Browsing by Issue Date, starting with "1998-12-01"

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A pilot-scale study of the design and operation parameters of a pulse-jet baghouse
(1998-12-01)
Lu, HC
;
Tsai, CJ
;
環境工程研究所
;
Institute of Environmental Engineering
Filtration curves and pulse-jet cleaning performance of different design and operating conditions of a pilot-scale pulse-jet baghouse are investigated. The effective residual pressure loss is used as an index of bag cleaning effect, while the average pulse overpressure inside the bag is used as an index of bag cleaning intensity. It is found that filtration curves vary with the initial tank pressure and the nozzle diameter of the bag cleaning system. The filtration time increases with increasing initial tank pressure or nozzle diameter. However, a critical value of the tank pressure exists for an effective bag cleaning. It is also found that a critical effective residual pressure loss value exists for the pulse-jet cleaning system. Too large an initial tank pressure and nozzle diameter result in a waste of cleaning energy. The addition of a venturi increases the average pulse overpressure appreciably, hence increasing the cleaning effect. A venturi is suggested to be installed to increase the bag cleaning effect and maximize cleaning energy in this study. (C) 1998 American Association for Aerosol Research.
Recursive wiener filter for motion parameter estimation in three-parameter motion model
(1998-12-01)
Liu, PC
;
Chang, WT
;
資訊工程學系
;
Department of Computer Science
Motion compensation is used to reduce the displaced frame difference (DFD) during the video coding. To increase the accuracy of the point correspondence during the compensation, a three-parameter motion model is considered. The matching error can be significantly reduced as compared with that of the two-parameter block matching. To derive the parameters, a partial full search method is used. The full search is used when the zoom value is set at one. Otherwise, the gradient-based algorithm is used, Since the DFD is a nonlinear function of the image gradients and the motion parameters, a linearized model is considered. To eliminate the linearization error, Wiener filtering is used to smoothen the DFD to improve the convergence condition of the iterative gradient search. To make the gradient-based search more robust to the gradient variation, several gradient estimation methods are also compared.
Frequency estimation of phase-modulated carriers
(1998-12-01)
Su, YT
;
Wu, RC
;
電信工程研究所
;
Institute of Communications Engineering
Conventional approach for frequency estimation usually assume a single tone without data modulation. In many applications such an assumption, realized by using either a separate pilot beacon or synchronization preamble is not feasible. This paper deals with frequency estimation of phase-modulated carriers in the absence of timing information and known data pattern. We introduce new frequency estimators that are based on the generalized maximum likelihood principle. The communication channels under consideration include both additive white Gaussian noise (AWGN) channels and correlated Rician fading channels. For the latter class, we distinguish between the case when the fading (amplitude) process is tracked and that when it is not tracked.
Three electrodes touch-mode capacitive pressure sensor
(1998-12-01)
Chang, KM
;
Hwang, GJ
;
Hsien, YL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A three-electrode capacitive pressure sensor for touch-mode operation with sensitivity of 0.030 pF/kPa (or 10.4 mV/kPa using CP-10 C/V converter circuit) in the pressure range of 170-280 kPa is presented with theoretical explanation of experimental results. A special ring structure is designed to integrate a sensing capacitor and a reference capacitor into the same cavity to partially cancel out the temperature effect. A third electrode is included to eliminate two-level connections without reducing its pressure sensitivity. The sensor offers the advantages of simple fabrication processes, planar connections, as well as high sensitivity, near-linear output, and large over-range pressure.
Time-constrained distributed program reliability analysis
(1998-12-01)
Chen, DJ
;
Chang, MS
;
Sheng, MC
;
Horng, MS
;
資訊科學與工程研究所
In this paper, we propose an approach to the reliability analysis of distributed programs that addresses real-time constraints. Our approach is based on a model for evaluating transmission time, which allows us to find the time needed to complete execution of the program, task, or mission under evaluation. With information on time-constraints, the corresponding Markov state space can then be defined for reliability computation. To speed up the evaluation process and reduce the size of the Markov state space, several dynamic reliability-preserving reductions are developed. A simple distributed real-time system is used as an example to illustrate the feasibility and uniqueness of the proposed approach.
Classifying and alleviating the communication overheads in matrix computations on large-scale NUMA multiprocessors
(1998-12-01)
Wang, YM
;
Wang, HH
;
Chang, RC
;
資訊工程學系
;
Department of Computer Science
Large-scale, shared-memory multiprocessors have non-uniform memory access (NUMA) costs. The high communication cost dominates the source of matrix computations' execution. Memory contention and remote memory access are two major communication overheads on large-scale NUMA multiprocessors. However, previous experiments and discussions focus either on reducing the number of remote memory accesses or on alleviating memory contention overhead. In this paper, we propose a simple but effective processor allocation policy, called rectangular processor allocation, to alleviate both overheads at the same time. The policy divides the matrix elements into a certain number of rectangular blocks, and assigns each processor to compute the results of one rectangular block. This methodology may reduce a lot of unnecessary memory accesses to the memory modules. After running many matrix computations under a realistic memory system simulator, we confirmed that at least one-fourth of the communication overhead map be reduced. Therefore, we conclude that rectangular processor allocation policy performs better than other popular policies, and that the combination of rectangular processor allocation policy with software interleaving data allocation policy is a better choice to alleviate communication overhead. (C) 1998 Elsevier Science Inc. All rights reserved.
Analysis of a partially sealed package for microstrip-line circuits
(1998-12-01)
Chen, HH
;
Chung, SJ
;
電信工程研究所
;
Institute of Communications Engineering
A partially sealed package formed by two metal diaphragms with or without an absorber is proposed and analyzed for shielded microstrip-line circuits. The mode-matching method, method of lines, and finite-element method are mixed appropriately to investigate the package. For a specific analysis, an electric current filament and a microstrip-line gap are chosen to simulate, respectively, an active circuit element (CE) and a passive CE to be packaged. The suppression effect of the package on the spurious (higher order) modes and the influence on the dominant mode are fully studied by comparing the excitation and scattering characteristics of the CE's with and without the package.
The impact of rate control algorithms on system-level VLSI design
(1998-12-01)
Cheng, SC
;
Hang, HM
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper presents an evaluation of rate control algorithms from a system-level VLSI design viewpoint. Rate control in video coding has a significant influence on the coded bit rate and image quality. Many rate control algorithms have been proposed mainly focusing on the optimal rate-distortion performance without considering their performance on the VLS implementation. The purpose of this study is not to propose a hardware architecture for any specific algorithm but to study the algorithm impact on hardware design. Based on our finding, a system designer should choose an algorithm not only good in rate control performance but also good in hardware implementation. When implementing and comparing a few rate control algorithms using a generic processor structure, we found that, in addition to the ordinary computational complexity, the internal buffer size is also very critical in VLSI realization. Several picture sequences have been tested including one sequence constructed specifically to simulate a difficult case for rate control. In this paper, three different types of popular rate control algorithms have been analyzed based on their picture quality, the internal buffer size, and the hardware cost. The methodology and results presented here provide useful guidelines for selecting an appropriate rate control algorithm for system-level VLSI designers.
A method for measuring Brewster's angle by circularly polarized heterodyne interferometry
(1998-12-01)
Lee, JY
;
Su, DC
;
光電工程學系
;
Department of Photonics
A new method for determining Brewster's angle is proposed based on the effect that the phase difference produced by a simple reflection from the test medium, for a two-frequency circularly polarized light source, is exactly equal to zero when the incident angle equals Brewster's angle. Its best resolution is 10(-3) deg and the validity of the method was demonstrated.
Finding space-optimal linear array for uniform dependence algorithms with arbitrary convex index sets
(1998-12-01)
Ke, JY
;
Tsay, JC
;
資訊工程學系
;
Department of Computer Science
The mapping of an n-dimensional uniform dependence algorithm onto a linear processor array can be considered as a linear transformation problem. However, to find a linear space-optimal transformation is difficult because the conditions for checking a correct mapping and the space cost function do not have closed-form expressions, especially when the index set J of an n-dimensional algorithm is of an arbitrary bounded convex index set. In this paper, we propose an enumeration method to find a space-optimal PE allocation vector for mapping an n-dimensional uniform dependence algorithm with an arbitrary bounded convex index set onto a linear processor array, assuming that a linear schedule is given a priori.
Bound-mode resonance improving the input matching of a dual-mode leaky guiding structure
(1998-12-01)
Lin, CC
;
Tzuang, CKC
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電信工程研究所
;
Institute of Communications Engineering
A novel approach of incorporating the bound-mode resonance in a uniform micro-CPW (coplanar waveguide) line that shows excellent input matching is presented. The matrix-pencil signal analyses of the CPW-fed micro-CPW guide confirm that two modes, namely, the bound CPW mode and the leaky second higher order microstrip mode, dominate, whereas the microstrip mode contributes too little to be detected. Both theoretical analyses and experimental measurements of the CPW-fed micro-CPW guide show that two well-matched input return losses regions are directly related to the resonances of the CPW mode within the guide.
Sputtered Cr and reactively sputtered CrNx serving as barrier layers against copper diffusion
(1998-12-01)
Chuang, JC
;
Tu, SL
;
Chen, MC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The barrier capability of sputter deposited Cr and reactively sputter deposited CrNx films against Cu diffusion in a structure of Cu/barrier/p(+)n junction diodes was investigated by means of thermal annealing at elevated temperatures in conjunction with electrical measurements and material analysis. For a 500 Angstrom thick barrier layer, the barrier capability of a pure Cr layer was limited to temperatures up to 500 degrees C, while CrNx films sputter deposited in a gas mixture of Ar and N-2 showed improved barrier capabilities. With Ar/N-2 flow rates of 24/6 to 24/12 standard cubic centimeters per minute, the deposited CrNx films possessed a much improved barrier capability. In particular, the Cu/CrNx (24/9)/p(+)n junction diodes were capable of sustaining 30 min of thermal anneal at temperatures up to 700 degrees C without degradation of the diodes' electrical characteristics. The failure of Cu/Cr/p(+)n and Cu/CrNx/p(+)n junction diodes under extreme thermal treatment was presumed to arise from two mechanisms: grain boundary diffusion for lightly nitrogen doped CrNx and pure Cr barriers, and localized defect (microcrack) diffusion for excessively nitrogen doped CrNx barriers.
Effects of ligand chain length and terminal N-alkylation on the protonation constants and stability constants of some transition metal complexes of linear tetraaza and pentaaza ligands
(1998-12-01)
Chang, CA
;
Shieh, FK
;
Liu, YL
;
Chung, CS
;
生物科技學系
A number of terminal N-alkylated linear tetraaza and pentaaza ligands were prepared. Their ligand protonation constants and some transition and post-transition metal (Ni2+, Cu2+, Zn2+, and Cd2+) complex stability constants were determined by potentiometric titration methods. In general, methylation and ethylation at the terminal nitrogen atoms caused the corresponding ligand nitrogen basicity to increase; however, the corresponding metal complex stabilities were decreased compared to the non-alkylated structural analogs, presumably due to a steric effect.
Process optimization of plasma-enhanced chemical vapor deposited passivation thin films for improving nonvolatile memory IC performance
(1998-12-01)
Lin, CF
;
Tseng, WT
;
Feng, MS
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Characteristics of plasma-enhanced chemical vapor deposited (PECVD) SiO2/SiNx passivation layers are modified to improve and optimize electrical performances such as program/erase cycle and hot carrier reliability of floating-gate nonvolatile memory devices. SiH4/N2O gas mixtures are utilized as precursors for oxide CVD process. Higher SiH4/N2O flow rate ratios render the resulting oxide films more silicon-rich, as manifested by their higher refractive index (RI) and wet etch rates. These modifications in film characteristics also correspond to increased program/erase cycles and lower % hot-carrier linear drain current (I-dlin) degradation An increase in RI from 1.520 to 1.675 translates to a rise in program/erase cycles from 17.3 K to 32 K and a fall in I-dlin from 8.2% to 4.9%. Further improvement in device performance is fulfilled by modifying the stoichiometry of the overlying nitride passivation layer. Water diffusion from oxide and hydrogen release from nitride are both responsible for hot carrier drain current degradation and loss in program/erase cycles. The utilization of a high-RI oxide in conjunction with a low hydrogen content nitride would give rise to the optimal device reliability.
Traffic control approaches for voice over ATM networks
(1998-12-01)
Chen, YC
;
Chan, CT
;
Hu, SC
;
Wang, PC
;
資訊工程學系
In this paper we present two traffic control approaches, a circuit emulation traffic control (CETC) and an adaptive priority traffic control (APTC) for supporting voice services in ATM networks. Most voice services can be handled as CBR traffic, this causes a lot of wasted bandwidth. Sending Voice through VBR(variable bit rate) may be a better alternative. because it allows the network to allocate voice bandwidth on demand. In CETC. the service discipline guarantees the quality of service (QOS) for voice circuits. Through mathematical analysis. we show that CETC features an adequate performance in delay-jitter. Moreover, it is feasible in implementation. We also present an APTC approach which uses a dynamic buffer allocation scheme to adjust the buffer size based on the real traffic need, as well as employs an adaptive priority queuing technique to handle various delay requirements for VER voice traffic. It provides an adequate QOS for voice circuits in addition to improving the multiplexing gain. Simulation results show that voice traffic get satisfied delay performance using our approaches. It may fulfill the emerging needs of voice service over ATM networks.
Aqueous tape casting of microwave ceramic BaO center dot La2O3 center dot 4.7TiO(2)
(1998-12-01)
Lee, CC
;
Lin, P
;
材料科學與工程學系
;
Department of Materials Science and Engineering
An aqueous-based slip for tape-casting BaO . La2O3. 4.7TiO(2) ceramic sheets was studied that is suitable for substrates of microwave devices. Two separate dispersants, Na4P2O7 (S2) and CH3(CH2)(4)SO3Na, combined with poly(vinyl alcohol) and poly(ethylene glycol), were used as slip additives. The zeta potential, particle size distribution, viscosity (of the slip), tensile strength and density (of green tapes), sintered density, microstructures and microwave dielectric properties (of sintered substrates) were characterized, and their dependence on the additives were analysed. S2 shows a better dispersion function and leads to a higher density of the tapes. During the sintering, the S2 liquid on grain boundaries hindered the grain growth and the formation of second phase. The dispersant-dependent microstructures of the substrates show strong influences on the dielectric properties.
An interval method for computing the structured singular value of a transfer matrix with real uncertainty
(1998-12-01)
Ge, ZM
;
Chu, LW
;
機械工程學系
;
Department of Mechanical Engineering
Singular value robustness tests can be used to analyze real parameter variations, but it is difficult to calculate the structured singular value (mu-norm) of a transfer matrix with real uncertainty. Thus far, the MATLAB (Matrix Laboratory) with mu-tools toolbox software package is the most widely used method for numerical computation of structured singular values. However, it can only obtain the lower and upper bounds of the mu-norm. We present a method developed from interval analysis which can compute the true value of the mu-norm in numerical computation.
Recycling technology of poly(ethylene terephthalate) materials
(1998-12-01)
Lin, CC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Poly(ethylene terephthalate) (PET) has become one of major post consumer plastics wastes, in addition to polyethylene (PE), polypropylene (PP), polystyrene (PS) and poly(vinyl chloride) (PVC). The challenge to large-volume plastics companies is to team how to collect, separate, reprocess and market their low-cost products and make a profit, too. The effort of. PET recycling, however, is the most successful story in the plastic recycling technology, including both reclaim and upgrade of PET waste. Beverage bottles made of PET are recycled more than 20 % of the total production. The technology of today can reclaim the postconsumer PET bottles to produce high-quality granulated PET with better than 99 % purity. A practical reclaim process for recycling PET bottles (including bottle, HDPE base cup, aluminum cap, liner, label and adhesive) is available by the Center for Plastics Recycling Research in USA. PET recycling process, like for other plastics, can be divided into three categories: incineration, physical recycling, and chemical recycling. To make the plastic recycling business pay requires more than simple recovery and marketing. Greatest profit potential is in upgraded and value-added reclaim products. Upgrading involves compounding with additives to make material more processable, adding reinforcement, or producing extrusions or finished parts from reclaim resins. For instance, a modified injection-moldable resin made from PET bottle scrap is claimed to provide high impact and processability at less cost than competitive materials. It is foreseen that chemical recycling of waste PET bottle becomes feasible if the price of raw material goes up. Three economical processes are involved in this technology: pyrolysis, hydrocracking, and hydrolysis. The hydrolysis process is presently employed to recover the raw material for unsaturated polyester resin manufacture or polyols for the production of polyurethane resin. It is reported in this presentation that polymer concrete could be a huge potential market for chemical reclaim of PET materials, especially for green or mixed-color PET, which are priced lower than colorless PET reclaim materials.
Magnetic-field dependence of the low-temperature specific heat of La2-xSrxCuO4
(1998-12-01)
Chen, SJ
;
Chang, CF
;
Tsay, HL
;
Yang, HD
;
Lin, JY
Recently, possible evidence from the low-temperature specific heat (LTSH) for the lines of nodes in the superconducting order parameter of cuprate superconductors has attracted much attention and is still debated. To clarify this issue and to cover the studies in different carrier doping regimes, we have measured LTSH of La2-xSrxCuO4 (s = 0.10, 0.16, and 0.22) both in zero and applied magnetic fields. In all doping regimes, it is found that the increase in the Linear-T coefficient gamma is proportional to H-1/2, consistent with d-wave supercon ductivity. The data shows clear evidence for an alpha T-2 term at zero magnetic field in LTSH of La1.78Sr0.22CuO4. Furthermore, our results are compared with the recently proposed scaling theory.
Magneto-luminescence of quasi-zero dimensional In0.25Ga0.75As/GaAs quantum dots
(1998-12-01)
Cheng, HH
;
Nicholas, RJ
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Priest, A
;
Tsai, FY
;
Lee, CP
We report photoluminescence measurements on In0.25Ga0.75As/GaAs quantum well and dots grown on (1 1 1)B GaAs substrate in high magnetic fields up to 45 Tesla. A well-defined PL line with full width at half maximum of approximately 5.5 meV is observed. From an analysis of the zero field transition energy, we point out the importance of an internal piezoelectric field. By analyzing the diamagnetic shift of the PL in both Faraday and Voigt configurations, the optical characteristics of a quasi-zero dimensional exciton are discussed. (C) 1998 Elsevier Science B.V. All rights reserved.