Browsing by Issue Date, starting with "1992-01-16"

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EFFECT OF FINITE SUBSTRATE WIDTH ON HIGHER-ORDER MODE GENERATION OF ELECTRICALLY SHIELDED SYMMETRICAL MICROSTRIP
(1992-01-16)
TSENG, JD
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TZUANG, CKC
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交大名義發表
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電信研究中心
;
National Chiao Tung University
The effect of finite substrate width on the higher-order mode generation of an electrically shielded microstrip is investigated. By employing the full-wave mixed potential mode-matching method the microstrip on a finite-width substrate can be accurately analysed. The dispersion characteristics of microstrip on two different substrate widths were compared in the frequency range of interest. The results indicated that the use of conventional three-dimensional simulators assuming homogeneous layered (stratified) multi-dielectric substrates may not work well above the first cutoff frequency of microstrip on a finite-width substrate.
FRACTURE AND IMPACT PROPERTIES OF POLYCARBONATES AND MBS ELASTOMER-MODIFIED POLYCARBONATES
(1992-01-25)
CHANG, FC
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WU, JS
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CHU, LH
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交大名義發表
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應用化學系
Mechanical properties of polycarbonates (PCs) and elastomer-modified polycarbonates with various molecular weights (MW) are investigated. Higher MW PCs show slightly lower density, yield stress, and modulus. The ductile-brittle transition temperature (DBTT) of the notched impact strength decreases with the increase of PC MW and with the increase of elastomer content. The elastomer-modified PC has higher impact strength than does the unmodified counterpart if the failure is in the brittle mode, but has lower impact strength if the failure is in the ductile mode. The critical strain energy release rate (G(c)) measured at -30-degrees-C decreases with the decrease of PC MW. The extrapolated zero fracture energy was found at M(n) = 6800 or MFR = 135. The G(c) of the elastomer-modified PC (MFR = 15, 5% elastomer) is about twice that of the unmodified one. The presence of elastomer in the PC matrix promotes the plane-strain localized shear yielding to greater extents and thus increases the impact strength and G(c) in a typically brittle fracture. Two separate modes, localized and mass shear yielding, work simultaneously in the elastomer-toughening mechanism. The plane-strain localized shear yielding dominates the toughening mechanism at lower temperatures and brittle failure, while the plane-stress mass shear yielding dominates at higher temperatures and ductile failure. For the elastomer-modified PC (10% elastomer), the estimated extension ratio of the yielding zone of the fractured surface is 2 for the ductile failure and 5 for the brittle crack. A criterion for shifting from brittle to ductile failure based on precrack critical plastic-zone volume is proposed.
陰濕的蒼苔
(1992-01-28)
管管
某人的人生觀之可嘆
(1992-01-29)
管管
FORMATION OF SELF-ALIGNED COBALT SILICIDE IN NORMAL FLOW NITROGEN FURNACE
(1992-01-30)
YANG, FM
;
CHEN, MC
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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
Cobalt can be completely transformed into cobalt silicide during annealing in a normal flow nitrogen furnace above a certain temperature which depends on the thickness of the cobalt film deposited on the silicon substrate. For a 400 angstrom cobalt film this temperature is 500-degrees-C and for a 1500 angstrom cobalt film it is 650-degrees-C. Loading the wafer into furnace tube is a critical step to prevent the cobalt from oxidation before silicidation in the annealing process. Lateral growth of silicide is not observed using this silicidation scheme. The cobalt oxide together with the underlying cobalt over the silicon oxide can be removed by hot 3HCl + H2O2 + 3H2O solution if the annealing is performed at a temperature below 650 and 900-degrees-C for a cobalt film thickness of 400 and 1500 angstrom respectively. The optimum condition for practical silicide formation is defined. The products and microstructure over the silicon and silicon oxide are characterized by X-ray diffraction spectra, Auger electron spectroscopy depth profiles, sheet resistance measurements and scanning electron microscopy inspection.
REDUCTION OF RESIDUAL-STRESS BY PARALLEL HEAT WELDING IN SMALL SPECIMENS OF TYPE-304 STAINLESS-STEEL
(1992-02-01)
CHOU, CP
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LIN, YC
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交大名義發表
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機械工程學系
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National Chiao Tung University
A new method designated 'parallel heat welding' has been developed for the reduction of residual stress in small specimens. It is carried out using a pair of parallel heating torches attached one either side to a welding torch as a movable heat source during welding. Six different welding conditions were applied to an autogenous gas tungsten arc welded Type 304 stainless steel. During welding, the thermal cycles of four locations in the weldment were recorded to investigate the action of thermal stress and to evaluate the effect of the parallel heat sources on sensitisation. In addition, an optical microscope was used to observe the degree of sensitisation. The experimental results show that the maximum principal residual stress and parallel welding direction stress can be reduced by 21-32% when the conventional welding process is replaced by parallel heat welding. The equilibrium temperature of the welded plate can be increased from 45 to 240-degrees-C. Also, based on the exposure time recorded at temperatures in the range 600-850-degrees-C, and metallographical observations, it was found that parallel heat welding has no influence on the degree of sensitisation of austenitic stainless steel weldments.
MATHEMATICAL MORPHOLOGY ON L-IMAGES
(1992-02-01)
HSUEH, YC
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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
In most applications, morphological operations are considered as unary operations, each associated with a structuring element. Due to the problem of grey-level overflow, the associated structuring elements of morphological operations on grey-level images (functions from R(n) or Z(n) to [0, m], where m is a fixed positive number) are limited to 'flat' or 'non-flat' structuring elements. However, neither flat or non-flat structuring elements are grey-level images. In this paper, we propose the notion of l-images, based on a clc-monoid (complete lattice-ordered commutative monoid), as a unified representation of binary images (functions from R(n) or Z(n) to {0, 1}), signals (functions from R(n) or Z(n) to the set of extended real numbers R*) and grey-level images. Then we generalize morphological operations to l-images such that the associated structuring elements can be arbitrary l-images. As consequences, we obtain several concrete expressions for dilations and erosions on grey-level images such that the associated structuring elements are also grey-level images. Therefore, the grey-level overflow problem is solved with no limitations on structuring elements. Furthermore, we show that the duality property of dilations and erosions on l-images holds if the underlying clc-monoid is self-dual.
DISTRIBUTED ERBIUM-DOPED FIBER AMPLIFIERS WITH STIMULATED RAMAN-SCATTERING
(1992-02-01)
WEN, S
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CHI, S
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光電工程學系
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電信研究中心
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Department of Photonics
The effect of stimulated Raman scattering (SRS) on the distributed erbium-doped fiber amplifier with 1.48-mu-m pump wavelength and 1.55-mu-m signal wavelength is numerically studied. The contributions of the gains from SRS and the pumped erbium ions doped in the fiber core are shown. It is found that SRS enhances both the gain and signal-to-noise ratio of the amplifier except the signal-to-noise ratio may be decreased by SRS for high initial signal power.
A NEW ACCESS-CONTROL METHOD USING PRIME FACTORIZATION
(1992-02-01)
HWANG, JJ
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SHAO, BM
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WANG, PC
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管理科學系
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資訊管理與財務金融系註：原資管所+財金所
Based on prime factorisation in number theory, a new but simple and efficient protection method for access control is proposed. This method has several advantages on performance over previous methods in the literature. Especially, a file/user can be added to or removed from the system without much effort. Excellence of this method is more pronounced for those systems where files are accessible to only a few users.
INVESTIGATION OF THERMAL COEFFICIENT FOR POLYCRYSTALLINE SILICON THERMAL SENSOR DIODE
(1992-02-01)
YEH, CF
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LIN, SS
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YANG, GP
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交大名義發表
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電控工程研究所
Thermal sensors utilizing p-n junction diodes built into the polycrystalline silicon layer are developed. The effective factors influencing the thermal coefficient of polycrystalline silicon thermal sensor diodes are clarified. It is found that diodes with a light boron dose have a larger thermal coefficient than those with a heavy boron dose. The plural p-n diodes connected with more cascade series number have a larger thermal coefficient than ones with less cascade series number. The periphery of the thermal sensor seems to have little effect on the thermal coefficient. In addition, the thermal coefficient will become higher as a larger forward current is selected. The thermal coefficient of the sensor with a boron dose of 1 x 10(15) cm-2 will reach a saturation value of -2 mV/K when the forward current is above 2-mu-A.
ANALYSIS OF DISPERSION AND SERIES GAP DISCONTINUITY IN SHIELDED SUSPENDED STRIPLINES WITH SUBSTRATE MOUNTING GROOVES
(1992-02-01)
WU, LK
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CHANG, HM
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交大名義發表
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傳播研究所
;
National Chiao Tung University
Dispersion and series gap discontinuity of shielded suspended striplines (SSL's) on Duroid substrate (epsilon(r) = 2.22) are analyzed using the finite-difference time-domain method (FD-TD). Numerical accuracy of better than 0.15% is achieved when the FD-TD is used to calculate the effective dielectric constant (epsilon(reff)) of an air-filled rectangular coaxial transmission line. Data obtained for the frequency-dependent epsilon(reff) of uniform SSL's, and both scattering and equivalent circuit parameters of various series gap discontinuities, are then presented. In general, presence of sidewall mounting grooves causes a nearly frequency-independent small reduction in epsilon(reff). On the other hand, proximity effects of the housing are found to be more important. It is demonstrated that: 1) for a given housing, epsilon(reff) decreases first with an increase in strip width before increasing again when strip is wider enough to interact strongly with the sidewalls and 2) reducing sidewall spacing causes an increase in epsilon(reff). For the gap discontinuity, coupling across the gap is stronger for wider strips and/or narrower gap width. Irregular transmission behavior is also found when strip is wide enough to interact strongly with the sidewalls.
BIT-SLICED MEDIAN FILTER DESIGN BASED ON MAJORITY GATE
(1992-02-01)
LEE, CL
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JEN, CW
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交大名義發表
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電控工程研究所
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National Chiao Tung University
There are arithmetic problems for the hardware realisation of bit-level median filtering algorithms. A design of a majority gate which is composed of output-wired inverters is proposed. The area and time complexities are better than the digital and analogue designs now available. This circuit is applied to a median filter design which is based on majority selection, the computation problems are thus avoided. It is a bit-sliced architecture with constant cycle time. Window shapes can be arbitrarily changed through mask-and-set modules. A median filtering system for two-dimensional image processing is presented. A binary majority gate is also an essential element in decision-making circuitry which is applied in fault-tolerant computing systems, artificial neural networks or related applications.
NUMERICAL-ANALYSIS OF THE LOOPING EFFECT IN GAAS-MESFETS
(1992-02-01)
LO, SH
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LEE, CP
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電子工程學系及電子研究所
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奈米中心
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Department of Electronics Engineering and Institute of Electronics
The looping effect in the I(D)-V(D) characteristics of GaAs MESFET's on semi-insulating substrates has been studied using a two-dimensional numerical analysis. Both the transient and the steady-state behaviors of the looping phenomenon are simulated and discussed. Peak voltage- and frequency-dependent behaviors of the looping effect are analyzed. The I(D)-V(D) loop is due to the difference in the distribution of ionized EL2 concentration when the drain voltage rises and falls because of the trapping process of EL2's. The output conductance is also found to be frequency-dependent and is explained by the frequency-dependent modulation of the potential barrier height at the channel/substrate interface due to the drain-voltage variation.
A NOVEL TECHNIQUE FOR LOW-THRESHOLD AND HIGH-POWER INGAAS/GAAS STRAINED-LAYER 0.98-MU-M BURIED HETEROSTRUCTURE LASER FABRICATION
(1992-02-01)
LIOU, DC
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CHIANG, WH
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LEE, CP
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CHANG, KH
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LIU, DG
A novel fabrication technique has been developed for InGaAs/GaAs strained-layer buried heterostructure lasers. Dielectric masks and Zn diffusion are not required in this technique. This novel fabrication process is much easier than the conventional approach and yields excellent laser results. A low threshold of 3 mA and high-power operation for lasing wavelength of 9800 +/- 20 angstrom have been achieved with graded index separate confinement heterostructure devices using this novel technique.
A NEW VARIABLE FRACTIONAL SAMPLE DELAY FILTER WITH NONLINEAR INTERPOLATION
(1992-02-01)
LIU, GS
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WEI, CH
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交大名義發表
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電控工程研究所
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National Chiao Tung University
This paper presents a finite impulse response (FIR) filter that can synthesize any fractional sample delay by nonlinear interpolation technique. Analytically closed-form solutions for the tap weights of such an FIR filter and their frequency responses are presented.
THE NEUTRON STREAMING TERM IN A GENERALIZED COORDINATE SYSTEM
(1992-02-01)
WAY, YS
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WAY, YM
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電子物理學系
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Department of Electrophysics
The vectorial form of the neutron streaming term used in the Boltzmann equation has been derived. With the aid of this vectorial form, the explicit expression of the neutron streaming term in a generalized coordinate system can readily be obtained. Examples of applications in the orthogonal curvilinear and the elliptical-elliptical toroidal coordinate systems are given for illustration.
RELAXATION BY THE HOPFIELD NEURAL NETWORK
(1992-02-01)
YU, SS
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TSAI, WH
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資訊工程學系
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Department of Computer Science
The relaxation process is a useful technique for using contextual information to reduce local ambiguity and achieve global consistency in various applications. It is basically a parallel execution model, adjusting the confidence measures of involved entities based on interrelated hypotheses and confidence measures. On the other hand, the neural network is a computational model with massively parallel execution capability. The output of each neuron depends mainly on the information provided by other neurons. Therefore, there exist certain common properties in the relaxation process and the neural network technique. A mapping method that makes the Hopfield neural network perform the relaxation process is proposed. By this method, the neural network technology can be easily adapted to solve the many problems which have already been solved by the relaxation process. An advantage of this is that the relaxation process can be performed in real time since the Hopfield network can be implemented by conventional analog circuits. Experimental results are given to demonstrate the feasibility of the proposed method by performing the image thresholding operation on the proposed neural network.
A SIMULATED ANNEALING APPROACH TO THE NETWORK DESIGN PROBLEM WITH VARIATIONAL INEQUALITY CONSTRAINTS
(1992-02-01)
FRIESZ, TL
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CHO, HJ
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MEHTA, NJ
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TOBIN, RL
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ANANDALINGAM, G
The equilibrium network design problem can be formulated as a mathematical program with variational inequality constraints. We know this problem is nonconvex; hence, it is difficult to solve for a globally optimal solution. In this paper we propose a simulated annealing algorithm for the equilibrium network design problem. We demonstrate the ability of this algorithm to determine a globally optimal solution for two different networks. One of these describes an actual city in the midwestern United States.
EFFECTS OF RAPID THERMAL ANNEALING ON THE FORMATION OF SHALLOW P+N JUNCTION BY IMPLANTING BF2+ IONS INTO THIN METAL-FILMS ON SI SUBSTRATE .1. THIN TITANIUM FILMS
(1992-02-01)
JUANG, MH
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CHENG, HC
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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
High-quality Ti-silicided shallow p+ n junctions have been fabricated by implanting BF2+ ions into thin Ti films on Si substrate and subsequent silicidation/drive-in by rapid thermal annealing (RTA) or conventional furnace annealing (CFA) under proper implant and anneal conditions. For both the RTA and CFA techniques, annealing temperatures higher than 800-degrees-C degrade the junction formation because of more severe dopant confinement within the silicides and more serious diffusion of knock-on Ti into junction regions. The high-dose implant greatly enhanced the dopant activation and thus improved the junctions. The high heating rate for RTA caused an immediate formation of Ti-B compounds at high temperatures, while CFA considerably promoted the drive-in efficiency because of its low heating rates and long annealing times. Hence, CFA yielded better low-bias rectifying characteristics than RTA due to larger dopant activation. However, CFA caused much worse high reverse-bias characteristics. A rapid increase of reverse currents with bias voltage was observed for the CFA-treated samples, indicating a severe Ti penetration due to long annealing times.
INSTABILITIES IN COUPLED PHOTOREFRACTIVE RING CAVITIES AND SELF-PUMPED PHASE CONJUGATORS
(1992-02-01)
DAI, LK
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GOU, YS
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GU, C
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YEH, P
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光電工程學系
In the preceding paper, we used the mean-field approximation to formulate the time evolution equations for two coupled unidirectional photorefractive ring resonators. Linear stability analysis based upon the steady-state solutions of the mean-field equations showed that the coupled system may become unstable in the unstable off- and steady-state operation regimes. In this paper, we investigate the temporal behavior and nonlinear dynamics of the coupled system. The results indicate that the coupled system exhibits self-pulsation and chaos in the unstable off-state and steady-state operation regimes. The instability is explained in terms of the competition between the nonlinear gain and loss. Numerical results of the transient equations are presented and discussed. The coupling between unidirectional ring resonators is extended to explain the instability in self-pumped phase conjugators.