BACKGROUND Adequate participant recruitment is vital to the conduct of a clinical trial. Projected recruitment rates are often over-estimated, and the time to recruit the target population (accrual period) is often under-estimated. METHODS This report illustrates three approaches to estimating the accrual period and applies the methods to a multi-center, randomized, placebo controlled trial u...

Supply chain management is taken into account as an inseparable component in satisfying customers' requirements. This paper deals with the distribution network design (DND) problem which is a critical issue in achieving supply chain accomplishments. A capable DND can guarantee the success of the entire network performance. However, there are many factors that can cause fluctuations in input dat...

The paper focuses on multi-period aspects of risk functionals. It discusses properties, provides dual representations and offers methods for constructing multiperiod risk functionals. On the way, existence results and representations for conditional risk mappings are derived. In particular, conditional, multi-period and nested versions of the average value-at-risk are given. Finally, the import...

This paper considers a multi-port and multi-period container planning problem of shipping companies that use both standard and foldable containers. A company must decide which number of empty containers of each type to purchase and reposition at each port within a defined period to minimize the total purchasing, repositioning, and storage costs. Wedevelop amodel to optimally allocate both folda...

We address a novel integrated maintenance and production scheduling problem in a multi-machine and multi-period production system, considering maintenance as a long-term decision. Deterioration of machines over time decreases production capacity. Since maintenance activities improve machine conditions, increasing production capacity, but also take time that cannot be used for production, the ch...

We study a minimal model for the flow of granular material on a conveyor belt consisting of a staircase-like array of K vertically vibrated compartments. Applying a steady inflow rate Q to the top compartment, we determine the maximum value Qcr(K) for which a continuous flow through the system is possible. BeyondQcr(K), which depends on the vibration strength and the dimensions of the system, a...

This paper presents a multi-period inventory lot-sizing scenario, where there are multiple products and multiple suppliers. We consider a situation where the demand of multiple discrete products is known over a planning horizon. Each of these products can be sourced from a set of approved suppliers, a supplier-dependent transaction cost applying for each period in which an order is placed on a ...