the quasi-periodic order is a type of geometrical order in universe which is observed in the structure of quasi-crystals. this order was first introduced in mathematics in 1973 by roger penrose and then discovered in quasi-crystals in 1984 while spreading in mathematics, chemistry and physics. the paper professor james lu et al published in science magazine in 2007 illustrated that iranians wer...

in classic inventory control system, we assume that purchasing cost should be paid at time of delivery. but sometimes in order to encourage retailer to increase his order, postpond payment is provided by supplier as an incentive policy for retailer. in this paper a periodic inventory control model is invetigated in which the period between two consecutive replenishmnet is a random variable. in ...

In this paper we consider the inventory problem with backorder such that both order and total demand quantities are triangular fuzzy numbers Q̃ = (q1, q0, q2), and R̃ = (r1, r0, r2) respectively, where q1 = q0−Δ1, q2 = q0+Δ2,r1 = r0−Δ3, r2 = r0+Δ4 such that 0 < Δ1 < q0, 0 < Δ2, 0 < Δ3 < r0, 0 < Δ4. Let s denote the maximum inventory quantity. Under conditions s ≤ q1 < q0 < q2 < r1 < r0 < r2, we f...

R etailers must constantly strive for excellence in operations; extremely narrow profit margins leave little room for waste and inefficiency. This article reports a retailer’s challenge to balance transportation, shelf space, and inventory costs. A retailer sells multiple products with stochastic demand. Trucks are dispatched from a warehouse and arrive at a store with a constant lead time. Eac...

Certain inventory items are living organisms, for example livestock, and are therefore capable of growing during the replenishment cycle. These items often serve as various saleable food items downstream in supply chains. The purpose of this paper is to develop a lot sizing model for growing items if the supplier of the items offers incremental quantity discounts. A mathematical model is derive...

In most stochastic inventory models, such as continuous review models and periodic review models, it has been assumed that the stockout period during a cycle is small enough to be neglected so that the average number of cycles per year can be approximated as D/Q, where D is the average annual demand and Q is the order quantity. This assumption makes the problem more tactable, but it should not ...

In most stochastic inventory models, such as continuous review models and periodic review models, it has been assumed that the stockout period during a cycle is small enough to be neglected so that the average number of cycles per year can be approximated as D/Q, where D is the average annual demand and Q is the order quantity. This assumption makes the problem more tactable, but it should not ...

The authors propose a new method, the Helfand-moment method, to compute the shear viscosity by equilibrium molecular dynamics in periodic systems. In this method, the shear viscosity is written as an Einstein-type relation in terms of the variance of the so-called Helfand moment. This quantity is modified in order to satisfy systems with periodic boundary conditions usually considered in molecu...

‎this paper proposes a multi-supplier multi-product inventory model in which the suppliers have unlimited production capacity, allow delayed payment, and offer either an all-unit or incremental discount. the retailer can delay payment until after they have sold all the units of the purchased product. the retailer’s warehouse is limited, but the surplus can be stored in a rented warehouse at a...