Browsing by Issue Date, starting with "2001-02-04"

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聽荷說法
(2001-02-04)
楊顯榮
Saturation of electron dephasing in three-dimensional polycrystalline disordered metals
(2001-02-05)
Lin, JJ
;
Kao, LY
;
物理研究所
;
Institute of Physics
We have systematically investigated the low-temperature electron dephasing times tau (phi) in more than 40 three-dimensional polycrystalline impure metals with distinct material characteristics. In all cases, a saturation of the dephasing time is observed below about a (few) degree(s) Kelvin, depending on samples. The value of the saturated dephasing time tau (0) [= tau (phi)(T --> 0 K)] falls basically in the range 0.005 to 0.5 ns for all samples. Particularly, we find that so scales with the electron diffusion constant D as tau (0) similar to D-alpha, with alpha close to or slightly larger than 1, for over two decades of D from about 0.1 to 10 cm(2) s(-1). Our observation implies an essentially constant saturated dephasing length of rootD tau (0) similar to 1000 Angstrom in three-dimensional polycrystalline disordered metals. A complete theoretical explanation is not yet available.
Angular distribution of electrons elastically backscattered from amorphous overlayer systems
(2001-02-10)
Kwei, CM
;
Tsai, SS
;
Tung, CJ
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Monte Carlo calculations have been performed of the angular distribution of electrons elastically backscattered from amorphous overlayer systems composed of thin copper films and semi-infinite silicon substrates. These calculations showed that the angular distribution of the elastically reflected intensity was dependent on film thickness and electron energy. They also showed that elastically backscattered electrons were due substantially to one, two and three scatterings with single-scattering events contributing about half of the intensity. Based on these findings, we have derived a formula for the contribution from single-scattering events to the angular distribution of the elastically reflected intensity. Combining this formula and the Pi-approximation for multiple scattering, we were able to construct an analytic formula for the angular distribution of electrons elastically backscattered from overlayer systems. Results from this approach were in good agreement with those computed using Monte Carlo simulations. (C) 2001 Elsevier Science B.V, All rights reserved.
Characteristics of monolithically integrated two-wavelength laser diodes with aluminum-free active layers
(2001-02-12)
Lu, TC
;
Fu, R
;
Shieh, HM
;
Huang, KJ
;
Wang, SC
A two-wavelength integrated laser diode (TWINLD) with aluminum-free active areas (AAA) has been realized by monolithically combining two different laser material structures in a single chip utilizing the metalorganic chemical vapor deposition growth and regrowth techniques. The single TWINLD chip comprises two ridge wave-guide lasers, one is an InGaP/InGaAlP material structure for a 650 nm red laser, and another is an InGaAsP/AlGaAs material structure with AAA for a 780 nm infrared laser. The chip geometry is 300 mum long and 300 mum wide with a separation of 150 mum between two laser emission spots. The ridge widths are 3.5 and 2 mum for the red and IR laser, respectively, and both lasers emit a single transverse mode with a threshold current of 12 mA for a 650 nm laser and 14 mA for a 780 nm laser under continuous wave operation condition. (C) 2001 American Institute of Physics.
Vibration analysis of a rotating Timoshenko beam
(2001-02-15)
Lin, SC
;
Hsiao, KM
;
機械工程學系
;
Department of Mechanical Engineering
The governing equations for linear vibration of a rotating Timoshenko beam are derived by the d'Alembert principle and the virtual work principle. In order to capture all inertia effect and coupling between extensional and flexural deformation, the consistent linearization of the fully geometrically non-linear beam theory is used. The effect of Coriolis force on the natural frequency of the rotating beam is considered. A method based on the power series solution is proposed to solve the natural frequency of the rotating Timoshenko beam. Numerical examples are studied to verify the accuracy of the proposed method and to investigate the effect of Coriolis force on the natural frequency of rotating beams with different angular velocity, hub radius and slenderness ratio. (C) 2001 Academic Press.
Diode-end-pumped passively mode-locked high-power Nd : YVO4 laser with a relaxed saturable Bragg reflector
(2001-02-15)
Chen, YF
;
Tsai, SW
;
Lan, YP
;
Wang, SC
;
Huang, KF
We demonstrate a high-power passively mode-locked Nd:YVO4 laser that uses a saturable Bragg reflector (SBR) with strain relaxation. 23.5 W of average power with similar to 21.5-ps cw mode-locked pulse trains was generated at a 50-W pump power. Experimental results show that appropriate strain relaxation in the SBR makes the mode-locking operation less sensitive to temperature variation. (C) 2001 Optical Society of America OCIS codes: 140.3530, 140.3580, 140.4050, 140.7090, 160.6000.
Hydrogenic impurity in multilayered quantum wires
(2001-02-15)
Hsieh, CY
;
Chuu, DS
;
電子物理學系
;
Department of Electrophysics
The binding energy of the ground state of a hydrogenic impurity located at the center of a multilayered quantum wire (MLQW) is studied within the framework of the effective-mass approximation. The MLQW consists of a core wire (GaAs) coated by a cylindrical shell (Ga1-xAlxAs) and then embedded in the bulk (Ga1-yAlyAs). The calculation was performed by using a trial wave function. To make a comparison, the ground and excited states (1s, 2p, and 3d states) binding energies of a hydrogenic impurity located at the center of a single-layered quantum wire (QW) are also calculated. It is found for small wire radius, the ground-state binding energy of the hydrogenic impurity located at the center of a MLQW behaves very differently from that of a single-layered QW. (C) 2001 American Institute of Physics.
Feasibility study on a contact-less direct thermal printing with electrothermal SPICE simulation
(2001-02-15)
Chen, YM
;
Shie, JS
;
光電工程學系
;
Department of Photonics
A new concept for making contact-less direct thermal printing for facsimile is proposed and evaluated in this article. The concept is based on the fact that air molecules can be a good thermal conduction medium capable of transferring the heat efficiently from a micro-heater to a thermal marking paper, if both in close proximity, The micro-heater can be made of single-crystal silicon by micromachining technology, hence the associated CMOS driving circuits can be fabricated monolithically with the heater to exempt from the tedious work of numerous wire bonding. An illustrative device of integrated micro-heater array in 200 dpi resolution has been fabricated, characterized and evaluated for the new printing application. A thermal model of the device has also been set up and studied of its dynamic behaviors using the existing electrothermal SPICE package. The result of simulations indicates that efficient energy transfer of more than 40%, much better than the conventional performance, can be achieved with a practical 1 mum air gap. This and other additional advantages described in the article indicates that, in principle, the contact-less direct thermal printing is feasible and the monolithic silicon micro-heater array can be an excellent device for this application. (C) 2001 Elsevier Science B.V. All rights reserved.
The influence of washing and calcination condition on urea-derived ceria-yttria-doped tetragonal zirconia powders
(2001-02-15)
Lin, JD
;
Duh, JG
;
Chiou, BS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The influence of washing and calcination conditions on the powder characteristics of urea-derived ceria-yttria-doped tetragonal zirconia powders (Ce-Y-TZP) ceramics are studied. The use of urea hydrolysis followed by acetone-toluene-acetone (ATA) washing can produce a finer and more sinterable Ce-Y-TZP powder as compared to that washed by alcohol. It is observed that as the calcination temperature is raised to 800 degreesC for 2 h, the sintered density achieves the highest value regardless of the increase of monoclinic content in as-derived powders. The higher the calcination temperature, the more the monoclinic content. The transformability of tetragonal phase is related to the A, temperature and tetragonality. The monoclinic content in as-derived powders after calcination and ball-milling processes is proportional to the A, temperature and tetragonality of tetragonal phase. (C) 2001 Elsevier Science B.V. All rights reserved.
Non-linear dynamic analysis and control of chaos for a two-degrees-of-freedom rigid body with vibrating support
(2001-02-15)
Ge, ZM
;
Tsen, PC
;
機械工程學系
;
Department of Mechanical Engineering
The dynamic behaviors of a two-degrees-of-freedom rigid body with vibrating support are studied in this paper. Both analytical and computational results are employed to obtain the characteristics of the system. By using the Lyapunov direct method the conditions of stability of the relative equilibrium position can be determined. The incremental harmonic balance method (II-IB) is used to find the stable and unstable periodic solutions for the: strongly non-linear system. By applying various numerical results such as phase plane, Poincare map, time history and power spectrum analysis, a variety of periodic solutions and the phenomena of the chaotic motion is presented. The effects of the changes of parameters in the system can he found in the bifurcation diagrams. Further, the chaotic behavior is verified by using Lyapunov exponents. The modified interpolated cell mapping method (MICM) is used to study the basins of attraction of periodic attractors and the fractal structure. Besides, additions of a constant torque, a periodic torque. addition of dither signals, delayed feedback control, adaptive control. and bang-bang control are used to control the chaos phenomena effectively. (C) 2001 Academic Press.
Microstructure effects on quantum efficiency in PtSi/p-Si(100) Schottky barrier detector
(2001-02-15)
Horng, GJ
;
Chang, CY
;
Chang, T
;
Ho, C
;
Wu, CS
The microstructure effects on the performance of the PtSi Schottky barrier detector (SBD) have been investigated in detail. The growth temperatures were ranged from 350 to 550 degreesC. The thickness of the PtSi film measured by high resolution transmission electron microscopy (HRTEM) is around 4 nm. The electron diffraction pattern shows an intermingling of both (1 (1) over bar 0) and (I (2) over bar 1) orientations when the PtSi film is formed at 350 degreesC. However, the diffraction patterns show only (1 (2) over bar1) orientation when the PtSi films are formed above 450 degreesC. It was found that the electrical barrier height of the Schottky barrier detector formed at 350 degreesC is about 0.02 eV higher than that formed above 450 degreesC. The microstructure of the PtSi film does not change even though the formation temperature is further increased to 550 degreesC. Nevertheless, the higher the formation temperature, the larger is the grain size. It was also observed that the grain size does not change the electrical barrier height. However, the quantum efficiency of the detector is much higher if the grain size is larger. The results indicate that the quantum efficiency of the detector can be improved if the PtSi film has (1 2 1) orientation and larger grain size. (C) 2001 Elsevier Science B.V. All rights reserved.
Nano-oxidation of silicon nitride films with an atomic force microscope: Chemical mapping, kinetics, and applications
(2001-02-15)
Chien, FSS
;
Chou, YC
;
Chen, TT
;
Hsieh, WF
;
Chao, TS
We demonstrate that local oxidation of silicon nitride films deposited on conductive substrates with a conductive-probe atomic force microscope (AFM) is a very promising approach for nanofabrication. Scanning Auger microscopy and spectroscopy are employed to verify the chemical changes after AFM-induced oxidation. Furthermore, the growth kinetics are found to have a logarithmic relationship of oxide height versus pulse duration [h proportional to ln(t/t(0))]. In contrast to rather slow thermal oxidation process, AFM-induced oxidation on silicon nitride has an anomalously high initial oxidation rate (similar to 30 000 nm/s at 10 V) and a small onset time t(0) (similar to 10 mus). As for the applications in ultrahigh-density recording, an oxide dot array (similar to 100 Gbit/in.(2)) produced by this process is demonstrated. The nitride film patterned by AFM can be utilized as an etching mask to fabricate "subtractive" silicon nanostructures, due to the large etching selectivity of Si3N4:SiO2:Si in various etchants. With this method, which is entirely compatible with the existing microelectronic processes, synthesis of ultrahigh packing density and ordered nanostructures could become readily achievable. (C) 2001 American Institute of Physics.
A reversing traversal algorithm to predict deleting node for the optimal k-node set reliability with capacity constraint of distributed systems
(2001-02-15)
Yeh, YS
;
Chiu, CC
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
A k-node set reliability with capacity constraint is defined as the probability that a set, K, of nodes is connected in a distributed system and the total capacity of the nodes in K is sufficient under a given capacity. This is generally an NP-hard problem. For reducing computational time, a reasonable k-node set within a given capacity constraint must be determined by an efficient algorithm. In this work, we propose a reversing traversal method to derive a k-node set under capacity constraint having an approximate solution. Initially, the set K is assigned to all the nodes in a system. The proposed algorithm uses an objective function to evaluate the fitness value of each node in K and predict a deleting node, which is not a critical node, in K with minimal fitness value. After deleting the node, the fitness value of each node that is adjacent to the deleted node is tuned. The above two processes are repeated until the total capacity of the nodes in each subset of the set K does not satisfy the capacity constraint. In our simulation, the proposed method can obtain an exact solution above 90%. When a sub-optimal solution is obtained, the average deviation from an exact solution is under 0.0033. Computational results demonstrate that the proposed algorithm is efficient in execution time and effective for obtaining an optimal k-node set with capacity constraint. (C) 2001 Elsevier Science B.V. All rights reserved.
Fuzzy approaches for fault diagnosis of transformers
(2001-02-16)
Chen, AP
;
Lin, CC
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
Dissolved gas analysis has been used as a diagnostic method to determine the conditions of transformers for a long time. The criteria used in dissolved gas analysis are based on crisp value norms. Due to the dichotomous nature of crisp criteria, transformers with similar gas-in-oil conditions may lead to very different conclusions of diagnosis especially when the gas concentrations are around the crisp norms. To deal with this problem, gas-in-oil data of failed transformers were collected and treated in order to obtain the membership functions of fault patterns using a fuzzy clustering method. All crisp norms are fuzzified to linguistic variables and diagnostic rules are transformed into fuzzy rules. A fuzzy system originally proposed by Takagi and Sugeno is used to combine the rules and the fuzzy conditions of transformers to obtain the final diagnostic results. It is shown that the diagnosing results from the combination of several simple fuzzy approaches are much better than traditional methods especially for transformers which have gas-in-oil conditions around the crisp norms. (C) 2001 Elsevier Science B.V. All rights reserved.
Using fuzzy set to model the stability region on the bicycle derailleur system
(2001-02-16)
Lin, TY
;
Tseng, CH
;
機械工程學系
;
Department of Mechanical Engineering
In designing the bicycle derailleur system, designers can use the results from the "stability region test" to determine many parameters. Experimentation is the most accurate way to find a stability region because it is very difficult to derive a mathematical expression for the stability region. In this paper, a fuzzy set is used to determine the stability region of the bicycle derailleur system. The database of the fuzzy set model is created from the experimental results. The relationship between the experimental data and fuzzy set model will be described. Many properties of the stability region can be derived from this model. The existence of the stability region, the reduction of experimental noise, the determination of indexed points, and other techniques in designing an indexed derailleur system will also be introduced. This approach can simplify the previous representations of the stability region and the mechanical characteristics. Finally, a case study of the market product is presented. (C) 2001 Elsevier Science B.V. All rights reserved.
Fuzzy ARIMA model for forecasting the foreign exchange market
(2001-02-16)
Tseng, FM
;
Tzeng, GH
;
Yu, HC
;
Yuan, BJC
;
管理學院
Considering the time-series ARTMA (p,d,q) model and fuzzy regression model, this paper develops a fuzzy ARIMA (FARIMA) model and applies it to forecasting the exchange rate of NT dollars to US dollars. This model includes interval models with interval parameters and the possibility distribution of future values is provided by FARIMA. This model makes it possible for decision makers to forecast the best- and worst-possible situations based on fewer observations than the ARIMA model. (C) 2001 Elsevier Science B.V. All rights reserved.
Low dark current quantum-dot infrared photodetectors with an AlGaAs current blocking layer
(2001-02-19)
Wang, SY
;
Lin, SD
;
Wu, HW
;
Lee, CP
;
電子工程學系及電子研究所
Low dark current InAs/GaAs quantum-dot infrared photodetectors (QDIPs) are demonstrated. The dark current is reduced by over three orders of magnitude by using a thin AlGaAs current blocking layer. This thin AlGaAs layer reduces the dark current much more than the response signal. The responsivity at 0.5 V is 0.08 A/W with a peak detection wavelength at 6.5 mum. The corresponding detectivity is 2.5x10(9) cm Hz(1/2)/W-1/2, which is the highest detectivity reported for a QDIP at 77 K. (C) 2001 American Institute of Physics.
請問東阿王曹子健先生
(2001-02-22)
管管
管管作品十三首
(2001-02-25)
管管
管管作品十三首
(2001-02-25)
管管