Interventions human

The stocking of ponds, lakes, and reservoirs to increase the production of desirable fishes that depend on natural productivity for their food supply and are ultimately captured by recreational fishermen or for subsistence is another example of extensive aquaculture. Some would consider such practices as lying outside of the realm of aquaculture, but since the practice involves human intervention and often employs fishes produced in hatcheries, recreational or subsistence level stocking is associated with, if not a part of aquaculture. Similarly, stocking new ponds or water bodies which have been drained or poisoned to eliminate undesirable species prior to restocking, can lead to increased production of desirable species. 

The safe operation of a chemical process requires continuous monitoring of the operation to stabilize the system, prevent deviations, and optimize system performance. This can be accomplished through the use of instrumentation/control systems, and through human intervention. The human element is discussed in Chapter 6. Proper operation requires a close interaction between the operators and the instrumentation/control system. To a large extent, batch operations have simple control systems and are frequently operated in the manual mode. The instrumentation system is the main source of information about the state of the process. Some of the typical functions of the instrumentation/control system are... 

Operator has to observe the process more frequently as a result of nonsteady state operating conditions. This requires more frequent control interventions, leading to an increased potential for human error. 

Although much as been done, much work remains. Improved material models for anisotropic materials, brittle materials, and chemically reacting materials challenge the numerical methods to provide greater accuracy and challenge the computer manufacturers to provide more memory and speed. Phenomena with different time and length scales need to be coupled so shock waves, structural motions, electromagnetic, and thermal effects can be analyzed in a consistent manner. Smarter codes must be developed to adapt the mesh and solution techniques to optimize the accuracy without human intervention. 

Defence in depth. The design process should ensure that multiple levels of protection are provided and the necessity of human intervention is minimized. 

For some processes, human intervention is included in the response to an upset. See Section 6.5 for a discussion of the human response time in process control. 

This is particularly relevant in situations where a human intervention is required in response to a potentially hazardous plant situation. 

Activation of the blowdown, however, will not depressurize a system fully for a considerable length of time. One of the reasons for considering retaining the possibility of human intervention was that the automated blowdown system was not considered completely reliable at the time because of the limitations of the fire and gas detection hardware. This would have the effect of resulting in increasing the likelihood of spurious blowdown production losses. 

Protection is the branch of electric power engineering concerned with the principles of design and operation of equipment (called relays nr protective relays ) which detect abnormal power system conditions and initiate corrective action as quickly as possible in order to return the power system to its normal state. The quickness of response is an essential element of protective relaying systems—response times of the order of a few milliseconds are often required. Consequently, human intervention in the protection of system operation is not possible. The response must be automatic, quick, and should cause a minimum amount of disruption to the power system. 

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