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740-km transmission of 78-channel 64-QAM signals (2.34 Gb/s) without dispersion compensation using a recirculating loop
(2000-09-01)
Wu, MC
;
Wong, JK
;
Tsai, KT
;
Chen, YL
;
Way, WI
A long-distance 1550-nm subcarrier multiplexed lightwave trunk system that transported 78 channels of 64-QAM signals was demonstrated in a recirculating loop experiment. Each channel can achieve a carrier-to-(noise + nonlinear distortion) ratio of 30 dB after 740-km transmission through conventional single-mode fiber without dispersion compensation.
Multilevel recording in erasable phase-change media by light intensity modulation
(2001-03-01)
Shieh, HPD
;
Chen, YL
;
Wu, CH
;
光電工程學系
;
Department of Photonics
Multilevel recording has an advantage of increasing the recording density without extensively altering the current optical configuration. Four-level recording schemes in phase-change disks using either two or three recording layers were demonstrated. By modulating the intensity of the laser pulse, marks were recorded in any of the recording layers, forming four recording regions. Utilizing the large difference in refractive indices between the amorphous and crystalline states, each recording region corresponds to a different reflectance. For the four-level recording disk, if each recording region represents two-bit data, then the recording density of the four-level disk can be higher by a factor of two than that of a conventional disk recorded by pulse position modulation (PPM).
A discrete region competition approach incorporating weak edge enhancement for ultrasound image segmentation
(2003-02-01)
Chen, CM
;
Lu, HHS
;
Chen, YL
;
統計學研究所
;
Institute of Statistics
Ultrasound images are inherently difficult to analyze due to their echo texture, speckle noise and weak edges. Taking into account these characteristics, we present a new region-based approach for ultrasound image segmentation. It is composed of two primary algorithms, discrete region competition and weak edge enhancement. The discrete region competition features four techniques, region competition, statistical modeling of speckle, early vision modeling, and discrete concepts. In addition, to prevent regions from leaking out of the desired area across weak edges, edges located on the slowly varying slope are enhanced according to their position on the slope and the length of the slope. This new approach has been implemented and verified on clinical ultrasound images. (C) 2002 Elsevier Science B.V. All rights reserved.
Electron field emission from fluorinated amorphous carbon nanoparticles on porous alumina
(2003-12-15)
Lai, SH
;
Huang, KP
;
Pan, YM
;
Chen, YL
;
Chan, LH
The fluorinated amorphous carbon nanoparticles (a-C:F NPs) films have been prepared on a porous alumina at a lower temperature of similar to100 degreesC by an ECR-CVD system with a mixture of CF4, C2H2 and Ar as precursors. The morphology of a-C:F NPs films was verified by FESEM. The microstructure and chemical bonding nature of the a-C:F NPs films were investigated by Raman spectroscopy and XPS, respectively. The fluorinated samples need a lower field (similar to2.25 V/mum for 10.6% F a-C:F NPs films) to emit the electron than unfluorinated ones. The excellent field-emission properties of a-C:F NPs films are due to the effect of the shape, fluorine doping and dangling bonds. (C) 2003 Elsevier B.V. All rights reserved.
Algorithms for compressing compound document images with large text/background overlap
(2004-12-01)
Wu, BF
;
Chiu, CC
;
Chen, YL
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Two algorithms are presented for compressing image documents, with a high compression ratio for both colour and monochromatic compound document images. The proposed algorithms apply a new method of segmentation to separate the text from the image in a compound document in which the text overlaps the background. The segmentation method classifies document images into three planes: the text plane, the background (non-text) plane and the text's colour plane, each of which are processed using different compression techniques. The text plane is compressed using the pattern matching technique, called JB2. Wavelet transform and zerotree coding are used to compress the background plane and the text's colour plane. Assigning bits for different planes yields high-quality compound document images with both a high compression ratio and well presented text. The proposed algorithms greatly outperform two well known image compression methods, JPEG and DjVu, and enable the effective extraction of the text from a complex background, achieving a high compression ratio for compound document images.
Slicing object-oriented programs
(1997)
Chen, JL
;
Wang, FJ
;
Chen, YL
;
資訊工程學系
;
Department of Computer Science
Program slicing has various applications in the fields of software engineering. The Object-Oriented (OO) paradigm introduces the features of abstraction, encapsulation, inheritance, and polymorphism to programs, but is not considered current program slicing techniques. In this paper, we define two types of program slices, state and behavior slices, by taking the dependencies of OO features into consideration. A state slice for an object is a set of messages and control statements that might affect the state of the object, while a behavior slice is a set of attributes and methods defined in related classes that might affect the behavior of the object. These slices may facilitate programmers to debug and understand OO software. The algorithms that developed based on an Object-oriented Dependency Graph to compute these slices can get more precise result by exploring the internal dependencies of complex objects.
Error control for H.263 video transmission over wireless channels
(1998)
Chen, YL
;
Lin, DW
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We consider ways to combat the error effects when transmitting H.263 video over a wireless channel. The error control measures consist of two "layers," namely, that of the coded bitstream and of the video information. At the bitstream layer, we employ error-resilient entropy coding (EREC), with pseudo-random block interleaving, to reduce the error propagation in decoding of variable-length codewords. At the information layer, we employ a DC recovery scheme to conceal the effects of corrupted DC coefficients. Corrupted motion vectors are detected and corrected using a motion-vector pairing technique in the encoder and a corresponding motion-vector checking and recovery algorithm in the decoder. By these methods, corrupted strips in the images caused by loss of synchronization are avoided. The annoying "green/pink block artifacts" caused by erroneous DC coefficients and the effects of incorrect motion compensation caused by corrupted motion vectors are also reduced.
An object-oriented dependency graph for program slicing
(1998)
Chen, JL
;
Wang, FJ
;
Chen, YL
;
資訊工程學系
;
Department of Computer Science
Program dependency graphs (PDG's) of a program facilitate program analysis and related applications such as program slicing, a method to identify the relevant entities of the program according to data and control dependencies. In the past, PDG's and program slicing were most developed for (conventional) imperative programs. Recently, the object-oriented (OO) paradigm gained momentum and popularity. The OO paradigm introduces the features of object abstraction, encapsulation, inheritance, and polymorphism to programs, but is not considered in PDG's and program slicing. In this paper, we present an Object-Oriented Dependency Graph (ODG) to represent the structure of OO programs. The ODG is defined based on a property multi-digraph that is extended from a directed graph by augmenting multiple edge types, vertex properties, and property relations. With the extension, the ODG cart avoid the specious dependencies due to object encapsulation. Based on the ODC, a program slicing method for OO software is developed. Besides data and control dependencies, dependencies caused by OO features are taken into consideration in our slicing method. Through the ODG, the slicing method might be applied to facilitate understanding debugging, and maintaining OO software as well as traditional program slicing methods do.
Structured design of standard-compatible error-resilient video coding, with application to H.263
(2000)
Lin, DW
;
Chen, YL
;
Lee, CT
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Many methods for video transmission error control have been proposed recently, especially in relation to transmission over bursty-error channels. However, a thorough, structural taxonomical framework for analysis and design of such methods seems lacking. Such a framework helps clarity in thought and aids in inspiring new error control methods or combinations thereof. We present a framework for classification of the various transmission error control techniques. We then consider error control for H.263. Several techniques are presented from the viewpoint of the proposed analysis framework and they illustrate how different techniques can be integrated coherently to achieve enhanced error resilience in the overall system. In particular, we employ slotted multiplexing at the multiplex level to reduce synchronization errors in variable-length coded data and to randomize the locations of the remaining error-corrupted image areas. At the source level, we introduce two standard-compatible schemes, called length-based intra refresh and motion vector pairing, respectively, which further limit spatial-temporal error propagation.
Multi-level recording in erasable phase-change media by light intensity modulation
(2000)
Chen, YL
;
Shieh, HPD
;
光電工程學系
;
Department of Photonics
Multi-level recording has advantage of increasing the recording density without extensively altering the current optic configuration. In this paper, a new four-level recording phase-change disk using three-recording layers was demonstrated. By modulating the intensity of the laser pulse, marks were chosen to record in any of recording layers, to form four recording regions. Utilizing the property of the phase change media whose amorphous and crystalline states differ largely in refractive indices, each recording region corresponds to different reflectance. For the four-level recording disk, each recording region represents two-bit data, then the recording density of the four-level disk is a factor of two higher than that of a conventional disk recorded by adopting the pulse position modulation (PPM).

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