the preparation of catalysts possessing activity comparable to that of the cobalt phthalocyanine based catalysts, popular in industrial practice.     

水溶性涂料使用性能研究

本文通过试验对水溶性涂料的耐盐雾腐蚀性能，耐热性能，高低温冲击性能，耐油性能，涂膜与铁基体，面漆的给合力及涂膜表面电阻进行研究，同时指出了该涂料在军用电子产品上的应用前景。     

CDB含水率计产生非一致性响应的原因及改进

郭海敏.CDB 含水率计产生非一致性响应的原因及改进.测井技术,1993;17(2):154～160用微波传输线理论,简化 CDB 含水率计为集总参数电路。导出了这种含水率计的响应方程,给出了油气水混合电导率与持水率的非线性关系式,在此基础上认为这种含水率计的响应曲线呈 S型。导致响应出现非一致性现象的主要因素有:工作频率低,不能有效地消除地层水矿化度的影响;仪器外壁侧孔使信号向外辐射造成损耗;仪器与其它仪器相连,此时含水率计呈非纯容性。我们认为这些因素的影响使得 CDB 含水率计与传统的电容法含水率计在实质上没有明显差别。要消除非一致性现象,应从以上几点进行改进。