Browsing by Author "Chang, WC"

Now showing 1 - 8 of 8

A 528MS/s frequency synchronizer for OFDM-based UWB system
(2005)
Chen, LH
;
Chang, WC
;
Liu, HY
;
Lee, CY
;
電子工程學系及電子研究所
A novel frequency synchronizer is proposed for 528MHz OFDM-based UWB system. It can reduce 75% memory and 59% power consumption through a low-power scheme based on data. partition. Measured result shows the proposed design can achieve 528MSamples/s throughput in 0.18 mu m CMOS process.
An area and power efficient frame synchronizer for 480Mb/s OFDM-based UWB system
(2005)
Chang, WC
;
Chen, LH
;
Liao, WC
;
Liu, HY
;
Lee, CY
A novel frame synchronizer is proposed for OFDM-based UWB system. Integrating the improved matched filters and dynamic threshold design, the proposed design can reduce 65% area and 58% power with an acceptable performance loss. It can achieve 528MS/s throughput for 480Mb/s UWB system in 0.18 mu m CMOS process.
Plausible origin of electromigration lifetime extrapolation difference between wafer level isothermal test and package level constant current test
(2004)
Wang, CS
;
Chen, MJ
;
Chang, WC
;
Ke, WS
;
Lee, CF
Electromigration lifetime extrapolated from the wafer level isothermal test on a metal line does not coincide with that from the package level constant current test. The discontinuity of mass flux density in wafer level isothermal test as origin of such difference is identified based on a temperature profile along the metal line. Once this issue is clarified in advance, improved correlation between both tests can be achieved and as a result, wafer level isothermal test is expected to replace the conventional time-consuming package level constant current test.
Rate-distortion optimized video streaming with smooth quality constraint
(2005)
Ho, CP
;
Chang, WC
;
Lee, KC
;
Tsai, CJ
;
資訊工程學系
In this paper, we propose an approach to integrate smooth quality constraint into a rate-distortion optimized scalable video streaming system over variable bandwidth networks. The constraint is based on the analysis of video content complexity. In order to preserve smooth video quality when the network bandwidth and video data rate vary, the scheme take into account degree of motion in each frame in an R-D optimized framework to determine the packet scheduling policy. An implementation based on MPEG-4 FGS codec is presented in this paper. Initial experiments show that the proposed approach can outperform the traditional scalable streaming systems under harsh network conditions.
The effect of grain boundary impedance on the power loss of Mn-Zn ferrites over 1 MHz
(1997-03-01)
Tung, MJ
;
Tseng, TY
;
Tsay, MJ
;
Chang, WC
;
電子工程學系及電子研究所
Recently, the operating frequency of switching mode power supplies has been increased from 25 kHz to several MHz to enhance their efficiency in a smaller size. Although, it was reported that Mn-Zn ferrites can also be used at 1 MHz, only few papers have discussed the possibility of using Mn-Zn ferrites at the frequency higher than 1 MHz. Our early paper reported that the core loss of low loss grade Mn-Zn ferrites is strongly dependent upon the capacitance of grain boundaries of sintered cores. In frequency region between 1 MHz to 3 MHz, the dielectric loss dominates the core loss, while eddy current loss is the major factor of the core loss in 3 MHz to 10 MHz. It is suggested that decreasing the grain boundary capacitance at middle high frequency or increasing the grain resistivity at high frequency region are the appropriate ways for Mn-Zn ferrites to be used at the frequency between 1 MHz and 10 MHz. This paper investigated the core loss of Mn-Zn ferrites in the frequency range between 1 MHz and 10 MHz in order to improve the properties of the Mn-Zn ferrite cores for their potential applications in this frequency region. The powders containing Fe2O3, MnO and ZnO ina molar ratio of 54.2:7.3:8.5 with the addition of CaO and SiO2 from 150 ppm to 450 ppm were prepared by a conventional ceramic process. Samples were sintered at 1150 degrees C to 1250 degrees C for 2 hrs then annealed at various condition. The results show that the sintering temperature and annealing condition altered the grain boundary impedance. For example, the grain boundary capacitance changes from 13 pF to 7 pF, meanwhile, the dielectric loss factor is lowered from 0.28 x 10(-9) to 0.17 x 10(-9), and consequently the power loss decreases from 253 KW/m(3) to 145 KW/m(3) at 2.5 MHz.
The molecular mechanism of actinomycin D in preventing neointimal formation in rat carotid arteries after balloon injury
(2005-05-01)
Wu, CH
;
Pan, JS
;
Chang, WC
;
Hung, JS
;
Mao, SJT
The pathological mechanism of restenosis is primarily attributed to excessive proliferation of vascular smooth muscle cells (SMC). Actinomycin D has been regarded as a potential candidate to prevent balloon injury-induced neointimal formation. To explore its molecular mechanism in regulating cell proliferation, we first showed that actinomycin D markedly reduced the SMC proliferation via the inhibition of BrdU incorporation at 80 nM. This was further supported by the G1-phase arrest using a flowcytometric analysis. Actinomycin D was extremely potent with an inhibitory concentration IC50 at 0.4 nM, whereas the lethal dose LD50 was at 260 mu M. In an in vivo study, the pluronic gel containing 80 nM and 80 lMactinomycin D was applied topically to surround the rat carotid adventitia; the thickness of neointima was substantially reduced (45 and 55%, respectively). The protein expression levels of proliferating cell nuclear antigen ( PCNA), focal adhesion kinase (FAK), and Raf were all suppressed by actinomycin D. Extracellular signal-regulated kinases (Erk) involved in cell-cycle arrest were found to increase by actinomycin D. These observations provide a detailed mechanism of actinomycin D in preventing cell proliferation thus as a potential intervention for restenosis.
The preventive effects of G115 on balloon injury-induced neointima formation in rats
(2001-12-28)
Wu, CH
;
Tsai, BR
;
Hsieh, WT
;
Chang, GY
;
Mao, SJT
After percutaneous transluminal coronary angioplasty (PTCA), 30-50% of the patients may present with restenosis within 6 months. The aim of this study was to search for a preventive remedy against the balloon injury-induced neointima formation. Ginseng, with its wide indications on immune and cardiovascular functions, has prompted us to explore its role in neointima formation. In the present study, we aimed to explore if a standardized Panax Ginseng extract G115 was able to inhibit neointimal formation. With BrdU luminencence assay, maximal proliferation of rat smooth muscle cells was reduced to 24% of control values by G115. Norepinephrine-induced vasocontraction was antagonized in 21% and 44% by 1.44mg/ml and 2.88mg/ml of G115, respectively. Neointima-to-lumen area ratio of balloon-injured rat carotid arteries was reduced 77.3% by G115 as compared to the sham control. These results demonstrate the preventive effects of ginsenosides on angioplasty-mediated neointima formation. (C) 2001 Elsevier Science Inc. All rights reserved.
Zinc ion acts as a cofactor for serine/threonine kinase MST3 and has a distinct role in autophosphorylation of MST3
(2005-06-01)
Lu, TJ
;
Huang, CYF
;
Yuan, CJ
;
Lee, YC
;
Leu, TH
We examined the metal ion cofactor preference for MST3 (mammalian Ste20-like kinase 3) of the Ste20 serine/threonine kinase family. Four metal ions (Mg+2, Mn+2, Zn2+, and Co2+) activate endogenous, exogenous, and baculovirus-expressed recombinant MST3 within the physiological concentration range. In contrast, Fe+2 and Ca+2 do not function as MST3 cofactors. Mn2+, Co2+, and Mg2+-dependent autophosphorylation of MST3 is mainly on threonine residue while Zn2+-stimulated MST3 autophosphorylation is on both serine and threonine residues. The distinct autophosphorylation pattern on MST3 suggests that MST3 may exert various types of kinase reactions depending on the type of metal ion cofactor used. To our knowledge, this is the first report showing Zn2+ as the metal ion cofactor of a recombinant serine/threonine kinase. (C) 2005 Elsevier Inc. All rights reserved.