Browsing by Author "Chang, CH"

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A Borrow-and-Return model to reduce client waiting time for broadcasting-based VOD services
(2003-06-01)
Yang, MH
;
Chang, CH
;
Tseng, YC
;
資訊工程學系
;
Department of Computer Science
One way to broadcast a popular video is to use multiple channels, each broadcasting a portion of the video periodically. Among the many schemes falling in this category, this paper focuses on several representative schemes (such as FB [15], [18], Pagoda [22], [24], and RFS [26]), which all share a FSFC property by repeatedly broadcasting the First Segment of the video on the First Channel. We propose a general Borrow-and-Return model that can be immediately applied to any scheme owning the FSFC property to reduce the viewer's waiting time without increasing the number of channels required. Given a group of videos, the basic idea is to lend the free time slots of videos without viewers to those videos with viewers to speedup the latter's transmission. By so doing, some bandwidth may be vacated by the borrowing videos to benefit others' transmission. Effectiveness of this model is analyzed by applying it to the FB scheme.
A computational approach to discover differential cooperation of regulatory sites in functionally related genes in yeast genome
(2004-11-01)
Huang, HD
;
Horng, JT
;
Chang, CH
;
Tsou, TS
;
Hong, JY
The availability of genome-wide gene expression data provides a unique set of genes from which to decipher the mechanisms underlying the common transcriptional response. A set of transcription factors which bind to target sites regulate the gene transcription cooperatively. This motivates us to discover the site associations of known transcription factor binding sites and certain repetitive elements. Those over-represented repetitive elements in the promoter regions of functionally related genes are predicted as putative regulatory elements. The study is to analyze how the differential site associations of the known regulatory sites and putative regulatory elements are distributed in the promoter regions of groups of functionally related genes. The functional-specific site associations are discovered by a statistical approach and the over-represented repetitive elements involving in the site associations are possible to be transcription factor binding sites. The site associations facilitate to predict functional-specific putative regulatory elements and to identify genes potentially co-regulated by the putative regulatory elements. Our proposed approach is applied to Saccharomyces cerevisiae and the promoter regions of yeast ORFs.
A fast video-on-demand broadcasting scheme for popular videos
(2004-06-01)
Sheu, JP
;
Wang, HL
;
Chang, CH
;
Tseng, YC
;
資訊工程學系
Broadcasting is a prospective approach to support near video-on-demand services with light communication overhead. By letting clients share channels, such approaches involve partitioning a video into segments and repeatedly broadcasting these segments in multiple channels. An early paper proposed a broadcasting scheme called RFS (recursive frequency splitting), which can significantly reduce clients' waiting time. While efficient, RFS suffers from a high computational complexity of O (n log n), where n is the number of segments of the video, which is typically very large. This paper proposes an efficient segmentation scheme, which can significantly reduce the computational overhead by slightly sacrificing the number of segments that can be arranged as compared to RFS.
A polynomial-perceptron based decision feedback equalizer with a robust learning algorithm
(1995-11-01)
Chang, CH
;
Siu, S
;
Wei, CH
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A new equalization scheme, including a decision feedback equalizer (DFE) equipped with polynomial-perceptron model of nonlinearities and a robust learning algorithm using l(p)-norm error criterion with p < 2, is presented in this paper, This equalizer exerts the benefit of using a DFE and achieves the required nonlinearities in a single-layer net. This makes it easier to train by a stochastic gradient algorithm in comparison with a multi-layer net. The algorithm is robust to aberrant noise for the addressed equalizer and, hence, converges much faster in comparison with the l(p)-norm. A detailed performance analysis considering possible numerical problem for p < 1 is given in this paper. Computer simulations show that the scheme has faster convergence rate and satisfactory bit error rate (BER) performance. It also shows that the new equalizer is capable of approaching the performance achieved by a minimum EER equalizer.
Additive multiplicative increasing functions on nonnegative square matrices and multidigraphs
(2001-09-28)
Chang, CH
;
Chuang, YC
;
Hsu, LH
;
資訊工程學系
;
Department of Computer Science
It is known that if f is a multiplicative increasing function on N, then either f(n) = 0 for all n is an element of N or f (n) = n(alpha) for some alpha greater than or equal to 0. It is very natural to ask if there are similar results in other algebraic systems. In this paper, we first study the multiplicative increasing functions. over nonnegative square matrices with respect to tensor product and then restrict our result to multidigraphs and loopless multidigraphs. (C) 2001 Elsevier Science B.V. All rights reserved.
Bandwidth brokers of instantaneous and Book-ahead requests for Differentiated Services networks
(2001)
Lin, YD
;
Chang, CH
;
Hsu, YC
;
資訊工程學系
;
Department of Computer Science
The Quality of Service (QoS) reservations in Differentiated Service (DiffServ) networks can be classified into two sets; Book-ahead (BA) requests and Instantaneous Requests (IRs). When an admitted BA request becomes active, some ongoing IRs are dropped when the bandwidth is insufficient for supporting both IRs and BA requests. The admission control should predict the lifetime, i.e. look-ahead time, of the IRs to prevent the admitted IRs from being dropped. The control should then check whether the available bandwidth during the look-ahead time is sufficient for the incoming IRs. We propose an application-aware look-ahead admission control for IRs, which determines the look-ahead time for specific types of IR applications. An admitted BA request might block subsequent ones that could bring more effective revenue. Thus, we propose the deferrable model of the admission control for BA requests. Simulation results indicate that the application-aware look-ahead admission control successfully reduces the dropping probability and wasted revenue of IRs by up to 10 times and 30%, respectively. Besides, the deferrable model indeed results in more BA effective revenue.
Bandwidth brokers of instantaneous and book-ahead requests for differentiated services networks
(2002-01-01)
Lin, YD
;
Chang, CH
;
Hsu, YC
;
資訊工程學系
;
Department of Computer Science
The Quality of Service (QoS) reservations in Differentiated Service (DiffServ) networks can be classified into two sets: Book-ahead (BA) requests and Instantaneous Requests (IRs). When an admitted BA request becomes active, some ongoing IRs is dropped when the bandwidth is insufficient for supporting both IRs and BA requests. The admission control should predict the lifetime, i.e. look-ahead time, of the IRs to prevent the admitted IRs from being dropped, The control should then check whether the available bandwidth during the look-ahead time is sufficient for the incoming IRs. We propose an application-aware look-ahead admission control for IRs, which determines the lookahead time for specific types of IR applications. An admitted BA request might block subsequent ones that could bring more effective revenue. Thus, we propose the deferrable model of the admission control for BA requests, Simulation results indicate that the application-aware look-ahead admission control successfully reduces the dropping probability and wasted revenue of IRs by up to 10 times and 30%, respectively. Besides, the deferrable model indeed results in more BA effective revenue.
Bayesian analysis of a growth curve model with a general autoregressive covariance structure
(2000-12-01)
Lee, JC
;
Chang, CH
;
交大名義發表
;
National Chiao Tung University
In this paper wt: consider from maximum likelihood and Bayesian points of view the generalized growth curve model when the covariance matrix has a Toeplitz structure. This covariance is a generalization of the AR(I) dependence structure. Inferences on the parameters as well as the future values are Included. The results are illustrated with several real data sets.
Catalytic wheel as Brownian motor and its core engine
(2005-01-01)
Tsong, TY
;
Chang, CH
;
交大名義發表
;
National Chiao Tung University
Catalytic wheel, Brownian motor, and biological energy transduction
(2005-02-01)
Tsong, TY
;
Chang, CH
;
物理研究所
;
Institute of Physics
An enzyme turns over, or recycles during each catalytic process. It is a catalytic wheel, analogous to a motor, or an engine. The fuel, or the driving force for the wheel, is the free energy of the substrate (S) to product (P) conversion (DeltaG(R)), or a free energy output of a coupled chemical reaction. When DeltaG(R) of the S --> P reaction is negative the reaction is spontaneous and the down-hill wheel motion requires no external input of energy. When DeltaG(R) is positive the wheel must turn uphill against a workload, a reaction that produces energy must be coupled to the wheel. The synthesis of ATP from ADP and P-i in a cell is an uphill reaction and the energy required for the synthesis is derived from the dissipation of a proton gradient, or an electric potential. This article focuses on mechanisms of action of the uphill catalytic wheels. It is shown that the coupling of an external energy source to an uphill catalytic wheel can be done, with nearly 100% efficiency, by mechanisms of the Brownian Motor. Theory of electroconformational coupling (TEC) is used to construct a Brownian motor, and electric activation of an ion pump, Na, K-ATPase is used to demonstrate its basic principles. A TEC Motor has three essential elements: 1) the ability of the protein to interact with an electric field, 2) existence of at least two conformations of protein that oscillate or fluctuate on interaction with the applied field, and 3) a built-in asymmetry in the molecular interactions with substrate and product. It is shown that the TEC Motor is a generic model and applicable to other types of biological energy transducers.
Characterization and conductive coating of phosphors for improved brightness
(2005-04-30)
Chang, CH
;
Chiou, BS
;
Chen, KS
;
Ho, JC
;
電子工程學系及電子研究所
In this study, the phosphors used in CRTs are coated with In2O3 conductive layer derived from the hydrolysis of indium chloride. The conductive coating retards/eliminates charging-up on the phosphor surface during the bombardment of the electrons and improves the cathodoluminescent brightness of the phosphor. However, the non-emissive conductive coating also degrades the cathodoluminescent brightness when it is too thick. The cathodoluminescent brightness increases initially with the amount of coating, reaches a maximum at 10 wt.% InCl3, and decreases with further increase of coating. It is found that with a 10 wt.% InCl3 coating, the brightness of phosphor increases by 20% at 500 V and 1 mu A. (c) 2004 Published by Elsevier B.V.
Coalesced single-input single-output dual-band filter
(2003)
Chang, CH
;
Wu, HS
;
Yang, HJ
;
Tzuang, CKC
;
電信工程研究所
An experimental proof-of-concept two-terminal single-input and single-output (SISO) 1.7GHz/4.1GHz; dual-band filter is presented. It incorporates the so-call frequency-selective resonators that are composite in structure, cascading a microstrip and microstrip on a two-dimensional periodical surface or the so-called PBG(photonic bandgap) ground plane. The composite resonators add additional degrees of freedom for controlling the relative positions of the passband center frequencies, Thus making the dual-band filters, which essential share one common layout. Measured and theoretical filter characteristics for such coalesced dual-band filter agree excellently, validating the proposed concepts.
Different kinds of analysis methods on a rectangular combined function bending magnet
(1996-12-11)
Hwang, CS
;
Chang, CH
;
Tseng, PK
;
Uen, TM
;
LeDuff, J
Magnetic field features of a rectangular combined function bending magnet are different from the sector magnet. A strong edge focusing factor (i.e., thin lens effect) intrinsically exists at the two magnet edges for the rectangular bending magnet. Therefore, in this study, we develop two kinds of Hall probe mapping trajectory with four analysis methods to measure and analyze the bending magnet's field behavior. A sufficient correlation among the four methods is an important feature. Those methods are individually used to derive the pole face tilt and bent, the effective magnetic length and to check the specification establish by the beam dynamics group. As for the two mapping methods, one is called ''Radial Mapping'' whose mapping trajectories in the longitudinal direction (s-axis) follow the different are lengths of radius rho+/-r and the transverse trajectories follow the radial displacement +/-r perpendicular to the are trajectory. The other one is called ''Lamination Mapping'' whose mapping trajectories in the longitudinal direction follow the constant are length of circle radius rho and the transverse trajectories follow the transverse axis displacement +/-x parallel to the lamination direction. This study also discusses the differences between those two mapping methods. Results obtained from the harmonic field distribution along the longitudinal direction (including the fringing field) and the main components of the integral strength are compared. The subsequent error of the four analysis methods is 0.01% for the dipole strength and 0.3% for the quadrupole strength individually. According to the specifications, those analysis errors are acceptable. Meanwhile, the accuracies of different methods for the higher multipole strengths are all within tolerances. The peculiar sextupole field behavior at the two magnet edges from the different mapping methods is owing to the effective magnet pole face that will be discussed.
Different kinds of analysis methods on a rectangular combined function bending magnet
(1996-12-11)
Hwang, CS
;
Chang, CH
;
Tseng, PK
;
Uen, TM
;
LeDuff, J
Magnetic field features of a rectangular combined function bending magnet are different from the sector magnet. A strong edge focusing factor (i.e., thin lens effect) intrinsically exists at the two magnet edges for the rectangular bending magnet. Therefore, in this study, we develop two kinds of Hall probe mapping trajectory with four analysis methods to measure and analyze the bending magnet's field behavior. A sufficient correlation among the four methods is an important feature. Those methods are individually used to derive the pole face tilt and bent, the effective magnetic length and to check the specification establish by the beam dynamics group. As for the two mapping methods, one is called ''Radial Mapping'' whose mapping trajectories in the longitudinal direction (s-axis) follow the different are lengths of radius rho+/-r and the transverse trajectories follow the radial displacement +/-r perpendicular to the are trajectory. The other one is called ''Lamination Mapping'' whose mapping trajectories in the longitudinal direction follow the constant are length of circle radius rho and the transverse trajectories follow the transverse axis displacement +/-x parallel to the lamination direction. This study also discusses the differences between those two mapping methods. Results obtained from the harmonic field distribution along the longitudinal direction (including the fringing field) and the main components of the integral strength are compared. The subsequent error of the four analysis methods is 0.01% for the dipole strength and 0.3% for the quadrupole strength individually. According to the specifications, those analysis errors are acceptable. Meanwhile, the accuracies of different methods for the higher multipole strengths are all within tolerances. The peculiar sextupole field behavior at the two magnet edges from the different mapping methods is owing to the effective magnet pole face that will be discussed.
Enzymatic formation of multiple triterpenes by mutation of tyrosine 510 of the oxidosqualene-lanosterol cyclase from Saccharomyces cerevisiae
(2004-12-03)
Wu, TK
;
Chang, CH
;
應用化學系分子科學碩博班
;
Institute of Molecular science
Enzymatic formation of multiple triterpenes by mutation of tyrosine 510 of the oxidosqualene-lanosterol cyclase from Saccharomyces cerevisiae.
(2005-03-13)
Chang, CH
;
Wu, TK
;
生物科技學系
;
Department of Biological Science and Technology
Enzyme as catalytic wheel powered by a Markovian engine: conformational coupling and barrier surfing models
(2005-05-01)
Tsong, TY
;
Chang, CH
;
物理研究所
;
Institute of Physics
We examine a typical Michaelis-Menten Enzyme (MME) and redress it to form a transducer of free energy, and electric, acoustic, or other types of energy. This amendment and extension is necessary in lieu of recent experiments in which enzymes are shown to perform pump, motor, and locomotion functions resembling their macroscopic counterparts. Classical textbook depicts enzyme, or an MME, as biocatalyst which can enhance the rate of a chemical reaction by lowering the activation barrier but cannot shift the thermodynamic equilibrium of the biochemical reaction. An energy transducer, on the other hand, must also be able to harvest, store, or divert energy and in doing so alter the chemical equilibrium, change the energy form, fuel an energy consuming process, or perform all these functions stepwise in one catalytic turnover. The catalytic wheel presented in this communication is both a catalyst and an energy transducer and can perform all these tasks with ease. A Conformational Coupling Model for the rotary motors and a Barrier Surfing Model for the track-guided stepping motors and transporters, are presented and compared. It is shown that the core engine of the catalytic wheel, or a Brownian motor, is a Markovian engine. It remains to be seen if this core engine is the basic mechanism for a wide variety of bio-molecular energy transducers, as well as certain other dynamic systems, for example, the Parrondo's Games. (c) 2004 Elsevier B.V. All rights reserved.
Estimation of dynamic origin-destination by Gaussian state space model with unknown transition matrix
(2003)
Jou, YJ
;
Hwang, MC
;
Wang, YH
;
Chang, CH
;
統計學研究所
Dynamic origin-destination (O-D) pattern representing time-dependent trip demands from one place (origin) to another (destination) is one of the most essential input data for most traffic operational analyses. Historical studies assumed that the transition matrix is known or at least approximately known, which is unrealistic for a real world network. And due to the fact that the number of trips to a specific destination, y, is easy to obtain and the O-D variable, x (path flow based in this research), is not directly observable, a Gaussian state space model is formulated to describe the relationships of x and y, observation equations, and the dynamics of x, state equations with unknown transition matrix. Under the assumption of Gaussian noise terms in state space model, the distribution of random transition matrix F is derived. A solution algorithm combining Gibbs sampler and Kalman filter to tackle the problem of simultaneous estimation of F and x, based on the latest available information is proposed. Real O-D data from Taipei Rapid Transit is used to verify the presented model and solution method. Preliminary results are generally satisfactory, showing that also in the unknown transition matrix case, significant estimates are achieved.
Exploration of glycosyl hydrolase family 75, a chitosanase from Aspergillus fumigatus
(2006-02-10)
Cheng, CY
;
Chang, CH
;
Wu, YJ
;
Li, YK
;
交大名義發表
A powerful endo-chitosanase ( CSN) previously described for a large scale preparation of chito-oligosaccharides ( Cheng, C.-Y., and Li, Y.-K. ( 2000) Biotechnol. Appl. Biochem. 32, 197 - 203) was cloned from Aspergillus fumigatus and further identified as a member of glycosyl hydrolase family 75. We report here a study of gene expression, functional characterization, and mutation analysis of this enzyme. Gene cloning was accomplished by reverse transcription-PCR and inverse PCR. Within the 1382-bp Aspergillus gene ( Gen-Bank (TM) accession number AY190324), two introns ( 67 and 82 bp) and an open reading frame encoding a 238-residue protein containing a 17-residue signal peptide were characterized. The recombinant mature protein was overexpressed as an inclusion body in Escherichia coli, rescued by treatment with 5 M urea, and subsequently purified by cation exchange chromatography. A time course H-1 NMR study on the enzymatic formation of chito-oligosaccharides confirmed that this A. fumigatus CSN is an inverting enzyme. Tandem mass spectrum analysis of the enzymatic hydrolysate revealed that the recombinant CSN can cleave linkages of GlcNAc-GlcN and GlcN-GlcN in its substrate, suggesting that it is a subclass I chitosanase. In addition, an extensive site-directed mutagenesis study on 10 conserved carboxylic amino acids of glycosyl hydrolase family 75 was performed. This showed that among these various mutants, D160N and E169Q lost nearly all activity. Further investigation using circular dichroism measurements of D160N, E169Q, wild-type CSN, and other active mutants showed similar spectra, indicating that the loss of enzymatic activity in D160N and E169Q was not because of changes in protein structure but was caused by loss of the catalytic essential residue. We conclude that Asp(160) and Glu(169) are the essential residues for the action of A. fumigatus endo-chitosanase.
Exploration of glycosyl hydrolase family 75, a chitosanase from Aspergillus fumigatus
(2006-02-10)
Cheng, CY
;
Chang, CH
;
Wu, YJ
;
Li, YK
;
應用化學系
A powerful endo-chitosanase ( CSN) previously described for a large scale preparation of chito-oligosaccharides ( Cheng, C.-Y., and Li, Y.-K. ( 2000) Biotechnol. Appl. Biochem. 32, 197 - 203) was cloned from Aspergillus fumigatus and further identified as a member of glycosyl hydrolase family 75. We report here a study of gene expression, functional characterization, and mutation analysis of this enzyme. Gene cloning was accomplished by reverse transcription-PCR and inverse PCR. Within the 1382-bp Aspergillus gene ( Gen-Bank (TM) accession number AY190324), two introns ( 67 and 82 bp) and an open reading frame encoding a 238-residue protein containing a 17-residue signal peptide were characterized. The recombinant mature protein was overexpressed as an inclusion body in Escherichia coli, rescued by treatment with 5 M urea, and subsequently purified by cation exchange chromatography. A time course H-1 NMR study on the enzymatic formation of chito-oligosaccharides confirmed that this A. fumigatus CSN is an inverting enzyme. Tandem mass spectrum analysis of the enzymatic hydrolysate revealed that the recombinant CSN can cleave linkages of GlcNAc-GlcN and GlcN-GlcN in its substrate, suggesting that it is a subclass I chitosanase. In addition, an extensive site-directed mutagenesis study on 10 conserved carboxylic amino acids of glycosyl hydrolase family 75 was performed. This showed that among these various mutants, D160N and E169Q lost nearly all activity. Further investigation using circular dichroism measurements of D160N, E169Q, wild-type CSN, and other active mutants showed similar spectra, indicating that the loss of enzymatic activity in D160N and E169Q was not because of changes in protein structure but was caused by loss of the catalytic essential residue. We conclude that Asp(160) and Glu(169) are the essential residues for the action of A. fumigatus endo-chitosanase.