Browsing by Issue Date, starting with "2006-01-03"

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A modified transfer matrix method for the coupling lateral and torsional vibrations of symmetric rotor-bearing systems
(2006-01-03)
Hsieh, SC
;
Chen, JH
;
Lee, AC
;
機械工程學系
;
Department of Mechanical Engineering
This study develops a modified transfer matrix method for analyzing the coupling lateral and torsional vibrations of the symmetric rotor-bearing system with an external torque. Euler's angles are used to describe the orientations of the shaft element and disk. Additionally, to enhance accuracy, the symmetric rotating shaft is modeled by the Timoshenko beam and considered using a continuous-system concept rather than the conventional "lumped system" concept. Moreover, the harmonic balance method is adopted in this approach to determine the steady-state responses comprising the synchronous and superharmonic whirls. According to our analysis, when the unbalance force and the torque with nx frequency of the rotating speed excite the system simultaneously, the (n + 1) x and (n - 1) x whirls appear along with the synchronous whirl. Finally, several numerical examples are presented to demonstrate the applicability of this approach. (c) 2005 Elsevier Ltd. All rights reserved.
Memory effect of sol-gel derived V-doped SrZrO3 thin films
(2006-01-03)
Liu, CY
;
Chuang, CC
;
Chen, JS
;
Wang, A
;
Jang, WY
V-doped SrZrO3 (SZO) thin films on LaNiO3/SiO2/Si substrate are synthesized by sol-gel method to form metal-insulator-metal (MIM) sandwich structure. The physical and electrical properties of the MIM device are studied. The structure and surface morphology of the SZO films are also characterized by X-ray diffraction and scanning electron microscopy. Such a device has the bistable switching properties of current-voltage characteristics. The resistive switching between high state and low state can also be operated with voltage pulses. The device with the properties of long retention time and non-destructive readout is expected to be suitable for nonvolatile memory application. (c) 2005 Elsevier B.V. All rights reserved.
Reaction growth of MF2/a-C (M = Ca, Mg) core/shell nanowires at the interface of vapor and solid reactants
(2006-01-03)
Huang, CH
;
Chang, YH
;
Lee, CY
;
Chiu, HT
;
應用化學系
C6F6 vapor is employed to react with CaC2 and Mg3N2 to grow CaF2/a-C and Mg2F2/a-C core/shell nanowires (tens of micrometers in length, tens to hundreds of nanometers in wire diameter, and tens of nanometers in core diameter), respectively, in high yields. The growth mechanism is proposed to proceed via a reaction at the interface of the vapor and solid reactants.
Photocurrent amplification at carbon nanotube-metal contacts
(2006-01-05)
Lien, DH
;
Hsu, WK
;
Zan, HW
;
Tai, NH
;
Tsai, CH
Infrared microscopy of hot spots induced by Joule heating in flip-chip SnAg solder joints under accelerated electromigration
(2006-01-09)
Chiu, SH
;
Shao, TL
;
Chen, C
;
Yao, DJ
;
Hsu, CY
Joule heating effect in solder joints was investigated using thermal infrared microscopy and modeling in this study. With the increase of applied current, the temperature increased rapidly due to Joule heating. Furthermore, modeling results indicated that a hot spot existed in the solder near the entrance point of the Al trace, and it became more pronounced as the applied current increased. The temperature difference between the hot spot and the solder was as large as 9.4 degrees C when the solder joint was powered by 0.8 A. This hot spot may play an important role in the initial void formation during electromigration.
Giant anisotropy of carrier mobility in electroluminescent conjugated polymer
(2006-01-09)
Meng, HF
;
Chen, BL
;
Tzeng, KC
;
Horng, SF
;
物理研究所
The horizontal and vertical hole mobility of amorphous spin-coated electroluminescent conjugated films are studied. It is found that the horizontal mobility is about four orders of magnitude larger than the vertical mobility. The horizontal mobility increases daily with the aging of the polymer solution from which the film is spun. Low temperature and photoluminescence study reveal that the giant mobility anisotropy is a result of the alignment of the aggregates, formed during aging, by the centrifugal force of the spin.
Local structural effects on low-frequency vibrational spectrum of liquid water: The instantaneous-normal-mode analysis
(2006-01-10)
Tsai, KH
;
Wu, TM
;
物理研究所
;
Institute of Physics
Currently, the designations for the low-frequency vibrational spectrum of liquid water are still diversified. In this Letter. using the instantaneous normal mode (INM) formalism for subensembles, we have examined the effects of local structure on the low-frequency INM spectrum of liquid water. The classified subensembles of water molecules are characterized by either the geometry of Voronoi polyhedron or the H-bond configuration. With these subensembles, the translational contribution to the INM spectrum is investigated. Providing insights into the local structural dependence of the vibrations between H-bonded water molecules. our results are consistent with the conventional designations for the Raman spectrum of liquid water. (c) 2005 Elsevier B.V. All rights reserved.
Influence of PMMA-chain-end tethered polyhedral oligomeric silsesquioxanes on the miscibility and specific interaction with phenolic blends
(2006-01-10)
Huang, CF
;
Kuo, SW
;
Lin, FJ
;
Huang, WJ
;
Wang, CF
Two different molecular weights of poly(methyl methacrylate) (PMMA) and PMMA containing polyhedral oligomeric silsesquioxane (PMMA-POSS) homopolymers have been prepared via the atom transfer radical polymerization (ATRP) technique. The miscibility and specific interaction behaviors of PMMA-POSS and PMMA with phenolic resin were investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). FTIR results reveal that at least three competing equilibriums are present in the phenolic/PMMA-POSS blend: self-association of phenolic (hydroxyl-hydroxyl), hydroxyl-siloxane interassociation between phenolic and POSS, and hydroxyl-carbonyl interassociation between phenolic and PMMA. Among these blends, single and higher T(g)s of these phenolic/PMMA-POSS blends were observed than the corresponding phenolic/PMMA blends at same composition, revealing that a stronger interassociation interaction of hydroxyl-siloxane than the hydroxyl-carbonyl interaction. Furthermore, we also found the screening effect in phenolic/LPMMA-POSS blends that tends to significantly decrease the hydrogen bond formation of the hydroxyl-carbonyl interassociation.
遞減面積之分散式靜電放電防護電路
(2006-01-11)
柯明道
;
郭秉捷
本發明提出一種遞減面積之分散式靜電放電防護電路，包括一信號輸入端、一接地端、一信號輸出端，且有一電源供應端，並有數靜電放電防護元件組相並聯在信號輸入端及信號輸出端間，且每一靜電放電防護元件組連接於電源供應端及接地端間，且在信號輸入端及信號輸出端間串聯有數高阻抗傳輸線，且每一高阻抗傳輸線分別連接於信號輸入端、靜電放電防護元件組及信號輸出端間，其特徵在於：每一靜電放電防護元件組包含二靜電放電防護元件，且靜電放電防護元件組內之靜電放電防護元件的面積尺寸係由信號輸入端至信號輸出端呈現遞減順序。本發明兼具寬頻電路及阻抗匹配之特點，並具較佳之靜電放電防護效果。
(In0.52Al0.48)(1-x)MnxAs muted magnetic semiconductor grown on InP substrates
(2006-01-11)
Lee, WN
;
Chen, YF
;
Huang, JH
;
Guo, XJ
;
Kuo, CT
A series of diluted magnetic semiconductors, (In0.52Al0.48)(1-x)MnxAs (0 < x <= 0. 11), was successfully grown on InP substrate by low-temperature molecular beam epitaxy. Our results indicate that (In0.52Al0.48)(1-x)MnxAs exhibits interesting magnetic behaviours at 5 K: it shows paramagnetic-like behaviour when x <= 0.05 and ferromagnetic behaviour when x >= 0.06.
鐵電元件之製造方法及鐵電材料之熱處理方法
(2006-01-11)
鄭晃忠
;
王志良
;
詹爵魁
;
史德智
;
郭孟維
本發明提供一種鐵電元件之製造方法及鐵電材料之熱處理方法，係在形成鐵電薄膜之後，採用低能量之雷射退火為第一階段處理，以使鐵電薄膜表面形成結晶核並改善薄膜內應力狀態，接著施以高能量之第二階段熱處理，以大幅改善整體鐵電薄膜結晶結構，進而獲得良好之鐵電特性。因此本發明提供一種低製程溫度及低熱應力之鐵電材料熱處理方法，可有效降低交互擴散及低熔點成分的揮發，具有高可靠、低熱處理成本、快速熱處理、元件產出效率高等功效。
Femtosecond fluorescence dynamics of porphyrin in solution and solid films: The effects of aggregation and interfacial electron transfer between porphyrin and TiO(2)
(2006-01-12)
Luo, LY
;
Lo, CF
;
Lin, CY
;
Chang, IJ
;
Diau, EWG
The excited-state relaxation dynamics of a synthetic porphyrin, ZnCAPEBPP, in solution, coated on a glass substrate as solid films, mixed with PMMA and coated on a glass substrate as solid films, and sensitized on nanocrystalline TiO(2) films were investigated by using femtosecond fluorescence up-conversion spectroscopy with excitation in the Soret band, S(2). We found that the S(2) -> S(1) electronic relaxation of ZnCAPEBPP in solution and on PMMA films occurs in 910 and 690 fs, respectively, but it becomes extremely rapid, < 100 fs, in solid films and TiO(2) films due to formation of porphyrin aggregates. When probed in the S(1) state of porphyrin, the fluorescence transients of the solid films show a biphasic kinetic feature with the rapid and slow components decaying in 1.9 - 2.4 and 19 - 26 ps, respectively. The transients in ZnCAPEBPP/TiO(2) films also feature two relaxation processes but they occur on different time scales, 100 - 300 fs and 0.8 - 4.1 ps, and contain a small offset. According to the variation of relaxation period as a function of molecular density on a TiO(2) surface, we assigned the femtosecond component of the TiO(2) films as due to indirect interfacial electron transfer through a phenylethynyl bridge attached to one of four meso positions of the porphyrin ring, and the picosecond component arising from intermolecular energy transfer among porphyrins. The observed variation of aggregate-induced relaxation periods between solid and TiO(2) films is due mainly to aggregation of two types: J-type aggregation is dominant in the former case whereas H-type aggregation prevails in the latter case.
Electrical characterizations of a controllable field emission triode based on low temperature synthesized ZnO nanowires
(2006-01-14)
Lee, CY
;
Tseng, TY
;
Li, SY
;
Lin, P
;
材料科學與工程學系
Fabrication and field emission properties of a ZnO nanowire (NW) triode were investigated in this study. The ZnO NWs have a single-crystalline wurtzite structure, similar to 50 nm diameter and 3.4 x 10(10) cm(-2) number density. The ZnO NW triode shows good and controllable emission properties with the turn-on anode electric field (at a current density of 1 mu A cm(-2)), threshold anode electric field (at a current density of 1 mA cm(-2)) and field enhancement factor of 1.6, 2.1 V mu m(-1) and 3340, respectively. The ZnO NW triode exhibits transistor characteristics with a gate leakage region, linear region and saturation region. Furthermore, the controllable field emission performance of the ZnO NW triode can be enhanced by illumination and argon ion bombardment. A low temperature Si-based microelectronic compatible fabrication process was provided for successfully making ZnO NW based triodes with good field emission properties.
White-light emitting ZnO-SiO2 nanocomposite thin films prepared by the target-attached sputtering method
(2006-01-14)
Peng, YY
;
Hsieh, TE
;
Hsu, CH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
ZnO-SiO2 nanocomposite thin films were prepared using the target-attached RF sputtering method without substrate heating. The PL measurements showed that the SiO2 films containing uniformly dispersed ZnO nanoparticles emit white light consisting of violet, blue, and Green-yellow band emissions. The presence of the blue emission is attributed to the large number of ZnO/SiO2 interfaces, which enlarges the depletion layer width and then enhances the related transition. The Gaussian curve fitting of PL spectra revealed that the competition between the blue and green-yellow band emissions and the relative emission intensity is strongly associated with the number of ZnO nanoparticles embedded in the SiO2 matrix. XPS analysis revealed that the main component of the oxygen defect species in the ZnO nanocomposite thin films is 'O-' ions (531.1-531.7 eV) at the subsurface. Within the knowledge of the defect configuration, XPS data were also utilized to estimate the oxygen vacancies and the specific carrier concentration in ZnO nanoparticles and relate to the integrated intensities of emission bands. Further analyses indicated that the defect structure of samples could be manipulated by the number and distribution of ZnO nanoparticles in SiO2 matrix to yield a distinct luminescence spectrum.
Evolution of conduction and interface states of laterally wet-oxidized AlGaAs with oxidation time
(2006-01-15)
Chen, JF
;
Hsiao, RS
;
Hung, WK
;
Wang, JS
;
Chi, JY
The conduction and interface states of laterally wet-oxidized GaAs-AlGaAs-GaAs structures after various oxidation times are investigated. Effective current blocking is achieved after 150 min oxidation and the conduction of current through the oxidized AlGaAs layer is controlled by the Poole-Frenkel mechanism, from which a relative dielectric constant of 7.07 is obtained. At an oxidation time of 15 min, capacitance-voltage spectra exhibit capacitance dispersion over frequency, implying the presence of an interface state. The intensity of the dispersion increases with increasing the oxidation time and admittance spectroscopy reveals a significant interface state at similar to 0.28 eV at 45 min. Further increasing the oxidation time to 150 min broadens the interface state to a set of continuous interface states from 0.19-0.31 eV with decreasing densities from 3x10(11) to 0.9x10(11) eV(-1) cm(-2) and generates fixed charges of about 9.1x10(11) cm(-2) in the oxidized layer. By comparison to a similar trap in a relaxed InGaAs/GaAs, the interface state is tentatively assigned to the interaction of residual As with dislocations. (c) 2006 American Institute of Physics.
Fiber-fault monitoring technique for passive optical networks based on fiber Bragg gratings and semiconductor optical amplifier
(2006-01-15)
Yeh, CH
;
Chi, S
;
光電工程學系
;
Department of Photonics
A novel monitoring method for in-service fault indemnification in passive optical networks (PONs) is proposed and demonstrated experimentally. The proposed monitoring technique is based on fiber Bragg grating (FBG) sensors and fiber laser scheme, and a semiconductor optical amplifier (SOA) is used to serve as a gain medium. By detecting the number of the wavelength lasing, the fiber-fault can be monitored without affecting the in-service channels. Moreover, the strain behavior on the FBGs has also been discussed. (c) 2005 Elsevier B.V. All rights reserved.
Synthesis of a novel benzoxazine monomer-intercalated montmorillonite and the curing kinetics of polybenzoxazine/clay hybrid nanocomposites
(2006-01-15)
Yei, DR
;
Fu, HK
;
Chen, WY
;
Chang, FC
;
應用化學系
Polybenzoxazine (PBZ), which has a structure similar to that of phenolic resin, is formed through the thermal self-curing of benzoxazine, that is through a heterocyclic ring opening reaction that requires no catalyst and releases no condensation byproducts. We have used the solvent blending method to prepare PBZ/clay nanocomposites possessing various clay contents. We synthesized a monofunctional benzoxazine monomer (MBM) and then treated the clay with this intercalation agent. The results of X-ray diffraction (XRD) analysis indicated that MBM intercalated into the galleries of the clay; the nanocomposite possessed an exfoliated structure at 3% clay content. To better understand the curing kinetics of the PBZ/clay nanocomposites, we performed dynamic and isothermal differential scanning calorimetry (DSC) measurements. We describe the thermodynamics of the curing process, using all three of the Kissinger, Ozawa, and Kamal models. The Kissinger and Ozawa methods gave fairly close results for the calculated activation energies, which decreased upon increasing the clay content. The Kamal method, based on an autocatalytic model, suggested a total reaction order of between 2.4 and 2.8. The glass transition temperature (T,) decreased upon increasing the clay content. Thermogravimetric analysis (TGA) indicated that the nanocomposites have higher decomposition temperatures than does the pristine PBZ; this finding suggests an enhancement in their thermal stability. (c) 2005 Wiley Periodicals, Inc.
Synthesis and characterization of light-emitting oligo(p-phenylene-vinylene)s and polymeric derivatives containing three- and five-conjugated phenylene rings
(2006-01-15)
Lin, HC
;
Tsai, CM
;
Huang, GH
;
Lin, JM
;
材料科學與工程學系
Several series of light-emitting oligo(p-phenylene-vinylene)s (BIII and BV series containing three- and five-conjugated phenylene rings) with various side groups and end groups attached to the cores were synthesized and characterized. The analogous PBV polymers, derived from the BV series, were also synthesized and investigated. Blue and greenish light emissions were observed in the photoluminescence (PL) and electroluminescence (EL) spectra of the blend and pure films with these pi-conjugated structures. In contrast to the three-conjugated ring oligomers, the five-conjugated ring derivatives (oligomers and polymers) had larger maximum emission wavelength values of PL and EL emissions. Mesomorphism was introduced into the BV series by the replacement of three-conjugated rings (BIII series) with five-conjugated phenyl cores (BV series). The liquid-crystalline properties of the BV series with end groups (on both end rings) were better than those of analogous BV-OC8 without end groups. Polarized PL emissions were obtained by the alignment of liquid-crystalline phase in rubbing cells. Upon heating, different PL emission wavelengths and intensities were observed in various phases. Not only the solubility and thermal properties but also the PL and EL properties could be effectively adjusted by the attachment of flexible alkoxy groups either on the central rings or on both end rings of the conjugated cores. (c) 2005 Wiley Periodicals, Inc.
Growth mode transfer of self-assembled CdSe quantum dots grown by molecular beam epitaxy
(2006-01-15)
Lai, YJ
;
Lin, YC
;
Fu, CP
;
Yang, CS
;
Chia, CH
Self-assembled CdSe/ZnSe quantum dots (QDs) were grown at various growth temperatures on GaAs (0 0 1) by molecular beam epitaxy. An optimum growth temperature for CdSe/ZnSe QDs was found to be 260 degrees C. The Stranski-Krastanow (SK) growth mode was confirmed clearly by atomic force microscopy images. The coherent SK QDs were observed from 2.5 monolayers (MLs). Two types of QDs were found with the CdSe coverage of 3.0 MLs. It was attributed to a growth mode change from the coherent SK growth mode to the ripening growth mode. A schematic diagram of the growth mechanism of self-assembled CdSe QDs was presented. Moreover, the photoluminescence spectra of samples with various thicknesses were investigated. A dramatic change of optical properties confirmed that the QD structure formed with thickness above 2.5 MLs. Finally, the dot size and the density distributions were controlled after growth by in-chamber thermal annealing. For the sample grown at 3.0 MLs, the distribution of dot sizes was controlled from 6.0 to 6.5 x 10(3) nm(3) at an annealing temperature of 400 degrees C. (c) 2005 Published by Elsevier B.V.
On the relocation problem with a second working crew for resource recycling
(2006-01-15)
Lin, BMT
;
Huang, HL
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
In this paper, we introduce a variant of the relocation problem, which was formulated from a public house redevelopment project in Boston. In the problem of interest, given some initial resources in a common pool there is a set of jobs to be processed on a two-machine flowshop. Each job acquires a specific number of resources to start its processing and will return a number of resources to the pool at its completion. The resource consumption and resource recycle processes are performed on machine one and machine two, respectively, in a two-machine flowshop style. Abiding by the resource constraints, the problem seeks to find a feasible schedule whose makespan is minimized. In this paper, we first present NP-hardness proofs for some special cases. Three heuristic algorithms are designed to compose approximate schedules. Two lower bounds are developed and then used to test the performance of our proposed heuristics. Numerical results from computational experiments suggest that the proposed heuristics can produce quality solutions in a reasonable time.