Browsing by Author "Tsai, SH"

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A (204,188) Reed-Solomon decoder using decomposed Euclidean algorithm
(2000)
Chang, HC
;
Cheng, CY
;
Tsai, SH
;
Lee, CY
;
電子工程學系及電子研究所
A (204, 188) Reed-Solomon decoder for DVB application is presented. The RS decoder features an area-efficient Key Equation Solver using a novel decomposed Euclidean algorithm. We implement the RS decoder using 0.35 mum CMOS 1P4M standard cells, where the total gate count is about 16K similar to 17K. Test results show that the RS decoder chip can run up to 87MHz.
A novel iodine-induced sequential cyclization reaction of norbornene derivatives leading to the formation of novel iodo-cage compounds
(1996-02-07)
Wu, HJ
;
Tsai, SH
;
Chung, WS
;
交大名義發表
;
應用化學系
Treatment of the bis-endo-thioester and acyl group substituted norbornenes 1a-d and 9a-c with iodine in aqueous tetrahydrofuran at 25 degrees C gave the novel iodo-cage compounds 2a-d and 10a-c in 80-90% yields respectively, the first example of sequential cyclization of norbornene derivatives induced by an iodine electrophile.
An approximately MAI-free multiaccess OFDM system in carrier frequency offset environment
(2005-11-01)
Tsai, SH
;
Lin, YP
;
Kuo, CCJ
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電控工程研究所
;
Institute of Electrical and Control Engineering
The carrier frequency offset (CFO) effect of a new multiaccess orthogonal frequency division multiplexing (OFDM) transceiver is analyzed. We show that multiaccess interference (MAI) due to CFO can be mitigated by choosing a proper set of orthogonal codes. That is, if we use M/2 symmetric or antisymmetric codewords of the M Hadamard-Walsh codewords, MAI can be greatly reduced to a negligible amount. The new OFDM system has been shown to be approximately MAI-free when there is no CFO. The new result developed here shows that the system continues to be approximately MAI-free even in the presence of CFO. Furthermore, we derive a close form for the reduced MAI, which reveals an interesting property of the system. That is, when the number of users increases, the reduced MAI and the inter carrier interference (ICI) due to self-CFO will decrease. Finally, it is demonstrated by simulation that the proposed OFDM scheme with proper code selection outperforms the OFDMA and the multicarrier code division multiplexing access (MC-CDMA) systems in a CFO environment.
Field-emission properties of aligned carbon nanotubes
(2000-09-15)
Hong, WK
;
Shih, HC
;
Tsai, SH
;
Shu, CT
;
Tarntair, FG
Dense, well-separated, and aligned carbon nanotubes have been prepared via bias-enhanced microwave plasma chemical vapor deposition. The turn-on fields defined at the emission current density of 10 mu A/cm(2) are about 3.35 V/mu m, 2.54 V/mu m, and 3.54V/mu m, for the immersion times in PdCl2 of 1 min, 20 min, and 40 min,respectively. The corresponding emission current densities are about 0.97 mA/cm(2), 4.5 mA/cm(2), and 0.44 mA/cm(2) at the electric field of 5 V/mu m. The higher emission current obtained from the aligned carbon nanotubes for the immersion time of 20 min is ascribed to the denser and sharper nanotubes formed in this condition.
Iodine-induced cyclization reaction of endo-thioester substituted norbornenes followed by methylthio group rearrangement
(1996-11-04)
Wu, HJ
;
Tsai, SH
;
Chung, WS
;
應用化學系
;
Department of Applied Chemistry
Treatment of the endo-thioester group substituted norbornenes 3a-3d with iodine in aqueous tetrahydrofuran at 25 degrees C gave the novel methylthio group rearranged lactonization products 4a-4d in 80% yields; iodolactonization reaction of 9 was applied to the synthesis of novel diacetal trioxa-cage compound 13. Copyright (C) 1996 Elsevier Science Ltd
Performance evaluation of optimal DMT transceivers for ADSL application
(2003)
Tsai, SH
;
Lin, YP
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Optimal transceivers that minimize the transmission power for a given probability of error and transmission bit rate will be evaluated for ADSL applications. We will compare the performance of the optimal DMT systems to that of DFT based DMT systems. The experiments show that the optimal DMT system usually has a gain of 3 dB or more over that of DFT based system. For comparable performances, the optimal DMT requires a-smaller number of subchannels and hence has a smaller system delay.
Stereoselectivity of the Diels-Alder reaction of (E)gamma-Oxo-alpha,beta-unsaturated thioesters with cyclopentadiene
(1996-06-01)
Tsai, SH
;
Chung, WS
;
Wu, HJ
;
應用化學系
;
Department of Applied Chemistry
The stereoselectivity of the Diels-Alder reaction of (E)-gamma-oxo-alpha,beta-unsaturated thioesters 3a-3d with cyclopentadiene is greatly enhanced in the presence of Lewis acids favoring the endo acyl isomers 4a-4d. In the absence of Lewis acid, Diels-Alder reaction of 3a-3d with cyclopentadiene at 25 degrees C gave two adducts 4a-4d and 5a-5d in a ratio of 1:1 respectively. In the presence of Lewis acids, Diels-Alder reaction of 3a-3d with cyclopentadiene gave 4a-4d and 5a-5d in ratios of 75 similar to 94:25 similar to 6 respectively. The stereoelectivity was enhanced to ratios of 95 similar to 98:5 similar to 2 with lowering the reaction temperature. The stereochemistry of the cycloadducts 4 and 5 was confirmed by iodocyclization. Reaction of the endo-thioester 5c with I-2 in aqueous THF at 0 degrees C gave the novel methylthio group rearranged product 6c in 80% yield, the first example of iodolactonization of endo-thioesters. Reaction of the endo-acyl isomer 4b with I-2 under the same reaction conditions gave an isomeric mixture of 7b and 8b in 1:2 ratio. The stereochemistry of the thioester group in 8b was proved by X-ray single-crystal analysis. The solvent effect on the endo selectivity of (Z)-gamma-oxo-alpha,beta-unsaturated thioester 2b was also examined.
Stereoselectivity of the Diels-Alder reaction of (E)gamma-Oxo-alpha,beta-unsaturated thioesters with cyclopentadiene
(1996-06-01)
Tsai, SH
;
Chung, WS
;
Wu, HJ
;
應用化學系
;
Department of Applied Chemistry
The stereoselectivity of the Diels-Alder reaction of (E)-gamma-oxo-alpha,beta-unsaturated thioesters 3a-3d with cyclopentadiene is greatly enhanced in the presence of Lewis acids favoring the endo acyl isomers 4a-4d. In the absence of Lewis acid, Diels-Alder reaction of 3a-3d with cyclopentadiene at 25 degrees C gave two adducts 4a-4d and 5a-5d in a ratio of 1:1 respectively. In the presence of Lewis acids, Diels-Alder reaction of 3a-3d with cyclopentadiene gave 4a-4d and 5a-5d in ratios of 75 similar to 94:25 similar to 6 respectively. The stereoelectivity was enhanced to ratios of 95 similar to 98:5 similar to 2 with lowering the reaction temperature. The stereochemistry of the cycloadducts 4 and 5 was confirmed by iodocyclization. Reaction of the endo-thioester 5c with I-2 in aqueous THF at 0 degrees C gave the novel methylthio group rearranged product 6c in 80% yield, the first example of iodolactonization of endo-thioesters. Reaction of the endo-acyl isomer 4b with I-2 under the same reaction conditions gave an isomeric mixture of 7b and 8b in 1:2 ratio. The stereochemistry of the thioester group in 8b was proved by X-ray single-crystal analysis. The solvent effect on the endo selectivity of (Z)-gamma-oxo-alpha,beta-unsaturated thioester 2b was also examined.
Synthesis of 3,5,7-trioxapentacyclo[7.2.1.0(2,8).0(4,11).0(6,10)]dodecane. A novel diacetal trioxa-cage
(1996-10-01)
Tsai, SH
;
Wu, HJ
;
Chung, WS
;
交大名義發表
;
應用化學系
3,5,7-Trioxapentacyclo[7.2.1.0(2,8).0(4,11).0(6,10)] dodecane, the parent compound of novel diacetal trioxa-cages, was synthesized from maleic anhydride cyclopentadiene adduct 1 by a four-step sequence. Attempts for the synthesis of monoaza dioxa-cage 12 failed. Ozonolysis of compound 9 in CH2Cl2-EtOH (1:1) at -78 degrees C followed by reduction with Me(2)S gave 13 in 65% yield.
Synthesis of diacetal trioxa-cage compounds via a sequential cyclization reaction of norbornene derivatives induced by electrophiles
(1997-09-05)
Wu, HJ
;
Tsai, SH
;
Chern, JH
;
Lin, HC
;
應用化學系
The synthesis of diacetal trioxa-cage compounds via a sequential cyclization reaction of norbornene derivatives induced by electrophiles in a short sequence is reported. Treatment of the norbornene derivatives 2a-d and 10b with I-2 in aqueous THF in the presence of KI at 25 degrees C regioselectively gave the iodo-cage compounds 3a-d and 11 in 80-90% yields, respectively, via a iodine-induced sequential cyclization reaction. No detectable amount of other regioisomers or monocyclization products was obtained. The synthesis of triora-cages 14a-e was accomplished from 3a-d and 11 in a two-step sequence. Treatment of diacylnorbornenes 15a-f with I-2 in aqueous THF at 25 degrees C regioselectively and stereoselectively gave the sequential cyclization products 16a-f, respectively, which were converted in one step to the diacetal trioxa-cages 24a-f in high yields. The structure of these trioxa-cages was proven by X-ray analysis of the crystalline compound 14e. Other electrophiles, such as bromine, m-CPBA, and Hg(OAc)(2), were also found to be effective for the sequential cyclization reaction. Oxymercuration of 15a-f and 2a-c with Hg(OAc)(2) in aqueous THF followed by reduction with NaBH4 at 25 degrees C gave compounds 28a-f and 30b,d,c in high yields, respectively.
Synthesis of diacetal trioxa-cage compounds via a sequential cyclization reaction of norbornene derivatives induced by electrophiles
(1997-09-05)
Wu, HJ
;
Tsai, SH
;
Chern, JH
;
Lin, HC
;
交大名義發表
The synthesis of diacetal trioxa-cage compounds via a sequential cyclization reaction of norbornene derivatives induced by electrophiles in a short sequence is reported. Treatment of the norbornene derivatives 2a-d and 10b with I-2 in aqueous THF in the presence of KI at 25 degrees C regioselectively gave the iodo-cage compounds 3a-d and 11 in 80-90% yields, respectively, via a iodine-induced sequential cyclization reaction. No detectable amount of other regioisomers or monocyclization products was obtained. The synthesis of triora-cages 14a-e was accomplished from 3a-d and 11 in a two-step sequence. Treatment of diacylnorbornenes 15a-f with I-2 in aqueous THF at 25 degrees C regioselectively and stereoselectively gave the sequential cyclization products 16a-f, respectively, which were converted in one step to the diacetal trioxa-cages 24a-f in high yields. The structure of these trioxa-cages was proven by X-ray analysis of the crystalline compound 14e. Other electrophiles, such as bromine, m-CPBA, and Hg(OAc)(2), were also found to be effective for the sequential cyclization reaction. Oxymercuration of 15a-f and 2a-c with Hg(OAc)(2) in aqueous THF followed by reduction with NaBH4 at 25 degrees C gave compounds 28a-f and 30b,d,c in high yields, respectively.
Synthesis of dioxa-cages as a new probe for the stereochemistry of the bisadducts of p-quinone with cyclopentadiene and cyclohexadiene
(1998-12-01)
Yen, CH
;
Tsai, SH
;
Wu, HJ
;
應用化學系
;
Department of Applied Chemistry
The synthesis of dioxa-cages via iodine-induced cyclization reaction can be used as a new method for the determination of the stereochemistry of the bisadducts of p-quinone with cyclopentadiene and cyclohexadiene. The bisadducts 2 and 8 were converted into the dioxa-cages 13a and 13b via a three-step sequence, respectively. The stereochemistry of 13a and 13b was determined on the basis of NOE experiments.
Tunable semiconductor laser with liquid crystal pixel mirror in grating-loaded external cavity
(1999-08-19)
Pan, CL
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Tsai, SH
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Pan, RP
;
Sheu, CR
;
Wang, SC
The wavelength of a commercial red pointer laser diode has been tuned over 4nm digitally in 0.2nm steps with a folded telescopic gating loaded external cavity incorporating a liquid crystal pixel mirror. The sidemode-suppression ratio of the laser was better than 20dB throughout this range.