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- Hark-Chin Hwang, Soo Y. Chang, Kangbok Lee
- Computers & OR
- 2004

We consider the problem of scheduling parallel machines that process service requests from various customers who are entitled to many di1erent grade of service (GoS) levels. We propose and analyze one simple way to ensure such di1erentiated service. In particular, we investigate how the longest processing time 5rst algorithm (LPT) would perform in the worst… (More)

- Soo Y. Chang, Hark-Chin Hwang, Sanghyuck Park
- Computers & OR
- 2005

We consider the problem of e&ciently packing steel products, known as coils, into special containers, called cassettes for shipping. The objective is to minimize the number of cassettes used for packing all the given coils where each cassette has capacity limits on both total payload weight and size. We model this problem as a two-dimensional vector packing… (More)

- Soo Y. Chang, Hark-Chin Hwang
- Discrete Applied Mathematics
- 1999

In this paper we consider the nonsimultaneous multiprocessor scheduling problem, or NMSP for short. The NMSP is a makespan minimization scheduling problem which involves the nonpreemptive assignment of independent jobs on m parallel machines with di erent starting times. It is well known that the longest processing time (LPT) algorithm and the modi ed… (More)

- Hark-Chin Hwang
- Operations Research
- 2010

- Hark-Chin Hwang, Kangbok Lee, Soo Y. Chang
- Discrete Applied Mathematics
- 2005

We consider the makespan minimization parallel machine scheduling problemwhere each machine may be unavailable for a known time interval. For this problem, we investigate how the worst-case behavior of the longest processing timefirst algorithm (LPT) is affected by the availability ofmachines. In particular, for givenmmachines, we analyze the cases where… (More)

- Hark-Chin Hwang
- Transportation Science
- 2009

- Hark-Chin Hwang, Hyun-Soo Ahn, Philip Kaminsky
- Operations Research
- 2013

We consider the multilevel lot-sizing problem with production capacities (MLSP-PC), in which production and transportation decisions are made for a serial supply chain with capacitated production and concave cost functions. Existing approaches to the multistage version of this problem are limited to nonspeculative cost functions—up to now, no algorithm for… (More)

- Hark-Chin Hwang, Kyungkuk Lim
- Discrete Applied Mathematics
- 2014

- Wilco van den Heuvel, José Miguel Gutiérrez, Hark-Chin Hwang
- European Journal of Operational Research
- 2008

In a recent paper Gutiérrez et al. (2008) show that the lot-sizing problem with inventory bounds can be solved in O(T log T ) time. In this note we show that their algorithm does not lead to an optimal solution in general. ∗Corresponding author. Tel.: +31 10 4081307; fax: +31 10 4089162

- Hark-Chin Hwang, Wikrom Jaruphongsa
- European Journal of Operational Research
- 2008

This paper deals with a lot-sizing model for major and minor demands in which major demands are specified by time windows while minor demands are given by periods. For major demands, the agreeable time window structure is assumed where each time window is not strictly nested in any other time windows. To incorporate the economy of scale of large production… (More)