We ask the question, “for minimizing mean response time (sojourn time), which is preferable: one fast server of speed 1, or k slow servers each of speed 1/k?” Our setting is the M/PH/k system with two priority classes of customers, high priority and low priority, where PH is a phase-type distribution. We find that multiple slow servers are often preferable, and we demonstrate exactly how many s...

We model a call center as a preemptive-resume priority queue with time-varying arrival rates and two priority classes of customers. The low priority customers have a dynamic priority where they become high priority if their waitingtime exceeds a given service-level time. The performance of the call center is measured by the mean number in system for the two customer classes. A fluid approximati...

The number of suicides increased for young adults in a 20 year period when the number among older adults declined. The rise in standardised mortality ratios was larger for young men (72.43%) than young women (19.04%). The suicide gap between the most and least deprived areas widened more for young women; there were over six times as many deaths in the most compared with the least deprived fifth...

BACKGROUND A well targeted flu vaccine strategy can ensure that vaccines go to those who are at the highest risk of getting infected if unvaccinated. However, prior research has not explicitly examined the association between the risk of flu infection and vaccination rates. PURPOSE This study examines the relationship between the risk of flu infection and the probability of getting vaccinated...

Following legislation, European Member States should have multi-annual control programs for contaminants, such as for mycotoxins, in feed and food. These programs need to be risk based implying the checks are regular and proportional to the estimated risk for animal and human health. This study aimed to prioritize feed products in the Netherlands for deoxynivalenol and aflatoxin B₁ monitoring. ...

A number of these systems are considered critical for the social welfare of modern societies and thus need priority protection (CNIP, 2006; Birchmeier, 2007). While the EU and other national and transnational administrations are recognizing the importance of this safety issue with specific directives and programs (OHS, 2002; EU 2005 and 2006; IRGC, 2006), it seems that the classical methods of ...

Millions of carloads of hazardous materials are transported annually throughout the North American railway network. The risk of hazardous materials release incidents makes railway transportation safety a high priority. A number of strategies have been implemented or are in development to reduce the risk. Each risk reduction strategy has a particular effect on safety and different risk reduction...

Failure modes and effects analysis (FMEA) has been used to identify the critical risk events and predict a system failure to avoid or reduce the potential failure modes and their effect on operations. The risk priority number (RPN) is the classical method to evaluate the risk of failure in conventional FMEA. RPN, which ranges from 1 to 1000, is a mathematical product of three parameters—severit...

We study the problem of priority inversion in distributed real-time and embedded systems and propose a solution based on a distributed version of the priority inheritance protocol (PIP). Previous approaches to priority inversions in distributed systems use variations of the priority ceiling protocol (PCP), originally designed for centralized systems as a modification of PIP that also prevents d...