Browsing by Issue Date, starting with "2001-07-04"

Now showing 1 - 20 of 76387

Computer-aided manufacturing of spiral bevel and hypoid gears by applying optimization techniques
(2001-07-04)
Lin, CY
;
Tsay, CB
;
Fong, ZH
;
機械工程學系
;
Department of Mechanical Engineering
A mathematical model of an ideal spiral bevel and hypoid gear-tooth surfaces based on the GIeason hypoid gear generator mechanism is proposed. Using the proposed mathematical model, the tooth surface sensitivity matrix to the variations in machine-tool settings is investigated. Surface deviations of a real cut pinion and gear with respect to the theoretical tooth surfaces are also investigated. An optimization procedure for finding corrective machine-tool settings is then proposed to minimize surface deviations of real cut pinion and gear-tooth surfaces. The results reveal that surface deviations of real cut gear-tooth surfaces with respect to the ideal ones can be reduced to only a few microns. Therefore, the proposed method for obtaining corrective machine-tool settings can improve the conventional development process and can also be applied to different manufacturing machines and methods for spiral bevel and hypoid gear generation. An example is presented to demonstrate the application of the proposed optimization model. (C) 2001 Elsevier Science B.V. All rights reserved.
Density functional study of the relative reactivity in the concerted 1,3-dipolar cycloaddition of nitrile ylide to disubstituted ethylenes
(2001-07-05)
Liao, HY
;
Su, MD
;
Chung, WS
;
Chu, SY
;
應用化學系
Density functional theory was used to perform a theoretical evaluation of (E)-1,2-disubstituted ethylenes as dipolarophiles for the 1,3-dipolar cycloaddition reaction. The reactivities of electron-withdrawing and -donating substituted ethylenes were examined by estimating their activation energies. The calculated activation energies predicted that the most reactive species is (E)-1,2-C2H2(NO)(2), whereas the least reactive is (E)-2-butene. Namely, it was demonstrated that 16-electron 1,3-dipole reactants with more electropositive substituents in terminal positions and ethylenes that possess more strongly electron-withdrawing substituents facilitate 1,3-dipolar cycloaddition reactions. All of the theoretical results can be rationalized using the configuration mixing model. (C) 2001 John Wiley & Sons, Inc.
Hyperbranched aromatic poly(ether imide)s: Synthesis, characterization, and modification
(2001-07-15)
Wu, FI
;
Shu, CF
;
應用化學系
;
Department of Applied Chemistry
The synthesis and characterization of hyperbranched aromatic poly(ether imide)s are described. An AB, monomer, which contained a pair of phenolic groups and an aryl fluoro moiety activated toward displacement by the attached imide heterocyclic ring, was prepared. The nucleophilic substitution of the fluoride with the phenolate groups led to the formation of an ether linkage and, subsequently, to the hyperbranched poly(ether imide), which contained terminal phenolic groups. A similar one-step polymerization involving a monomer that contained silyl-protected phenols yielded a hyperbranched poly(ether imide) with terminal silylated phenols. The degree of branching of these hyperbranched polymers was approximately 55%, as determined by a combination of model compound studies and H-1 NMR integration experiments. End-capping reactions of the terminal phenolic groups were readily accomplished with a variety of acid chlorides and acid anhydrides. The nature of the chain-end groups significantly influenced physical properties, such as the glass-transition temperature and the solubility of the hyperbranched poly(ether imide)s. As the length of the acyl chain of the terminal ester groups increased, the glass-transition temperature value for the polymer decreased, and the solubility of the polymer in polar solvents was reduced, becoming more soluble in nonpolar solvents. (C) 2001 John Wiley & Sons, Inc.
Studies of miscibility behavior and hydrogen bonding in blends of poly(vinylphenol) and poly(vinylpyrrolidone)
(2001-07-17)
Kuo, SW
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Polymer blends of poly(vinylphenol) (PVPh) with poly(vinylpyrrolidone) (PVP) were prepared by solution casting from the N,N-dimethylformamide (DMF) solution. Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and solid-state nuclear magnetic resonance (NMR) were used to investigate the hydrogen bonding and miscibility behavior of the blend. This PVPh/PVP blend system has a single glass transition temperature over the entire composition range, indicating that this blend is able to form a miscible phase due to the formation of inter-hydrogen bonding between the hydroxyl of PVPh and the carbonyl of PVP. Furthermore, FTIR and solid-state NMR were used to study the hydrogen-bonding interaction between the PVPh hydroxyl group and the PVP carbonyl group at various compositions. According to the Painter-Coleman association model (PCAM), the interassociation constant for the PVPh/PVP blend is significantly higher than the self-association constant of PVPh, revealing that the tendency toward hydrogen bonding of the PVPh and PVP dominates the intra-hydrogen bonding of the PVPh in the mixture.
Polygon building block route to sp(2)-carbon-based materials
(2001-07-18)
Lee, CY
;
Chiu, HT
;
Peng, CW
;
Yen, MY
;
Chang, YH
Pentagonal- and hexogonal-shaped building block precursors provide a novel, high-yield method for the preparation of carbon onions and nanosized graphite particles. A reaction of hexachlorocyclopentadiene (C5Cl6) with sodium (see Figure) offers carbon onions with 8-50 spherical and elliptical shells. The same reaction with hexachlorobenzene (C6Cl6) results in a mixture of graphite crystallites. [GRAPHICS]
Stretch-wire system for integral magnetic field measurements
(2001-07-21)
Hwang, CS
;
Hong, CH
;
Lin, FY
;
Yang, SL
;
電子物理學系
A stretch-wire system was developed to measure and characterize the first and second magnetic fields integral of insertion devices and the harmonic field components of lattice magnet. This simple wire support structure was built with a reliable high precision, and high-speed automatic measurement system for measuring the transversal field integrals of various kind magnets. The measurement precision of the system is 1.5 G cm (70 G cm(2)) for the first (second) field integral of the insertion devices and 0.01% for the harmonic field components analysis of the lattice magnets. The scanning time for a complete measurement is five minutes for the first and second field integral distribution, and four minutes for the harmonic field components. (C) 2001 Elsevier Science B.V. All rights reserved.
Luminescent mechanisms of ZnS : Cu : Cl and ZnS : Cu : Al phosphors
(2001-07-23)
Chen, YY
;
Duh, JG
;
Chiou, BS
;
Peng, CG
;
電子工程學系及電子研究所
ZnS:Cu:Cl and ZnS:Cu:Al phosphors are fabricated by a flux fusion method to be used in cathode ray tube (CRT) monitors for green emission. The emission spectra of the phosphors depend on the Cu concentration. A series of luminescence measurements have been conducted, and several models are applied to explain the luminescent phenomenon of these phosphors. It is revealed that ZnS:Cu:Cl and the ZnS:Cu:Al phosphors exhibit green emission yet their luminescence mechanisms are different. The emission spectrum from the as-fabricated green phosphors is not a typical Gaussian distribution. The combination of blue and green band luminescence is attributed to the green-luminescence quenching derived from the interstitial Cu+ ions. (C) 2001 Elsevier Science B.V. All rights reserved.
Channel graphs of bit permutation networks
(2001-07-28)
Tong, LD
;
Wang, FK
;
Chang, GJ
;
應用數學系
;
Department of Applied Mathematics
Channel graphs have been widely used in the study of blocking networks. In this paper, we show that a bit pen-nutation network has a unique channel graph if and only if it is connected, and two connected bit pen-nutation networks are isomorphic if and only if their channel graphs are isomorphic. (C) 2001 Elsevier Science B.V. All rights reserved.
A complementary survey on double-loop networks
(2001-07-28)
Hwang, FK
;
應用數學系
;
Department of Applied Mathematics
We give a survey on double-loop networks with emphasis on new development since the surveys in 1986, 1991 and 1995. (C) 2001 Elsevier Science B.V. All rights reserved.
Weighted connected k-domination and weighted k-dominating clique in distance-hereditary graphs
(2001-07-28)
Yeh, HG
;
Chang, GJ
;
應用數學系
;
Department of Applied Mathematics
A graph is distance-hereditary if the distance between any two vertices in a connected induced subgraph is the same as in the original graph. This paper presents efficient algorithms for solving the weighted connected k-domination and the weighted k-dominating clique problems in distance-hereditary graphs, (C) 2001 Elsevier Science B.V. All rights reserved.
Conduction mechanisms for off-state leakage current of Schottky barrier thin-film transistors
(2001-07-30)
Yeh, KL
;
Lin, HC
;
Huang, RG
;
Tsai, RW
;
Huang, TY
Conduction mechanisms for the off-state leakage in Schottky barrier thin-film transistor were explored. It was found that the field-emission process dominates the leakage conduction of the device with the conventional structure as the field strength in the drain junction becomes high, and results in the strong gate-induced drain leakage (GIDL) like phenomenon. In contrast, for the device with a field-induced-drain structure, the high-field region is pulled away from the silicided drain. As a result, the field-emission conduction is eliminated, so the GIDL-like leakage current is effectively suppressed. (C) 2001 American Institute of Physics.
管管作品四首
(2001-08-01)
管管
Thermal-treatment induced deep electron traps in AlInP
(2001-08-01)
Sung, WJ
;
Huang, KF
;
Lin, WJ
;
Tseng, TY
;
電子物理學系
The effects of thermal treatment on the quality of AlInP film, grown by metal-organic chemical vapor deposition (MOCVD), have been carefully investigated using deep level transient spectroscopy (DLTS). Two thermal-treatment-induced deep levels were observed in the samples thermal-treated above 500 degreesC and shall be attributed to the generation of phosphorus vacancies (V-p) by evaporation of phosphorus from AlInP surface. Examination of these deep levels provided a relatively simple means of understanding the thermal-treatment-induced behavior, thus allowing us to determine an appropriate process for manufacturing AlInP-based products.
劍橋之柳(外一首)
(2001-08-01)
管管
Visualization of roll patterns in Rayleigh-Benard convection of air in a rectangular shallow cavity
(2001-08-01)
Lir, JT
;
Lin, TF
;
機械工程學系
;
Department of Mechanical Engineering
Flow visualization is conducted here to study the vortex flow patterns associated with the Rayleigh-Benard convection in a horizontal shallow cavity of air. The cavity is a rectangular enclosure characterized by the aspect ratios A(x) = 16 and A(z) = 20. Attention is focused on the convection rolls driven at slightly supercritical and subcritical buoyancies. The results show that at slightly subcritical Ra the induced vortex flow is in the form of rectangular rolls along the cavity sides and short straight parallel rolls in the cavity core. At slightly higher Ra near Ra-c proportional to (= 1708) more rectangular rolls appear and the short straight rolls in the cavity core merge together to form a serpentine roll. At slightly supercritical buoyancy with 2000 less than or equal to Ra less than or equal to 3000 the entire cavity is filled with the straight rolls all parallel to the short sides of the cavity. At an even higher Ra of 4000 the vortex rolls become irregular and time dependent. Moreover, the processes through which various vortex flow structures evolve during the transient stage are shown to be rather complicate and the vortex flow patterns during the how formation are significantly affected by the heating rate in raising the buoyancy force. Furthermore, the wavenumber reduction at higher Ra for the parallel vortex roll pattern was noted to mainly result from the splitting of some rectangular rolls into cells and the subsequent merging of the cells into bigger rolls at the intermediate stage of the flow formation. (C) 2001 Elsevier Science Ltd. All rights reserved.
管管作品四首
(2001-08-01)
管管
劍橋之柳(外一首)
(2001-08-01)
管管
Improved low temperature characteristics of p-channel MOSFETs with Si1-xGex raised source and drain
(2001-08-01)
Huang, HJ
;
Chen, KM
;
Huang, TY
;
Chao, TS
;
Huang, GW
P-channel metal-oxide-semiconductor field-effect transistors with Si1-xGex raised source and drain (RSD) have been fabricated and further studied for low temperature applications. The Si1-xGex RSD layer was selectively grown by ANELVA. SRE-612 ultra-high vacuum chemical vapor deposition (UHVCVD) system, Compared to devices with conventional Si RSD, improved transconductance and specific contact resistance were obtained, and these improvements become even more dramatic with reducing channel length, Well-behaved short channel characteristics with reduced drain-induced barrier lowering (DIBL) and off-state leakage current are demonstrated on devices with 100 nm Si1-xGex RSD, due to the resultant shallow junction and less implantation damage. Moreover, temperature measurements reveal that Si1-xGex RSD devices show more dramatic improvement in device performance at low temperature (-50 degreesC) operation, which can be ascribed to the higher temperature sensitivity of the Si1-xGex sheet resistance.
管管作品四首
(2001-08-01)
管管
The enhancement of nitrogen incorporation in RTN2O annealed TEOS oxide fabricated on disilane-based polysilicon films
(2001-08-01)
Lee, JW
;
Chen, WD
;
Lei, TF
;
Lee, CL
;
電子工程學系及電子研究所
Disilane-based stacked structures were first proposed to demonstrate that the nitrogen incorporation was enhanced in the RTN2O annealed tetraethylorthosilicate (TEOS) oxide fabricated on disilane-based polysilicon films. Compared with the oxide fabricated on the silane-based polysilicon film, the nitrogen incorporation in the disilane-based oxides is six times higher. To study the nitrogen incorporation effects on the RTN2O annealed TEOS oxides, the disilane-based polysilicon stacked on the silane-based polysilicon film structure was proposed. We found that the oxide quality was largely improved by the same surface morphology of bottom polysilicon films. We think the this approach could be used in fabricating dynamic random access memory (DRAM) to have better data retention characteristics and to improve the reliability of DRAM and flash memory devices. (C) 2001 The Electrochemical Society. [DOI: 10.1149/1.1383554] All rights reserved.