Singa Wang Chiu

Intra-supply chain system with multiple sales locations and quality assurance

The emergence of the global economy has transformed the interdepartmental nature of a transnational enterprise into a highly collaborative oriented team. This transformation enables the enterprise to lower its transaction and coordination costs and increase its competitive advantage in the global market. This study investigates such a so-called intra-supply chain system that exists in present-day transnational firms, wherein a single production unit manufactures products to meet the demands of multiple regional sales offices and incorporates quality assurance in its production. The objective of the present study is to determine an optimal production quantity and shipment policy that minimizes the integrated production-inventory-delivery costs for the intra-supply chain system. In this study, considerations related to a products quality assurance include inspection for quality, rework of defective items and failure in rework. Delivery of the finished products starts when quality of the entire production lot is assured. Multi-shipment policy is used to synchronously transport finished items to multiple locations for satisfying customer demands in each cycle. Mathematical modeling along with Hessian matrix equations is employed to solve the proposed intra-supply chain system. A numerical example with a discussion and cost-benefit analysis of outsourcing work to an external distributor is presented to demonstrate the practical applicability of the obtained results.

On intra-supply chain system with an improved distribution plan, multiple sales locations and quality assurance

Transnational companies, operating in extremely competitive global markets, always seek to lower different operating costs, such as inventory holding costs in their intra- supply chain system. This paper incorporates a cost reducing product distribution policy into an intra-supply chain system with multiple sales locations and quality assurance studied by [Chiu et al., Expert Syst Appl, 40:2669–2676, (2013)]. Under the proposed cost reducing distribution policy, an added initial delivery of end items is distributed to multiple sales locations to meet their demand during the production unit’s uptime and rework time. After rework when the remaining production lot goes through quality assurance, n fixed quantity installments of finished items are then transported to sales locations at a fixed time interval. Mathematical modeling and optimization techniques are used to derive closed-form optimal operating policies for the proposed system. Furthermore, the study demonstrates significant savings in stock holding costs for both the production unit and sales locations. Alternative of outsourcing product delivery task to an external distributor is analyzed to assist managerial decision making in potential outsourcing issues in order to facilitate further reduction in operating costs.

Mathematical modeling of a multi‑product EMQ model with an enhanced end items issuing policy and failures in rework

AbstractnThis study uses mathematical modeling to examine a multi-product economic manufacturing quantity (EMQ) model with an enhanced end items issuing policy and rework failures. We assume that a multi-product EMQ model randomly generates nonconforming items. All of the defective are reworked, but a certain portion fails and becomes scraps. When rework process ends and the entire lot of each product is quality assured, a cost reduction nxa0+xa01 end items issuing policy is used to transport finished items of each product. As a result, a closed-form optimal production cycle time is obtained. A numerical example demonstrates the practical usage of our result and confirms a significant savings in stock holding and overall production costs as compared to that of a prior work (Chiu et al. in J Sci Ind Res India, 72:435–440 2013) in the literature.

Incorporating a cost lessening distribution policy into a production system with random scrap rate

This paper incorporates a cost lessening product distribution policy into a production system with random scrap rate, with the purpose of cutting down producer’s inventory holding cost. The present study reconsiders a production lot sizing problem examined by a prior paper and improves its replenishment lot size solution in terms of stock holding cost reduction. Anxa0n+1 product distribution policy is used here in lieu of thexa0nxa0multi-delivery plan adopted in prior study. Under the proposed policy, an initial installment of finished products is delivered to customer for satisfying the product demand during producer’s production uptime. Then, fixed quantityxa0nxa0installments of finished items are delivered to customer at a fixed interval of time at the end of uptime. Mathematical modeling is used and as a result, the optimal production lot size solution is derived. A numerical example with analysis is provided to show practical usage of research result and demonstrate its significant savings in holding costs. n n xa0 n n Key words:xa0Optimization, production system, replenishment lot size, multiple deliveries, scrap.

Producer–retailer integrated EMQ system with machine breakdown, rework failures, and a discontinuous inventory issuing policy

This study develops two extended economic manufacturing quantity (EMQ)-based models with a discontinuous product issuing policy, random machine breakdown, and rework failures. Various real conditions in production processes, end-product delivery, and intra-supply chains such as a producer–retailer integrated scheme are examined. The first model incorporates a discontinuous multi-delivery policy into a prior work (Chiu et al. in Proc Inst Mech Eng B J Eng 223:183–194, 2009) in lieu of their continuous policy. Such an enhanced model can address situations in supply chain environments, where finished products are transported to outside retail stores (or customers). The second model further combines retailer’s stock holding costs into the first model. This extended EMQ model is applicable in situations in present-day manufacturing firms where finished products are distributed to company’s own retail stores (or regional sales offices) and stocked there for sale. Two aforementioned extended EMQ models are investigated, respectively. Mathematical modeling along with iterative algorithms are employed to derive the optimal production run times that minimize the expected total system costs, including the costs incurred in production units, transportation, and retail stores, for these integrated EMQ systems. Numerical examples are provided to demonstrate the practical application of the research results.

Optimization of a Multi–Product Intra-Supply Chain System with Failure in Rework

Globalization has created tremendous opportunities, but also made business environment highly competitive and turbulent. To gain competitive advantage, management of present-day transnational firms always seeks options to trim down various transaction and coordination costs, especially in the area of controllable intra-supply chain system. This study investigates a multi–product intra-supply chain system with failure in rework. To achieve maximum machine utilization, multiple products are fabricated in succession on a single machine. During the process, production of some defective items is inevitable. Reworking of nonconforming items is used to reduce the quality cost in production and achieving the goal of lower overall production cost. Because reworks are sometimes unsuccessful, failures in rework are also considered in this study. Finished goods for each product are transported to the sales offices when the entire production lot is quality assured after rework. A multi-delivery policy is used, wherein fixed quantity n installments of the finished lot are transported at fixed intervals during delivery time. The objective is to jointly determine the common production cycle time and the number of deliveries needed to minimize the long–term expected production–inventory–delivery costs for the problem. With the help of a mathematical model along with optimization technique, the optimal production–shipment policy is obtained. We have used a numerical example to demonstrate applicability of the result of our research.

Replenishment lot sizing with an improved issuing policy and imperfect rework derived without derivatives

This study uses an alternative approach to reexamine a replenishment lot size problem with discontinuous issuing policy and imperfect rework. A straightforward approach in terms of algebraic derivation is proposed instead of conventional method with the need of applying first-order and second-order differentiations to system cost function for proof of convexity before derivation of the optimal lot size. The research result obtained in this study is identical to that in Lee et al. (2011), where they adopted conventional method to solve the problem. The proposed algebraic approach is helpful for practitioners who may have insufficient knowledge of differential calculus to understand with ease such a real life vendor-buyer integrated problem.

Solving multi-customer FPR model with quality assurance and discontinuous deliveries using a two-phase algebraic approach.

A multi-customer finite production rate (FPR) model with quality assurance and discontinuous delivery policy was investigated in a recent paper (Chiu et al. in J Appl Res Technol 12(1):5–13, 2014) using differential calculus approach. This study employs mathematical modeling along with a two-phase algebraic method to resolve such a specific multi-customer FPR model. As a result, the optimal replenishment lot size and number of shipments can be derived without using the differential calculus. Such a straightforward method may assist practitioners who with insufficient knowledge of calculus in learning and managing the real multi-customer FPR systems more effectively.

A two-phase approach for jointly determining the lot size and delivery policy in a vendor-buyer integrated system with rework

This paper presents a two-phase algebraic approach for jointly determining the lot size and delivery policy in a vendor-buyer integrated system with rework. Conventional method uses the diff erential calculus for solving production-shipment problem with the need for proving optimality fi rst on the system cost function. This study proposes a two-phase algebraic solution procedure to derive the optimal lot size as well as optimal number of deliveries without using derivatives. The proposed approach enables practitioners who maybe without suff icient knowledge of calculus to understand such a specifi c real world problem with ease

Determining optimal lot size problem with rework and multiple deliveries using algebraic approach

This paper presents an algebraic approach for determining optimal lot size for economic production quantity (EPQ) model with rework and multiple deliveries. Conventional methods for solving production lot size are by using diff erential calculus on the longrun average production-inventory-delivery cost function with the need to prove optimality first. This paper shows that optimal lot size and its related costs for the aforementioned EPQ model can be derived without derivatives. As a result, it enables students and/or practitioners who with little knowledge of calculus to understand and handle with ease the realistic EPQ systems