We study the positive recurrence of piecewise Ornstein–Uhlenbeck (OU) diffusion processes, which arise from many-server queueing systems with phase-type service requirements. These diffusion processes exhibit different behavior in two regions of the state space, corresponding to “overload” (service demand exceeds capacity) and “underload” (service capacity exceeds demand). The two regimes cause...

Abstract In this paper, we propose a new robust cycle-based control policy for single installation inventory models with non-stationary uncertain demand. The policy is simple, flexible, easily implementable and preliminary numerical experiments suggest that the policy has very promising empirical performance. The policy can be used both when the excess demand is backlogged as well as when it is...

A pilot scale wastewater treatment plant was designed, constructed and operated on site to treat wastewater from a combined effluent drain. The activated sludge process (ASP) was used at three different hydraulic retention times (HRT) of 12, 10 and 8 hrs at an average MLSS concentration of 3500 mg/L. Under each HRT, the pilot plant was operated for a period of 10-12 weeks. Chemical oxygen deman...

The efforts of modern civilization to create an environment to meet human aspirations have successfully resulted in constant improvements of our lifestyle, but it has increased risks to human and ecological health. This situation has motivated many scientists throughout the world to analyze the environmental factors that can affect our health or ecology and to calculate the levels of risk. In B...

A systematic understanding of traffic dynamics on road networks is crucial for many transportation studies and can help to develop more efficient ramp metering, evacuation, signal control, and other management and control strategies. In this study, we present a theory of multi-commodity network traffic flow based on the Lighthill–Whitham–Richards (LWR) model. In particular, we attempt to analyz...

Consider stochastic production-inventory control problem in which there are multiple capacity sources, multiple heterogeneous products, non-stationary demand and time-varying costs. If shortage costs can be evaluated the natural objective is to minimize expected production, inventory and shortage costs. Otherwise one can use service level requirements as target inventory while trying to minimiz...

Without significant intervention, demand for crude oil could rise by a further 25% by 2035, stemming from its use for transportation, particularly road transport. Many technologies for alternative fuels and substitute transport energy carriers are being researched, but successful implementation of these technologies at scale will require attention to consumer-behavioural and policy challenges a...

This paper studies a Stochastic Multi-Period Location-Transportation Problem (SMLTP) characterized by multiple transportation options, multiple demand periods and a stochastic stationary demand. We consider the determination of the number and location of the depots required to satisfy a set of customer’s demands, and the mission of these depots in terms of the subset of customers they must supp...

On an otherwise symmetric oligopoly market with stochastic demands for heterogeneous products firms can either hire an employee or partner or buy the required labor input on the labor market. Whereas the wage of hired labor does not depend on the realization of stochastic demand, the price of bought labor input reacts positively to product demand. We first solve the market by deriving the equil...

This paper studies the computation of order up to levels for a stochastic programming inventory problem of a perishable product. Finding a solution is a challenge as the problem enhances a perishable product, fixed ordering cost and non-stationary stochastic demand with a service level constraint. An earlier study [6] derived order-up-to values via an MILP approximation. We consider a computati...