Browsing by Issue Date, starting with "2003-03-01"

Now showing 1 - 20 of 72892

Using a conflict map as an instructional tool to change student alternative conceptions in simple series electric-circuits
(2003-03-01)
Tsai, CC
;
教育研究所
;
師資培育中心
;
Institute of Education
;
Center of Teacher Education
Research in science education has revealed that students have alternative conceptions when learning various domains in science. The conflict map uses a series of discrepant events, critical events, relevant scientific conceptions and perceptions to promote student conceptual change. This study was conducted to examine the effects of using a conflict map on eighth graders' conceptual change and ideational networks about simple series electric circuits. Through a quasi-experimental research design, 93 of Taiwan's eighth graders were assigned to a control group, receiving traditional instruction, while 97 eighth graders were assigned to an experimental group, which used a conflict map as an instructional tool. Research data gathered from a two-tier test revealed that the conflict map could help students overcome alternative conceptions about simple series electric circuits. Student interview data, analysed through a flow map method, also showed that the use of conflict map could help students construct greater, richer and more integrated ideational networks about electric circuits.
All-planar dual-mode asymmetric filters at Ka-band
(2003-03-01)
Chen, HC
;
Tzuang, CKC
;
電信工程研究所
;
Institute of Communications Engineering
All-planar dual-mode inductive asymmetric filters utilizing new planar microstrip to dielectric-loaded rectangular waveguide transitions at Ka-band were presented and built in this letter. The conventional, three-dimensional metallic rectangular waveguide dual-mode filters can be implemented into mature PCB technology with a much easier and lower-cost fabrication process on the basis of the all-planar feature of the transition. This work demonstrates two Ka-band filter examples with center frequency at 31 GHz and bandwidth at 1 GHz and 2 GHz. The measured minimum insertion loss of each case was, respectively, 2.68 and 1.12 dB, with greater than 10 dB return loss in the passband. Moreover, the measured side-band attenuation (near passband) is larger than 30 dB due to the transmission zeros at each side of the passband.
Effect of Zr/Ti ratios on characterization of Pb(ZrxTi1-x)O-3 thin films on Al2O3 buffered Si for one-transistor memory applications
(2003-03-01)
Sun, CL
;
Hsu, JJ
;
Chen, SY
;
Chin, A
;
材料科學與工程學系
Pb(ZrxTi1-)O-3 (PZT) thin films have been prepared on Al2O3/Si and PbTiO3/Al2O3/Si substrates, respectively. On Al2O3/Si substrates, Ti-rich PZT thin films had lower perovskite transformation temperatures than those of Zr-rich PZT films. Therefore, PbTiO3 was used as the seeding layer on Al2O3/Si to form a PbTiO3/Al2O3/Si substrate. The threshold voltage shift of a PZT(53/ 47)/PbTiO3/Al2O3/Si capacitor reaches 9 V with +/-10 V writing voltages, which is much larger than the 2 V of the PZT(0/100)/PbTiO3/Al2O3/Si capacitor. Different memory mechanisms in the capacitance-voltage characteristics of capacitors were further examined and discussed in this paper. (C) 2003 The Electrochemical Society.
An embedding algorithm for multiple watermarks
(2003-03-01)
Shieh, CS
;
Huang, HC
;
Wang, FH
;
Pan, JS
;
電子工程學系及電子研究所
A new algorithm for embedding several watermarks into the same original source is proposed in this paper. Instead of conventional watermark embedding algorithms that embed one watermark in one specific domain, we propose algorithms for embedding multiple watermarks into different compression domains to protect the ownership of the original images. The proposed schemes for embedding and extraction in different domains vary from the existing methods reported in the literature. Simulation results show their robustness for surviving intentional attacks and, hence, their effectiveness in protecting copyrights. They are also easy to implement.
THz radiation emission properties of multienergy arsenic-ion-implanted GaAs and semi-insulating GaAs based photoconductive antennas
(2003-03-01)
Liu, TA
;
Tani, M
;
Pan, CL
;
光電工程學系
;
Department of Photonics
We compare the performance of THz photoconductive (PC) emitter antennas fabricated on multienergy arsenic ion implanted GaAs (multi-GaAs:As+) and semi-insulating GaAs. High damage threshold biasing (>60 kV/cm) and large saturation optical-pumping power (similar to20 mW) for multi-GaAs:As+ based PC antennas are reported. Carrier mobility in the As ion implanted layer of GaAs:As+ was estimated to be about 150 cm(2)/V/s, which was comparable to that of. low,temperature GaAs. (C) 2003 American Institute of Physics.
Free-space electrooptic sampling of terahertz radiation from optically excited superconducting YBa2Cu3O7-delta thin films
(2003-03-01)
Lin, PI
;
Wu, KH
;
Juang, JY
;
Lin, JY
;
Uen, TM
The characteristics of photogenerated terahertz radiation from a current-biased superconducting YBa2Cu3O7-delta (YBCO) bow-tie antenna were investigated using a free-space electrooptic sampling technique. Picosecond electromagnetic pulses about 450 fs wide were obtained. The frequency spectrum derived by Fourier transforming the picosecond pulses spans over 0.1-4 THz. The dynamics of the quasi-particles optically induced by the ultrafast laser pulse primarily determines the performances of the transient terahertz radiation generated under different operating parameters. The results indicate a characteristic quasi-particle relaxation time of about 2.5 ps close to the critical temperature T-c, and a faster time at lower temperatures.
Narrow-band interference rejection in DS/CDMA systems using adaptive (QRD-LSL)-based nonlinear ACM interpolators
(2003-03-01)
Yuan, JT
;
Lee, JN
;
電信工程研究所
;
Institute of Communications Engineering
An Mth order adaptive lattice filter automatically generates all M of the outputs that would be provided by M separate transversal filters. This feature may effectively suppress the narrow-band interference (NBI) of either unknown or time-varying bandwidth (or number of frequency bands) in direct-sequence code-division multiple access systems for which the order of the interference rejection filter that achieves the optimal performance is unknown or constantly changing. Moreover, a lattice filter may significantly outperform its transversal counterpart in complex jamming environments in which the adaptive lattice filter must suppress multiple jammers, since each stage of a lattice filter adapts to suppress an orthogonal component of the NBI. This paper,develops a computationally efficient and numerically stable adaptive QR-decomposition-based least squares lattice (QRD-LSL)-based nonlinear approximate conditional mean interpolator to suppress NBI effectively. Simulation results demonstrate that both the signal-to-noise ratio improvements and the convergence rate achieved by the proposed interpolators outperform those of other existing prediction-based techniques.
Phase transformations in a Cu-14.2Al-7.8Ni alloy
(2003-03-01)
Chen, CH
;
Liu, TF
;
工學院
;
材料科學與工程學系
;
College of Engineering
In the as-quenched condition, the microstructure of the Cu-14.2 wt pct Al-7.8 wt pet Ni alloy was D0(3) phase containing extremely fine L-J precipitates with two variants. The L-J precipitate has an orthorhombic structure with lattice parameters a = 0.413 nm, b = 0.254 nm and c = 0.728 nm, which was a new phase found firstly by the present workers. The orientation relationship between the L-J phase and the matrix is (100)(L-J)//(011)(m), (010)(L-J)//(111) and (001)(L-J)//(211)(m). The rotation axis and rotation angle between two variants of the L-J phase are [021] and 90 deg. When the alloy was aged at 500 degreesC for short times and then quenched, gamma(2) particles started to precipitate within the D0(3) matrix at the aging temperature and the remaining D0(3) matrix would transform to gamma(1)' martensite during quenching. This is similar to that observed by other workers in a Cu-14Al-4Ni alloy. However, when the alloy was aged at 500 degreesC for longer times, the remaining D0(3) matrix would transform to a mixture of (B2 + alpha) phases. This feature has never been observed by other workers in the Cu-Al-Ni alloys.
Microlens array fabricated by excimer laser micromachining with gray-tone photolithography
(2003-03-01)
Tien, CH
;
Chien, YE
;
Chiu, Y
;
Shieh, HPD
;
光電工程學系
We demonstrate the fabrication of a refractive microlens array by using 249nm excimer laser micromachining with coded gray-tone mask photolithography. With pre-corrections to the nonlinear exposure process, the maximum deviation from the designed shape was below 5%. The fabricated hemispherical lens of 30 mum radius was used as a solid immersion lens (SIL) and combined with a 0.54 numerical aperture (NA) objective to achieve a 0.87 effective NA through the knife-edge scanning test. The. experimental results agreed with those of the simulation. Unlike the methods such as the thermal melting process, this one-step optical exposure method with a coded mask provides a relatively fast and cost-effective way to realize a microlens array in optical data storage, information processing, and optical interconnection applications.
A combination logic design for a high speed IEEE 802.11 MAC controller
(2003-03-01)
Li, RZ
;
Huang, SP
;
Lin, FS
;
Hong, MT
;
Chen, PN
In this paper, we propose a pure combinational logic design for the implementation of IEEE802.11 Medium Access Control (MAC) protocol, in contrast to firmware implementation based on an embedded micro-engine. In order to have a timely response, a Control Frame Handler is also included in our MAC controller. A further improvement for timely manipulation on the time-critical management frames (such as Beacon, ATIM and Probe Response) is subsequently developed in our revised edition. Equipped with a self-developed PCMCIA unit, the functions of our MAC controller have been verified using two Altera EPF 10K-100 ARC240-2 FPGAs in an on-line MAC-to-MAC data exchange fashion. Experimental results show that a pure combinational logic design can easily achieve a baseband-interfacing throughput of over-100Mbps with a cost-effect gate count of 21702.
Sources of sampling error for field measurement of nitric acid gas by a denuder system
(2003-03-01)
Bai, H
;
Lu, C
;
Chang, KF
;
Fang, GC
;
環境工程研究所
Field measurements of atmospheric HNO3 gas by a denuder system equipped with four annular denuders were conducted in Taiwan. The positive errors from interfering N-compounds as well as the negative errors from incompleteness of the apparent absorption of the HNO3 gas. as sampled by one NaCl-denuder, were quantitatively determined and the error sources were identified. It is found that the concentrations of positive error and negative error might cancel each other resulting in less difference between the measured and the true HNO3 concentrations. The atmospheric HNO3 concentration and the ambient temperature were the major factors that influence the degree of negative errors. The apparent absorption efficiency might decrease to less than 80% if the HNO3 gas concentration were lower than 0.3 mug m(-3) or the ambient temperature were over 28degreesC. There are also evidences showed that the positive errors were from both interfering N-containing gases and nitrate-containing particles. (C) 2003 Elsevier Science Ltd. All rights reserved.
Feasibility studies of magnetic particle-embedded carbon nanotubes for perpendicular recording media
(2003-03-01)
Kuo, CT
;
Lin, CH
;
Lo, AY
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Nano-sized magnetic particles were successfully used as the catalysts to synthesize magnetic metal-encapsulated carbon nanotubes (CNTs) or nanoparticles on Si wafers in a microwave plasma electron cyclotron resonance chemical vapor deposition (ECR-CVD) system with CH4 and/or H-2 as source gases. The magnetic catalyst materials, including Fe-Pt, Co-Pt, Nd2Fe14B, Fe and Fe-Ni, were first deposited on Si wafers by a physical vapor deposition (PVD) method, with subsequent plasma treatment for nanoparticle transformation. The main process parameters include catalyst materials, hydrogen plasma catalyst pretreatment and deposition temperature. For applications in magnetic media, the process has the following advantages: perpendicularly aligned CNTs or nanoparticles; tip-growth CNTs; well-distributed magnetic particles; detectable magnetic field in each particle; high tube number density (up to 134 Gtubes/inch(2) for Fe-assisted CNTs); favorable catalyst size; higher shape and induced anisotropy; and nanostructures that can be manipulated. The catalyst particle sizes of Fe, Nb2Fe14B and Fe-Pt (35-40 mn in diameter) are uniform and greater than but close to the critical optimum size or single domain size, which favor a higher coercive force. The greatest coercive force can reach 750 Oe for Fe-assisted CNTs at a deposition temperature of 715 degreesC, which is comparable with values reported in the literature. The coercive force difference between the vertical and horizontal directions can reach 300 Oe for Fe-assisted CNTs, and 355 Oe for Nb2Fe14B-assisted CNTs. (C) 2002 Elsevier Science B.V. All rights reserved.
A fast multicast IP-rOuting lookup scheme
(2003-03-01)
Huang, KM
;
Chang, CJ
;
電信工程研究所
;
Institute of Communications Engineering
This letter proposes a fast multicast IP-routing lookup scheme, which adopts a compression bit map conception for forwarding information. The proposed scheme-can achieve fast address lookup speed and reasonable forwarding table size.
A parallel block scaled gradient method with decentralized step-size for block additive unconstrained optimization problems of large distributed systems
(2003-03-01)
Lin, SY
;
Lin, SS
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper, we propose a modified parallel block scaled gradient method for solving block additive unconstrained optimization problems of large distributed systems. Our method makes two major modifications to the typical parallel block scaled gradient method: First, we include a pre-processing step which reduces the computational time; second, we propose a decentralized Armijo-type step-size rule. This rule circumvents the difficulty of determining a step-size in a distributed computing environment and enables the proposed parallel algorithm to execute in a distributed computer network with a limited amount of data transfer. We have applied our method to the weighted-least-square problems of power system state estimation and demonstrated the convergence of our method by testing numerous examples on a PC network. The speedup ratio of the distributed version of our method tends to increase proportionally with the number of subsystems (or computers).
A design-for-verification technique for functional pattern reduction
(2003-03-01)
Liu, CNJ
;
Chen, IL
;
Jou, JY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This technique reduces the number of required functional patterns by first defining conditions for hard-to-control (HTC) code in a hardware-description-language design and then using an algorithm to detect such code automatically. A second algorithm eliminates these HTC points by selecting a minimum number of nodes for control point insertion.
An investigation of magnetic field effects on energy states for nanoscale InAs/GaAs quantum rings and dots
(2003-03-01)
Li, YM
;
Lu, HM
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
In this paper, we investigate the electron-hole energy states and energy gap in three-dimensional (313) InAs/GaAs quantum rings and dots with different shapes under external magnetic fields. Our realistic model formulation includes: (i) the effective mass Hamiltonian in non-parabolic approximation for electrons, (ii) the effective mass Hamiltonian in parabolic approximation for holes, (iii) the position- and energy-dependent quasi-particle effective mass approximation for electrons, (iv) the finite hard wall confinement potential, and (v) the Ben Daniel-Duke boundary conditions. To solve the 3D non-linear problem without any fitting parameters, we have applied the nonlinear iterative method to obtain self-consistent solutions. Due to the penetration of applied magnetic fields into torus ring region, for ellipsoidal- and rectangular-shaped quantum rings we find nonperiodical oscillations of the energy gap between the lowest electron and hole states as a function of external magnetic fields. The nonperiodical oscillation is different from 1D periodical argument and strongly dependent on structure shape and size. The result is useful to study magneto-optical properties of the nanoscale quantum rings and dots.
Wide range work function modulation of binary alloys for MOSFET application
(2003-03-01)
Tsui, BY
;
Huang, CF
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper explores the characteristics of the binary alloys Th-Pt and Ta-Ti for gate electrode application. With a proper composition of high and low work function metals, the work function of the metal alloys can be modulated from 4.16 eV to 5.05 eV continuously. The alloys show good thermal stability and inner chemical activity on both silicon dioxide and hafnium dioxide. Thermal stress generated from the alloy film increases interface state density and hence effective oxide charges. This problem can be greatly reduced with W/Ta-Pt stack structure, where W acts as the main conducting metal and Ta-Pt acts as work function control metal. All of these properties make them suitable for use in all device applications.
Fine-grained protein fold assignment by support vector machines using generalized npeptide coding schemes and jury voting from multiple-parameter sets
(2003-03-01)
Yu, CS
;
Wang, JY
;
Yang, JM
;
Lyu, PC
;
Lin, CJ
In the coarse-grained fold assignment of major protein classes, such as all-alpha, all-beta, alpha + beta, alpha/beta proteins, one can easily achieve high prediction accuracy from primary amino acid sequences. However, the fine-grained assignment of folds, such as those defined in the Structural Classification of Proteins (SCOP) database, presents a challenge due to the larger amount of folds available. Recent study yielded reasonable prediction accuracy of 56.0% on an independent set of 27 most populated folds. In this communication, we apply the support vector machine (SVM) method, using a combination of protein descriptors based on the properties derived from the composition of n-peptide and jury voting, to the fine-grained fold prediction, and are able to achieve an overall prediction accuracy of 69.6% on the same independent set-significantly higher than the previous results. On 10-fold cross-validation, we obtained a prediction accuracy of 65.3%. Our results show that SVM coupled with suitable global sequence-coding schemes can significantly improve the fine-grained fold prediction. Our approach should be useful in structure prediction and modeling. (C) 2003 Wiley-Liss, Inc.
A novel approach of backup path reservation for survivable high-speed networks
(2003-03-01)
Lo, CC
;
Chuang, BW
;
交大名義發表
;
National Chiao Tung University
For high-speed networks, a restoration mechanism based on backup path provides a, means for assuring their survivability. In this article, we propose a two-phase BP reservation mechanism for high-speed networks. In the admission phase, a pair of working path and backup path is selected from the provisioned sets of WPs and BPs. In the adjustment phase, if backup capacity utilization exceeds the preset threshold, BP assignments are rearranged to optimize the usage of backup capacity. A mathematical model is formulated to verify the quality of the optimized solutions. Computational experiments indicate that the proposed mechanism significantly reduces the consumption of backup capacity while still maintaining a high degree of survivability. Moreover, experiments show that the optimized solutions obtained are on average within 3.6 percent of optimal.
Fuzzy inductive learning strategies
(2003-03-01)
Wang, CH
;
Tsai, CR
;
Hong, TP
;
Tseng, SS
;
資訊工程學系
In real applications, data provided to a learning system usually contain linguistic information which greatly influences concept descriptions derived by conventional inductive learning methods. Design of learning methods for working with vague data is thus very important. In this paper, we apply fuzzy set concepts to machine learning to solve this problem. A fuzzy learning algorithm based on the AQR learning strategy is proposed to manage linguistic information. The proposed learning algorithm generates fuzzy linguistic rules from "soft" instances. Experiments on the Sports and the Iris Flower classification problems are presented to compare the accuracy of the proposed algorithm with those of some other learning algorithms. Experimental results show that the rules derived from our approach are simpler and yield higher accuracy than those from some other learning algorithms.