Hospitalization data were extracted for Marines wounded in Vietnam from 1965 to 1969 to examine the echelon flow of treatment care for different types of injuries. The inter-echelon movement of each patient who was hospitalized at an echelon II or III facility was tracked until the treatment was completed or until the patient was moved to a facility in the continental United States. Results sho...

The delivery of freight from its origin to its destination is often managed through one or more intermediate facilities where storing, merging and consolidation activities are performed. This type of distribution systems is commonly called multi-echelon, where each echelon refers to one level of the distribution network. Multi-echelon distribution systems are often considered by public administ...

In allusion to such problems as low accuracy and long convergence time in traditional two-echelon vehicle routing optimization algorithm, a Memetic algorithm (QDEMA) based on Q learning theory and differential evolution is proposed in this article to solve above problems. Firstly, it is necessary to research the two-echelon vehicle routing optimization problem and adopt the optimal segmentation...

This paper studies a two-echelon supply chain with stochastic and discrete consumer demand, batch order quantities, periodic inventory review, and deterministic transportation times. Reorder point policies manage inventories at every location. Average inventory, backorders and fill rates are evaluated exactly for each location. Safety stock is evaluated exactly at the lower echelon and a good a...

HYPOTHESIS The required sample size of a prospective randomized trial comparing standard pancreaticoduodenectomy with pancreaticoduodenectomy plus extended lymphadenectomy for pancreatic adenocarcinoma is prohibitively large, making such a trial infeasible. DESIGN Retrospective cohort study. SETTING Comprehensive cancer center. PATIENTS We identified 158 patients who underwent pancreatico...

BACKGROUND The need for routine axillary lymph node dissection (ALND) in patients with invasive breast cancer and low-volume sentinel node (SN) involvement is questionable. Accurate prediction of second echelon lymph node involvement could identify those patients most likely to benefit from ALND. METHODS A consecutive series of 317 patients with invasive breast cancer and a tumor positive axi...

In this paper, we study a multi-echelon uncapacitated lot-sizing problem in series (mULS), where the output of the intermediate echelons has its own external demand, and is also an input to the next echelon. We propose a polynomial-time dynamic programming algorithm, which gives a tight, compact extended formulation for the two echelon case (2-ULS). Next, we present a family of valid inequaliti...

The Two-Echelon Routing Problem constitutes a class of combinatorial optimization problems with applications in many different fields such as city logistic planning, intermodal transportation, postal and parcel delivery distribution systems and so on. This thesis contains: a survey of the main contributions related to the two-echelon routing, focusing on the Two-Echelon Location Routing Problem...

An arborescent distribution system is a multi-level system in which each installation receives input from a unique immediate predecessor and supplies one or more immediate successors. In this paper, it is shown that a distribution system with an arborescent structure can also be modelled using an echelon stock concept where at any instant the total echelon holding cost is accumulated at the sam...

Freight transportation constitutes one of the main activities that influences economy and society, as it assures a vital link between suppliers and customers and is represents a major source of employment. Multi-echelon distribution is one of the most common strategies adopted by the transportation companies in an aim of cots reduction. Although vehicle routing problems are very common in opera...