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Sequential logic elements
Published in J. R. Gibson, Electronic Logic Circuits, 2013
In any real circuit one of the output gates will operate marginally faster than the other and the circuit will not oscillate but will go to one of the Q = Q’ states; which one of the two states cannot be predicted. In this particular case the circuit action is indeterminate and a race condition or hazard is said to exist. Many different types of hazard may arise in logic circuits; the term is used whenever the output of a circuit cannot be predicted or when an incorrect output is produced (even if only for a brief time) before the circuit produces the correct one. A race condition is one particular type of hazard and arises when the final circuit state depends upon the relative operating speeds of two or more circuit components. Hazard conditions may occur in any sequential logic circuit; they must be identified and excluded in some way.
Hazard and Risk Analysis
Published in Richard C. Fries, Handbook of Medical Device Design, 2019
Hazard is a potentially dangerous condition, which is triggered by an event. This event is often called the cause of the hazards. A hazard will not necessarily cause harm, because any hazard will have to be existent for a period of time before it will become dangerous. This time is often called hazard latency time. Examples are radiation or exposure hazards, which need to exceed a specific dose in order to become dangerous. The hazard latency time is an important property of each individual hazard and determining this time should be part of the hazard identification process. A second important hazard property is the observability and detectability. These factors are also hazard specific and will provide important information for the design of risk mitigation measures.
Combinational Logic Networks
Published in John C. Morris, Digital Electronics, 2013
Chapter 2 showed that a propagation delay time (tpd) exists in all logic gates and this is the start of the problem. If you look at the timing of Fig. 3.33(b) you will see that when both inputs A and B are at logic 1 the output of the inverter should be logic 0. But because of the propagation delay of the inverter there will be a short period of time (tpd) when the output will be at logic 1 resulting in an unwanted output pulse or glitch. If a change in a single input can cause a glitch, a static hazard is said to exist. If there are a number of possible paths involved in the circuit, each introducing its own possibly different propagation delays, then a dynamic or race hazard exists.
Leveraging wearable technologies to improve test & evaluation of human-agent teams
Published in Theoretical Issues in Ergonomics Science, 2020
Amar Marathe, Ralph Brewer, Bret Kellihan, Kristin E. Schaefer
According to MIL-STD-882E, there is an 8-step safety process for documenting the system safety approach for identifying and documenting hazards, assessing and documenting risk, identifying and documenting risk mitigation measures, reducing risk, verifying, validating, and documenting risk reduction, accepting risk and documenting, and managing life-cycle risk. Under these steps, a hazard is ‘a real or potential condition that could lead to an unplanned event or series of events resulting in death, injury, occupational illness, damage to or loss of equipment or property, or damage to the environment’ (p. 5). A hazard analysis traditionally includes evaluation of the system components, energy sources, ordnance, hazardous materials, interfaces and controls, interface considerations to other systems when in a network or systems-of-systems architecture, material compatibilities, inadvertent activation, commercial-off-the-shelf, government-off-the-shelf, non-developmental items, and government-furnished equipment. All risks and hazards are assigned ratings denoting the level of severity (from negligible to catastrophic) and probability of occurrence (frequent, probably, occasional, remote, improbably, eliminated). Based on these levels, risk reduction and mitigation strategies are recommended by the evaluators.
Forensic human factors and ergonomics analysis of a trip and fall event in a parking lot
Published in Theoretical Issues in Ergonomics Science, 2020
Designing out the hazard (eliminating or reducing it) is usually the most effective hazard control method. One way to reduce the likelihood of a trip and fall is to remove obstructions such as eliminating wheel stops, especially those that warp or have protruding bolts. If this had been done, Mrs. Lumens would not have been injured in the subject parking lot.