Browsing by Issue Date, starting with "2000-07-06"

Now showing 1 - 20 of 78222

Dynamic analysis of a spur gear by the dynamic stiffness method
(2000-07-06)
Huang, KJ
;
Liu, TS
;
機械工程學系
;
Department of Mechanical Engineering
This study treats a spur gear tooth as a variable cross-section Timoshenko beam to construct a dynamic model, being able to obtain transient response for spur gears of involute profiles. The dynamic responses of a single tooth and a gear pair are investigated. Firstly, polynomials are used to represent the gear blank and the tooth profile. The dynamic stiffness matrix and natural frequencies of the gear are in turn calculated. The forced response of a tooth subject to a shaft-driven transmission torque is calculated by performing modal analysis. This study takes into account time-varying stiffness and mass matrices and the gear meshing forces at moving meshing points. The forced response at arbitrary points in a gear tooth can be obtained. Calculation results of fillet stresses and strains are compared with those in the literature to verify the proposed method. (C) 2000 Academic Press.
Induced gamma -> alpha crystal transformation in blends of polyamide 6 and liquid crystalline copolyester
(2000-07-11)
Ho, JC
;
Wei, KH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The equilibrium melting temperatures and the induced gamma --> ct crystal transformation in blends of random liquid crystalline copoly(oxybenzoate-ethylene terephthalate) at molar ratio 60/40 (P64) and polyamide 6 (PA6) under different thermal treatments were investigated with differential scanning calorimetry and wide-angle X-ray diffraction, respectively. It was found that the equilibrium melting temperatures of P64/PA6 blends depended strongly on the amount of P64, and the presence of a small amount of P64 in PA6, around 5%, induced additional crystallization of the or-form crystal in the quenched PA6. Moreover, the onset temperature for the gamma --> alpha crystal transformation in the 5/95 P64/PA6 blend was reduced by 30 degrees C as compared to that in the pure PA6 case (160 degrees C vs 130 degrees C).
A possible nonpolar solvation mechanism at an intermediate time scale: the solvent-cage expansion
(2000-07-14)
Chang, SL
;
Wu, TM
;
物理研究所
;
Institute of Physics
Through studying the so-called 'epsilon' nonpolar solvation model, we propose that the expansion of the solvent cage, which is composed of the solvents at the vicinity of the first maximum of the solute-solvent radial distribution function, might be a possible solvation mechanism at a time scale between inertial motions and structural relaxation. The expansion is triggered by the strong repulsion between the solute and its neighboring solvents, originally inside the cage. This intermediate mechanism is found to be the cause for the bump following the ultrafast decay in the solvation time correlation functions of the 'epsilon' model at low densities. (C) 2000 Elsevier Science B.V. All rights reserved.
Optimal binary vote assignment for replicated data
(2000-07-15)
Chang, HK
;
Yuan, SM
;
資訊工程學系
;
Department of Computer Science
Data replication can be used to improve the availability of data in a distributed database system. In such a system, a mechanism is required to maintain the consistency of the replicated data. Weighted voting is a popular solution for maintaining the consistency. The performance of a voting system is determined by the vote assignment. It was shown in previous studies that finding the optimal solution among nonnegative integer vote assignments requires O(2(N2)) time. So it is not suitable to find the optimal integer vote assignment (OIVA) for large systems. In this paper, cue propose the optimal binary vote assignment (OBVA) considering only binary vote assignments. It is shown that OBVA can achieve nearly the same availability of OIVA. On the other hand, OBVA requires only O(N(2)) time, which is preferred for large systems. (C) 2000 Elsevier Science Inc. All rights reserved.
Efficient high-power diode-end-pumped TEM00 Nd : YVO4 laser with a planar cavity
(2000-07-15)
Chen, YF
;
Lan, YP
;
Wang, SC
;
電子物理學系
;
光電工程學系
We demonstrate a compact and efficient diode-end-pumped TEMinfinity laser with output power of 30 W for 48 W of incident pump power by use of two coated Nd:YVO4 crystals to form a thermally stabilized flat-flat cavity. In Q-switched operation 25 W of average power at a pulse-repetition rate of 100 kHz and similar to 0.9-mJ pulse energy at a pulse-repetition rate of 10 kHz were produced. (C) 2000 Optical Society of America OCIS codes: 140.3480, 140.3540.
Linear k-arboricities on trees
(2000-07-15)
Chang, GJ
;
Chen, BL
;
Fu, HL
;
Huang, KC
;
應用數學系
For a fixed positive integer k, the linear k-arboricity la(k)(G) of a graph G is the minimum number l such that the edge set E(G) can be partitioned into G disjoint sets and that each induces a subgraph whose components are paths of lengths at most k. This paper studies linear k-arboricity from an algorithmic point of view. In particular, we present a linear-time algorithm to determine whether a tree T has la(k)(T)less than or equal to m. (C) 2000 Elsevier Science B.V. All rights reserved.
Bidirectional approximate reasoning for rule-based systems using interval-valued fuzzy sets
(2000-07-16)
Chen, SM
;
Hsiao, WH
;
資訊工程學系
;
Department of Computer Science
In this paper, we extend the work of Chen et al, [Fuzzy Sets and Systems 91 (1997) 339-353] to present a new method to deal with bidirectional approximate reasoning for rule-based systems based on the direction of matching between interval-valued fuzzy sets, We also use some examples to illustrate the bidirectional approximate reasoning process. Because the proposed method can perform bidirectional approximate reasoning based on the direction of matching between interval-valued fuzzy sets, it is more reasonable and more powerful than the one presented in Chen et al., Fuzzy Sets and Systems 91 (1997) 339-353. The proposed method can provide a useful way to deal with bidirectional approximate reasoning for rule-based systems using interval-valued fuzzy sets. (C) 2000 Elsevier Science B.V, All rights reserved.
Influence of boundary conditions on pattern formation and spatial chaos in lattice systems
(2000-07-19)
Shih, CW
;
應用數學系
;
Department of Applied Mathematics
This work elucidates the spatial structure of lattice dynamical systems, which is represented by equilibria of the systems. On a finite lattice, various boundary conditions are imposed. The effect from these boundary conditions on formation of pattern as well as spatial complexity, as the lattice size tends to infinity, is investigated. Two general propositions are proposed as a criteria to demonstrate that this effect is negligible. To illustrate the effectiveness of these criteria, the mosaic patterns in a cellular neural network model on one- and two-dimensional lattices are also studied. On a one-dimensional lattice, the influence of boundary conditions on pattern formation and spatial chaos for mosaic patterns is negligible. This result is justified by verifying the above-mentioned criteria and by using the transition matrices. These appropriately formulated matrices generate all the mosaic patterns on a one-dimensional infinite lattice and on any one-dimensional finite lattice with boundary conditions. On a two-dimensional lattice, two illustrative examples demonstrate that the boundary effect can be dominant. The results and analysis in this investigation have significant implications for circuit design in cellular neural networks.
老秋
(2000-07-19)
管管
Effect of coplanar probe pad design on noise figures of 0.35 mu m MOSFETs
(2000-07-20)
Su, CY
;
Chen, LP
;
Chang, SJ
;
Huang, GW
;
Ho, YP
The effects of different coplanar ground-signal-ground (GSG) probe pads on the noise figure characteristics of submicron MOSFETs are presented. Devices with top-level metal as probe pads shielded by grounded bottom-level metal possess the most appropriate probe pad structure for characterising the noise performance of MOSFETs. Equivalent circuits of the probe pads are used to explain the different noise behaviours.
的法國梧桐不同
(2000-07-20)
管管
爾雅廿五歲隱地:再給我廿五年
(2000-07-21)
陳文芬
Oxide thinning percolation statistical model for soft breakdown in ultrathin gate oxides
(2000-07-24)
Chen, MJ
;
Kang, TK
;
Liu, CH
;
Chang, YJ
;
Fu, KY
An existing cell-based percolation model with parameter correlation can find its potential applications in assessing soft-breakdown (BD) statistics as long as the oxide thinning due to the localized physical damage near the SiO2/Si interface is accounted for. The resulting model is expressed explicitly with the critical trap number per cell n(BD) and the remaining oxide thickness t(ox)(') both as parameters. Reproduction of time-to-bimodal (soft- and hard-) breakdown statistical data from 3.3-nm-thick gate-oxide samples yields n(BD) of 3 and 4 for soft and hard breakdown, respectively. The extracted t(ox)(') of 1.0 nm for soft breakdown, plus the transition layer thickness of 0.5 nm in the model, is fairly comparable with literature values from current-voltage fitting. The dimension and area of the localized physically damaged region or percolation path (cell) are quantified as well. Based on the work, the origins of soft and hard breakdown are clarified in the following: (i) soft breakdown behaves intrinsically as hard breakdown, that is, they share the same defect (neutral trap) generation process and follow Poisson random statistics; (ii) both are independent events corresponding to different t(ox)(') requirements; and (iii) hard breakdown takes place in a certain path located differently from that for the first soft breakdown. (C) 2000 American Institute of Physics. [S0003-6951(00)02130-6].
The optimal pebbling number of the complete m-ary tree
(2000-07-28)
Fu, HL
;
Shiue, CL
;
應用數學系
;
Department of Applied Mathematics
In this paper, we find the optimal pebbling number of thr complete m-ary tree. (C) 2000 Elsevier Science B.V. All rights reserved.
The solid state C-13 NMR studies of intermolecular hydrogen bonding formation in a blend of phenolic resin and poly(hydroxyl ether) of bisphenol A
(2000-07-31)
Wu, HD
;
Ma, CCM
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Full Paper: The formation of intermolecular hydrogen bonds in blends of novolac type phenolic and poly(hydroxyl ether) of bisphenol A was investigated by studying its T-g behavior, excess volume, and solid state C-13 NMR spectra. The T-g and parameters of solid state C-13 NMR, such as the T-CH and spin-lattice relaxation time in the rotating frame T-1p(H), indicate that the London dispersion force (entropically favored) significantly affects the intermolecular hydrogen bonding of the blend. The phenoxy chain forces opening of the intra-association of phenolic and thus creates more free OHs. This strong entropic effect reduces the total hydrogen bonding of the system especially when one of the polymer is the minor component. This also results in the reduction of T-g and free volume expansion, reflecting in the increase of cross-polarization (C-H) time and molecular mobility within the phenolic/phenoxy blend.
Influence of solid content on bioleaching of heavy metals from contaminated sediment by Thiobacillus spp
(2000-08-01)
Chen, SY
;
Lin, JG
;
環境工程研究所
;
Institute of Environmental Engineering
The bioleaching process is one of the promising methods for removing heavy metals from contaminated sediments. In this study the effects of sediment solid content on the performance of the bioleaching process using a mixed culture of two sulfur-oxidizing bacteria were investigated. The results showed that the rate of pH reduction decreased with increasing sediment solid content because of the buffering capacity of sediment solids. It was found that there was a linear relationship between buffering capacity and sediment solid content. For different solid contents (10-100gdm(-3)), 82-95% (w/w) of Cu; 58-70% (w/w) of Zn; 55-73% (w/w) of Mn; 33-72% (w/w) of Pb; 35-65% (w/w) of Ni and 9-20% (w/w) of Cr were leached from sediments in this bioleaching process. The rate of metal leaching was found to decrease with an increase in sediment solid content. The solubilization of heavy metal from sediments was well described by a solid content-related kinetic equation. (C) 2000 Society of Chemical Industry.
Carrier-to-interference ratio measurement using moments or histograms
(2000-08-01)
Su, YT
;
Chen, JY
;
電信工程研究所
;
Institute of Communications Engineering
Cochannel interference is often the predominant factor that limits the capacity of a cellular mobile radio system. Power control is thus needed so that carrier-to-cochannel interference ratio (CIR) can be maintained within a tolerable bound. Many power control algorithms that require real-time CIR measurement have been proposed but there is very few mentioning of the measurement method, This paper presents viable solutions for real-time CIR estimations under various channel conditions. These solutions are based on either the method of moments or the histogram matching concept. We provide numerical results to demonstrate the usefulness and to compare the performance of the proposed algorithms. It is found that the histogram matching method with a properly-designed nonuniform quantizer offers excellent CIR estimation.
Dissociation kinetics of cerium(III) complexes of macrocyclic polyaza polycarboxylate ligands TETA and DOTA
(2000-08-01)
Chang, CA
;
Liu, YL
;
生物科技學系
;
Department of Biological Science and Technology
The acid-catalyzed dissociation rate constants of the cerium(III) complexes of 1,4,8,11-tetraazacyclotetradecane-1,4, 8,11-tetraacetic acid (TETA) and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) have been determined at four different temperatures (i.e., 25.0 degreesC, 32.0 degreesC, 39.0 degreesC, 45.0 degreesC) in aqueous media (mu = 0.10 M, HCl/KCl) to obtain additional kinetic data and to evaluate possible effects of ligand pre-organization for metal ion complexation. The rates are much faster for Ce(TETA)(-) than for Ce(DOTA)(-), indicating the lower thermodynamic stability of the former. In the presence of excess strong acid, 0.1 - 1.0 M HCl, the dissociation reactions follow the rate law: -d[ML]T/dt = (k(d) + k(H)[H+])[ML](T) and -d[ML]T/dt = (k(H)[H+] + k(H2)[H+](2))[ML](T), respectively, where k(d) is acid-independent dissociation reaction rate constant and k(H) and k(H2) are the respective dissociation rate constants for the pathways involving monoprotonated and diprotonated species. The rate activation parameters, DeltaH(not equal), DeltaS(not equal) and DeltaG(not equal), for each dissociation pathway have been obtained and their values are consistent with the proposed mechanisms. In particular, the rate difference between Ce(TETA)(-) and Ce(DOTA)(-) for the monoprotonated complex dissociation pathway is mainly due to difference in DeltaH(H)(not equal). If has been concluded that ligand pre-organization results in more stable complexes and slower complex dissociation rates.
ALTO: An iterative area/performance tradeoff algorithm for LUT-based FPGA technology mapping
(2000-08-01)
Huang, JD
;
Jou, JY
;
Shen, WZ
;
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 an iterative area/performance tradeoff algorithm for look-up table (LUT)-based held programmable gate array (FPGA) technology mapping. First, it finds an area-optimized, performance-considered initial network by a modified area optimization technique. Then, an iterative algorithm consisting of several resynthesizing techniques is applied to trade the area for the performance in the network gracefully. Experimental results show that this approach can efficiently provide a complete set of mapping solutions from the area-optimized one to the performance-optimize one for the given design. Furthermore, these two extreme solutions produced by our algorithm outperform the results provided by most existing algorithms. Therefore, our algorithm is very useful for the timing-driven, LUT-based FPGA synthesis.
Determination of the optimal dose of polyelectrolyte sludge conditioner considering particle sedimentation effects
(2000-08-01)
Wu, CC
;
Lee, DJ
;
Huang, CP
;
環境工程研究所
;
Institute of Environmental Engineering
The specific resistance to filtration (SRF) of sludge was determined using both a leaf filter and a Buncher funnel. The filterability of a kaolin suspension and an alum sludge were characterized using SRF data and capillary suction time (CST) measurements. Filter orientation during the leaf filter test and stirring during the Buncher funnel test affected the SRF values, and the optimal dosage of polyelectrolyte conditioner (defined as the dosage that yields the minimum resistance to filtration) varied depending on the type of test used. Therefore, the optimal dose of polyelectrolyte was an operationally defined value that depended on the geometry of the filter chamber and fluid/particle interactions, such as sedimentation. (C) 2000 Elsevier Science Ltd. All rights reserved.