Browsing by Author "Wang, WJ"

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A novel LCD driver testing technique using logic test channels
(2003)
Su, CC
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Wang, WJ
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Wang, CH
;
Tseng, IS
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電控工程研究所
This paper proposes a novel voltage measurement technique for LCD driver testing by the use of logic test channel of an ATE. The method is able to achieve less than 1mV error with the presence of 32mV RMS noise.
Characterization and properties of new silicone-containing epoxy resin
(2000-07-01)
Wang, WJ
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Perng, LH
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Hsiue, GH
;
Chang, FC
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應用化學系
A new epoxy monorner, triglycidyloxy phenyl silane (TGPS) has been synthesized. By curing of TGPS, Epon 828 and DER 732, with 4,4-diaminodiphonyl methane (DDM), the curing rate and conversion efficiency of these epoxy resins are in the order of TGPS > Epon 828 > DER 732. In the mixed epoxy system of TGPS/Epon 828/DDM, homogenous products are obtained from all proportions. In addition, the glass transition temperature of the blend decreases with increasing amount of TGPS from 140 to 100 degrees C. By using TGA in a Nz environment, the onset decomposition temperature of silicone-containing epoxy resin system of TGPS is 80 degrees C lower than that of Epon 828, and the decomposition of TGPS is a two-stage process with maxima weight loss rates at 330 and 430 degrees C, respectively. The first stage involves the breaking of the silicons-containing group in TGPS and the second-stage is carbonization. In the second stage of carbonization, the temperature for maximum weight loss rate is 15 degrees C higher than that of the Epon 828 in the first stage. This result indicates that the silicone-containing group is in favor of the carbonization mechanism and the solid char yield at 800 degrees C for TGPS is 40 wt%. Based on EDX analysis on the surface elements, the presence of Si and C is indicative of the above observation. In addition, the result by using TGA in an air environment shows that the silicon-containing carbon residue is superior in preventing oxidative burning. The high limiting oxygen index (LOI) of TGPS at 35 is considered as an excellent flame retardant in the epoxy system. (C) 2000 Elsevier Science Ltd. All rights reserved.
Estimating the association parameter for copula models under dependent censoring
(2003)
Wang, WJ
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統計學研究所
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Institute of Statistics
Many biomedical studies involve the analysis of multiple events. The dependence between the times to these end points is often of scientific interest. We investigate a situation when one end point is subject to censoring by the other. The model assumptions of Day and co-workers and Fine and co-workers are extended to more general structures where the level of association may vary with time. Two types of estimating function are proposed. Asymptotic properties of the proposed estimators are derived. Their finite sample performance is studied via simulations. The inference procedures are applied to two real data sets for illustration.
Estimation of Kendall's tau under censoring
(2000-10-01)
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 study nonparametric estimation of Kendall's tau, tau, for bivariate censored data. Previous estimators of tau, proposed by Brown, Hollander and Korwar (1974), Weier and Basu (1980) and Oakes (1982), fail to be consistent when marginals are dependent. Here we express tau as an integral functional of the bivariate survival function and construct a natural estimator via the von Mises functional approach. This does not necessarily yield a consistent estimator since tail region information on the survival curve may not be identifiable due to right censoring. To assess the magnitude of the inconsistency we propose some estimable bounds on tau. It is shown that estimates of the bounds shrink to provide consistency if the largest observations on both marginal coordinates are uncensored and satisfy certain regularity conditions. The bounds depend on the sample size, on censoring rates and, in particular, on the estimated probability of the unknown tail region. We also discuss using the bootstrap method for variance estimation and bias correction. Two illustrative data examples are analyzed, as well as some simulation results.
Longitudinal control of vehicle platoon via wavelet neural network
(2004)
Hsu, CF
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Wang, WJ
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Lee, TT
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Lin, CM
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電控工程研究所
Transportation technology is one of the most influential areas on the human life. There has been an interest in the development of an automated highway system in which high traffic flow rates may be safely achieved Upon entering the automated highway system, the longitudinal control of car-following collision prevention system will drive a vehicle along the fully automated highway. This paper proposes an intelligent wavelet neural network (IWNN) control system for the car-following collision prevention system based on the wavelet neural network (WNN) approach. The WNN combines the capability of artificial neural networks for learning from processes and the capability of wavelet decomposition for control dynamic systems. In the proposed IWNN system, a WNN controller is used to mimic an ideal controller and a robust controller is designed to compensate for the difference between the ideal controller and the WNN controller. The adaptation laws of the IWNN are derived in the sense of Lyapunov stability analysis, so that the stability of the control system can be guaranteed. Finally, simulation results show that the proposed IWNN control system can achieve favorable tracking performance for a safe car-following control.
Model selection and semiparametric inference for bivariate failure-time data
(2000-03-01)
Wang, WJ
;
Wells, MT
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統計學研究所
;
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.
Nonparametric estimation of the sojourn time distributions for a multipath model
(2003)
Wang, WJ
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統計學研究所
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Institute of Statistics
We use a multipath (multistate) model to describe data with multiple end points. Statistical inference based on the intermediate end point is challenging because of the problems of nonidentifiability and dependent censoring. We study nonparametric estimation for the path probability and the sojourn time distributions between the states. The methodology proposed can be applied to analyse cure models which account for the competing risk of death. Asymptotic properties of the estimators proposed are derived. Simulation shows that the methods proposed have good finite sample performance. The methodology is applied to two data sets.
On assessing the association for bivariate current status data
(2000-12-01)
Wang, WJ
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Ding, AA
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統計學研究所
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Institute of Statistics
Assuming that the two failure times of interest with bivariate current status data follow a bivariate copula model, we propose a two-stage estimation procedure to estimate the association parameter which is related to Kendall's tau. Asymptotic properties of the proposed semiparametric estimator show that, although the first-stage marginal estimators have a convergence rate of only n(1/3), the resulting parameter estimator still converges to a normal random variable with the usual n(1/2) rate. The variance of the proposed estimator can be consistently estimated. Simulation results are presented, and a community-based study of cardiovascular diseases in Taiwan provides an illustrative example.
Power analysis for linear models with spherical errors
(2002-11-01)
Wang, WJ
;
Wells, MT
;
統計學研究所
;
Institute of Statistics
In this article, we consider testing a general linear hypothesis for a regression model when the error distribution belongs to the class of spherical distributions. The distributional robustness of the F-statistics under a null hypothesis for spherically symmetric distributions is well understood. This invariance property, however, does not hold under the alternative hypothesis. Motivated by a simplified example, we study the relationship between power of the test and the error distribution's dispersion and kurtosis. We find that these two parameters are not sufficiently precise measures for determining the power behavior of a test. (C) 2002 Elsevier Science B.V. All rights reserved.
RNN-based prosodic modeling for mandarin speech and its application to speech-to-text conversion
(2002-03-01)
Wang, WJ
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Liao, YF
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Chen, SH
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電信工程研究所
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Institute of Communications Engineering
In this paper, a recurrent neural network (RNN) based prosodic modeling method for Mandarin speech-to-text conversion is proposed. The prosodic modeling is performed in the post-processing stage of acoustic decoding and aims at detecting word-boundary cues to assist in linguistic decoding. It employs a simple three-layer RNN to learn the relationship between input prosodic features, extracted from the input utterance with syllable boundaries pre-determined by the preceding acoustic decoder, and output word-boundary information of the associated text. After the RNN prosodic model is properly trained, it can be used to generate word-boundary cues to help the linguistic decoder solving the problem of word-boundary ambiguity. Two schemes of using these word-boundary cues are proposed. Scheme I modifies the baseline scheme of the conventional linguistic decoding search by directly taking the RNN outputs as additional scores and adding them to all word-sequence hypotheses to assist in selecting the best recognized word sequence. Scheme 2 is an extended version of Scheme I by further using the RNN outputs to drive a finite state machine (FSM) for setting path constraints to restrict the linguistic decoding search. Character accuracy rates of 73.6%, 74.6% and 74.7% were obtained for the systems using the baseline scheme, Schemes I and 2, respectively. Besides, a gain of 17% reduction in the computational complexity of the linguistic decoding search was also obtained for Scheme 2. So the proposed prosodic modeling method is promising for Mandarin speech recognition. (C) 2002 Elsevier Science B.V. All rights reserved.
Signal bias removal with orthogonal transform for adverse Mandarin speech recognition
(2000-04-27)
Wang, WJ
;
Chen, SH
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電信工程研究所
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Institute of Communications Engineering
A new method for applying orthogonal transforms in signal bias removal (SBR) for adverse Mandarin speech recognition (MSR) is proposed. The orthogonal transform process is performed in a moving window manner to extract features from the input speech. Codewords are then obtained by matching high-order, bias-free features with pre-trained codebooks for bias estimation. The effectiveness of the method has been confirmed by an experiment involving multi-speaker adverse continuous MSR. Significant improvements in the recognition accuracy and computation time were achieved as compared with the conventional SBR method.
Synthesis, characterization, thermal and flame-retardant properties of silicon-based epoxy resins
(1999-08-15)
Hsiue, GH
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Wang, WJ
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Chang, FC
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應用化學系
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Department of Applied Chemistry
A new silicon-containing oxirane triglycidyl phenyl silane oxide (TGPSO) and its corresponding silicon-containing epoxy resins are synthesized and characterized. The activation energies of TGPSO curing reaction with various curing agents, including 4,4-diaminodiphenylmethane, 4,4-diaminodiphenylsulfone, and dicyanodiaminde, are found to be 180, 196.5, and 154 kJ/mol. The curing reaction of TGPSO with diamines is determined to be a first-order reaction through means of Arrhenius plots. The introduction of the silicon-containing group results in higher curing reactivity. This silicon-containing resin possesses higher char yield as well as higher limiting oxygen index (LOI = 35) than the commercial epoxy resins, confirming the usefulness of these silicon-containing epoxy resins as flame retardants. Char yields and LOI measurements demonstrate that incorporating silicon into epoxy resins is able to improve their flame retardancy. (C) 1999 John Wiley & Sons, Inc.
Testing independence for bivariate current status data
(2004-03-01)
Ding, AA
;
Wang, WJ
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統計學研究所
;
Institute of Statistics
This article develops a nonparametric procedure for testing marginal independence based on bivariate current status data. Asymptotic properties of the proposed tests are derived, and their finite-sample performance is studied via simulations. The method is applied to analyze data from a community-based study of cardiovascular epidemiology in Taiwan.