Timing-critical design

Mechanical properties of the electrode turned out to be a critical factor not clearly understood at the time of designing of LBG1025 graphite. Authors have learned that a battery cannot be cycled if the coating does not adhere properly to the current collector. 

A careful study of the above tables and figure 12.1 will indicate why a rubber chemist spends a lot of time in designing compounds with various cross link densities for oil field service as well as for other critical applications. It can also be observed that tear strength, fatigue life and toughness, all important requirements for oil field, rubber seals pass through an optimum at low cross link density and fall off with increase in cross link, whereas the most important sealing properties such as hysteresis and compression set improve with increased cross link. 

In the lead identification and lead optimization phases of discovery, there is greater focus on thermodynamic solubility measurements. Thermodynamic solubility assays are designed to determine the solubility of the stable crystalline form of the compound, since this is the physical form that will be sought in the development phase for orally administered drugs. As such, thermodynamic solubilities provide discovery projects with a better risk assessment of likely formulation issues in development. Thermodynamic solubilities, unlike kinetic solubilities, are less dependent on the initial physical form of the compound and being less time critical also tend to be more reproducible. This is particularly important from a molecular design perspective where chemists are seeking to modify molecular structure to improve solubility. 

A disadvantage of REX operation is its difficulty with low-viscosity fluids (< 10 Pa-s) and temperature control especially for highly exothermic reactions. Usually, a critical design criterion is that REX is not feasible beyond the residence times greater than... 

Critical design parameters for these systems can be cast into idealized, quantitative design equations in order to define such factors as reactor volume-flow, electrode overpotential, and hold-up time, as functions of reactor design (40). 

The most important testing protocol for resistance to deterioration of critical physical properties upon exposure to heat, especially over prolonged periods of time, was designed by the Underwriters Laboratories (UL) [1], The UL temperature index is used to qualify materials for applications (such as use in electrical equipment) regulated by UL. The main purpose of these tests is to ensure that a polymer can be used safely for a prolonged period of time in these applications. A larger value of the UL temperature index implies greater stability, defined in... 

Knowledge of the fornr of the rate equation, coupled with the experimental determination of the value of the rate constant, k, and the order, n, are valuable in a number of ways. Industrial chemists use this information to establish optimum conditions for preparing a product in the shortest practical time. The design of an entire manufacturing facility may, in part, depend on the rates of the critical reactions. 

The hydrostatic test pressure is 1.25 times the design pressure corrected for temperature, rather than the usual 1.5. Division 2 establishes upper limits for the test pressure relative to the yield strength at test temperature. The pneumatic test pressure is 1.15 times the design pressure corrected for temperature rather than 1.25 required by Division 1. Division 2 has no provision for proof tests to establish the maximum allowable working pressure. But Appendix 6, Experimental Stress Analysis, provides for the determination of the critical or governing stresses for unusual geometries for which theoretical stress analysis is inadequate. 

Decentralized decision making is, of course, required in some time-critical situations. But like all safety-critical decision making, the decentralized decisions must be made in the context of system-level information and from a total systems perspective in order to be effective in reducing accidents. One way to make distributed decision making safe is to decouple the system components in the overall system design, if possible, so that decisions do not have systemwide repercussions. Another common way to deal with the problem is to specify and train standard emergency responses. Operators may be told to sound the evacuation alarm any time an indicator reaches a certain level. In this way, safe procedures are determined at the system level and operators are socialized and trained to provide uniform and appropriate responses to crisis situations. 

Selecting ceramics for use at high temperatures or under applied load requires consideration of their long-term stability. Time dependent deformation is known as creep, and creep resistance is a critical design parameter. Even if creep does not lead to failure, a change in shape or size may render a component useless. The mechanism responsible for creep depends on temperature, stress, and the microstructure of the ceramic. 

The designer needs to consider the time it takes to process the information presented and make a correct decision. Due to the time constraint, the depth of the analysis expected from the crew should be proportionally inversed to the time criticality of the expected reaction. The information needed by the flight crew should be presented in such a way as to assist the processing task, not only under normal circumstances, but also when performance is affected by stress (e.g. during failure conditions) or fatigue. 

Optimum SDA performance is achieved through proper choice of L/D, droplet size, and residence time. The designed residence time for most SDAs is 10-12 sec at maximum design. Inspection and maintenance is critical to continued good operation of the scrubber. 

Mine hoist brake systems are a critical system of a mine hoist. In order to bring a potentially hazardous situation under control, they must work correctly and as designed each and every time. Traditionally designed (non SIL compliant) mine hoist brake systems have proven to be generally safe and reliable. While a traditionally designed hoist brake system will be designed to limit hazardous effects from a random component failure, they may still be subject to systematic failures such as commissioning errors or maintenance errors. 

The high anisotropy of fibers, such as Kevlar, Twaron, Technora, Spectra and Dyneema, makes it doubly important to get the fiber orientation right in the composite and the weak transverse bonding means that there is easy yielding in compression and relatively poor temperature/time performance. Design decisions are thus very important. The ceramic fibers are less critical in these respects. 

The type of load-transfer switch used in the UPS system is another critical design parameter. The continuity of AC power service to the load is determined by the type of switching circuit used. An electromechanical transfer switch, shown in Fig. 10.137, is limited to switch times of 20 to 50 ms. This time delay can cause sensitive load equipment to malfunction, and perhaps shut down. A control circuit actuates the relay when the sensed output voltage falls below a preset value, such as 94% of nominal. A static transfer switch, shown in Fig. 10.138, can sense a failure and switch the load in about 4 ms. Most... 

A stated requirement of the HEAT/ACT project SPP was that the PSC should be prepared to support Preliminary and Critical Design Reviews (PDR and CDR). Producing the PSC would also ensure that the Interim Safety Case could be prepared in time to support first flight. 

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