Browsing by Issue Date, starting with "2001-03-19"

Now showing 1 - 20 of 76630

Effect of substrate concentration on bioleaching of metal-contaminated sediment
(2001-03-19)
Chen, SY
;
Lin, JG
;
環境工程研究所
;
Institute of Environmental Engineering
The remediation of metal-contaminated sediment wits studied using the bioleaching process with a mixed culture of sulfur-oxidizing bacteria. The effects of substrate concentration (elemental sulfur) on sediment acidification, sulfur oxidation and metal solubilization from contaminated sediment during the bioleaching process were investigated with free-cell suspensions. Sulfur concentration greater than 0.5% (w/v) was found to be inhibitory to bacterial activity and metal solubilization from sediment. The sulfate production was well described by a substrate inhibition expression and Haldane's equation. In addition, an empirical equation related to sulfur concentration was also used to describe the metal solubilization in the bioleaching process. (C) 2001 Elsevier Science B.V. All rights reserved.
Reactive compatibilization of PP/PBT blends by a mixture of PP-g-MA and epoxy resin
(2001-03-21)
Shieh, YT
;
Liao, TN
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
In this study, dual compatibilizers composed of the commercially available maleic anhydride-grafted polypropylene (PP-MA) and a multifunctional epoxy resin were demonstrated to effectively compatibilize the immiscible and incompatible blends of PP and poly(butylene terephthalate) (PBT). The PP-MA with a low MA content is totally miscible with PP to make the PP phase quasi-functionalized, so that the multifunctional epoxy has the chance to react with PBT and PP-MA simultaneously to form PP-MA-co-epoxy-co-PBT copolymers at the interface. These desired copolymers are able to anchor along the interface and serve as efficient compatibilizers. The compatibilized blends, depending on the quantity of dual compatibilizers employed, exhibit higher viscosity, finer phase domain, and improved mechanical properties. Epoxy does not show compatibilization effects for the PP/PBT blends without the presence of PP-MA in the blends. (C) 2001 John Wiley & Sons, Inc.
Disproving a conjecture on planar visibility graphs
(2001-03-28)
Chen, CY
;
Wu, KP
;
應用數學系
;
Department of Applied Mathematics
Two vertices A and B of a simple polygon P are (mutually) visible if AB does not intersect the exterior of P. A graph G is a visibility graph if there exists a simple polygon P such that each vertex of G corresponds to a vertex of P and two vertices of G are joined by an edge if and only if their corresponding vertices in P are visible, No characterization of visibility graphs is available. Abello, Lin and Pisupati conjectured that every hamiltonian maximal planar graph with a 3-clique ordering is a visibility graph. In this paper, we disprove this conjecture. (C) 2001 Elsevier Science B.V. All rights reserved.
Structural identification from ambient vibration measurement using the multivariate AR model
(2001-03-29)
Huang, CS
;
土木工程學系
;
Department of Civil Engineering
A procedure for identifying the dynamic characteristics of a structural system using the multivariate AR (ARV) model is presented in the paper. A least-squares approach to determine the coefficient matrices of the ARV model is proposed, which is a modification of the traditional one. The modification is based on the equivalence between the correlation function matrix for the responses of a linear system subjected to white-noise input and the deterministic free vibration responses of the system. Then, the dynamic characteristics of the system are evaluated directly from the coefficient matrices of the ARV model by adopting the concept behind Ibrahim's system identification technique. The superiority of the proposed procedure over the traditional one is demonstrated through numerical studies on a six-story shear building. Finally, the present identification procedure is applied to identify the dynamic characteristics of a three-span highway bridge from its ambient vibration responses subjected to traffic flow. The validity of the present procedure is confirmed by the excellent agreement between the identified results obtained in the present study and those obtained from an impulse test. (C) 2001 Academic Press.
Origin of size effect on superconductivity in (R-0.8 Pr-0.2)Ba2Cu3O7 studied by soft X-ray absorption spectroscopy
(2001-03-30)
Chen, JM
;
Nachimuthu, P
;
Lin, JY
;
Hong, IP
;
Chang, CF
O K-edge X-ray absorption near-edge structure (XANES) spectroscopy of (R-0.8 Pr-0.2)Ba2Cu3O7 (R = Y, Tm, Dy, Gd, Eu and Sm) has been performed to investigate the dependence of hole distribution on ionic size of the R3+ ions. Near the O Is absorption edge, pre-peaks at similar to 527.8 and similar to 528.5 eV are assigned to transitions into O 2p hole states located in the CuO3 ribbons and CuO2 planes, respectively. As deduced from O K-edge X-ray absorption spectra, the hole concentrations in the CuO2 planes decrease monotonically with increasing ionic size of the rare-earth elements. The present XANES results clearly demonstrate that the suppression of superconductivity in (R1-x Pr-x)Ba2Cu3O7 With ionic radius of the R3+ ions results predominantly from the hole-depletion effect. (C) 2001 Elsevier Science B.V. All rights reserved.
Exact Green function of Aharonov-Bhm billiard system
(2001-03-30)
Chuu, DS
;
Lin, DH
;
電子物理學系
;
Department of Electrophysics
The exact Green functions of the relativistic spherical quantum Aharonov-Bohm billiard systems in two- and three-dimensional spaces are given by the path integral approach. The transcendental equations for determining the energy spectra are discussed.
Discrepancies between different response parameters in batch and continuous algal toxicity tests
(2001-03-30)
Chao, MR
;
Chen, CY
;
環境工程研究所
;
Institute of Environmental Engineering
The test sensitivities and reproducibilities based on different response endpoints (cell density and total cell volume) were compared using both bath and continuous algal toxicity tests. Parameters related to algal cell density are found to be more sensitive and reproducible than total cell volume which bears a direct correlation to algal biomass or dry weight. The magnitude of differences in the median effective concentration values could be upto six folds. The main cause for the above discrepancies is because the cell density and total cell volume are two response endpoints reflecting the degree of inhibition on the binary fission mechanism and overall photosynthesis, respectively. At low toxicant concentrations, the inhibitory effect is primarily on the cell division rather than on the cellular photosynthesis. Thus, more severe toxic effects are expected to be observed based on the cell density than the total cell volume. The results of this study clearly demonstrate that sensitivity and reproducibility can be significantly improved if response parameters are calculated based on the cell density. Traditionally, cell density data are often converted into biomass before assessing the effects of toxicants. This procedure may not be necessary and may reduce the test sensitivity. (C) 2001 Elsevier Science B.V. All rights reserved.
Luminescence intensity reduction in Mg-doped GaN grown by metalorganic chemical vapor phase epitaxy
(2001-04-01)
Shu, CK
;
Chen, HH
;
Lee, WH
;
Pan, YC
;
Huang, HY
Photoluminescence dynamic responses of a heavily Mg-doped GaN grown by metalorganic chemical vapor phase epitaxy have been investigated. As the probe power density increased from 2.5 to 925 W/cm(2), a Mg-related emission band shifted from 2.82 to 3.16 eV revealing characteristics of donor-acceptor pair recombination. The intensity evolution also showed slow decay that suggests the metastable emission behavior. A simple potential barrier model was proposed to occur between the Mg related deep levels and common Mg acceptor level, which impedes electron relaxation and thus slows down the luminescence decay. From the variation of decay time constant with temperature. a barrier energy was deduced to be about 69 meV which is very close to the electrical result of 68 meV.
Numerical and experimental study of internal flow field for a carbon fiber tow pneumatic spreader
(2001-04-01)
Chen, JC
;
Chao, CG
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In this study, a three-dimensional (3-D) mathematical model of a fiber pneumatic spreader was successfully developed in the physical phenomena of the internal flow field by a far-field treatment at boundary conditions. The 3-D numerical analysis was carried out on incompressible fluid flows in the pneumatic spreader by using finite volume method combined with the k-epsilon turbulence model which solves Reynolds-averaged Naiver-Stokes equations. Characteristics of the flow field in the spreader at different service conditions are investigated by velocity and pressure distributions. Comparisons of numerical results with measured velocity and pressure distributions were made to determine the accuracy of the employed method. A good agreement was found in both qualitative and quantitative analysis. Fibers were spread on 1:1-scale model of the pneumatic spreader at various fiber transporting rates and air flow rates. Photography techniques were simultaneously used to record the procedures of fibers spread. The carbon fiber tow was easily spread out at service conditions. The performance was better than prior studies in one-dimensional orifice formulation. The results revealed details of the fiber spreading processes. Agreement among those results validated the assumptions inherent to the computational calculation and gave confidence to more complex geometries as well as flow fields. In other words, the use of numerical analysis in the internal flow field was useful for the fiber pneumatic spreader design.
Possibilistic programming in production planning of assemble-to-order environments
(2001-04-01)
Hsu, HM
;
Wang, WP
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
For the sake of alleviating the influences of demand uncertainty in assemble-to-order (ATO) environments, the strategies of regulating dealers' forecast demands, determining appropriate safety stocks, and deciding the numbers of key machines are usually adopted by manufacturers. In this paper, we propose a possibility linear programming model to manage these production planning problems. The proposed model accomplishes forecasting adjustments, material management, and production activities. Because of price fluctuations, material obsolescence, and the time value of, capital. the ambiguity of cost is considered in the objective function of the model. We substituted the fuzzy objective function with three crisp objectives: minimizing the most possible cost, maximizing the possibility of obtaining lower cost, and minimizing the risk of obtaining higher cost. Zimmermann's fuzzy programming method is then applied for achieving an overall satisfactory compromise solution. Finally, an example is given to illustrate our model. (C) 2001 Elsevier Science B.V. All rights reserved.
Integration of thin film transistor controlled carbon nanotubes for field emission devices
(2001-04-01)
Cheng, HC
;
Hong, WK
;
Tarntair, FG
;
Chen, KJ
;
Lin, JB
A new field emission device composed of carbon nanotubes and a thin film transistor (TFT) has been successfully demonstrated to significantly improve emission stability. Carbon nanotubes are directly integrated in the drain region of the TFT and the emission current from the carbon nanotubes is controlled via the TFT drain current. The fluctuation of the emission current of the TFT-controlled carbon nanotubes can be suppressed to less than 2%, below the fluctuation of uncontrolled carbon nanotubes. The novel field emission device exhibits low-voltage controllability, good emission stability, and structural simplicity, making it promising for application to future field-emission display. (C) 2001 The Electrochemical Society.
A framework for temporal similarity measures of content-based scene retrieval
(2001-04-01)
Shan, MK
;
Lee, SY
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
The distinguished features of video retrieval lie in the similarity measures and content-based retrieval. Most research on content-based video retrieval represents the content of video as a set of frames, leaving out the temporal ordering of frames in the shot. In this paper, the similarity measures of video content are investigated. We propose a series of similarity measures based on the similarity of frame sequence which take temporal ordering into consideration. All the algorithms corresponding to the similarity measures are based on the approach of dynamic programming. (C) 2001 Published by Elsevier Science B.V.
Ordered lookup with bypass matching for scalable per-flow classification in layer 4 routers
(2001-04-01)
Lin, YD
;
Wei, HY
;
Wu, KJ
;
資訊工程學系
;
Department of Computer Science
In order to provide different service treatments to individual or aggregated hows, layer 4 routers in Integrated Services networks need to classify packets into different queues. The classification module of layer 4 routers must be fast enough to support gigabit links at a rate of millions of packets per second. In this work, we present a new software method OLBM to lookup multiple fields of a packet, in a dynamically pre-defined order, against the classification database. This algorithm also uses a technique called bypass matching and can classify packets at a rate of well over one million packets per second while scaling to support more than 300k flows. Complexity analysis and experiment measurements are also presented in this study. (C) 2001 Elsevier Science B.V. All rights reserved.
On-chip ESD protection design by using polysilicon diodes in CMOS process
(2001-04-01)
Ker, MD
;
Chen, TY
;
Wang, TH
;
Wu, CY
;
電子工程學系及電子研究所
A novel on-chip electrostatic discharge (ESD) protection design by using polysilicon diodes as the ESD clamp devices in CMOS process is first proposed in this paper, Different process splits have been experimentally evaluated to find the suitable doping concentration for optimizing the polysilicon diodes for both on-chip ESD protection design and the application requirements of the smart-card ICs. The secondary breakdown current (It2) of the polysilicon diodes under the forward- and reverse-bias conditions has been measured by the transmission-line-pulse (TLP) generator to investigate its ESD robustness, Moreover, by adding an efficient VDD-to-VSS clamp circuit into the IC, the human-body-model (HBM) ESD robustness of the IC with polysilicon diodes as the ESD clamp devices has been successfully improved from the original similar to 300 V to become greater than or equal to3 kV, This design has been practically applied in a mass-production smart-card IC.
Analysis and DSP implementation of a broadband duct ANC system using spatially feedforward structure
(2001-04-01)
Bai, MR
;
Lin, YJ
;
機械工程學系
;
Department of Mechanical Engineering
The active control technique for broadband attenuation of noise in ducts, using spatially feedfoward structure. is investigated from the viewpoints of both acoustic analysis and exists an ideal controller for this problem. The ideal controller is a function of the finite control engineering. According to the previous work by Munjal and Eriksson [1], there source impedance and is thus independent of the boundary conditions. Despite the simplicity the ideal controller cannot be practically implemented due to the difficulty of calibration of electro-mechanical parameters. To overcome the problem, the controller is implemented via an equivalent formulation modified from the controller originally proposed by Roure [2]. The modified controller is implemented on a DSP platform, using a FIR filter, an IIR filter and a hybrid filter. The experimental results showed that the system achieved 17.2 dB maximal attenuation in the frequency band 300 similar to 600 Hz. Physical insights and design considerations in implementation phase are also discussed in the paper.
A beamspace-time blind RAKE receiver for sectored CDMA systems
(2001-04-01)
Lee, TS
;
Tsai, TC
;
Chen, CH
;
電信工程研究所
;
友訊交大聯合研發中心
A beamspace-time (BT) RAKE receiver is proposed for multiple access interference (MAT) suppression and multipath diversity reception in sectored wireless CDMA communications. The scheme involves three stages. First, a set of adaptive beamformers encompassing a prescribed angular sector is constructed on an antenna array, each providing effective suppression of out-of-sector MAI and reception of in-sector signal. Second, a set of adaptive correlators is attached to each beam to combat in-sector MAI. Finally, the beamspace correlator output data are combined to capture the signal multipaths coherently. The above three-stage operation is performed in a blind mode in that no training signal is needed. The only information required is the signature, timing and a rough estimate of the angle of arrival (AOA) of the desired signal.
Analysis and design of large leaky-mode array employing the coupled-mode approach
(2001-04-01)
Hu, CN
;
Tzuang, CKC
;
電信工程研究所
;
Institute of Communications Engineering
This paper presents the coupled-mode approach to the analysis and design of a large leaky-mode array, in which an N-element microstrip array above a common ground plane supports N coupled leaky modes (leaky EH1 modes) at the first higher order, Following a brief description of a conventional full-wave nonstandard eigenvalue problem for solving the complex propagation constants, we present the detailed formulation of the coupled-mode approach, clearly showing the transformation of the nonstandard eigenvalue problem into a standard one. Thus, all the eigenvalues (complex propagation constants) and eigenvectors (modal current distributions) are solved simultaneously, regardless of the size of the array (N). Two key issues pertinent to the successful implementation of the proposed coupled-mode approach are addressed: the determination of the coupling coefficients and the uniqueness of the isolated uncoupled leaky mode, which represents the leaky modal solution of a single microstrip, but is derived from a system of coupled leaky-mode solutions provided the coupled microstrips have equal width and spacing, Closed-form expressions for obtaining the coupling coefficients of orders two, three, and four are presented. Theoretical studies of closely coupled microstrip arrays of two, three, and four elements show that the magnitude of the coupling coefficient C-i,C-i+j between elements i and i + j decreases at the order of 10(-j). These theoretical case studies also lead to the same isolated uncoupled leaky-mode solution as predicted. Furthermore, the dispersion characteristics of the microstrip array at the first higher order obtained by the coupled-mode approach and the full-wave approach agree excellently for all the case studies, Error analyses indicated that at least two coupling coefficients (C-i,C-i+1 and C-i,C-i+2) are required for obtaining accurate complex propagation constants with rms errors less than 1% for most of the leaky region of the particular array under investigation. An example of applying the proposed coupled-mode approach for analyzing a corporate-fed leaky-mode array of eight elements is reported, revealing that only four out of the eight leaky modes are excited. The coupled-mode theory predicts the far-field radiation pattern in the main beam region in excellent agreement with the measured results.
Low cost CMOS on-chip and remote temperature sensors
(2001-04-01)
Weng, MC
;
Wu, JC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper describes the design and results of low cost integrated CMOS local and remote temperature sensors with digital outputs. No trimming is needed to obtain good temperature linearity, so that only one-temperature calibration is needed which greatly reduces testing cost. The base-emitter voltage of the parasitic substrate bipolar transistor is used to measure the local temperature. A diode-connected external bipolar transistor is used to measure the remote temperature. Chopper techniques were used to cancel the offset voltage of the op-amp, so that a precise bandgap voltage call be obtained without resistance trimming. A first order Sigma Delta ADC was used to produce the digital output. The local and remote temperature sensors were realized in a 0.6 mu cm single-poly triple-metal CMOS technology with active area of 0.61 nm(2) and 0.65 mm(2), respectively. After calibration, the error is +/-1 degreesC for the local temperature sensor over the temperature range of -20 to 130 degreesC, and +/-2 degreesC for tile remote temperature sensor over the range of 0 to 120 degreesC. The supply currents of tile local and remote temperature sensors are 3.5 muA and 38 muA at 8 samples/s, respectively.
Approaches to tacamonine.
(2001-04-01)
Ho, TL
;
Su, CY
;
Gorobets, E
;
應用化學系
;
Department of Applied Chemistry
Sidelobe suppression of spectral response in holographic optical filter
(2001-04-01)
Zajtsev, AK
;
Lin, SH
;
Hsu, KY
;
電子物理學系
;
光電工程學系
In order to suppress sidelobes of holographic filter's spectral response we propose to use weighting of grating intensity distribution along light propagation. This can be realized in photorefractive material (for example in LiNbO3:Fe) by using spatial selective decaying of conventional uniform grating by illumination of light through some transparent mask. Experimental results show that it is able to obtain 8 dB improvement of sidelobe level compared to uniform grating. But it is accompanied by 1.7 times expansion of main lobe and two times decrease of diffraction efficiency. (C) 2001 Elsevier Science B.V. All rights reserved.