Browsing by Issue Date, starting with "1994-04-30"

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SYNTHESIS AND THERMAL-BEHAVIOR OF SIDE-CHAIN LIQUID-CRYSTALLINE POLYMETHACRYLATES CONTAINING TOLANE-BASED MESOGENIC SIDE-GROUPS
(1994-04-30)
HSIEH, CJ
;
WU, SH
;
HSIUE, GH
;
HSU, CS
;
應用化學系
The synthesis and characterization of nine polymethacrylates containing 4-alkoxy-4'-tri-fluoromethyltolane, 4-alkoxy-4'-cyanotolane, and 4-alkoxy-4'-nitrotolane side groups were described in this study. The phase behavior of the prepared monomers and polymers was characterized by differential scanning calorimetry, optical polarizing microscopy, and x-ray diffraction. All of the obtained monomers exhibit no mesophase, while most of the synthesized polymers reveal enantiotropic mesomorphism. The polymethacrylate containing 4-propanyloxy-4'-nitrotolane side groups was the only one which shows no mesomorphic behavior. Both the spacer length and the nature of terminal groups have profound influence on the phase transition temperatures and thermal stability of the mesophase. The polymers with longer spacers tend to form a more ordered mesophase with a wider temperature range. Among three polymers with the same spacer length, the polymer with a trifluoromethyl terminal end group is inclined to form a more ordered mesophase than the other two polymers. No side chain crystallization occurred for all obtained polymers. (C) 1994 John Wiley & Sons, Inc.
THE EFFECTS OF FLUORINE PASSIVATION ON POLYSILICON THIN-FILM TRANSISTORS
(1994-05-01)
CHERN, HN
;
LEE, CL
;
LEI, TF
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The fluorine implantation on polysilicon was found to improve the characteristics of polysilicon thin-film transistors (TFT's). The fluorine passivates the trap states within the polysilicon channel. As compared with the H-2-plasma passivation, the fluorine implantation passivates more uniformly both the band tail-states and midgap deep-state, while the H-2-plasma treatment is more effective to passivate deep states than tail states. A fluorine-implanted device can be further improved its performance if an H-2-plasma treatment is applied. In contrast to the H-2-plasma passivation, the fluorine passivation improves the device hot-carrier immunity. Combining the fluorine passivation and H-2-plasma passivation, a high performance TFT with a high hot-carrier immunity can be obtained.
SUPPRESSION OF THE BORON PENETRATION INDUCED SI/SIO2 INTERFACE DEGRADATION BY USING A STACKED-AMORPHOUS-SILICON FILM AS THE GATE STRUCTURE FOR PMOSFET
(1994-05-01)
WU, SL
;
LEE, CL
;
LEI, TF
;
CHEN, JF
;
CHEN, LJ
This letter reports that the boron penetration through the thin gate oxide into the Si substrate does not only cause a large threshold voltage shift but also induces a large degradation in the Si/SiO2 interface. An atomically flat Si/SiO2 interface can be easily obtained by using a stacked-amorphous-silicon (SAS) film as the gate structure for p+ poly-Si gate MOS devices even the annealing temperature is as high as 1000-degrees-C.
BUOYANCY-INDUCED FLOW TRANSITION IN MIXED CONVECTIVE FLOW OF AIR THROUGH A BOTTOM HEATED HORIZONTAL RECTANGULAR DUCT
(1994-05-01)
HUANG, CC
;
LIN, TF
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
A detailed numerical simulation was carried out to study the buoyancy induced flow transition in a mixed convective flow of air through a bottom heated horizontal rectangular duct. The unsteady three-dimensional Navier-Stokes and energy equations were directly solved by a higher order finite difference numerical scheme without using any turbulence modeling. Results were particularly presented for Re = 500 and A = 2 covering a wide range of Gr/Re2 from steady laminar longitudinal vortex now to unsteady chaotic flow. The results indicate that the increasing buoyancy causes the steady laminar flow for Gr/Re2 < 4 to become a periodic laminar flow for 4 less-than-or-equal-to Gr/Re2 < 19, then to a quasiperiodic flow for 19 less-than-or-equal-to Gr/Re2 < 25 and finally to a chaotic flow in the downstream for 25 < Gr/Re2 less-than-or-equal-to 40. Thus, the buoyancy induced laminar to turbulent flow transition follows the Ruelle-Taken route. An empirical equation was proposed to correlate the locations for Hopf bifurcation.
A NEW METHOD FOR HANDLING MULTICRITERIA FUZZY DECISION-MAKING PROBLEMS
(1994-05-01)
CHEN, SM
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
;
Department of Computer Science
This paper presents a new method for handling multicriteria fuzzy decision-making problems, in which the characteristics of the alternatives are represented by interval-valued fuzzy sets, and some techniques are developed to calculate the degree of similarity between interval-valued fuzzy sets. The proposed method is more flexible than the one we presented earlier (Chen et al., 1989) because it allows the criteria values of the alternatives to be represented by real intervals rather than crisp real values between zero and one.
THE HYSTERESIS OF MAGNETIZATION IN THE GENERALIZED CRITICAL-STATE MODEL - LOW-FIELD APPROXIMATION
(1994-05-01)
CHEN, JL
;
YANG, TJ
;
電子物理學系
;
光電工程學系
;
Department of Electrophysics
The generalized critical-state model is extended to the low-field case by a new low-field approximation. We calculate the hysteresis loops of magnetization for H(max) < H* and H(max) > H*. We obtain new behaviors of M(H) which are different from the results derived from the Bean and Kim models. Our theory qualitatively agrees with the experimental results for high-T(c) superconductors. Some important macroscopic parameters may be obtained by fitting our theory with the experimental data.
ANALYTICAL DESIGN OF SYMMETRICAL KERR-LENS MODE-LOCKING LASER CAVITIES
(1994-05-01)
LIN, KH
;
HSIEH, WF
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
Analytical expressions for the spot size and the Kerr-lens mode-locking (KLM) strength can be represented as explicit functions of the Position in the cavity, the laser power, and the stability parameter for a four-mirror figure-Z laser resonator. The results indicate that the KLM strength achieves its maximum value at the edge of the stability range. Self-amplitude modulation and group-velocity dispersion compensation can be established by a prism pair. Simultaneously obtaining a large pumping efficiency and KLM is possible for this cavity.
IMPROVEMENT OF POLYSILICON OXIDE CHARACTERISTICS BY FLUORINE INCORPORATION
(1994-05-01)
CHERN, HN
;
LEE, CL
;
LEI, TF
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effect of fluorine on the polysilicon oxide (polyoxide) characteristics is investigated. It is found that the polyoxide leakage current and breakdown strength are improved as fluorine is incorporated into the oxide film. Experimental results show that the improvement is believed to be due to the oxide stress relaxation rather than the change of the polyoxide/polysilicon interface texture.
TRANSFER-FUNCTION BETWEEN WAVE HEIGHT AND WAVE PRESSURE FOR PROGRESSIVE WAVES
(1994-05-01)
KUO, YY
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CHIU, YF
;
交大名義發表
;
土木工程學系
;
National Chiao Tung University
Predicting the wave height from the subsurface wave pressure based on the pressure response factor and the correction factor has fundamental difficulties. The relationship between the measured wave height and the subsurface wave pressure was directly assessed in this study without resorting to the two parameters. Laboratory experiments were performed under various wave conditions. An empirical expression of the transfer function between wave height and wave pressure was obtained from these test data by dimensional analysis and regression analysis. In intermediate and deep water depth conditions, the transfer function was only a function of a nondimensional parameter which is composed of the angular frequency, the depth of the pressure sensor under the still water level and the acceleration of gravity. Finally, the empirical expression was compared with the experimental data and observational data from Hom-ma et al. (1966), Cavaleri (1978), Lee and Wang (1984), and Bishop and Donelan (1987). The empirical formula was found to be in sufficient correlation with these data.
THEORY OF DOUBLY RESONANT INFRARED-VISIBLE SUM-FREQUENCY AND DIFFERENCE-FREQUENCY-GENERATION FROM ADSORBED MOLECULES
(1994-05-01)
HUANG, JY
;
SHEN, YR
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光電工程研究所
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Institute of EO Enginerring
We theoretically analyze doubly resonant infrared-visible sum-frequency (DR IVSFG) and difference-frequency generation (DR IVDFG) from a monolayer of adsorbates at an interface. our calculated results with a model molecule indicate that the resonant amplitude of nonlinear optical susceptibility of DR IVDFG and DR IVSFG processes conveys information about the electron-vibration coupling in adsorbates. Moreover, owing to a dephasing-rephasing procedure involved, DR IVDFG can also be developed into a sensitive probe for investigating the coherent phase relaxation process in adsorbed molecules without the complication of inhomogeneous broadening.
FEATURE-PRESERVING CLUSTERING OF 2-D DATA FOR 2-CLASS PROBLEMS USING ANALYTICAL FORMULAS - AN AUTOMATIC AND FAST APPROACH
(1994-05-01)
LIN, JC
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TSAI, WH
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交大名義發表
;
資訊工程學系
;
National Chiao Tung University
We propose in this correspondence a new method to perform two-class clustering of 2-D data in a quick and, automatic way by preserving certain features of the input data. The method is analytical, deterministic, unsupervised, automatic, and noniterative. The computation time is of order n if the data size is n, and hence much faster than any other method which requires the computation of an n-by-n dissimilarity matrix. Furthermore, the proposed method does not have the trouble of guessing initial values. This new approach is thus more suitable for fast automatic hierarchical clustering or any other fields requiring fast automatic two-class clustering of 2-D data. The method can be extended to cluster data in higher dimensional space. A 3-D example is included.
STABILITY OF AN UMBILICAL DIRECTOR FIELD OF NEMATIC LIQUID-CRYSTAL IN A CLOSED CONICAL CAVITY
(1994-05-01)
WEI, JG
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CHEN, SH
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
This letter studies the stability of a single umbilical director field of nematic liquid crystal (NLC) in a closed cavity with external electric field. To form the single umbilic structure, we filled NLC with negative dielectric anisotropy in a closed conical cavity and made molecules align perpendicular to the cavity wall. Electric field was applied along the symmetry axis of the cavity. Using the continuum theory, we show that an umbilical director field will transform to a director field of a hyperbolic singular point with disclination ring instead of a Poincare structure at a critical voltage.
A NOTE ON THE MINIMUM CUT COVER OF GRAPHS
(1994-05-01)
HO, TY
;
HSU, LH
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交大名義發表
;
資訊工程學系
;
National Chiao Tung University
Loulou formulates the problem of minimizing the test time for printed circuit boards into that of minimizing the cardinality of cut cover for graphs. This note shows that the minimum cardinality of cut cover for a graph G is inverted left perpendicular log2 chi(G) inverted right perpendicular. This result enables us to conclude that the problem of determining the minimum cardinality of cut cover is NP-hard. It is also known that every planar graph is 4-colorable. Thus, if the layouts of printed circuit board form a planar graph, the minimum time needed to test the circuits is at most 2.
NEW OBSERVATION AND THE MODELING OF GATE AND DRAIN CURRENTS IN OFF-STATE P-MOSFETS
(1994-05-01)
CHEN, MJ
;
CHAO, KC
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CHEN, CH
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The work reports new observations concerning the gate and drain currents measured at off-state conditions in buried-type p-channel LDD MOSFET devices. Detailed investigation of the observed phenomena reveals that 1) the drain current can be separated into two distinct components: band-to-band tunneling in the gate-to-drain overlap region and collection of holes generated via impact ionization by electrons inside the oxide; and 2) the gate current can be separated into two distinct components: the hot electron injection into the oxide and the Fowler-Nordheim electron tunneling through the oxide. At low negative drain voltage, the dominant component of the drain current is the hole generation inside the oxide. At high negative drain voltage, the drain current is essentially due to band-to-band tunneling, and it is correlated with the hot-electron injection-induced gate current.
SYNTHESIS OF SIDE-CHAIN LIQUID-CRYSTALLINE POLYOXETANES CONTAINING 4-DODECANYLOXYPHENYL TRANS-4-ALKYLCYCLOHEXANOATE SIDE-GROUPS
(1994-05-01)
LU, YH
;
CHANG, HL
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HSU, CS
;
應用化學系
;
Department of Applied Chemistry
The synthesis and characterization of side-chain liquid crystalline polyoxetanes containing 4-dodecanyloxyphenyl trans-4-alkylcyclohexanoate side groups are presented. All the obtained monomers exhibit smectic B mesomorphism, while all the obtained polymers present smectic A, smectic B and smectic G mesophases. A longer terminal alkyl group is leading to the formation of a more stable mesophase.
EFFECT OF INTERFACIAL OXIDE ON STATIC AND HIGH-FREQUENCY PERFORMANCE IN POLYEMITTER BIPOLAR-TRANSISTORS UNDER HIGH-LEVEL INJECTION
(1994-05-01)
CHYAN, YF
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SZE, SM
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CHANG, CY
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REIF, R
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電控工程研究所
We report on a theoretical investigation of the eff ect of interfacial oxide on both static and dynamic performance in polycrystalline silicon emitter bipolar transistors. The calculation is carried out up to 0.9 V, before the onset of the Kirk eff ect. From the model, it is found that the current gain increases and the forward transit time decreases as interfacial oxide thickness increases. Furthermore, both the current gain and the forward transit time decrease as recombination velocity increases. In addition, the intrinsic base resistance remains almost constant as interfacial oxide thickness increases, and increases as recombination velocity increases. Compared with the conventional low-level injection model, the improved model provides much more accurate expressions for electrical characteristics of bipolar transistors operating under high-level injection.
OBJECT MOVEMENT IN DISTRIBUTED OBJECT-ORIENTED SYSTEMS
(1994-05-01)
LEE, YS
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WANG, FJ
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CHANG, CH
;
交大名義發表
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資訊科學與工程研究所
In a distributed object-oriented system-a system containing more than one object-oriented system (OOS)-different OOSs may contain classes with different definitions, different definitions but the same name, or the same definition but different names. Moving an object between two OOSs includes locating a suitable class and creating an instance of the class with the value of the moved object in the destination system. This study discusses what is a suitable class for a moved object in the destination OOS and presents the algorithms for finding such a suitable class. It also discusses the activities of copying the value of the moved object into the instance of a located class in the destination site. A general object movement mechanism and its implementation for a domain specific model are then incorporated into a prototype of a distributed OOS, called DOOSPE.
SO2 REMOVAL BY NH3 GAS INJECTION - EFFECTS OF TEMPERATURE AND MOISTURE-CONTENT
(1994-05-01)
BAI, H
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BISWAS, P
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KEENER, TC
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環境工程研究所
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Institute of Environmental Engineering
The removal of SO2 by NH3 gas injection at various temperatures and moisture contents has been studied experimentally. The product compositions of the NH3-SO2-H2O vapor reactions were also reported. A thermodynamic analysis was carried out to predict the SO2 removal as well as the product compositions. Both the experimental results and thermodynamic analysis indicated that SO2 removal and the product compositions are sensitive to the reaction temperature. Moisture content, once in large excess of the stoichiometric requirement, does not have a strong effect on the product compositions but plays an important role in the SO2 removal.
OPTIMUM BEAMFORMERS FOR MONOPULSE ANGLE ESTIMATION USING OVERLAPPING SUBARRAYS
(1994-05-01)
LEE, TS
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DAI, TY
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交大名義發表
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電信工程研究所
;
National Chiao Tung University
We here derive the optimum sum and difference beamformers for monopulse target localization using a linear array. The beamformers are constructed, treating as superelements two overlapping subarrays. Removing the common factor associated with the superelement pattern from the angle error function leads to a closed-form target angle estimator independent of any adaptive nulling performed. Performance analysis of the angle estimator is conducted, and a procedure is developed to construct the beamformers, which achieve the minimum estimation variance under Gaussian noise. It is shown that the optimum angle estimator using the maximum overlapping subarrays is efficient for a moderately high signal-noise ratio (SNR) and a small off-boresight angle. The proposed method can be easily modified to incorporate interference cancellation.
MAGNETIC-ORDERING OF PR AND CU IN TLBA2PRCU2O7-Y
(1994-05-01)
HSIEH, WT
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CHANG, KJ
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LI, WH
;
LEE, KC
;
LYNN, JW
Neutron-scattering measurements have been performed to study the magnetic ordering of Pr and Cu in semiconducting TlBa2PrCu2O7-y. This compound has a nuclear structure which is similar to that of YBa2Cu3O7 but with the CuO-chain layers fully replaced by TlO layers. At low temperatures the magnetic diffraction pattern reveals magnetic Bragg peaks of the {1/2 1/2 1/2} type, which are associated with the antiferromagnetic ordering of the Pr moments. The magnetic structure consists of nearest-neighbor spins along all three crystallographic directions being antiparallel. The spin direction is along the c axis, with a saturated moment of 1.05 mu(B). The temperature dependence of the intensity of these reflections indicates a Neel temperature T(N) almost-equal-to 8 K, which is about half that observed in the related PrBa2Cu3O7 system. A second set of magnetic reflections, of the {1/2 1/2 1} type, are also observed, and these are associated with the Cu magnetic sublattice. This magnetic structure is identical to the ''plane ordering'' observed in the related 1:2:3 system, where the nearest-neighbor Cu spins are again antiparallel. The spin direction is in the tetragonal ab plane, with a saturated ordered moment of 0.59 mu(B). The temperature dependence indicates a Neel temperature of almost-equal-to 370 K for the Cu spins.