The Cost Function of a Two-Level Inventory System with identical retailers benefitting from Information Sharing

This paper investigates a two-echelon inventory system with a central warehouse and N (N > 2) retailers managed by a centralized information-sharing mechanism. In particular, the paper mathematically models an easy-to-implement inventory control system that facilitates making use of information. Some assumptions of the paper include: a) constant delivery time for retailers and the central warehouse and b) Poisson demand with identical rates for retailers. The inventory policy comprises continuous review (R,Q)-policy on the part of retailers and triggering the system with m batches (of a given size Q) at the central warehouse. Besides, the central warehouse monitors retailers' inventory and may order batches sooner than retailers' reorder point, when their inventory position reaches R + s. An earlier study proposed the policy and its cost function approximation. This paper derives an exact mathematical model of the cost function for the aforementioned problem

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

Study of Canola Meal Extract in the Synthesis of Lipids by Mortierella alpina

Quality and cost-effective raw materials and the utilization of agriculture by-products with potential quality attributes and negligible commercial value can be supplemented in several microbial processing industries. Canola meal (CM), a by-product of canola processing, has an excellent nutritional profile composed of protein, carbohydrates, vitamins, and minerals, and could serve as a potential candidate for microbial culture media. Saskatchewan, as a global leader in canola production, has plans for upscaling its canola processing facilities. The efficient utilization of canola meal extract (CME) in the production of lipids and polyunsaturated fatty acids, such as arachidonic acid (ARA) has the potential to serve as valuable ingredients or base chemicals for food, feed, and nutraceutical industries. This current study focused on the incorporation of alkaline extract (AE) and subcritical extract (SE) of CM in a culture medium of an oleaginous fungus, Mortierella alpina ATCC 32223, by replacing conventional yeast extract (YE) at a level of 50 % and 100 %. Extraction for AE was conducted at 75 °C with a pH of 10.5, while for SE, it was carried out at 160 °C without pH control. Initial trials were conducted to examine the effect of aeration at a level of 0.5 to 2.0 vvm on fungal growth and it was found that increasing aeration rate increased fungal growth rate from 0.16 day-1 to 0.39 day-1. Also, the ARA percentage in the lipid increased from 10.39% to 21.86%. It became evident that ARA production was positively correlated with biomass accumulation and its lipid content. During the replacement of YE by CME, it was observed that the 100% substitution of YE by CME yielded growth results similar to that of the control, which employed standard media containing YE. Moreover, AE- and SE-supplemented media exhibited a higher ARA accumulation of 144.91 mg/L and 165.8 mg/L, respectively, in comparison to standard media (124.87 mg/L). Interestingly, when glucose was omitted from the culture, media supplemented with 100% AE performed better as compared to standard media. However, the limitation of glucose had an adverse effect on both the growth and lipid content of the culture

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

Study of Canola Meal Extract in the Synthesis of Lipids by Mortierella alpina

Quality and cost-effective raw materials and the utilization of agriculture by-products with potential quality attributes and negligible commercial value can be supplemented in several microbial processing industries. Canola meal (CM), a by-product of canola processing, has an excellent nutritional profile composed of protein, carbohydrates, vitamins, and minerals, and could serve as a potential candidate for microbial culture media. Saskatchewan, as a global leader in canola production, has plans for upscaling its canola processing facilities. The efficient utilization of canola meal extract (CME) in the production of lipids and polyunsaturated fatty acids, such as arachidonic acid (ARA) has the potential to serve as valuable ingredients or base chemicals for food, feed, and nutraceutical industries. This current study focused on the incorporation of alkaline extract (AE) and subcritical extract (SE) of CM in a culture medium of an oleaginous fungus, Mortierella alpina ATCC 32223, by replacing conventional yeast extract (YE) at a level of 50 % and 100 %. Extraction for AE was conducted at 75 °C with a pH of 10.5, while for SE, it was carried out at 160 °C without pH control. Initial trials were conducted to examine the effect of aeration at a level of 0.5 to 2.0 vvm on fungal growth and it was found that increasing aeration rate increased fungal growth rate from 0.16 day-1 to 0.39 day-1. Also, the ARA percentage in the lipid increased from 10.39% to 21.86%. It became evident that ARA production was positively correlated with biomass accumulation and its lipid content. During the replacement of YE by CME, it was observed that the 100% substitution of YE by CME yielded growth results similar to that of the control, which employed standard media containing YE. Moreover, AE- and SE-supplemented media exhibited a higher ARA accumulation of 144.91 mg/L and 165.8 mg/L, respectively, in comparison to standard media (124.87 mg/L). Interestingly, when glucose was omitted from the culture, media supplemented with 100% AE performed better as compared to standard media. However, the limitation of glucose had an adverse effect on both the growth and lipid content of the culture

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

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