Discounting Systemic Factors

The problem with event chain models is not simply that the selection of the events to include and the labeling of some of them as causes are arbitrary or that the selection of which conditions to include is also arbitrary and usually incomplete. Even more important is that viewing accidents as chains of events and conditions may limit understanding and learning from the loss and omit causal factors that cannot be included in an event chain. 

Event chains developed to explain an accident usually concentrate on the proximate events immediately preceding the loss. But the foundation for an accident is often laid years before. One event simply triggers the loss, but if that event had not happened, another one would have led to a loss. The Bhopal disaster provides a 

The release of methyl isocyanate (MIC) from the Union Carbide chemical plant in Bhopal, India, in December 1984 has been called the worst industrial accident in history Conservative estimates point to 2,000 fatalities, 10,000 permanent disabilities (including blindness), and 200,000 injuries [38]. The Indian government blamed the accident on human error—the improper cleaning of a pipe at the plant. A relatively new worker was assigned to wash out some pipes and filters, which were clogged. MIC produces large amounts of heat when in contact with water, and the worker properly closed the valves to isolate the MIC tanks from the pipes and filters being washed. Nobody, however, inserted a required safety disk (called a slip blind) to back up the valves in case they leaked [12]. 

A chain of events describing the accident mechanism for Bhopal might include  

E1 Worker washes pipes without inserting a slip blind. 

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Pick-up of stray current (a.c. or d.c.) (Section 10.5). Decreased use of d.c. in many areas has led to less possibilities of pick-up of direct current from utilities, mines, etc. The importance of grounded a.c. systems has been discounted, but Waters has shown that alternating currents can accelerate corrosion. Furthermore the rectifying effects of oxide films, clay minerals and other soil factors are not understood. 

The Net Present Value (NPV) of a capital investment is the equivalent total cash flow generated by all the acquisition s benefits less all the acquisition s costs computed over the life of the system on a year to year basis, adjusted for the value of money as reflected by such factors as finance rates, and projected ("discounted") to the present day. A dollar benefit projected for the system next year would only be worth 0.91 today if that dollar could be earning 10% interest. A net present value of zero means that the acquisition will, over its projected life, just break even and that it is therefore an acceptable purchase. A better than zero NPV would be a high priority purchase since it indicates a real profit. 

The Internal Rate of Return (IRR) is the equivalent interest rate at which the Net Present Value of the acquisition would be zero. Given the projected total cost of the system, and the projected total benefits of the system, both projected back (discounted) to today, it is the interest rate that the investment could sustain and still just break even. Since firms, in general, operate at a point where their incremental cost of money is equal to its incremental earning power, any investment that returns an IRR better than the cost of money is a good investment. Traditionally, the IRR is found by calculating the NPV with different interest factors in a trial and error method until the interest factor is found which drives the NPV to approximately zero. 

Hence, such atoms need to be discounted in their contribution to A S1, conformatjonal and this is done by applying a factor of 0.5 times the number of such sp2 members of a chain. This discounting also applies to ring systems. Hence, we can estimate a parameter, r ... 

Corrosion economics and corrosion management forms the theme of the fifth chapter. Discounted cash flow calculations, depreciation, the declining balance method, double declining method, modified accelerated cost recovery system and present worth calculation procedures are given, together with examples. In the second part, corrosion management, including the people factor in corrosion failure is briefly presented. Some of the expert systems presently available in the literature are briefly discussed. 

The sensitivity results reported in Table 5 for FF production price are as follows. A 0.01/kWh increase in electricity cost causes FF production price to increase by 0.55/kg. A 25 increase in electrolyser cost ( /kWdc-m) causes FF production price to increase by 0.04/kg. A 1% increase in electrolyser capacity factor causes FF production price to decrease by 0.02/kg. A 1% increase in electrolyser efficiency (LHV) causes FF production price to decrease by 0.04/kg. A 1% increase in electrolysis plant O M expenses, which includes water system and compressors, causes FF production price to increase by 0.09/kg. A 1% increase in the discount rate causes FF production price to increase by 0.09/kg. To evaluate the effect of a decrease in cost factor values simply reverse the sign, positive or negative, for the change in FF production price. 

Data from animal studies ideally should provide clear evidence of specific reproductive toxicity in the absence of other, systemic, toxic effects. However, if developmental toxicity occurs together with other toxic effects in the dam, the potential influence of the generalized adverse effects should be assessed to the extent possible. The preferred approach is to consider adverse effects in the embryo/foetus first, and then evaluate maternal toxicity, along with any other factors, which are likely to have influenced these effects, as part of the weight of evidence. In general, developmental effects that are observed at maternally toxic doses should not be automatically discounted. Discounting developmental effects that are observed at maternally toxic doses can only be done on a case-by-case basis when a causal relationship is established or refuted. 

An expert system planned for Risk Assistant addresses the probability that various exposure pathways will be of concern at a hazardous waste site. This module guides users in considering factors that may increase or decrease the likelihood that a chemical will be released from a unit such as a landfill or surface impoundment to any environmental media. If release cannot be ruled out, factors affecting transport to an area of potential exposure are considered. If the presence of contamination in an area of potential exposure cannot be discounted, potential exposure scenarios are reviewed. The end result is a listing of potential exposure pathways that the user may have to consider for the site. 

The products of each system were costed using two different techniques the equality method and the by-product work method (1, 2 ). Every case analyzed accounts for maintenance as well as fuel expenses but excludes other operating costs. Capital investment is amortized at an after-tax discount rate of 8.5%. The effects of income taxes, ad valorem taxes, and depreciation (see (3) for the formulation of the annualization factor accounting for capital, taxes and depreciation) are included, while the effects of inflation were neglected. 

When the liquid has foaming tendencies, additional residence time must be allowed for phase disengagement. System discount factors, recommended by Koch-Glitsch, Inc. on the basis of field experience, are shown in Table 12.7. As an example, the maximum allowable velocity of 0.1 m/s would be multiplied by the discount factor so as to provide adequate downcomer volume. 

Thermal decomposition is not considered in this scheme. Indeed, assuming the activation energy Ea for the C-I bond decomposition to be equal to the 2.6 eV bond energy (i.e., no activation barrier assumed) and a rather high preexponential factor of 1013 s 1, the yield by thermal decomposition is estimated to be only 10-6 on a time scale of fis and 10-3 on ms time scales. The possibility of thermal decomposition is further discounted by the failure to detect any NapH-like photoproduct formation in the ablation of Napl/Rd/ PMMA (0.4% and 0.1% by wt., respectively Rd represents rhodamine 6G) at 532 nm. Nevertheless, it is reasonable to assume that comparable temperatures develop in the ablation of this system as in the 248-nm irradiation of NapI/PMMA. Therefore, thermal decomposition fails to account for the aromatic dopant decomposition. 

TABLE 5.7-3 Downflow Capacity Discount Factors, Foaming Systems... 

We cannot discount altogether the patient-specific prognostic factors outhned in the staging systems described in Table 104.1. For reasons that are not completely understood, both the age and sex of the patient at diagnosis influence disease behavior and the outcome of initial therapies. 

Farrah and Pickering (1977), however, discount inorganic jarticulate sorption of mercury as being a najor factor in the transport and redistribution of mercury in natural water systems and suggested tla.t precipitation/dissolution processes, rather than sorption, are the dominating factors in mercury water-sediment partitioning. 

Estimates of working capital requirements fall Into four cireas inventories, accounts receivable, cash in hand, and current liabilities. To estimate these, it is necessary to consider the different production stages in which materials can be found, wdiich are (1) raw materials paid for but not received (a portion of current assets) (2) raw materials on hand but not paid for (a portion of current liabilities) (3) materials in process (4) finished products in store whether on-site orpff-site and (5) finished prod-ucts delivered to customers but not yet paid for (accounts receivable). The calculation of the amounts of each of these material inventories depends on such factors as distance from raw material suppliers, types of contracts for raw material purchases, raw material purchase fh nancing methods, quantity discounts and lot sizes available for raw materials, available modes of transportSition, cost of storage facilities, plant size and capacity, seasonality of sales volumes, marketing system, and customer credit policies. 

We have very little idea about the stoichiometry of the two major polysomal mRNP proteins, or their location on the mRNA, apart from the fact that the 8,000 dalton protein seems to be associated with the poly A tract at the 5 end (59) The function of the proteins is even more obscure. In cell-free translation assays the activity of polysomal mRNP is no greater than that of deproteinised mRNA (20). This result is open to the qualification that in crude cell-free systems the added deproteinised mRNA mi t pick up proteins from the cell-free extract and thereby be effectively converted into polysomal mRNP particles, but since the same result is obtained in highly fractionated systems (11) this reservation can probably be discounted. The major polysomal mRNP proteins are distinct from all seven recognised initiation factors (ll), and initiation complex formation is found to require the same set of seven factors regardless of whether polysomal mRNP or deproteinised mRNA is used (11). In short, there is no evidence that these proteins play a role in mRNA translation. 

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