Browsing by Issue Date, starting with "2002-11-01"

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Improving the electrical integrity of Cu-CoSi2 contacted n(+)p junction diodes using nitrogen-incorporated Ta films as a diffusion barrier
(2002-11-01)
Yang, WL
;
Wu, WF
;
You, HC
;
Ou, KL
;
Lei, TF
The study on improving the electrical integrity Of Cu-CoSi2 contacted-junction diodes by using the reactively sputtered TaNx as a diffusion barrier is presented in this paper. In this study, the Cu(300 nm)-CoSi2 (50 nm)/n(+)p junction diodes were intact with respect to metallurgical reaction up to a 350 degreesC thermal annealing while the electrical characteristics started to degrade after annealing at 300 degreesC in N-2 ambient for 30 min. With the addition of a 50-nm-thick TaNx diffusion barrier between Cu and CoSi2, the junction diodes were able to sustain annealing up to 600 degreesC without losing the basic integrity of the device characteristics, and no metallurgical reaction could be observed even after a 750 degreesC annealing in furnace. In addition, the structure of TaNx layers deposited on CoSi2 at various nitrogen flow rates has been investigated. The TaNx film with small grain sizes deposited at nitrogen flow ratios exceeding 10% shows better barrier capability against Cu diffusion than the others.
Role of positive trapped charge in stress-induced leakage current for flash EEPROM devices
(2002-11-01)
Wang, TH
;
Zous, NK
;
Yeh, CC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The transient behavior of hot hole (HH) stress-induced leakage current (SILC) in tunnel oxides is investigated. The dominant SILC mechanism is positive oxide charge-assisted tunneling (PCAT). The transient effect of SILC is attributed to positive oxide charge detrapping and thus the reduction of PCAT current. A correlation between SILC and stress-induced substrate current is observed. Our study shows that both SILC and stress-induced substrate current have power law time-dependence t(-n) with the power factor n about 0.7 and 1, respectively. Numerical analysis for PCAT current incorporating a trapped charge caused Coulombic potential in the tunneling barrier is performed to evaluate the time-and field-dependence of SILC and the substrate current. Based on our model, the evolution of threshold voltage shift with read-disturb time in a Flash EEPROM cell is derived. Finally, the dependence of SILC on oxide thickness is explored. As oxide thickness reduces from 100 Angstrom to 53 Angstrom, the dominant SILC mechanism is found to change from PCAT to neutral trap-assisted tunneling (TAT).
Evolutionary programming synthesis of optimal long-period fiber grating filters for EDFA gain flattening
(2002-11-01)
Lee, CL
;
Lai, Y
;
光電工程學系
;
Department of Photonics
An innovative long-period fiber grating (LPG) synthesis method based on the stochastic evolutionary programming (EP) algorithms is demonstrated to be effective for designing optimal LPG filters. Synthesis of a single-stage LPG filter for the entire C-band erbium-doped fiber amplifier (EDFA) gain flattening is used as an example to show the feasibility and the effectiveness of the proposed algorithm. To the best of our knowledge, this is the first demonstration that good EDFA gain flattening for the entire band can be achieved with a single-stage LPG filter that is properly designed.
An investigation of dust emissions from unpaved surfaces in Taiwan
(2002-11-01)
Tsai, CJ
;
Chang, CT
;
環境工程研究所
;
Institute of Environmental Engineering
One of the critical problems in making an effective strategy to control fugitive road dust is to estimate the emission factor accurately. The paper presents measured results of emission factor at field and in a wind tunnel. For the field study, three unpaved roads in Hsin Chu, Taiwan were tested. For the wind tunnel testing, the tested road dust was also collected from the field. Results of field study indicate that the emission factor of unpaved roads increases with the increasing wind speed, the number of vehicles and the speed of vehicles. It can be predicted as e (g/m(2)day) = 8.72 x 10(-3) x V-w(0.64) X s(0.19) x M-0.05 x V-v(1.32) x N-v(1.11) (V-w, m/s-wind speed, s, %-silt content of road dust; M, %-moisture content of road dust; N-v, #/h-number of vehicles: V-v, km/h-speed of vehicles) by the multi-variable regression technique. The fractions of PM10 and PM2.5, in the TSP reentrained from the unpaved roads are 20.6 +/- 12.9% and 2.3 +/- 1.2%, respectively. The wind tunnel test results show that air acceleration rate and edge effect of the dust surface increase the emission factors considerably. As air acceleration rate increases from 0.1 to 1.5 m/s(2), the emission factor increases linearly from 1.0 x 10(-4) to 7.0 x 10(-4) kg/m(2) s. However, test results show no significant effect of air acceleration and edge effect of dust surface on the threshold wind speed of reentrainment. (C) 2002 Elsevier Science B.V. All rights reserved.
Coexistence of a self-induced transparency soliton and a Bragg soliton
(2002-11-01)
Tseng, HY
;
Chi, S
;
光電工程研究所
;
Institute of EO Enginerring
We theoretically show that a self-induced transparency (SIT) soliton and a Bragg soliton can coexist in a nonlinear photonic band gap (PBG) medium doped uniformly with inhomogeneous-broadening two-level atoms. The Maxwell-Bloch equations for the pulse propagating through such a uniformly doped PBG structure are derived first and further reduced to an effective nonlinear Schrodinger equation. This model describes an equivalent physical mechanism for a Bragg-soliton propagation resulting from the effective quadratic dispersion balancing with the effective third-order nonlinearity. Because the resonant atoms are taken into account, the original band gap can be shifted both by the dopants and the instantaneous nonlinearity response originating from an intense optical pulse. As a result, even if a SIT soliton with its central frequency deep inside the original forbidden band, it still can propagate through the resonant PBG medium as long as this SIT soliton satisfies the effective Bragg-soliton propagation. An approximate soliton solution describing such coexistence is found. We also show that the pulse width and group velocity of this soliton solution can be uniquely determined for given material parameters, atomic transition frequency, and input central frequency of the soliton. The numerical examples of the SIT soliton in a one-dimensional As2S3-based PBG structure doped uniformly with Lorentzian line-shape resonant atoms are shown. It is found that a SIT soliton with similar to100-ps width in such a resonant PBG structure can travel with the velocity being two orders of magnitude slower than the light speed in an unprocessed host medium.
Effect of annealing on the structural and optical properties of AgGaS2 thin films prepared by pulsed laser deposition
(2002-11-01)
Hsu, HC
;
Chen, HH
;
Kuo, SY
;
Chang, CS
;
Hsieh, WF
The influence of annealing on the AgGaS2 films groom by pulsed laser deposition has been investigated. The X-ray diffraction results show the AgGaS2 films were found with preferential orientation (1 1 2) normal to the surface and silver droplets,were diminished after the post-annealing. Photoluminescence (PL) measurements reveled the exciton energy is slightly red shifted that is possibly due to the thermal strain effect. The binding energy of the shallow, donors is similar to28 meV determined from temperature dependent PL spectra, In addition, the A-exciton and the B/C-exciton could be observed in the transmittance spectra at room temperature. (C) 2002 Elsevier Science B.V. All rights reserved.
A reverse logistics cost minimization model for the treatment of hazardous wastes
(2002-11-01)
Hu, TL
;
Sheu, JB
;
Huang, KH
;
運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
This study presents a cost-minimization model for a multi-time-step, multi-type hazardous-waste reverse logistics system. A discrete-time linear analytical model is formulated that minimizes total reverse logistics operating costs subject to constraints that take into account such internal and external factors as business operating strategies and governmental regulations. Application cases are presented to demonstrate the feasibility of the proposed approach. By using the proposed model coupled with operational strategies, it is shown that the total reverse logistics costs for the applications cases can be reduced by more than 49%. (C) 2002 Elsevier Science Ltd. All rights reserved.
On the singularity induced by boundary conditions in a third-order thick plate theory
(2002-11-01)
Huang, CS
;
土木工程學系
;
Department of Civil Engineering
This paper thoroughly examines the singularity of stress resultants of the form r(-xi)F(theta) for 0less than or equal toxiless than or equal to1 as r --> 0 (Williams-type singularity) at the vertex of an isotropic thick plate; the singularity is caused by homogeneous boundary conditions around the vertex. An eigenfunction expansion is applied to derive the first known asymptotic solution for displacement components, from the equilibrium equations of Reddy's third-order shear deformation plate theory. The characteristic equations for determining the singularities of stress resultants are presented,for ten sets of boundary conditions. These characteristic equations are independent of the thickness of the plate, Young modulus, and shear modulus, but some do depend on Poisson's ratio. The singularity orders of stress resultants for various boundary conditions are expressed in graphic form as a function of the vertex angle. The characteristic equations obtained herein are compared with those from classic plate theory and first-order shear deformation plate theory. Comparison results indicate that different plate theories yield different singular behavior for stress resultants. Only the vertex with simply supported radial edges (S(I)_S(I) boundary condition) exhibits the same singular behavior according to all these three plate theories.
Novel planar, square-shaped, dielectric-waveguide, single-, and dual-mode filters
(2002-11-01)
Chang, CY
;
Hsu, WC
;
電信工程研究所
;
Institute of Communications Engineering
This paper presents a novel concept of a square-shaped dielectric-waveguide resonator, which can easily realize a dielectric-waveguide cross-coupled filter or a dielectric-waveguide dual-mode filter, using the conventional printed circuit board (PCB) process. This planar dielectric-waveguide resonator has a higher Q value than a microstrip resonator. The physical mechanisms of both single- and dual-mode filters are elucidated. Some new coupling structures are developed for undergoing the PCB process. Filter design procedures are detailed. Design curves for the coupling coefficients of internaland external-coupling structures are determined by full-wave finite-element-method electromagnetic calculations. Measurement results are highly consistent with theory for all trial filters. This study offers an effective means of producing low-cost high-performance planar circuit filters.
Experimental evaluation of adaptive predictive control for rotor vibration suppression
(2002-11-01)
Bai, MR
;
Ou, KY
;
機械工程學系
;
Department of Mechanical Engineering
An on-line active control technique for suppressing rotor vibration is proposed. Linear voice coil motors mounted on a ball bearing housing are used for generating counter forces to cancel the transverse vibrations of shaft due to imbalance, misalignment, and so forth. Controllers are designed by using the impulse response-based model predictive control (IMPC) and generalized predictive control (GPC). Recursive-least-square (RLS) method is employed for real-time system identification. Multiple channel active control systems are implemented on the platform of a digital signal processor (DSP). Experimental evaluation indicated that the proposed methods were effective in suppressing the periodic disturbances due to constant as well as variable rotor speed. In particular, GPC has achieved the most satisfactory performance in terms of vibration attenuation and convergence speed.
Forecast of development trends in Taiwan's machinery industry
(2002-11-01)
Chang, PC
;
Wang, CP
;
Yuan, BJC
;
Chuang, KT
;
科技管理研究所
Industry transformation oriented toward high technology is being expected in the next 10 years by targeting Taiwan becoming an island of the technology. The machinery industry, which has been playing a vital role in Taiwan's economic development in the past, should be continuously emphasized during the course of the future development. This paper presents a detailed study on the future development of Taiwan's machinery industry along with the valuable proposals to the government policy and the investment strategy to the private sectors. The 10-year forecasting survey based on the strength, weakness, opportunity and threats (SWOT) analysis was made through an integrated professional team using the Delphi method. The derived results of market growth forecasting and the projected high potential products are further elaborated in the paper. (C) 2002 Elsevier Science Inc. All rights reserved.
Observation of laser transverse modes analogous to a SU(2) wave packet of a quantum harmonic oscillator
(2002-11-01)
Chen, YF
;
Lan, YP
;
電子物理學系
;
光電工程研究所
;
Department of Electrophysics
We report the generation of a new type of laser transverse mode that is analogous to a SU(2) elliptical wave packet of a quantum harmonic oscillator. Experimental results show that using a doughnut pump profile to excite an isotropic microchip laser in a spherical cavity can generate the elliptical transverse modes. The formation of elliptical transverse modes is found to be a spontaneous locking process of Hermite-Gaussian modes within the same family. The chaotic relaxation oscillation caused by the interaction of two nearly degenerate elliptical modes is also observed.
Investigations of pulse current electrodeposition for damascene copper metals
(2002-11-01)
Chang, SC
;
Shieh, JM
;
Dai, BT
;
Feng, MS
;
材料科學與工程學系
The influence of current density, duty cycle, and frequency of the applied pulse current on film qualities of electroplated copper was discussed. With various filled damascene structures, the corresponding filling power was optimized in a range of pulse current frequency. The optimized pulse current plating in conjunction with a leveler-free electrolyte resulted in a defect-free filling in approximate 100 nm damascenes and reduced the resistivity of Cu deposits. (C) 2002 American Vacuum Society.
Investigation of carrying agents on microstructure of electroplated Cu films
(2002-11-01)
Shieh, JM
;
Chang, SC
;
Dai, BT
;
Feng, MS
;
材料科學與工程學系
Adding high molecular-weight polyethylene glycol (PEG) as a carrying agent benefits Cu electroplating from the viewpoint of an increase in both filling capability and films' conductivity, when plated in a lower current-density region. On electroplating in a higher current-density region, a gradually decreasing grain size from the top to bottom of Cu films occurs in the electrolyte without PEG or with PEG200. In comparison, sharp grains are formed for the mentioned multi-domain crystallization for those films deposited by the electrolyte containing PEG2000 or PEG6000 due to its lower surface tension which facilitates grain growth along the higher electric field. The used concentration of PEG was flexible due to the fact that the surface morphology, resistivity and deposition rate of deposited films remained almost unchanged over a wide PEG concentration range.
Dynamic periodic location area update in mobile networks
(2002-11-01)
Lin, YB
;
Lee, PC
;
Chlamtac, I
;
資訊工程學系
;
Department of Computer Science
In mobile communications networks, periodic location area update (PLAU) is utilized to detect the presence of a mobile station (MS). In 3GPP Technical Specifications 23.012 and 24.008, a fixed PLAU scheme was proposed for the Universal Mobile Telecommunications System (UNITS), where the interval between two PLAUs is of fixed length. We observe that MS presence can also be detected through call activities and normal location area update (NLAU). Therefore, we propose a dynamic PLAU scheme where the PLAU interval is dynamically adjusted based on the call traffic and NLAU rate. An analytic model is developed to investigate the performance of dynamic and fixed PLAU schemes. This paper provides guidelines to select parameters for dynamic PLAU.
Lapped unimodular transform and its factorization
(2002-11-01)
Phoong, SM
;
Lin, YP
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Two types of lapped transforms have been studied in detail in the literature, namely, the lapped orthogonal transform (LOT) and its extension, the biorthogonal lapped transform (BOLT). In this paper, we will study the lapped unimodular transform (LUT). All three transforms are first-order matrices with finite impulse response (FIR) inverses. We will show that like LOT and BOLT, all LUTs can be factorized into degree-one unimodular matrices. The factorization is both minimal and complete. We will also show that all first-order systems with FIR inverses can be minimally factorized as a cascade of degree-one LOT, BOLT, and LUT building blocks. Two examples will be given to demonstrate that despite having a very small system delay, the LUTs have a satisfactory performance in comparison with LOT and BOLT.
Optimal design of panel speaker array with omnidirectional characteristics
(2002-11-01)
Bai, MR
;
Chung, KC
;
機械工程學系
;
Department of Mechanical Engineering
A panel speaker system intended for a projection screen is developed. Like other sound sources with large dimension, the panel speaker has a beaming problem in high frequencies. To alleviate the problem, panel speakers are integrated into an array, with optimal electronic compensation for omnidirectional response and array efficiency. The heart of the design procedure is a three-stage optimization scheme involving two nonlinear and nonconvex objectives. The process is interactive, allowing the array coefficients to be tailored so that the specifications of directional response can be met. The optimal design of panel speaker array is then implemented by using a multichannel digital signal processor. In addition, a Hilbert transformer is required to produce the quadrature components of the array coefficients. A small array and a large matrix were constructed to validate the implemented array signal processing system. The experimental results indicate that, without degradation of efficiency, the proposed optimization technique in conjunction with electronic compensation is effective in attaining omnidirectional radiation property. (C) 2002 Acoustical Society of America.
A genetic algorithm for solving dual-homing cell assignment problem of the two-level wireless ATM network
(2002-11-01)
Din, DR
;
Tseng, SS
;
資訊工程學系
;
Department of Computer Science
In this paper, we investigate the optimal assignment problem, which assigns cells in Personal Communication Service to switches on Asynchronous Transfer Mode network in an optimum manner. The cost has two components: one is the cost of handoffs that involve two switches, and the other is the cost of cabling. This problem is model as dual-homing cell assignment problem, which is a complex integer programming problem. Since finding an optimal solution of this problem is NP-hard, a stochastic search method, based on a genetic approach, is proposed to solve this problem. In this paper, domain-dependent heuristics are encoded into crossover operations, mutations of genetic algorithm (GA) to solve this problem. Simulation results show that GA is robust for this problem. (C) 2002 Elsevier Science B.V. All rights reserved.
On the use of loss history for performance improvement of TCP over wireless networks
(2002-11-01)
Lee, CL
;
Liu, CF
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
Due to the fast advances in wireless networking technology, there is an increasing number of hosts using TCP/IP to connect to the Internet via wireless links. However, it is known that TCP performs poorly on paths with wireless links. This paper presents an approach to address the problem. In the proposed approach, a sender controls the size of transmitted packets and observes the number of losses for each of the controlled packet sizes. It then estimates the number of congestion losses and random losses separately. The results are used to decide whether to reduce the window size or not when a packet loss is detected. We use ns-2 simulator to evaluate the proposed approach. The simulation results show that the proposed approach is able to achieve between 25% and 150% better throughput than FACK under the byte-error rate range of 5 x 10(-5) to 20 x 10(-5).
Experience in building a real-time extension library for Java
(2002-11-01)
Chiao, HT
;
Kao, SHJ
;
Chang, YS
;
Huang, ST
;
Yuan, SM
For building real-time control programs on PC controllers, we designed and implemented a real-time extension library to enhance the Java virtual machine that was already available in the real-time operating system we used. Our extension library has the following advantages: First, the underlying Java virtual machine needs no modification to accommodate it. Second, this extension library is easily ported to any other priority-based real-time operating system. Third, the core of this extension library is basically derived from a subset of the Real-Time Specification for Java (RTSJ) standard, and thus our real-time control program can be moved to a forthcoming RTSJ-compliant Java virtual machine without much difficulty. In brief, our work may help suggest ways of implementing RTSJ, or the notion of (degrees of) "minimal" compliance/support of RTSJ based on non-RTSJ Java virtual machines. In this paper, we will show the requirement, application programming interface, and implementation of this extension library, and discuss its influence on timing.