Browsing by Author "Ke, WT"

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Job order releasing and throughput planning for multi-priority orders in wafer fabs
(2003-01-01)
Chung, SH
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Pearn, WL
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Lee, AHI
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Ke, WT
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工業工程與管理學系
To meet the production target of multi-level (multiple priority rank) orders in wafer fabs, this paper uses a hierarchical framework based on a mathematical model, and without the assistance of any simulation tool, to build a production scheduling system to plan wafer lot releasing sequence and time. This system first applies capacity loading analysis to set up the batch policy for each level (rank) of orders. Next, the production cycle time of each product level is estimated with considerations of batching and loading factor. The cycle time is then used to derive system control parameters such as the most appropriate level of work in process (WIP) and the number of daily operations on the bottleneck workstation. Lastly, a Constant WIP mechanism is applied to establish a wafer release sequence table and a throughput timetable. The due date designation for each specific order can hence be confirmed. With the comparison with the result of simulation, it shows that under the designed system the performance and planning measures in the master production schedule can be drawn up quickly and accurately, and the system throughput target and due date satisfaction can be achieved. Overall, the proposed production scheduling system is both effective and practicable, and the planning results are supportive for good target planning and production activity control.
On L(d, 1)-labelings of graphs
(2000-06-06)
Chang, GJ
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Ke, WT
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Kuo, D
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Liu, DDF
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Yeh, RK
Given a graph G and a positive integer d, an L(d, 1)-labeling of G is a function f that assigns to each vertex of G a non-negative integer such that if two vertices u and u are adjacent, then f(u) - f(v) greater than or equal to d; if u and v are not adjacent but there is a two-edge path between them, then f(u)- f(v) greater than or equal to 1. The L(d, 1)-number of G, lambda(d)(G), is defined as the minimum m such that there is an L(d, 1)-labeling f of G with f(V) subset of or equal to {0, 1, 2,,.., m}. Motivated by the channel assignment problem introduced by Hale (Proc, IEEE 68 (1980) 1497-1514), the L(2, 1)-labeling and the L(1, 1)-labeling (as d = 2 and 1, respectively) have been studied extensively in the past decade. This article extends the study to all positive integers d. We prove that lambda(d)(G) less than or equal to Delta(2) + (d - 1)Delta for any graph G with maximum degree d. Different lower and upper bounds of lambda(d)(G) for some families of graphs including trees and chordal graphs are presented. In particular, we show that the lower and the upper bounds for trees are both attainable, and the upper bound for chordal graphs can be improved for several subclasses of chordal graphs. (C) 2000 Elsevier Science B,V. All rights reserved.