Browsing by Issue Date, starting with "2000-03-01"

Now showing 1 - 20 of 78541

Forest leaves and four-cycles
(2000-03-01)
Fu, HL
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Rodger, CA
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應用數學系
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Department of Applied Mathematics
In this article, we find necessary and sufficient conditions for the existence of a 4-cycle system of K-n - E(F) for any forest F of K-n. (C) 2000 John Wiley & Sons, Inc.
Enhancing science instruction: the use of 'conflict maps'
(2000-03-01)
Tsai, CC
;
師資培育中心
;
Center of Teacher Education
This paper proposes the use of 'conflict maps' as a way of enhancing science teaching and learning. The conflict map emphasizes not only the use of discrepant events, but also the resolution of the conflict between students' alternative conceptions and the scientific conception, using critical events or explanations and relevant perceptions and conceptions that explicate the scientific conception. The use of conflict maps is consistent with a conceptual change model suggested by science educators; hence, it is expected that the conflict map could help students overcome alternative conceptions and thus promote conceptual change. The conflict map, which clearly displays students' alternative conceptions and scientific conceptions, could be used as an instructional aid, helping science teachers construct or implement lesson plans, or as a metacognitive tool, helping learners monitor their ideas and the processes of conceptual change.
Fault-tolerant gamma interconnection networks by chaining
(2000-03-01)
Chen, CW
;
Lu, NP
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Chen, TF
;
Chung, CP
;
資訊工程學系
The authors propose two single-fault-tolerant gamma interconnection networks. The first is a partially chained gamma interconnection network (PCGIN) with two disjoint paths between any source-destination pair. A PCGIN has the characteristics of one fault tolerance and destination tag routing, but backtracking may be necessary when a fault occurs. To eliminate the backtracking penalties of a PCGIN, a fully chained gamma interconnection network (FCGIN); that can at least tolerate one link or switch fault at each stage without backtracking, is also proposed FCGIN has the advantages of destination tag routing, lower hardware costs than a PCGIN, low fault penalty, and strong reroutability.
Theoretical analysis of extrusion of rectangular, hexagonal and octagonal composite clad rods
(2000-03-01)
Wu, CW
;
Hsu, RQ
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機械工程學系
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Department of Mechanical Engineering
Composite clad rods with non-axisymmetric cross-sectional areas are commercially important owing to their extensive industrial applications such as in electrodes, conductors and chemical devices. For instance, in the processing of superconductor wire, increasing the packing density involves closely packing superconductor rods which have a hexagonal cross-section next to each other inside the high purity copper tube. During extrusion process, non-uniform deformation tends to occur because the core and sleeve of a composite clad rod is usually composed of materials with different mechanical properties. The first recognized paper on round-to-square drawing/extrusion with variable corner radius was presented by Beer et al. in 1979. In this study, we present a model based on upper-bound theorem to analyze the extrusion of composite clad rods with non-axisymmetric cross-section. Velocity fields for both core and sleeve are generated with the assistance of a product's cross-sectional profile functions. Products with rectangular, hexagonal and octagonal sections are chosen as the study objects. Also discussed herein are numerical results for various process variables such as semi-die angle, reduction of area, frictional condition of die, and product shape complexity. According to these results, the extrusion pressure and product dimensional change are closely related to the process variables. (C) 1999 Elsevier Science Ltd. All rights reserved.
Integral sliding control for disturbance matched to part of the inputs
(2000-03-01)
Chen, YP
;
Chang, JL
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電控工程研究所
;
Institute of Electrical and Control Engineering
This paper presents a theoretical research on the integral sliding control technology for linear time-invariant systems encountering disturbance matched to part of the control inputs. Only part of the control inputs is designed by the sliding-mode theory to eliminate the disturbance. Besides, based on the pole-assignment method the design of integral sliding vector becomes simple and straightforward. A numeric example is finally used to demonstrate the success of the developed controller.
Adaptive-level memory caches on World Wide Web servers
(2000-03-01)
Chang, DW
;
Ke, HR
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Chang, RC
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交大名義發表
;
資訊工程學系
Owing to the fast growth of World Wide Web (WWW), web traffic has become a major component of Internet traffics. Consequently, the reduction of document retrieval latency on WWW becomes more and more important. The latency can be reduced in two ways: reduction of network delay and improvement of web servers' throughput. Our research aims at improving a web server's throughput by keeping a memory cache in a web server's address space. In this paper, we focus on the design and implementation of a memory cache scheme. We propose a novel web cache management policy named the adaptive-level policy that either caches the whole file content or only a portion of it, according to the file size. The experimental results show three things. First, our memory cache is beneficial since, under our experimental workloads, the throughput improvement can achieve 32.7%. Second, our cache management policy is suitable for current web traffic. Third, with the increasing popularity of multimedia files, our policy will outperform others currently used in WWW. (C) 2000 Elsevier Science B.V. All rights reserved.
Admission control for variable spreading gain CDMA wireless packet networks
(2000-03-01)
Lee, TH
;
Wang, JT
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電信工程研究所
;
Institute of Communications Engineering
A technique for variable spreading gain code-division multiple access (VSG-CDMA) with transmit power control has recently been proposed [4], [5] to provide integrated services in a wireless packet network. System capacities of VSG-CDMA networks with and without considering user activity factors were derived. The analysis gives a lower bound of system capacity because a user's transmitted power is considered part of the interference to its own signal. In this paper, we present an optimistic upper bound assuming that there is no multipath fading or the energy of a signal in all multipath components can be fully resolved. An optimum power vector assignment and a simple criterion for all users to simultaneously achieve their quality of service (QoS) requirements tin terms of bit energy-to-interference density ratios) are derived. We found from numerical examples that, compared with the lower bound given in [4] and [5], significant improvement can be obtained if multipath fading can be satisfactorily handled. Several access control schemes are also studied to guarantee delay bound requirements. Simulation results reveal that more connections can be further accommodated with access control.
Voltage and frequency dependence of differential capacitance in relaxed In0.2Ga0.8As/GaAs Schottky diodes
(2000-03-01)
Chen, JF
;
Chen, NC
;
Wang, JS
;
Wang, PY
;
電子物理學系
Capacitance dispersion over frequency is investigated for relaxed In0.2Ga0.8As/GaAs Schottky diodes. While the high-frequency capacitance is voltage-independent, the low-frequency capacitance is seen to decrease with reverse voltage. Based on a Schottky barrier combined with a high-resistance layer containing traps, a simplified equation for the differential capacitance is derived to explain the capacitance-voltage-frequency relation. It is found that the high-frequency capacitance corresponds to the total thickness of the Schottky depletion and the high-resistance layer, while the low-frequency capacitance at a small reverse voltage is the Schottky depletion capacitance and at a large reverse voltage is the high-frequency capacitance.
Satellite sensor image classification using cascaded architecture of neural fuzzy network
(2000-03-01)
Lin, CT
;
Lee, YC
;
Pu, HC
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電控工程研究所
;
Institute of Electrical and Control Engineering
Satellite sensor images usually contain many complex factors and mixed pixels, so a high classification accuracy is not easy to attain. Especially, for a nonhomogeneous region, gray values of satellite sensor images vary greatly and thus, direct statistic gray values fail to do the categorization task correctly. The goal of this paper is to develop a cascaded architecture of neural fuzzy networks with feature mapping (CNFM) to help the clustering of satellite sensor images, In the CNFM, a Kohonen's self-organizing feature map (SOFM) is used as a preprocessing layer for the reduction of feature domain, which combines original multi-spectral gray values, structural measurements from co-occurrence matrices, and spectrum features from wavelet decomposition. In addition to the benefit of dimensional reduction of feature space, Kohonen's SOFM can remove some noisy areas and prevent the following training process from being overoriented to the training patterns, The condensed measurements are then forwarded into a neural fuzzy network, which performs supervised learning for pattern classification. The proposed cascaded approach is an appropriate technique for handling the classification problem in areas that exhibit large spatial variation and interclass heterogeneity (e.g., urban-rural infringing areas). The CNFM is a general and useful structure that can give us favorable results in terms of classification accuracy and learning speed, Experimental results indicate that our structure can retain high accuracy of classification (90% in average), while the training time is substantially reduced if our system is compared to the commonly used backpropagation network. The CNFM appears to be more reasonable and practical than the conventional implementation.
Applying fuzzy logic in the modified single-layer perceptron image segmentation network
(2000-03-01)
Chang, JY
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Chen, JL
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電控工程研究所
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Institute of Electrical and Control Engineering
In this paper, we propose a fuzzy-logic-based modified single layer perceptron (MSLP) image segmentation network for object extraction. We select a sigmoid gray level transfer function with the aid of the input image histogram and map the input gray levels into the interval [0,1]. Then we adopt the linear index of fuzziness of the output nodes as the error function of the image segmentation system to incorporate the learning capability of a neural network. Our scheme can successfully extract objects from the background. To further enhance the capability of the segmentation system, the proposed network is incorporated with fuzzy if-then rules to adaptively adjust the threshold of the activation function of the MSLP output neuron for best matching the local characteristics of the image. Fuzzy if-then rules involving the edge intensities and vertical positions of pixels are reasoned to determine the threshold adaptively. From the results of segmenting forward looking infrared (FLIR) images, better segmentation images have been obtained by incorporating fuzzy if-then rules with the MSLP segmentation technique. As demonstrated by this study, it is promising and worthy of study that incorporating human knowledge in terms of Fuzzy rules into a designed numerical algorithm can further improve performance, not only in the segmentation problem we present.
Active, programmable, and mobile code networking
(2000-03-01)
Morreale, P
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Sohraby, K
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Li, B
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Lin, YB
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資訊工程學系
Decoding of CISC instructions in superscalar processors with high issue rate
(2000-03-01)
Shiu, RM
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Chiu, JC
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Cheng, SK
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Shann, JJJ
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資訊工程學系
The paper examines the design issues of decoders, including the primitive operation (POP) translation strategies and the decoding rules, for CISC superscalar processors to exploit a higher degree of parallel execution. Attention is focused on the x 86 instruction set because of its popularity. There are two different approaches regarding POP translation strategies: one is to merge the address generation into load/store operations, and the other is to translate the isolated address generation operations. Simulation results show that, in high issue-rate decoders, the latter strategy improves the performance by 20 to 25 %. Furthermore, considering the tradeoffs between the hardware cost and performance, a cost-effective decoding rule suitable for current commercial programs is recommended.
Cascoded LVTSCR with tunable holding voltage for ESD protection in bulk CMOS technology without latchup danger
(2000-03-01)
Ker, MD
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Chang, HH
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
The lateral SCR devices used in CMOS on-chip ESD protection circuits are reviewed. Such SCR devices had been found to be accidentally triggered by noise pulses when the ICs are operated in the application systems. A cascoded design is therefore proposed to safely apply the LVTSCR devices for whole-chip ESD protection in CMOS ICs without causing unexpected operation errors or latchup danger. The temperature dependence on the holding voltage of the cascoded LVTSCRs has been investigated in detail. From the experimental verification, the cascoded LVTSCRs can be fully turned on within a time below 20 ns. The ESD robustness per layout area of the three-cascoded LVTSCRs can be 0.83 V/mu m(2) in a 0.35-mu m silicide CMOS process without using the extra silicide-blocking and ESD-implant masks, whereas the ESD robustness of the gate-grounded NMOS is only 0.25 V/mu m(2). Such cascoded LVTSCRs with a tunable holding voltage greater than VDD can provide CMOS ICs with effective component-level ESD protection but without causing catchup danger if it is accidentally triggered by the system-level overshooting or undershooting noise pulses. (C) 2000 Elsevier Science Ltd. All rights reserved.
A repetitive learning method based on sliding mode for robot control
(2000-03-01)
Liu, TS
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Lee, WS
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機械工程學系
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Department of Mechanical Engineering
In order to make a robot precisely track desired periodic trajectories, this work proposes a sliding mode based repetitive learning control method, which incorporates characteristics of sliding mode control into repetitive learning control. The learning algorithm not only utilizes shape functions to approximate influence functions in integral transforms, but also estimates inverse dynamics functions based on integral transforms. It learns at each sampling instant the desired input joint torques without prior knowledge of the robot dynamics. To carry out sliding mode control, a reaching law method is employed, which is robust against model uncertainties and external disturbances. Experiments are performed to validate the proposed method.
Search of optimum bias voltage for oxide patterning on Si using scanning tunneling microscopy in air
(2000-03-01)
Tseng, KS
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Hsieh, TE
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Lo, SC
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Lin, HF
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材料科學與工程學系
Nanometer-scale oxide patterns were fabricated on H-passivated Si using a scanning tunneling microscopy (STM) in air. We found that the optimum bias voltage to generate clean and uniform oxide patterns depends on the composition of the tip material rather than on the tip head sharpness. For tungsten tips, oxide patterns with the desired geometrical features can be obtained at bias voltages ranging from -0.8 to -1.2 V, while for platinum-iridium tips, the bias voltages lie between -1.5 and -2.5 V at a fixed tunneling current of 2.0 nA. These biases correspond to the working voltage generating the oxide pattern with the lowest apparent depth. Beyond these voltage ranges, tip scratching on the sample surface or field-induced mass transfer from the tip might occur, as evidenced by tip wearing and the contamination of debris of tip material in the vicinity of the patterns. On the other hand, the tip head sharpness affects the width and the height of line patterns. When extremely fine oxide lines were desired, a sharp tip has to be used for STM patterning. (C) 2000 American Vacuum Society. [S0734-211X(00)08202-0].
Model selection and semiparametric inference for bivariate failure-time data
(2000-03-01)
Wang, WJ
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Wells, MT
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統計學研究所
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Institute of Statistics
We propose model selection procedures for bivariate survival models for censored data generated by the Archimedean copula Family. In route to constructing the selection methodology, we develop estimates of some time-dependent association measures, including estimates of the local and global Kendall's tau, local odds ratio, and other measures defined throughout the literature. We propose a goodness-of-fit-base model selection methodology as well as a graphical approach. We show that the proposed methods have desirable asymptotic properties and perform well in finite samples.
Process program change control in a process environment
(2000-03-01)
Chou, SC
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Chen, JYJ
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資訊工程學系
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Department of Computer Science
Process programs may change during enactment. The change of an enacting process program should be controlled. This paper describes process program change control in the CSPL (Concurrent Software Process Language) environment, which consists of techniques to (1) define change plans, (2) analyze and handle change impacts, and (3) resume process programs, Moreover, we provide an editor to guide process program change, with which the consistency between a change plan and the actual change can be enforced. We have used the environment in an experimental setting, and that experience shows that change control provided by the environment depends significantly upon process programs. If the dependencies among process components are well-specified in a process program, the change control mechanism will detect all the affected components when the process program is changed. Copyright (C) 2000 John Wiley & Sons, Ltd.
Incrementally extensible folded hypercube graphs
(2000-03-01)
Chang, HY
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Chen, RJ
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資訊工程學系
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Department of Computer Science
In this paper, we propose the incrementally extensible folded hypercube (IEFH) graph as a new class of interconnection networks for an arbitrary number of nodes. We show that this system is optimal fault tolerant and almost regular (i.e., the difference between the maximum and the minimum degree of nodes is at most one). The diameter of this topology is half of that of the incomplete hypercube (IH), the supercube, or the IEH graph. We also devise a simple routing algorithm for the IEFH graph. Finally, we embed cycles and complete binary trees into this graph optimally.
Path-based protocol verification approach
(2000-03-01)
Liu, WC
;
Chung, CG
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資訊工程學系
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Department of Computer Science
Protocol verification is one of the most challenging tasks in the design of protocols. Among the various proposed approaches, the one based on reachability analysis (or known as state enumeration approach) is of the most: simple, automatic and effective. However, the state explosion problem is a principle obstacle toward successful and complete verifications of complex protocols. To overcome this problem, we proposed a new approach, the "path-based approach." The idea is to divide a protocol into a collection of individual execution record, denoted as: concurrent paths, a partial order representation recording the execution paths of individual entities. Then, the verification of the protocol is, thus, replaced by that of individual concurrent paths. Since concurrent paths can be automatically generated through Cartesian product:of the execution paths of all modules, and verified independently, the memory requirement is limited to the complexity of individual concurrent path rather than the whole protocol. Thus, the state explosion problem is alleviated from such "divide and conquer" approach. Furthermore, we propose an algorithm, making the trade-off on memory requirement to generate the concurrent paths more efficiently; and utilize the technique of symmetric verification, parallel computing to improve the efficiency of verification. Eventually, our experience of verifying real protocols shows that our approach uses much less memory:and time than reachability analysis. (C) 2000 Elsevier Science B.V. All rights reserved.
Design of multicode CDMA systems for 3-D stereoscopic video over wireless ATM networks
(2000-03-01)
Chang, PR
;
Lin, CF
;
Wu, MJ
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電信工程研究所
;
Institute of Communications Engineering
This paper investigates the application of multicode spread-spectrum code-division multiple-access (SS-CDMA) techniques to three-dimensional (3-D) stereoscopic video transmission over wireless asynchronous transfer mode (ATM) networks. Three-dimensional visual communications, made through the use of stereoscopic images, are able to achieve total display realism. Such services allow users to share the virtual reality (VR) world without any geographical restrictions. In order to create a 3-D system with two images (left and right) that should be transmitted over a bandlimited mobile channel simultaneously, a cost-effective Motion Picture Experts Group (MPEG)-based wavelet multiresolution coding with a joint motion and disparity compensation is developed to reduce a large amount of information contained in the images to meet the low-transmission rate limitation of mobile channels. However, the rapidly variable bit rate (VBR) characteristics of the MPEG-based 3-D videos seems a weakness to the transmission of such videos via a constant bit-rate (CBR) mobile channel. The ATM technique is especially well suited for VER MPEG-based 3-D video because of its ability to allocate bandwidth on demand to these services. However, since the mobile radio has a Limited channel capacity, the overall capacity of the traditional ATM-based SS-CDMA system may not be sufficient to accommodate the MPEG-based 3-D video services requested by the multiple mobile users simultaneously. To tackle this difficulty, a multicode CDMA technique is proposed to provide VER MPEG-based 3-D video services by varying the number of spreading codes assigned to the 3-D video to meet its dynamic throughput requirement. Powerful forward error correction (FEC) codes are necessary to protect the video data so that it can be successfully transmitted at an acceptable signal power level. Two separate FEC code schemes are applied to the header and payload of an ATM cell containing 3-D video data, respectively. The ATM cell header is protected by a relatively powerful FEC code to ensure correct delivery and low cell loss rate (CLR). On the other hand, the ATM cell payload is encoded for varying degrees of error protection according to the priority of the payload data in 3-D videos. An adaptive FEC code combining scheme is proposed to provide the good protection for payload data with the maximization of its code rate to minimize the extra bandwidth for FEC overhead.