Worst-case tests

Experimental methods coming from laboratory-based studies of worst-case testing of simulated workplace conditions. 

Safety is known. Most DOD standard designs have been proof-tested" by exposure of a test structure to the explosive effects of a nearby detonation. The worst-case test condition is depicted in Figure 2. 

The scope section describes what the process validation protocol covers, the number of batches, and what it does not cover. In this part, usually packaging validation or mouthpiece testing is included or excluded. Any worst-case tests may be briefly described. Stability commitments and stability protocols should be mentioned. 

Worst-case testing This encompasses upper and lower limits, and circumstances that pose the greatest chance of finding errors. 

The system is not only tested under typical operating conditions but also at the limits under which it will be required to operate - an approach known variously as worst case testing, gray box testing or testing of boundary conditions. Testing boundary conditions is important because most software errors occur around its boundary limits. Combinations of several worst cases are also tested. For example, if a system is specified to acquire data from multiple instruments and the data acquisition rate can be varied, test cases include acquisition from the maximum number of instruments at the highest data rate. 

To illustrate the use of designed experiments in this process, a case study is presented involving a packaging sealer (3). Designed experiments in conjunction with other tools are used to create a control plan that is then validated. The DOE results are also used to identify worst-case conditions for worst-case testing, and to help select sample sizes for worst-case and final PQ testing. 

At the Biyan site the main line flow constrictor was installed flush against an isolation valve and a 90° elbow. This was done to establish worst case test conditions. It was expected on theoretical grounds that the operation of the flow separator would be insensitive to upstream flow conditioning of the gas. Test data taken to date has proven this to be the case. 

Worst-case testing shall be performed to assess the extreme (i.e., worst) cases specified by the application of analytical technique. 

The direction of these glare sources should be adjustable and specified. As there are different mechanisms responsible for the different glare types, appropriate worst-case tests should be defined (coherent light source, direct and indirect glare etc.)... 

Endurance Burn Under certain cou(itious, a successfully arrested flame may stabilize on the unprotected side of an arrester element. Should this condition not be corrected, the flame will eventually penetrate the arrester as the channels become hot. An endurance burn time can be determined by testing, which specifies that the arrester has withstood a stabilized flame without penetration for a given period. The test should address either the actual or worst-case geometry, since heat transfer to the element will depend on whether the flame stabilizes on the top, bottom, or horizontal face. In general, the endurance burn time identified by test should not be regarded as an accurate measure of the time available to take remedial action, since test conditions will not necessarily approximate the worst possible practical case. Temperature sensors may be incorporated at the arrester to indicate a stabilized flame condition and either alarm or initiate appropriate action, such as valve closure. 

Another method is a series of exhaust dilution equations based on Wilson and Lamb " and a series of earlier papers summarized in ASHRAE. This method is based on wind tunnel tests on simplified buildings and is intended to provide conservative (low dilution) results. Wilson and Lamb compared the model to actual field data collected at a university campus and found that the model did indeed predict dilutions similar to measured worst-case dilutions suitable for a screening model. However, many cases resulted in conservative Linderpredictions of dilutions. ... 

Operational qualification involves performing a series of tests to check that all elements of the system are functional across the specified operating range. This usually involves performing challenges at the worst case extreme operating conditions. The process should allow confirmation of final operation, maintenance and calibration procedures. 

A nearly perfect diverging wavefront would exit the test plate appearing as though it came from a source 100 m away. A segment would be positioned so that its mean center of curvature was coincident with that virtual source 100 m away. In the worst case in our example, the un-equal air path would be about 4 m rather than 204 m. Interference would take place between the wavefront reflected off the 100 m radius side of the test plate and the segment. The roughly 3 m back to the source and beamsplitter is common path and will not affect the interference pattern. 

In fact, when chemical class searches are chosen, the user should change as many of the "U" designations in Chemical Attributes as possible. When a U" is left, the system assigns a "worst case" value to that attribute in order to make the most conservative choice of materials. Thus, if the answer to the question, "Is the chemical a known or potential carcinogen " is "U," the system assigns it a "yes" because that is the worst case and will produce the most conservative selections when the database is evaluated for materials that have been tested against the class of compounds under consideration. 

Soil properties A Soil texture (sand, silt, clay), organic matter/carbon content, and pH Stones, roots, and hardpans must be largely absent to allow representative sampling of soil profile Soil properties should appear uniform over test site Soil texture data should be available at time of site selection. Soil properties must match study purpose. This can be realistic use conditions, realistic worst-case or worst-case in terms of agrochemical mobility and persistence Must ensure that the majority of samples can be taken from the deepest sampling horizon. Information about sub-soils can be obtained from soil maps, test coring and on-site interviews... 

Application of the test substance to the target crop prior to harvest represents a worst-case scenario for potential exposure to workers for the crop category. 

End-use formulations should be used as the test substance. If an active ingredient is marketed in two commercial formulations, then both should be used in the study, since there may be differences in residue levels and dissipation rates, e.g., a wettable powder versus a liquid formulation. The best solution would be plots located at the same site for a side-by-side comparison. This should only be necessary at one of the sites. However, each formulation should be represented in the study unless a strong case can be made for a worst-case scenario. 

It is assumed that the moisture content of the soil has been determined to be approximately 50% under worst-case conditions. Using this information and the results from vendor tests, it has been determined that a minimum dose of one part solidification reagent to two parts soil is required for the migration control of lead. Testing has shown that the optimum solidification reagent mixture would comprise ca. 50% fly ash and ca. 50% kiln dust. Thus, ca. 7000 t (6364 T) each of fly ash and cement kiln dust would be required. The reagents would be added in situ with a backhoe. As one area of the soil is fixed, the equipment could be moved onto the fixed soil to blend the next section. It may be anticipated that the soil volume would expand by ca. 20% as a result of the fixation process. This additional volume would be used to achieve the required slope for the cap. An RCRA soil/clay cap placed over the solidified material is necessary to prevent infiltration and additional hydraulic stress on the fixed soil. It is estimated that the fixation would reduce lead migration by 40% and that the fixed soil may pass the U.S. EPA levels for lead. 

Compliance with U.S. EPA s design performance standards can be demonstrated through one-dimensional, steady-state flow calculations, instead of field tests. For detection sensitivity, the calculation of flow rates should assume uniform top liner leakage. For detection time, factors such as drain spacing, drainage media, bottom slope, and top and bottom liners should all be considered, and the worst-case leakage scenario calculated. 

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