Variable default value

Second card FORMAT(8F10.2), control variables for the regression. This program uses a Newton-Raphson type iteration which is susceptible to convergence problems with poor initial parameter estimates. Therefore, several features are implemented which help control oscillations, prevent divergence, and determine when convergence has been achieved. These features are controlled by the parameters on this card. The default values are the result of considerable experience and are adequate for the majority of situations. However, convergence may be enhanced in some cases with user supplied values. 

The following variables are given default values if the user does not explicitly define them ... 

A specification of the NLP problem to be solved—at a minimum, the number of functions, the number of variables, which function is the optimization objective, bounds on the functions and variables (if different from some default scheme), and initial values of some or all variables (the system may supply default values, but using these is recommended only as a last resort). 

Chapter 5 of the document reviews the UFs used by UK Government departments, agencies, and their advisory committees in human health risk assessment. Default values for UFs are provided in Table 3 in the UK document with the factors separated into four classes (1) animal-to-human factor, (2) human variability factor, (3) quality or quantity of data factor, and (4) severity of effect factor. The following chemical sectors are addressed food additives and contaminants, pesticides and biocides, air pollutants, drinking water contaminants, soil contaminants, consumer products and cosmetics, veterinary products, human medicines, medical devices, and industrial chemicals. 

Dourson et al. (1996) considered that, in general, the default value of 10 for interindividual variability appears to be protective when starting from a median response, or by inference, from a NOAEL assumed to be from an average group of humans. When NOAELs are available in a known sensitive human subpopulation, or if human toxicokinetics or toxicodynamics are known with some certainty, this default value of 10 should be adjusted or replaced accordingly. 

In conclusion, the data and analyses performed by Renwick and Lazarus indicate that the 10-fold factor for human variability is an appropriate default value, but it has also identified a number of circumstances where this default value may be inadequate. For example, the 3.16 toxicokinetic factor could not cover human variability in the case of genetic polymorphisms. 

The ITL4 variable controls how many times the step size can be reduced during a simulation. The default value is 10, so after the step size has been reduced 10 times the simulation will stop. If the value of the option is not set to 100 then change the value to 100. 

The variable nrjuutants determines the size of the sample population, 1000 is the default value. 

The value of deadtime is set by clicking on the icon, clicking the right mouse button, and selecting Forms and All Variables. The window shown at the top of Figure 3.75 opens, which shows some default values for input and output. Make an initialization run to get the correct values, as shown in at the bottom of Figure 3.75. The deadtime value has also been inserted. Figure 3.76 shows the flowsheet and faceplate with the temperature and level controllers installed. 

LOAEL where a NOAEL is not available, and database deficiencies. Lack of reproductive and developmental toxicity data is often used as a basis for including a database uncertainty factor. The default value for any one uncertainty factor is 10, but this may be reduced depending on the confidence in the data or information that provides assurance of reduced intra- or interspecies variability (Renwick et al., 2000). As noted above, chemical-specific data on toxicokinetics and toxicodynamics may be used to replace part or all of these uncertainty factors, and this strategy has been used by WHO/IPCS (IPCS, 1994, 2004b, 2005). 

The NOAEL or benchmark dose/concentration is selected, then, generally to be at or below the threshold in animals uncertainty factors are then applied to estimate the subthreshold in sensitive human populations, with a 10-fold default factor addressing interspecies differences (i.e. the variation in response between animals and a representative healthy human population) and another 10-fold factor accounting for interindividual variability in humans (the variation in response between a representative healthy human population and sensitive subgroups). While additional factors are sometimes applied to account for deficiencies of the database, the 100-fold default value is common. 

Using default values, the selected range of the influencing variables must be chosen well, as the complaint of any particular person that You have not considered that for me/my family the exposure (this influence factor) is higher than the one that you have used might devalue the whole exposure assessment in a public debate. Furthermore, in the authors experience, it is much better to use distributions for the influence factors. Considering combinations of distributions for the input variables might lead to answers like We have considered... 

The FCC simulator also requires a description of the unit and its operation in terms of equipment dimensions and constraints, operating variables and unit parameters. Standard or default values for all of these are stored in the preprocessor database. The user, however, can change the values of any of the following in specifying the base and alternate FCC operations ... 

In general, calculations of industrial emissions rely on default values according to the industrial sector, emission rates, wind velocity and direction, anticipated substance flows through the environment, abatement technologies and wastewater treatment processes (see [114]). Site-specific assessments and local environmental exposure assessments must also account for geographic variability caused by climate, hydrology, geology, and biotic conditions [115]. 

Table 10.6 Variability in default values for protection factors used in Canada, Germany, UK, USA and California...

Default factor, user mav change User variables Calculated values, million ... 

Since we did not perform Le Bail s decomposition of this powder diffraction pattern, we will illustrate the Rietveld refinement sequence in this case beginning from all profile parameters selected at their default values and the same starting model of the crystal structure as was used in the case of Cu Ka radiation data. The input file, ChTExOlg.inp, with initial variables and the experimental data file, Ch7Ex01 MoKa.dat, are found on the CD. The progression of the refinement is shown in Table 7.5. 

The initial process in the application of toxicity (dose-response) data in risk assessment is the extrapolation of findings to establish acceptable levels (AL) of human exposure. These levels may be reference values (inhalation reference concentrations, RfC or oral reference doses, RfD), minimal risk levels (MRL) values, occupational exposure limits, and so on. When the toxicity data are derived from animals, the lowest dose representing the NOAEL (preferably) or the LOAEL defines the point of departure (POD). In setting human RfD, RfC, or MRL values, the POD requires several extrapolations (see [13] and revisions). Extrapolations are often made for interspecies differences, intraspecies variability, duration of exposure, and effect level. Each area is generally addressed by applying a respective uncertainty factor having a default value of 10 their multiplicative value is called the composite uncertainty factor (UF). The UF is mathematically combined with the dose at the POD to determine the reference value ... 

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