A mathematical model for internal oxidation

A mathematical model for internal oxidation kinetics was developed using numerical methods (finite difference) and computer techniques. The flexibility of the model permitted analysis of semi-infinite and finite situations with planar, cylindrical, and spherical geometries for systems with various amounts of local solute enrichment. Graphical results are presented for subscale thickness as a function of time and local enrichment as a function of position in the subscale. The model is also applied to internal oxidation with a discontinuous change in surface oxygen concentration; a graphical solution encompassing a wide range of possible experimental conditions is presented. The use of the model in analyzing nonisothermal internal oxidation problems is demonstrated.     

An expert system methodology for aircraft-gate assignment

The aircraft-gate assignment problem is a significant concern in airline operations. This paper addresses the use of knowledge based expert systems to help solve the aircraft-gate assignment problem. The problem is described and the factors that need to be considered in aircraft-gate assignment are identified and delineated. The expert system's architecture is presented and its working is described.     

Flexural capacity of thin wall fibre reinforced cement

A method of calculating the flexural strength (cracking) of fibre reinforced cement floor and wall systems is presented. The method for flexural strength is based on non-linear stress-strain relationship at failure tension and corresponding stress distribution in section at cracking and subsequent failure. The method is verified in tests of full-scale ‘V’ and ‘U’ shaped panels made of asbestos-cement which were tested as simply supported beams designed for the construction of low cost housing and wall facades. Additional tests were performed on small sized samples to verify the mechanical properties of material used.     

Forecasting compensatory control (FCC) of machining flatness

Forecasting Compensatory Control (FCC) was implemented to improve the flatness of three dimensional prismatic workpieces in an end-milling operation. The basic logic of the strategy is based on inprocess error measurement, stochastic modelling, and prediction and compensation of the cutting errors.The proposed FCC system consisted of a newly developed laser-based in-process flatness error measurement system, a hydraulic positioning servo system, and a digital microcomputer control system. Through the application of the FCC system to on-line cutting experiments, the workpiece flatness error was reduced by up to 80% during machining.     

Solar radiation estimates from common parameters

In tropical countries, precipitable water, W, is not a good basis for predicting solar radiation because of the narrow range of fluctuation in this parameter. Relative humidity, however, does fluctuate over a larger range and has been used in this study. The following empirical relationships between solar-radiation intensity, H, ratio of hours of bright sunshine to twelve hours, S, and relative humidity of the environment, R, have been obtained by statistical methods applied to the available data.^*

H=490S^0.357R^−0.262

H=460e^0.607(S−R)

H=464+265S−248R

These equations give better estimates of solar-radiation intensity than the single-parameter relationship like

H=a+bS

Charts have been constructed from the empirical relations to simplify the use of the expressions.     

Automated patent searching: Preliminary results of USPTO studies

The United States Patent and Trademark Office has begun development of a ‘paperless’ automated system to replace its paper search files. In order to answer several questions related to automated operation, the US Office conducted a number of studies involving commercial patent search systems. The results of these studies are summarized in this paper.     

Wet air regeneration of PAC: Comparison of carbons with different surface oxygen characteristics

Surface oxygen has an important effect on the wet air regeneration (WAR) of powdered activated carbons (PAC) and on the adsorption properties of the regenerated PAC. Virgin and phenanthrene-loaded PACs were regenerated in a bench-scale reactor, and then analyzed to determine surface oxygen content, adsorption capacity, and extent of phenanthrene oxidation.Even though the virgin wood-base (WB) and lignite-base (LB) PACs had about the same oxygen content, the oxygen content of the WB PAC increased more than twice as much as the LB PAC during regeneration. The difference was caused by the larger amount of CO₂-evolving oxides that formed on the WB PAC. WAR reduces the capacity of PAC for p-nitrophenol (PNP). Removing the surface oxides had varying effects on the carbon's capacity for PNP. Also, adsorbed phenanthrene was more easily oxidized on the WB PAC than on the LB PAC during regeneration.     

KINETICS OF REACTION BETWEEN Cu_2S AND Cu_2O

Reaction between Cu_2S and Cu_2O was investigated at 1150 to 1250℃.The reaction rate in-creases with the increase of surface area of Cu_2O grains and depends unobviously on temper-ature.At the suggestion of controlling step of reaction rate being oxygen diffusion through theliquid layer along reaction boundaries,two final kinetical equations would be made as follows:x=6.69×10~(-2)At for 0<α<0.74 and ln(l-α)=-A(9.83×10~(-2)t+1.76)for 0.74<α<1,whereα is SO_2 evolved in time t and A is surface area of Cu_2O particles.     

信息边界安全及我国的对策

进入９０年代以来,信息安全已居为各国十分重视的国家安全问题。本文作者在“信息安全”的基础上率先提出了“信息边界安全”的全新概念,并对信息边界最易受攻击 的“主要区段”以及我国应采取的对策作了介绍。     

南京ATM宽带多媒体网络的建设

ＡＴＭ技术在经济ＩＴＵ－Ｔ和ＡＴＭ论坛多年的研究与论证后,已开始在多个领域得到广泛运用。本文介绍了南京市ＡＴＭ的网络的建设情况,包括基本组成、网络业务及网络的测试等。