On the efficiency of optimal algorithms for the joint replenishment problem: a comparative study

In this paper we proposed an efficient algorithm to solve the joint replenishment problem to optimality. We perform a computational study to compare the performance of the proposed algorithm with the best one reported in Viswanathan [6]. The study reveals that for large minor set-up costs and moderate major set-up cost, our algorithm outperforms the latter.inventory;joint replenishment;deterministic demand

Controlling inventories in a supply chain: a case study

This article studies specific aspects of the joint replenishment problem in a real supply chain setting. Particularly we analyze the effect on inventory performance of having minimum order quantities for the different products in the joint order, given a complex transportation cost structure. The policies suggested have been tested in a simulation model with real data.Inventory;Supply chain management;Minimum order quantities;Joint replienishment

Generalized Solutions for the joint replenishment problem with correction factor

In this paper we give a complete analysis of the joint replenishment problem (JRP) under constant demands and continuous time. We present a solution method for the JRP when a correction is made for empty replenishments, and we test the solution procedures with real data. We show that the solutions obtained differ from the standard JRP when no correction is made in the cost function. We further show that the JRP with correction outperforms independent ordering. Additional numerical experiments are presented.inventory;joint replenishment;correction factor

New Bounds for the Joint Replenishment Problem: Tighter, but not always better

In this paper we present new bounds on the basic cycle time for optimal methods to solve the JRP. They are tighter than the ones reported in Viswanathan [7]. We carry out extensive numerical experiments to compare them and to investigate the computational complexity.computational complexity;joint replenishment problem;bounds

Determination of recovery effort for a probabilistic recovery system under various inventory control policies

In this study we investigate the desired level of recovery under various inventory control policies when the success of recovery is probabilistic. Recovery process is modelled as a single stage operation and recovery effort is represented by the expected time spent for it. The effect of increasing recovery effort on the success probability together with unit cost of the operation is included by assuming general forms of dependencies. The desired level of recovery is investigated under four inventory control policies for a wide range of system parameters. In this article, we present our computational results and their managerial implications.inventory control;probabilistic recovery

Molecular Hydrogen Kinematics in Cepheus A

We present the radial velocity structure of the molecular hydrogen outflows associated to the star forming region Cepheus A. This structure is derived from doppler shift of the H_2 v=1-0 S(1) emission line obtained by Fabry-Perot spectroscopy. The East and West regions of emission, called Cep A(E) and Cep A(W), show radial velocities in the range -20 to 0 km/s with respect to the molecular cloud. Cep A(W) shows an increasing velocity with position offset from the core indicating the existence of a possible accelarating machanism. Cep A(E) has an almost constant mean radial velocity of -18 km/s along the region although with a large dispersion in velocity, indicating the possibility of a turbulent outflow. A detailed analysis of the Cep A(E) region shows evidence for the presence of a Mach disk on that outflow. Also, we argue that the presence of a velocity gradient in Cep A(W) is indicative of a C-shock in this region. Following Riera et al. (2003), we analyzed the data using wavelet analysis to study the line width and the central radial velocity distributions. We found that both outflows have complex spatial and velocity structures characteristic of a turbulent flow.Comment: 24 pages, 15 figure

OH+ in Diffuse Molecular Clouds

Near ultraviolet observations of OH+ and OH in diffuse molecular clouds reveal a preference for different environments. The dominant absorption feature in OH+ arises from a main component seen in CH+ (that with the highest CH+/CH column density ratio), while OH follows CN absorption. This distinction provides new constraints on OH chemistry in these clouds. Since CH+ detections favor low-density gas with small fractions of molecular hydrogen, this must be true for OH+ as well, confirming OH+ and H2O+ observations with the Herschel Space Telescope. Our observed correspondence indicates that the cosmic ray ionization rate derived from these measurements pertains to mainly atomic gas. The association of OH absorption with gas rich in CN is attributed to the need for high enough density and molecular fraction before detectable amounts are seen. Thus, while OH+ leads to OH production, chemical arguments suggest that their abundances are controlled by different sets of conditions and that they coexist with different sets of observed species. Of particular note is that non-thermal chemistry appears to play a limited role in the synthesis of OH in diffuse molecular clouds.Comment: 15 pages, 4 figures, to appear in ApJ Letter