Lifetime reliability

CCPS defines reliability as the probability that an item is able to perform a required function under stated conditions for a stated period of time or for a stated demand. In addition to relying on QA/QC, companies use dependable data to conduct reliability analyses. Though related,- reliability is different from quality. While quality control is concerned with the performance of a product or process at one time, reliability is concerned with the performance of a product over its entire lifetime. Reliability engineering addresses all aspects of a product s life, from its conception, subsequent design, and production processes, through its practical use lifetime, with maintenance support and availability, and covers reliability, maintainability, and availability. Process safety metrics data can provide valuable input to the life data analyses used to estimate the probability and capability of parts, components, and systems to perform their required functions for desired periods without failure, in specified environments. 

N. Nemeth. O. Jadaan, and J.P. Gydcenyesi. Lifetime Reliability Prediction of Ceramic Structures Under Transient Thermomechanical Loads, NASA TP-2005-212505 (2005). 

Much could also be done in enhancing the lifetime, reliability and recyclability of both the manmade infrastructure and the consumer products which operate within it. This is probably the natural domain for adaptronics, the one in which the technology first began to be defined. 

As discussed in the introduction to this chapter (Section 10.1), the development of novel biomaterials with improved lifetimes, reliability and bioactive functions is high on the R D agenda of worldwide research. The Umited stability of HAp... 

Krasich, M. Accelerated testing for demonstration of product lifetime reliability, In Proceedings of Annual Reliability and Maintainability Symposium, pp.117-123, 2003. 

In order to account for the effects of uncertainties and potential undesirable performance of a structure during its lifetime, reliability offers the means for quantifying the level of safety associated with a structural system. A criterion widely used for characterizing safety of a structure is the first-excursion probability (see, e.g., Soong and Grigoriu, 1993). This probability measures the chances that uncertain structural responses exceed in magnitude prescribed thresholds within a specified time interval. That is, first-excursion probability measures the chances of occurrence of the following event F (which is termed in the sequence as failure event) ... 

Quality, product (manufacturing) The ability of a product to meet the customer s expectations based on cost, appearance, performance, lifetime, reliability, etc. The ability to meet standards. 

Considerable effort has been directed to determining the causes of connection failutes and to learning how to minimize the likelihood of occurrence. Acceptable failute rates range from <1 in 10 operating hours for contacts in air-frame (31) electrical systems and in some telecommunications equipment, to 100—1000 in 10 operating hours in instmments, to even larger rates for contacts in many consumer products. A failute is defined as exceedance of contact resistance, which can be as Httle as twice the initial contact resistance, that causes circuit malfunction. The required lifetimes of connectors may be >20 yr, although most required appHcation times ate shorter (see Materials reliability). 

General Collection efficiency Legal limitations such as best available technology Initial cost Lifetime and salvage value Operation and maintenance costs Power requirement Space requirements and weight Materials of construction Reliability Reputation of manufacturer and guarantees Ultimate disposal/use of pollutants... 

To produce reliable data on the lifetime and overall activity of the ionic catalyst system, a loop reactor was constructed and the reaction was carried out in continuous mode [105]. Some results of these studies are presented in Section 5.3, together with much more detailed information about the processing of biphasic reactions with an ionic liquid catalyst phase. 

It is interesting to note that independent, direct calculations of the PMC transients by Ramakrishna and Rangarajan (the time-dependent generation term considered in the transport equation and solved by Laplace transformation) have yielded an analogous inverse root dependence of the PMC transient lifetime on the electrode potential.37 This shows that our simple derivation from stationary equations is sufficiently reliable. It is interesting that these authors do not discuss a lifetime maximum for their formula, such as that observed near the onset of photocurrents (Fig. 22). Their complicated formula may still contain this information for certain parameter constellations, but it is applicable only for moderate flash intensities. 

The fastest reliable PMC transients recorded at electrodes (ZnO single crystals24) were limited by the lifetime of a 10-ns laser flash. It was apparent from the nondeconvoluted signal at shorter time scales that much faster decay processes took place and would be accessible with faster laser pulses. 

Reliable lifetime TDI values cannot be derived, since long-term studies at the appropriate doses and in the appropriate species are not available. Medium-term exposure TDIs for the estimation of risk were estimated (as the chlorides) as 0.0012 mg/kg body weight for monomethyltin and dimethyltin based on neurotoxicity, 0.003 mg/kg body weight for dibutyltin based on immunotoxicity, and 0.002 mg/kg body weight for dioctyltin, also based on immunotoxicity. No reliable TDI could be derived for monobutyltin or monooctyltin. 

Tables (3-1, 3-2, and 3-3) and figures (3-1 and 3-2) are used to summarize health effects and illustrate graphically levels of exposure associated with those effects. These levels cover health effects observed at increasing dose concentrations and durations, differences in response by species, minimal risk levels (MRLs) to humans for noncancer end points, and EPA s estimated range associated with an upper- bound individual lifetime cancer risk of 1 in 10,000 to 1 in 10,000,000. Use the LSE tables and figures for a quick review of the health effects and to locate data for a specific exposure scenario. The LSE tables and figures should always be used in conjunction with the text. All entries in these tables and figures represent studies that provide reliable, quantitative estimates of No-Observed-Adverse-Effect Levels (NOAELs), Lowest-Observed-Adverse-Effect Levels (LOAELs), or Cancer Effect Levels (CELs).

The validity of the above conclusions rests on the reliability of theoretical predictions on excited state barriers as low as 1-2 kcal mol . Of course, this required as accurate an experimental check as possible with reference to both the solvent viscosity effects, completely disregarded by theory, and the dielectric solvent effects. As for the photoisomerization dynamics, the needed information was derived from measurements of fluorescence lifetimes (x) and quantum yields (dielectric constant, where extensive formation of ion pairs may occur [60], the observed photophysical properties are confidently referable to the unperturbed BMPC cation. Figure 6 shows the temperature dependence of the... 

Chemists predominantly think in illustrative models they like to see structures and bonds. Modern bond theory has won its place in chemistry, and is given proper attention in Chapter 10. However, with its extensive calculations it corresponds more to the way of thinking of physicists. Furthermore, albeit the computational results have become quite reliable, it often remains difficult to understand structural details. For everyday use, simple models such as those treated in Chapters 8, 9 and 13 are usually more useful to a chemist The peasant who wants to harvest in his lifetime cannot wait for the ab initio theory of weather. Chemists, like peasants, believe in rules, but cunningly manage to interpret them as occasion demands (H.G. von Schnering [112]). 

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