Browsing by Issue Date, starting with "1995-06-01"

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RUBBING-INDUCED MOLECULAR ALIGNMENT ON AN ORIENTING LAYER OF POLYIMIDE WITH AND WITHOUT ALKYL SIDE-CHAINS
(1995-06-01)
HUANG, JY
;
LI, JS
;
JUANG, YS
;
CHEN, SH
;
交大名義發表
The rubbing-induced molecular alignment on a surface of polyimide with and without branched alkyl side chains was investigated with optical phase retardation measurement, atomic force microscopy (AFM), and second-harmonic generation (SHG). Our AFM results suggest that the rubbing-induced microgrooves play a minor role in aligning liquid crystal (LC) molecules. From the SHG studies, the detailed in-plane distribution of a LC monolayer on rubbed polymers was deduced, and the polar angle of the LC molecules was found to vary with the rubbing strength exerted on an alkyl-branched polymer. The polar angle of the LC monolayer on an alkyl-branchless main-chain polyimide film was observed to be independent of the rubbing strength. We propose a simple molecular model to reconcile these experimental results.
ANALYSIS OF TRANSPORT CRITICAL-CURRENT DENSITY IN A BENT BI-PB-SR-CA-CU-O SILVER-SHEATHED TAPE
(1995-06-01)
LEE, WD
;
HORNG, L
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YANG, TJ
;
CHIOU, BS
;
電子物理學系
The experimental results on the magnetic behavior of the transport critical current density in a bent Bi based superconducting tape have shown that the irreversible strain limit epsilon(irrev) for the onset of permanent strain damage to Ag sheathed superconductors is not dependent on the magnetic field, nor does the normalized I-c(H, epsilon)/I-c(0, epsilon) current depend on the strain at least up to 0.5 T at 77 K. Such a behavior has been attributed to two reasons: (1) The intrinsic pinning properties are unchanged in a bent tape; (2) The strain effect is extrinsic and arises from superconductor cracks. Thus, based on these arguments a Josephson junction tunneling model with cracks in between the grain boundaries is proposed to explain the J(c) behavior quite well for a bent granular high-T-c superconducting tape. Our model calculation shows that the critical current density of high-T-c superconductor may be enhanced by increasing the strain tolerance epsilon(irrev) and the epsilon(irrev) is determined by the properties of Ag sheathed tape and its related material parameters, which are dependent on the connectivity of the grain boundaries.
THE MAXIMUM BIT RATES OF SOLITON COMMUNICATION-SYSTEMS WITH LUMPED AMPLIFIERS AND FILTERS IN DIFFERENT DISTANCES
(1995-06-01)
CHI, S
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DUNG, JC
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WEN, SF
;
光電工程學系
;
電信研究中心
The maximum bit rate of a soliton communication system with lumped amplifiers and optical filters is considered, When the dispersion of the fiber varies from one amplifier spacing to another amplifier spacing, the maximum bit rate is significantly reduced. To overcome the effect, the amplitude of the soliton is amplified so that it is still the average soliton corresponding to the fiber dispersion for an amplifier spacing, Thus, the maximum bit rate is only slightly less than that without the dispersion variations, For a given distance, the maximum bit rate limited by the stability and soliton interaction is obtained, The result is compared with that limited by the Gordon-Haus effect, For shorter transmission distance, the maximum bit rate is limited by the stability and soliton interaction, For longer transmission distance, the maximum bit rate is limited by the Gordon-Haus effect.
DECOUPLING CONTROLLER-DESIGN FOR LINEAR-MULTIVARIABLE SYSTEMS WITH PERIODIC INPUTS
(1995-06-01)
HO, SJ
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LIN, CA
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電控工程研究所
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Institute of Electrical and Control Engineering
We propose a decoupling controller design method for linear multivariable systems with periodic inputs. The plant may be nonminimum phase, and the periodic inputs may have different periods in different input channels. In addition to achieving closed-loop stability and input-output decoupling, the design is to satisfy prespecified sensitivity bound and tracking error bound for a class of periodic inputs in each channel. With the proposed design approach, an n-channel MIMO design problem is reduced to n SISO ones in which design specifications can be independently achieved. A design algorithm is proposed, and an illustrative example is given.
TUNABLE MULTITERAHERTZ BEAT SIGNAL GENERATION FROM A 2-WAVELENGTH LASER-DIODE ARRAY
(1995-06-01)
WANG, CL
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PAN, CL
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交大名義發表
;
光電工程學系
;
National Chiao Tung University
We report, for the first time to our knowledge, generation of a tunable miltiterahertz modulation signal on an optical carrier directly from a single laser source. The modulation frequency, which can be tuned from 0.15 THz to more than 7 THz, is the beat note obtained by varying the spectral separation between the coaxial two-color output of a two-wavelength laser-diode array from 0.32 to 17 nm. The frequency characteristics of the terahertz beat note are determined with a noncollinear intensity autocorrelator.
REACTION-KINETICS OF HUMIC-ACID WITH SODIUM-HYPOCHLORITE - COMMENT
(1995-06-01)
CHANG, CN
;
CHAO, AC
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LIN, JG
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環境工程研究所
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Institute of Environmental Engineering
A NEW APPROACH TO MODELING THE SUBSTRATE CURRENT OF PRESTRESSED AND POST-STRESSED MOSFETS
(1995-06-01)
YANG, JJ
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SHAOSHIUN, S
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CHOU, PC
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CHEN, CH
;
LIN, MS
In this paper, we propose a closed form expression of a new and accurate analytical substrate current model for both pre-stressed and post-stressed MOSFET's, It was derived based on the concept of effective electric field, which gives a more reasonable impact ionization rate in the lucky-electron model, This effective electric field, composed by two experimentally determined parameters, ran be regarded as a result of nonlocal heating effects within de,ices, This model shows a significant improvement to the conventional local field model. One salient feature of the present model is that it allows us to characterize the time evolution of the substrate current of stressed MOSFET's for the first time. Experimental verification for a wide variety of MOSFET's with effective channel lengths down to 0.3 mu m shows that the new model is very accurate and is feasible for any kind of MOS device with different drain structures, The present model can be applied to explore the hot carrier effect in designing submicrometer MOS devices with emphasis on the design optimization of a device drain engineering issue, In addition, the present model is well suited for device reliability analysis and circuit level simulations.
ELECTRON-ATOM SCATTERING IN AN INTENSE RADIATION-FIELD
(1995-06-01)
HAN, CS
;
電子物理學系
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Department of Electrophysics
FUZZY CONTROL OF RIDER-MOTORCYCLE SYSTEM USING GENETIC ALGORITHM AND AUTOTUNING
(1995-06-01)
WU, JC
;
LIU, TS
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機械工程學系
;
Department of Mechanical Engineering
This study investigates the stability control of a rider-motorcycle system based on fuzzy control in conjunction with both genetic algorithm (GA) and an auto-tuning method. The autotuning method, which entails tuning rules, is employed to on-line adjust output gains of fuzzy control. Although a GA has been used for fuzzy control in the literature, it has been confined to aiding membership functions' enaction. By contrast, this study employs a GA to determine optimal parameters in control rules for fuzzy control and in tuning rules for the auto-tuning method. Both computer simulation and experiment with regard to an inverted pendulum hinged to a rotating disk are carried out to represent the circular motion of the rider-motorcycle system, in which the inverted pendulum represents a rider's body in banking motion. The relation between riding speeds of the motorcycle and leaning angles of the rider is examined based on speed variations and Bode plots. Simulation and experimental results show the significant effect of the rider's banking angle on stability control.
PERFORMANCE CHARACTERIZATION OF THE TREE QUORUM ALGORITHM
(1995-06-01)
CHANG, HK
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YUAN, SM
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交大名義發表
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資訊工程學系
;
National Chiao Tung University
The tree quorum algorithm, which logically organizes the sites in a system to a tree structure, is an efficient and fault-tolerant solution for distributed mutual exclusion. In this paper, the performance characteristics of the tree quorum algorithm is analyzed. A refinement algorithm is proposed to refine a logical tree structure by eliminating nodes or subtrees which do not improve the peformance. Thus the refined tree performs better than the original.
MODELING THE POSITIVE-FEEDBACK REGENERATIVE PROCESS OF CMOS LATCHUP BY A POSITIVE TRANSIENT POLE METHOD .1. THEORETICAL DERIVATION
(1995-06-01)
KER, MD
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WU, CY
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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
A novel method to characterize the mechanism of positive-feedback regeneration in a p-n-p-n structure during CMOS latchup transition is developed, It is based on the derived time-varying transient poles in large-signal base-emitter voltages of the lumped equivalent circuit of a p-n-p-n structure, Through calculating the time-varying transient poles during CMOS latchup transition, it is found that there exists a transient pole to change from negative to positive and then this pole changes to negative again, A p-n-p-n structure, which has a stronger positive-Feedback regeneration during turn-on transition, will lead to a larger positive transient pole, The time when the positive transient pole occurs during CMOS latchup transition is the time when the positive-feedback regeneration starts, By this positive transient pole, the positive-feedback regenerative process of CMOS latchup can he quantitatively characterized.
CMOS CURRENT-MODE IMPLEMENTATION OF SPATIOTEMPORAL PROBABILISTIC NEURAL NETWORKS FOR SPEECH RECOGNITION
(1995-06-01)
WU, CY
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LIU, RY
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JOU, IC
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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
In this paper, a Spatiotemporal Probabilistic Neural Network (SPNN) is proposed for spatiotemporal pattern recognition. This new model is developed by applying the concept of Gaussian density function to the network structure of the SPR (SPatiotemporal Pattern Recognition). The main advantages of this model include faster training and recalling process for patterns. In addition, the overall architecture is also simple, modular, regular, locally connected, and suitable for VLSI implementation. One set of independent speaker isolated (Mandarin digit) speech database is used as an example to demonstrate the superiority of the neural networks for spatiotemporal pattern recognition. The testing result with a reduced error rate of 7% shows that the SPNN is very attractive and effective for practical applications. The CMOS current-mode IC technology is used to implement the SPNN to achieve the objective of minimum classification error ina more direct manner. In this design, neural computation is performed in analog circuits while template information is stored in digital circuits. The prototyping speech recognition processor for the 12th LPC calculation is designed by 1.2 mu m CMOS technology. The HSPICE simulation results are also presented, which verifies the function of the designed neural system.
GRAPHICAL DETERMINATION OF MONOMER SHIFT, DIMER SHIFT AND DIMERIZATION CONSTANT FOR SELF-ASSOCIATION - 2-ISOPROPYL PHENOL IN C6D12 AS AN EXAMPLE
(1995-06-01)
CHEN, JS
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SHIAU, JC
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FANG, CY
;
交大名義發表
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應用化學系
We propose a graphical method to treat dilution shift in NMR spectra to determine the monomer shift, dimer shift and dimerization constant simultaneously and consistently for the system of monomer/dimer equilibrium. The salient features include avoiding error-prone manual extrapolation to zero concentration to obtain a monomer shift, and providing consistent assessment and error estimation for the determination. The dilution shifts of 2-isopropyl phenol in C6D12 serve to demonstrate this graphical method. The enthalpy and entropy of dimerization are determined via a van't Hoff plot from the temperature variation of the dimerization constant.
KNOWLEDGE ACQUISITION FOR FUZZY EXPERT-SYSTEMS
(1995-06-01)
HWANG, GJ
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交大名義發表
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資訊工程學系
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National Chiao Tung University
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Department of Computer Science
Expert systems have been successfully applied to a wide variety of application domains. To achieve better performance, researchers have tried to employ fuzzy logic to the development of expert systems. However, as fuzzy rules and membership functions are difficult to define, most of the existing tools and environments for expert systems do not support fuzzy representation and reasoning. Thus, it is time-consuming to develop fuzzy expert systems. In this article we propose a new approach to elicit expertise and to generate knowledge bases for fuzzy expert systems. A knowledge acquisition system based upon the approach is also presented, which can help knowledge engineers to create, adjust, debug, and execute fuzzy expert systems. Some control techniques are employed in the knowledge acquisition system so that the concepts of fuzzy logic could be directly applied to conventional expert system shells; moreover, a graphic user interface is provided to facilitate the adjustment of membership functions and the display of outputs. The knowledge acquisition system has been integrated with a popular expert system shell, CLIPS, to offer a complete development environment for knowledge engineers. With the help of this environment, the development of fuzzy expert systems becomes much more convenient and efficient. (C) 1995 John Wiley & Sons, Inc.
3-DIMENSIONAL NATURAL-CONVECTION OF AIR IN AN INCLINED CUBIC CAVITY
(1995-06-01)
LEE, TL
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LIN, TF
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機械工程學系
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Department of Mechanical Engineering
Three-dimensional steady and transient natural convective flow in a differentially heated inclined cubic cavity of air was numerically simulated by the projection method combined with the power law scheme. Various three-dimensional flow structures were induced, depending on the Reyleigh number and inclined angle, although the main flow is nearly two-dimensional. It is of interest to note that the flow is stronger when a vertical cavity is inclined, implying significant flow acceleration by the buoyancy component normal to the hot and cold walls. Change in the flow structure during the transient causes wavy variation of the space-averaged Nusselt number with time.
MICROWAVE-ENHANCED SUPERCONDUCTIVITY AND TRANSPORT-PROPERTIES OF Y-BA-CU-O BICRYSTAL WEAK-LINKS
(1995-06-01)
FU, CM
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JUANG, JY
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CHEN, MF
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WU, KH
;
UEN, TM
The effects of the tilt angle on microwave-enhanced transition temperatures and critical currents of YBCO bicrystal weak-links have been investigated. It was found that, with smaller grain boundary tilt angles (e.g. 24 degrees), the enhancement was small, displaying essentially the same behavior as that manifested in intragranular regions. By contrast, when the tilt angle was increased from 36.8 degrees to 45 degrees, noticeable Tc enhancement was found to occur even at low input microwave powers. The results were compared to the temperature dependent critical current, in order to delineate possible correlations between the two physical parameters.
FABRICATION AND PROPERTIES OF DC-SPUTTERED TL-1223 SUPERCONDUCTING THIN-FILMS
(1995-06-01)
JUANG, JY
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HORNG, JH
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LIN, HC
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WANG, SJ
;
FU, CM
A multi-step deposition and post annealing scheme has been developed for preparing nearly single phase, c-axis oriented TlBa2Ca2Cu3O9 (Tl-1223) superconducting thin films by dc-sputtering. The effects of the compensates used during post annealing on final phase formation suggest the crucial role played by thermodynamic conditions and further validates the viability of the present process scheme. In particular, films obtained by the present process have shown, for the first time in this system, a critical current density (Jc) above 10(6) A/cm(2) at 17 K with a zero- resistance transition temperature (Tco) above 110 K. The results are attributed to the improvement of film morphology, specifically a decreased density of weak-linking.
ENHANCED H-2-PLASMA EFFECTS ON POLYSILICON THIN-FILM TRANSISTORS WITH THIN ONO GATE-DIELECTRICS
(1995-06-01)
YANG, CK
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LEE, CL
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LEI, TF
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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
This letter reports that passivation effects of the H-2-plasma on the polysilicon thin-film transistors (TFT's) were greatly enhanced if the TFT's have a thin Si3N4 film On their gate-dielectrics. Compared to the conventional devices with only the SiO2 gate dielectric, the TFT's with Si3N4 have much more improvement on their subthreshold swing and field-effect mobility after H-2-plasma treatment.
CRUCIAL FORMULA FOR DETERMINATION OF THE OCCURRENCE OF THE NONCHAOTIC STATES IN RF-BIASED NONLINEAR OSCILLATORS
(1995-06-01)
YANG, TH
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WANG, CS
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HUANG, JC
;
GOU, YS
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電子物理學系
ERROR INDUCED BY LOCAL YIELDING AROUND HOLE IN HOLE DRILLING METHOD FOR MEASURING RESIDUAL-STRESS OF MATERIALS
(1995-06-01)
LIN, YC
;
CHOU, CP
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機械工程學系
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Department of Mechanical Engineering
The hole drilling strain gauge method described in ASTM standard E837 is a popular method for measuring residual stresses near the surface of a material. However, some measuring errors have been found that may affect the accuracy of the measurement The present paper aims to improve the accuracy by analysing the errors caused by local yielding around the hole. The materials used were 304 stainless steel, 5052 H32 aluminium alloy, and 1018 low carbon steel. The experimental results showed that the error induced by local yielding around the hole is negligible when the residual stresses measured are less than 65% of the yield stress. The maximum errors are in the range 32-47% and occur when the calibrated tensile stress is 95% of the yield stress of the test material. The maximum plastic error occurs in the perfect elastic-plastic material. The plastic error increases as the value of the Young's modulus of the material used increases.