Browsing by Issue Date, starting with "1998-10-07"

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Capillary electrophoresis, potentiometric and laser excited luminescence studies of lanthanide(III) complexes of 1,7-dicarboxymethyl-1,4,7,10-tetraazacyclododecane (DO2A)
(1998-10-07)
Chang, CA
;
Chen, YH
;
Chen, HY
;
Shieh, FK
;
生物科技學系
The protonation constants of the ligand 1,7-dicarboxymethyl-1,4,7,10-tetraazacyclododecane (DO2A) were redetermined by the potentiometric pH titration method (log K 10.94, 9.55, 3.85, 2.55) and the macrocycle ring protonation sites have also been confirmed by NMR techniques to be the secondary amine nitrogen atoms. The stability constants of calcium(II) and all trivalent lanthanide (Ln(3+)) metal complexes of DO2A (Ca2+, log K-ML 7.16; Ln(3+), log K-ML 10.94-13.31) were determined by the potentiometric pH titration and capillary electrophoresis methods, respectively. In general, the stabilities of the Ln(DO2A)(+) complexes increase with increasing atomic number for the lighter lanthanides (La3+-Sm3+) and remain relatively unchanged for the heavier lanthanides (Eu3+-Lu3+). Laser-excited spectroscopy of the F-7(o) --> D-5(o) transition of Eu3+ is used to study the aqueous Eu3+-DO2A complex system. At low pH (e.g. pH 5-6) Eu3+ forms a 1:1 species with the ligand DO2A, presumably Eu(DO2A)(H2O)(q)(+), where q is the number of inner-sphere coordinated water molecules. As the solution pH increases the hydrolysis product, Eu(DO2A)(OH)(H2O)(q-1), is formed. Lifetime measurements of each species in H2O and D2O allow the determination of the corresponding number of inner-sphere coordinated water molecules to be 3.0 and 2.6, consistent with the proposed structures (i.e. q = 3). The first hydrolysis constant (pK(h)) is estimated to be 8.1 +/- 0.3.
Interfacial reactions between zirconia and titanium
(1998-10-13)
Lin, KF
;
Lin, CC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Effects of high-resistivity, low-temperature layer in transient capacitance measurements of GaAs n-i-p structures
(1998-10-15)
Chen, JF
;
Wang, PY
;
Chen, NC
;
電子物理學系
;
Department of Electrophysics
Deep-level transient spectroscopy and transient capacitance measurements are performed on a molecular-beam-epitaxially grown GaAs n-i-p diode with a 2000-Angstrom-thick low-temperature OLT)-grown layer immersed in its intrinsic region. The transient capacitance measurements reveal that the time constant and activation energy are the same for both the emission and capture processes. An equivalent circuit based on capacitance-frequency spectra is derived and used to obtain the resistivity values of the LT layer that are in agreement with experimental results. It is concluded that the transient capacitance observed corresponds to the resistance-capacitance time constant due to the LT-layer. In addition, the value of the activation energy is explained based on the equivalent circuit.
The preferable resonators for Kerr-lens mode-locking determined by stability factors of their iterative maps
(1998-10-15)
Wei, MD
;
Hsieh, WF
;
Sung, CC
;
光電工程學系
;
Department of Photonics
The generalized stability factor of a general resonator was obtained from its iterative map based on the linear stability analysis. Since a physical system tends to stay with high stability, the preferred resonator for Kerr-lens mode-locking (KLM) is determined by the relative stability between KLM and CW operations. With this criterion the preferable KLM regions agree with the previous experimental self-starting regions when the Ken medium is located around the center of the resonator. (C) 1998 Elsevier Science B.V. All rights reserved.
Preparation and characteristics of Bi-Pb-Sr-Ca-Cu-O superconducting films by spray pyrolysis and post-annealing
(1998-10-15)
Koo, HS
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Two kinds of high-T-c superconducting films, Bi1.8Pb0.2Sr2Ca2Cu3Oy and Bi2PbSr2Ca2Cu3Oy, were prepared by spray pyrolysis and postannealing with the aid of Bi-based bulk. Highly c-oriented and nearly single-phase 2223 high-T-c Bi-based superconducting films can be achieved for the as-sprayed Bi1.8Pb0.2Sr2Ca2Cu3Oy and the Bi2PbSr2Ca2Cu3Oy films annealed at 845 degrees C for 20 h. X-ray diffraction (XRD) patterns exhibit amorphous-like phases with microcrystals for the as-sprayed films and the transformation of amorphous-like phase into crystalline high-T-c (2223), low-T-c (2212) and Ca2PbO4 phases for the resultant films. For as-sprayed films, post-annealing in the closed system with Bi-based bulk sources is favourable to the formation of 2223 phase; on the contrary, the 2212 phase is formed in the open system, as demonstrated by XRD and scanning electron microscopy (SEM). SEM and XRD analyses show a plate-like microstructure for the 2223 phase and a needle-like one for the 2212 phase. This phenomenon explains that compensation and diffusion of Bi-based bulk sources into the as-sprayed films help in the formation of 2223 phase and these processes are more efficient in the closed system. The resultant film shows a high critical transition temperature (T-c,T-zero) of 104 K and a critical current density (J(c)) of 1.8 x 10(4) A/cm(2). (C) 1998 Elsevier Science S.A. All rights reserved.
The preferable resonators for Kerr-lens mode-locking determined by stability factors of their iterative maps
(1998-10-15)
Wei, MD
;
Hsieh, WF
;
Sung, CC
;
光電工程研究所
;
Institute of EO Enginerring
The generalized stability factor of a general resonator was obtained from its iterative map based on the linear stability analysis. Since a physical system tends to stay with high stability, the preferred resonator for Kerr-lens mode-locking (KLM) is determined by the relative stability between KLM and CW operations. With this criterion the preferable KLM regions agree with the previous experimental self-starting regions when the Ken medium is located around the center of the resonator. (C) 1998 Elsevier Science B.V. All rights reserved.
Power equalized wavelength-selective fiber lasers using fiber Bragg gratings
(1998-10-15)
Liaw, SK
;
Lee, CC
;
Ho, KP
;
Chi, S
;
光電工程學系
A fiber Bragg grating (FBG) based multi-wavelength ring laser is experimentally investigated in this paper. The lasing wavelengths can be dynamically selected by using a 1 x N optical switch. Micro-bender between FBGs is used as variable attenuator to equalize the output power for each lasing wavelength. By using passive multi-ring cavities (MRC) method, single- or dual-wavelength laser of equal output power is demonstrated for a signal-to-noise ratio (SNR) of 63 dB and a narrow linewidth of 3 kHz. (C) 1998 Elsevier Science B.V. All rights reserved.
A weight-assessing method with habitual domains
(1998-10-16)
Tzeng, GH
;
Chen, TY
;
Wang, JC
;
管理學院
;
College of Management
Weights of criteria are the important factors in decision-making. However, from a behavioral perspective, traditional weighting methods account for too few factors to deal with decisions properly. Based on the behavior mechanism and the theory of habitual domains, this study is undertaken to develop a new weight-assessing model that treats decisionmaking as a dynamically adjusting process proceeding from the ideal to actual states. The new model is built upon the dynamic analysis for the connectivities between criteria instead of the static analysis of traditional models. Finally, we have studied Taipei City motorcycle users, mode-choice behavior through questionnaire in order to show the applicability of the new model. From the empirical results, it is found that our weight-assessing method has significant application potential in practice. (C) 1998 Elsevier Science B.V. All rights reserved.
管管老來得子取名叫「領風」
(1998-10-25)
江中明
Synthesis of new type diacetal trioxa-cage compounds via an intramolecular nucleophilic addition of the hydroxy group to the carbonyl oxide group
(1998-10-30)
Wu, HJ
;
Chao, CS
;
Lin, CC
;
應用化學系
;
Department of Applied Chemistry
The synthesis of diacetal trioxa-cage compounds with a new type of skeleton is reported. Ozonolysis of the diols 2a-f, 21, 24, and 33 in CH2Cl2 at -78 degrees C followed by reduction with Me2S gave the diacetal trioxa-cages 3a-f, 22, 25, and 34 in 70-80% yields, respectively. A mechanism via an intramolecular nucleophilic addition of the hydroxy group of the diols to the carbonyl oxide group is proposed for the formation of the diacetal trioxa-cages. The effect of the number of carbon atoms at the bridge of the diols on the formation of the diacetal trioxa-cage skeleton was examined. Ozonolysis of the diols 13 and 15 under the same reaction conditions gave compounds 16 and 18, respectively. No detectable amount of the trioxa-cages 17 and 19 was obtained. For the synthesis of the diacetal trioxa-cages 28a-c and 31, which possess an alkene bond intact, ozonolysis of the diols 27a-c and 30 was performed by controlling the amount of ozone.
Synthesis of new type diacetal trioxa-cage compounds via an intramolecular nucleophilic addition of the hydroxy group to the carbonyl oxide group
(1998-10-30)
Wu, HJ
;
Chao, CS
;
Lin, CC
;
應用化學系
;
Department of Applied Chemistry
The synthesis of diacetal trioxa-cage compounds with a new type of skeleton is reported. Ozonolysis of the diols 2a-f, 21, 24, and 33 in CH2Cl2 at -78 degrees C followed by reduction with Me2S gave the diacetal trioxa-cages 3a-f, 22, 25, and 34 in 70-80% yields, respectively. A mechanism via an intramolecular nucleophilic addition of the hydroxy group of the diols to the carbonyl oxide group is proposed for the formation of the diacetal trioxa-cages. The effect of the number of carbon atoms at the bridge of the diols on the formation of the diacetal trioxa-cage skeleton was examined. Ozonolysis of the diols 13 and 15 under the same reaction conditions gave compounds 16 and 18, respectively. No detectable amount of the trioxa-cages 17 and 19 was obtained. For the synthesis of the diacetal trioxa-cages 28a-c and 31, which possess an alkene bond intact, ozonolysis of the diols 27a-c and 30 was performed by controlling the amount of ozone.
The effect of native oxide on thin gate oxide integrity
(1998-11-01)
Chin, A
;
Lin, BC
;
Chen, WJ
;
Lin, YB
;
Thai, C
We have studied the effect of native oxide on thin gate oxide integrity. Much improved leakage current of gate oxide can be obtained by in situ desorbing the native oxide using a HF-vapor treated and H-2 backed process. Furthermore, extremely sharp interface between oxide and Si is obtained, and good oxide reliability is achieved even under a high current density stress of 11 A/cm(2) and a large charge injection of 7.0 x 10(4) C/cm(2). The presence of native oxide will increase the interface roughness, gate oxide leakage current and stress-induced hole trap.
An extraction method to determine interconnect parasitic parameters
(1998-11-01)
Chao, CJ
;
Wong, SC
;
Chen, MJ
;
Liew, BK
;
電子工程學系及電子研究所
Interconnect parasitic parameters in integrated circuits have significant impact on circuit speed. An accurate monitoring of these parameters can help to improve interconnect performance during process development, provide information for circuit design, or give useful reference for circuit failure analysis. Existing extraction methods either are destructive (such as SEM measurement) or can determine only partial parasitic parameters (such as large capacitor measurement), In this paper, we present a new method for extracting interconnect parasitic parameters, which can simultaneously determine the interlayer and intralayer capacitances, line resistance, and effective line width. The method is based on two test patterns of a same structure with different dimensions. The structure consumes less wafer area than existing methods. The method shows good agreement with SEM measurement of dielectric thickness in both nonglobal planarized and chemical-mechanical polished processes, and gives accurate prediction of the process spread of a ring oscillator speed over a wafer.
DMTS: A distributed multimedia teleworking system
(1998-11-01)
Yuang, MC
;
Liu, JG
;
Chen, YG
;
Liu, JC
;
資訊工程學系
Multimedia systems combine a variety of information sources, such as voice, graphics, animation, images, and full-motion video, into a wide range of applications. The paper initially categorizes existing multimedia applications into three classes: noninteractive-oriented, interactive-oriented client-server-based, and interactive-oriented peer-party-based. In particular, the paper examines interactive-oriented applications and provides an in-depth survey of the media synchronization problem for the design of these applications. The paper then presents our prototyping system, called the Distributed Multimedia Teleworking System (DMTS), which allows two or more remote systems in collaboration to access and modify multimedia data through a network in a fully synchronous fashion. The system has been developed over TCP/IP and an FDDI network, using an XVideo D/A card. The media supported by DMTS include text, graphics, voice, and video. DMTS employs a master-slave collaboration model to maintain the coherence of the text and graphics data being simultaneously modified. Moreover, DMTS also adopts effective mechanisms to reduce skew (asynchrony) and jitter delays between video and voice streams. Finally, the paper demonstrates that DMTS achieves a maximum throughput of 13 frames per second, and reveals that the throughput bottleneck resides in the hardware capture and D/A processing of video frames.
Differential conductance of a saddle-point constriction with a time-modulated gate-voltage
(1998-11-01)
Tang, CS
;
Chu, CS
;
電子物理學系
;
Department of Electrophysics
This work investigates how a time-modulated gate-voltage influences the differential conductance G of a saddle-point constriction. The constriction is modeled by a symmetric saddle-point potential and the time-modulated gate-voltage is represented by a potential of the form V(0)Theta(a/2 - x - x(c)) cos(omega t). For h omega less than half of the transverse subband energy level spacing, gate-voltage-assisted (suppressed) feature occurs when the chemical potential mu is less (greater) than but close to the threshold energy of a subband. Our results indicate that as mu increases, G exhibits, alternatively, the assisted and the suppressed feature. For a larger h omega, these two features may overlap. In addition, dip structures are found in the suppressed regime, and mini-steps are found in the assisted regime only when the gate-voltage covers a region sufficiently distant from the center of the constriction. (C) 1998 Elsevier Science B.V. All rights reserved.
Modular recurrent neural networks for Mandarin syllable recognition
(1998-11-01)
Chen, SH
;
Liao, YF
;
電信工程研究所
;
Institute of Communications Engineering
A new modular recurrent neural network (MRNN)-based speech-recognition method that can recognize the entire vocabulary of 1280 highly confusable Mandarin syllables is proposed in this paper, The basic idea is to first split the complicated task, in both feature and temporal domains, into several much simpler subtasks involving subsyllable and tone discrimination, and then to use two weighting RNN's to generate several dynamic weighting functions to integrate the subsolutions into a complete solution. The novelty of the proposed method lies mainly in the use of appropriate a priori linguistic knowledge of simple initial-final structures of Mandarin syllables in the architecture design of the MRNN, The resulting MRNN is therefore effective and efficient in discriminating among highly confusable Mandarin syllables. Thus both the time-alignment and scaling problems of the ANN-based approach for large-vocabulary speech-recognition can be addressed. Experimental results show that the proposed method and its extensions, the reverse-time MRNN (Rev-MRNN) and bidirection MRNN (Bi-MRNN), all outperform an advanced HMM method trained with the MCE/GPD algorithm in both recognition-rate and system complexity.
Direct focusing modifications of elliptical Gaussian beam by non-circular apertures
(1998-11-01)
Chan, SH
;
Shiue, SG
;
Lu, MH
;
光電工程研究所
;
Institute of EO Enginerring
For focusing the elliptical Gaussian beam directly, the effects of a non-circular aperture on the focusing properties are studied. The focusing properties for different shapes of apertures, which include a circle, an ellipse and a rectangle, are calculated and compared. Moreover, for different elliptical Gaussian beams, an empirical aperture selection rule that can be used to circularize the focusing spot is proposed. The energy transmission ratios are also considered in this paper.
Microstructure and nonlinear properties of microwave-sintered ZnO-V2O5 varistors: I, effect of V2O5 doping
(1998-11-01)
Kuo, CT
;
Chen, CS
;
Lin, IN
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The modification of the densification behavior and the grain-growth characteristics of the microwave-sintered ZnO materials, caused by the incorporation of V2O5 additives, have been systematically studied. Generally, the addition of V2O5 markedly enhances the densification rate, such that a density as high as 97.9% of the theoretical density and a grain size as large as 10 mu m can be attained for a sintering temperature as low as 800 degrees C and a soaking time as short as 10 min. Increasing the sintering temperature or soaking time does not significantly change the sintered density of the ZnO-V2O5 materials but it does monotonously increase their grain size. Varying the proportion of V2O5 in the range of 0.2-1.0 mol% does not pronouncedly modify such behavior. The leakage current density (J(L)) of these high-density and uniform-granular-structure samples is still large, which is amended by the incorporation of 0.3 mol% of Mn3O4 in the ZnO materials, in addition to 0.5 mol% of the V2O5 additives. Samples that are obtained using such a method possess good nonohmic characteristics (alpha = 23.5) and a low leakage current density (J(L) = 2.4 x 10(-6) A/cm(2)).
Properties of sputtered Cr-O and reactively sputtered Cr-N-O as passivation layers against copper oxidation
(1998-11-01)
Chuang, JC
;
Chen, MC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Passivation layers of 200 Angstrom sputtered Cr-O as well as reactive sputtered Cr-N-O were studied with respect to the passivation capability against thermal oxidation of Cu in flowing nitrogen and flowing oxygen ambients. In a flowing N-2 ambient, both Cr-O and Cr-N-O passivation layers were able to prohibit oxidation of Cu at temperatures up to 700 degrees C. In an O-2 ambient, the passivation capability of Cr-N-O layer was found to be 500 degrees C, which is 150 degrees C higher than that of Cr-O layer. The superiority of the passivation capability of the Cr-N-O layer is presumably due to decoration of the surface defects and grain boundaries with nitrogen, which provide fast paths for oxygen and copper diffusion. (C) 1998 American Vacuum Society. [S0734-211X(98)11706-7].
Microstructure and nonlinear properties of microwave-sintered ZnO-V2O5 varistors: II, effect of Mn3O4 doping
(1998-11-01)
Kuo, CT
;
Chen, CS
;
Lin, IN
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The microstructure and nonlinear current-voltage characteristics of Mn3O4-doped ZnO-V2O5 ceramics, microwave-sintered at 800 degrees-1200 degrees C for 10 min, have been investigated. A high density (96% of the theoretical density) has been achieved. The incorporation of Mn3O4 additives does not significantly alter the densification behavior of the ZnO-V2O5 materials, but rather pronouncedly increases the non-linear coefficient (alpha = 23.5) and markedly suppresses their leakage current density (J(L) = 2.4 x 10(-6) A/cm(2)). On the other hand, the intrinsic properties of the materials, including the Schottky barrier height (Phi(b)) and the donor density (N-d), are only moderately modified; that is, Phi(b) = 1.16 eV and N-d = 5.4 x 10(17)/cm(3). X-ray diffractometry analyses and energy-dispersive X-ray microanalyses (via scanning electron microscopy) indicate that the V2O5 species facilitate the densification and the development of microstructure via the formation of a liquid phase (Zn-3(VO4)(2)) along the grain boundaries, whereas the Mn3O4 species markedly enhance the nonohmic behavior of the ZnO-V2O5 materials by forming the surface states along the grain boundaries.