Browsing by Issue Date, starting with "2000-09-06"

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Curing kinetics and viscosity change of a two-part epoxy resin during mold filling in resin-transfer molding process
(2000-09-06)
Lee, CL
;
Wei, KH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The curing kinetics and the resulting viscosity change of a two-part epoxy/amine resin during the mold-filling process of resin-transfer molding (RTM) of composites was investigated. The curing kinetics of the epoxy/amine resin was analyzed in both the dynamic and the isothermal modes with differential scanning calorimetry (DSC). The dynamic viscosity of the resin at the same temperature as in the mold-filling process was measured. The curing kinetics of the resin was described by a modified Kamal kinetic model, accounting for the autocatalytic and the diffusion-control effect. An empirical model correlated the resin viscosity with temperature and the degree of cure was obtained. Predictions of the rate of reaction and the resulting viscosity change by the modified Kamal model and by the empirical model agreed well with the experimental data, respectively, over the temperature range 50-80 degrees C and up to the degree of cure alpha = 0.4, which are suitable for the mold-filling stage in the RTM process. (C) 2000 John Wiley & Sons, Inc.
Effect of material and process variables on the performance of resin-transfer-molded epoxy fabric composites
(2000-09-06)
Lee, CL
;
Wei, KH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The effects of material and process variables on glass fabric-reinforced epoxy composites by the resin-transfer molding (RTM) process were studied. It was found that the molded aged resin with 55% fiber exhibited twice the mold-filling time and caused a 7-15% deterioration in the interlaminar shear strength (ILSS) and in the flexural strength of the composites as compared to those of the composites molded with fresh resin. At a 55% fiber volume fraction, composites molded with aged resin resulted in a 35% longer filling time and a 4-12% decreased ILSS and flexural strength as compared to those of the composites at a 44% fiber volume fraction. Moldings with a perimeter inlet exhibited a 65% shorter mold-filling time, 28% reduced void content, and 6% improved flexural strength as compared to those of the composites molded with the center inlet. (C) 2000 John Wiley & Sons, Inc.
Total synthesis of (+/-)-2-isocyanoallopupukeanane
(2000-09-08)
Ho, TL
;
Kung, LR
;
Chein, RJ
;
應用化學系
;
Department of Applied Chemistry
2-Isocyanoallopupukeanane (4) has been obtained in racemic form from methyl 2-exo-methylbicyclo-[2.2.1]hept-5-ene-2-endo-carboxylate via dibromocarbene addition, S(N)2' displacement, chain extension, and elaboration of the unsaturated ketone 12c which underwent an intramolecular hetero-Diels-Alder reaction to afford 13 containing all the skeletal carbon atoms. The dihydropyran unit was cleaved by ozonolysis to give the tricarbocyclic intermediate which required seven more steps to complete the synthesis.
On asymptotic stabilization of driftless systems
(2000-09-11)
Liang, YW
;
Liaw, DC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A simple approach is proposed to investigate the stabilization of driftless systems. By taking the control input as a function of system states, we can transform the stabilization design into a stability problem. The known stability results on the nonlinear autonomous system are then employed to derive the asymptotically stabilizing controllers by solving an algebraic equation. Existence conditions of the asymptotic stabilizing feedback controller for the driftless systems by employing the stability criteria on linear systems and a class of third-order homogeneous systems are obtained to demonstrate the application of the approach. (C) 2000 Elsevier Science Inc. All rights reserved.
詩情與趣味-欣賞管管<小詩葉>三首
(2000-09-15)
管管
Field-emission properties of aligned carbon nanotubes
(2000-09-15)
Hong, WK
;
Shih, HC
;
Tsai, SH
;
Shu, CT
;
Tarntair, FG
Dense, well-separated, and aligned carbon nanotubes have been prepared via bias-enhanced microwave plasma chemical vapor deposition. The turn-on fields defined at the emission current density of 10 mu A/cm(2) are about 3.35 V/mu m, 2.54 V/mu m, and 3.54V/mu m, for the immersion times in PdCl2 of 1 min, 20 min, and 40 min,respectively. The corresponding emission current densities are about 0.97 mA/cm(2), 4.5 mA/cm(2), and 0.44 mA/cm(2) at the electric field of 5 V/mu m. The higher emission current obtained from the aligned carbon nanotubes for the immersion time of 20 min is ascribed to the denser and sharper nanotubes formed in this condition.
詩情與趣味-欣賞管管<小詩葉>三首
(2000-09-15)
管管
詩情與趣味-欣賞管管<小詩葉>三首
(2000-09-15)
管管
詩情與趣味-欣賞管管<小詩葉>三首
(2000-09-15)
管管
Two-dimensional electric-field vector measurement by a LiTaO3 electro-optic probe tip
(2000-09-20)
Kuo, WK
;
Chen, WH
;
Huang, YT
;
Huang, SL
;
電子工程學系及電子研究所
An electro-optic probe tip that is made from LiTaO crystal to make tangentially two-dimensional electric-field (E-field) vector measurements is presented. We combine a new electro-optic modulation technique and a conventional one to resolve the two E-tield components. The new modulation effect on the optical probing beam is caused by rotation of the principal axis the electro-optic crystal, which is proportional to the E-field. Inasmuch as there is no free charge involved in the axis rotation, rotation modulation of the axis can be as fast as conventional modulation. The principles are carefully derived, and an experimental system constructed, to measure two-dimensional E-field vectors on a test pattern. The results are in good agreement with those obtained with commercial software for electromagnetic simulation. The sensitivities of two tangential E-field components are 76 (mV/cm)/root Hz and 0.8 (V/cm)root Hz, respectively. The root-mean-square error of an E-field directional measurement is 1.5 degrees. (C) 2000 Optical Society of America OCIS codes: 120.5410, 230.2090, 230.4110, 130.6010.
Subharmonic Melnikov functions for strongly odd non-linear oscillators with large perturbations
(2000-09-21)
Ge, ZM
;
Ku, FN
;
機械工程學系
;
Department of Mechanical Engineering
Fast feedforward channel sounding RAKE receiver
(2000-09-28)
Chen, CC
;
Huang, CC
;
電信工程研究所
;
Institute of Communications Engineering
A RAKE receiver with a feedforward channel sounding technique is described. Chip rate sampling is used to reduce the hardware complexity. A novel path-selection technique is employed to track the rapidly changing channel impulse response. The bit error rate performance of this RAKE receiver nas evaluated by computer simulation.
An end-to-end flow control approach based on round trip time
(2000-09-30)
Chen, JR
;
Chen, YC
;
Lee, CL
;
資訊工程學系
;
Department of Computer Science
Traditional TCP Row control schemes, such as Tahoe and Reno, continuously increase the window size until possible packet loss is detected. These schemes generate congestion unnecessarily by themselves and utilize the buffer space inefficiently. Therefore, Vegas was proposed to accommodate the drawbacks. It uses the measured round-trip time (RTT) to obtain the information required for the flow control. in this work, we propose a Row control scheme, RTT-based TCP, which uses the RTT directly to control the window size adjustment. RTT-based TCP comprises four mechanisms: the modified exponential window increment, the RTT measurement, the queue occupancy estimation, and the quick queue-occupancy reduction. Simulation results show that RTT-based TCP outperforms Vegas in the aspects of throughput, fairness and efficiency of buffer usage. (C) 2000 Elsevier Science B.V. All rights reserved.
Migration-adsorption mechanism of metallic impurities out of chemically amplified photoresist onto silicon-based substrates
(2000-10-01)
Yang, CC
;
Ko, FH
;
Wang, MY
;
Wang, TK
;
Wu, SC
The radioactive tracer technique was applied to investigate the migration and adsorption behaviors of metallic impurities (i.e., Ba, Cs, Zn, and Mn) out of chemically amplified photoresist onto silicon-based underlying substrates. Two important process parameters, i.e., baking temperatures and substrate types (e.g., bare silicon, polysilicon, oxide, and nitride) were evaluated. Our results indicated that the transition metals (Zn and Mn) have lower migration ratios than alkali metal (Cs) and alkaline earth metal (Ba), irrespective of the substrate types and baking temperatures. The transition metals form stable complexes with the coexisting solvents and/or hydrolysis species in the photoresist layer. The size of the metal complex, the drag force in solvent evaporation, and the baking process were found to have significant effects on impurity migration. A new model, together with the metal migration in the chemically amplified photoresist and the subsequent adsorption onto the underlying substrate, was proposed to explain the pathway of the metal migration. This model could explain the migration ratios of metallic impurities out of the photoresist layer onto the substrate surface. (C) 2000 The Electrochemical Society. S0013-4651(00)01-026-0. All rights reserved.
Feedback median filter for robust preprocessing of glint noise
(2000-10-01)
Chang, DC
;
Wu, WR
;
電信工程研究所
;
Institute of Communications Engineering
Glint noise may arise in a target tracking system. The non-Gaussian behavior of glint noise can severely degrade the tracking performance, Measurement preprocessing at the front-end of the tracker is an effective method to reduce glint noise. The preprocessor proposed by Hewer, Martin, and Zeh, which used the computationally intensive M-estimator, may not be suitable for practical implementation. An alternative method employing the median filter is studied here. The median tilter is well known for its simplicity and robustness. However, the efficiency of the median biter can be seriously degraded if input samples are not identically distributed. This is what we may encounter in the tracking problem. A feedback median filter is then proposed to overcome this impediment without substantially increasing complexity. Simulations show that the new preprocessor can greatly improve tracking performance in the glint noise environment.
Temperature and annealing effects on photoluminescence spectra of (InAs)(1)/(GaP)(2) superlattices grown by solid-source molecular beam epitaxy
(2000-10-01)
Cheng, YC
;
Chi, S
;
Chou, ST
;
Huang, KF
;
電子物理學系
Anomalous variation of photoluminescence (PL) wavelengths with temperature was observed in (InAs)(1)/(GaP)(2) short-period-superlattice (SPS) quantum wells grown by solid-source molecular beam epitaxy with different phosphorus and arsenic cracker temperatures. We believed that the anomalous PL behavior could be attributed to the multi-axial strain effect existed at the abrupt InAs and GaP interfaces in the SPS structure. After rapid thermal anneal (RTA) treatment, the anomalous PL spectra in the low temperature region disappeared but the high temperature PL characteristics remained, which revealed the thermal stability of the (InAs)(1)/(GaP)(2) quantum well structures and its potential in replacing InGaAsP quaternary.
Parallel synchronous and asynchronous space-decomposition algorithms for large-scale minimization problems
(2000-10-01)
Liu, CS
;
Tseng, CH
;
機械工程學系
;
Department of Mechanical Engineering
Three parallel space-decomposition minimization (PSDM) algorithms, based on the parallel variable transformation (PVT) and the parallel gradient distribution (PGD) algorithms (O.L. Mangasarian, SIMA Journal on Control and Optimization, vol. 33, no. 6, pp. 1916-1925.), are presented for solving convex or nonconvex unconstrained minimization problems. The PSDM algorithms decompose the variable space into subspaces and distribute these decomposed subproblems among parallel processors. It is shown that if all decomposed subproblems are uncoupled of each other, they can be solved independently. Otherwise, the parallel algorithms presented in this paper can be used. Numerical experiments show that these parallel algorithms can save processor time, particularly for medium and large-scale problems. Up to six parallel processors are connected by Ethernet networks to solve four large-scale minimization problems. The results are compared with those obtained by using sequential algorithms run on a single processor. An application of the PSDM algorithms to the training of multilayer Adaptive Linear Neurons (Madaline) and a new parallel architecture for such parallel training are also presented.
Bayesian wavelet shrinkage for nonparametric mixed-effects models
(2000-10-01)
Huang, SY
;
Lu, HHS
;
統計學研究所
;
Institute of Statistics
The main purpose of this article is to study the wavelet shrinkage method from a Bayesian viewpoint. Nonparametric mixed-effects models are proposed and used for interpretation of the Bayesian structure. Bayes and empirical Bayes estimation are discussed. The latter is shown to have the Gauss-Markov type optimality (i.e., BLUP), to be equivalent to a method of regularization estimator (MORE), and to be minimax in a certain class. Characterization of prior and posterior regularity is discussed. The smoothness of posterior estimators is controlled via prior parameters. Computational issues including the use of generalized cross validation are discussed, and examples are presented.
Photo-induced liquid crystal alignment with discotic films
(2000-10-01)
Wu, LH
;
Lee, WC
;
Hsu, CS
;
Wu, ST
;
應用化學系
Photo-induced liquid crystal alignment using cross-linked discotic compounds was demonstrated. These discotic compounds exhibit good solubility in common organic solvents, 60 degreesC processing temperature and excellent thermal stability. A linearly polarized long wave ultraviolet light (lambda = 350 nm) was used to initiate the cross-linking process which, in turn, induces liquid crystal alignment on the discotic film surface. The polarity of discotic compounds plays an important role in affecting the pretilt angle of the liquid crystal alignment. A pretilt angle of 1 +/- 0.4 degrees was obtained using single exposure at oblique angle. Potential application of this new photo-alignment film for low temperature poly-silicon thin-film-transistor liquid crystal display is foreseeable.
Chinese dialect identification using segmental and prosodic features
(2000-10-01)
Chang, WW
;
Tsai, WH
;
電信工程研究所
;
Institute of Communications Engineering
Several approaches to Chinese dialect identification based on segmental and prosodic features of speech are described in this paper. When using segmental information only, the system performs phonotactic analysis after speech utterances have been tokenized into sequences of broad phonetic classes. The second scheme comprises prosodic models which are trained to capture tone sequence information for individual dialects. Also proposed is a novel approach that examines differences between Chinese dialects at broad phonetic and prosodic levels. These algorithms were evaluated via a multispeaker read-speech mode. Simulation results indicate that the combined use of Segmental and prosodic features allows the proposed system to discriminate among three major Chinese dialects spoken in Taiwan with 93.0% accuracy. (C) 2000 Acoustical Society of America. [S0001-4966(oo)03410-X].