Planning and Scheduling Decisions in Supply Chains with Multiple Supply Modes: An Integrated Approach

We address the problem of jointly determining shipment planning and scheduling decisions with the presence of multiple shipment modes. We consider long lead time, less expensive sea shipment mode, and short lead time but expensive air shipment modes. Existing research on multiple shipment modes largely address the short term scheduling decisions only. Motivated by an industrial problem where planning decisions are independent of the scheduling decisions, we investigate the benefits of integrating the two sets of decisions. We develop sequence of mathematical models to address the planning and scheduling decisions. Preliminary computational results indicate improved performance of the integrated approach over some of the existing policies used in real-life situations.Singapore-MIT Alliance (SMA

A Model for Contingent Manpower Planning: Insights from a High Clock Speed Industry

Intense competitive pressures have led to compressed product life cycles and frequent introduction of new products. This creates demand volatility and a consequent pressure on manufacturing to meet this variable demand. In this paper we model the manpower planning issues for a computer manufacturer during the product introduction phase when a quick ramp-up of production to meet rapidly increasing demand is a key requirement. A mix of permanent and contingent workers with different skill sets is considered. Some important issues addressed in this research are (a) how to assign workers with different skills to maximize production (b) what is the induction rate of contingent workers to achieve the desired ramp-up and (c) what are the key decision factors that impact manufacturing performance An LP model is proposed to minimize overall costs subject to complex scheduling, skills, and learning rate requirements. Our analysis indicates that cost of induction of contingent workers, overtime cost premium, and the amount of overtime have significant impact on performance. The findings of the study will be useful to managers in planning and allocation of workers of different skills to various manufacturing processes and to determine the optimal number of contingent workers to induct.Singapore-MIT Alliance (SMA

An Extension to the Tactical Planning Model for a Job Shop: Continuous-Time Control

We develop an extension to the tactical planning model (TPM) for a job shop by the third author. The TPM is a discrete-time model in which all transitions occur at the start of each time period. The time period must be defined appropriately in order for the model to be meaningful. Each period must be short enough so that a job is unlikely to travel through more than one station in one period. At the same time, the time period needs to be long enough to justify the assumptions of continuous workflow and Markovian job movements. We build an extension to the TPM that overcomes this restriction of period sizing by permitting production control over shorter time intervals. We achieve this by deriving a continuous-time linear control rule for a single station. We then determine the first two moments of the production level and queue length for the workstation.Singapore-MIT Alliance (SMA

Multi-Item Single-Vendor-Single-Buyer Problem with Consideration of Transportation Quantity Discount

This paper deals with the problem of shipping multiple commodities from a single vendor to a single buyer. Each commodity is assumed to be constantly consumed at the buyer, and periodically replenished from the vendor. Furthermore, these replenishments are restricted to happen at discrete time instants, e.g., a certain time of the day or a certain day of the week. At any such time instant, transportation cost depends on the shipment quantity according to certain discount scheme. Specifically, we consider two transportation quantity discount schemes: LTL (less-than-truckload) incremental discount and TL (truckload) discount. For each case, we develop MIP (mixed integer programming) mathematical model whose objective is to make an integrated replenishment and transportation decision such that the total system cost is minimized. We also derive optimal solution properties and give numerical studies to investigate the problem.Singapore-MIT Alliance (SMA

Logistics Network Design with Differentiated Delivery Lead-Time: Benefits and Insights

Most logistics network design models assume exogenous customer demand that is independent of the service time or level. This paper examines the benefits of segmenting demand according to lead-time sensitivity of customers. To capture lead-time sensitivity in the network design model, we use a facility grouping method to ensure that the different demand classes are satisfied on time. In addition, we perform a series of computational experiments to develop a set of managerial insights for the network design decision making process.Singapore-MIT Alliance (SMA

DSS Model for Profit Maximization at Customer Enquiry Evaluation Stage

This paper presents an optimal method and a heuristic approach which aims at maximizing the profit when responding to a set of customer enquiries under limited capacity. The model takes into consideration the quantity of available-to-promise (ATP) which measures the capability to fill customer orders, along with enquiry quantity and product price. The optimal method and the heuristic approach are tested using ATP, product price and enquiry quantity each at their different levels. From the example conducted, it is found that (1) the optimal model can help to make appropriate decision for selecting a subset of enquiries, and (2) the heuristic approach can produce a result within 5% from the optimum achieved by optimal method for most parameter settings.Singapore-MIT Alliance (SMA

Framework to Manage Customer Enquiries for SMEs

For most Smaller Manufacturing Enterprises (SMEs), how to manage customer enquiries at the customer enquiry stage is of great importance to maintain the competitive advantage and secure future customer orders. A lack of co-ordination between marketing/sales and production at this stage often leads to confirmed orders being delivered later than promised and/or being produced at a loss. In the paper, the problems and the solutions for managing customer enquiries faced by many SMEs are addressed. A general process for dealing with customer enquiries at the customer enquiry stage and a corresponding DSS approach are presented in detailed. The SMEs would benefit from the proposed DSS in which the considerations of current material and production capacity are given to the customer enquiry management process.Singapore-MIT Alliance (SMA

Fulfillment of Rush Customer Orders under Limited Capacity

Customer demand fulfillment is the business process within a company that determines how the customer demand is fulfilled. A rush order is the last minute customer order after the production plan of a company has been concluded. For these rush orders, appropriate and reasonable response is imperative as it could put strain on customer relationship and services. A good and positive response could help the company to build and retain its market share in today’s highly competitive markets. A model aims at decreasing the product inventory cost is proposed in this paper. In this model, the prioritized fulfillment sequence of rush customer demands can be searched in terms of the product inventory cost. The paper focuses on two main issues: the available-to-promise (ATP) based fulfillment ability and the prioritized fulfillment of customer demands. For ATP based fulfillment, a dynamic bill-of-material (BOM) is proposed to handle the complicated issues of BOM, BOM explosion and production capacity. By means of dynamic BOM, material availability as well as production capacity can be taken into consideration simultaneously and efficiently. Two methods, mathematical optimization and heuristic algorithm, are constructed and elaborated on in the second issue. The proposed model allows companies to prioritize customer rush orders in terms of product inventory cost.Singapore-MIT Alliance (SMA

A Pilot Genome-Wide Analysis Study Identifies Loci Associated With Response to Obeticholic Acid in Patients With NASH

A significantly higher proportion of patients with nonalcoholic steatohepatitis (NASH) who received obeticholic acid (OCA) had histological improvement relative to placebo in the FLINT (farnesoid X nuclear receptor ligand obeticholic acid for noncirrhotic, NASH treatment) trial. However, genetic predictors of response to OCA are unknown. We conducted a genome‐wide association study (GWAS) in FLINT participants to identify variants associated with NASH resolution and fibrosis improvement. Genotyping was performed using the Omni2.5 content GWAS chip. To avoid false positives introduced by population stratification, we focused our GWAS on white participants. Six regions on chromosomes 1, 4, 6, 7, 15, and 17 had multiple single nucleotide polymorphisms (SNPs) with suggestive association (P < 1 × urn:x-wiley:2471254X:media:hep41439:hep41439-math-0001) with NASH resolution. A sentinel SNP, rs75508464, near CELA3B on chromosome 1 was associated with NASH resolution, improvement in the nonalcoholic fatty liver disease activity score, portal inflammation, and fibrosis. Among individuals carrying this allele, 83% achieved NASH resolution with OCA compared with only 33% with placebo. Eight regions on chromosomes 1, 2, 3, 11, 13, and 18 had multiple SNPs associated with fibrosis improvement; of these, rs12130403 near TDRD10 on chromosome 1 was also associated with improvement in NASH and portal inflammation, and rs4073431 near ANO3 on chromosome 11 was associated with NASH resolution and improvement in steatosis. Multiple SNPs on chromosome 11 had suggestive association with pruritus, with rs1379650 near ANO5 being the top SNP. Conclusion: We identified several variants that may be associated with histological improvement and pruritus in individuals with NASH receiving OCA. The rs75508464 variant near CELA3B may have the most significant effect on NASH resolution in those receiving OCA