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abstract

AbstractA machine or production system is subject to random failure. Upon failure the system is replaced by a new one, and the process repeats. A cost is associated with each replacement, and an additional cost is incurred at each failure in service. Thus, there is an incentive for a controller to attempt to replace before failure occurs. The problem is to find an optimal control strategy that balances the cost of replacement with the cost of failure and results in a minimum total long‐run average cost per unit time. We attack this problem under the cumulative damage model for system failure. In this failure model, shocks occur to the system in accordance with a Poisson process. Each shock causes a random amount of damage or wear and these damages accumulate additively. At any given shock, the system fails with a known probability that depends on the total damage accumulated to date. We assume that the cumulative damage is observable by the controller and that his decisions may be based on its current value. Supposing that the shock failure probability is an increasing function of the cumulative damage, we show that an optimal policy is to replace either upon failure or when this damage first exceeds a critical control level, and we give an equation which implicitly defines the optimal control level in terms of the cost and other system parameters. Also treated are some more general models that allow for income lost during repair time and other extensions.

Theories of cognitive consistency are formally integrated and compared by applying a multiple regression modeling strategy that has developed in the analysis and formal integration of theories of social consistency. Several important studies of cognitive consistency theories are reviewed to locate conceptual omissions in tests of the theory. In addition, several issues that are problematic in testing consistency theories are reviewed, alternative solutions are discussed, and areas in which additional work is needed are noted.

PurposeThis article aims to describe the effects of the communication style of the message sender (threatening or neutral), status of the sender (equal to or higher than the recipient) and the power relationship between sender and recipient (from the same department or not) on the blood pressure of the recipient of an e‐mail messageDesign/methodology/approachThe study was conducted under controlled laboratory conditions. The experiment was a mixed design, using both within and between subjects variables. The independent variable for the within subjects factor was the task that participants performed. There were three tasks: answering a questionnaire, reading a non‐threateningly worded e‐mail reprimand, and reading a threateningly worded e‐mail reprimand. Although the study used students as participants, the messages they received were from real people in a University College. Discusses the implications in the area of occupational health.FindingsDiastolic blood pressure was significantly higher (p<0.01) when recipients were reading the threateningly worded reprimand compared to reading a non‐threateningly worded reprimand. The effect of status on blood pressure was significant (p<0.05) but only for recipients in the same department as the message sender.Originality/valueThe results add to the evidence that communication style and status can have a direct impact on the recipient's physiological response.