Browsing by Issue Date, starting with "1996-06-01"

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A new extraction algorithm for the metallurgical channel length of conventional and LDD MOSFET's
(1996-06-01)
Jean, YS
;
Wu, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A new extraction algorithm for the metallurgical channel length of conventional and LDD MOSFET's is presented, which is based on the well-known resistance method with performing a special technique to eliminate the uncertainty of the channel length as well as to reduce the influence of the parasitic source/drain resistance on threshold-voltage determination. In particular, the metallurgical channel length is determined from a wide range of gate-voltage-dependent effective channel length at an adequate gate overdrive, The 2-D numerical analysis clearly show that the adequate gate overdrive is strongly dependent on the dopant concentration in the source/drain region, Therefore, an analytic equation is derived to determine the adequate gale overdrive for various source/drain and channel doping, It shows that higher and lower gate overdrives are needed to accurately determine the metallurgical channel length of conventional and LDD MOSFET devices, respectively. It is the first time that we can give a Correct gate overdrive to extract L(met) not only for conventional devices but also for LDD MOS devices. Besides, the parasitic source/drain resistance call also he extracted using our new extraction algorithm.
Back-gate forward bias method for low-voltage CMOS digital circuits
(1996-06-01)
Chen, MJ
;
Ho, JS
;
Huang, TH
;
Yang, CH
;
Jou, YN
The back-gate forward bias method suitable for present standard hulk CMOS processes has been promoted for low-voltage digital circuit application, A CMOS inverter employing the method has experimentally exhibited the ability of electrically adjusting the transition region of the de voltage transfer characteristics. Transient measurement has further shown that the inverter with a back-gate forward bias of 0.4 V can operate at low supply voltages down to 0.6 V without significant loss in switching speed, Guidelines for ensuring proper implementation of tile method in a bulk CMOS process has been set up against latch-up, parasitic bipolar, impact ionization, and stand-by current, Following these guidelines, a cost-effective low-power, low-voltage, high-density mixed-mode CMOS analog/digital integrated circuits chip with both reasonable speed and improved precision has been projected for the first time.
Two-color above-threshold ionization of atoms
(1996-06-01)
Han, CS
;
電子物理學系
;
Department of Electrophysics
A nonperturbative method is used to study the two-color multiphoton ionization of atoms by solving the Schrodinger equation in momentum space, which facilitates the extraction of the rapidly varying part of the wave function. Our method generalizes the problem for cases where an arbitrary number of ionization photons are absorbed, and also takes into account the threshold shifts due to both the high- and low-frequency fields. The photoelectron energy spectra of the hydrogen atoms are calculated and the dependence on the laser field strengths and frequencies is discussed.
A speech recognition method based on the sequential multi-layer perceptrons
(1996-06-01)
Chen, WY
;
Chen, SH
;
Lin, CJ
;
交大名義發表
;
National Chiao Tung University
A novel multi-layer perceptrons (MLP)-based speech recognition method is proposed in this study. In this method, the dynamic time warping capability of hidden Markov models (HMM) is directly combined with the discriminant based learning of MLP for the sake of employing a sequence of MLPs (SMLP) as a word recognizer. Each MLP is regarded as a state recognizer to distinguish an acoustic event. Next, the word recognizer is formed by serially cascading all state recognizers. Advantages of both HMM and MLP methods are attained in this system through training the SMLP with an algorithm which combines a dynamic programming (DP) procedure with a generalized probabilistic descent (GPD) algorithm. Additionally, two sub-syllable SMLP-based schemes are studied through application of this method toward the recognition of isolated Mandarin digits. Simulation results confirm that the performance of the methods is comparable to a well modeled continuous Gaussian mixture density HMM trained with the minimum error criterion. Not only does the SMLP require less trainable parameters than the HMM system, but the former is more convenient for analysing internal features. With the aid of internal feature selection, discarding the least useful parameters of SMLP without affecting its performance is relatively easy. Copyright (C) 1996 Elsevier Science Ltd
Coupling-efficiency analysis and control of dual antiresonant reflecting optical waveguides
(1996-06-01)
Chen, YH
;
Huang, YT
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We have developed the necessary theory to analyze the coupling efficiency of dual ARROW waveguide. Based on the theory, we have found that the coupling efficiency of dual ARROW waveguides can be flexibly controlled from a 100% value to zero by simply varying the outermost cladding thickness. BPM simulations also give same results and verify the theory. The theory and simulation results can be efficiently applied to designing an ARROW power divider with any specified power ratio.
Stereoselectivity of the Diels-Alder reaction of (E)gamma-Oxo-alpha,beta-unsaturated thioesters with cyclopentadiene
(1996-06-01)
Tsai, SH
;
Chung, WS
;
Wu, HJ
;
應用化學系
;
Department of Applied Chemistry
The stereoselectivity of the Diels-Alder reaction of (E)-gamma-oxo-alpha,beta-unsaturated thioesters 3a-3d with cyclopentadiene is greatly enhanced in the presence of Lewis acids favoring the endo acyl isomers 4a-4d. In the absence of Lewis acid, Diels-Alder reaction of 3a-3d with cyclopentadiene at 25 degrees C gave two adducts 4a-4d and 5a-5d in a ratio of 1:1 respectively. In the presence of Lewis acids, Diels-Alder reaction of 3a-3d with cyclopentadiene gave 4a-4d and 5a-5d in ratios of 75 similar to 94:25 similar to 6 respectively. The stereoelectivity was enhanced to ratios of 95 similar to 98:5 similar to 2 with lowering the reaction temperature. The stereochemistry of the cycloadducts 4 and 5 was confirmed by iodocyclization. Reaction of the endo-thioester 5c with I-2 in aqueous THF at 0 degrees C gave the novel methylthio group rearranged product 6c in 80% yield, the first example of iodolactonization of endo-thioesters. Reaction of the endo-acyl isomer 4b with I-2 under the same reaction conditions gave an isomeric mixture of 7b and 8b in 1:2 ratio. The stereochemistry of the thioester group in 8b was proved by X-ray single-crystal analysis. The solvent effect on the endo selectivity of (Z)-gamma-oxo-alpha,beta-unsaturated thioester 2b was also examined.
PA CS: Personal access communications system - A tutorial
(1996-06-01)
Noerperl, AR
;
Lin, YB
;
Sherry, H
;
資訊工程學系
;
Department of Computer Science
The Personal Access Communications System (PACS) is an American National Standards Institute common air interface standard developed for the 1.9 GHz PCS band in the United Stales. PACS uses frequency division duplexing technology and is optimized to support low-mobility pedestrian outdoor usage and wireless local loop applications in a medium-range environment. PACS-Unlicensed B (PACS-UB) is a version of PACS using time division duplexing. PACS-UB has been optimized for private, indoor wireless PBX applications and cordless telephony. Both modes of operation are supported using the same portable hardware and the same signaling protocol.
An executable specification language for specification understanding in object-oriented specification reuse
(1996-06-01)
Chou, SC
;
Chen, JY
;
Chung, CG
;
資訊工程學系
;
Department of Computer Science
System analysis time can be reduced through specification reuse which, however, requires specification understanding. This paper presents an object-oriented executable specification language which reduces understanding time through executing specifications. In addition to being executable, the specification language hides as many classes as possible within subsystems, and explicitly specifies relationships between specification components. This facilitates specification modification. Moreover, the language explicitly specifies interface parameters of specification components. This facilitates specification composition.
The effect of lead impurity on the DC-etching behaviour of aluminum foil for electrolytic capacitor usage
(1996-06-01)
Lin, W
;
Tu, GC
;
Lin, CF
;
Peng, YM
;
材料科學與工程學系
The effects of lead impurity on the etched morphology of high purity aluminum foils for electrolytic capacitor applications were investigated in this work. The lead impurity was either present in as-received aluminum foils or deposited purposely on the foil surface through an immersion-reduction reaction. The amount and distribution of deposited lead varies with the lead content in as-received foil. The as-received foil with higher lead content gave a higher concentration and a more uniform distribution of deposited lead. Uniformly distributed vertical tunnel etchings were obtained when high lead foil, formed by immersion as-received high lead foil in Pb(NO3)(2) solution, was subject to DC-etching. For the as-received lower lead foils, the deposited lead was concentrated in rolling lines which resulted in surface etching along rolling lines. Both the surfacial and cross-sectional etching morphologies are presented in this study, together with the etching mechanism discussed. Copyright (C) 1996 Elsevier Science Ltd.
Zeeman studies of the first excited states of palladium and metal free phthalocyanines in Shpol'skii matrix
(1996-06-01)
Huang, SC
;
Chen, WH
;
交大名義發表
;
電子物理學系
;
National Chiao Tung University
Phthalocyanines (Pcs) are planar molecules of relatively high symmetry and exhibit magneto-optic effects in many ways. We report the Zeeman effect of the first excited states of palladium (Pd-) and free-base (H-2-) Pcs in a 5 K Shpol'skii matrix by direct observation of their fluorescence position shifts. From the experimental data an apparent angular momentum integral, coupling the lowest two Jahn-Teller stabilized crystal field split first excited states, Lambda', was found to be 2.7+/-0.1 (h) over bar for PdPc. No conclusive Lambda' was deduced for H(2)Pc but its value can be estimated to be around the theoretical value of 3 (h) over bar. The experimental data of H(2)Pc revealed a complex structure in the fluorescence band examined, which complicated the analysis of Lambda' but helped unravel the biexponential decay problem of the structure. We infer one narrower band in the structure has the previously reported lifetime of tau 6.3 ns, and the other broader band being similar to 1.8 cm(-1) higher, has tau 3.7 ns. We believe this composite situation also exists for the other tautomeric structure since it also exhibited biexponential decay. (C) 1996 American Institute of Physics.
Temperature-dependent transport properties of n(+) GaAs/low-temperature GaAs/n(+) GaAs structures grown by molecular beam epitaxy
(1996-06-01)
Chen, JF
;
Chen, NC
;
Chiu, SY
;
Wang, PY
;
Lee, WI
The temperature-dependent I-V characteristics of n(+) GaAs low-temperature GaAs(AlGaAs) n(+) GaAs structures in which the low-temperature layers were grown at 250, 350, and 450 degrees C were analyzed. Band conduction with an activation energy of 0.72 eV dominates at T>250 K. Hopping conduction dominates at T<250 K, where the resistivity was found to be insensitive to temperature. From this analysis, it is shown that Fermi level is pinned to an acceptorlike deep level of about 10(17) cm(-3), which lies at 0.72 eV below the conduction band. Measured capacitance can be described in terms of a parallel-plate capacitance with separation being equal to the expected growth thickness. Majority traps (electrons) were observed by deep-level transient spectroscopy with an activation energy about 0.72 eV, confirming the result of the resistivity analysis. In addition, the I-V characteristics were fitted to the simulated curves based on a simplified space-charge limited theory and the result was found to be consistent with the resistivity analysis. (C) 1996 American Institute of Physics.
Stereoselectivity of the Diels-Alder reaction of (E)gamma-Oxo-alpha,beta-unsaturated thioesters with cyclopentadiene
(1996-06-01)
Tsai, SH
;
Chung, WS
;
Wu, HJ
;
應用化學系
;
Department of Applied Chemistry
The stereoselectivity of the Diels-Alder reaction of (E)-gamma-oxo-alpha,beta-unsaturated thioesters 3a-3d with cyclopentadiene is greatly enhanced in the presence of Lewis acids favoring the endo acyl isomers 4a-4d. In the absence of Lewis acid, Diels-Alder reaction of 3a-3d with cyclopentadiene at 25 degrees C gave two adducts 4a-4d and 5a-5d in a ratio of 1:1 respectively. In the presence of Lewis acids, Diels-Alder reaction of 3a-3d with cyclopentadiene gave 4a-4d and 5a-5d in ratios of 75 similar to 94:25 similar to 6 respectively. The stereoelectivity was enhanced to ratios of 95 similar to 98:5 similar to 2 with lowering the reaction temperature. The stereochemistry of the cycloadducts 4 and 5 was confirmed by iodocyclization. Reaction of the endo-thioester 5c with I-2 in aqueous THF at 0 degrees C gave the novel methylthio group rearranged product 6c in 80% yield, the first example of iodolactonization of endo-thioesters. Reaction of the endo-acyl isomer 4b with I-2 under the same reaction conditions gave an isomeric mixture of 7b and 8b in 1:2 ratio. The stereochemistry of the thioester group in 8b was proved by X-ray single-crystal analysis. The solvent effect on the endo selectivity of (Z)-gamma-oxo-alpha,beta-unsaturated thioester 2b was also examined.
Recursive filtering with non-Gaussian noises
(1996-06-01)
Wu, WR
;
Kundu, A
;
電信工程研究所
;
Institute of Communications Engineering
The Kalman filter is the optimal recursive filter, although its optimality can only be claimed under the Gaussian noise environment, In this paper, we consider the problem of recursive filtering with non-Gaussian noises, One of the most promising schemes, which was proposed by Masreliez, uses the nonlinear score function as the correction term in the state estimate, Unfortunately, the score function cannot be easily implemented except for simple cases, In this paper, a new method for efficient evaluation of the score function is developed, The method employs an adaptive normal expansion to expand the score function followed by truncation of the higher order terms, Consequently, the score function can be approximated by a few central moments, The normal expansion is made adaptive by using the concept of conjugate recentering and the saddle point method, It is shown that the approximation is satisfactory, and the method is simple and practically feasible, Experimental results are reported to demonstrate the effectiveness of the new algorithm.
Laboratory testing of three direct reading dust monitors
(1996-06-01)
Tsai, CJ
;
Shih, TS
;
Lin, JD
;
機械工程學系
;
環境工程研究所
This study used a dust chamber to test the response of three direct reading dust monitors, GCA MINIRAM PDM-3, Sibata PCD-1, and TSI 8510, to different dust materials having similar size distributions. Total dust concentrations obtained by open-face filters were used as standards for comparing total dust concentration readings, while respirable dust concentrations calculated from particle size distribution measured by the MOUDI cascade impactor were used as standards for comparing respirable dust concentration readings. It was found that the GCA MINIRAM PDM-3 was accurate within +10-16% in regard to total dust concentration, independent of dust material. The calibration constant k of the Sibata PCD-1 was close to 6.0 for both quartz and SAE fine dusts and was independent of dust concentrations. However, for carbon particles, k remains nearly constant from 13-16 only when the total dust concentration is greater than 3.0 mg/m(3). The TSI 8510 seriously underestimates the concentration of SAE fine dust, and is more accurate for quartz and carbon dusts when respirable dust concentration is less than 6.0 mg/m(3). When respirable dust concentration is greater than 6.0 mg/m(3), it will also underestimate quartz dust concentration substantially, while it remains accurate for carbon dust.
Multi-class clustering by analytical two-class formulas
(1996-06-01)
Lin, JC
;
資訊工程學系
;
Department of Computer Science
This paper proposes a new clustering method based on the hierarchical use of the analytical two-class clustering tool introduced by Lin and Tsai.(1) The method comprises two phases. In the first phase, called the splitting phase, the data set is hierarchically decomposed into some subsets. In the second phase, called the merging phase, the set-to-set distances between these subsets are checked so that some subsets can be merged back together to obtain better clustering results. We use the idea of the so-called dense cut to determine when to stop the splitting phase. We also use a trace-following technique for the so-called boundary data to reduce significantly the computational load involved in the merging phase. Two algorithms are provided, and many experiments are included to show that the data being processed are not required to be linearly separable, noiseless, or formed of spherical clusters.
Design of a fuzzy traffic controller for ATM networks
(1996-06-01)
Cheng, RG
;
Chang, CJ
;
電信工程研究所
;
電信研究中心
;
Institute of Communications Engineering
This paper presents the design of a fuzzy traffic controller that simultaneously manages congestion control and call admission control for asynchronous transfer mode (ATM) networks. The fuzzy traffic controller is a fuzzy implementation of the two-threshold congestion control method and the equivalent capacity admission control method extensively studied in the literature. It is an improved, intelligent implementation that not only utilizes the mathematical formulation of classical control but also mimics the expert knowledge of traffic control, We appropriately choose input linguistic variables of the fuzzy traffic controller so that the controller is a closed-loop system with stable and robust operation. We extract knowledge of conventional control methods from numerous analytical data using a clustering technique and then use this knowledge to set parameters of the membership functions and fuzzy control rules via fuzzy set manipulation (linguistically stated but mathematically treated) with the aid of an optimization technique named genetic algorithm (GA). Simulation results show that the proposed fuzzy admission control improves system utilization by a significant 11%, while maintaining the quality of service (QoS) contract comparable with that of the conventional equivalent capacity method. The performance of the proposed fuzzy congestion control method is also 4% better than that of the conventional two-threshold congestion control method.
Feedforward and feedback control strategy for active noise cancellation in ducts
(1996-06-01)
Hu, JS
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This paper presents the theoretical work about active noise cancellation in ducts. The proposed control system is designed based on the assumption of a one-dimensional sound field. The controller consists of a feedforward block which serves as a noise observer. The feedback portion of the control algorithm is to minimize residual disturbances. Closed-loop stability of the MIMO (multiple-input-multiple-output) system is analyzed and the result shows that the dynamic influenced by the space-feedforward and feedback controllers can be decoupled. Both semi-infinite and finite-length ducts are considered in this study and simulation examples are given to illustrate the effectiveness of the proposed controllers.
The effect of lead impurity on the DC-etching behaviour of aluminum foil for electrolytic capacitor usage
(1996-06-01)
Lin, W
;
Tu, GC
;
Lin, CF
;
Peng, YM
;
材料科學與工程學系
The effects of lead impurity on the etched morphology of high purity aluminum foils for electrolytic capacitor applications were investigated in this work. The lead impurity was either present in as-received aluminum foils or deposited purposely on the foil surface through an immersion-reduction reaction. The amount and distribution of deposited lead varies with the lead content in as-received foil. The as-received foil with higher lead content gave a higher concentration and a more uniform distribution of deposited lead. Uniformly distributed vertical tunnel etchings were obtained when high lead foil, formed by immersion as-received high lead foil in Pb(NO3)(2) solution, was subject to DC-etching. For the as-received lower lead foils, the deposited lead was concentrated in rolling lines which resulted in surface etching along rolling lines. Both the surfacial and cross-sectional etching morphologies are presented in this study, together with the etching mechanism discussed. Copyright (C) 1996 Elsevier Science Ltd.
Risk analysis for flow duration curve based seasonal discharge management programs
(1996-06-01)
Kao, JJ
;
Bau, SF
;
交大名義發表
;
環境工程研究所
;
National Chiao Tung University
A non-seasonal discharge standard may be too stringent and not cost-effective for a season of large flow, if the variation of seasonal streamflow of a river is significant. Seasonal discharge programs established based on streamflow variation were therefore explored in this work. A design procedure using the dow duration curve method, two total-mass-load based discharge programs, linear programming, and Monte-Carlo analysis is proposed for determining and analyzing the pertinent seasonal division of a two-season discharge management program. The flow duration curve method was used to compute the design low flow. The maximal total waste load and uniform treatment programs were the two total-mass-load based programs analysed. Linear programming models were established to determine the optimal division of seasons based on the objective of maximally allowable total waste load. Monte-Carlo simulation with QUAL2E-UNCAS was implemented to assess the risk of violation of water quality of seasonal programs. The proposed procedure is demonstrated in a case study of the Tung-Kang River basin in Taiwan. Copyright (C) 1996 Elsevier Science Ltd
Transient combustion of a heating droplet in a gravitational environment
(1996-06-01)
Huang, LW
;
Chen, CH
;
機械工程學系
;
Department of Mechanical Engineering
The transient combustion characteristics of a droplet suddenly exposed to the envelope flames in an atmospheric environment are studied numerically. Combustion can be divided into a droplet heating-up and a constant-droplet-temperature burning. The naturally-convective flow is not known a priori, but provided as part of the solution. During the heating-up stage, the temperature and evaporation rate of droplet increase sharply, and the square of diameter decreases slightly as time proceeds. In the following stage, the droplet temperature remains constant, the evaporation rate and droplet diameter decrease with time. The flowfield of natural convection is also presented to demonstrate its interaction with the flame and the transient process. Finally, the fuel accumulation phenomenon is identified and it results in an reduction of evaporation constant.