Browsing by Issue Date, starting with "2005-05-25"

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A study on the hardness variation of alpha- and beta-pure titanium with different grain sizes
(2005-05-25)
Kao, YL
;
Tu, GC
;
Huang, CA
;
Liu, TT
;
材料科學與工程學系
In this study, the hardness and the microstructure of alpha and beta-pure Ti treated with different grain sizes were investigated. The alpha-Ti specimens were obtained by heating pure Ti at 750 degrees C for various periods and then quenched in water, while the beta-Ti specimens by heating at 1000 degrees C for various periods and then quenched in water. Experimental results show that the hardness of a-Ti decreased with increasing the grain size; whereas, the hardness of beta-Ti tends to increase with increasing grain size. From the microstructures examined with transmission electron microscope, it can be realized that the strengthening mechanisms of alpha- and beta-Ti are quite different. Grain boundary could be the main strengthening microstructure of alpha-Ti and the smaller grain size the higher hardness. The major strengthening microstructure of beta-Ti was martensitic twin with a very high dislocation density. The amount of martensitic twin increased with increasing the grain size of beta-Ti and, therefore, the larger grain size the higher hardness. (c) 2005 Elsevier B.V. All rights reserved.
Fast direct solver for the biharmonic equation on a disk and its application to incompressible flows
(2005-05-25)
Lai, MC
;
Liu, HC
;
應用數學系
;
Department of Applied Mathematics
We develop a simple and efficient FFT-based fast direct solver for the biharmonic equation on a disk. The biharmonic equation is split into a coupled system of harmonic problems. We first use the truncated Fourier series expansion to derive a set of coupled singular ODEs, then we solve those singular equations by second-order finite difference discretizations. Using a radial grid with shifting a half mesh away from the origin, we can handle the coordinate singularity easily without pole conditions. The Sherman-Morrison formula is then applied to solve the resultant linear system in a cost-efficient way. The computational complexity of the method consists of O(MN log(2) N) arithmetic operations for M x N grid points. The numerical accuracy check and some applications to the incompressible Navier-Stokes flows inside a disk are conducted. (c) 2004 Elsevier Inc. All rights reserved.
Model identification of ARIMA family using genetic algorithms
(2005-05-25)
Ong, CS
;
Huang, JJ
;
Tzeng, GH
;
運輸與物流管理系註：原交通所+運管所
;
科技管理研究所
ARIMA is a popular method to analyze stationary univariate time series data. There are usually three main stages to build an ARIMA model, including model identification, model estimation and model checking, of which model identification is the most crucial stage in building ARIMA models. However there is no method suitable for both ARIMA and SARIMA that can overcome the problem of local optima. In this paper, we provide a genetic algorithms (GA) based model identification to overcome the problem of local optima, which is suitable for any ARIMA model. Three examples of times series data sets are used for testing the effectiveness of GA, together with a real case of DRAM price forecasting to illustrate an application in the semiconductor industry. The results show that the GA-based model identification method can present better solutions, and is suitable for any ARIMA models. (c) 2004 Elsevier Inc. All rights reserved.
Microstrip directional coupler with nearly ideal TEM coupler performance
(2005-05-26)
Wang, SM
;
Hsieh, MY
;
Chiang, CH
;
Chang, CY
;
電信工程研究所
A meandered parallel coupled-line structure is proposed to achieve high directivity within a wide bandwidth. By properly increasing the meandered parallel coupled-line sections, the high-directivity band-width becomes much wider. An example coupler is fabricated to verify the theory. More than 50 dB of isolation is achieved over a bandwidth of zero to twice centre frequency.
Control of enhanced THz transmission through metallic hole arrays using nematic liquid crystal
(2005-05-30)
Pan, CL
;
Hsieh, CF
;
Pan, RP
;
Tanaka, M
;
Miyamaru, F
We demonstrate frequency tuning of enhanced THz radiation transmitted through a two- dimensional metallic hole array ( 2D- MHA) by controlling the index of refraction of the medium filling the holes and adjacent to the 2D- MHA on one side. The medium is a nematic liquid crystal ( NLC) and its index of refraction is varied using magnetically controlled birefringence of the NLC. With the NLC, the peak transmission frequency of the 2D- MHA shift to the red by 0.112 THz and can be tuned from 0.193 to 0.188 THz. The peak transmittance is as high as 70% or an enhancement of 2.42 times, considering the porosity of the 2D- MHA. As a tunable THz filter, this device exhibits a continuous tuning range of 4.7 GHz, a low insertion loss of 2.35 to 1.55 dB and a quality factor of similar to 4- 5. (C) 2005 Optical Society of America.
Characterization of CF4-plasma fluorinated HfO2 gate dielectrics with TaN metal gate
(2005-05-30)
Lai, CS
;
Wu, WC
;
Wang, JC
;
Chao, T
;
物理研究所
In this paper, fluorine incorporation into the HfO2 gate dielectrics by post CF4 plasma treatment was proposed to improve the electrical characterization. TaN-HfO2-p-Si capacitors were demonstrated in this work. The characteristics of fluorinated HfO2 gate dielectrics were improved, including the capacitance-voltage hysteresis and current-voltage behaviors. This may be attributed to the fluorine incorporated into the HfO2 gate dielectrics as revealed by secondary ion mass spectroscopy. Moreover, the formation of Hf-F bonding was observed through electron spectroscopy for chemical analysis spectra. (c) 2005 American Institute of Physics.
An unusual, completely miscible, ternary hydrogen-bonded polymer blend of phenoxy, phenolic, and PCL
(2005-05-31)
Kuo, SW
;
Chan, SC
;
Wu, HD
;
Chang, FC
;
應用化學系
We have investigated the miscibility and hydrogen-bonding behavior of ternary blends of phenoxy, phenolic, and poly(e-caprolactone) (PCL) by using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy. On the basis of DSC analyses, we observed a rare totally miscible ternary hydrogen-bonded polymer blend in the amorphous phase: all compositions of this ternary blend display a single glass transition temperature. In addition, these single glass transition temperatures can be predicted well by extending the Kwei equation from the binary polymer blend to this ternary polymer blend. The infrared spectra indicate that the intermolecular hydrogen bonding of each pair of binary components still exists in the ternary polymer blend. We used the ternary totally miscible blend to determine the interassociation equilibrium constant between the hydroxyl groups of phenolic and the hydroxyl groups of phenoxy indirectly from the fraction of hydrogen-bonded carbonyl groups of PCL. Quantitative analyses suggest that interassociation between the hydroxyl groups of phenolic and the hydroxyl groups of phenoxy is more favorable than the hydroxyl-carbonyl interassociations of either phenolic/PCL or phenoxy/PCL and the hydroxyl-hydroxyl self-association of the pure phenolic and phenoxy homopolymers at room temperature.
Perceived fairness of pricing on the Internet
(2005-06-01)
Huang, JH
;
Chang, CT
;
Chen, CYH
;
管理科學系
;
經營管理研究所
The perceived fairness of price changes has been a subject of much inquiry in economic and marketing literature. This paper examines consumers' perceptions of the fairness of pricing on the Internet. Fair prices on the Internet, pricing mechanisms, methods of price discrimination and yield management are investigated from a consumer's perspective. Results obtained from 276 questionnaires collected in Taiwan indicate that the Internet prices that equal those in the traditional channels are perceived to be unfair. Respondents considered various pricing mechanisms on the Internet to be fair while many practices of price discrimination and yield management were perceived to be unfair. © 2004 Elsevier B.V. All rights reserved.
Reliability of strained SiGe channel p-channel metal-oxide-semiconductor field-effect transistors with ultra-thin (EOT=3.1nm) N2O-annealed SiN gate dielectric
(2005-06-01)
Chen, CW
;
Chien, CH
;
Chen, YC
;
Hsu, SL
;
Chang, CY
The p-channel metal-oxide-semi conductor field-effect transistor (pMOSFET) with 50-nm-thick Si0.85Ge0.15 channel and in ultra-thin (EOT = 3.1 nm) N2O-annealed SiN gate dielectric has been shown to have well-performing on/off and output characteristics. Several methodologies for the device reliability characterization, such as stress-induced-leakage-current (SILC), drain-avalanche-hot-carrier (DAHC) injection, channel hot-carrier (CHC) injection and negative-bias-temperature-instability (NBTI), have been used and the results were compared. In terms of the long-term degradation, the excellent quality of the N2O-annealed SiN gate dielectric can be firmly obtained because only negligible degradations have been found after stressing no matter which technique was employed. Even so, the experimental results have been compared and we found that the HC degradation is worse than the NBTI degradation and the channel-hot-carrier (CHC) stressing is the worst case for all kinds of reliability testing. Meanwhile, we have also verified that the interface state generation is the dominant mechanism responsible for the HC-induced degradation while the electron trapping dominates the device degradation for the NBTI stressing.
Implementation of wireless network environments supporting inter access point protocol and dual packet filtering
(2005-06-01)
Hwang, LY
;
Chiang, ML
;
Chang, RC
;
資訊工程學系
;
Department of Computer Science
With advances in wireless technologies, future internetworks will include large numbers of mobile hosts roaming across wireless cells. The goal of this paper is to provide a wireless network communication environment, in which mobile hosts can roam among various access points (wireless cells) and across different subnets. For this purpose, we develop methods to implement and integrate the communication mechanisms of Mobile IP and Inter Access Point Protocol (IAPP). For efficient transmission, we also devise a dual packet filtering technique to filter out unnecessary packet transmission, thereby reducing traffic on wireless networks. Such filtering is especially important because of the limited bandwidth of wireless links. Our work can serve as the reference once IAPP has been approved as standard. (c) 2004 Elsevier Inc. All rights reserved.
Improving high-temperature performance in continuous-wave mode InGaAsN/GaAsN ridge waveguide lasers
(2005-06-01)
Chang, YA
;
Kuo, HC
;
Lu, CY
;
Kuo, YK
;
Wang, SC
Continuous-wave (CW) mode operation InGaAsN/GaAsN double-quantum-well lasers with a laser wavelength of 1.295 mu m are demonstrated by metal-organic chemical vapour deposition (MOCVD). With the use of a high-bandgap GaAs0.9P0.1 into the active region before the growth of p-type layers, a room temperature (RT) threshold current of 99 mA and the characteristic temperature (TO) values of 155 K in a temperature range of 25-95 degrees C and 179 K in a temperature range of 25-85 degrees C are obtained from a 4 x 1000 mu m(2) ridge waveguide uncoated laser diode. The To value of the conventional structure without the high-bandgap GaAs0.9P0.1 is 118 K in a temperature range of 25-95 degrees C. High-temperature performance is improved and the results of numerical analysis suggest that it may be attributed to the reduced electronic leakage current.
Spin-flip transport through an interacting quantum dot
(2005-06-01)
Lin, KC
;
Chuu, DS
;
電子物理學系
;
Department of Electrophysics
The spin-flip associated transport based on the Anderson model is studied. It is found that the electrons are scattered due to spin-flip effect via the normal, mixed and Kondo channels. The spin-flip scattering via Kondo channel enhances the Kondo resonance peak and causes a slight blue shift. The conductance is suppressed by the spin-flip scattering. This is attributed to the reason that electrons with energy near Fermi level are scattered by Kondo channel. (c) 2005 Elsevier Ltd. All rights reserved.
一種超薄型平面喇叭之結構及其最佳化設計方法
(2005-06-01)
白明憲
;
呂彥志
本發明係為一種超薄型平面喇叭之結構及其最佳化設計方法，其結構包含一板材、一壓電材料一導電材以及懸邊。最佳化設計方法之模擬系統是以能量法與變分原理為基礎理論並利用有限元素法求解，其中程序同時考慮電能系統、機械系統以及聲場系統空氣之負載效應。再利田口實驗計畫法與基因演算法做結構之最佳化設計，以使得超薄型平面喇叭在較低之共振頻率下仍能維持與高共振頻率時之平均聲壓值相近，以達音質、音量最佳之目的。本創作之特點在於透過喇叭結構之最佳化程序可充分發揮音質喇叭之優點，不僅可以製作成任意平面形狀，大幅提高喇叭之聲功率，而且使用上非常省電有效率，並可改善喇叭在高共振頻率時，聲音太過尖銳之缺點。
A novel process-compatible fluorination technique with electrical characteristic improvements of poly-Si TFTs
(2005-06-01)
Wang, SD
;
Lo, WH
;
Chang, TY
;
Lei, TF
;
電子工程學系及電子研究所
A process-compatible fluorine passivation technique of poly-Si thin-film transistors (TFTs) was demonstrated by employing a novel CF4 plasma treatment. Introducing fluorine atoms into poly-Si films can effectively passivate the trap states near the SiO2/poly-Si interface. With fluorine incorporation, the electrical characteristics of poly-Si TFTs can be significantly improved including a steeper subthreshold slope, smaller threshold voltage, lower leakage current, higher field-effect mobility, and better On/Off current ratio. Furthermore, the CF4 plasma treatment also improves the reliability of poly-Si TFTs with respect to hot-carrier stress, which is due to the formation of strong Si-F bonds.
Intracavity PPLN crystals for ultra-low-voltage laser Q-switching and high-efficiency wavelength conversion
(2005-06-01)
Chen, YH
;
Huang, YC
;
Lin, YY
;
Chen, YE
;
電子物理學系
We report to the best of our knowledge the lowest switching voltage in an electro-optically Q-switched Nd: YVO4 laser by using a 13-mm long, 14-μ m-period PPLN crystal as a Pockels cell. A switching voltage as low as &SIM; 50V in the PPLN crystal was sufficient to hold off the lasing of the Q-switched laser at a pump power more than two times above its continuous-wave threshold. When the PPLN Q-switch was driven by a 100-V voltage at 6.5 kHz, we obtained 0.9-kW laser peak power from this 1-W diode-pumped Nd: YVO4 laser system with 13% output coupling. When the PPLN Pockels cell was cascaded with a 5-cm long, 30-μ m-period PPLN crystal, we produced &SIM; μ J/pulse energy at 1.59 μ m from optical parametric generation inside the actively Q-switched laser.
Guest editorial - Mobile computing and networking
(2005-06-01)
Wei, DSL
;
Naik, K
;
Lin, YB
;
Olariu, S
;
Wang, LC
Thermoelectric effects in superconductors
(2005-06-01)
Kolacek, J
;
Yang, TJ
;
電子物理學系
;
Department of Electrophysics
It is widely believed that temperature gradient does not induce electric field in the superconductor and consequently that thermoelectric effects do not exist, or are negligible in these materials. This statement is correct only as far as effective electric field or gradient of the electrochemical potential is concerned. In normal metals temperature gradient generates effective electric field, which nulls out thermally induced diffusion current. In superconductor the diffusion current of quasiparticles is canceled by a counterflow of supercurrent. Superconducting current induces the true electric field, which can be approximated by gradient of the screened Bernoulli potential. It explains familiar giant thermomagnetic flux observed in superconducting thermocouples. Contactless measurements of thermoelectric effects are suggested.
Applying hexagonal nanostructured zeolite particles for acetone removal
(2005-06-01)
Lin, YC
;
Bai, HL
;
Chang, CL
;
環境工程研究所
;
Institute of Environmental Engineering
This study examines the performance of a new adsorbent, hexagonal nanostructured zeolite particles (HNZP) for acetone adsorption and compares the results with that of commercial mobil synthetic zeolite-5 (ZSM-5) type zeolite. The HNZP is a pure siliceous adsorbent with different values of pore diameter and surface area being adjustable by the manufacturing condition. The results indicate that a slight increase in the average pore diameter (d) of HNZP from 2 to 2.5 nm leads to an increase in the acetone adsorption capacity, although its surface area is decreased, in which case (d = 2.5 nm) the adsorption capacity of fresh HNZP is better than that of ZSM-5 zeolite. Even for the fresh HNZP (d = 2 nm) of which the adsorption capacity is less than that of the ZSM-5 zeolite at relative humidity (RH) of 0%, its adsorption capacity is not deteriorated after repeated regeneration, but the adsorption capacity of regenerated ZSM-5 zeolite decays markedly. Thus, after only one regeneration, the adsorption capacity of HNZP (d = 2 nm) becomes better than that of the ZSM-5 zeolite. The decrease in the adsorption capacity of regenerated ZSM-5 zeolite might be because of its aluminum content that catalyzes the acetone into coke and, thus, blocks the adsorption sites. Furthermore, result on the moisture effect shows that because the pure siliceous HNZP was more hydrophobic than the ZSM-5 zeolite, the acetone adsorption efficiency of fresh HNZP (d = 2 nm) is better than that of ZSM-5 zeolite at RH = 50%.
Java-based component framework for dynamic reconfiguration
(2005-06-01)
Lee, YF
;
Chang, RC
;
資訊工程學系
;
Department of Computer Science
Updating software via the Internet is becoming a necessary feature of contemporary software. However, most software updating processes need to restart the programs or systems after the new software modules are installed. Dynamic reconfiguration is a technique that can deploy new software modules without restarting. This is usually achieved by modifying programming language syntax, language runtime systems or the code that is compiled. In the paper, a Java-based component framework is proposed to support dynamic reconfiguration, which does not need to modify the Java language, the Java virtual machine or the Java bytceode. The component framework has two implementations. The first one is based on the Java language itself; it is slower but can be used on almost every Java virtual machine. The second one is based on both the Java code and native programming interfaces provided by the Java virtual machine; it is much more efficient but is platform-dependent. The component framework is able to replace a single component as well as multiple components. In addition, several kinds of component change are permitted, including data members and component interfaces. To demonstrate the use of the component framework, a dynamically reconfigurable TCP is implemented.
Risk assessment for build-operate-transfer projects: a dynamic multi-objective programming approach
(2005-06-01)
Kang, CC
;
Feng, CM
;
Khan, HA
;
運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
This study uses a dynamic multi-objective programming approach to establish a risk assessment model, and develops an iterative algorithm for the model solution. The results obtained show that the sum of the interactive utility value could determine whether or not the interactive relationship is characterized by independence among negotiators. In addition, our numerical example shows that the risk measurement model developed can reflect risk assessment made by the negotiation group for certain events, and can analyze interaction characteristics among negotiators. (C) 2003 Elsevier Ltd. All rights reserved.