Browsing by Issue Date, starting with "2006-01-15"

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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.
Effect of phosphorus dopant on photoluminescence and field-emission characteristics of Mg0.1Zn0.9O nanowires
(2006-01-15)
Lee, CY
;
Tseng, TY
;
Li, SY
;
Lin, P
;
材料科學與工程學系
The photoluminescence and field-emission properties of Mg0.1Zn0.9O nanowires (MZO NWs) hydrothermally grown on the p-type silicon (100) substrates with and without phosphorus dopant were investigated in this study. Parts of MZO NWs were treated with PH3 plasma to form phosphorus-doped MZO NWs (PMZO NWs). The MZO and PMZO are wurtzite single crystals, and the surface morphologies of MZO NWs are identical to those of PMZO NWs with an average diameter of 50 nm and a length of 500 nm. The direct band gaps and emitted ultraviolet photoluminescences of the MZO and PMZO NWs are 3.41 eV and 403.8 nm and 3.56 eV and 385.4 nm, respectively. The MZO NWs grown on Si substrates have an emission threshold electric field of 1.8 V/mu m (current density of 1.0 mA/cm(2)) and a field enhancement factor, beta, of 3048 while the PMZO NWs show enhanced properties with a threshold electric field of 1.5 V/mu m and a beta value of 3054. These field-emission properties are also enhanced by illumination, which reveals that the emission behavior is affected by the surface charge state. Therefore, it is suggested that the band structure of MZO NWs has been modulated by phosphorus incorporation. (c) 2006 American Institute of Physics.
動態影像估測之裝置及方法
(2006-01-16)
吳炳飛
;
瞿忠正
;
陳昭榮
;
彭信元
;
游東龍
本發明係有關於一種動態影像估測之裝置及方法，此裝置具有複數個二維差值累積器、複數個位移暫存器、比較器、及加法器，二維差值累積器係用以執行變動影像及先前影像之比較，並輸出複數個對應之絕對差總和，再由比較器對此些絕對差總和進行比較，以取得一個最小之絕對差總和，因而得知變動影像與先前影像之運動向量，並記錄之。如此一來，影像資料僅需儲存變動影像及其運動向量，而非整幅之目前影像，故能減少影像資料之資料量。
Spectroscopy and femtosecond dynamics of type-II CdTe/CdSe core-shell quantum dots
(2006-01-16)
Chou, PT
;
Chen, CY
;
Cheng, CT
;
Pu, SC
;
Wu, KC
Syntheses of CdTe/CdSe type-II quantum dots (QDs) using CdO and CdCl2, as precursors for core and shell, respectively, are reported. Characterization was made via near-IR interbond emission, transmission electron microscopy (TEM), energy dispersive spectroscopy (EDX), and X-ray diffraction (XRD). Femtosecond fluorescence upconversion measurements on the relaxation dynamics of the CdTe core (in CdTe/CdSe) emission and CdTe/CdSe inter-band emission reveal that as the size of the core increases from 5.3, 6.1 to 6.9 nm, the rate of photoinduced electron separation decreases from 1.96, 1.44 to 1.07 X 10(12) s(-1). The finite rates of the initial charge separation ore tentatively rationalized by the small electron-phonon coupling, causing weak coupling between the initial and charge-separated states.
An aberrant autocrine activation of the platelet-derived growth factor alpha-receptor in follicular and papillary thyroid carcinoma cell lines
(2006-01-18)
Chen, KT
;
Lin, JD
;
Liou, MJ
;
Weng, HF
;
Chang, CA
Platelet-derived growth factor receptor (PDGFR) can bind to its ligand and consequently possess a kinase activity, and which is associated with the carcinogenesis of different cell types, including astrocytomas, oligodendrogliomas. and glioblastoma. In a cDNA microarray analysis, we observe the over-expressed mRNA of both PDGF-A and PDGF-alpha receptor in thyroid carcinoma cells. And the elevated protein expressions of PDGF-A and PDGF-alpha receptor in thyroid carcinoma cells were also confirmed by a Western blot analysis. The phosphorylation of PDGF-alpha receptor evaluated by an antibody against Tyr 720-phosphate was found in thyroid carcinoma cells. The tyrosine kinase activity of PDGF-alpha receptor was inhibited by tyrphostin AG1295 and showed a dose-dependent inhibition for the proliferation of thyroid carcinoma cells. These findings imply that autocrine activation of PDGF-alpha receptor plays a crucial role in the carcinogenesis of thyroid cells. (c) 2005 Elsevier Ireland Ltd. All rights reserved.
Structural and optical properties of ZnO nanosaws
(2006-01-18)
Wu, CY
;
Hsu, HC
;
Cheng, HM
;
Yang, S
;
Hsieh, WF
The randomly oriented ZnO nanosaws were synthesized on Si substrates by a simple vapor transport method. For structure characterization of the products, the SEM micrograph clearly reveals that length of nanosaw exceeds several tens of mu m and the side of sharp teeth of a saw has a length of about 1-5 mu m and diameters of about 100nm. The results of TEM, XRD, and Raman measurements indicate that the ZnO nanosaw is the single-crystal structure with the wurtzite phase. Under low excitation density, this UV emission peak measured at room temperature is attributed to the recombination of free excitons. Several sharp peaks emerge at photon energy around 3.18 eV with FWHM less than 4 meV when the sample is excited above a certain threshold. We refer that the random lasing in ZnO nanosaws results from the multiple coherent scattering in highly random-oriented ZnO nanosaws. (c) 2005 Elsevier B.V. All rights reserved.
Effects of doping concentration and annealing temperature on properties of highly-oriented al-doped ZnO films
(2006-01-18)
Kuo, SY
;
Chen, WC
;
Lai, FI
;
Cheng, CP
;
Kuo, HC
Transparent and conductive high-preferential c-axis-oriented Al-doped zinc oxide (ZnO:Al, AZO) thin films have been prepared by the sol-gel route. Film deposition was performed by spin-coating technique on Si(1 0 0) and glass substrate. Structural, electrical and optical properties were performed by XRD, SEM, four-point probe, photoluminescence (PL) and UV-VIS spectrum measurements. The effects of annealing temperature and dopant concentration on the structural and optical properties are well discussed. It was found that both annealing temperature and doping concentration alter the microstructures of AZO films. Also, PL spectra show two main peaks centered at about 380 nm (UV) and 520 nm (green). The variation of UV-to-green band emission was greatly influenced by annealing temperatures and doping concentration. Reduction in intensity ratio of UV-to-green might possibly originate from the formation of Al-O bonds and localized Al-impurity states. The minimum sheet resistance of 10(4)ohm/rectangle was obtained for the film doped with 1.6mol% Al, annealed at 750 degrees C. Meanwhile, all AZO films deposited on glass are very transparent, between 80% and 95% transmittance, within the visible wavelength region. These results imply that the doping concentration did not have significant influence on transparent properties, but improve the electrical conductivity and diversify emission features. (c) 2005 Elsevier B.V. All rights reserved.
Method of combining multilevel memory cells for an error correction scheme
(2006-01-19)
Wu, Jieh-Tsorng
;
Wang, Ta-Hui
;
Chang, Hsie-Chia
A memory combines plural memory cells for storing data wherein the differential stages voltage levels of memory cells are not limited in square value of 2 and can be improved linearly. The feature of the present invention can also increase memory capacity without increasing memory area. Furthermore it can remain voltage levels which cannot express 0 and 1 combination for error erasure messages when data is read. For efficient usage of memory, the increased memory capacity is not only for storing data but also for storing error correction scheme to assure the veracity of the storing data and improve producing yield and reliability for multilevel memory systems.
Internal rotation and spin conversion of CH3OH in solid para-hydrogen
(2006-01-20)
Lee, YP
;
Wu, YO
;
Lees, RM
;
Xu, LH
;
Hougen, JT
The quantum solid para-hydrogen (p-H-2) has recently proven useful in matrix isolation spectroscopy. Spectral lines of compounds embedded in this host are unusually narrow, and several species have been reported to rotate in p-H-2. We found that a p-H-2 matrix inhibits rotation of isolated methanol (CH3OH) but still allows internal rotation about the C-O bond, with splittings of the E/A torsional doublet in internal rotation-coupled vibrational modes that are qualitatively consistent with those for CH3OH in the gaseous phase. This simplified high-resolution spectrum further revealed the slow conversion of nuclear spin symmetry from species E to species A in the host matrix, offering potential insight into nuclear spin conversion in astrophysical sources.
Effect of prolonged HAART on oral colonization with Candida and candidiasis
(2006-01-20)
Yang, YL
;
Lo, HJ
;
Hung, CC
;
Li, YC
;
生物科技學系
Background: Progressive cell-mediated immunodeficiency with decrease of CD4+ lymphocyte count to less than or equal to 200 cells/mm(3) is a major risk factor for colonization with Candida species and development of candidiasis. Oropharyngeal candidiasis may occur in up to 90% of human immunodeficiency virus (HIV)-infected patients during the course of the disease. This study is to determine the effect of prolonged highly active antiretroviral therapy (HAART) on oropharyngeal colonization with Candida species and oral candidiasis. Methods: A prospective, longitudinal follow-up study in HIV-infected patients receiving HAART. Results: The mean CD4+ count increased from 232.5 to 316 cells/mm(3) and the proportion of patients whose CD4+ count less than 200 cells/mm(3) decreased from 50.0% to 28.9% (p = 0.0003) in patients receiving HAART for at least 2 years. The prevalence of oral candidiasis decreased from 10.6% to 2.1% (p = 0.004). The decrease in Candida colonization was less impressive, falling from 57.8% to 46.5% (p = 0.06). Of the 142 patients enrolled in at least two surveys, 48 (33.8%) remained colonized with Candida and 42 (29.6%) remained negative. In the remaining 52 patients, 34 switched from culture positive to negative, and an increase in CD4+ lymphocytes was noted in 91.2% of them. Among the 18 patients who switched from culture negative to positive, 61.1% also demonstrated an increase in CD4+ lymphocyte count (p = 0.01). Conclusion: These findings indicate that HAART is highly effective in decreasing oral candidiasis in association with a rise in CD4+ lymphocyte counts, but only marginally effective in eliminating Candida from the oropharynx.
A study of the recirculating flow in planar, symmetrical branching channels
(2006-01-20)
Tsui, YY
;
Lu, CY
;
機械工程學系
;
Department of Mechanical Engineering
A numerical method is employed to examine the now in symmetrical, two-dimensional branches of Y shape and Tee shape. The methodology is based oil a pressure-correction procedure within the frame of unstructured grids. Specified pressures are imposed at the outlets of the two branches. The area ratio of the branch is allowed to vary in the range of 2-3. Separation of the flow in the bifurcating region is inevitable. Willi equal Millet pressures, symmetrical flow patterns prevail except for the Y type branch Under the conditions of high Reynolds numbers and large area ratios. This implies that the Y-branch flow is more sensitive to small disturbances. It is shown that with a slightly higher pressure imposed oil one of the two branches the structure Of the recirculating flow for the Y type is greatly affected and the flow rate is reduced dramatically in the high-pressure branch channel. In contrast, the influence on the Tee type branch is much lower since the flow behaves like a jet impinging oil a confined duct. Copyright (c) 2005 John Wiley & Sons, Ltd.
Potassium ion recognition by 15-crown-5 functionalized CdSe/ZnS quantum dots in H2O
(2006-01-21)
Chen, CY
;
Cheng, CT
;
Lai, CW
;
Wu, PW
;
Wu, KC
Based on 15-crown-5 functionalized CdSe/ZnS quantum dots (QDs), we report a novel fluorogenic sensor to probe K+ ions in H2O; recognition of K+ can be achieved via the Forster type of energy transfer between two different color QDs, so that [K+] of the order of 10(-6) M can be promptly detected.
全空乏型絕緣層上矽晶金氧半場效電晶體裝置及其製法
(2006-01-21)
崔秉鉞
;
林家彬
本發明提出一種奈米尺寸之高性能絕緣層上矽晶金氧半場效電晶體裝置及其製法，其特徵在於裝置包括：一金屬氧化物半導體形成於絕緣層上矽晶基板之上；一金屬矽化物層，在閘極方面具有單一之全金屬矽化物閘極、高介電常數介電層以及可調變功函數之部件；在源、汲極部分則具有除了完全反應之金屬矽化物之源、汲極外，以及修正蕭基接面之源極與汲極結構。
Path-dependent human identification using a pyroelectric infrared sensor and Fresnel lens arrays
(2006-01-23)
Fang, JS
;
Hao, Q
;
Brady, DJ
;
Shankar, M
;
Guenther, BD
This paper presents a design and development of a low power consumption, and low cost, human identification system using a pyroelectric infrared (PIR) sensor whose visibility is modulated by a Fresnel lens array. The optimal element number of the lens array for the identification system was investigated and the experimental results suggest that the lens array with more elements can yield a better performance in terms of identification and false alarm rates. The other parameters of the system configuration such as the height of sensor location and sensor-to-object distance were also studied to improve spectral distinctions among sensory data of human objects. The identification process consists of two parts: training and testing. For the data training, we employed a principal components regression (PCR) method to cluster data with respect to different registered objects at different speed levels. The feature data of different objects walking along the same path in training yet at random speeds are then tested against the pre-trained clusters to decide whether the target is registered, and which member of the registered group it is. (c) 2006 Optical Society of America.
Synthesis and characterization of light-emitting H-bonded complexes and polymers containing bis(pyridyl) emitting acceptors
(2006-01-24)
Lin, HC
;
Tsai, CM
;
Huang, GH
;
Tao, YT
;
材料科學與工程學系
A series of bis(pyridyl) acceptor emitters are synthesized and the LC and photophysical (PL and EL) properties of their supramolecular structures, including H-bonded polymer networks and trimers, are explored. Unique mesomorphic properties may be introduced into these H-bonded complexes and polymers containing nonmesogenic acceptor emitters. In addition, the emission properties of bis(pyridyl) acceptor emitters can be adjusted by their surrounding nonphotoluminescent proton donors. Compared with pure bis(pyridyl) acceptor emitters, red-shifts of PL emission wavelengths were observed in most of the H-bonded complexes and polymers. Because of the higher acidity value of m-PC(10)BA (16) and its stronger H-bonded effect in H-bonded polymer complexes, the largest red-shift of 93 nm in lambda(max) value of PL has occurred in the fully H-bonded polymer network p-PBBBP-OC8 (8)/m-PC(10)BA (16) in contrast to pure emitter p-PBBBP-OC8 (8). A very narrow full width at half-maximum (fwhm) value (38 nm) of EL spectra can be obtained in the device of H-bonded complexes blended with PVK, and a higher brightness of EL is produced at an appropriate annealing temperature.