Browsing by Issue Date, starting with "2007-05-01"

Now showing 1 - 20 of 59803

A non-additive model for evaluating airline service quality
(2007-05-01)
Liou, James J. H.
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Tzeng, Gwo-Hshiung
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科技管理研究所
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Institute of Management of Technology
This study develops a non-additive model for evaluating and improving the service quality of airlines and compares its results with the conventional additive method. Service quality is a composite of various attributes and many in a system have inter-dependent characteristics that may not be correctly evaluated using conventional additive measures. A fuzzy integral is thus proposed. Factor analysis is initially used to extract some independent common-factors and fuzzy integral used to integrate the performance ratings of inter-dependent attributes in each common-factor. For the analytic hierarchy process a pair-wise comparative approach is adopted to determine the relative weights linking each independent common-factor. Finally, Grey relation analysis and simple additive weight method are used to find airline service quality. A study of international airlines is conducted for verification. Safety and reliability emerge as the critical factors of service quality. (C) 2007 Elsevier Ltd. All rights reserved.
Patterned self-assembly of magnetic biomolecules on semiconductor substrates
(2007-05-01)
Sun, Kien Wen
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Chang, Chia-Ching
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生物科技學系
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應用化學系
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應用化學系分子科學碩博班
The paper reports on the methods of preparing and patterning magnetic metallothionein (Mn,Cd-MT-2) molecules on semiconductor surfaces. The molecules are placed into nanopores prepared on silicon (0 0 1) substrates. We observe the self-assembled growth of those MT molecules on the patterned Si surface. Dense arrays of molecular rods are demonstrated on templates with small pores and pitch sizes. Then the structures of the self-assembled protein are studied by atomic force microscopy (AFM) and magnetic force microscopy (MFM). Our measurements indicate that molecular self-assembly has a magnetic dipole moment which interacts with the applied magnetic field. (c) 2007 Elsevier Ltd. All rights reserved.
Evaluating intertwined effects in e-learning programs: A novel hybrid MCDM model based on factor analysis and DEMATEL
(2007-05-01)
Gwo-Hshiung Tzeng
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Cheng-Hsin Chiang
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Chung-Wei Li
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科技管理研究所
;
Institute of Management of Technology
Internet evolution has affected all industrial and commercial activity and accelerated e-learning growth. Due to cost, time, or flexibility for designer courses and learners, e-learning has been adopted by corporations as an alternative training method. E-learning effectiveness evaluation is vital, and evaluation criteria are diverse. A large effort has been made regarding e-learning effectiveness evaluation; however, a generalized quantitative evaluation model, which considers both the interaffected relation between criteria and the fuzziness of subjective perception concurrently, is lacking. In this paper, the proposed new novel hybrid MCDM model addresses the independent relations of evaluation criteria with the aid of factor analysis and the dependent relations of evaluation criteria with the aid of DEM-ATEL. The AHP and the fuzzy integral methods are used for synthetic utility in accordance with subjective perception environment. Empirical experimental results show the proposed model is capable of producing effective evaluation of e-learning programs with adequate criteria that tit with respondent's perception patterns, especially when the evaluation criteria are numerous and intertwined. (C) 2006 Elsevier Ltd. All rights reserved.
10-GHz highly symmetrical sub-harmonic Gilbert mixer using GaInP/GaAs HBT technology
(2007-05-01)
Wu, Tzung-Han
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Meng, Chinchun
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電信工程研究所
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Institute of Communications Engineering
A 10-GHz sub-harmonic Gilbert mixer is demonstrated using GaInP/GaAs hetero-junction bipolar transistor technology. The local oscillator (LO) signal time-delay path in the sub-harmonic LO stage is compensated using the fully symmetrical stacked-LO doubler; therefore, the balance of the sub-harmonic LO stage, the radio frequency to intermediate frequency isolation, and IIP2 are improved. The demonstrated 10-GHz sub-harmonic mixer achieves 10 dB conversion gain, IP1dB of -12 dBm, IIP3 of 2 dBm and IIP2 of 33 dBm.
Optical characterization of Zn0.97Mn0.03Se/ZnSe0.92Te0.08 type II multiple-quantum-well structures
(2007-05-01)
Lin, D. Y.
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Shiu, J. J.
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Wu, J. D.
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Yang, C. S.
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Chou, W. C.
The optical characterization of type II Zn0.97Mn0.03Se/ZnSe0.92Te0.08 multiple-quantum-well structures have been studied using photoluminescence (PL), temperature-dependent PL, polarized PL, power-dependent PL, and photoreflectance (PR) in this study. The PL data reveal that the band alignment of the ZnMnSe/ZnSeTe system is type II. Comparing with the theoretical calculation based on the Schrodinger equation, the valence band offset is estimated to be 0.6 eV. From the power-dependent PL spectra, it is observed that the peak position of PL spectra shows a blueshift under different excitation power. The blueshift can be interpreted in terms of the band-bending effect due to spatially photoexcited carriers in a type II alignment. The thermal activation energy (E-A) for quenching the PL intensity was determined from temperature-dependent PL spectra. The thermal activation energy was found to decrease as the thickness of ZnMnSe and ZnSeTe layers decreased. The polarized PL spectra exhibit a large in-plane polarization with the polarization degree up to 50%. The polarization does not depend on the excitation intensity as well as temperature. The large polarization is an inherent orientation of the interface chemical bonds. The higher transition features observed in PR spectra show a blueshift with the similar trend observed in the PL spectra as decreasing the thickness of ZnSeTe layer. This result provides a consistent evidence for the assumption that square-like well shapes were built in the ZnSeTe layers. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Properties of vortex propagation in a niobium film with spacing-graded density of pinning sites
(2007-05-01)
Horng, Lance
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Wu, T. C.
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Wu, J. C.
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Cao, R.
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Yang, T. J.
The vortex propagation has been investigated in Nb superconductors with one dimension spacing-graded density of submicrometer-scaled holes in this research. A rectification effect can be discerned because the applied ac is transformed into a net dc voltage. These results demonstrate that the rectification is mainly characterized by the asymmetric pinning landscape and the rectified voltage depends considerably on temperature and the amplitude of applied ac. The dc voltage increases steeply up to the maximum value and then decreases to zero dc voltage with the increase of ac. The shape of peaks in the dc voltage signal become steeper and move to higher applied ac regime with the decrease of temperature.
Nonplanar modeling and experimental validation of a spindle-disk system equipped with an automatic balancer system in optical disk drives
(2007-05-01)
Chao, Paul C. -P.
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Sung, Cheng-Kuo
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Wu, Szu-Tuo
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Huang, Jeng-Sheng
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電控工程研究所
Non-planar dynamic modeling and experimental validation of a spindle-disk system equipped with an automatic ball-type balancer system (ABS) in optical disc drives are performed in this study. Recent studies about planar dynamic modeling and analysis have shown the capability of the ABS in spindle-disk assembly via counteracting the inherent imbalance. To extend the analysis to be practical, non-planar dynamic modeling are conducted in this study to re-affirm the pre-claimed capability of the ABS system, along with experiments being designed and conducted to validate the theoretical findings. Euler angles are first utilized to formulate potential and kinetic energies, which is followed by the application of Lagrange's equation to derive governing equations of motion. Numerical simulations are next carried out to explore dynamic characteristics of the system. It is found that the levels of residual runout (radial vibration), as compared to those without the ABS, are significantly reduced, while the tilting angle of the rotating assembly can be kept small with the ABS installed below the inherent imbalance of the spindle-disk system. Experimental study is also conducted, and successfully validates the aforementioned theoretical findings. It is suggested that the users of the ABS need to cautiously operate the spindle motor out of the speeds close to the resonances associated with various degrees of freedom. In this way, the ABS could hold the expected capability of reducing vibration in all important directions, most importantly in radial directions.
Sub-THz photonic-transmitters based on separated-transport-recombination photodiodes and a micromachined slot antenna
(2007-05-01)
Li, Yu-Tai
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Shi, J.-W.
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Pan, Ci-Ling
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Chiu, C.-H.
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Liu, W.-S.
We demonstrate a novel photonic transmitter, which is composed of a low-temperature-grown GaAs (LTG-GaAs)-based separated-transport-recombination photodiode and a micromachined slot antenna. Under femtosecond optical pulse illumination, this device radiates strong electrical pulses (4.5-mW peak power) without the use of a Si-lens. It can be observed in the Fourier transform infrared spectrometer spectrum of radiated pulses that a significant resonance, with a peak power of approximately 300 mu W, occurs at 500 GHz, which corresponds to the designed resonant frequency of the slot antenna. The saturation problem related to the output terahertz power that occurs with the traditional LTG-GaAs-based photonic-transmitters when operated under high external applied electrical fields (> 50 kV/cm) has been eliminated by the use of our device.
Effect of top electrode material on resistive switching properties of ZrO2 film memory devices
(2007-05-01)
Lin, Chih-Yang
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Wu, Chen-Yu
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Wu, Chung-Yi
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Lee, Tzyh-Cheang
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Yang, Fu-Liang
The influence of top electrode material on the resistive switching properties of ZrO2 -based memory film using Pt as a bottom electrode was investigated in this letter. In comparison with Pt/ZrO2/Pt and Al/ZrO2/Pt devices, the Ti/ZrO2/Pt device exhibits different resistive switching current-voltage (I-V) curve, which can be traced and reproduced by a dc voltage more than 1000 times only showing a little decrease of resistance ratio between high and low resistance states. Furthermore, the broad dispersions of resistive switching characteristics in the Pt/ZrO2/Pt and Al/ZrO2/Pt devices are generally observed during successive resistive switching, but those dispersions are suppressed by the device using Ti as a top electrode. The reliability results, such as cycling endurance and continuous readout test, are also presented. The write-read-erase-read operations can be over 104 cycles without degradation. No data loss is found upon successive readout after performing various endurance cycles.
Light-output enhancement of nano-roughened GaN laser lift-off light-emitting diodes formed by ICP dry etching
(2007-05-01)
Kao, Chih-Chiang
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Kuo, H. C.
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Yeh, K. F.
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Chu, J. T.
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Peng, W. L.
In this paper, we report the fabrication and characteristics of nano-roughened GaN laser lift-off (LLO) light-emitting diodes (LEDs) with different scale surface roughness. The surface roughness of devices was controlled by inductively coupled plasma reactive inn etching. Using this fabrication method to form nanoscaled roughness, the electrical property was almost not degraded. Furthermore, the light-output power and wall-plug efficiency of LLO LED could be both significantly enhanced about two times using this simple method.
On the architecture design and performance evaluation of a configurable Blueweb network
(2007-05-01)
Yu, Chih-Min
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Huang, Chia-Chi
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電信工程研究所
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Institute of Communications Engineering
Blueweb is a self-organizing Bluetooth-based multihop network equipped with a scatternet formation algorithm and a modified source routing protocol. In this paper, we first review the basic Blueweb network. Then we focus on a heuristic automatic configuration algorithm which can be used to partition a large-scale Blueweb network. This algorithm contains three main functional blocks including route master selection, node assignment, and subnet number decision. The route master selection block selects new route masters at a low computation cost. The node assignment block assigns nodes to each newly configured subnet in order to minimize the average route query cost. The subnet number decision block determines the optimal number of subnet which achieves the largest system performance improvement ratio at minimum operation cost. With these three functional blocks, optimal network configuration for Blueweb routing protocol can be determined. Computer simulations show that a configured Blueweb achieves higher network capacity than an unconfigured Blueweb.
Characterizing nonlinear rate-dependent behaviors of graphite/epoxy composites using a micromechanical approach
(2007-05-01)
Tsai, Jia-Lin
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Chen, Kuei-Han
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機械工程學系
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Department of Mechanical Engineering
This research aims to characterize the nonlinear rate-dependent behaviors of graphite/epoxy composites using micromechanical analysis. In this analysis, graphite fibers are considered as elastic solids, while the surrounding epoxy matrix exhibiting rate sensitivities are described using the three-parameter viscoplasticity model. By using Aboudi's generalized method of cells (GMC), the incremental form of the constitutive relations of the composites are expressed in terms of the constituent properties as well as the geometry parameters of the representative volume element. After a numerical iteration, the corresponding stress and strain relations of composites at different strain rates are generated. In order to verify the model predictions, off-axis graphite/epoxy composite specimens are tested at strain rates from 10(-4) to 550/s. For strain rates less than 1/s, the experiments are conducted using a hydraulic MTS machine, while high-strain-rate tests were carried out using a split Hopkinson pressure bar. Experimental results indicate that the stress and strain curves are quite sensitive to the strain rate; moreover, when the strain rates increase, the material stiffens. A comparison of model predictions with experimental results indicates that the rate-dependent behaviors of composites can be characterized effectively with the GMC model in conjunction with the viscoplastic properties of epoxy.
Unitizations of double-ring structure and Erbium-doped waveguide amplifier for stable and tunable fiber laser
(2007-05-01)
Chou, S.-Y.
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Yeh, C.-H.
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Chi, S.
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光電工程學系
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Department of Photonics
We propose and demonstrate experimentally a single longitudinal-mode (SLM) fiber double-ring laser using an Erbium-doped waveguide amplifier (EDWA), polarization controller (PC), and a fiber Fabry-Perot tunable filter (FFP-TF) into the ring cavity. In addition the output power side mode suppression ratio (SMSR), and the stabilities of power and wavelength of the laser also are investigated.
Effect of different gold nanoparticle sizes to build an electrical detection DNA between nanogap electrodes
(2007-05-01)
Chang, Tien-Li
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Lee, Ya-Wei
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Chen, Chun-Chi
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Ko, Fu-Hsiang
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材料科學與工程學系奈米科技碩博班
An experimental study for identifying DNA strands immobilized in the different particle sizes of gold nanoparticle (AuNP) between nanogap electrodes is presented. The nanogap-based electrics chip demonstrates a significant electrical property with a target DNA (DNA) concentration of 10 pM in the different particle sizes of AuNP to be analyzed in order to make the assay useful for an integrated lab-on-a-chip application system. The biochips with nanogap electrodes are fabricated by e-beam lithography (EBL). Different from traditional detection methods including polymerase chain reaction (PCR) based on assays which are expensive and time consuming for DNA strands research. By the method of electrical characterization, a change in measured current through the different particle sizes of AuNP can pave the way for further use in sensitive biomolecule detection study. (c) 2007 Published by Elsevier B.V.
Corner stress singularities in an FGM thin plate
(2007-05-01)
Huang, C. S.
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Chang, M. J.
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土木工程學系
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Department of Civil Engineering
Describing the behaviors of stress singularities correctly is essential for obtaining accurate numerical solutions of complicated problems with stress singularities. This analysis derives asymptotic solutions for functionally graded material (FGM) thin plates with geometrically induced stress singularities. The classical thin plate theory is used to establish the equilibrium equations for FGM thin plates. It is assumed that the Young's modulus varies along the thickness and Poisson's ratio is constant. The eigenfunction expansion method is employed to the equilibrium equations in terms of displacement components for an asymptotic analysis in the vicinity of a sharp corner. The characteristic equations for determining the stress singularity order at the corner vertex and the corresponding corner functions are explicitly given for different combinations of boundary conditions along the radial edges forming the sharp corner. The non-homogeneous elasticity properties are present only in the characteristic equations corresponding to boundary conditions involving simple support. Finally, the effects of material non-homogeneity following a power law on the stress singularity orders are thoroughly examined by showing the minimum real values of the roots of the characteristic equations varying with the material properties and vertex angle. (c) 2006 Elsevier Ltd. All rights reserved.
Effects of Fe substitution on the transport properties of the superconductor MgB2
(2007-05-01)
Gahtori, Bhasker
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Lal, Ratan
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Agarwal, S. K.
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Kuo, Y. K.
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Sivakumar, K. M.
A systematic study has been made on the effect of Fe substitution by means of resistivity, thermal conductivity, and Seebeck coefficient of the Mg1-xFexB2 superconductor involving 0%, 0.3%, 0.6%, 1.2%, and 3.0% Fe content. The superconducting transition has been found to be very sharp (similar to 0.2 K) for a pristine sample and substitution of Fe results in the decrease of T-C with the increase in the transition width. Thermal conductivity is found to decrease with Fe content in general, such that the shoulder present in the pristine sample tends to fade away with increasing Fe. An analysis has been made on the normal state resistivity in terms of a two-band model, and of the thermal conductivity in terms of the Wiedemann-Franz law and the lattice thermal conductivity, and the information obtained on the basis of this analysis has been discussed. Besides, the electronic density of states (DOS) near the Fermi level remains nearly unaffected upon Fe substitution, as evidenced by the Seebeck coefficient measurements. When compared with Mn, Fe behaves like a nonmagnetic element with a modest variation in T-C and on the other hand, the T-C depression is much stronger when compared with other elements like Al, Cu, etc. Therefore, the observed variation in T-C for the presently investigated concentrations of Fe is attributed to the specific nature of the given substituent element (Fe) in altering the phonon frequency and/or electron-phonon coupling strength rather than spin-flip scattering or change in DOS or disorder.
Low-complexity conjugate gradient algorithm for array code acquisition
(2007-05-01)
Yang, Hua-Lung
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Wu, Wen-Rong
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電信工程研究所
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Institute of Communications Engineering
An adaptive array code acquisition for direct-sequence/ code-division multiple access (DS/CDMA) systems was recently proposed to enhance the performance of the conventional correlator-based method. The scheme consists of an adaptive spatial and an adaptive temporal filter, and can simultaneously perform beamforming and code-delay estimation. Unfortunately, the scheme uses a least-mean-square (LMS) adaptive algorithm, and its convergence is slow. Although the recursive-least-squares (RLS) algorithm can be applied, the computational complexity will greatly increase. In this paper, we solve the dilemma with a low-complexity Conjugate gradient (LCG) algorithm, which can be considered as a special case of a modified conjugate gradient (MCG) algorithm. Unlike the original conjugate gradient (CG) algorithm developed for adaptive applications, the proposed method, exploiting the special structure inherent in the input correlation matrix, requires a low computational-complexity. It can be shown that the computational complexity of the proposed method is on the same order of the LMS algorithm. However, the convergence rate is improved significantly. Simulation results show that the performance of adaptive array code acquisition with the proposed CG algorithm is comparable to that with the original CG algorithm.
Using nonadditive fuzzy integral to assess performances of organizational transformation via communities of practice
(2007-05-01)
Chu, Mei-Tai
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Shyu, Joseph Z.
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Tzeng, Gwo-Hshiung
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Khosla, Rajiv
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科技管理研究所
Organizational transformations have been widely adopted by firms who wish to improve their competitive advantage to be better prepared to face external challenges. This research has chosen Communities of Practice (CoPs) as the subject of discussion for an assessment model to reform organizations that undertake CoPs for collective knowledge to enhance their core competencies. Given the interrelationships between criteria, this research uses the nonadditive fuzzy integral to develop a framework for the CoPs performance assessment. The purposes of this paper are to identify the key dimensions/criteria in the CoPs, to use fuzzy logic method to analyze the relative importance of each criterion, and to rank the criteria so that proper resources can be allocated while managing the CoPs. Through interviews with experts, four strategy alternatives and 16 criteria along four dimensions are generated. A survey of the CoPs practitioners is then conducted to compare the results of each criterion. The results will not only help organizations that intend to initiate changes via the CoPs activities to decide the ranking of their appraisal criteria, but it can also assist them in guiding the behavior of their staff while effectively monitoring and improving the performances of the CoPs.
Empirical measurement of sustainable welfare from the perspective of extended genuine savings
(2007-05-01)
Lin, Grace T. R.
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科技管理研究所
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Institute of Management of Technology
The original genuine savings (GS) model started from a concern mainly with unchanged capital: if the stocks of all forms of capital decline through time, welfare will decline, too, eventually leading to unsustainability. In other words, negative GS rates indicate unsustainability. In the context of sustainable development evaluation, however, income distribution and change of per capita welfare are two significant dimensions that the GS model has totally ignored and that need to be aptly incorporated into the model. This is because, behind a positive GS ratio, a country still faces other factors such as current income inequality and population growth, which may undermine the enjoyable sustainable welfare. This paper therefore adjusts the GS framework for these reflections and tests its application to the United Kingdom and Taiwan between 1970 and 1998. Our result shows that the United Kingdom has more depressed GS rates and more eminent sustainable welfare loss than Taiwan over the years. This result has been accordant with some prior research claims: many resource-rich countries have achieved slow or no long-term improvements in their standards of living. Copyright (c) 2007 John Wiley & Sons, Ltd and ERID Environment.
Magnetic and optical properties of isolated magnetite nanocrystals
(2007-05-01)
Shauo, Chang-Neng
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Chao, Chuen-Guang
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Wu, Tsien Ming
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Shy, Hsiou-Jeng
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材料科學與工程學系
Following preparation of isolated nano-sized magnetite particles in a low-concentration dispersant solution, this study investigated the magnetic and optical properties. Magnetic measurements indicated that the magnetite nanoparticles exhibited perfect superparamagnetism above the blocking temperature. Optical measurements revealed that the magnetic films exhibited good transmittance in the visible region and excellent UVB absorption. It has potential for use in optical applications (UVB-cut), such as sunglasses, heat mirror film and others.