Browsing by Author "Liu, JS"

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A geometry-based error estimation for cross-ratios
(2002-01-01)
Liu, JS
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Chuang, JH
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資訊工程學系
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Department of Computer Science
For choosing specific cross-ratios as 2D projective coordinates in various computer vision applications, a reasonable error analysis model is usually required. This investigation adopts the assumption of normal distribution for positioning errors of point features in an image to formulate the error variances of cross-ratios. Based on a geometry-based error analysis, a straightforward way of identifying the cross-ratios with minimum error variances is proposed. Simulation results show that the proposed approach. as well as a further simplified alternative, yield much better estimations of minimum error variances in terms of accuracy, cost, and stability compared with some other methods, e.g., the one based on the rule given by Georis et al. (IEEE Trans. Pattern Anal. Mach. Intell. 20 (4) (1998) 366). Some causes of the performance differences in the estimations are explained using a special configuration of point features. (C) 2001 Pattern Recognition Society. Published by Elsevier Science Ltd. All rights reserved.
A novel dual focus objective lens for DVD/CD pick-up head
(1998-03-01)
Liu, PY
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Shieh, HPD
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Ju, JJ
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Tsai, ST
;
Yang, TM
A new dual focus objective lens of combinig aspherical surfaces of DVD and CD for DVD/CD pick-up head was designed. Numerical analysis based on the diffraction model were studied to trade off the spot size, side lobe, and energy ratio of DVD and CD, The hybrid aspherical surfaces of DVD and CD are optimized for low aberration. The spot size of full wave half maximum (FWHM) are 0.553 and 0.88 mu m for DVD and CD, respectively, measured from thus constructed double rings lens.
Characteristics of novel polysilicon oxide by anodic oxidation
(1999-09-01)
Yeh, CF
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Liu, JS
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Chiang, MC
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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
For nonvolatile memory applications, a novel oxide grown on polysilicon by anodic oxidation (anodic polyoxide) is first investigated. In this work, the electrical characteristics of anodic polyoxide is discussed and compared with the conventional thermal polyoxide. The results show that the anodic polyoxide exhibits considerably excellent characteristics, i.e., low leakage current, high breakdown electric field, and high reliabilities.
Investigation of high-power device and process for field emission display
(1996)
Yeh, CF
;
Liu, JS
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Huang, CM
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交大名義發表
;
電子工程學系及電子研究所
A method of fabricating a semiconductor device including a high withstanding voltage lateral CMOS and a standard logic CMOS is developed for field emission display. Structure, process and simulation by TSUPREM and MEDICI will be discussed in this paper.
QoS routing in ad hoc wireless networks
(1999-08-01)
Lin, CHR
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Liu, JS
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資訊工程學系
;
Department of Computer Science
The emergence of nomadic applications have recently generated much interest in wireless network infrastructures that support real-time communications. In this paper, we propose a bandwidth routing protocol for quality-of-ser,ice (QoS) support in a multihop mobile network. The QoS routing feature is important for a mobile network to interconnect wired networks with QoS support (e.g., ATM, Internet, etc.). The QoS routing protocol can also work in a stand-alone multihop mobile network for real-time applications. Our QoS routing protocol contains end-to-end bandwidth calculation and bandwidth allocation. Under such a routing protocol, the source (or the ATM gateway) is informed of the bandwidth and QoS available to any destination in the mobile network. This knowledge enables the establishment of QoS connections within the mobile network and the efficient support of real-time applications. In addition, it enables more efficient call admission control. In the case of ATM interconnection, the bandwidth information can be used to carry out intelligent handoff between ATM gateways and/or to extend the ATM virtual circuit (VC) service to the mobile network with possible renegotiation of QoS parameters at the gateway. We examine the system performance in various QoS traffic hows and mobility environments via simulation. Simulation results suggest distinct performance advantages of our protocol that calculates the bandwidth information, It is particularly useful in call admission control, Furthermore, "standby" routing enhances the performance in the mobile environment. Simulation experiments show this improvement.
R&D in China: an empirical study of Taiwanese IT companies
(2004-09-01)
Lu, LYY
;
Liu, JS
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經營管理研究所
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Institute of Business and Management
This study extends the research on R&D (research and development) internationalization to a new environmental context (two Asian newly-industrialized economies, mainland China and Taiwan). Based on a survey of 56 major Taiwanese information technology (IT) companies, the status of R&D internationalization with Taiwan as the home and mainland China as the host is investigated. Human-capital-augmentation is found to be the key motive for Taiwanese IT companies to extend R&D activities to the mainland. Accessing capable yet cost effective local engineers with an additional benefit of geographical and linguistic proximity is the major context of this motive. The location decision is based on three considerations - access to engineers, proximity to manufacturing site, and competition avoidance. Finally, three operational patterns of conducting the international design and development (D&D) activities are categorized, which are 'home-base-integration', 'host-base-integration', and 'product life cycle'.
Risk factors for fatal candidemia caused by Candida albicans and non-albicans Candida species
(2005-04-07)
Cheng, MF
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Yang, YL
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Yao, TJ
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Lin, CY
;
Liu, JS
Background: Invasive fungal infections, such as candidemia, caused by Candida species have been increasing. Candidemia is not only associated with a high mortality (30% to 40%) but also extends the length of hospital stay and increases the costs of medical care. Sepsis caused by Candida species is clinically indistinguishable from bacterial infections. Although, the clinical presentations of the patients with candidemia caused by Candida albicans and non-albicans Candida species (NAC) are indistinguishable, the susceptibilities to antifungal agents of these species are different. In this study, we attempted to identify the risk factors for candidemia caused by C. albicans and NAC in the hope that this may guide initial empiric therapy. Methods: A retrospective chart review was conducted during 1996 to 1999 at the Veterans General Hospital-Taipei. Results: There were 130 fatal cases of candidemia, including 68 patients with C. albicans and 62 with NAC. Candidemia was the most likely cause of death in 55 of the 130 patients (42.3%). There was no significant difference in the distribution of Candida species between those died of candidemia and those died of underlying conditions. Patients who had one of the following conditions were more likely to have C. albicans, age >= 65 years, immunosuppression accounted to prior use of steroids, leukocytosis, in the intensive care unit (ICU), and intravascular and urinary catheters. Patients who had undergone cancer chemotherapy often appeared less critically ill and were more likely to have NAC. Conclusion: Clinical and epidemiological differences in the risk factors between candidemia caused by C. albicans and NAC may provide helpful clues to initiate empiric therapy for patients infected with C. albicans versus NAC.
Self-calibration with varying focal length from two images obtained by a camera with small rotation and general translation
(2001-11-01)
Liu, JS
;
Chuang, JH
;
資訊工程學系
;
Department of Computer Science
The stratified self-calibration approach based on the absolute conic or its dual, the absolute dual quadric, has the merit of allowing the intrinsic camera parameters to vary while being retrieved from an image sequence. In this paper, we show that for a camera with small rotation and general translation, a new linear equation resulted from the infinity homography can be added to a system of linear equations to compute the absolute dual quadric. Experiments with both synthetic and real images show that satisfactory results can be obtained with the proposed linear approach. It is possible to further improve the calibration result by adopting some nonlinear optimization schemes, e.g., a suitable LM-like algorithm, to enforce the absolute dual quadric constraints using the linear solutions as an initial guess. (C) 2001 Elsevier Science B.V. All rights reserved.
Self-calibration with varying focal length from two images obtained by a stereo head
(2002-12-01)
Liu, JS
;
Chuang, JH
;
資訊工程學系
;
Department of Computer Science
The self-calibration approach based on the absolute conic or its dual) the absolute dual quadric, has the merit of allowing the intrinsic camera parameters to vary in image sequence. In this paper; we show that certain linear equations resulting from the infinity homography can be added to a system of originally undetermined linear equations to find the absolute dual quadric for a stereo head. The special stereo configurations considered here allow one camera to rotate around either one or two of the coordinate axes defined by another camera. Experiments with synthetic images show that satisfactory results can be obtained with only the proposed linear methods. For real images obtained with non-ideal stereo configurations, and possibly with measurement noises, results obtained from the proposed linear methods may serve as reasonable initial guesses for some non-linear optimization procedure. (C) 2002 Pattern Recognition Society. Published by Elsevier Science Ltd. All rights reserved.
Shadow generation from stereo images
(2000-04-13)
Chuang, JH
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Kuo, LW
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Kuo, HJ
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Liu, JS
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資訊工程學系
A novel approach to generating object shadows using two dimensional (2D) information is presented. Existing approaches to shadow generation are generally based on 3D geometry. The proposed method is based on deriving accurate shadows of a 3D object using only stereo images of the object taken from two different viewpoints. The approach can be extended easily to solve more general problems which involve multiple objects as well as multiple planar surfaces on which object shadows are to be cast.
Structure-stability-activity relationship in covalently cross-linked N-carbamoyl D-amino acid amidohydrolase and N-acylamino acid racemase
(2006-06-09)
Chiu, WC
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You, JY
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Liu, JS
;
Hsu, SK
;
Hsu, WH
N-Acylamino acid racemase (NAAAR) and N-carbamoyl-D-amino-acid amidohydrolase (D-NCAase) are important biocatalysts for producing enantiopure a-amino acids. NAAAR forms an octameric assembly and displays induced fit movements upon substrate binding, while D-NCAase is a tetramer that does not change conformation in the presence of a ligand. To investigate the effects of introducing potentially stabilizing S-S bridges in these different multimeric enzymes, cysteine residues predicted to form inter or intra-subunit disulfide bonds were introduced by site-directed mutagenesis. Inter-subunit S-S bonds were formed in two NAAAR variants (A68C-D72C and P60C-Y100C) and two D-NCAase variants (A302C and P295C-F304C). Intra-subunit S-S bonds were formed in two additional NAAAR variants (E149C-A182C and V265C). Crystal structures of NAAARs variants show limited deviations from the wild-type overall tertiary structure. An apo A68C-D72C subunit differs from the wild-type enzyme, in which it has an ordered lid loop, resembling ligand-bound NAAAR. The structures of A222C and A302C D-NCAases are nearly identical to the wild-type enzyme. All mutants with inter-subunit bridges had increases in thermostability. Compared with the wild-type enzyme, A68C-D72C NAAAR showed similar k(cat)/K-m ratios, whereas mutant D-NCAases demonstrated increased k(cat)/K-m ratios at high temperatures (A302C: 4.2-fold at 65 degrees C). Furthermore, molecular dynamic simulations reveal that A302C substantially sustains the fine-tuned catalytic site as temperature increases, achieving enhanced activity. (c) 2006 Elsevier Ltd. All rights reserved.