We introduce an algorithm design technique for a class of combinatorial optimization problems with concave costs. This technique yields a strongly polynomial primal-dual algorithm for a concave cost problem whenever such an algorithm exists for the fixedcharge counterpart of the problem. For many practical concave cost problems, the fixed-charge counterpart is a well-studied combinatorial optim...

We consider an economic lot-sizing problem with a special class of piecewise linear ordering costs, which we refer to as the class of modified all-unit discount cost functions. Such an ordering cost function represents transportation costs charged by many less-thantruckload carriers. We show that even special cases of the lot-sizing problem are NP-hard and therefore analyze the effectiveness of...

PURPOSE To examine the laboratory test ordering patterns of interns to determine the effects of more senior residents' and attendings' supervision on trainees' patterns and residents' perceptions of control in test ordering. METHOD In a 2007 cohort study of 2,066 patients cared for by 85 interns, 56 residents, and 27 attendings on the University of Pennsylvania general medical hospitalist ser...

background: increased costs and mortality associated with inappropriate blood transfusions have led to investigations about blood request and blood transfusion techniques. we investigated the transfusion status in patients who underwent orthopedic surgery in poursina hospital (rasht, iran) to optimizing blood usage and determine if a scheduled transfusion program for every orthopedic surgery co...

OBJECTIVE To calculate the variable costs involved with the process of delivering erythropoiesis stimulating agents (ESA) in European dialysis practices. METHODS A conceptual model was developed to classify the processes and sub-processes followed in the pharmacy (ordering from supplier, receiving/storing/delivering ESA to the dialysis unit), dialysis unit (dose determination, ordering, recei...

We consider the periodic-review, single-location, single-product, production/inventory control problem under non stationary demand and service-level constraints. The product is perishable and has a fixed shelf life. Costs comprise fixed ordering costs and inventory holding costs. For this inventory system we discuss a number of control policies that may be adopted. For one of these policies, we...

This paper deals with the problem of coordinated ordering of items having deterministic but time varying demands where there is a common ordering cost if one or more of these items are ordered in addition to individual items ordering costs. To solve this NP-hard problem we propose a number of heuristics. Also we report on a comparative study that we undertaken to evaluate the relative performan...

This paper considers a single-echelon, continuous review, inventory system with a warehouse facing compound Poisson customer demand. The replenishment lead-time is constant. Demand that cannot be met directly is backordered. There are standard linear holding and backorder costs but no set-up or ordering cost. It is assumed that the demand process starts at a certain given time. Consequently, be...