Browsing by Author "Chen, Chun-Hao"

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A distributed server architecture supporting dynamic resource provisioning for BPM-oriented workflow management systems
(2010-08-01)
Tsai, Ching-Hong
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Huang, Kuo-Chan
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Wang, Feng-Jian
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Chen, Chun-Hao
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資訊工程學系
Workflow management systems have been widely used in many business process management (BPM) applications. There are also a lot of companies offering commercial software solutions for BPM. However, most of them adopt a simple client/server architecture with one single centralized workflow-management server only. As the number of incoming workflow requests increases, the single workflow-management server might become the performance bottleneck, leading to unacceptable response time. Development of parallel servers might be a possible solution. However, a parallel server architecture with a fixed-number of servers cannot efficiently utilize computing resources under time-varying system workloads. This paper presents a distributed workflow-management server architecture which adopts dynamic resource provisioning mechanisms to deal with the probable performance bottleneck. We implemented a prototype system of the proposed architecture based on a commercial workflow management system, Agentflow. A series of experiments were conducted on the prototype system for performance evaluation. The experimental results indicate that the proposed architecture can deliver scalable performance and effectively maintain stable request response time under a wide range of incoming workflow request workloads. (C) 2010 Elsevier Inc. All rights reserved.
A GA-based approach for finding appropriate granularity levels of patterns from time series
(2016)
Chen, Chun-Hao
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Tseng, Vincent S.
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Yu, Hsieh-Hui
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Hong, Tzung-Pei
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Yen, Neil Y.
In our previous approach, we proposed an algorithm for finding segments and patterns simultaneously from a given time series. In that approach, because patterns were derived through clustering techniques, the number of clusters was hard to be setting. In other words, the granularity of derived patterns was not taken into consideration. Hence, an approach for deriving appropriate granularity levels of patterns is proposed in this paper. The cut points of a time series are first encoded into a chromosome. Each two adjacent cut points represents a segment. The segments in a chromosome are then divided into groups using the cluster affinity search technique with a similarity matrix and an affinity threshold. With the affinity threshold, patterns with the desired granularity level can be derived. Experiments on a real dataset are also conducted to demonstrate the effectiveness of the proposed approach.
Performance Improvement in RF LDMOS Transistors Using Wider Drain Contact
(2013-09-01)
Chen, Kun-Ming
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Chen, Bo-Yuan
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Chiu, Chia-Sung
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Huang, Guo-Wei
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Chen, Chun-Hao
In this letter, we proposed a new layout structure for RF laterally diffused metal-oxide-semiconductor (LDMOS) transistors. In a multifinger layout, the drain contact region was designed to be wider than the channel region. The wider drain increases the equivalent drift region width to reduce the drift resistance and suppress the quasi-saturation effect. We found that the wide-drain multifinger LDMOS devices have lower on-resistance, higher cutoff frequency, higher maximum oscillation frequency, and better power performances than the standard multifinger ones.