Browsing by Issue Date, starting with "2007-06-06"

Now showing 1 - 20 of 59574

Nanomanipulation measurement and PIC simulation of field-emission properties from a single crystallized silicon nano-emitter
(2007-06-06)
Cheng, T. C.
;
Hsu, K. H.
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Chen, P. Y.
;
Huang, W. J.
;
Wu, J. S.
The field-emission characteristics of a single silicon nano-emitter were investigated by means of experiments and simulation models. The emitter array was fabricated by dry etching using an inductively coupled plasma (ICP) through a three-step process. A novel experimental technique was developed to precisely measure the field-emission current from a single silicon emitter. Accompanying these measurements, a parallelized three-dimensional particle-in-cell (PIC) code, in which the Fowler - Nordheim emission law was implemented at the emitter surface, was employed to simulate the emission current both with and without taking into account the space charge effect. Results show that the simulated I - V relationship when considering the space - charge effect was in excellent agreement with the actual measurements. Noticeably, the predicted turn-on voltage was found to be within only 9.3% of the experimental data. In addition, both the predicted and experimental data demonstrated a consistent single linear slope in the FN plot, which indicates that the field emission from a single silicon tip is a barrier-tunnelling, quantum mechanical process.
Process of producing group III nitride based reflectors
(2007-06-07)
Huang, Gensheng
;
Yao, Hsin-Hung
;
Kuo, Hao-Chung
;
Wang, Shing-Chung
To solve the existing problems in distributed Bragg reflectors (DBR) used in the prior art, the present invention provides a fabrication method of group III nitride based distributed Bragg reflectors (DBR) for vertical cavity surface emitting lasers (VCSELs), which suppresses the generation of cracks, and a distributed Bragg reflector with high reflectivity, broad stopband, and adaptability to optical devices such as vertical cavity surface emitting lasers, micro-cavity light emitting diodes, resonance cavity light emitting diodes and photodetectors.
DualMAC: A soft handoff mechanism for real-time communications in secured WLANs
(2007-06-08)
Tsao, Shiao-Li
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Lo, Pang Hsiang
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資訊工程學系
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Department of Computer Science
WLAN has been widely deployed over public and private areas in recent years and has become one of the most popular access technologies for mobile Internet services. Handoffs between WLAN access points (APs) that introduce packet loss and delay during a network session is one of the critical issues for real-time communication services. Unfortunately, most of the previous studies in reducing handoff latency and packet loss in WLANs rely on WLAN infrastructure upgrades, and those solutions suffer from deployment problems in the well-established WLAN hotspots. In this work, a pure station (STA)-side approach which only requires the firmware or software upgrade on WLAN STAs without the enhancements of the WLAN standards and infrastructures is presented. The proposed mechanism developed from a time division duplex concept maintains both connections with the serving and target AP simultaneously using two different medium access control (MAC) addresses. Thus, an STA can perform WLAN association, authentication, security key handshake procedures with the target AP, or further acquires an IP address in a new subnet while transmitting and receiving real-time packets through the serving AP at the same time. Simulation results demonstrate that seamless handoffs for real-time communications in secured WLANs can be easily achieved by the proposed mechanism. (C) 2007 Elsevier B.V. All rights reserved.
QoS-aware mobile service transactions in a wireless environment
(2007-06-10)
Younas, Muhammad
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Chao, Kuo-Ming
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Wang, Ping
;
Huang, Chun-Lung
;
資訊管理與財務金融系註：原資管所+財金所
Mobile computing greatly facilitates the provision of mobile services using portable and handheld devices which are connected through wireless networks. A pre-requisite for the provision of an effective service is to ensure quality of service (QoS) during the concurrent execution of requests and system or network failures. This paper presents a new transaction management approach for the provision of mobile services which is based on advanced transaction models and fuzzy selection criteria. It employs a novel QoS consensus moderation approach in order to select preferred mobile services from among various alternatives, thus providing multiple pathways to the completion of mobile service transactions. Unlike traditional transaction management schemes, the proposed approach takes into account QoS attributes in the commit process of mobile service transactions. The proposed approach is implemented as a prototype tool and evaluated through a number of experiments. Experimental results show that the proposed approach effectively selects mobile services and significantly increases the throughput (i.e. commit rate) of mobile service transactions. Copyright (C) 2007 John Wiley & Sons, Ltd.
Compact efficient eye-safe intracavity optical parametric oscillator with a shared cavity configuration
(2007-06-10)
Chen, Y. F.
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Su, K. W.
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Chang, Y. T.
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Yen, W. C.
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電子物理學系
We present a compact efficient eye-safe intracavity optical parametric oscillator pumped by a passively Q-switched Nd:YAG laser in a shared cavity configuration. A signal pulse of 3.3 mJ energy at a 1573 nm wavelength with a peak power of 150 kW was achieved. The effective conversion efficiency with respective to the optimized 1064 nm Q-switched pulse energy was as high as 51%. (C) 2007 Optical Society of America.
Discrete monolayer light emission from GaSb wetting layer in GaAs
(2007-06-11)
Lo, Ming-Cheng
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Huang, Shyh-Jer
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Lee, Chien-Ping
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Lin, Sheng-Di
;
Yen, Shun-Tung
Distinct light emission peaks from monolayers of GaSb quantum wells in GaAs were observed. Discrete atomic layers of GaSb for the wetting layer prior to quantum dot formation give rise to transition peaks corresponding to quantum wells with 1, 2, and 3 ML. From the transition energies the authors were able to deduce the band offset parameter between GaSb and GaAs. By fitting the experimental data with the theoretical calculated result using an 8x8 k center dot p Burt's Hamiltonian along with the Bir-Picus deformation potentials, the strain-free (fully strained) valence band discontinuity for this type-II heterojunction was determined to be 0.45 eV (0.66 eV). (c) 2007 American Institute of Physics.
Power consumption reduction scheme of magnetic microactuation using electroplated Cu-Ni nanocomposite
(2007-06-11)
Huang, Yu Wen
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Chao, Yuan
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Chen, C. C.
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Cheng, Y. T.
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電子工程學系及電子研究所
This letter presents a power consumption reduction scheme of magnetic microactuation using Cu-Ni nanocomposite film which is electroplated in alkaline noncyanide based Ni colloidal copper plating solution at 40 degrees C. The superconducting quantum interference device magnetometer measurements show that Cu film is modified from diamagnetism to ferromagnetism via the incorporation of Ni ferromagnetic nanoparticles into itself to form a Cu-Ni nanocomposite film. A magnetic microactuator made of the nanocomposite can have about 9% performance improvement in terms of actuation enlargement. In other words, the coil made of the Cu-Ni nanocomposite can exhibit better power efficiency for the same output displacement. (c) 2007 American Institute of Physics.
Erratum: "Thermomigration in flip-chip SnPb solder joints under alternate current stressing" [Appl. Phys. Lett. 90, 152105 (2007)]
(2007-06-11)
Hsiao, Hsiang-Yao
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Chen, Chih
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材料科學與工程學系
;
Department of Materials Science and Engineering
可用於窄頻濾波器之光纖光柵製作方法
(2007-06-11)
徐桂珠
;
許立根
;
項維巍
;
賴杰
本發明係提供一種可用於窄頻濾波器之光纖光柵製作方法，可使光纖於低紫外光曝照量時，折射率變化量與紫外光曝照量仍具有線性比例。本發明係以強度均勻之紫外光照射於一光纖上，使光纖整體產生適當且均勻之折射率變化，並以具有干涉條紋之紫外光照射該光纖，使光纖引致之折射率變化隨干涉條紋強度成正比以形成一光纖光柵。由於折射率變化量與紫外光曝照量間由非正比關係之操作點移至正比關係之操作點，本發明可有效改善光纖光柵折射率變化不易控制而容易發生變形之情形，提高製作結構複雜之光纖光柵的成功機率。
Flavonoids, centaurein and centaureidin, from Bidens pilosa, stimulate IFN-gamma expression
(2007-06-13)
Chang, Shu-Lin
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Chiang, Yi-Ming
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Chang, Cicero Lee-Tian
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Yeh, Hsu-Hua
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Shyur, Lie-Fen
Bidens pilosa is used as an ethnical medicine for bacterial infection or immune modulation in Asia, America and Africa. Here, we employed an IFN-gamma promoter-driven luciferase reporter construct and T cells to characterize immunomodulatory compounds from this plant based on a bioactivity-guided isolation principle. We found that PHA, a positive control, caused a six-fold increase in IFN-gamma promoter activity. In contrast, hot water crude extracts from Bidens pilosa and its butanol subfraction increased IFN-gamma promoter activity to two- and six-fold, respectively. Finally, centaurein (EC50 = 75 mu g/ml) and its aglycone, centaureidin (EC50 = 0.9 mu g/ml), isolated from this butanol subtraction, augmented IFN-gamma promoter activity by similar to four-fold. Consistent with the role of centaurein or its aglycone in IFN-gamma regulation, we showed that centaurein induced the activity of NEAT and NF kappa B enhancers, located within the IFN-gamma promoter, in Jurkat cells. Overall, our results showed that centaurein regulated IFN-gamma transcription, probably via NFAT and NF kappa B in T cells. (c) 2007 Elsevier Ireland Ltd. All rights reserved.
Electroluminescence and electron transport characteristics of aromatic polyimides containing 1,3,4-oxadiazole moiety
(2007-06-13)
Hsu, Shou-Chian
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Whang, Wha-Tzong
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Chao, Ching-Shiun
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材料科學與工程學系
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Department of Materials Science and Engineering
Single and double layer polymer light-emitting diodes (LEDs) were fabricated by using 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole (BAO)-based aromatic polyimides (APIs). All the resultant APIs have high glass transition temperatures (T-g>250 degrees C) and high thermal decomposition temperatures (T-d>510 degrees C). The APIs exhibit broad fluorescent characteristic, and the fluorescent intensity is related to the intermolecular chain's orientation. BAO-3,3 '-oxydiphthalic anhydride (ODPA) and BAO-4,4 '-(hexafluoro-iso-propylidene) diphthalic anhydride show electroluminescent property in single layer LED devices. By inserting BAO-ODPA in the poly(p-phenylene vinylene)-poly(vinylalcohol) LED device to form a double layer device, the EL efficiency can be improved by two orders of magnitude. (C) 2007 Elsevier B.V. All rights reserved.
Evidence for the electron trap state associated with N-rich clusters in InGaAsN/GaAs quantum wells
(2007-06-13)
Chen, J. F.
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Hsieh, P. C.
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Hsiao, R. S.
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Wang, J. S.
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Chi, J. Y.
An electron trap state has been found to appear in InGaAsN/GaAs quantum wells ( QWs) as a result of composition fluctuation. Evidence of composition fluctuation is shown by photoluminescence spectra which display an additional low-energy emission due to local regions of N-rich clusters. Enhancing composition fluctuation leads to undulated InGaAsN/GaAs interface with dot-like islands. The capacitance-voltage profiling shows an additional peak following the QW electron ground state peak, suggesting the presence of an electron trap state below the QW electron ground state. The emission properties of this trap state are similar to those of quantum dots immersed in a well. Enhancing composition fluctuation can cause an energy downward shift and spectral broadening of this electron trap state, suggesting an increase in island size and fluctuations of the size and composition. Thus, it is deduced that the electron trap state originated from the N-rich clusters in the well behaving like quantum dots. Upon modulation, the electrons are thermally activated from this trap state to the QW electron ground state and subsequently emitted to the GaAs bottom electrode.
Growth of GaAs expitaxial layers on Si substrate by using a novel GeSi buffer layer
(2007-06-14)
Chang, Edward Y.
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Luo, Guangli
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Yang, Tsung-Hsi
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Chang, Chun-Yen
This invention provides a process for growing Ge epitaixial layers on Si substrate by using ultra-high vacuum chemical vapor deposition (UHVCVD), and subsequently growing a GaAs layer on Ge film of the surface of said Ge epitaixial layers by using metal organic chemical vapor deposition (MOCVD). The process comprises steps of, firstly, pre-cleaning a silicon wafer in a standard cleaning procedure, dipping it with HF solution and prebaking to remove its native oxide layer. Then, growing a high Ge-composition epitaixial layer, such as Si0.1Ge0.9 in a thickness of 0.8 μm on said Si substrate by using ultra-high vacuum chemical vapor deposition under certain conditions. Thus, many dislocations are generated and located near the interface and in the low of part of Si0.1Ge0.9 due to the large mismatch between this layer and Si substrate. Furthermore, a subsequent 0.8 μm Si0.05Ge0.95 layer, and/or optionally a further 0.8 μm Si0.02Ge0.98 layer, are grown. They form strained interfaces of said layers can bend and terminate the propagated upward dislocation very effectively. Therefore, a film of pure Ge is grown on the surface of said epitaixial layers. Finally, a GaAs epitaixial layer is grown on said Ge film by using MOCVD.
Multimedia short message template application system and broadcast system, multimedia short message template applying method and broadcast method
(2007-06-14)
Chen, Deng-Jyi
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Hung, Chi-Chang
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Yang, Po-Chun
A multimedia short message template application system and a broadcast system, a multimedia short message template applying method and a broadcast method are disclosed. The multimedia short message template application system comprises a multimedia object, a multimedia database, a template database and an applying unit. The multimedia object includes an object content attribute and an object motion attribute. The object motion attribute includes an interaction function. The multimedia database is composed of a multimedia data. The template database is composed of short message templates. Any short message template includes a combination arrangement of a multimedia object. A corresponding short message template is found by the applying unit from the template database based on the selection chosen by a user. A corresponding multimedia data is then found from the multimedia database based on the selection chosen by the user again. Lastly, the corresponding multimedia data is loaded into the object content attribute of the short message template within the multimedia object to make a multimedia short message.
俺說
(2007-06-15)
管管
Fabrication of a miniature CMOS-based optical biosensor
(2007-06-15)
Ho, Wei-Jen
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Chen, Jung-Sheng
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Ker, Ming-Dou
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Wu, Tung-Kung
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Wu, Chung-Yu
This work presents a novel, miniature optical biosensor by immobilizing horseradish peroxidase (HRP) or the HRP/glucose oxidase (GOx) coupled enzyme pair on a CMOS photosensing chip with a detection area of 0.5 mm x 0.5 mm. A highly transparent TEOS/PDMS Ormosil is used to encapsulate and immobilize enzymes on the surface of the photosensor. Interestingly, HRP-catalyzed luminol luminescence can be detected in real time on optical H2O2 and glucose biosensors. The minimum reaction volume of the developed optical biosensors is 10 RL. Both optical H2O2 and glucose biosensors have an optimal operation temperature and pH of 20-25 degrees C and pH 8.4, respectively. The linear dynamic range of optical H2O2 and glucose biosensors is 0.05-20 mM H2O2 and 0.5-20 mM glucose, respectively. The miniature optical glucose biosensor also exhibits good reproducibility with a relative standard deviation of 4.3%. Additionally, ascorbic acid and uric acid, two major interfering substances in the serum during electrochemical analysis, cause only slight interference with the fabricated optical glucose biosensor. In conclusion, the CMOS-photodiode-based optical biosensors proposed herein have many advantages, such as a short detection time, a small sample volume requirement, high reproducibility and wide dynamic range. (c) 2007 Published by Elsevier B.V.
俺說
(2007-06-15)
管管
Deep-level emissions in GaAsN/GaAs structures grown by metal organic chemical vapor deposition
(2007-06-15)
Chen, J. F.
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Ke, C. T.
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Hsieh, P. C.
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Chiang, C. H.
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Lee, W. I.
This work presents the deep-level photoluminescence of coherently strained GaAsN/GaAs quantum-well (QW) structures with various GaAsN thicknesses and N contents. A broad deep-level emission at similar to 1.1 eV is observed, whose wavelength is redshifted as the GaAsN thickness increases. Based on its energy separation from the QW emission, this emission is attributed to a transition between the QW electron ground state and a deep level at similar to 0.2 eV above the GaAsN valence-band (VB) edge. This level is shown to be tied to the GaAs band edge. A transition between this level and the GaAs conduction band allows the GaAsN-GaAs band alignment to be evaluated. A type II band lineup is obtained with VB offsets of 0.03 and 0.002 eV for N=0.6% and 1.8%, respectively. The decreased VB offset suggests a transition from type II to type I with increasing N content. Thermal annealing effectively removes this level and improves the QW emission. The concentration of this level is not clearly correlated with N content, suggesting that this level is induced by a low-temperature growth of the GaAsN layer to suppress the composition fluctuation. Given its energy, this level is tentatively assigned to V-Ga. (c) 2007 American Institute of Physics.
俺說
(2007-06-15)
管管
Synthesis and characterization of side-chain liquid crystalline homopolymers and block copolymers containing biphenyl4-ylthiophene and biphenyl-4-ylfluorene pendants
(2007-06-15)
Lee, Kuan-Wei
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Lin, Hong-Cheu
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材料科學與工程學系
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Department of Materials Science and Engineering
A series of new liquid crystalline homopolymers (PI and P2) and block copolymers (P3 and P4) composed of methacrylates containing pendant biphenyl-4-ylthiophene (M1) and biphenyl-4-ylfluorene (M2) units were synthesized by atom transfer radical polymerization (ATRP). The number-average molecular weights (M-n) of the homopolymer (P2) and diblock copolymers (P3 and P4) were in the range of 5153-8713 g mol(-1) with polydispersity indices (PDIs) between 1.17 and 1.25. The thermal, mesogenic, and photoluminescence (PL) properties of all polymers were investigated. Except for the absence of mesogenic properties in block copolymer P4, polymers P1 and P3 possessed the smectic A phase and polymer P2 exhibited the nematic phase. Moreover, the mesomorphism and the layer d-spacing values of the smectic A phase in polymers P1 and P3 were confirmed and characterized by X-ray diffraction (XRD) patterns. (C) 2007 Elsevier Ltd. All rights reserved.