Browsing by Author "Chang, CW"

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A video information system for sport motion analysis
(1997-06-01)
Chang, CW
;
Lee, SY
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
In this paper, we present several important methods in a video information system for sport motion analysis. We first describe an efficient method for computing the position of one or more moving objects in a video sequence. We utilize computer vision routines for both target object tracking and feature value extraction. Then, we propose a multiple subsequence matching mechanism for comparing the difference in object motion between two video sequences. A mapping function, penalty table and the overall distance between two video sequences have been defined. We use the prominent feature points as our segmentation positions and separate the sequence into several subsequence groups. After an alignment process, we can find the mapping of the best matching and get an evaluation report between the two video sequences for motion analysis. The video information system described in this paper has successfully analysed several examples of sport motion, and is representative of techniques commonly used in practice. (C) 1997 Academic Press Limited.
A video information system for sport motion analysis
(1997-06-01)
Chang, CW
;
Lee, SY
;
交大名義發表
;
資訊科學與工程研究所
;
National Chiao Tung University
In this paper, we present several important methods in a video information system for sport motion analysis. We first describe an efficient method for computing the position of one or more moving objects in a video sequence. We utilize computer vision routines for both target object tracking and feature value extraction. Then, we propose a multiple subsequence matching mechanism for comparing the difference in object motion between two video sequences. A mapping function, penalty table and the overall distance between two video sequences have been defined. We use the prominent feature points as our segmentation positions and separate the sequence into several subsequence groups. After an alignment process, we can find the mapping of the best matching and get an evaluation report between the two video sequences for motion analysis. The video information system described in this paper has successfully analysed several examples of sport motion, and is representative of techniques commonly used in practice. (C) 1997 Academic Press Limited.
AlGaInP light-emitting diodes with stripe patterned omni-directional reflector
(2006-02-01)
Lee, YJ
;
Lu, TC
;
Kuo, HC
;
Wang, SC
;
Liou, MJ
An n-side-up AlGaInP-based light-emitting diode (LED) with a stripe-patterned omni-directional reflector (ODR) was fabricated by adopting the adhesive-layer bonding scheme. Comparing to the conventional ODR LED, the stripe-patterned ODR LED significantly enhanced the output power with an only slight higher forward voltage. This improvement was analyzed by the scanning near-field optical microscope (SNOM) and could be attributable to the geometrical shape of stripe patterns that redirects the guided light towards to the escaping cone of the LED surface. The optimized dimension of stripe patterns was also calculated by simply modeling a LED dice with a stripe-patterned ODR structure, according to optical ray-tracing method.
Automatic cel painting in computer-assisted cartoon production using similarity recognition
(1997-07-01)
Chang, CW
;
Lee, SY
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
The task of painting each eel of an animated sequence has always been a tedious work using traditional methods. In order to simplify and speed up the process, the development of an automatic eel painting system is desired. This paper presents a method for assisting the production of cartoon animation using computers in order to reduce the production expense and to improve the overall quality. It signals a great improvement in the working environment where 2-D animation Is produced. The basic idea of our automatic eel painting mechanism is to extract both statistical and topological features of regions from input animation drawings, and to search for similar corresponding regions in the previous drawing, If the similarity measures are within the accepted thresholds, the corresponding colour will be inherited. A new integrated labelling algorithm constructing statistical region and topological graph features is proposed. Furthermore, a similarity measure of regions is defined and an algorithm of partial matching of attribute graphs is presented. The experimental result shows the feasibility and practicability of the proposed approach. (C) 1997 by John Wiley & Sons, Ltd.
Automatic cel painting in computer-assisted cartoon production using similarity recognition
(1997-07-01)
Chang, CW
;
Lee, SY
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
The task of painting each eel of an animated sequence has always been a tedious work using traditional methods. In order to simplify and speed up the process, the development of an automatic eel painting system is desired. This paper presents a method for assisting the production of cartoon animation using computers in order to reduce the production expense and to improve the overall quality. It signals a great improvement in the working environment where 2-D animation Is produced. The basic idea of our automatic eel painting mechanism is to extract both statistical and topological features of regions from input animation drawings, and to search for similar corresponding regions in the previous drawing, If the similarity measures are within the accepted thresholds, the corresponding colour will be inherited. A new integrated labelling algorithm constructing statistical region and topological graph features is proposed. Furthermore, a similarity measure of regions is defined and an algorithm of partial matching of attribute graphs is presented. The experimental result shows the feasibility and practicability of the proposed approach. (C) 1997 by John Wiley & Sons, Ltd.
Constructing quantitative models from qualitative mutant phenotypes: preferences in selecting sensory organ precursors
(2006-06-01)
Hsu, CP
;
Lee, PH
;
Chang, CW
;
Lee, CT
;
應用化學系分子科學碩博班
Motivation: To study biology from the systems level, mathematical models that describe the time-evolution of the system offer useful insights. Quantitative information is required for constructing such models, but such information is rarely provided. Results: We propose a scheme-based on random searches over a parameter space, according to criteria set by qualitative experimental observations-for inferring quantitative parameters from qualitative experimental results. We used five mutant constraints to construct genetic network models for sensory organ precursor formation in Drosophila development. Most of the models were capable of generating expression patterns for the gene Enhancer of split that were compatible with experimental observations for wild type and two Notch mutants. We further examined factors differentiating the neural fate among cells in a proneural cluster, and found two opposite driving forces that bias the choice between middle cells and the peripheral cells. Therefore, it is possible to build numerical models from mutant screening and to study mechanisms behind the complicated network.
Design and analyses of compact bent-tapered waveguides using guided-wave lens sets
(2004-08-20)
Chang, CW
;
Hsieh, WF
;
光電工程學系
;
Department of Photonics
We propose compact bent-tapered waveguides using guided-wave lens sets, which are constructed by disposing lens-shaped waveguide regions in planar tapered waveguides. Two applications of the abruptly bent tapered waveguide and the Z-bend tapered waveguide demonstrate high transmittances of 91% and 86% with bent and tapered angles of 10degrees. (C) 2004 Wiley Periodicals, Inc.
Design of low-loss tapered waveguides using the telescope structure compensation
(2003-10-01)
Chang, CW
;
Wu, ML
;
Hsieh, WF
;
光電工程學系
;
Department of Photonics
A low-loss tapered waveguide is achieved by the telescope structure compensation. The configuration of this design is similar to the Galilean telescope based on the bulk geometrical optics. We numerically calculate the transmission efficiency in the use of the beam propagation method (BPM) and the finite-difference time-domain method. The BPM simulation results reveal that the normalized transmission efficiency is more than 95%, even if the tapered angle is as large as 10degrees.
Determination of dynamic elastic constants of transversely isotropic rocks using a single cylindrical specimen
(1997-10-01)
Liao, JJ
;
Hu, TB
;
Chang, CW
;
交大名義發表
;
土木工程學系
A new experimental procedure and its associated interpretation theories are proposed to determine the five dynamic elastic constants of a transversely isotropic rock. Using Christoffel's equations, the elastic constants can be uniquely determined based on ultrasonic wave velocity measurements on a single cylindrical specimen. The new method requires that the orientation of planes of elastic symmetry by parallel to its longitudinal axis. The wave velocity measuring devices (i.e. transducers) can be mounted on the sides or ends of the specimen. The new method has been implemented in the laboratory on a transversely isotropic rock, argillite. Wave velocity measurements were taken on specimens with and without a tensile load applied at the ends. Consistent results were obtained in both cases. This paper describes details of the analytical background and the proposed experimental procedure. Available test results are presented to demonstrate the efficacy of the new method. (C) 1997 Elsevier Science Ltd.
Determination of dynamic elastic constants of transversely isotropic rocks using a single cylindrical specimen
(1997-10-01)
Liao, JJ
;
Hu, TB
;
Chang, CW
;
土木工程學系
;
Department of Civil Engineering
A new experimental procedure and its associated interpretation theories are proposed to determine the five dynamic elastic constants of a transversely isotropic rock. Using Christoffel's equations, the elastic constants can be uniquely determined based on ultrasonic wave velocity measurements on a single cylindrical specimen. The new method requires that the orientation of planes of elastic symmetry by parallel to its longitudinal axis. The wave velocity measuring devices (i.e. transducers) can be mounted on the sides or ends of the specimen. The new method has been implemented in the laboratory on a transversely isotropic rock, argillite. Wave velocity measurements were taken on specimens with and without a tensile load applied at the ends. Consistent results were obtained in both cases. This paper describes details of the analytical background and the proposed experimental procedure. Available test results are presented to demonstrate the efficacy of the new method. (C) 1997 Elsevier Science Ltd.
Effects of N2O fluence on the PECVD-grown Si-rich SiOx with buried Si nanocrystals
(2005)
Lin, CJ
;
Kuo, HC
;
Chen, CY
;
Chueh, YL
;
Chou, LJ
The optimized N2O fluence is demonstrated for plasma enhanced chemical vapor deposition (PECVD) of Si-rich substoichiometric silicon oxide (SiOx) films with buried Si nanocrystals. Strong room-temperature photoluminescence (PL) at 550-870 rim has been observed in SiOx films grown by PECVD under a constant SiH4 fluence of 20 sccm with an N2O fluence varying from 105 sccm to 130 sccm. A 22-nm-redshift in the central PL wavelength has been detected after annealing from 15 min to 180 min. The maximum PL irradiance is observed from the SiOx film grown at the optimal N2O fluence of 120 sccm after annealing for 30 minutes. Larger N2O fluence or longer annealing time leads to a PL band that is blue-shifted by 65 nm and 20 nm, respectively. Such a blue shift is attributed to shrinkage in the size of the Si nanocrystals with the participation of oxygen atoms from N2O incorporated within the SiOx matrix. The (220)-oriented Si nanocrystals exhibit radii ranging from 4.4 nm to 5.0 nm as determined by transmission electron microscopy (TEM). The luminescent lifetime lengthens to 52 mu s as the nc-Si size increase to > 4 nm. Optimal annealing times for SiOx films prepared at different N2O fluences are also reported. A longer annealing process results in a stronger oxidation effect in SiOx films prepared at higher N2O fluences, yielding a lower PL irradiance at shorter wavelengths. In contrast, larger Si nanocrystals can be precipitated when the N2O fluence becomes lower; however, such a SiOx film usually exhibits weaker PL at longer wavelength due to a lower nc-Si density. These results indicate that a N2O/SiH4 fluence ratio of 6:1 is the optimized PECVD growth condition for the Si-rich SiO2 wherein dense Si nanocrystals are obtained after annealing.
Error statistics of closed-loop power control in multirate DS-CDMA cellular systems
(2002)
Wang, LC
;
Chang, CW
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, we investigate the error statistics of the close-loop power control scheme with variable spreading factors for the multi-rate services in the third generation wideband CDMA (WCDMA) system. We demonstrate that the long scrambling pseudo-noise code, besides its well known feature in differentiating users and base stations, can improve power control false command over a frequency-selective fading channel as well. Our computer simulation results indicate that the SIR measurement error can be reduced by 3 dB in a typical case, and the power control false command can be reduced from 27 % to 10 % in comparison to using pure short Walsh codes. It will be shown that the close-loop power control error is a composite function of spreading factor, target E-b / N-o and Doppler frequency. The statistics of closed loop power control false command can be easily characterized by a Bernoulli distribution with a parameter provided by our results.
Fabrication and micro-photoluminescence investigation of Mg-doped gallium nitride nanorods
(2005-04-01)
Chang, YH
;
Hsueh, TH
;
Lai, FI
;
Chang, CW
;
Yu, CC
High-density magnesium (Mg)-doped gallium nitride (GaN) nanorods were fabricated by inductively coupled plasma reactive ion etching from a GaN film and had a mean length of approximately 50nm. A large blue-shift was observed in the photoluminescence (PL) peak energy of Mg-doped GaN nanorods under HeCd laser (325 nm) excitation. The PL spectra of the nanorods show a typical donor-acceptor-pair (DAP) emission at approximately 3.0 eV with a large blue-shift compared to that of the Mg-doped GaN film. The blue-shift energy increases from 8 meV to 67 meV as the excitation intensity varies from 12 kW/cm(2) to 56 kW/cm(2). Possible reasons for the power dependence of the spectral shift in the PL emission energy are discussed.
Fabrication of magnesium-doped gallium nitride nanorods and microphotoluminescence characteristics
(2006-05-01)
Lai, FI
;
Kuo, SY
;
Chang, YH
;
Huang, HW
;
Chang, CW
High density magnesium (Mg)-doped gallium nitride (GaN) nanorods were fabricated by inductively coupled plasma reactive ion etching technique from the epitaxial film. Under the fixed Cl-2/Ar flow rate of 10/25 SCCM (SCCM denotes cubic centimeter per minute at STP) and inductively coupled plasma/bias power of 200/200 W, the nanorods were fabricated with a density of 10(8)-10(10) cm(2) and dimension of 20-100 nm by varying the chamber pressure from 10 to 30 mTorr. A large blueshift was observed in the photoluminescence (PL) peak energy of Mg-doped GaN nanorods under HeCd laser (325 nm) excitation. The PL spectra of nanorods show a typical donor-acceptor-pair emission around 3.0 eV with a large blueshift compared to the Mg-doped GaN film. The blueshift energy increases from 8 to 67 meV as the excitation intensity varies from 12 to 56 kW/cm(2). Possible reasons causing the power dependence of spectral shift in the PL emission energy are discussed. 2006 American Vacuum Society.
Femtosecond fluorescence dynamics of trans-azobenzene in hexane on excitation to the S-1(n,pi*) state
(2002-10-01)
Lu, YC
;
Chang, CW
;
Diau, EWG
;
應用化學系
;
Department of Applied Chemistry
Femtosecond fluorescence dynamics of trans-azobenzene in hexane have been investigated on excitation to the S-1(n,pi*) state at 432 nm using the up-conversion technique. Two transient components were observed to represent the fast and the slow S-1 fluorescence dynamics in the wavelength range of 550-732 nm. Based on the results obtained from recent ab initio calculations (Ishikawa, T.; Noro, T.; Shoda, T., J. Chem. Phys. 2001, 115, 7503), a dynamical picture is given in the following. Upon initial excitation to the S, state, the excited molecule is moving away from the first detection window within the observed 200-300 fs. The structural relaxation from the Franck-Condon region may be responsible for the observed fast S-1 dynamics with the driving force being the CNNC twisting motion along the rotational coordinate. For the rest of the motion on the S-1 global potential surface, the excited molecule may search for the S-0/S-1 conical intersection for an efficient internal conversion to the ground state. The nuclear motions for the observed slow S-1 dynamics not only involve the CNNC torsional coordinate but also the other degrees of freedom such as the CNN bending coordinate on the multidimensional S-1 potential energy surface. The whole electronic relaxation process occurs within the observed 1-2 ps. The slow S-1 dynamics were found to vary with the fluorescence wavelengths due to the influence of the solvent-induced vibrational relaxation in the S-1 state; the vibrational relaxation should occur on a time scale comparable to the time scale of the electronic relaxation (S-1-->S-0 internal conversion).
Fluorescence lifetime and nonradiative relaxation dynamics of DCM in nonpolar solvent
(2003-06-04)
Chang, CW
;
Kao, YT
;
Diau, EWG
;
應用化學系
;
應用化學系分子科學碩博班
The nonradiative dynamics of DCM in hexane have been investigated using femtosecond fluorescence up conversion technique at three excitation wavelengths (400, 445 and 480 nm). The S, lifetime was observed to be 9.8 +/- 0.5 ps, which is independent of the excitation and the fluorescence wavelengths. The observed S, lifetimes of DCJT and DCJTB are slower than those of DCM and DCMB by one order of magnitude, indicating the significance of the twisting motion of the amino group affecting the S, nonradiative dynamics. TDDFT calculations suggest that an intersystem crossing is responsible for the observed S, dynamics of DCM in nonpolar solvent. (C) 2003 Elsevier Science B.V. All rights reserved.
Formation of nanostructures of hexaphenylsilole with enhanced color-tunable emissions
(2006-02-26)
Bhongale, CJ
;
Chang, CW
;
Diau, EWG
;
Hsu, CS
;
Dong, YQ
Nanostructures of 1,1,2,3,4,5-hexaphenylsilole (HPS) of various types were obtained on simple reprecipitation with THF as solvent and water as non-solvent. The formation and evolution of these nanostructures were monitored with scanning electron microscopy. Using picosecond time-correlated single-photon counting, we observed enhanced emission and fluorescence lifetimes at volume fractions 70-90% of added water. We report the first enhanced color-tunable emissions of a conjugated organic compound (HPS) due to the formation of nanoflowers, nanoglobules and microglobules, and provide time scales for those nanostructures and the corresponding intermolecular interactions in the aggregates. (c) 2005 Elsevier B.V. All rights reserved.
Gap-processing time analysis of an indicator-based stall avoidance mechanism for high speed downlink packet access
(2005)
Wang, LC
;
Chang, CW
;
Chang, CJ
;
電信工程研究所
;
Institute of Communications Engineering
For supporting high speed downlink packet access (HSDPA) in the wideband code division multiple access (WCDMA) system, an indicator-based stall avoidance mechanism was recently proposed to remove the nonrecoverable gap in the received out-of-sequence packets. The stall of delivering medium access control (MAC) layer data to the upper layer is a serious problem when a negative acknowledgement (NACK) control signal becomes an acknowledgement (ACK) signal in the multiprocess stop-and-wait (SAW) hybrid automatic repeat request (HARQ) mechanism. This paper presents an analytical model to calculate the gap-processing time of the indicator-based stall avoidance mechanism. Instead of time-consuming simulations, the gap-processing time of the indicator-based stall avoidance in the multi-process SAW HARQ mechanism in the HSDPA system can be calculated easily by the proposed method for different packet error rates, various numbers of allowable users, and different numbers of parallel processes in the SAW HARQ mechanism. Numerical results are performed in a Rayleigh fading channel to demonstrate the effectiveness of the proposed method in understanding the performance tradeoffs of the multi-process HARQ mechanism in HSDPA.
Gap-processing time analysis of stall avoidance mechanisms for high speed downlink packet access with parallel HARQ schemes
(2005)
Wang, LC
;
Chang, CW
;
電信工程研究所
;
Institute of Communications Engineering
The parallel multi-channel stop-and-wait (SAW) hybrid. automatic repeat request (HARQ) mechanism is one of key technologies for high speed downlink packet access in the wideband code division multiple access system. However, this parallel HARQ mechanism may encounter a serious stall problem, resulted from the error of the negative acknowledgement (NACK) changing to the acknowledgement (ACK) in the control channel. In the stall situation, the receiver waits for a packet that will be no longer sent by the transmitter and stops delivering the medium access control (MAC) layer packets to the upper layer. The stall issue seriously degrades the quality of service for the high speed mobile terminal owing to the high probability of NACK-to-ACK errors. In this paper, we present an analytical approach to compare three stall avoidance schemes: the timer-based, the window-based, and the indicator-based schemes. To this end, we first define a new performance metric - the gap-processing time the duration for a nonrecoverable gap appearing in the MAC layer re-ordering buffer until it is recognized. Second, we derive the closed-form expressions for the average gap-processing time of these three stall avoidance schemes. It will be shown that our analytical results match the simulations well. Further, by analysis we demonstrate that the indicator-based stall avoidance scheme outperforms the. timer-based and the window-based schemes. The developed analytical approaches provide important insight into determining a proper number of processes in the parallel SAW HARQ mechanism when applying the indicator-based stall avoidance scheme. Moreover, our analysis can facilitate the physical/MAC/radio link control cross-layer design because the gap-processing time is closely related to packet error rate in the physical layer, reordering buffer size in the MAC and RLC layer.
Guided-wave microlens array applications to compact 1x8 planar waveguide splitters
(2004-10-05)
Chang, CW
;
Hsieh, WF
;
光電工程學系
;
Department of Photonics
A compact 1 x 8 waveguide splitter using a guided-wave microlens array is presented and analyzed to show low insertion loss and output imbalance of 0.28 and 0.15 dB, respectively. The analysis results show that the proposed equal-power splitter with insensitive wavelength responses and acceptable fabrication tolerances is applicable for compact and wide-bandwidth integrated optical devices. (C) 2004 Wiley Periodicals, Inc.