Browsing by Issue Date, starting with "1998-06-25"

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Two-dimensional beam-scanning phase-shifterless technique using linear active leaky-wave antenna array
(1998-06-25)
Hu, CC
;
Jou, CF
;
Wu, JJ
;
傳播研究所
;
Institute of Communication Studies
A novel two-dimensional electronic beam scanning technique using a linear leaky-wave antenna array with coupled oscillators is introduced, eliminating the need for phase shifters. The measured H-plane main beam carl be continuously scanned from 70 to 40 degrees as the frequency varies from 7.9 to 9.05 GHz. By detuning the free running frequencies of the end elements, the measured E-plane main beam can be continuously scanned from -22 to +26 degrees.
The use of a biomolecular target for crystalline carbon nitride film deposition by Ar ion-beam sputtering without any other source of nitrogen
(1998-06-29)
Chen, LC
;
Lu, TR
;
Kuo, CT
;
Bhusari, DM
;
Wu, JJ
Carbon nitride films have been synthesized by argon ion-beam sputtering from a biomolecular compound target, 8-aza-6-aminopurine (C4N6H4) The compound has a six-membered ring structure similar to that existing in the hypothetical beta-C3N4. Except fur the target material, no other source of nitrogen was used during sputtering deposition. It was found that crystalline carbon nitride with high N/C atomic composition ratios of 0.43-0.56 can be formed even at room temperature. The infrared spectra of the film exhibit two peaks at 1383 and 1643 cm(-1), corresponding to C-N and C=N stretching modes, respectively. No detectable peak at 2200 cm(-1) (C=N stretching mode) is observed. Both x-ray diffraction and transmission electron microscopy show a very strong broad peak at 3.2 Angstrom, comparable to the d spacing of the (110) orientation in the beta-C3N4 structure. However, it is suggested that the film contains a nanocrystalline phase with a crystal structure yet to be determined. (C) 1998 American Institute of Physics.
Nonlocal extended conformal algebras associated with multiconstraint KP hierarchy and their free field realizations
(1998-06-30)
Shaw, JC
;
Tu, MH
;
應用數學系
;
物理研究所
;
Department of Applied Mathematics
We study the conformal properties of the multiconstraint KP hierarchy and its nonstandard partner by covariantizing their corresponding Lax operators. The associated second Hamiltonian structures turn out to be nonlocal extensions of W-n algebra by some integer or half-integer spin fields depending on the order of the Lax operators. In particular, we show that the complicated second Hamiltonian structure of the nonstandard multiconstraint KP hierarchy can be simplified by factorizing its Lax operator to multiplication form. We then diagonalize this simplified Poisson matrix and obtain the free held realizations of its associated nonlocal algebras.
An inheritance flow model for class hierarchy analysis
(1998-06-30)
Chen, JL
;
Wang, FJ
;
資訊工程學系
;
Department of Computer Science
This paper presents an inheritance flow model, which represents the inheritance relationships among classes as a flow graph. A flow operation is associated with each attribute and method in a class to denote the defined (redefined) or inherited member. An inherited member can be deemed as being handled by a sequence of how operations along a path in the flow graph. This model provides several analyses in a class hierarchy, such as implicit inherited member and polymorphic method invocation. These analyses may be applied in various fields of software engineering, such as static analysis, maintenance, and complexity measurement. (C) 1998 Elsevier Science B.V. All rights reserved.
A homophonic DES
(1998-06-30)
Hsieh, TM
;
Yeh, YS
;
Hsieh, YC
;
Wang, CC
;
資訊科學與工程研究所
In this paper, we propose a variant of DES called a homophonic DES. The DES algorithm is strengthened by adding some random bits into the plaintext, which are placed in particular positions to maximize diffusion, and to resist differential attack. (C) 1998 Elsevier Science B.V. All rights reserved.
Barrier properties of very thin Ta and TaN layers against copper diffusion
(1998-07-01)
Wang, MT
;
Lin, YC
;
Chen, MC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Diffusion barrier properties of very thin sputtered Ta and reactively sputtered TaN films used as a barrier layer between Cu and Si substrates were investigated using electrical measurement and materials analysis. The Cu/Ta/p(+)-n junction diodes with the Ta barrier of 5, 10, and 25 nm thicknesses were able to sustain a 30 min thermal annealing at temperatures up to 450, 500, and 550 degrees C, respectively, without causing degradation to the device's electrical characteristics. The barrier capability of Ta layer can be effectively improved by incorporation of nitrogen in the Ta film using reactive sputtering technique. For the Cu/TaN/p(+)-n junction diodes with the TaN barrier of 5,10, and 25 nm thicknesses, thermal stability was able to reach 500, 600, and 700 degrees C, respectively. We found that failure of the very thin Ta and TaN barriers was not related to Ta silicidation at the barrier/Si interface. Failure of the barrier layer is presumably due to Cu diffusion through the barrier layer during the process of thermal annealing via local defects, such as grain boundaries and stress-induced weak points.
Numerical analysis of a burning droplet with internal circulation in a gravitational environment
(1998-07-01)
Huang, LW
;
Chen, CH
;
機械工程學系
;
Department of Mechanical Engineering
A theoretical analysis of steady burning droplets with internal circulation in the presence of normal atmosphere and gravity is presented. The normalized system governing the gas phase consists of the complete set of conservation equations in r-z coordinates and includes finite-rate global kinetics. For the liquid phase, it includes continuity and momentum conservation equations. Thermodynamic equilibrium is assumed along the gas-liquid interface, which is not stationary. A body-fitted grid generation technique is used to handle irregular boundaries. The parametric study is performed by changing droplet diameter. The induced convection flowfield is presented to demonstrate its interaction with the flame and the liquid flow motion. The predicted results show that there exists one, two, or three cells within the burning droplet, depending on its diameter. The occurrence of an extra cell is due to reverse flow in the gas phase generated by interaction of the induced flow and blowing velocity. Comparison with the case where internal flow is not considered, for a small droplet the effect of internal circulation on mass evaporation rate can be neglected. On the other hand the internal flow will increase the mass evaporation rate.
Fuzzy neural systems for controlling sound localisation in stereophonic reproduction
(1998-07-01)
Chang, PR
;
Tan, TH
;
電信工程研究所
;
Institute of Communications Engineering
The paper presents a new fuzzy logic control (FLC) approach which leads to a stereophonic reproduction controller for localising an auditory image in the desired direction and at the expected distance. Since an auditory event is usually less precisely resolved than the physical sound space, the auditory event need not coincide with a physical sound source, and can occur at a position where nothing is visible to a listener. It turns out that controlling the auditory image is more difficult than the localisation of a sound image. Unlike the conventional sound image localisation approach, our fuzzy logic controller can take account of knowledge in human auditory perception. The ambiguous human auditory perception in conjunction with the spatial reverberation from the surrounding environment can be represented by a number of fuzzy-set values. From these fuzzy representations, the auditory image localisation controller characterises the function of how control outputs depend on control inputs as fuzzy implications or associations. Furthermore, the overall stereophonic reproduction controller can be realised by a 45-rule fuzzy associative memory (FAM) system. The performance of FLC-based auditory image localisation is verified in a number of experiments.
Reaching strong consensus in the presence of mixed failure types
(1998-07-01)
Siu, HS
;
Chin, YH
;
Yang, WP
;
資訊工程學系
;
Department of Computer Science
The Strong Consensus (SC) is a variant of the conventional distributed consensus problem. The protocol designed for the SC problem requires that the agreed value among fault-free processors be one of the fault-free processor's initial value. The SC problem is re-examined with the assumption of mixed failure types (also referred to as the hybrid fault model). Compared with the features of the existing protocols, the underlying network topologies of the proposed protocol do not have to be fully connected, the mixed failure types can be tolerated, and no prior information of the system's faulty status is required. The proposed protocol can tolerate a maximum number of faults to enable each fault-free processor to reach an agreement with a minimum number of message exchanges. (C) 1998 Published by Elsevier Science Inc. All rights reserved.
Fabrication and raman analysis of ZnSe quantum dots in glass matrix thin films by pulsed laser evaporation
(1998-07-01)
Yin, SB
;
Chen, L
;
Hsieh, WF
;
光電工程學系
;
Department of Photonics
We have successfully fabricated ZnSe-microcrystal-doped silica-glass thin films by pulsed laser evaporation from ZnSe powder embedded in sol-gel glass targets and demonstrated that the spatial cell-elation model call be used to analyze the LO Raman mode of ZnSe semiconductor doped glass thin films. The obtained correlation lengths differ from the real sizes of the particulates observed by scanning electron microscopy which may bz due to the fact that the particulates art polycrystalline, with different orientations separated by grain boundaries, and the correlation length just provides a measure of the separated average grain dimension. The photoluminescence spectrum indicates that the carriers may tunnel through the grain walls in the polycrystalline particulates. Low temperature annealing only causes aggregate of particulates without merging the grain boundaries.
Alkaline hydrolysis of the sludge generated from a high-strength, nitrogenous-wastewater biological-treatment process
(1998-07-01)
Lin, JG
;
Ma, YS
;
Huang, CC
;
環境工程研究所
;
Institute of Environmental Engineering
The production of acrylonitrile butadiene styrene (ABS, a petrochemical product) in Taiwan is one of the biggest manufactoring processes in the world. The large amount of ABS sludge generated in the wastewater treatment plant from the highly nitrogenous-wastewater contains significant amount of complex and biorefractory organic substances. Resource recovery is the optimal conception of the traditional sludge treatment for the purpose of organic matters removal. An alkaline pretreatment method is used to enhance the efficiency of biological hydrolysis of industrial wastewater sludge in the present study. The operating conditions for the alkaline pretreatment of the ABS sludge were maintained at room temperature (25+/-3 degrees C), reaction time of 24h, total solids in the feed of 0.5-2%, and NaOH dosages of 10-50 mg l(-1). Considering the increasing concentrations of soluble chemical oxygen demand and biochemical oxygen demand, the experimental results indicated that the alkaline pretreatment method was useful in biodegradability enhancement. (C) 1998 Elsevier Science I;tn. All rights reserved.
New RSA cryptosystem hardware design based on Montgomery's algorithm
(1998-07-01)
Yang, CC
;
Chang, TS
;
Jen, CW
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this paper, we propose a new algorithm based on Montgomery's algorithm to calculate modular multiplication that is the core arithmetic operation in an RSA cryptosystem. The modified algorithm eliminates over-large residue and has very short critical path delay that yields a very high-speed processing. The nevi architecture based on this modified algorithm takes about 1.5n(2) clock cycles on the average to finish one n-bit RSA operation. We have implemented a 512-bit single-chip RSA processor based on the modified algorithm with Compass 0.6-mu m SPDM CMOS cell library. The simulation results show that the processor can operate up to 125 MHz and deliver the baud rate of 164 Kbits/s on the average.
Plant uncertainty analysis in a duct active noise control problem by using the H-infinity theory
(1998-07-01)
Bai, MR
;
Lin, HH
;
機械工程學系
;
Department of Mechanical Engineering
Plant uncertainty is one of the major contributing factors that could affect the performance as well as stability of active noise control (ANC) systems. Plant uncertainty may be caused by either the errors in modeling, computation, and measurement, or the perturbations in physical conditions. These factors lead to deviations of the plant from the nominal model, which will in turn affect the robustness of the control system. In this paper, the effects due to changes in physical conditions on the ANC system are investigated. The analysis is carried out in terms of performance and robustness by using a general framework of the H-infinity robust control theory. The size of plant uncertainty is estimated according to the infinity norm of the perturbations to physical conditions, which provides useful information for subsequent controller design that accommodates both performance and stability in an optimal and robust manner. The guidelines for designing the ANC systems with reference to plant uncertainties are also addressed. (C) 1998 Acoustical Society of America. [S0001-4966(98)02007-4].
Improving radiation hardness of EEPROM/flash cell by N2O annealing
(1998-07-01)
Huang, TY
;
Jong, FC
;
Chao, TS
;
Lin, HC
;
Leu, LY
The effects of an N2O anneal on the radiation effects of a split-gate electrical erasable programmable read only memory (EEPROM)/flash cell with a recently-proposed horn-shaped floating gate were studied. We have found that although the cells appear to survive 1 Mrad(Si) Co-60 irradiation without data retention failure, the write/erase cycling endurance was severely impeded after irradiation. Specifically, the write/erase cycling endurance was degraded to 20 K from the pre-irradiation value of 50 K, However, by adding an N2O annealing step after the interpoly oxidation, the after-irradiation write/erase cycling endurance of the resultant cell can be significantly improved to over 45 K, N2O annealing also improves the after-irradiation program and erase efficiencies. The N2O annealing step therefore presents a potential method for enhancing the robustness of the horn-shaped floating-gate EEPROM/flash cells for radiation-hard applications.
The creation of nanometer magnetic domain structure in artificially pinning hole of magneto-optical recording material
(1998-07-01)
Wu, TH
;
Wu, JC
;
Chen, BM
;
Shieh, HPD
;
光電工程學系
A novel method for pinning the magnetic domain in artificially pinning hole has been developed for magneto-optical (Mo) thin film material Dy-x(FeCo)(1-x). The artificially pinning holes were fabricated using electron-beam lithography. Hole arrays with square, star, and circle shapes had been made in this study. However, the nanometer scale magnetic domains could be formed inside the hole arrays if the pinning hole geometry was not well defined, and the pinning domain may induce media noise.
Correspondence on 'Planar constrained terminals over-the-cell router'
(1998-07-01)
Yan, JT
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
A new routing model with constrained terminal structure for over-the-cell channel routing and a graph theoretical algorithm for solving the planar constrained terminals over-the-cell routing problem have recently been published. The routing model with constrained terminal structure assigns the connection constraint between adjacent layers on terminals and makes use of the vacant locations on each layer for over-the-cell routing. Based on the constrained terminal structure, a graph theoretical algorithm is proposed to complete planer routing layer by layer for over-the-cell channel routing. The new routing model and the graph theoretical algorithm are shown to be flawed, and corrections are suggested.
Matrix formulation of Hamiltonian structures of constrained KP hierarchy
(1998-07-01)
Huang, WJ
;
Shaw, JC
;
Tu, MH
;
應用數學系
;
Department of Applied Mathematics
We give a matrix formulation of the Hamiltonian structures of constrained KP hierarchy. First, we derive from the matrix formulation the Hamiltonian structure of the one-constraint KP hierarchy, which was originally obtained by Oevel and Strampp. We then generalize the derivation to the multiconstraint case and show that the resulting bracket is actually the second Gelfand-Dickey bracket associated with the corresponding Lax operator. The matrix formulation of the Hamiltonian structure of the one-constraint KP hierarchy in the form introduced in the study of matrix model is also discussed. (C) 1998 American Institute of Physics. [S0022-2488(98)01207-9].
On existential polarity wh-phrases in Chinese
(1998-07-01)
Lin, JW
;
外國語文學系
;
Department of Foreign Languages and Literatures
Fast full search in motion estimation by hierarchical use of Minkowski's inequality (humi)
(1998-07-01)
Lu, JY
;
Wu, KS
;
Lin, JC
;
資訊工程學系
;
Department of Computer Science
In this paper, we extend the idea of successive elimination algorithm (SEA) to obtain a fast full search (FS) algorithm accelerating the block matching procedure of motion estimation. Based on the monotonic relation between the accumulated absolution distortions (AAD) obtained for distinct layers of a pyramid structure; the proposed method successfully rejects many impossible candidates considered in the FS. The derivation of the monotonicity relation repeatedly uses in a four-dimensional vector space the l(1)-version of Minkowski's inequality, an inequality which is quite well-known in the field of mathematics. Simulation results show that the processing speed is faster than that of several well-known fast full search methods, including the SEA that uses just once the Minkowski's inequality (in a vector space of 256 dimension when the block size is 16 x 16). The processing speed of the proposed method is also competitive with that of the three-step search (TSS), which is often used for block matching in interframe video coding, although the visual quality performance of TSS is usually a little poorer than that of the FS. (C) 1998 Pattern Recognition Society. Published by Elsevier Science Ltd. All rights reserved.
Design of acceleration/deceleration profiles in motion control based on digital FIR filters
(1998-07-01)
Chen, CS
;
Lee, AC
;
機械工程學系
;
Department of Mechanical Engineering
In motion control, the reference commands should pass through the acceleration/deceleration (Acc/Dec) processor before being fed into the servo loop. Consequently, not only can a smooth motion profile be obtained but undesirable vibration can be avoided. In this study, we develop a systematic design procedure for the Acc/Dec processor based on the discrete time finite-impulse-response (FIR) filter design technique with some necessary conditions. Compared with the conventional Acc/Dec scheme, the FIR Acc/Dec scheme poses the advantage that the contouring error can be analyzed. Also, the contouring error caused by the conventional Acc/Dec scheme is evaluated by demonstrating a mapping technique from the conventional Acc/Dec scheme to the FIR Acc/Dec scheme. The proposed Acc/Dec algorithm is quite flexible and efficient, creating space for users to use more sophisticated profiles to more efficiently match the system constraints with minimum contouring errors. Simulation and experimental results verify that the proposed Acc/Dec processor can effectively improve the motion accuracy. (C) 1998 Elsevier Science Ltd. All rights reserved.