Browsing by Issue Date, starting with "2000-07-01"

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Direction of arrival estimation based on phase differences using neural fuzzy network
(2000-07-01)
Shieh, CS
;
Lin, CT
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A new high-resolution direction of arrival (DOA) estimation technique using a neural fuzzy network based on phase difference (PD) is proposed in this paper. The conventional DOA estimation method such as MUSIC and MLE, are computationally intensive and difficult to implement in real time. To attach these problems, neural networks have become popular for DOA estimation in recent years. However, the normal neural networks such as multilayer perceptron (MLP) and radial basis function network (RBFN) usually produce the extra problems of low convergence speed and/or large network size (i.e., the number of network parameters is large). Also, the way to decide the network structure is heuristic. To overcome these defects and take use of neural learning ability, a powerful self-constructing neural fuzzy inference network (SONFIN) is used to develop a new DOA estimation algorithm in this paper. By feeding the PD's of received radar-array signals, the trained SONFIN can give high-resolution DOA estimation. The proposed scheme is thus called PD-SONFIN, This new algorithm avoids the need of empirically determining the network size and parameters in normal neural networks due to the powerful on-line structure and parameter learning ability of SONFIN, The PD-SONFIN can always find itself an economical network size in fast learning process. Our simulation results show that the performance of the new algorithm is superior to the RBFN in terms of convergence accuracy, estimation accuracy, sensitivity to noise, and network size.
Prediction-based lower triangular transform
(2000-07-01)
Phoong, SM
;
Lin, YP
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper, a new nonunitary transform called the prediction-based lower triangular transform (PLT) is introduced for signal compression. The new transform has the same decorrelation property as the Kahurnen-Loeve transform (KLT), but its implementational cost is less than one half of KLT, Compared with the KLT, the design cost of an M x M PLT is much lower and is only of the order of O(M-2). Moreover, the PLT can be factorized into simple building blocks, Using two different factorizations, we introduce two minimum noise structures that have roughly the same complexity as the direct implementation of PLT. These minimum noise structures have the following properties: 1) Its noise gain is unity even though the transform is nonunitary; 2) perfect reconstruction is structurally guaranteed; 3) it can be used for both. lossy/lossless compression. We will show that the coding gain of PLT implemented using the minimum noise structure is the same as that of KLT. Furthermore, universal transform coders using PLT are derived. For AR(1) process, the M x M PLT has a closed form and needs only (M - 1) multiplications and additions.
Plasma-induced charging damage in ultrathin (3-nm) gate oxides
(2000-07-01)
Chen, CC
;
Lin, HC
;
Chang, CY
;
Liang, MS
;
Chien, CH
Plasma-induced damage in various 3-nm-thick gate oxides (i.e., pure oxides and N2O-nitrided oxides) was investigated by subjecting both nMOS and pMOS antenna devices to a photoresist ashing step after metal pad definition. Both charge-to-break-down and gate leakage current measurements indicated that large leakage current occurs at the wafer center as well as the wafer edge for pMOS devices, while only at the wafer center for nMOS devices. These interesting observations could be explained by the strong polarity dependence of ultra-thin oxides in charge-to breakdown measurements of nMOS devices. In addition, pMOS devices were found to be more susceptible to charging damage, which can be attributed to the intrinsic polarity dependence in tunneling current between n- and p-MOSFET,s. More importantly, our experimental results demonstrated that stress-induced leakage current (SILC) caused by plasma damage can be significantly suppressed in N2O-nitrided oxides, compared to pure oxides, especially for pMOS devices. Finally, nitrided oxides were also found to be more robust when subjected to high temperature stressing. Therefore, nitrided oxides appear to be very promising for reducing plasma charging damage in future ULSI technologies employing ultrathin gate oxides.
Nature of the 45 degrees vortex lattice reorientation in tetragonal superconductors
(2000-07-01)
Knigavko, A
;
Kogan, VG
;
Rosenstein, B
;
Yang, TJ
;
電子物理學系
The transformation of the vortex lattice in a tetragonal superconductor which consists of the 45 degrees reorientation relative to the crystal axes is studied using the nonlocal London model. It is shown that the reorientation occurs as two successive second order (continuous) phase transitions. The transition magnetic fields are calculated for a range of parameters relevant for borocarbide superconductors in which the reorientation has been observed.
Identification, purification, and characterization of a thermophilic imidase from pig liver
(2000-07-01)
Su, TM
;
Yang, YS
;
生物科技學系
;
Department of Biological Science and Technology
This study investigates thermophilic imidase activity of the liver. We demonstrate that imidase catalyzes the hydrolysis of imides at a temperature substantially higher than that of its native environment. Then, a thermophilic imidase is purified to homogeneity from pig liver, and its thermoproperties are studied. About 2500-fold of purification and 15% yield of imidase activity are obtained after ammonium sulfate precipitation, octyl, DEAE, chelation, and gel filtration chromatography, While avoiding heat treatment for the protein purification, this study also indicates that only one enzyme is responsible for the imidase activity. This homogenous enzyme prefers to catalyze hydrolysis of imides at above 60 degrees C rather than at the body temperature of a pig. Although stable at below 50 degrees C, imidase quickly loses its activity at above 65 degrees C. Thus, the temperature effect on imidase activity is limited mainly by its thermostability, Substrate specificity of imidase is also temperature dependent. Our results demonstrate that the hydrolysis of physiological substrates is the most temperature dependent and that of hydantoins is the least temperature dependent. When increasing the reaction temperature from 25 to 60 degrees C, specific activities increase 50- and 60-fold for dihydrouracil and dihydrothymine, respectively. The temperature effect on the K-m and V-max of imidase is substrate dependent. (C) 2000 Academic Press.
Improvement in wafer temperature uniformity and flow pattern in a lamp heated rapid thermal processor
(2000-07-01)
Yin, CP
;
Hsiao, CC
;
Lin, TF
;
機械工程學系
;
Department of Mechanical Engineering
An experimental lamp heated, rapid thermal processor (RTP) for an 8-in single silicon wafer was designed and established to investigate the thermal and flow characteristics in the processing chamber by transient temperature measurement and flow visualization. Experiments were carried out to explore the effects of placing a highly conducting copper plate right below the wafer on the uniformity of the wafer temperature and effects of the showerhead on the resulting flow distribution in the processing chamber. The measured data indicated that adding the copper plate can effectively reduce the nonuniformity of the wafer temperature. Besides, using a showerhead with finer holes in it results in a better flow distribution in the processor. (C) 2000 Elsevier Science B.V. All rights reserved.
High temperature formed SiGeP-MOSFET's with good device characteristics
(2000-07-01)
Wu, YH
;
Chin, A
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We have used a simple process to fabricate Si0.3Ge0.7/Si p-MOSFET's. The Si0.3Ge0.7 is formed using deposited Ge followed by 950 degrees C rapid thermal annealing and solid phase epitaxy that is process compatible with existing VLSI. Hole mobility of 250 cm(2)/Vs is obtained from Si0.3Ge0.7 p-MOSFET that is similar to two times higher than Si control devices and results in a consequent substantially higher current drive. The 228 Angstrom Si0.3Ge0.7 thermal oxide grown at 1000 degrees C has a high breakdown field of 15 MV/cm, low interface trap density (D-it) of 1.5 x 10(11) eV(-1) cm(-2), and low oxide charge of 7.2 x 10(10) cm(-2). The source-drain junction leakage after implantation and 950 degrees C RTA is also comparable with Si counterpart.
An analysis for measurement of thermal diffusivity components of anisotropic platelike samples by AC calorimetric method
(2000-07-01)
Sheu, LJ
;
Lin, JD
;
機械工程學系
;
Department of Mechanical Engineering
This work examines the effects of anisotropy and transparency on measurements of thermal diffusivity components with an ac calorimetric method associated with laser heating. Analytical results indicate that the region where the two-dimensional effect occurs increases with the decrease of the ratio of cross-plane to in-plane thermal diffusivity. The region also increases with the optical thickness of the sample. The linear relations, as indicated by a decay constant from which the cross-plane thermal diffusivity is deduced, are not obtained for media of both optically moderate and thin thickness, while at sufficiently large optical thickness, anisotropy and two-dimensional effects are found insignificant.
An automatic controller extractor for HDL descriptions at the RTL
(2000-07-01)
Liu, CNJ
;
Jou, JY
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Extracting controlling finite-state machines can significantly reduce state space and thereby speed functional verification. The controller extraction algorithm uses an approach that frees it from restrictions on HDL code writing style.
Synthesis of dextran-(5-FU)-galactosamine conjugate through a tripeptide spacer group and its in vitro properties
(2000-07-01)
Guu, JA
;
Juang, TM
;
Hsiue, GH
;
Chiu, HC
;
應用化學系
In this study, conjugation of 5-fluorouracil (5-FU) and galactosamine with dextran via Glycyl-L-Leucyl-Glycine (Gly-Leu-Gly) tripeptidyl spacer was performed first by activation of dextran with p-nitrophenyl chloroformate, followed by aminolysis of Glycyl-L-Leucyl-Glycyl-5flurouracil (Gly-Leu-Gly-5-FU) and galactosamine with activated dextrans. Preparation of Gly-Leu-Gly-5-FU was carried out by sequential reactions of peptide synthesis in solution phases and coupling with 5-FU in the presence of diethylphosphoric cyanide. The release of 5-FU from the conjugates upon the exposure of polymeric prodrugs to papain implied that the attachment of 5-FU with the tripeptidyl spacer, Gly-Leu-Gly, was capable of being liberated by cathepsin B in lysosomes of targeted cells. The observation that the cytoxicity in vitro from the incubation of dextran-5-FU conjugate containing galactosamine residues with Hep-3B cells is higher than that in the void of galactosamine indicated the occurrence of specific binding of the targeting moieties with its receptors on cell membrane, leading to an enhanced cellular uptake of the conjugate via receptor-mediated endocytosis.
Digital multisignature schemes for authenticating delegates in mobile code systems
(2000-07-01)
Shieh, SP
;
Lin, CT
;
Yang, WB
;
Sun, HM
;
資訊工程學系
In this paper, we motivate the need for efficient multisignature schemes in delegated mobile services. With the schemes, delegates can be identified and delegated accesses can be controlled. First, we give a new digital signature scheme with message recovery. Based on the digital signature scheme, two digital multisignature schemes are proposed: the parallel multisignature scheme and the serial multisignature scheme. The parallel multisignature scheme allows each user to sign the same message separately and independently, and then combines all individual signatures into a multisignature, The serial multisignature scheme allows a group of users to sign the message serially, and does not need to predetermine the signing order. Both multisignature schemes tan withstand the attacks that aim to forge the signatures or to get the private kegs of the signers.
Existence and multiplicity of traveling waves in a lattice dynamical system
(2000-07-01)
Hsu, CH
;
Lin, SS
;
應用數學系
;
Department of Applied Mathematics
This work proves the existence and multiplicity results of monotonic traveling wave solutions for some lattice differential equations by using the monotone iteration method. Our results include the model of cellular neural networks (CNN). In addition to the monotonic traveling wave solutions, non-monotonic and oscillating traveling wave solutions in the delay type of CNN are also obtained. (C) 2000 Academic Press.
Sintering BaTi4O9/Ba2Ti9O20-based ceramics by glass addition
(2000-07-01)
Cheng, CM
;
Yang, CF
;
Lo, SH
;
Tseng, TY
;
電子工程學系及電子研究所
After calcining BaCO3 + 4TiO(2) mixed powder at 1150 degrees C for 2 h, BaTi4O9 is the major phase, Ba4Ti13O30 and BaTi5O11 are minor phases. After calcining 2BaCO(3) + 9TiO(2) mixed powder at 1200 degrees C for 10 h, Ba2Ti9O20 is the major phase, BaTi4O9 and BaTi5O11 are the minor phases. The calcining powders are used as the BaTi4O9 and Ba2Ti9O20 precursors. MgO-CaO-SiO2-Al2O3 (MCAS) composite glass powder, fabricated by sol-gel method, is used as the low melting addition to lower the sintering temperatures of BaTi4O9 and Ba2Ti9O20 dielectric. The addition of MCAS glass does not inhibit the residual satellite phases to transform into BaTi4O9 and Ba2Ti9O20. For MCAS-doped BaTi4O9 and Ba2Ti9O20 ceramics the major phases are BaTi4O9 and Ba2Ti9O20, cordierite is observed as minor phase. The temperatures needed to densify the BaTi4O9 and Ba2Ti9O20 ceramics are lowered down with the increase amount of MCAS glass addition. For BaTi4O9 and Ba2Ti9O20 ceramics, both the densities and the dielectric constants (at 1 MHz) increase with the sintering temperature and decrease with the amount of MCAS glass addition. (C) 2000 Elsevier Science Ltd. All rights reserved.
A wavelet multiresolution compression technique for 3D stereoscopic image sequence based on mixed-resolution psychophysical experiments
(2000-07-01)
Chang, PR
;
Wu, MJ
;
電信工程研究所
;
Institute of Communications Engineering
Three-dimensional visual communications, made through the use of stereoscopic images, are able to achieve total display realism. In order to create a 3D system with two images (left and right) that should be transmitted simultaneously, the large amount of information contained in the images should be reduced, and an efficient coding appropriate for stereoscopic images is developed. Stereoscopic image sequence compression involves the exploitation of the spatial redundancy between the left and right image frames to achieve the compression ratio higher than that are by the independent compression of the two frames. In order to further achieve the higher compression ratio, in this paper, we employ the mixed-resolution psychophysical experiments to the stereo image compression. The experiments have shown that a stereo image pair with one high-resolution image and one lower-resolution image is sufficient to provide good stereoscopic depth perception. Thus, one image sequence is compressed independent of the other sequence using the motion compensation, while the other sequence is estimated at a lower resolution from this stream using the low-resolution disparity compensation. To implement the mixed-resolution coding, a wavelet multiresolution framework has been adopted to facilitate such an estimation of motion and disparity vectors at different resolutions. Experimental results indicate that the compression ratio for a typical stereoscopic image sequence is about 90, without any significant loss in the perceived 3D stereoscopid image quality. (C) 2000 Elsevier Science B.V. All rights reserved.
Effects of a new combination of additives in electroplating solution on the properties of Cu films in ULSI applications
(2000-07-01)
Hu, JC
;
Chang, TC
;
Wu, CW
;
Chen, LJ
;
Hsiung, CS
Effects of a new combination of additives in acid electroplating solution on the properties of Cu thin films have been investigated, The electroplated Cu films exhibit an excellent superfilling behavior. 0.18 mu m vias with an aspect ratio exceeding 5 were filled completely without any void or seam. Strong (111) texture was found for the electroplated Cu films. The resistivity of a 450-nm-thick Cu film was measured to be 1.84 mu Omega cm. (C) 2000 American Vacuum Society. [S0734-2101(00)08004-0].
Cellular neural networks: Local patterns for general templates
(2000-07-01)
Hsu, CH
;
Juang, J
;
Lin, SS
;
Lin, WW
;
應用數學系
This work investigates the mosaic local patterns for cellular neural networks with general templates. Our results demonstrate that the set of templates can be divided into many finite regions. In each region, the same family of local patterns can be generated. Conversely, our results further demonstrate that some templates can realize a family of local patterns which can be linearly separated by a hyperplane in the configuration space. This study also proposes algorithms for verifying the linear separability for a given family of local patterns and, when it is separable, for obtaining the associated template.
Ultrafast dynamics in Pr-doped and oxygen-deficient YBCO films by femtosecond spectroscopy
(2000-07-01)
Wu, KH
;
Luo, CW
;
Juang, JY
;
Uen, TM
;
Gou, YS
We have systematically measured the transient reflectivity (Delta R/R) in Pr-doped YBCO (PrxY1-xBa2Cu3O7) and partially oxygen deficient YBCO (YBa2Cu3O7-delta) thin films at temperatures ranging from 300 to 12 K by using the femtosecond pump-probe technique. Measurements performed at low temperatures indicate that the magnitude, polarity, and relaxation time of the transient reflectivity is strongly dependent on the photon energy and pumping intensity of the optical excitation, the ambient temperature, and the doping level of the superconducting thin films. Moreover, the temperature dependence of the Fermi-level position was also observed. (C) 2000 Elsevier Science B.V. All rights reserved.
High-speed booth encoded parallel multiplier design
(2000-07-01)
Yeh, WC
;
Jen, CW
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper presents a design methodology for high-speed Booth encoded parallel multiplier. For partial product generation, we propose a new modified Booth encoding (MBE) scheme to improve the performance of traditional MBE schemes. For final addition, a new algorithm is developed to construct multiple-level conditional-sum adder (MLCSMA). The proposed algorithm can optimize final adder according to the given cell properties and input delay profile. Compared with a binary tree-based conditional-sum adder, the speed performance improvement is up to 25 percent. On average, the design developed herein reduces the total delay by 8 percent for parallel multiplier. The whole design has been verified by gate level simulation.
Design and analysis of a growable multicast ATM switch
(2000-07-01)
Wang, KC
;
Cheng, MH
;
資訊工程學系
;
Department of Computer Science
This work designs and analyzes a cost-effective growable multicast asynchronous transfer mode (ATM) switch that has a new grouping network structure. The proposed switch can easily be enlarged by using more stages, since both cell routing and contention resolution are designed to distribute ol er switch elements. Experimental results indicate that, by allowing valid cells to enter grouping networks from two directions (the west and north sides), the modular ATM sa itch proposed herein not only meets the ATM performance requirements for both unicasting and multicasting but also uses fen er switch elements and has a shorter cell delay than the ATM switch.
Characteristics of instantaneous resonant modes in simple dense fluids with short-ranged repulsive interactions
(2000-07-01)
Wu, TM
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Ma, WJ
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Chang, SL
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物理研究所
;
Institute of Physics
We manifest the characteristics of the low-frequency, quasilocalized instantaneous normal modes, named as the instantaneous resonant modes (IRMs), in simple dense fluids with short-ranged repulsive interactions. The analyses include the potential energy profiles of the IRMs, and the local geometric structures and the number of the interacting neighbors of the particles at which the centers of the quasilocalization are located. We conclude that an IRM is created due to fluctuations in the local density, and has a barely-isolated center, which slightly interacts with one or two nearest neighbors, and the potential energy profile of an IRM is basically single-well with strong anharmonicity. The differences in character between the IRMs and the high-frequency localized instantaneous normal modes are also examined. Based on the barely isolated center picture, a necessary criterion for the occurrence of the IRMs is proposed. While only the imaginary-frequency IRMs are found in dense fluids with purely repulsive interactions satisfying the criterion, a tiny attractive well in the pair potential allows the occurrence of the real-frequency IRMs. The physical systems to detect the presence of the IRMs are discussed. (C) 2000 American Institute of Physics. [S0021-9606(00)50225-6].