Browsing by Author "Chao, CC"

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Complementary sets and Reed-Muller codes for peak-to-average power ratio reduction in OFDM
(2006)
Chen, CY
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Wang, CH
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Chao, CC
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電信工程研究所
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Institute of Communications Engineering
One of the disadvantages of orthogonal frequency division multiplexing (OFDM) systems is the high peak-to-average power ratio (PAPR) of OFDM signals. Colay complementary sets have been proposed to tackle this problem. In this paper, we develop several theorems which can be used to construct Golay complementary sets and multipleshift complementary sets from Reed-Muller codes. We show that the result of Davis and Jedwab on Golay complementary sequences and those of Paterson and Schmidt on Colay complementary sets can be considered as special cases of our results.
Space allocation for commercial activities at international passenger terminals
(2005-01-01)
Hsu, CI
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Chao, CC
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運輸與物流管理系註：原交通所+運管所
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Department of Transportation and Logistics Management
This study examines the relationships among commercial revenue, passenger service level and space allocation in international passenger terminals. Using mathematical programming, this study constructs a model for maximizing concession revenues while maintaining service level, to optimize the space allocation for various types of stores. This study then uses CKS International Airport as an example to demonstrate the applicability of the models. The results show that total commercial revenues can be maximized by locating the stores with more concession revenue in the more accessible positions. Moreover, the optimal space allocation for commercial activities and public facilities changes with passenger volumes and/or service levels. (C) 2004 Elsevier Ltd. All rights reserved.
The enhanced soft handoff algorithm for multirate DS-CDMA cellular systems
(2003)
Chao, CC
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Ching, YL
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Chung, JC
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電信工程研究所
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Institute of Communications Engineering
In this paper, an enhanced soft handoff algorithm is proposed to improve system capacity for multi-rate DS-CDMA cellular systems. In the algorithm, we first propose a load-based power allocation scheme for serving soft handoff users in the forward link; we next develop two kinds of active set determination mechanism: a quality-based active set control (QBASC) scheme and fuzzy active set control (FASC) scheme, to re-select active set members so as to not only save system resource but also maintain required signal quality. Simulation results show that the proposed enhanced soft handoff algorithms can successfully achieve load balancing between cells. Compared to the conventional soft handoff algorithm, QBASC and FASC schemes can enhance 71.43% and 85.71% system capacity in the multirate DS-CDMA cellular system with hot-spot, respectively.
The influence of Mg on creep properties and fracture behaviors of Mar-M247 superalloy under 1255 K/200 MPa
(2000-05-01)
Bor, HY
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Chao, CC
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Ma, CY
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材料科學與工程學系
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Department of Materials Science and Engineering
The effects of Mg microadditions on the high-temperature/low stress (1255 K/200 MPa) creep properties and fracture behavior of a Mar-M247 superalloy were investigated in this study. The results of quantitative statistical analyses showed that when Mg microadditions up to 50 ppm were made, the MC carbides located at grain boundaries (designated GB MC) were significantly refined and spheroidized and the number of MC carbides decreased. In addition, the M23C6 carbides present on GBs dramatically increased with increasing Mg contents up to 50 ppm, and the creep resistance was enhanced under the test condition of 1255 K/200 MPa. However, the creep performance of a Mar-M247 superalloy containing 80 ppm Mg deteriorated due to the formation of an extremely large amount of MC carbide and a decrease in the number of M23C6 carbides at GBs. The cracks mainly initiated and propagated along GBs in both the Mg-free and Mg-containing Mar-M247 superalloys under 1255 K/200 MPa, and the finial rupture was caused by intergranular fracture. Under the present creep condition, the optimal Mg microaddition to a Mar-M247 superalloy should be 30 to 50 ppm.