Human capacity error

Limitations in human capacity to perceive, to attend to, remember, process and act on information are all relevant in the context of human error. Typical... 

Human dependability encompasses the risk of human errors, but also the human capacity to perform well, even beyond expectations, and to anticipate and solve problems. Consequently the project addresses both human error and how it can be avoided, as well as how one can depend on humans to create safety in space operations. Thus, the project also includes theories and perspectives from resilience engineering and High Reliability Organizations (HRO). 

All behaviour critical to the causation of accidents could not be shaped by information and motivation alone. Errors arising from insufficient adaptation of the work task to human capacity have to be approached through technical and ergonomic measures. .. Without such understanding, people will still be blamed for things that they couldn t have done otherwise and preventative measures will continue to be misdirected. 

In recent years robots and other automated instruments, and entire integrated systems, have been developed to accelerate the crystallization process (Luft et al., 2003 DeLucas et al., 2003 Hosfield et al., 2003 Bard et al., 2004). They have the capacity to screen thousands of crystallization conditions, and they do so precisely and reliably, with fewer errors and better record keeping than most humans. In many large laboratories these have become essential pieces of equipment. Using standard, usually commercially available screening kits, sometimes supplemented by local favorites, they can often arrive at acceptable crystals in the most expeditious possible manner. 

In the above methods, the separated albumin (or whole serum if total protein is to be determined) is reacted with excess copper in approximately 1 N alkali. A macromethod is also available which utilizes the capacity of albumin to react with copper(II) in a mole ratio of 1 1 (K32). This is an amperometric titration of blood serum (1 ml) in 0.1 M ammoniacal am-moniiun nitrate pH 9.2 with CuS04 (4.8 X 10 M). Under these conditions human y-globulin did not react, so that the fair agreement by this method with results obtained by a biuret method after sulfite fractionation (K32) is probably the result of a balance of errors. In view of the interest in the small fraction of albumin-boimd copper in hepatolenticular degeneration, and the paucity of information on the unique binding reaction presumably with N-terminal aspartyl residues, further investigation would be valuable. 

According to one point of view, expressed by Laplace, dynamical systems like the Solar System are completely deterministic, so probability theory can have no relevance. But this point of view requL a God-like omniscience in being able to determine initial conditions exactly. This requires an infinite number of digits and is beyond the capacity of anybody or anything ctf finite size, including the observable Universe (Ford 1983) [Ref. 59]. In reality measurement is only able to determine the state of a classical system to a finite number of digits, and even this determination is subject to errors, without quantum mechanics, and whether this determination is made by human or machine. Such measurements limit the known or recorded motion to a range of possible orbits. 

The next step employs quantitative models of human performance and technology to reach an applied decision that best satisfies the required resources if sufficient resources are available. If sufficient resources are not available, additional performance and skill resources need to be obtained to complete the task, or the task requirements need to be reduced. Quantitative models of human performance include MHP, THERP, and ERM. Using the MHP, the human processing parameters needed for each task operation are identified. The time values assigned to each parameter are used to compute task time estimates. This approach is limited to estimating performance in terms of time. THERP maps operations to the tasks included in human reliability databases to estimate human error probabflities. The ERM provides a framework for specifying performance and functional capacities at the resource level. It is the only model that (1) incorporates aU required dimensions of performance and skills and (2) uses consistent modeling constructs across tasks, humans, and machines. 

After the task is specified, human and machine performance models can be applied to estimate task performance. The MHP and keystroke-level performance model can provide task performance estimates in terms of task completion time. THERP can be used to estimate human error probabilities for each task and task sequence. The ERM approach can be used to estimate performance along any required dimension and to compare required with available resources along any required dimension as long as the human performance data are available. The results of the ERM assessment would identify stress levels on capacities (e.g., resources stressed too long or beyond maximum capacity). These results indicate limiting factors to successful task performance. Limiting factors can be identified at elemental or intermediate performance resource levels. As such, the ERM represents a more comprehensive and internally consistent model than the others. It is more comprehensive in that it can be used to model any performance dimension. It is... 

In task analysis, it is common practice to distinguish between stress and strain. However, these terms are sometimes used interchangeably and confusedly. In this chapter, stress refers to a condition that may lead to an adverse effect on the body, whereas strain refers to the effect of stress on the body. For example, working at a computer job in dim lighting often leads to headaches. The dim lighting is considered the stress, and the headache is the strain. The term stressor is also widely used as a synonym for stress. Strain has often been wrongly called stress. These terms must be clearly defined to determine which factors are causative ones (stresses) and which are consequences (strains). Stress is determined by task demands, while strain is determined by the amount of physical resources expended beyond some tolerable level, defined by the person s resource capacities. The stress-strain principle is pivotal to task analysis when one is concerned with errors, cumulative traumas, and injuries in the workplace and is applicable to task situations where task demands are likely to exceed human resource capacities. 

One of the key problems for the future then will be discovering where technology can help and where we need to rely on human judgement. As Bates etal. (2001) point out, human beings are erratic and err in unexpected ways, yet we are also resourceful and inventive and can recover from errors and crises. In comparison, machines, at least most of those currently in use, are dependable but also dependably stupid. An almost perfect instruction, quite good enough for any human operator, can completely disable a machine. Human beings also have the capacity to respond to an unknown unknown , that is an event that could not have been predicted (Bates et a/.,2001). 

Turning to the hazards and the impact of industrial processes. Many disasters such as Flixborough, Seveso and Bhopal (see section 1.6) have ably illustrated the environmental impact of human errors and the need for rigorous safety controls. The capacities and productivity of chemical plants are driven upwards as are the magnitudes of losses in terms of economic cost and fatalities. Analysis of the major causes of accidents in the U.S. chemical industry in the 1978-1980 period highlighted that ... 

There are a number of techniques available to extract ATP from cells. Some use trichloroacetic acid (TCA), which also aids in stabilizing the molecule. TCA has a good extraction capacity, is relatively quick, has a reduced potential for human error, and does not discriminate between the different microbiological fractions of activated sludge. Luminescence produced in the luciferin-luciferase reaction can be measured using scintillation counting equipment or a range of luminometers currently on the market. 

Natural circulation coupled with negative temperature reactivity coefficient and large heat capacity make loss of flow accidents inconceivable enables decay heat removal using RVACS only and enables autonomous control and high tolerance to human errors. 

Overload—Operators may experience a state of overload when the demands of a task are beyond their limited attentional capacity (Young and Stanton, 2002). Various consequences are associated with overload, including mental saturation, fatigue, stress, and human error. 

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