Surface degradation of nanocrystalline zirconia dental implants

Yttria-stabilized zirconia prepared by hot isostatic pressing represents attractive material for biomedical applications. In this work the degradation of yttria-stabilized zirconia dental implants abutments due to the tetragonal to monoclinic phase transformation after one year of clinical use was studied in detail. Microstructural characterization by Electron Back Scattering Diffraction was successfully applied. The amount and distribution of the monoclinic phase, the grain-size distribution and crystallographic orientations between tetragonal and monoclinic crystals in 3 mol.% yttria-stabilized polycrystalline zirconia were determined in two different types of abutments currently used in clinical practice. Clear crystallographic orientation relationship between parent tetragonal and daughter monoclinic phase was clearly observed. An important and novel conclusion is that no substantial bulk degradation of 3Y-TZP dental implant abutments was detected after 1 year of clinical use

Revenue sharing contract for a VMI with one for one period policy

In this article, we design a revenue-sharing contract to coordinate inventory control decisions in a serial supply chain consisting of one supplier, one vendor, and one retailer. We assume that the retailer faces Poisson demand and his unsatisfied demands will be lost. The retailer applies one-for-one period policy in which he constantly places an order for one unit of product to the vendor in a predetermined time interval which results in a deterministic demand for the vendor. Vendor orders the required quantity from supplier which will be immediately received at the vendor’s warehouse. Solution procedures are developed to find the equilibrium in the vendor managed inventory program with a revenue-sharing contract. Furthermore, we obtain the optimal order cycle for the retailer and the vendor which minimizes the supply chain’s total cost

Introducing a new ordering policy in a two-echelon inventory system with Poisson demand

International audienceIn this paper we introduce a new ordering policy for inventory control in a two-echelon inventory system consisting of one central warehouse and a number of non-identical retailers. The warehouse uses a modified one-for-one policy, but the retailers apply a new policy which is different from the traditional inventory policies described in the literature of inventory and production control systems. In this system, each retailer constantly places an order for one unit of product to the central warehouse in a pre-determined time interval; i.e., the time interval between any two consecutive orders from each retailer is a fixed number and the quantity of each order is one. We then show how the inventory costs can be determined for this system. The most important advantage of this policy is that the warehouse is facing a uniform and deterministic demand originated by each retailer. Furthermore, a numerical example is provided to compare the performance of the new policy with the performance of the one-for-one policy in a two echelon inventory system in terms of the total system cost

An algorithm for the determination of the economic order quantity in a two-level supply chain with transportation costs: comparison of decentralized with centralized decision

14 pagesInternational audienceThis paper considers a two-level supply chain consisting of one warehouse and one retailer. In this model we determine the optimal ordering policy according to inventory and transportation costs. We assume that the demand rate by the retailer is known. Shortages are allowed neither at the retailer nor at the warehouse. We study this model in two cases; decentralized and centralized. In the decentralized case the retailer and the warehouse independently minimize their own costs; while in the centralized case the warehouse and the retailer are considered as a whole firm. We propose an algorithm to find economic order quantities for both the retailer and the warehouse which minimize the total system cost in the centralized case. The total system cost contains the holding and ordering costs at the retailer and the warehouse as well as the transportation cost from the warehouse to the retailer. The application of this model into the pharmaceutical downstream supply chain of a public hospital allows obtaining significant savings. By numerical examples, the costs are computed in MATLAB© to compare the costs in the centralized case with decentralized one and to propose a saving-sharing mechanism through quantity discount

Inventory Cost Evaluation Under VMI Program with Lot Splitting

This paper aims to evaluate inventory cost of a Two-echelon serial supply chain system under vendor managed inventory program with stochastic demand, and examine the effect of environmental factors on the cost of overall system. For this purpose, we consider a two-echelon serial supply chain with a manufacturer and a retailer. Under Vendor managed inventory program, the decision on inventory levels are made by manufacturer centrally. In this paper, we assume that the manufacturer monitors inventory levels at the retailer location and replenishes retailer's stock under (r, n, q) policy moreover, the manufacturer follows make-to-order strategy in order to respond retailer's orders. In the other word, when the inventory position at the retailer reaches reorder point, r, the manufacturer initiates production of Q=nq units with finite production rate, p. The manufacturer replenishes the retailer's stock with replenishment frequency n, and the complete batch of q units to the retailer during the production time. We develop a renewal reward model for the case of Poisson demand, and drive the mathematical formula of the long run average total inventory cost of system under VMI. Then, by using Monte Carlo simulation, we examine the effect of environmental factors on the cost of overall system under VMI

Economic Order Quantity in a Centralized Two-Level Supply Chain with Transportation Cost

International audienceThis paper considers a two-level supply chain consisting of one warehouse and one retailer. Unlike the most similar models which determine the optimal ordering policy according to inventory cost only, in this model, we also consider the transportation cost. We assume that the demand rate at the retailer is known and the demand is confined to a single item. Shortages are allowed neither at the retailer nor at the warehouse. The objective is to find the economic order quantities for both the retailer and the warehouse which minimize the total cost. That is, the sum of the holding and ordering cost at the retailer and warehouse as well as the transportation cost from warehouse to retailer. Numerical results show savings can be made by this model in comparison to the model of optimal ordering policy in which the transportation cost is not considered

A New replenishment Policy in a Two-echelon Inventory System with Stochastic Demand

International audienceIn this paper we consider a two-echelon inventory system consisting of one central warehouse and a number of non-identical retailers. The warehouse uses a regular one-for-one policy to replenish its inventory, but the retailers apply a new policy that is each retailer orders one unit to central warehouse in a pre-determined time interval. The most advantage of this policy is that the retailers' orders, which constitute warehouse demand, are deterministic. For this system we show how the inventory costs can be evaluated. By the numerical examples we compare our policy with one-for-one policy