Prediction techniques

UNIQUAC is significant because it provides a means to estimate multicomponent interactions using no more than binary interaction experimental data, bond angles, and bond distances. There is an implicit assumption that the combinatorial portion of the model, ie, the size and shape effects, can be averaged over a molecule and that these can be directly related to molecular surface area and volume. This assumption can be found in many QSAR methods and probably makes a significant contribution to the generally low accuracy of many QSAR prediction techniques. 

The design of this alloy was unique in that it utilized phase stability and other predictive techniques to balance the levels of critical elements (Cr, Mo, Co, Al, Wand Ta), thereby maintaining the hot corrosion resistance of IN-738 at higher strength levels without compromising phase stability. Most... 

Heselberg, P., S. Murakami, and C.-A. Roulet. 1996. Annex 26 Air flow patterns m large enclosures. In Ventilation of Large Spaces in Buildings. Part 3 Analysis and Prediction Techniques. LEA,... 

The most common predictive technique which is used to analyze facilities which contain new equipment or processes, or where there is an unusually high risk to personnel or the environment is the Hazard and Operability technique or HAZOP. A HAZOP study requires a team of five to ten multi-discipline personnel consisting of representatives from engineering, operations, and health, safety, and environmental staff. The... 

Prediction of specific errors and their consequences by using task analysis and error prediction techniques (Chapters 4 and 5)... 

Shah, M. M., A General Predictive Technique for Heat Transfer During Saturated Film Boiling in Tubes, Heat Trans. Eng, V. 2, Oct.-Dec. (1980) p. 51. 

Even with the predictive techniques discussed, many potentially serious problems can remain undetected. Routine visual inspection of all critical plant systems will augment the other techniques and insure that potential problems are detected before serious damage can occur. 

We are pleased to acknowledge our indebtedness to colleagues P. J. Baldock and A. Parker for the x-ray crystallographic studies, to P. Snowden who devised the life prediction technique, and to Imperial Chemical Industries Ltd. for permission to publish this paper. 

In the area of predictive toxicology the applicability domain is taken to express the scope and limitations of a model, that is, the range of chemical structures for which the model is considered to be applicable [106]. Although this issue has been fundamental to the use of QSAR (and indeed any predictive technique) since its conception, there remain few reliable methods to define and apply an applicability domain in predictive toxicology. The current status of methods to define the applicability domain for use in (Q)SAR has been assessed recently by Netzeva et al. [106]. 

Partial Least Squares (PLS) regression (Section 35.7) is one of the more recent advances in QSAR which has led to the now widely accepted method of Comparative Molecular Field Analysis (CoMFA). This method makes use of local physicochemical properties such as charge, potential and steric fields that can be determined on a three-dimensional grid that is laid over the chemical stmctures. The determination of steric conformation, by means of X-ray crystallography or NMR spectroscopy, and the quantum mechanical calculation of charge and potential fields are now performed routinely on medium-sized molecules [10]. Modem optimization and prediction techniques such as neural networks (Chapter 44) also have found their way into QSAR. 

There are many types of phase diagrams in addition to the two cases presented here these are summarized in detail by Zief and Wilcox (op. cit., p. 21). Solid-liquid phase equilibria must be determined experimentally for most binary and multicomponent systems. Predictive methods are based mostly on ideal phase behavior and have limited accuracy near eutectics. A predictive technique based on extracting liquid-phase activity coefficients from vapor-liquid equilibria that is useful for estimating nonideal binary or multicomponent solid-liquid phase behavior has been reported by Muir (Pap. 71f, 73d ann. meet., AIChE, Chicago, 1980). 

Farrest, C. F., W. T. Hancox, and W. B. Nicoll, 1971, Axial Void Distributions, in Forced Convection Boiling A Survey of Prediction Techniques and Their Efficiency, Int. J. Heat Mass Transfer 14 1 377-1394. (3)... 

Atkinson, R., Aschmann, S.M., Winer, A.M., Pitts, Jr., J.N. (1985) Atmospheric gas phase loss processes for chlorobenzene, benzotrifluoride and 4-chlorobenzotrifluoride, and generalization of predictive techniques for atmospheric lifetimes of aromatic compounds. Environ. Contam. Toxicol. 14, 417-425. 

There is, as always, a need for good quality data. Most of this is now available in electronic form and Chapter 11 lists some of the databases available. In spite of proclaimed good intentions, there is little systematic documentation of the successful application of plastics and their lifetimes, only examples of unexpected failure. There is a need for medium-term, lightly accelerated tests under intermediate conditions to validate the predictive models. While inspection of components at end-of-life is more prevalent than expected, there is a need for coupling it to predictive techniques to validate these techniques and to close the loop of life prediction. 

---