Browsing by Author "Chen, YY"

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A chitosanase from Paecilomyces lilacinus with binding affinity for specific chito-oligosaccharides
(2005-04-01)
Chen, YY
;
Cheng, CY
;
Haung, TL
;
Li, YK
;
應用化學系
A purple-spore, rhizosphere-inhabiting nematophagous fungus, further identified as Paecilomyces lilacinus, was found to grow on chitosanase-detecting plate. An induced endochitosanase having a molecular mass of 23 kDa was purified from the culture medium by a single cation-exchange column-chromatography step. Its optimum pH, optimum temperature and pi were found to be 6.0, 50 degrees C and 8.3 respectively. The N-terminal amino acid sequence of the purified enzyme was partially determined. On the basis of the partial sequence XQLPANLXXIYD and the BLAST results, the purified chitosanase was classified as a new member of the family 75 glycohydrolases. Complete hydrolysis of 95% deacetylated chitosan by the isolated chitosanase released chitotriose, chitotetraose and chitopentaose as the major hydrolytic products. Two oligosaccharides, which were further determined to be GlcN-GlcN-GlcNAc and GlcNAc-GlcN-GlcN-GlcNAc by chemical methylation followed by liquid chromatography-tandem MS analysis, were obtained after the denaturation of the purified chito-sanase. This is the first documented finding that chitosanase can be produced in a Paecilomyces strain and that it has binding affinity for specific N-acetylated oligosaccharides.
A secure data hiding scheme for binary images
(2002-08-01)
Tseng, YC
;
Chen, YY
;
Pan, HK
;
資訊工程學系
;
Department of Computer Science
This letter presents a novel steganography scheme capable of concealing a piece of critical information in a host message which is a binary image (e.g., a facsimile). A binary matrix and a weight matrix are used as secret keys to protect the hidden information. Given a host image of size m x n, the proposed scheme can conceal as many as [log(2) (mn + 1)] bits of data in the image by changing, at most, two bits in the host image. This scheme can provide a higher security, embed more information, and maintain a higher quality of the host image than available schemes.
An effect scheme for fixed-length tunnel allocation in hierarchical WDM networks
(2005)
Lo, TY
;
Chen, C
;
Chen, YY
;
資訊工程學系
;
Department of Computer Science
In this paper, we investigate the static tunnel allocation problem in multigraularity optical cross-connect (MG-OXC) networks. Our goal is to allocate a set of tunnels that minimize the blocking probability for the dynamic traffic that will follow the prior-known historical traffic matrix. A heuristic Capacity-Balanced Static Tunnel Allocation (CB-STA) has been proposed [1], which always tries to allocate a tunnel from the node with maximal predicted traffic going out to the node with maximal predicted traffic coming in. However, the tunnel length constraint is not carefully considered while selecting node pairs. Thus, this work proposes a heuristic, Weighted Tunnel Allocation (WTA), to improve CB-STA. WTA adds some additional edges with predefined hop length, termed auxiliary links, to the original topology to form an auxiliary graph. Node pair incident to an auxiliary link means that there could be tunnels allocated for it. By routing the historical traffic on the auxiliary graph, preference of tunnel allocation for each node pair incident to the auxiliary link can be estimated. Finally the tunnels will be allocated according to the preference, The simulation results show that WTA outperforms CB-STA in all switching type combinations.
An intelligent radar predictor for high-speed moving-target tracking
(2002)
Chen, YY
;
Young, KY
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Due to rapid increase in missile speed, the air-defense radar system faces severe challenge in tracking these high-speed missiles. During tracking, the radar data are read into the system in a real-time manner sequentially, and thus only few data are available for trajectory estimation in every short time period. Therefore, in this paper, we propose an intelligent radar predictor, including a self-organizing map (SOM), to achieve accurate trajectory estimation under the strict time constraint. By knowing the dynamic model of the moving target, the SOM, an unsupervised neural network, learns to predict the target trajectory using a limited number of data. The performance of the SOM is compared with that of the Kalman filtering. Simulation results based on both the generated and real radar data demonstrate the effectiveness of the proposed intelligent radar predictor.
Anomalous temperature and disorder dependences of electron-phonon scattering rate in impure V1-xAlx alloys
(2004-06-01)
Meikap, AK
;
Chen, YY
;
Lin, JJ
;
電子物理學系
;
物理研究所
Using weak-localization studies, we have measured the electron-phonon scattering time tau(ep) in a series of V1-xAlx alloys having the characteristic of ql<<1, where q is the wave number of the thermal phonons and l is the electron elastic mean free path. We find an anomalous electron-phonon scattering rate obeying a quadratic temperature dependence as well as a linear mean-free-path dependence, i.e., tau(ep)(-1)similar toT(2)l. This result cannot be explained in terms of existing theories for the electron-phonon interaction in impure conductors.
Characteristics of the inter-poly Al(2)O(3) dielectrics on NH(3)-nitrided bottom poly-si for next-generation flash memories
(2005-04-01)
Chen, YY
;
Chien, CH
;
Lou, JC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effects of surface NH(3) nitridation of the bottom poly-Si film, and post-deposition annealing (PDA) temperature, on the electrical properties and reliability characteristics of aluminum oxide (Al(2)O(3)) inter-poly capacitors, were evaluated in this study. The polarity-dependent dielectric properties of Al(2)O(3) inter-poly dielectrics (IPDs) were strongly affected by both surface nitridation and the annealing temperature. For positive gate bias, IPDs with NH(3) surface nitridation significantly suppressed the formation of an additional layer with a lower dielectric constant, during the post-annealing process, and obtained a smoother interface, compared to those without nitridation treatment. Furthermore, the presence of a thin Si-N layer made the PDA more effective in eliminating the traps existing in the as-deposited films, and improved dielectric characteristics, under negative polarity. As a result, the smoother interface and smaller electron trapping rate contributed to the drastically reduced leakage current, enhanced breakdown field, and charge to breakdown (Q(bd)) of the Al(2)O(3) inter-poly capacitors with surface NH(3) nitridation. Moreover, the electrical properties of Al(2)O(3) IPD were heavily dependent upon the PDA temperature. The sample exhibited optimal quality in terms of leakage current, electron trapping rate and Qbd when annealed at 900 degrees C. X-ray photoelectron spectroscopy and Auger electron spectroscopy analyses have shown that this occurrence arises from various compositions, under different annealing conditions and excess oxygen, which can act as an electron trapping center, playing an important role in determining IPD electrical properties.
Characteristics of the inter-poly Al2O3 dielectrics on NH3-nitrided bottom poly-si for next-generation flash memories
(2005-04-01)
Chen, YY
;
Chien, CH
;
Lou, JC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effects of surface NH3 nitridation of the bottom poly-Si film, and post-deposition annealing (PDA) temperature, on the electrical properties and reliability characteristics of aluminum oxide (Al2O3) inter-poly capacitors, were evaluated in this study. The polarity-dependent dielectric properties of Al2O3 inter-poly dielectrics (IPDs) were strongly affected by both surface nitridation and the annealing temperature. For positive gate bias, IPDs with NH3 surface nitridation significantly suppressed the formation of an additional layer with a lower dielectric constant, during the post-annealing process, and obtained a smoother interface, compared to those without nitridation treatment. Furthermore, the presence of a thin Si-N layer made the PDA more effective in eliminating the traps existing in the as-deposited films, and improved dielectric characteristics, under negative polarity. As a result, the smoother interface and smaller electron trapping rate contributed to the drastically reduced leakage current, enhanced breakdown field, and charge to breakdown (Q(bd)) of the Al2O3 inter-poly capacitors with surface NH3 nitridation. Moreover, the electrical properties of Al2O3 IPD were heavily dependent upon the PDA temperature. The sample exhibited optimal quality in terms of leakage current, electron trapping rate and Qbd when annealed at 900 degrees C. X-ray photoelectron spectroscopy and Auger electron spectroscopy analyses have shown that this occurrence arises from various compositions, under different annealing conditions and excess oxygen, which can act as an electron trapping center, playing an important role in determining IPD electrical properties.
Electrooptical properties of GaNAs/GaAs multiple quantum well structures
(2003-07-25)
Lee, JR
;
Chen, YY
;
Lu, CR
;
Lee, WI
;
Lee, SC
The electrooptical properties of the GaNAs/GaAs multiple quantum well structures have been studied using the photoreflectance spectroscopy from 20 K to room temperature. Above the band gap energy of GaAs, Franz-Keldysh oscillations were observed. The period of the Franz-Keldysh oscillations decreased slightly with decreasing temperature, and indicated that the corresponding space charge distribution varied slowly with temperature. The modulated quantum well transition features were observed below the band gap energy of GaAs. A matrix transfer algorithm was used to calculate the quantum well subband energies numerically. The band gap energy and the electron effective mass of the GaNAs/GaAs system were adjusted to obtain the subband energies to best fit the observed quantum well transition energies. (C) 2003 Elsevier Science B.V. All rights reserved.
High quality Al2O3IPD with NH3 surface nitridation
(2003-08-01)
Chen, YY
;
Chien, CH
;
Lou, JC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this letter, the effect of surface NH3 nitridation on the electrical properties and reliability characteristics of aluminum oxide (Al2O3) interpoly capacitors is studied. With NH3 surface nitridation, the formation of an additional layer with lower dielectric constant during post-annealing process can be significantly suppressed, compared to that without nitridation treatment. Furthermore, the presence of a thin Si-N layer can make post-deposition annealing more effective in eliminating traps existing in the as-deposited films. As a result, a smoother interface and smaller electron trapping rate can contribute to the drastically reduced leakage current, enhanced breakdown field and charge to breakdown (Q(bd)) of Al2O3 interpoly capacitors with surface NH3 nitridation.
Luminescent mechanisms of ZnS : Cu : Cl and ZnS : Cu : Al phosphors
(2001-07-23)
Chen, YY
;
Duh, JG
;
Chiou, BS
;
Peng, CG
;
電子工程學系及電子研究所
ZnS:Cu:Cl and ZnS:Cu:Al phosphors are fabricated by a flux fusion method to be used in cathode ray tube (CRT) monitors for green emission. The emission spectra of the phosphors depend on the Cu concentration. A series of luminescence measurements have been conducted, and several models are applied to explain the luminescent phenomenon of these phosphors. It is revealed that ZnS:Cu:Cl and the ZnS:Cu:Al phosphors exhibit green emission yet their luminescence mechanisms are different. The emission spectrum from the as-fabricated green phosphors is not a typical Gaussian distribution. The combination of blue and green band luminescence is attributed to the green-luminescence quenching derived from the interstitial Cu+ ions. (C) 2001 Elsevier Science B.V. All rights reserved.
Photoreflectance characterization of GaNAs/GaAs multiple quantum well structures
(2002)
Lu, CR
;
Lee, JR
;
Chen, YY
;
Lee, WI
;
Lee, SC
We investigate GaNAs/GaAs multiple quantum well structures using the photoreflectance spectroscopy at various temperatures. The modulated optical response consists of quantum well excitonic transitions and band edge transitions that exhibits Franz-Keldysh oscillatory features. The bowing parameter, effective mass, and the band-offset value were adjusted to obtain the subband energies to best fit the observed quantum well transition energies. The period of the Franz-Keldysh oscillations indicates the strength of the internal field.
PUML and PGML: Device-independent UI and logic markup languages on small and mobile appliances
(2005)
Kao, TH
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Chen, YY
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Tsai, TH
;
Chou, HJ
;
Lin, WH
To accomplish developing mobile web applications on variety of mobile execution environments, we propose Pervasive User interface Markup Language (PUML) describing user interfaces for applications on the small devices, and Pervasive loGic Markup Language (PGML) representing the computational logic of the applications. Furthermore, we exploit the XSLT/XPath transformation mechanism to transform documents of PUML/PGML into the target languages, and evaluate them by implementing toolkit and runtime service applications. In Brief, our paper contributes an XML-based application model to assist mobile application developers.
Temperature dependence of magnetic properties in Ni-Mn-Ga shape memory alloys
(2004)
Lee, MD
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Nong, NV
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Thuy, NP
;
Yao, YD
;
Lee, SF
Due to exhibiting giant field-induce strain, the Ni2MnGa shape memory alloys are great interest for both scientific researches and industry applications. The non-stoichiometric Ni50Mn25+xGa25-x alloys with x varied from 1.5, 2.5 to 4 have been fabricated by arc-melting. Martensitic transformation temperature for structure transformation from tetragonal to cubic (T-M) was observed from the magnetization, electrical resistivity and X-ray diffraction studies as functions of temperature below 400 K. We found that T-M increases roughly from 280 K to 310K with increasing x from 1.5 to 4. However, the Curie transition (T-M) is roughly at 380 K for all the samples, it is insensitive to the variation of Mn/Ga ratio. The electrical resistivity data exhibit a deep near T-M and a slope change near T-C. We have experimentally demonstrated that the shape memory effect can be occurred at room temperature with a proper concentration variation of Mn and Ga. (C) 2004 WILEYNCH Verlag GmbH & Co. KGaA, Weinheim.
The effect of substrate surface roughness on the wettability of Sn-Bi solders
(2000-06-01)
Chen, YY
;
Duh, JG
;
Chiou, BS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effect of substrate surface roughness on the wettability of Sn-Bi solders is investigated by the eutectic Sn-Bi alloy on Cu/Al2O3 substrates at 190 degrees C. To engineer the surface with different roughnesses, the Cu-side of the substrates is polished with sandpaper with abrasive number 100, 240, 400, 600, 800, 1200, and 1 mu m alumina powder, respectively. Both dynamic and static contact angles of the solder drops are studied by the real-time image in a dynamic contact angle analyzer system (FTA200). During dynamic wetting, the wetting velocity of the solder drop decreases for the rougher surface. However, the time to reach the static contact angle seems to be identical with different substrate surface roughness. The wetting tip of the solder cap exhibits a waveform on the rough surface, indicating that the liquid drop tends to flow along the valley. As the solder drops reach a static state, the static contact angle increases with the substrate surface roughness. This demonstrates that the wettability of solders degrades as the substrates become rough.
Virtual topology reconfiguration in hierarchical cross-connect WDM networks
(2005)
Yeh, HY
;
Chen, C
;
Chen, YY
;
資訊工程學系
;
Department of Computer Science
Multigranularity optical cross-connects (MG-OXCs) have emerged as the means to save the cost of manufacturing large optical cross-connects (OXCs) used in the IP-over-WDM networks. This paper considers the virtual topology configuration problem in the MG-OXC networks that has not yet been studied. We assume that the future traffic pattern is known a priori and we are to reconfigure the original topology, without dramatically changing the current virtual topology, to the new one that is suitable for the new traffic pattern. We propose our heuristic Preference Based Reconfiguration Algorithm (PBRA) to solve the problem by constructing an auxiliary graph to help determining the addition, deletion, or keeping of the virtual links. Simulation results show that we can change less original virtual topology at the cost of small increase in blocking probability.