Browsing by Issue Date, starting with "2007-07-05"

Now showing 1 - 20 of 59414

交大e-News第005期
(2007-07-05)
Secretariat
;
國立交通大學秘書室
Clock switching circuit
(2007-07-05)
Wu, Jian-Hua
;
Hwang, Wei
The present invention discloses a clock switching circuit, which comprises: a clock generator, receiving two different clock signals; a logic gate, coupled to an enable-signal generator and an output-clock generator, wherein during clock switching, the logic gate turns off output clock according to the signal edges of those two clock signals to avoid the problems of clock glitch and timing insufficiency, and the logic gate will not restore clock output until an appropriate timing occurs.
Tunable fiber amplifier and laser using discrete fundamental-mode cutoff
(2007-07-05)
Chi, Sien
;
Chen, Nan-Kuang
The present invention uses short-pass filters to suppress the optical gain in C-band of an Er-doped optical fiber by discrete fundamental-mode cutoff so that S-band with shorter wavelength can obtain enough optical gain for signal amplification.
Relativistic parametrization of the self-consistent-charge density-functional tight-binding method. 1. Atomic wave functions and energies
(2007-07-05)
Witek, Henryk A.
;
Koehler, Christof
;
Frauenheim, Thomas
;
Morokuma, Keiji
;
Elstner, Marcus
A detailed treatment of a confined relativistic atom, needed as an initial step for the parametrization of the self-consistent-charge density-functional tight-binding method, is presented and discussed. The required one-component quantities, i.e., orbital energies, orbital wave functions, and Hubbard parameters, are obtained by weighted averaging of the corresponding numbers determined for the atomic spinors. The wave function and density confinement is achieved by introducing the Woods-Saxon potential in the atomic four-component Dirac-Kohn-Sham problem. The effect of the additional confining potential on energy eigenvalues and the shape of atomic wave functions and densities is discussed and numerical examples are presented for the valence spinors of carbon, germanium, and lead.
Ultrafast relaxation of zinc protoporphyrin encapsulated within apomyoglobin in buffer solutions
(2007-07-05)
Luo, Liyang
;
Chang, Chin-Hao
;
Chen, Yue-Ching
;
Wu, Tung-Kung
;
Diau, Eric Wei-Guang
The relaxation dynamics of a zinc protoporphyrin (ZnPP) in THF, KPi buffer, and encapsulated within apomyoglobin (apoMb) was investigated in its excited state using femtosecond fluorescence up-conversion spectroscopy with S-2 excitation (lambda(ex) = 430 nm). The S-2 -> S-1 internal conversion of ZnPP is ultrafast (tau < 100 fs), and the hot S-1 ZnPP species are produced promptly after excitation. The relaxation dynamics of ZnPP in THF solution showed a dominant offset component (tau = 2.0 ns), but it disappeared completely when ZnPP formed aggregates in KPi buffer solution. When ZnPP was reconstituted into the heme pocket of apoMb to form a complex in KPi buffer solution, the fluorescence transients exhibited a biphasic decay feature with the signal approaching an asymptotic offset: at lambda(em) = 600 nm, the rapid component decayed in 710 fs and the slow one in 27 ps; at lambda(em) = 680 nm, the two time constants were 950 fs and 40 ps. We conclude that (1) the fast-decay component pertains to an efficient transfer of energy from the hot S-1 ZnPP species to apoMb through a dative bond between zinc and proximal histidine of the protein; (2) the slow-decay component arises from the water-induced vibrational relaxation of the hot S-1 ZnPP species; and (3) the offset component is due to S-1 -> T-1 intersystem crossing of the surviving cold S-1 ZnPP species. The transfer of energy through bonds might lead the dative bond to break, which explains our observation of the degradation of ZnPP-Mb samples in UV-vis and CD spectra upon protracted excitation.
Light-emitting diode of polymer nanocomposite with quantum dots
(2007-07-05)
Wei, Kung-Hwa
;
Chou, Chia-Hung
The present invention provides a light-emitting diode made of a polymer nanocomposite doped with quantum dots to improve luminescence efficiency and to increase stability and electrical characteristics.
Cross-sectional transmission electron microscopy observations on the Berkovich indentation-induced deformation microstructures in GaN thin films
(2007-07-07)
Chien, Chi-Hui
;
Jian, Sheng-Rui
;
Wang, Chung-Ting
;
Juang, Jenh-Yih
;
Huang, J. C.
Nanoindentation-induced mechanical deformation in GaN thin films prepared by metal-organic chemical-vapour deposition was investigated using the Berkovich diamond tip in combination with the cross-sectional transmission electron microscopy (XTEM). By using focused ion beam milling to accurately position the cross-section of the indented region, the XTEM results demonstrate that the major plastic deformation was taking place through the propagation of dislocations. The present observations are in support of attributing the pop-ins that appeared in the load-displacement curves to the massive dislocation activities occurring underneath the indenter during the loading cycle. The absence of indentation-induced new phases might have been due to the stress relaxation via the substrate and is also consistent with the fact that no discontinuity was found upon unloading.
Dislocation reduction in GaN grown on stripe patterned r-plane sapphire substrates
(2007-07-09)
Chen, Hou-Guang
;
Ko, Tsung-Shine
;
Ling, Shih-Chun
;
Lu, Tien-Chang
;
Kuo, Hao-Chung
Extended defect reduction in GaN can be achieved via direct growth on stripe patterned (1(-)1 02) r-plane sapphire substrates by metal organic chemical vapor deposition. The striped mesa is along [11 (-)2 0] with two etched sides in {0001} and {1 (-)1 01} faces. GaN grown on both etched facets in epitaxy exhibit different crystallographic relationships with sapphire substrate which are (1 (-)1 02)(sapphire)parallel to(11 (-)2 0)(GaN) and [11 (-)2 0](sapphire)parallel to[ (-)1 100](GaN), and (0001)(sapphire)parallel to(0001)(GaN) and [11 (-)2 0](sapphire)parallel to[ (-)1 100](GaN), respectively. The dislocation densities can be significantly reduced through epitaxial growth on the inclined lateral faces of mesas. Dislocation density in the order of similar to 10(7) cm(-2) can be achieved in the tilted GaN. (C) 2007 American Institute of Physics.
n(+)-doped-layer-free microcrystalline silicon thin film transistors fabricated with the CuMg as source/drain metal
(2007-07-09)
Wang, M. C.
;
Chang, T. C.
;
Liu, Po-Tsun
;
Xiao, R. W.
;
Lin, L. F.
The feasibility of using CuMg as source/drain metal electrodes for n(+)-doped-layer-free microcrystalline silicon thin film transistors (mu-Si:H TFTs) has been investigated. The Ohmic-contact characteristic has been achieved by using the CuMg alloy as source/drain metal. Furthermore, a wet etching process of Cu alloy source/drain metal has been completed by using the ferric chloride base etchant. The proposed mu-Si:H TFT has shown similar electrical characteristic with the mu-Si:H TFT with n(+)-doped layer. The experimental result also showed that the CuMg alloy was suitable for the replacement of n(+)-doped layer in thin film transistor liquid-crystal displays. (C) 2007 American Institute of Physics.
Multi-slope handoff algorithm for controlling dynamic communication quality in wireless communications
(2007-07-10)
Huang
;
Ching Yao
;
Tsai
;
Ming Yuan
;
Huang
A multi-slope handoff algorithm for controlling dynamic communication quality in wireless communications is proposed to let a mobile node adjust the handoff slope according to different communication connection situations for setting the optimum add/drop connection trigger thresholds. The algorithm comprises the following steps. First, a mobile node receives pilot strengths of its service pilot and nearby pilots to produce an aggregate strength. Next, the mobile node determines whether to perform handoff according to the magnitude of the aggregate strength. The handoff action is then controlled by multi-slope handoff operations to set an appropriate slope and to calculate the add/drop connection trigger thresholds when performing handoff. Finally, the pilot to be connected is selected based on the communication quality at that time. In this way, the quality of the communication service can be enhanced, the connection power consumption can be lowered, and the communication channel usage can be reduced.
Method of combining multilevel memory cells for an error correction scheme
(2007-07-10)
Wu
;
Jieh-Tsorng
;
Wang
;
Ta-Hui
;
Chang
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.
Structural evolution of poly(styrene-b-4-vinylpyridine) diblock copolymer/gold nanoparticle mixtures from solution to solid state
(2007-07-10)
Huang, Ching-Mao
;
Wei, Kung-Hwa
;
Jeng, U-Ser
;
Liang, Keng S.
;
材料科學與工程學系
We used in situ annealing small-angle X-ray scattering to monitor the structural evolution of a spherical poly(styrene-b-4-vinylpyridine) diblock copolymer (PS-b-P4VP)/2-phenylethanethiol-coated Au nanoparticle (AuSC2Ph) mixture in the solid state during its thermal annealing. We found that the Au nanoparticles (NPs) that existed initially in a random state with some cluster packing in the PS domain diffused to the interface of the amphiphilic PS-b-P4VP diblock copolymer within 4 h at 170 degrees C under vacuum to form NP-filled shell-like assemblies, as further evidenced from transmission electron microscopy imaging. From the X-ray photoelectron spectroscopy data, we speculate that this interfacial activity of AuSC2Ph results from the fact that the initially hydrophobic Au NP surfaces became increasingly hydrophilic as most of the 2-phenylethanethiol ligands had evaporated off. The Au NP nanoshell assemblies located at the interface between PS and P4VP were quite stable even after redissolving in toluene; they remained in the form of PS-Au-P4VP core/shell/corona onion micelles, as evidenced from solution state small-angle X-ray scattering data.
Transient evolution of carbon monoxide poisoning effect of PBI membrane fuel cells
(2007-07-10)
Wang, Chien-Ping
;
Chu, Hsin-Sen
;
Yan, Yi-Yie
;
Hsueh, Kan-Lin
;
機械工程學系
High temperature poly benzimidazole membrane fuel cells are the focus of attention due to high CO tolerance and overcoming water managements. This paper develops a transient. one-dimensional mathematical model to predict CO tolerance, and validates it with experiments. Experimental results are measured at different temperatures. Fuel cell performance degradations with time are also measured under various fuel compositions. Transient evolutions of current density, H-2 coverage, CO coverage, and ionic potential are shown during the CO poisoning process. The theoretical results show that hydrogen coverage decreases with time, reducing hydrogen oxidation reactions and dropping ionic potential loss. The effects of temperature. CO contents. and H-2 dilutions on fuel cell performance and the time to reach steady t(ss) are all investigated. Predictions of fuel cell current density degradation also show good agreement with experimental results. (c) 2007 Elsevier B.V. All rights reserved.
Kernel support for zero-loss Internet service restart
(2007-07-10)
Chang, Da-Wei
;
Tsai, Chuan-Ming
;
Li, Wei-Kou
;
Lee, Tzu-Rung
;
資訊工程學系
Owing to long serving time and huge numbers of clients, Internet services can easily suffer from transient faults. Although restarting a service can solve this problem, information of the on-line requests will be lost owing to the service restart, which is unacceptable for many commercial or transaction-based services. In this paper, we propose an approach to achieve the goal of zero-loss restart for Internet services. Under this approach, a kernel subsystem is responsible for detecting the transient faults, retaining the I/O channels of the service, and managing the service restart How. In addition, some straightforward modifications to the service should be made to take advantage of the kernel support. To demonstrate the feasibility of our approach, we implemented the subsystem in the Linux kernel. Moreover, we modified a Web server and a CGI program to take advantage of the kernel support. According to the experimental results, our approach incurs little runtime overhead (i.e. less than 3.2%). When the service crashes, it can be restarted quickly (i.e. within 210 mu s) with no information loss. Furthermore, the performance impact due to the service crash is small. These results show that the approach can efficiently achieve the goal of zero-loss restart for Internet services. Copyright (C) 2006 John Wiley & Sons, Ltd.
Copper metalized ohmic contact electrode of compound device
(2007-07-12)
Lee, Cheng-Shih
;
Chang, Edward Yi
;
Chen, Ke-Shian
The present invention provides an ohmic contact for a copper metallization whose heat diffusion is improved and cost is reduced. Therein, the ohmic contact is formed through a depositing and an annealing of three metal layers of Pd, Ge and Cu; and, the contact resistance of the ohmic contact is adjusted by the thicknesses of the three layers.
Staggered source/drain and thin-channel TFT structure and fabrication method thereof
(2007-07-12)
Chang, Kow-Ming
;
Lin, Gin-Min
This invention relates to a process for fabricating a staggered source/drain and thin-channel TFT structure, which simplifies the conventional process for fabricating the structure by decreasing the number of mask steps and achieving better results at suppressing the electric field near the drain junction and reducing the leakage current. The process comprises (1) re-crystallizing a-Si into poly-Si (02), which is performed by depositing an a-Si layer on a substrate and then applying a general photolithographic step and a RIE etching step for defining the amorphous Si islands provided with higher regions and lower regions, wherein the residual width of the thin channel of the a-Si is about 5 to 200 nm after etching; then the a-Si is changed into poly-Si (02) after a subsequent annealing; (2) defining the gate region (05), source/drain region (07) and the channel; (3) applying the implantation; and (4) applying the connection.
Pragmatical generalized synchronization of chaotic systems with uncertain parameters by adaptive control
(2007-07-15)
Ge, Zheng-Ming
;
Yang, Cheng-Hsiung
;
機械工程學系
;
Department of Mechanical Engineering
A new kind of generalized synchronization of two chaotic systems with uncertain parameters is proposed. Based on a pragmatical asymptotical stability theorem and an assumption of equal probability for ergodic initial conditions, an adaptive control law is derived so that it can be proved strictly that the common null solution of error dynamics and of parameter dynamics is actually asymptotically stable, i.e. these two identical systems are in generalized synchronization and the estimated parameters approach the uncertain values. It is called pragmatical generalized synchronization. Finally, two numerical examples are studied for two Quantum-CNN oscillator chaotic systems to show the effectiveness of the proposed generalized synchronization strategy with a double Duffing chaotic system as a goal system. (C) 2007 Elsevier B.V. All rights reserved.
White electroluminescence from a single polymer: A blue-emitting polyfluorene incorporating orange-emitting benzoselenadiazole segments on its main chain
(2007-07-15)
Chien, Chen-Han
;
Shih, Ping-I
;
Shu, Ching-Fong
;
應用化學系
;
Department of Applied Chemistry
We have developed efficient white-light-emitting polymers through the incorporation of low-bandgap orange-light-emitting benzoselenadiazole (BSeD) moieties into the backbone of a blue-light-emitting bipolar polyfluorene (PF) copolymer, which contains hole-transporting triphenylamine and electron-transporting oxadiazole pendent groups. By carefully controlling the concentrations of the low-energy-emitting species in the resulting copolymers, partial energy transfer from the blue-fluorescent PF backbone to the orange-fluorescent segments led to a single polymer emitting white light and exhibiting two balanced blue and orange emissions simultaneously. Efficient polymer light-emitting devices prepared using this copolymer exhibited luminance efficiencies as high as 4.1 cd/A with color coordinates (0.30, 0.36) located in the white-light region. Moreover, the color coordinates remained almost unchanged over a range of operating potentials. A mechanistic study revealed that energy transfer from the PF backbone to the low-bandgap segments, rather than charge trapping, was the main operating process involved in the electroluminescence process. (c) 2007 Wiley Periodicals, Inc. Inc.
Influences of Ti, TiN, Ta and TaN layers on integration of low-k SiOC : H and Cu
(2007-07-15)
Tsai, Kou-Chiang
;
Wu, Wen-Fa
;
Chao, Chuen-Guang
;
Hsu, Jwo-Lun
;
Chiang, Chiu-Fen
The interactions between low-k material hydrogenated silicon oxycarbide (SiOC:H) and barrier layers, Ta, TaN, physical-vapor deposition (PVD) and chemical-vapor deposition (CVD) Ti and TiN, have been investigated. The results show these barriers except TaN can react with SiOC:H at evaluated temperature. Furthermore, significant interactions of carbon and oxygen due to the degradation of the SiOC:H films upon annealing exist for all barrier/SiOC:H structures. The CVD-TiN structure can retard the hydrogen out-diffusion, while PVD-TiN structure induces the H out-diffusion from the SiOC:H films. By studying flat band voltage shift in C-V tests, it is demonstrated that Cu+ ions drift into SiOC:H under electric field at elevated temperatures. A thin layer of TaN is proven to be good Cu drift barrier layer with SiOC:H dielectrics. (c) 2007 Elsevier B.V. All rights reserved.
Synthesis and characterization of a polyfluorene containing carbazole and oxadiazole dipolar pendent groups and its application to electroluminescent devices
(2007-07-15)
Yuan, Mao-Chuan
;
Shih, Ping-I
;
Chien, Chen-Han
;
Shu, Ching-Fong
;
應用化學系
We have synthesized a blue-light-emitting polyfluorene (PF) derivative (PF-CBZ-OXD) that presents bulky bole-transporting carbazole and electron-transporting oxadiazole pendent groups functionalized. at the C-9 positions of alternating fluorene units. The results from photoluminescence and electrochemical measurements indicate that both the side chains and the PF main chain retain their own electronic characteristics in the copolymer. An electroluminescent device incorporating this polymer as the emitting layer was turned on at 4.5 V; it exhibited a stable blue emission with a maximum external quantum efficiency of 1.1%. Moreover, we doped PF-CBZ-OXD and its analogue PF-TPA-OXD with a red-light-emitting iridium phosphor for use as components of phosphorescent red-light emitters to investigate the effect of the host's HOMO energy level on the degree of charge trapping and on the electrophosphorescent efficiency. We found that spectral overlap and individual energy level matching between the host and guest were both crucial features affecting the performance of the electroluminescence devices. Atomic force microscopy measurements indicated that the dipolar nature of PF-CBZ-OXD, in contrast to the general nonpolarity of polydialkylfluorenes, provided a stabilizing environment that allowed homogeneous dispersion of the polar iridium triplet dopant. (c) 2007 Wiley Periodicals, Inc.