Browsing by Author "Chuang, TJ"

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A new algorithm for lossless still image compression
(1998-09-01)
Chuang, TJ
;
Lin, JC
;
資訊工程學系
;
Department of Computer Science
This paper presents a spatial domain method for lossless still image compression using a new scheme: base switching (BS). The given image is partitioned into non-overlapping fixed-size subimages. Different subimages then get different compression ratios according to the base values of the subimages. In order to increase the compression ratio, a hierarchical technique is also used. It is found that the compression ratio of the proposed algorithm can compete with that of the VBSS and the international standard algorithms known as JBIG and Lossless JPEG. In addition, when the BS method is compared with the S + P method, which is an excellent frequency domain method that used EZW, although S + P method gains about 9% increase in the compression ratio, its encoding time (excluding I/O) is about three times longer than ours. The math theory needed to build up the proposed compression scheme is also provided. (C) 1998 Published by Elsevier Science Ltd on behalf of the Pattern Recognition Society. All rights reserved.
Molecular conformation and nanomechanics of self-assembled alkylsiloxane monolayers
(1997-01-08)
Huang, JY
;
Song, KJ
;
Lagoutchev, A
;
Yang, PK
;
Chuang, TJ
We have studied the chain conformation and nanomechanical properties of pure alkylsiloxane monolayers and the mixed films with fluorine-containing species using scanning force microscopy (SFM) and infrared-visible sum-frequency generation spectroscopy (IV-SFG). Our IV-SFG spectra yield information about the chain ordering and surface density of specific species in the pure and mixed monolayers. A film formation process involving preferential adsorption of the fluorinated species from solution was observed. On the basis of the SFM measurements, the stiffness of alkylsiloxane monolayers under load was found to increase with the chain length, changes of chain conformation, and alkyl chain fluorination.
Molecular conformation and nanomechanics of self-assembled alkylsiloxane monolayers
(1997-01-08)
Huang, JY
;
Song, KJ
;
Lagoutchev, A
;
Yang, PK
;
Chuang, TJ
We have studied the chain conformation and nanomechanical properties of pure alkylsiloxane monolayers and the mixed films with fluorine-containing species using scanning force microscopy (SFM) and infrared-visible sum-frequency generation spectroscopy (IV-SFG). Our IV-SFG spectra yield information about the chain ordering and surface density of specific species in the pure and mixed monolayers. A film formation process involving preferential adsorption of the fluorinated species from solution was observed. On the basis of the SFM measurements, the stiffness of alkylsiloxane monolayers under load was found to increase with the chain length, changes of chain conformation, and alkyl chain fluorination.
New approach to image encryption
(1998-04-01)
Chuang, TJ
;
Lin, JC
;
資訊工程學系
;
Department of Computer Science
A new cryptographic method for encrypting still images is proposed. This method is designed on the basis of the base-switching lossless image compression algorithm. The method therefore simultaneously possesses both image encryption and lossless compression abilities. A given image is first partitioned into nonoverlapping fixed-size subimages, and each subimage will then have its own base value. These subimages are then encoded and encrypted one by one according to the base values. By choosing the function to encrypt the base value, there are (128!)(t) [or (128!)(3t)] possible ways to encrypt a gray-scaled (color) image if t layers are used in the encryption system. The theoretical analysis needed to support the proposed encryption method is provided, and the experimental results are also presented. (C) 1998 SPIE and IS&T. [S1017-9909(98)01202-1].
Self-assembly of alkylsiloxane monolayers on fused silica studied by XPS and sum frequency generation spectroscopy
(1998-01-15)
Lagutchev, AS
;
Song, KJ
;
Huang, JY
;
Yang, PK
;
Chuang, TJ
Infrared-visible sum frequency generation (SFG) vibrational spectroscopy in the C-H stretching region was used to study a set of self-assembled monolayers, formed from octyltrichlorosilane [CH3(CH2)(7)SiCl3], its partially fluorinated analog, (tridecafluoro-1,1,2,2-tetrahydrooctyl)-1-trichlorosilane [CF3-(CF2)(5)(CH2)(2)SiCl3] and their mixtures. SFG measurements were complemented with transmission-absorption FTIR spectroscopy and X-ray photoemission spectroscopy. Simultaneous self-assembly of both chlorosilanes results in preferential deposition of the fluorinated compound. The major reason for this behavior is the alkyl chain fluorination. There is a strong spectroscopic evidence of close coadsorption of fluorinated and non-fluorinated molecules in mixed monolayers. It follows that the species in self-assembled monolayers of binary composition do not segregate into different phases as it is observed for similar Langmuir-Blodgett films. Distinct differences found in SFG spectra of fluorinated and non-fluorinated samples indicate that SFG spectroscopy is much more sensitive than FTIR in detection of symmetry distortions in the alkyl chain of the amphiphiles. Both SFG and FTIR spectroscopic data show the presence of hydrocarbon residue in fluorinated and mixed films that is very likely due to hexadecane used as a solvent during monolayer deposition. (C) 1998 Elsevier Science B.V.
Sum-frequency vibrational spectroscopic study of mixed alkylsiloxane monolayers self-assembled on fused silica surface
(1997-10-01)
Lagutchev, AS
;
Song, KJ
;
Huang, JY
;
Yang, PK
;
Chuang, TJ
Self-assembled monolayers of fluorinated and non-fluorinated alkylsiloxanes were prepared on fused silica substrates and studied by both conventional IR and nonlinear sum-frequency vibrational spectroscopy complemented with XPS. Simultaneous self-assembly of the two alkylsiloxanes results in preferential adsorption of the fluorinated compound and formation of the mixed monolayer. Different species are found to be closely coadsorbed in the mixed monolayers which distinguishes self-assembly from Langmuir-Blodgett deposition where the similar species tend to separate into different phases. Nonlinear sum-frequency spectroscopy of C-H stretching region detects symmetry perturbations of the alkyl chain induced by trans-cis defects and partial fluorination and clearly distinguishes between them. All three characterization methods consistently indicate the presence of a hydrocarbon residue in all deposited monolayers, which is ascribed to the hexadecane used as a solvent during the self-assembly process. (C) 1997 Elsevier Science S.A.