Browsing by Issue Date, starting with "2002-07-15"

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Intrachain carrier transport in conjugated polymer with structural and chemical defects
(2002-07-15)
Chen, YS
;
Meng, HF
;
物理研究所
;
Institute of Physics
By calculating the phase shifts of the wave functions for the extended scattering states within tight-binding model for a poly (p-phenylene vinylene) chain with one conjugation defect, we obtain the exact transmission probability through the defect as a function of the carrier incident energy for the entire eight pi bands. Cis-defect, sp(3) saturation, and oxidation are considered. The transmission increases rapidly from zero with the carrier kinetic energy, implying the conjugation breaks do not severely limit the intrachain charge transport under high electric field. Assuming an average conjugation length of 100 Angstrom separated by cis-defects, the drift velocity is predicted to be as high as 10(3) m/s for field at 10(7) V/m, and over 10(5) m/s at 10(8) V/m.
Induction of cyclooxygenase-2 by staurosporine through the activation of nuclear factor for IL-6 (NF-IL6) and activator protein 2 (AP2) in an osteoblast-like cell line
(2002-07-15)
Wang, CY
;
Lei, HJ
;
Huang, CYF
;
Zhang, ZJ
;
Mukherjee, AB
The induction of cyclooxygenase-2 (COX-2) plays a crucial role in many physiological and pathological processes. The expression of the COX-2 gene is regulated by many extracellular stimuli, including growth factors, cytokines, and tumor promoters. Staurosporine, a potential anti-tumor drug, was found recently to up-regulate the expression of the COX-2 gene in the mouse osteoblast-like cell line MC3T3-E1. The ability of staurosporine to induce the expression of the COX-2 gene was investigated using luciferase reporters controlled by various COX-2 core promoter regions. Two cis-acting sites for activator protein 2 (AP2) and nuclear factor for IL-6 (NF-IL6), respectively, were identified as responsible for the staurosporine-mediated COX-2 up-regulation. Mutational analysis further verified that both NF-IL6 and AP2 are involved in this process. Further studies showed the stimulatory effect of staurosporine on luciferase activity to be both time- and concentration-dependent. Luciferase activity could be induced at as low as 5 nM staurosporine and reached a maximum at around 20 nM. At 50 nM, the stimulatory effect of staurosporine on luciferase activity reached a maximum at about 8 hr and fell rapidly following 10 hr of incubation. Interestingly, a selective protein kinase C inhibitor, 2-[1-(3-dimethylaminopropyl)indol-3-yl]-3-(indol-3-yl) maleimide (GF109203X), failed to stimulate luciferase activity under the same conditions. This finding implies that staurosporine-mediated COX-2 gene expression is specific and independent of protein kinase C activity. (C) 2002 Elsevier Science Inc. All rights reserved.
The numerical range of a nonnegative matrix
(2002-07-15)
Li, CW
;
Tam, BS
;
Wu, PY
;
應用數學系
;
Department of Applied Mathematics
We offers an almost self-contained development of Perron-Frobenius type results for the numerical range of an (irreducible) nonnegative matrix, rederiving and completing the previous work of Issos, Nylen and Tam, and Tam. and Yang on this topic. We solve the open problem of characterizing nonnegative matrices whose numerical ranges are re gular convex polygons with center at the origin. Some related results are obtained and some open problems are also posed. (C) 2002 Elsevier Science Inc. All rights reserved.
Using buried capacitor in LTCC-MLC balun
(2002-07-18)
Tang, CW
;
Chang, CY
;
電信工程研究所
;
Institute of Communications Engineering
A novel chip-type ceramic balun designed in the 2.4 GHz ISM band frequency is presented. A buried capacitor is included in the balun, so that the length of the coupled transmission lines can be reduced and can be designed very easily. A meander or spiral broadside coupled-line is adopted to realise the proposed LTCC multi-layer balun. The measured performances of phase and amplitude balance for this LTCC-MLC balun show a good match with computer simulation.
BIST scheme for DAC testing
(2002-07-18)
Chang, SJ
;
Lee, CL
;
Chen, JE
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A low-cost, built-in self-test (BIST) scheme for a digital-to-analogue converter (DAC) is presented. The basic idea is to convert the DAC output voltages corresponding to different input codes into different oscillation frequencies through a voltage controlled oscillator (VCO), and further transfer these frequencies to different digital codes using a counter. According to the input and output codes, performances of a DAC, such as offset error, gain error, differential nonlinearity (DNL), integral nonlinearity (INL), could be effectively detected by simply using digital circuits rather than complex analogue ones. In addition, the annoying DAC output noise could be naturally filtered out by this BIST method.
Bias effect on the growth of carbon nanotips using microwave plasma chemical vapor deposition
(2002-07-22)
Tsai, CL
;
Chen, CF
;
Wu, LK
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Carbon nanotips with a high-aspect ratio were directly grown on Pt films. Carbon nanotips grew up to 5.4 mum length and 64 nm diameter under a -120 V bias. Compared to the hollow structure of carbon nanotubes, transmission electron microscopy images indicate its solid body, which is made of graphite. Carbon nanotips possess good field emission characteristics, that is, a turn-on field of 1.5 V/mum and 761 muA/cm(2) under 2.2 V/mum. The Pt films provide a good conduction path for electron transport from the cathode to the emission site and do not act as catalysts. (C) 2002 American Institute of Physics.
A novel amplifying antenna array using patch-antenna couplers - Design and measurement
(2002-08-01)
Tsai, CH
;
Yang, YCA
;
Chung, SJ
;
Chang, K
;
電信工程研究所
This paper proposes a novel amplifying antenna array using the patch-antenna coupler formed by placing one or two open-ended microstrip lines (coupled lines) near and along the nonradiating edge(s) of a patch antenna. An X-band five-element array with broadside 25-dB Chebyshev radiation is demonstrated. When the input signal is fed to the center element, with most of the power radiating from the antenna, part of it is tapped to the coupled lines, amplified by an FET amplifier, and fed to the next antenna element. This process is repeated after all the antenna elements are fed with suitable power. The amplitude distribution of the fields radiated from the antennas is controlled by the coupling coefficient from the patch to the coupled line, which, in turn, is governed by the coupling length and gap between the patch and line. The measured return loss of the designed five-element array is -27 dB at the center frequency of 10 GHz with 2% 10-dB bandwidth. The radiation pattern possesses a transmitting gain of 15.9 dB, a half-power beamwidth of 17degrees, and a sidelobe level of -22 dB.
Analysis of petroleum distillates from fire debris using supercritical fluid extraction with a two-level orthogonal array experimental design
(2002-08-01)
Huang, CT
;
Hsieh, YZ
;
應用化學系
;
Department of Applied Chemistry
A supercritical fluid extraction (SFE) method was developed in the present study as an effective sample pretreatment technique of petroleum distillates from fire debris. Three petroleum distillates were used as target analytes, including 95 unleaded gasoline, kerosene, and premium diesel. An orthogonal array (L16) experimental design was adopted to separately evaluate primary SFE experimental factors. The SFE efficiencies of petroleum distillates at various extraction conditions were examined and the optimized SFE conditions were identified. Experimental results demonstrated that the optimized SFE method not only provided an effective extraction method for the spiked sample, but also successfully recovered residues of petroleum distillates from fire debris.
Dependence of deep level concentrations on ammonia flow rate in n-type GaN films
(2002-08-01)
Lee, L
;
Chang, FC
;
Chung, HM
;
Lee, MC
;
Chen, WH
Deep level transient spectroscoppy was used to characterize the deep levels of GaN films grown with various V/III ratios using metalorganic vapor phase epitaxy. Two prominent defects, located at E(C)-0.569 +/- 0.003 and E(C)-1.013 +/- 0.091 eV, were detected in this study. When the NH(3) flow rate was increased, we observed a slight increase in trap concentration of the E(C)-0.569 eV defect and a significant increase at E(C)-1.013 eV. Although a high V/III seems necessary for obtaining good quality GaN film, our results indicate that, if the ammonia is in excessive supply, it may generate a large number of E(C)-1.013 eV deep level defects, which deteriorate the film quality - which should be avoided with special care.
A manufacturer's optimal quantity discount strategy and return policy through game-theoretic approach
(2002-08-01)
Su, CT
;
Shi, CS
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
This study generalised the traditional quantity discount problem with return contracts, in which a manufacturer promises to refund some fraction of the retailer's wholesale price if an item is returned, as a two-stage game. In the first stage the manufacturer and retailer determine the inventory level cooperatively. In the second stage, the manufacturer bargains with the retailer for quantity discount and return schemes to maintain channel efficiency. A menu of discount-return combinations is proposed for the manufacturer to make inventory decisions. The model developed will demonstrate that the return policy can be considered as mirror images of quantity discount strategy. That is, options with more generous return privileges are coupled with higher wholesale prices, whereas the lowest wholesale price comes with very strict limits on returns and a restocking fee for any returned goods.
A fast audio bit allocation technique based on a linear R-D model
(2002-08-01)
Lee, CY
;
Fang, YC
;
Chuang, HC
;
Wang, CN
;
Chiang, T
The MPEG-1 Layer III audio coding is most widespread digital audio format on the Internet. Its encoder is more complicated than the other layers., in the MPEG-I audio specification, where the bit allocation constitutes significant part of the total computational load. This paper describes a fast bit allocation technique using a novel linear model to compute the bitrate and the global gain of the inner loop (rate control loop) for the classic MP3 bit allocation problem. Estimated quantization noise is approximated with a binomial expansion for the adjustment of the scalefactors. This procedure reduces the outer loop iterations (distortion control loop) to one loop. Our bit allocation technique is about five times faster compared to the well-known LAME MP3 encoder. Based on the objective quality measure, total number of distorted bands, and average total noise-to-masking ratio (NMR), our experimental results show that there is significant improvement in speedup of the encoding process without noticeable audio quality degradation.
Electron energy state spin-splitting in 3D cylindrical semiconductor quantum dots
(2002-08-01)
Li, Y
;
Voskoboynikov
;
Lee, CP
;
Sze, SM
;
Tretyak, O
In this article we study the impact of the spin-orbit interaction on the electron quantum confinement for narrow gap semiconductor quantum dots. The model formulation includes: (1) the effective one-band Hamiltonian approximation; (2) the position- and energy-dependent quasi-particle effective mass approximation; (3) the finite hard wall confinement potential; and (4) the spin-dependent Ben Daniel-Duke boundary conditions. The Hartree-Fock approximation is also utilized for evaluating the characteristics of a two-electron quantum dot system. In our calculation, we describe the spin-orbit interaction which comes from both the spin-dependent boundary conditions and the Rashba term (for two-electron quantum dot system). It can significantly modify the electron energy spectrum for InAs semiconductor quantum dots built in the GaAs matrix. The energy state spin-splitting is strongly dependent on the dot size and reaches an experimentally measurable magnitude for relatively small dots. In addition, we have found the Coulomb interaction and the spin-splitting are suppressed in quantum dots with small height.
A parallelized indexing method for large-scale case-based reasoning
(2002-08-01)
Chen, WC
;
Tseng, SS
;
Chang, LP
;
Hong, TP
;
Jiang, MF
Case-based reasoning (CBR) is a problem-solving methodology commonly seen in artificial intelligence. It can correctly take advantage of the situations and methods in former cases to find out suitable solutions for new problems. CBR must accurately retrieve similar prior cases for getting a good performance. In the past, many researchers proposed useful technologies to handle this problem. However, the performance of retrieving similar cases may be greatly influenced by the number of cases. In this paper, the performance issue of large-scale CBR is discussed and a parallelized indexing architecture is then proposed for efficiently retrieving similar cases in large-scale CBR. Several algorithms for implementing the proposed architecture are also described. Some experiments are made and the results show the efficiency of the proposed method. (C) 2002 Elsevier Science Ltd. All rights reserved.
Precursor ISI-free frame synchronization for DMT VDSL system
(2002-08-01)
Lin, ST
;
Wei, CH
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A new modified maximum likelihood (ML) algorithm for frame synchronization in discrete multitone VDSL transmission system is presented. Computer simulation results are included to show its improvement in Et/N-0 of each tone in the received data. This algorithm estimates the frame boundary at the initial transition edge rather than at the middle peak of a shortened twisted-pair channel response. The timing margin degradation caused by precursor intersymbol interference (ISI) can be reduced significantly, especially at the sub-channel loaded with more bits.
Impacts of gate structure on dynamic threshold SOI nMOSFETs
(2002-08-01)
Lo, WC
;
Chang, SJ
;
Chang, CY
;
Chao, TS
;
電子工程學系及電子研究所
The effects of different substrate-contact structures (T-gate and H-gate) dynamic threshold voltage silicon-on-insulator (SOI) nMOSFETs (DTMOS) have been investigated. It is found that H-gate structure devices have higher driving current than T-gate under DTMOS-mode operation. This is because H-gate SOI devices have larger body effect factor (gamma), inducing a lager reduction of threshold voltage. Besides, it is found that drain-induced-barrier-lowering (DIBL) is dramatically reduced for both T-gate and H-gate structure devices when devices are operated under DTMOS-mode.
Investigation of superfilling and electrical characteristics in low-impurity-incorporated Cu metallization
(2002-08-01)
Shieh, JM
;
Chang, SC
;
Dai, BT
;
Feng, MS
;
材料科學與工程學系
Complete filling of 0.13-mum vias and deposition of Cu with a low resistivity of about 2.3 muOmega(.)cm were obtained using an electrolyte with 2-aminobenzothiazole (2ABT) as the filling promoter. Due to the moderate charge transfer polarization characteristic realized by the addition of 2ABT, the film resistivity and the activation energy for thermal grain growth were similar to those for electrolytes without it. After rapid thermal annealing (RTA) at 400degreesC for 30 s, the resistivity was further reduced to similar to1.9 muOmega(.)cm.
A solution model of integrating cells of PCS to switches in wireless ATM network
(2002-08-01)
Din, DR
;
Tseng, SS
;
資訊工程學系
;
Department of Computer Science
In this paper, we investigate the optimal assignment problem of cells in PCS (Personal Communication Service) to switches on a ATM (Asynchronous Transfer Mode) network. Given cells and switches on an ATM network (whose locations are fixed and known), the problem is to group cells into clusters and assign these clusters to switches in an optimum manner. This problem is modeled as a complex integer programming problem. Since finding an optimal solution of this problem is NP-hard, a heuristic solution model consists of three phases (Cell Pre-Partitioning Phase, Cell Exchanging Phase, and Cell Migrating Phase) is proposed. Experimental results show that Cell Exchanging and Cell Migrating Phases can really reduce total cost near 44% on average.
Smith form of FIR pseudocirculants
(2002-08-01)
Lin, YP
;
Phoong, SM
;
電控工程研究所
;
Institute of Electrical and Control Engineering
The pseudocirculant matrices have been found to be a very useful tool in the analysis and design of communication systems, e.g., precoding systems and discrete multitone transceivers. In these systems, a scalar channel P(z) is recast into a pseudocirculant channel matrix. Many important channel properties have been derived from the Smith form and the decomposition of pseudocirculants. In this letter, we will show that the Smith form of a pseudocirculant matrix can be given in terms of the zeros of the underlying finite-impulse response (FIR) channel P(z). Once the zeros of P(z) are known, the Smith form of the corresponding pseudocirculant matrix can be obtained in closed form.
Study on dopant activation of phosphorous implanted polycrystalline silicon thin films by KrF excimer laser annealing
(2002-08-01)
Tseng, CH
;
Lin, CW
;
Teng, TH
;
Chang, TK
;
Cheng, HC
The KrF excimer laser annealing of phosphorous implanted polycrystalline silicon (poly-Si) films had been investigated completely. Resistors were fabricated to measure sheet resistance of poly-Si film. The interference effect, heat absorption of capping oxide as well as transformation of poly-Si grain size during laser annealing were reported. Depending on the carrier concentrations, poly-Si exhibits different sheet resistance behavior when the excimer laser fluence is higher than the full-melt threshold fluence. The sheet resistance of poly-Si film has an abnormal increase from 5 x 10(4) to 4 x 10(6) Q/square when the excimer laser energy is higher than full-melt threshold energy. (C) 2002 Elsevier Science Ltd. All rights reserved.
A compact low-power rail-to-rail class-B buffer for LCD column driver
(2002-08-01)
Weng, MC
;
Wu, JC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper proposes a compact, low-power, and rail-to-rail class-B output buffer for driving the large column line capacitance of LCDs. The comparator used as a nonlinear element in feedback path is modified from the current-mirror amplifier, which has area and power advantages. The output buffer was realized in a 0.35 mum CMOS process. The active area of the buffer is 86 X 73.5 mum(2). With a 3.3 V supply, the measured quiescent current is 7.4 muA. The settling time for 0.05-3.25 V swing to within 0.2% is 8 mus.