Browsing by Issue Date, starting with "1999-10-31"

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詩社四十五周年茶會創世紀喜臨門
(1999-10-31)
林英喆
A minimum output burstiness traffic scheduling algorithm
(1999-11-01)
Kuo, YE
;
Lee, TH
;
傳播研究所
;
電信工程研究所
;
Institute of Communication Studies
In this paper, we present a traffic scheduling algorithm, called the Delay-Bound Monotonic with Average Rate Reservation (DM/ARR), which generates minimum output burstiness streams. We assume that connection i is policed by the leaky bucket algorithm with parameters (sigma(i), sigma(i)) where sigma(i) is the bucket size (or burstiness) and p(i) is the leaky rate. Compared with the totally isolated scheme where connection i is allocated a bandwidth r(i) = max{sigma(i)/d(i),rho(i)} (d(i) is the delay bound requirement of connection i), the DM/ARR algorithm has a better performance in the sense that it has a larger admission region. We prove that. among all possible scheduling algorithms that satisfy the delay bound requirements of established connections, DM/ARR results in the minimum output burstiness. This is important because a smaller burstiness implies a smoother traffic and thus the receiver (or next switch node in a multihop network) can handle it more easily. Numerical results show that the admission region of the DM/ARR algorithm is close to that of the earliest deadline first [1] algorithm. A packetized version is studied for ATM networks.
Bond length order parameter of conjugated polymers
(1999-11-01)
Lai, CM
;
Meng, HF
;
物理研究所
;
Institute of Physics
It is usually assumed that the ground state lattice configuration of polyacetylene is a dimerized chain. We found that the energy can be further reduced by an overall chain length contraction, which leads to a new bond length order parameter, in addition to the well-known bond alternation order parameter. For quasi-particles like solitons and polarons, these two order parameters are coupled with the electron wave functions and vary in space. We generalize the Takayama-Liu-Maki equations in the continuum limit to incorporate this new order parameter. Significant modifications are found for the polaron solution. Polyacene, a ladder polymer, is also studied with the inclusion of the bond length order parameter. The ground state is predicted to be a non-alternating structure, with zero energy gap and unusually high electric conductivity. (C) 1999 Elsevier Science B.V. All rights reserved.
On the properties of the reduction-by-composition LMS algorithm
(1999-11-01)
Chen, SG
;
Kao, YA
;
Chen, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The recently proposed low-complexity reduction-by-composition least-mean-square (LMS) algorithm (RCLMS) costs only half multiplications compared to that of the conventional direct-form LMS algorithm (DLMS), This work intends to characterize its properties and conditions for mean and mean-square convergence. Closed-form mean-square error (MSE) as a function of the LMS step-size mu and an extra compensation step-size alpha are derived, which are slightly larger than that of the DLMS algorithm. It is shown, when mu is small enough and alpha is properly chosen, the RCLMS algorithm has comparable performance to that of the DLMS algorithm. Simple working rules and ranges for alpha and mu to make such comparability are provided. For the algorithm to converge, a tight hound for alpha is also derived. The derived properties and conditions are verified by simulations.
Internet-based hierarchical floorplan design
(1999-11-01)
Lin, JH
;
Jou, JY
;
Jiang, IHR
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
With the proliferation of the transistor count in VLSI design, more and more design groups try to figure out an efficient way to combine their designs. The Internet features distributed computing and resource sharing. Consequently, a hierarchical design can adequately be solved in the Internet environment. In this paper, we demonstrate the facilitation of the Internet environment by solving the area minimization floorplan problem. We propose the RMG algorithm taking advantage of the Internet. Based on the model of transfer latencies, the RMG algorithm reduces the computing time by shortening the critical path in the floorplan tree. Our experimental results show that the Internet is suitable for Electronic Design Automation (EDA).
Directional spectrum analysis and statistics obtained from ERS-1 SAR wave images
(1999-11-01)
Kuo, YY
;
Leu, LG
;
Kao, IL
;
土木工程學系
;
Department of Civil Engineering
This work examines ERS-1 (the first European Remote Sensing Satellite) SAR (Synthetic Aperture Radar) water surface wave images over Hualien of Taiwan, indicating that the variation of SAR signals in space domain is similar to in situ wave data's in time domain. Some statistical properties of SAR data are investigated. The Rayleigh distribution function closely corresponds with the histogram of wave heights, but the Gaussian one cannot for water surface displacements. Evidence reveals that SAR wave signals do not respond well to actual ocean waves effectively. As wave spectral analysis of available SAR data reveals, the appropriate sample size of SAR wave image, sampling average, and moving average should be taken carefully to accurately confirm directional power spectra. Moreover, SAR spectra are compared with in situ ones, confirming that peak frequencies correlate well and wave directions approximately agree with each other. Some differences between both spectral shapes remain somewhat unclear and require further study. Nevertheless, in this study, ERS-1 SAR power spectra verified the feasibility of deriving an appropriate dominant wave direction and peak frequency. (C) 1998 Elsevier Science Ltd. All rights reserved.
Excitation of the NO molecule by chirped infrared laser pulses
(1999-11-01)
Lin, JT
;
Hayashi, M
;
Lin, SH
;
Jiang, TF
;
物理研究所
To explore the insights of recent experiments on the excitation of the NO molecule by chirped subpicosecond IR pulses, a corresponding theoretical study is presented. The agreements between experimental and theoretical results show the importance of the full-dimensional quantum-mechanical calculation. [S1050-2947(99)04711-3].
Time-dependent Ginzburg-Landau equation for d(x2-y2)-wave superconductors: Hall effect in the low field regime
(1999-11-01)
Yang, TJ
;
Dai, MC
;
電子物理學系
;
Department of Electrophysics
The Hall effect is studied by using a phenomenological time-dependent Ginzburg-Landau equation with mixing of s-and d-wave components in d(x)2-(y)2-wave superconductors within a low field regime. An equation of motion for a single vortex is derived and the Hall angle is obtained under an external driving current along the crystal axis. We find that not only the imaginary parts of s- and d-wave relaxation time but also the mixed gradient terms may change the sign of the Hall effect.
Generation of coherent cw-terahertz radiation using a tunable dual-wavelength external cavity laser diode
(1999-11-01)
Gu, P
;
Chang, F
;
Tani, M
;
Sakai, K
;
Pan, CL
A tunable dual-wavelength external cavity laser diode (2-lambda-ECL) was used to generate tunable coherent cw-terahertz (THz) radiation by photomixing in a biased photoconductive antenna fabricated on a low-temperature-grown (LTG)-GaAs film. The 2-lambda-ECL oscillated at the two output modes simultaneously with a frequency separation from 250 GHz to 2.1 THz in the same cavity. We demonstrated that the frequency of the emitted THz radiation corresponded to the difference frequency between the two modes of the diode laser. The tunable 2-lambda-ECL, due to its compact design and ease of optical alignment, is a promising laser source for the generation of tunable cw-THz radiation by photomixing.
Modulation transfer function of a liquid crystal spatial light modulator
(1999-11-01)
Hsieh, ML
;
Hsu, KY
;
Paek, EG
;
Wilson, CL
;
光電工程學系
The modulation transfer function (MTF) of a pixelated liquid crystal spatial light modulator (LC-SLM) has been derived as a function of the fill factor. Based on the formula, we have investigated the dependence of the MTF on the orientations and spatial frequency of the input patterns. Furthermore, we have proposed and demonstrated a method for improving the MTF of a LC-SLM. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
Effects of methyl silsesquioxane electron-beam curing on device characteristics of logic and four-transistor static random-access memory
(1999-11-01)
Lin, CF
;
Tung, IC
;
Feng, MS
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The as-spun methyl silsesquioxane (MSQ) film cured by an electron beam (e-beam) did not show water absorption after a five-day exposure to ambient ail: MSQ was applied to the triple-level metal (TLM) Logic and double-level metal (DLM) foul-transistor (4-T) static random-access memory (SRAM) as intermetal dielectric by means of the non-etchback process. When MSQ treatment conditions were properly controlled, the top layer of the as-spun films was cured by e-beam exposure while the bottom layer of the film was thermally cured for a short period of time. The as-cured MSQ offered good surface planarity. In addition, neither via poisoning, bowing nor cracking was observed. The results showed that, by the application of the e-beam cured MSQ in the fabrication of intel connect structures, the cache time of DLM 4-T SRAM could be improved to 10 ns compared with 11.5 ns for the SRAM fabricated using the conventional furnace cure spin-on-glass (SOG) process (400 degrees C annealing for one hour). E-beam exposure has little effect on n-channel metal-oxide-semiconductor (NMOS) device characteristics, such as saturation current threshold voltage and channel length. In contrast, e-beam exposure has a significant effect on p-channel MOS (PMOS) device characteristics, resulting in a shift of the threshold voltage as well as an increase in the channel length. It is notable that the e-beam exposure almost did not affect NMOS device characteristics in the 4-T SRAM, since the polysilicon load resistor could serve as a shield against electron bombardment. In such a case, the resistance of the polysilicon load resistor was significantly decreased.
Adaptive predictor based on maximally flat halfband filter in lifting scheme
(1999-11-01)
Ho, WJ
;
Chang, WT
;
電信工程研究所
;
Institute of Communications Engineering
For the complex short time-varying signals, a high-order predictor does not always yield good performance. For this, we investigate the use of a short-order adaptive predictor. Since the maximally flat filters are the optimal predictors for polynomial signal prediction, the adaptation is based on the combination of a set of maximally flat filters. For compression efficiency, the dynamic ranges of the weighting variables are specially considered. For this, based on the Bernstein filters, another form to represent the weighting variables is used. These two sets of weighting coefficients can be transformed into each other with a simple linear transform. Thus, the adaptation can be made in both the time domain and the frequency domain. For block-based image coding, the least square criterion is used to derive the weighting coefficients. Experimental results show that the adaptive predictor performs better than the SSP transform, the median edge detector (MED), and the gradient adjusted predictor (GAP).
Secure communication mechanisms for GSM networks
(1999-11-01)
Lo, CC
;
Chen, YJ
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
With the advance of wireless communications technology, mobile communications has become more convenient than ever. However, because of the openness of wireless communications, how to protect the privacy between communicating parties is becoming a very important issue. In this paper, we focus on the security of the Global System for Mobile communication (GSM) networks. A secure communication architecture for the GSM network is proposed. In the proposed architecture, we use public-key cryptography for user authentication and stream cipher for message encryption and decryption. An authentication protocol and a key generation method are presented in conjunction with the proposed architecture. Cryptanalysis and operational analysis show that the authentication protocol is secure and efficient. Simulation results indicate that the key generation method can always produce key strings of evenly distributed 0's and 1's and with infinite period.
The novel precleaning treatment for selective tungsten chemical vapor deposition
(1999-11-01)
Chang, TC
;
Mor, YS
;
Liu, PT
;
Sze, SM
;
Yang, YL
The new solutions, hydroxylamine sulfate [(NH2OH)(2)H2SO4] combined with CuSO4, for cleaning Al via were investigated. Tt is found that the cleaning capability of hydroxylamine sulfate combined with CuSO4 is better than that of hydroxylamine sulfate. Low via resistance of electrical test structure is obtained if the via is cleaned by this new cleaning solution. The hydroxylamine sulfate can efficiently remove Al3O2 and leave the clean Al on the surface of via. Then, the Cu ion in this new solution will immediately react with clean Al and form a copper passivating layer on the surface of via. The copper is more stable than aluminum in the environment and hard to be oxidized. Therefore, hydroxylamine sulfate combined with CuSO4 can provide excellent cleaning capability for aluminum via holes. Also, the clean surface on the bottom of via is helpful for tungsten nucleation in via during CVD-W deposition. Therefore, a low via resistance and good selectivity of tungsten plug are obtained when the Al via is precleaned with this new solution. (C) 1999 Elsevier Science S.A. All rights reserved.
Electrical properties of the Si implantation in Mg doped p-GaN
(1999-11-01)
Lai, WC
;
Yokoyama, M
;
Tsai, CC
;
Chang, CS
;
Guo, JD
This work performs Si ion implantation to activate and convert the electrical conduction of p-GaN films from p-type to n-type. Multiple implantation method is used to form a uniform Si implanted region in the p-type GaN epitaxial layer. Implantation energies for the multiple implantation are 10, 100, and 200 keV. The implantation dose is 5 x 10(15) cm(2) for each implantation energy. After implantation, the samples were annealed in an N-2 ambient for different annealing temperatures and annealing times. The activation efficiency reaches as high as 20% when annealing the sample at 1000 degrees C,. The carrier activation energy is about 720 meV. The low activation energy indicates that the hopping process mechanism is the dominant mechanism for the activation of the Si implant in p-GaN. In addition, the rectifying I-V characteristic of the p-n GaN diode is also examined.
"Laboratory exercises help me memorize the scientific truths": A study of eighth graders' scientific epistemological views and learning in laboratory activities
(1999-11-01)
Tsai, CC
;
師資培育中心
;
Center of Teacher Education
Upon analysis of 25 Taiwanese eighth graders' questionnaire responses, actual laboratory observation recording, and interview details, the present study was conducted to explore the interplay between students' scientific epistemological views (SEVs) and their learning in school laboratory activities. It was revealed that, although higher achievers tended to have a greater frequency of verbal negotiations directly related to laboratory details, students' SEVs were also related to their laboratory verbal interactions. It was found that students having SEVs more oriented to constructivist views of science, called constructivist students, tended to focus more on negotiating the meanings of experiments with their peers than did students having SEVs more in line with empiricist views of science, called empiricist students (p < 0.05). Constructivist students perceived actual laboratory learning environments as less open-ended and less integrated (p < 0.05) and they tended to prefer a more student-supported and open-ended approach to experimentation (p < 0.05). Interview details showed that constructivist learners tended to explore deeply the involved concepts of laboratory activities, resulting in a richer understanding. On the other hand, empiricist learners placed greater emphasis on "doing" laboratory work, following the codified procedures of science textbooks, and they believed that laboratory exercises made scientific concepts more impressive, acting as memory aids. This study concludes that an appropriate understanding of the constructivist epistemology of science should be an essential prerequisite for implementing so-called "constructivist science teaching." (C) 1999 John Wiley & Sons, Inc.
Reliable determination of object pose from line features by hypothesis testing
(1999-11-01)
Chang, CC
;
Tsai, WH
;
資訊工程學系
;
Department of Computer Science
To develop a reliable computer vision system, the employed algorithm must guarantee good output quality. In this study, to ensure the quality of the pose estimated from line features, two simple test functions based on statistical hypothesis testing are defined. First, an error function based on the relation between the line features and some quality thresholds is defined. By using the first test function defined by a lower bound of the error function, poor input can be detected before estimating the pose. After pose estimation, the second test function can be used to decide if the estimated result is sufficiently accurate. Experimental results show that the first test function can detect input with low qualities or erroneous line correspondences and that the overall proposed method yields reliable estimated results.
Effectively blocking copper diffusion at low-k hydrogen silsesquioxane/copper interface
(1999-11-01)
Liu, PT
;
Chang, TC
;
Yang, YL
;
Cheng, YF
;
Shih, FY
The interaction between copper and low-k hydrogen silsesquioxane (HSQ) film was investigated using a Cu/HSQ/Si metal insulation semiconductor capacitor and hydrogen plasma posttreatment. Owing to serious diffusion of copper atoms in HSQ film, degradation of the dielectric properties are significant with the increase of thermal stress. By applying hydrogen plasma treatment to the HSQ film, however, the phenomena of serious Cu penetration were not observed by electrical characteristic measurements and secondary ion mass spectroscopy (SIMS) analysis even in the absence of diffusion barrier layers. Therefore, hydrogen plasma treatment can effectively block the diffusion of copper in low-k HSQ film.
Reducing memory traffic and accelerating prolog execution in a superscalar prolog system
(1999-11-01)
Ma, RL
;
Chung, CP
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
Memory access operations constitute about 32.7% of all the operations executed in a typical Prolog program. Among these memory accesses, 75% are to the program control structures (environments and choice points). These memory accesses plus possible data cache misses greatly impair system performance, and the problem is even more severe in a VLIW, superscalar, or superpipelined Prolog system. This paper describes an innovative windowed register file management technique called SORWT (splittable overlapping register window technique). With SORWT, environments, choice points, and arguments can be stored in a windowed register file. SORWT reduces the number of memory accesses to only 25% of the number made when a conventional stack scheme is used. This paper describes in detail how Warren and PLM instructions can be implemented using SORWT and it presents a register file overflow/underflow handling mechanism called the memory window matrix (MWM) and a mapping function for use between register windows and the MWM. Thirty benchmark programs are used to study performance issues, the overhead of SORWT, optimal register file and window sizes, and the argument overflow rate.
An efficient multipath routing for distributed computing systems with data replication
(1999-11-01)
Chen, DJ
;
Chang, PY
;
資訊工程學系
;
Department of Computer Science
In distributed computing environments, executing a program often requires the access of remote data files. An efficient data routing scheme is thus important for time-critical applications. To ensure a prior desired communication quality, we present a connection-oriented routing scheme, the multipath routing, which allows multiple routes to be established between the source and the destination. Based on the multipath routing scheme, the problem of finding a collection of routing paths for an application to minimize its data transmission time is addressed. Such a problem becomes a complex combinatorial one when the application accesses multiple replicated data sources. Since finding an optimal solution is computationally infeasible in practice, we thus propose a heuristic method to get a sub-optimal solution. (C) 1999 Elsevier Science Inc. All rights reserved.