Browsing by Issue Date, starting with "1994-03-31"

Now showing 1 - 20 of 88362

COMPLEX-VALUED NEURAL-NETWORK FOR DIRECTION-OF-ARRIVAL ESTIMATION
(1994-03-31)
YANG, WH
;
CHAN, KK
;
CHANG, PR
;
交大名義發表
;
電信工程研究所
A complex-valued neural network for the implementation of a direction of arrival (DoA) estimator is presented. The network is based on the linear prediction method, with data processed fully in the complex domain. Simulation results are given to demonstrate the effectiveness of the network performances.
QUANTIZATION-ERROR CURVE - A MEASURE OF SIMILARITY BETWEEN REQUANTISED IMAGES
(1994-03-31)
CHU, CH
;
HSUEH, YC
;
資訊工程學系
;
Department of Computer Science
A new similarity measure between a digital image and its quantised version is presented. By calculating the quantisation error on each of a sequence of subdomains, we can obtain a quantisation error curve as a similarity measure. This measure outperforms the commonly used measure for estimating the similarity between requantised images.
BINDING-ENERGIES OF D- ION IN GAAS QUANTUM-WELL
(1994-04-01)
CHANG, YH
;
YEH, JJ
;
SHEU, YM
;
WANG, CC
;
CHEN, TC
Magnetic field dependent binding energies of the D- ion in the center of a 210 angstrom GaAs quantum well are determined by temperature magneto-transport measurments. The binding energies increase from 2.1 meV at 2T to 4 meV at 8T, and are consistently higher than the transition energies ootained from magneto-optical measurements performed on the same sample. We conclude from these data that in the magneto-optical measurement the observed transitions are between ground and excited D- states.
NANOMETER THICK SI/SIGE STRAINED-LAYER SUPERLATTICES GROWN BY AN ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION TECHNIQUE
(1994-04-01)
CHANG, TC
;
CHANG, CY
;
JUNG, TG
;
TSAI, WC
;
WANG, PJ
High quality Si/Si1-xGex superlattices having layers as thin as 1.5 nm have been grown by an ultrahigh vacuum/chemical vapor deposition system. High-resolution double-crystal x-ray diffraction, and conventional and high-resolution cross-sectional transmission electron microscopy were used to evaluate the crystalline quality of these superlattices. A dynamical x-ray simulation program was employed to analyze the experimental rocking curves. Excellent matches between experimental rocking curves and simulated ones were obtained for all superlattices with various periodicity. A cross-sectional transmission electron micrograph of an 80 period Si(4.2 nm)/Si0.878Ge0.122 (1.5 nm) superlattice, in which each individual layers was clearly resolved, demonstrated the capability of this growth technique for nanometer thick layer deposition.
CHARACTERIZATION OF SI/SIGE STRAINED-LAYER SUPERLATTICES GROWN BY AN ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION TECHNIQUE
(1994-04-01)
CHANG, TC
;
CHANG, CY
;
JUNG, TG
;
TSAI, WC
;
HUANG, GW
High-resolution double-crystal X-ray diffraction and cross-sectional transmission electron microscopy were used to characterize the Si/SiGe strained-layer superlattices grown by the ultrahigh vacuum/chemical vapor deposition (UHV/CVD) system. A dynamical X-ray simulation was employed to analyze the experimental rocking curves. Good matches between the experimental rocking curves and the simulated ones demonstrate that the high quality Si/SiGe strained-layer superlattices with abrupt interface and excellent thickness and composition uniformity have been achieved. Thickness uniformity was further confirmed by the cross-sectional transmission electron microscopy. In addition, high-resolution double-crystal X-ray diffraction was proven to be a powerful technique for determining the doping level and the thickness of heavily doped contact layer in Si/SiGe device structures prior to further processing. Good wafer-to-wafer uniformity can be simultaneously achieved by the UHV/CVD technique; as a result, the UHV/CVD technique is readily applicable to manufacturing.
ANALYSIS OF A CUTOFF PRIORITY CELLULAR RADIO SYSTEM WITH FINITE QUEUING AND RENEGING/DROPPING
(1994-04-01)
CHANG, CJ
;
SU, TT
;
CHIANG, YY
;
電信工程研究所
;
電信研究中心
Queueing of new or handoff calls can minimize blocking probabilities or increase total carried traffic. This paper investigates a new cutoff priority cellular radio system that allows Smite queueing of both new and handoff calls. We consider the reneging from the system of queued new calls due to caller impatience and the dropping of queued handoff calls by the system as they move out of a handoff area before being accomplished successfully. We use signal-flow graphs and Mason's formula to obtain the blocking probabilities of new and handoff calls and the average waiting times. Moreover, an optimal cutoff parameter and appropriate queue sizes for new and handoff calls are numerically determined so that a proposed overall blocking probability is minimized.
LOW-TEMPERATURE-PROCESSED POLY-SI THIN-FILM TRANSISTORS USING SOLID-PHASE-CRYSTALLIZED AND LIQUID-PHASE-DEPOSITED GATE OXIDE
(1994-04-01)
YEH, CF
;
CHEN, CL
;
YANG, YC
;
LIN, SS
;
YANG, TZ
Poly-Si thin-film transistor (TFT) devices using solid-phase-crystallized and liquid-phase-deposited gate oxide are, for the first time, realized by low-temperature processes (LTP) (<625-degrees-C) for future LCDs and 3-D integrated circuits. The method of liquid-phase deposition of SiO2 (LPD-SiO2) is described. The physical, chemical and electrical properties of the new dielectric layer are clarified. The TFT (W/L = 200 mum/10 mum) having an on-off current ratio of 10(6) at V(D) = 5 V, a field-effect mobility of 15 cm2/V.s at V(D) = 0.1 V, a threshold voltage of 5.6 V, and a subthreshold swing of 1.6 V/decade, exhibits sufficient performance for pixel transistors. The field-effect mobility is strongly dependent on channel length. Effective passivation of defects by plasma hydrogenation will be very essential to achieve higher performance.
MULTICOMPONENT ION-EXCHANGE COLUMN DYNAMICS
(1994-04-01)
TAN, HKS
;
SPINNER, IH
;
應用化學系
;
Department of Applied Chemistry
Simple model equations which consider different rate control mechanisms are formulated for fixed bed multicomponent ion exchange processes. Efficient and accurate numerical methods are developed for solving these equations for liquid phase, solid phase or combined phase control. The algorithms are applicable to both ion exchange and liquid adsorption and are shown to be extendable to a general form of isotherms. The accuracy of the numerical algorithm is evidenced by the fact that the asymptotic limiting equilibrium solutions are closely approached as the dimensionless length parameter is increased, regardless of the rate control mechanism. Numerical examples for ion exchange applications are presented. These examples included multicomponent elution and purification problems. The effect of mass transfer resistance was also examined. Other examples examine the validity of a model reduction assumption and the comparison of equilibrium theory with the results obtained using the present finite mass transfer rate model.
BORON-DOPED DIAMOND FILMS USING TRIMETHYLBORATE AS A DOPANT SOURCE IN METHANE CARBON-DIOXIDE GAS-MIXTURES
(1994-04-01)
CHEN, CF
;
CHEN, SH
;
HONG, TM
;
WANG, TC
;
材料科學與工程學系
The effects of boron concentration in the gas phase on the morphological features and cathodoluminescence (CL) of polycrystalline diamond films were investigated. The diamond films were prepared on p-type Si(100) substrates by microwave plasma chemical vapour deposition. Trimethylborate vapour was introduced to the CH4-CO2 gas mixture as a dopant source. Secondary ion mass spectroscopy (SIMS), Raman and CL spectroscopy and scanning electron microscopy analysis were performed on the films. The depth profile of SIMS showed that boron was uniformly doped into the diamond film even at a depth of 6 mum. Boron was found to have a significant effect on both the morphology and cathodoluminescence of the deposited films. The surface morphology changed from well-defined facets to ball-like features with increasing gas phase dopant concentration. To obtain doped diamond films of good quality, it is necessary to lower the carbon concentration by decreasing the flow rate of CH4 during the deposition process. The cathodoluminescence of diamond films was investigated in the range 1.8-4.0 eV. The emission peak intensity of CL spectra at 2.3-2.4 eV was found to increase with increasing dopant concentration in the gas phase. The luminescence is explained by donor-acceptor pair recombination, where the acceptor is substitutional boron. This result indicates that the boron atoms can be successfully doped into substitutional sites of the diamond structure.
ENHANCEMENT OF OXIDE BREAK-UP BY IMPLANTATION OF FLUORINE IN POLY-SI EMITTER CONTACTED P-+-N SHALLOW JUNCTION FORMATION
(1994-04-01)
WU, SL
;
LEE, CL
;
LEI, TF
;
CHEN, CF
;
CHEN, LJ
In this study, it is demonstrated that the incorporation of fluorine can enhance poly-Si/Si interfacial oxide break-up in the poly-Si emitter contacted p+-n shallow junction formation. The annealing temperature for breaking up the poly-Si/Si interfacial oxide has been found to be as low as 900-degrees-C. As a result, the junction depth of the BF2-implanted device is much larger than that of the boron-implanted device.
OPTIMAL MULTIPROCESSOR TASK-SCHEDULING USING DOMINANCE AND EQUIVALENCE-RELATIONS
(1994-04-01)
CHOU, HC
;
CHUNG, CP
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
We propose an optimization scheme for unit-execution-time task scheduling on multiprocessors. In this scheme, dominance, semi-dominance, equivalence and semi-equivalence relations between tasks are first defined. The solution tree technique is adopted to keep track of the unfinished sub-schedules. We prove that when certain conditions are satisfied, a sub-schedule need not be explored further, since it cannot lead to a schedule better than some others. An algorithm that avoids generating such non-optimal schedules is presented. Then we conduct experiments to show the promise of our scheme in reducing solution space. Another advantage of this scheme is its extensibility. This scheme can easily be applied to other scheduling problems by simply adding additional constraints to the original definitions of the dominance, semi-dominance, equivalence and semi-equivalence relations.
IMPROVED QUANTITATIVE MEASURES OF ROBUSTNESS FOR MULTIVARIABLE SYSTEMS
(1994-04-01)
CHEN, HG
;
HAN, KW
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Asymptotically stable linear systems subject to unstructured time varying perturbations are considered. Allowable perturbation bounds are obtained such that the perturbed systems remain stable. These bounds are derived iteratively by means of adjusting a sequence of Lyapunov matrices. In comparison with existing methods, less conservative quantitative measures of robustness are obtained.
COLLOCATED SENSOR ACTUATOR POSITIONING AND FEEDBACK DESIGN IN THE CONTROL OF FLEXIBLE STRUCTURE-SYSTEM
(1994-04-01)
LEE, AC
;
CHEN, ST
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
This paper presents a new control design method for the control of flexible systems that not only guarantees closed-loop asymptotic stability but also effectively suppresses vibration. This method allows integrated determination of actuator/sensor locations and feedback gain via minimization of an energy criterion, which is chosen as the integrated total energy stored in the system. The energy criterion is determined via an efficient solution of the Lyapunov equation and minimized with a quasi-Newton or recursive quadratic programming algorithm. The prerequisite for this optimal design method is that the controlled system be asymptotically stable. This study shows that when the controller structure is a collocated direct velocity feedback design with positive definite feedback gain, the number and placement of actuators/sensors are the only factors needed to determine necessary and sufficient conditions for ensuring closed-loop asymptotic stability. The application of this method to a simple flexible structure confirms the direct relationship between our optimization criterion and effectiveness in vibration suppression.
CRACK SIZE IDENTIFICATION USING AN EXPANDED MODE METHOD
(1994-04-01)
KAM, TY
;
LEE, TY
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
An expanded mode method constructed based on the modal analysis method and an energy approach is presented for size identification of a crack with given location in a damaged structure. Measured natural frequencies and mode shapes of the structure with or without a crack are used to compute the strain energies of the structures subject to free vibration via a quasi-static approach. The two types of strain energy are then combined with the work required for the crack formation to construct the energy balance equation from which the size of the crack is evaluated through an iteration procedure. The theory of fracture mechanics is used to derive the work required for crack formation. Examples of the identification of crack sizes for a number of damaged beam structures are given to illustrate the applications of the proposed expanded mode method. Factors affecting the accuracy of crack size identification are investigated using a cracked cantilever beam as an example. The results show that the present method is promising for practical applications.
ELECTROOPTIC PHASE TRACKING OF MICROWAVE SIGNALS BEYOND 18.5 GHZ USING AN INTEGRATED ELECTROOPTIC MODULATOR AS AN OPTOELECTRONIC HARMONIC MIXER IN A PHASE-LOCK LOOP
(1994-04-01)
PAN, CL
;
LIN, GR
;
CHYOU, DY
;
WU, HH
;
交大名義發表
We demonstrate electrooptic phase tracking of microwave signals beyond 18.5 GHz using a gain-switched laser diode as the optical clock. The key element of this system is a fiber-pigtailed integrated-optic Mach-Zehnder Modulator (IOM). The IOM functions as an optoelectronic harmonic mixer in a phase lock loop. The conversion loss of the OEHM is 66dB. The phase error and the single sideband phase noise density of the phase- locked 18.5 GHz signal is 5.6 x 10(-5) rad/square-root Hzand -54 dBc/Hz, respectively.
EFFECT OF GE CONCENTRATION ON STATIC AND MICROWAVE PERFORMANCES IN GEXSI1-X HETEROJUNCTION BIPOLAR-TRANSISTORS UNDER HIGH-LEVEL INJECTION
(1994-04-01)
CHYAN, YF
;
SZE, SM
;
CHANG, CY
;
REIF, R
;
電控工程研究所
We report the theoretical investigation of the effect of Ge concentration on both static and high-frequency performances in polycrystalline silicon emitter GexSi1-x heterojunction bipolar transistors (HBTs). The calculation is carried out up to 0.95 V, before the onset of the Kirk effect [C. T. Kirk: IEEE Trans. Electron Devices ED-9 (1962) 164]. From this model, we find that the current gain, transconductance, cutoff frequency, and maximum oscillation frequency increase with increasing Ge concentration. In addition, the base transit time and the switching delay time in the emitter-coupled logic circuit slightly decrease as Ge content increases. Furthermore, it shows that the high-level injection eff ect becomes more pronounced in the GexSi1-x HBT as Ge concentration increases. Compared with the conventional low-level injection model, the improved model provides much more accurate expressions for electrical characteristics of GexSi1-x HBTs operating under high-level injection.
PD-GE CONTACT TO N-GAAS WITH THE TIW DIFFUSION BARRIER
(1994-04-01)
HUANG, WC
;
LEI, TF
;
LEE, CL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Pd-Ge based ohmic contact to n-GaAs with a TiW diffusion barrier was investigated. Electrical analysis as well as Auger electron spectroscopy and the scanning electron microscopy were used to study the contact after it was subjected to different furnace and rapid thermal annealing and different aging steps. All analyses show that TiW can act as a good barrier metal for the Au/Ge/Pd/n=GaAs contact system. A value of 1.45 x 10(-6) OMEGA-cm2 for the specific contact resistance was obtained for the Au/TiW/Ge/Pd/n-GaAs contact after it was rapid thermally annealed at 425-degrees-C for 90 s. It can withstand a thermal aging at 350-degrees-C for 40 h with its pc increasing to 2.94 x 10(-6) OMEGA-CM2 and for an aging at 410-degrees-C for 40 h with its p. increasing to 1.38 x 10(-5) OMEGA-cm2.
THEORETICAL EVALUATION OF THE INHIBITORY EFFECTS OF MERCURY ON ALGAL GROWTH AT VARIOUS ORTHOPHOSPHATE LEVELS
(1994-04-01)
CHEN, CY
;
交大名義發表
;
環境工程研究所
;
National Chiao Tung University
;
Institute of Environmental Engineering
Mercury toxicity on Selenastrum capricornutum was examined by a chemostat culture system. Phosphorus concentration within the system was controlled by means of maintaining different dilution rates of the chemostat. The study shows that EC(50) is consistently correlated with the phosphorus concentration. The sample correlation coefficient (r) between EC(50) and PO4-P concentration is found to be 0.87, which suggests that EC(50) is likely to be influenced by the phosphorus concentration. This phenomenon can be explained by a theory which describes the correlation between the tolerance and the activation level. The study indicates that nutrient conditions constitute an important factor in algal toxicity tests.
TAUTOMERIC RELAXATION RATES IN THE GROUND-STATE OF TETRA-4-TERTIARY BUTYLPHTHALOCYANINE IN SHPOLSKII MATRICES
(1994-04-01)
CHEN, WH
;
GAO, J
;
RIECKHOFF, KE
;
VOIGT, EM
;
電子物理學系
We report experimental results of the ground state proton tunneling rate constant k in the absence of radiation to be from 0.03 to 0.35 s-1 at temperatures from 4.2 to 77 K for tetra-4-tertiary butylphthalocyanine tautomers embedded in hexadecane matrices. While a detailed microscopic description of the exact transfer mechanism is not possible from the data obtained so far, we present a model based on a new type of potential barrier and use the semiclassical WKB approximation to calculate transmission data compatible with experiment.
MEASUREMENT OF THIN OXIDE-FILMS ON IMPLANTED SI-SUBSTRATE BY ELLIPSOMETRY
(1994-04-01)
CHAO, TS
;
LEI, TF
;
CHANG, CY
;
LEE, CL
;
電子工程學系及電子研究所
In this study, the thickness of oxide film which is deposited by low-temperature chemical vapor deposition (LTCVD) on an implanted silicon substrate was measured by multiple-angle incident (MAI) ellipsometry. By using this method, the refractive index, thickness, and the effective index of the substrate can be calculated simultaneously. It is found that the thickness of oxide film on an implanted silicon substrate is only 4% different from that on a nonimplanted silicon substrate under the same deposition conditions. The result shows that a higher implantation energy results in a higher effective substrate index. Even with a high temperature and long annealing process, the refractive index of the implanted silicon substrate cannot recover to the value of nonimplanted silicon substrate.