Reason Model revision

A South African group also began calculations with Boyd s pro-gram. They got it in Snow s version, and applied it to stability differences between complexes of Ni(II) with five- and six-membered chelate rlngs and other thermodynamic calculations We have earlier commented on the three first papers, and there seems no reason to revise our remarks that the method leaves out the majority of the non-bonded interactions (for which there is no excuse in 1978 and later), that the minimisation criterion is very liberal, that calculated energies are compared with measured enthalpies with no account of the internal motion. Altogether, their method has no interest as a modelling tool. 

This is a further deepened work of what Samsung Total accomplished[12-14] several years ago. Several operation conditions including hardware modification which may enhance the productivity were deduced and simulated using the simulation model. Some ideas wctb alre y applied to commercial plant when they were concluded practically reasonable while some are on the waiting list One of the examples of productivity enhancement is shown in Fig. 1 and Fig. 2 which compare the conversion profiles and MWDs under original and revised operation conditions. As shown in these two figures the productivity was mhanced while MWD docs not change much. 

This model is based on Sw data spanning 5 log units. Nirmalakhandan and Speece [36,37] discuss the model s validity and robustness in detail. They performed a test using experimental Sw data for esters, ethers, and aldehydes that were not included in the training set. They noted reasonably good agreement between experimental and estimated data for the test set and indicated that eq. 11.5.4 is applicable to dialkyl ethers, alkanals, and alkyl alkanoates, but not for ketones, amines, PAHs, and PCBs. Nirmalakhandan and Speece [37] expanded the model above for the PAHs, PCBs, and PCDDs. However, their model has been criticized by Yalkowsky and Mishra for incorrect and omitted data [38]. The revised model is [38]... 

Given that this revised calibration scheme together with the correction of the weighted mean calculation are nearly identical (< 150 m difference) to the previous model results all of the comparisons of the modern isotopic compositions of precipitation from other regions are effectively unchanged and hence these comparisons demonstrates that the model yields quite reasonable fits without adjustment (see Rowley et al. 2001 and Rowley and Garzione 2007). However it should always be made clear that the empirical scheme to model precipitation from condensate does not represent the microphysics of water droplet formation, coalescence,... 

It is rather essential that the applicability domain of a derived model can be evaluated so that outliers to the model may be indicated. If an established statistical model is to be regarded as poor from a predictive point of view this should be done on the basis of correct reasons, that is, that the model has truly poor predictive ability and not from the fact that the model cannot estimate outliers to the model with acceptable accuracy. The latter case is probably the most common cause for statistical (ADMET) models to fall from fame especially those that can be accessed through internal or external web services. In many cases it is difficult, if not impossible, to find out about the compounds used as training set and/or the chemical description used in the model. Thus, many compounds outside the applicability domain of the model will be submitted. It is therefore of great importance to have an indication together with the prediction whether the compound is considered to fall inside or outside of this domain, that is, if the compound is an outlier or not. The outlier information, and possibly also how far from the model the compound in question is, may in many cases be utilized in a more proactive way than just realizing that a number of compounds submitted to the model for prediction are, in fact, outliers to the present model. Thus, by analyzing the outliers, perhaps virtual compounds, from various points of views, for example, structural or synthetic, some of these compounds may later be synthesized and tested experimentally. The same compounds may then be incorporated into a revised model that will have a broader applicability domain. There are different methods available to determine whether a particular compound is to be labeled as an outlier. In this section, we will describe two of these methods ... 

A difficulty with the Al-Hayes and Winterton model is that the values of <(>, 0, and < >r need to be known. For a number of boiling experiments, measurements are reported of < ), and Winterton [67] shows that reasonable results could be obtained by assuming that <(> = 0 +10° and (j)r = (j) -10°. Kandlikar and Stumm [374] showed that the Al-Hayes and Winterton model gave excellent results for bubble diameters greater than 800/xm but that large discrepancies were observed for smaller bubbles Kandlikar and Stumm suggest a revised model for this region. 

Rehability of final data depends, first, on the correct selection of thermodynamic and chemical laws and their use in hydrogeochemical mathematical models, and second, on the selecting means of its solving and reliability of utilized values. For this reason at the evaluation of final result quality by means of software programs are identified two levels of revision validation and verification. They have the same objective but differ in properties, rules and restrictions. Their violation is considered an error. 

Such a task description invites task analysis, which would lead naturally to human reliability analysis (HRA). Indeed, perhaps the earliest work in this field applied HRA techniques to construct fault trees for aircraft structural inspection (Lock and Strutt 1985). The HRA tradition lists task steps, such as expanded versions of the generic functions above, lists possible errors for each step, then compiles performance shaping factors for each error. Such an approach was tried early in the FAA s human factors initiative (Drury et al. 1990) but was ultimately seen as difficult to use because of the sheer number of possible errors and PSFs. It is occasionally revised, such as in the current FRANCIE project (Haney 1999), using a much expanded framework that incorporates inspection as one of a number of possible maintenance tasks. Other attempts have been made to apply some of the richer human error models (e.g.. Reason 1990 Hollnagel 1997 Rouse 1985) to inspection activities (La-toreUa and Drury 1992 Prabhu and Drury 1992 Latorella and Prabhu 2000) to inspection tasks. These have given a broader understanding of the possible errors but have not helped better define the PoD curve needed to ensure continuing airworthiness of the civil air fleet. 

---