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LPT Scheduling for Multipurpose Machines
황학진,Hwang, Hark-Chin 대한산업공학회 2003 산업공학 Vol.16 No.S
We consider scheduling jobs on multipurpose machines where jobs can be processed by a subset of the machines operated in parallel with the objective of minimizing makespan. We apply LPT(Longest Processing Time first) algorithm and prove that its posterior worst-case performance ratio is at most $log_24m/(1+{\lambda})$, where \lambda is the number of machines eligible for processing the job with the latest completion time. In general, LPT is shown to always find a schedule with makespan at most $log_24m/3$ times optimum.
Hark-Chin Hwang(황학진) 한국경영과학회 2007 한국경영과학회 학술대회논문집 Vol.2007 No.11
This paper considers a shipment planning of products from manufacturers to a third-party warehouse for demands with production time windows where a demand must be replenished in its time window. The underling lot-sizing model also assumes cargo delivery cost in each inbound replenishment to the warehouse. For this mode I, an optimal O(nT⁴) is presented where n is the number of demands and T is the length of the planning horizon.
On the effect of demand randomness on inventories and costs under competition
Hark-Chin Hwang(황학진) 한국경영과학회 2009 한국경영과학회 학술대회논문집 Vol.2009 No.10
We consider the effect of demand randomness on the inventory level and cost of inventory systems under competition. The demand randomness is given by a mean preserving transformation of an industry demand. Two firms or divisions in a company are initially allocated a deterministic portion of the demand and then competes with inventory level. For the single-period competitive news vendor model, we observe how the inventory level and cost of each firm changes as the variance of demand increases (decreases).
황학진(Hark-Chin Hwang) 한국경영과학회 2007 經營 科學 Vol.24 No.2
In this paper we consider an alternate m machine scheduling problem in which each job having at most two eligible machines should be assigned with the objective of makespan minimization. For this problem, we propose a O(m2<SUP>m</SUP>) time rounding algorithm with performance ratio at most 1.5. For a little general problem where each job can be processed in at most three machines, we prove that a polynomial time algorithm does not exist with performance ratio less than 1.5.