Time dependency, performance-influencing factors

The experiments are performed according to the chosen design and a response or a number of responses are measured. The sequence in which the experiments are performed can influence the estimation of the effect of a factor [36]. The reason for this lies in the fact that the measurements can be influenced by different sources of error. Each measurement is influenced by uncontrolled factors that cause random error. Measurements can also be influenced by systematic errors or by systematic errors caused by drift (linear drift due to time-dependent factors). The occurrence of systematic errors or of drift will affect the estimation of the effects of the factors fi om the design [36]. 

In the first generation of HRA methods, human failure was seen and investigated as random phenomenon, with some distribution in time formed by performance shaping factors influence. In HRA second generation method/framework ATHEANA, treatment of human failure is different, as it is seen as cause based consequence of error forcing context actuation. Still, the plant specific experience can lead to the conclusion that some residual randomness should be kept in hiunan failure model, similarly to the case of (equipment) dependent errors and residual common cause failures. 

Physical Activity (Work) and Other External Influence Factors. Usually a distinction is made between pulse rate at rest and pulse rate under physical (work) stress. The work pulse frequency depends on the time and level of work stress as well as the degree of fitness of the person performing the work. Pulse frequency for permanent work is that which at a prolonged uniform level of work will remain fairly constant. Up to that state of equilibrium (steady state) there is almost a linear relationship between pulse frequency and oxygen intake. Beyond the steady state, pulse frequency will increase until complete exhaustion sets in (Figure 6.12). The permanent performance limit for physical work is reached at that point in time when, at a maximum work load, the pulse frequency does not rise any further. 

Change in Performance as a Function of Time. Man s performance depends on a variety of influence factors. Among them are calculable ones as well as those which cannot be assessed or predicted. 

Time to delamination testing of multilayer PCBs has become a common test for lead-free assembly compatibUity. However, several factors beyond the base material type can have an influence on performance. So care needs to be taken in assessing why a particular PCB might exhibit a low time to delamination. On the other hand, if a particular type of base material exhibits low times to delamination, little can be done in PCB manufacturing to improve performance. In short, a given material offers a certain performance entitlement. Whether this performance level is realized in the finished PCB is dependent on several factors, primarily related to PCB manufacturing processing. 

The cycle time for the manufacture of a rotation molded product can be between five to forty minutes, depending on various factors. Important influencing factors are the type and size of the molds, machine performance, material choice, and wall thickness. 

Measurement of performance. Quality Management requires that measures of performance be established for every activity. These measures include end-of-pipe measurement, such as amounts of material released into the environment or injury rates, and in-process measures of how efficiently you are managing, such as time to review safety improvement proposals or total resources expended on PSM. Each team should be required to identify potential performance measures for the processes they are developing and the activities these processes manage. Many of the end-of-pipe measures will already exist these should be critically examined to ensure that they truly measure performance and are not unduly influenced by other factors. For example, the number of accidents in a fleet of road vehicles is almost directly dependent on the number of miles driven with no improvement in performance, a reduction in miles driven would reduce the number of accidents. 

The quality of chromatographic separation depends on the composition of the stationary phase of the column and the instrument settings. The temperature regime of the oven the flow rate of the mobile phase gas through the column the temperature of the injection port—all of these factors influence compound retention time and peak resolution. The reduction in the chromatographic analysis time may adversely affect compound resolution. Because commercial laboratories always balance a need for a sufficient resolution with a need to perform analysis within the shortest possible period of time, the quality of chromatographic resolution is often traded for the speed of analysis. 

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