Environmental assumptions

Level 1 is the customer view and assists system engineers and customers in agreeing on what should be buUt and, later, whether that has been accomplished. It includes goals, high-level requirements and constraints (both physical and operator), environmental assumptions, definitions of accidents, hazard information, and system limitations. 

Dependability cases are provided by manufacturers and operating companies. They usually comprise large, complex argument structures on the development process, on system properties and environmental assumptions, and on operating procedures with multiple interdependencies and references to external documents... 

Contrary to proponents assumptions, natural dyes are not necessarily environmentally friendly. First, large amounts of plant waste would be produced because of the low dye content in plants, eg, 170 million t of waste to color the cotton volume. Also, in order to dye fabric with natural dyes, "mordants," which are usually based on heavy metals, have to be used. For example, madder is appHed with tin (Sn) or aluminum (Al). Weld is appHed with tin salts. Salts based on copper and iron can also be used. 

It also specifies data requirements, assumptions, limitations, eventual type of critical review, and the report requirements. For example, a study could be done to select between one of two materials when developing a dust transport container for a baghouse filter. The intended audience may be the designers, the results being used to indicate which one of the two materials provides the lowest environmental impact. The system function may be to transport dust from the baghouse filter to a landfill site, and the functional unit may be one metric ton or m of dust. The system boundaries may be described by considering which processes are included and which are outside the system limits. 

Most human or environmental healtli hazards can be evaluated by dissecting tlie analysis into four parts liazard identification, dose-response assessment or hazard assessment, exposure assessment, and risk characterization. For some perceived healtli liazards, tlie risk assessment might stop with tlie first step, liazard identification, if no adverse effect is identified or if an agency elects to take regulatory action witliout furtlier analysis. Regarding liazard identification, a hazard is defined as a toxic agent or a set of conditions that luis the potential to cause adverse effects to hmnan health or tlie environment. Healtli hazard identification involves an evaluation of various forms of information in order to identify the different liaz.ards. Dose-response or toxicity assessment is required in an overall assessment responses/cffects can vary widely since all chemicals and contaminants vary in their capacity to cause adverse effects. This step frequently requires that assumptions be made to relate... 

Designers of most structures specify material stresses and strains well within the pro-portional/elastic limit. Where required (with no or limited experience on a particular type product materialwise and/or process-wise) this practice builds in a margin of safety to accommodate the effects of improper material processing conditions and/or unforeseen loads and environmental factors. This practice also allows the designer to use design equations based on the assumptions of small deformation and purely elastic material behavior. Other properties derived from stress-strain data that are used include modulus of elasticity and tensile strength. 

The overall set of partial differential equations that can be considered as a mathematical characterization of the processing system of gas-liquid dispersions should include such environmental parameters as composition, temperature, and velocity, in addition to the equations of bubble-size and residence-time distributions that describe the dependence of bubble nucleation and growth on the bubble environmental factors. A simultaneous solution of this set of differential equations with the appropriate initial and boundary conditions is needed to evaluate the behavior of the system. Subject to the Curie principle, this set of equations should include the possibilities of coupling effects among the various fluxes involved. In dispersions, the possibilities of couplings between fluxes that differ from each other by an odd tensorial rank exist. (An example is the coupling effect between diffusion of surfactants and the hydrodynamics of bubble velocity as treated in Section III.) As yet no analytical solution of the complete set of equations has been found because of the mathematical difficulties involved. To simplify matters, the pertinent transfer equation is usually solved independently, with some simplifying assumptions. 

Departures from ideality have been studied extensively for gases and gas mixtures. For most conditions of interest in the Earth s atmosphere, the assumption of ideal behavior is a reasonable approximation. The two most prevalent gases (N2 and O2) are non-polar and have critical temperatures (126 K and 154 K) far below most temperatures of environmental interest. These gases behave fairly ideally even though their pressures are high. For other gases, the partial pressures common in the atmosphere are so low that ideal behavior is a good approximation. 

In making the reasonable assumption that browser diets should have remained consistent through time, it was also assumed that C7 C ratios of their C3 foliage diets would not have changed. This is not the case environmental parameters such as aridity, osmotic stress, temperature, pCOi and irra-diance have predictable effects on ratios of C3 plants (summarized in... 

All these assumptions can make a significant difference to the outcome of the study, and perhaps not surprisingly, assumptions made by organizations with a vested interest tended to support their product. Perhaps the overall conclusion from these studies is that the difference in overall impact is relatively small. How these products are used in practice may in fact be the most significant determinant of their relative environmental impact. 

A common assumption is that reduced environmental impact must be paid for by higher prices or lower profit margins. This is a dangerous assumption because it reinforces the idea that environmental issues are a problem and cost. With good design you can achieve reduced impact and higher value at the same time. 

Discontinuity between the physical form of the sample and reference material used can lead to error. This is another manifestation of the matrix effect, but one which has to be considered when analyzing biological and environmental samples. There is no easy answer to the relationship between partide size and homogeneity. It is a popular assumption that the smaller the partide size the less the degree of heterogeneity. In some cases this may be true but there are a number of considerations. 

Half-life estimates of approximately 28 days for thiophanate-methyl indicate a very slow decay compared to methiocarb with an estimate of half-life of about 11 days. The application of a model based on a first-order decay process resulted in fairly high R2 and significant fit. The results suggest that both pesticides are relatively stable compared to other compounds under similar environmental conditions (Brouwer et al., 1994). With respect to the objectives of the study and the proposed model, it can be stated that the results confirm the assumption of a linear relationship between application rate (for both application techniques) and the increase of dislodgeable foliar residue. This relationship holds for modeling purposes. The contribution of the crop density or total crop surface area to the process of interception cannot be quantified with the results of the present study. Because the interception factor ranges from about 0.35 to 0.9 (Willis and McDowell, 1987), the... 

Partition coefficients can then be combined to describe the ecosystem, assuming all the compartments are well mixed such that equilibrium is achieved between them. This assumption is generally not true of an environmental system since transfer rates between compartments may be slower than transformation rates within compartments. Therefore, equilibrium is never truly approached, except for perhaps with very stable compounds. However, such simplifications can give an indication into which compartments a chemical will tend to migrate and can provide a mechanism for ranking and comparing chemicals. 

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