This paper is about learning a continuous approximation of the Pareto frontier in Multi–Objective Markov Decision Problems (MOMDPs). We propose a policy–based approach that exploits gradient information to generate solutions close to the Pareto ones. Differently from previous policy–gradient multi–objective algorithms, where n optimization routines are use to have n solutions, our approach perf...

BACKGROUND Many hospitals have adopted smoke-free policies on their property. We examined the consequences of such polices at two Canadian tertiary acute-care hospitals. METHODS We conducted a qualitative study using ethnographic techniques over a six-month period. Participants (n=186) shared their perspectives on and experiences with tobacco dependence and managing the use of tobacco, as wel...

Threats associated with climate change may damage forests. To encourage adaptation in countries with a lot of privately owned forest, policy measures directed at private forest owners may be implemented. By means of policy scenarios, the present study examined the effects of two hypothetical policies: an advice and an economic incentive, on climate change adaptation among private forest owners ...

In this paper, a geometric process repair model for a k-dissimilar-component series repairable system with one repairman is proposed. For each component, the successive operating times form a decreasing geometric process whereas the consecutive repair times constitute an increasing geometric process. Under this assumption, we consider a replacement policyM = (N1,N2, . . . ,Nk) based respectivel...

We develop a mathematical programming approach for the classical PSPACE hard restless bandit problem in stochastic optimization. We introduce a hierarchy of n (where n is the number of bandits) increasingly stronger linear programming relaxations, the last of which is exact and corresponds to the (exponential size) formulation of the problem as a Markov decision chain, while the other relaxatio...

Given a Markov Decision Process (MDP) with n states and m actions perstate, we study the number of iterations needed by Policy Iteration (PI)algorithms to converge to the optimal γ-discounted optimal policy. We con-sider two variations of PI: Howard’s PI that changes the actions in all stateswith a positive advantage, and Simplex-PI that only changes the action inthe sta...

We have proposed an object -oriented RBAC (ORBAC) model to efficiently represent the real world. Though ORBAC is a good model, administration of ORBAC including creating and maintaining an access control security policy still remains a challengeable problem. In this paper, we present a practical method that can be employed in an enterprise environment to manage security policies using eXtensibl...

An M/G/1 retrial queue subject to disasters and N-policy vacation is investigated in this paper. Both positive and negative customers arrival in Poisson processes independently, and positive customers receive service immediately if the server is idle upon their arrivals. Otherwise, they enter a retrial orbit and repeat their attempt again after a random time period. Once negative customers arri...

This paper develops an economic lot-sizing production model for deteriorating items with time dependent quadratic demand and delay in payments under two levels of trade credit policy. The trade credit policy adopted here is a two-level trade credit policy in which the supplier offers the retailer a permissible delay period M, and the retailer in turn provides customers a permissible delay perio...

We investigate how “top-N percent” policies in college admission affect diversity at the high-school level. It is well understood that these policies produce incentives for students to relocate to schools with weaker competition. We show theoretically that such school arbitrage can neutralize the policy at the college level but may partially desegregate high schools. These predictions are suppo...