Browsing by Issue Date, starting with "1998-05-01"

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Design and analysis of electrically calibrated tympanic thermometers
(1998-05-01)
Ou-Yang, M
;
Shie, JS
;
Tsao, C
;
光電工程學系
;
Department of Photonics
A new tympanic thermometer is analyzed and tested experimentally. An electrically calibrated pyroelectric detector of special configuration is employed to determine a person's body temperature. An energy-storage, power-supply-isolated capacitor is used as the electrical heating reference. The new thermometer design has an accuracy within +/-0.1 degrees C with a 90% confidence and is immune to ambient temperature, detector aging, and parameter variations. An equivalent-circuit model is established in the analysis to account for the heat exchanges among the tympanum, the surroundings, and the detector as well as for the electrothermal behavior of the detector. The model provides effective simulation of the thermometer with PSPICE. Critical parameters governing the accuracy and the Limitation of the tympanic thermometer are also pointed out by the simulation. (C) 1998 Optical Society of America.
Well supply voltage effect on escape current of guard rings in epitaxial CMOS technology
(1998-05-01)
Huang, CY
;
Chen, MJ
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
An n-well guard ring dual collector structure formed on an epitaxial substrate has been characterized and simulated. The measured I-V characteristics have exhibited that a reduction of well supply voltage from 5.0 to 1.0 V causes an increase in the escape current into the outer well by a factor of about 14, while the base and inner guard ring collector currents are hardly changed. This will influence neighboring latchup susceptibility substantially. This experimental observation can provide a new evidence of the published theory responsible for the escape current: the injected minority carriers flow through a quasi-neutral layer between the upper collecting plate and the bottom high/low junction reflecting plate. Based on this theory actual epitaxial layer thickness can be extracted with low guard ring voltages as well. Published by Elsevier Science Ltd. All rights reserved.
A dual CP slot antenna using a modified Wilkinson power divider configuration
(1998-05-01)
Tseng, WJ
;
Chung, SJ
;
電信工程研究所
;
Institute of Communications Engineering
A dual circularly polarized (CP) slot antenna based on a proposed equal-split Wilkinson power divider is presented, An offset-fed slot antenna, which was analyzed using the method of moments together with a mixed potential integral equation, was used to replace the lumped resistor in the divider. A dual CP slot antenna operating at S-band was designed and demonstrated experimentally. The antenna possessed a return loss bandwidth of 39.3%, an isolation bandwidth of 10% for VSWR <2, and 3-dB axial ratio bandwidth of 28%.
Inverse Vening Meinesz formula and deflection-geoid formula: applications to the predictions of gravity and geoid over the South China Sea
(1998-05-01)
Hwang, C
;
土木工程學系
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Department of Civil Engineering
Using the spherical harmonic representations of the earth's disturbing potential and its functionals, we derive the inverse Vening Meinesz formula, which converts deflection of the vertical to gravity anomaly using the gradient of the H function. The deflection-geoid formula is also derived that converts deflection to geoidal undulation using the gradient of the C function. The two formulae are implemented by the 1D FFT and the 2D FFT methods. The innermost zone effect is derived. The inverse Vening Meinesz formula is employed to compute gravity anomalies and geoidal undulations over the South China Sea using deflections from Seasat, Geosat, ERS-1 and TOPEX//POSEIDON satellite altimetry. The 1D FFT yields the best result of 9.9-mgal rms difference with the shipborne gravity anomalies. Using the simulated deflections from EGM96, the deflection-geoid formula yields a 4-cm rms difference with the EGM96-generated geoid. The predicted gravity anomalies and geoidal undulations can be used to study the tectonic structure and the ocean circulations of the South China Sea.
The role of partial miscibility on the properties of ternary blends of liquid crystalline copolyesters and polyetherimide
(1998-05-01)
Wei, KH
;
Tyan, HL
;
材料科學與工程學系
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Department of Materials Science and Engineering
Binary blends of liquid crystalline copoly(oxybenzoate-p-ethylene terephthalate) at molar ratio 60/40, POB-PET, and polyetherimide (PEI) were investigated with differential scanning calorimetry and polarised optical microscopy. It was found that POB-PET and PEI were partially miscible when PEI was the major component. Adding a small amount (5 phr) of POB-PET to the originally immiscible blends of liquid crystalline copoly(oxybenzoate-naphthalate) (73/27), Vectra, and PEI resulted in better interfacial adhesions between Vectra and PEI as evidenced by the morphological observations with scanning electron microscopy. The enhancement in the interfacial adhesions caused an increase in the ultimate tensile strength and the impact strength of these ternary blends of Vectra, POB-PET and PEI as compared to that of the corresponding binary blends of Vectra and PEI in an injection molding process. (C) 1998 Elsevier Science Ltd. All rights reserved.
An RNN-based prosodic information synthesizer for Mandarin text-to-speech
(1998-05-01)
Chen, SH
;
Hwang, SH
;
Wang, YR
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A new RNN-based prosodic information synthesizer for Mandarin Chinese text-to-speech (TTS) is proposed in this paper. Its four-layer recurrent neural network (RNN) generates prosodic information such as syllable pitch contours, syllable energy levels, syllable initial and final durations, as well as inter-syllable pause durations. The input layer and first hidden layer operate with a word-synchronized clock to represent current-word phonologic states within the prosodic structure of text to be synthesized. The second hidden layer and output layer operate on a syllable-synchronized clock and use outputs from the preceding layers, along with additional syllable-level inputs fed directly to the second hidden layer, to generate desired prosodic parameters. The RNN was trained on a large set of actual utterances accompanied by associated texts, and can automatically learn many human-prosody phonologic rules, including the well-known Sandhi Tone 3 F0-change rule. Experimental results show that all synthesized prosodic parameter sequences matched quite well with their original counterparts, and a pitch-synchronous-overlap-add-based (PSOLA-based) Mandarin TTS system was also used for testing of our approach. While subjective tests are difficult to perform and remain to be done in the future, we have carried out informal listening tests by a significant number of native Chinese speakers and the results confirmed that all synthesized speech sounded quite natural.
Analysis and application of a two-port aperture-coupled microstrip antenna
(1998-05-01)
Tseng, WJ
;
Chung, SJ
;
電信工程研究所
;
Institute of Communications Engineering
A two-port aperture-coupled microstrip antenna was analyzed using the method of moments together with a mixed potential integral equation (MPIE), The antenna contains two microstrip-line ports (i.e., a feeding port and a coupling port), The field coming from one microstrip line on the circuit layer is fed into the patch through an aperture on the ground plane, Part of the field is then coupled back to a second microstrip line through another aperture on the same ground. The influences of the stub lengths, along with the positions and sizes of the apertures, on the coupling power and the resonant frequency were investigated. As an application, a feedback antenna oscillator was designed using the present structure where the antenna served not only as a radiator, but also as a feedback resonator. The oscillation was stable and with a clean spectrum at the frequency of 9.79 GHz, which was only 0.2% different from the design one. An effective isotropic radiated power (EIRP) of 39 mW was achieved. The measured cross-polarized fields were at least 15 dB lower than the copolarized ones.
Magnetic force microscopy study of domain walls on a thin cobalt film
(1998-05-01)
Lin, HN
;
Chiou, YH
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Chen, BM
;
Shieh, HPD
;
Chang, CR
Two types of 180 degrees domain walls on a 115 nm cobalt film are observed by magnetic force microscopy. The surface Neel wall on top of an asymmetric Bloch wall is found inhomogeneous. with the width estimated to be around 200 nm. The width of the rhomb-structured cross-tie wall, on the other hand, is approximately 400 nm. The coexistence of these two types of domain walls indicates that their wall energies are comparable at the film thickness. (C) 1998 American institute of Physics.
管管作品三首
(1998-05-01)
管管
Growth of MgWO4 phosphor by RF magnetron sputtering
(1998-05-01)
Chu, JP
;
Hsieh, IJ
;
Chen, JT
;
Feng, MS
;
材料科學與工程學系
Magnesium tungstate (MgWO4) thin film phosphors prepared by radio frequency (RF) magnetron sputter deposition were characterized. alpha- and beta-MgWO4 were determined as the major phases in the films studied. Since the deposition rates of film were influenced by RF power. working pressure as well as oxygen content, these processing parameters played an important role in affecting the phase present in the as-deposited films. It is found that the formation of alpha-MgWO4 phase was favorable for the films grown at low deposition rates (<40 Angstrom min(-1)) whereas beta-MgWO4 was a dominant phase at high deposition rates. Substrate temperatures showed no detectable effects on the deposition rates and thus the beta-MgWO4 was the only phase present for the substrate temperature range examined. A phase formation mechanism due to the deposition rate difference is described. Post-deposition annealing significantly improved the cathodoluminescence (CL) properties of films, with annealing temperatures at 750 degrees C or above being the most effective. CL property improvement appeared to he attributed to the enhancement of crystallinity and the transformation to the stable beta-MgWO4 phase during the annealing. Annealing-induced film delamination and blisters. however, resulted in deterioration of low voltage CL properties. (C) 1998 Elsevier Science S.A. All lights reserved.
Electron-phonon scattering times in crystalline disordered titanium alloys between 3 and 15 K
(1998-05-01)
Wu, CY
;
Jian, WB
;
Lin, JJ
;
物理研究所
;
Institute of Physics
We have successfully fabricated bulk crystalline disordered titanium alloys (Ti1-xSnx, T1-xGex, and Ti0.97-xSn0.03Scx) with nominal concentration x of the order of a few at. %. The impurity atoms are gradually introduced into a titanium host to tune the degree of disorder, resulting in residual resistivities rho(0) varying from approximate to 40 to 160 mu Omega cm (corresponding to values of k(F)l approximate to 5-20, with k(F) being the Fermi wave number and l being the electron elastic mean free path). With this wide range of experimentally accessible rho(0), we are able to perform systematic studies of the disorder rho(0), or electron elastic mean free path l, behavior of the electron-phonon scattering time tau(ph). We have measured the magnetoresistivities of these alloys between 3 and 15 K, and compared our results with weak-localization theoretical predictions to extract tau(ph)(T,l) Unexpectedly, we obtain a rather diversified temperature dependence and disorder dependence of tau(ph) as follows. (a) In Ti1-xSnx alloys with rho(0) greater than or similar to 100 mu Omega cm we find 1/tau(ph)similar to T-2/l. (b) In Ti1-xSnx alloys with rho(0) less than or similar to 70 mu Omega cm we find 1/tau(ph)similar to T-3/l. (c) In Ti1-xGex alloys with 50 less than or similar to p(0) less than or similar to 130 mu Omega cm we find 1/tau(ph)similar to T-3 in some alloys and 1/tau(ph)similar to T-4 in others, while at a given temperature 1/tau(ph) is essentially independent of disorder. (d) In Ti0.97-xSn0.03Scx alloys with 55 less than or similar to rho(0) less than or similar to 75 mu Omega cm we obtain 1/tau(ph)similar to T-2. These experimental observations altogether imply that electron-phonon interactions in the presence of strong impurity scattering are very sensitive to the local material environment (the microscopic quality) of a particular sample system, which might be variously modulated with the doping of different kinds of impurity atoms. Our results are compared with existing theoretical predictions for electron-phonon scattering in disordered conductors.
管管作品三首
(1998-05-01)
管管
Application of center manifold reduction to nonlinear system stabilization
(1998-05-01)
Liaw, DC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
The Center Manifold Theorem is applied to the local feedback stabilization of nonlinear systems in critical cases. The paper addresses two particular critical cases of which the system linearization at the equilibrium point of interest is assumed to possess either a simple zero eigenvalue or a complex conjugate pair of simple and pure imaginary eigenvalues. In either case, the noncritical eigenvalues are taken to be stable. The results on stabilizability and stabilization are given explicitly in terms of the nonlinear model of interest in its original form, i.e., before reduction to the center manifold. Moreover, the formulation given in this paper uncovers connections between results obtained using the center manifold reduction and those of an alternative approach. (C) 1998 Elsevier Science Inc. All rights reserved.
管管作品三首
(1998-05-01)
管管
Erasable phase change disks with super resolution capability by pulse-readout
(1998-05-01)
Liu, JR
;
Shieh, HPD
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光電工程學系
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Department of Photonics
Erasable thermal phase change super resolution (EPSR) disks composed of mask and recording layers can be Fabricated with a "below-diffraction-limited": aperture within the readout spot to achieve optical super resolution. The formation of the aperture and the readout signal on the EPSR disk were analyzed. The feasibility of the designed EPSR disks was evaluated by thermal simulation. A carrier-to-noise-ratio (CNR) of 32 dB at mark size of 0.4 mu m, 8 dB higher than that in a conventional disk, was obtained by applying pulse-readout to the EPSR disks at a wavelength of 780 nm and numerical aperture of 0.55.
Conduction mechanisms in amorphous and crystalline Ta2O5 thin films
(1998-05-01)
Ezhilvalavan, S
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Electrical properties and leakage current mechanisms of amorphous and polycrystalline tantalum pentoxide (Ta2O5) films were studied. Ta2O5 thin films were deposited on Pt/SiO2/n-Si substrate by reactive magnetron sputtering and then annealed at temperatures ranging from 500 to 800 degrees C for 30 min in O-2. The as-deposited films were amorphous and showed good electrical properties in terms of a dielectric constant of about 31 and leakage current density of 10(-10) A/cm(2) at 100 kV/cm. The leakage current flowing through Ta2O5 film increases from 10(-10) to 10(-7) A/cm(2) following the annealing. The conduction mechanism at low electric fields (100 kV/cm) is due to Ohmic conduction. On the other hand Schottky mechanism dominates at the intermediate fields (100-350 kV/cm) and Poole-Frenkel becomes predominant at high fields (>350 kV/cm). The increase in leakage current density in the crystallized film is due to Si penetrated into the Ta2O5 grain and grain boundary from the underlying SiO2/n-Si substrate. (C) 1998 American Institute of Physics.
Coherent interference suppression with complementally transformed adaptive beamformer
(1998-05-01)
Lee, TS
;
Lin, TT
;
電信工程研究所
;
Institute of Communications Engineering
This paper proposes a beamforming scheme for suppressing coherent interference with an array of arbitrary geometry. The scheme first uses estimates of the source directions to construct a transformation, which removes the desired signal while retaining the coherent interference. Optimum beamforming is then performed on the transformed data containing only interference and noise to produce the maximum output signal-to-interference-plus-noise ratio (SINR), Analysis and numerical results demonstrate that the proposed complementally transformed beamformer significantly outperforms the conventional multiply constrained minimum variance (MCMV) beamformers.
Circular chromatic numbers and fractional chromatic numbers of distance graphs
(1998-05-01)
Chang, GJ
;
Huang, LL
;
Zhu, XD
;
應用數學系
;
Department of Applied Mathematics
This paper studies circular chromatic numbers and fractional chromatic numbers of distance graphs G(Z, D) for various distance sets D. In particular, we determine these numbers for those D sets of size two, for some special D sets of size three, for D = {1, 2,..., m, n} with 1 less than or equal to m < n, for D = {q, q + 1,..., p} with q less than or equal to p, and for D = {1, 2,..., m} - {k} with 1 less than or equal to k less than or equal to m. (C) 1998 Academic Press.
Evaluation of buckling and first-ply failure, probabilities of composite laminates
(1998-05-01)
Lin, SC
;
Kam, TY
;
Chu, KH
;
機械工程學系
;
Department of Mechanical Engineering
A procedure for failure probability evaluation of composite laminates subjected to in plane loads is proposed. The material properties, fiber angles and layer thicknesses of the laminates are treated as random variables in the reliability analysis. The statistics of first-ply failure loads and buckling strengths of the laminates are determined via the stochastic finite element method. The failure probabilities of the laminates which are susceptible to buckling and first-ply failure are computed using the statistics obtained in the stochastic finite element analysis. The feasibility and accuracy of the present approach are validated using the results obtained via the Monte-Carlo method. A number of examples of reliability analysis of composite laminates subject to in-plane loads are given to illustrate the applications of the procedure. (C) 1998 Elsevier Science Ltd.
Fatigue reliability evaluation for composite laminates via a direct numerical integration technique
(1998-05-01)
Kam, TY
;
Chu, KH
;
Tsai, SY
;
機械工程學系
;
Department of Mechanical Engineering
A direct numerical integration technique for evaluating Fatigue reliability of composite laminates under varying stress amplitudes is presented. A number of cumulative damage models are adopted to construct the limit state equation for the laminates in the reliability analysis. Existing fatigue life distributions of composite laminates under cyclic stresses of constant amplitude are used in the reliability assessment of the composite laminates under varying stress amplitudes. The accuracy of the proposed method in fatigue reliability prediction is then verified by experimental Fatigue life data of varying stress amplitudes. A comparison between the present method and the modified beta-method is also made to illustrate the suitability of the present method in fatigue reliability prediction. (C) 1998 Elsevier Science Ltd.