Browsing by Author "Pan, JS"

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0.66 mu m InGaP/InGaAlP single quantum well microdisk lasers
(1998-06-01)
Pan, JS
;
Cheng, PH
;
Lee, TD
;
Lai, YC
;
Tai, KC
Visible emitting microdisk lasers with single InGaP/InGaAlP quantum well were demonstrated for the first time. Large spontaneous emission factors beta of 0.12 and 0.08 were observed for 5 and 10 mu m diameter disks, respectively.
A tabu search based maximum descent algorithm for VQ codebook design
(2001-09-01)
Huang, HC
;
Chu, SC
;
Pan, JS
;
Lu, ZM
;
電子工程學系及電子研究所
A maximum descent (MD) method has been proposed for vector quantization (VQ) codebook design. Compared with the traditional generalized Lloyd algorithm (GLA), the MD algorithm achieves better codebook performance with far less computation time. However, searching for the optimal partitioning hyperplane of a multidimensional cluster is a difficult problem in the MD algorithm. Three partition techniques have been proposed for the MD method in the literature. In this paper, a new partition technique based on the tabu search (TS) approach is presented for the MD algorithm. Experimental results show that the tabu search based MD algorithm can produce a better codebook than can the conventional MD algorithms.
A VQ-based robust multi-watermarking algorithm
(2002-07-01)
Huang, HC
;
Wang, FH
;
Pan, JS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
New methods for digital image watermarking based on the characteristics of vector quantization (VQ) are proposed. In contrast with conventional watermark embedding algorithms to embed only one watermark at a time into the original source; we present one algorithm to embed multiple watermarks for copyright protection. The embedding and extraction processes are efficient for implementing with conventional VQ techniques; and they can be accomplished in parallel to shorten the processing time. After embedding, embedder would output one watermarked reconstruction image and several secret keys associated with the embedded watermarks. These secret keys are then registered to the third party to preserve the ownership of the original source in order to prevent the attackers from inserting counterfeit watermarks. Simulation results show that under no attacks, the embedded watermarks could be perfectly extracted. If there are some intentional attacks in our simulation, all the watermarks could survive to protect the copyrights. Therefore, we are able to claim the robustness, usefulness, and ease of implementation of our algorithm.
An adaptive and robust watermarking method based on VQ
(2002-04-01)
Huang, HC
;
Wang, FS
;
Pan, JS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
An adaptive and robust watermarking algorithm based on vector quantization (VQ) is presented in this paper. A binary watermark is adaptively embedded with the characteristics of the original source in the VQ domain, then the watermarked image along with a secret key are transmitted to the receiver for protecting the ownership. In extracting the watermark, we make use of the pre-registered secret key in addition to the watermarked image to examine whether the watermark could survive the intentional attacks or not. We performed a variety of attacks on the watermarked image, including the destruction attacks and the synchronization attacks, to show the robustness and effectiveness of the proposed algorithm. After watermark extraction, we acquired the extracted watermark that is highly similar to the embedded one; in addition, the information conveyed therein is easily recognizable. Hence, the proposed algorithm is not only robust bust also useful for protecting the ownership of digital media.
An embedding algorithm for multiple watermarks
(2003-03-01)
Shieh, CS
;
Huang, HC
;
Wang, FH
;
Pan, JS
;
電子工程學系及電子研究所
A new algorithm for embedding several watermarks into the same original source is proposed in this paper. Instead of conventional watermark embedding algorithms that embed one watermark in one specific domain, we propose algorithms for embedding multiple watermarks into different compression domains to protect the ownership of the original images. The proposed schemes for embedding and extraction in different domains vary from the existing methods reported in the literature. Simulation results show their robustness for surviving intentional attacks and, hence, their effectiveness in protecting copyrights. They are also easy to implement.
Efficient and robust watermarking algorithm with vector quantisation
(2001-06-21)
Huang, HC
;
Wang, FH
;
Pan, JS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A new method for watermarking based on Vector quantisation is proposed. It is efficient for implementation with conventional techniques, and simulation results show its robustness under a variety of attacks. Tt also represents superiority over eng algorithms.
Far-field emission narrowing effect of microdisk lasers
(1998-05-04)
Lee, TD
;
Cheng, PH
;
Pan, JS
;
Tsai, RS
;
Lai, Y
Far-field intensity distribution of semiconductor microdisk lasers is experimentally measured and the emission angle is found to be much smaller than that of a planar source with the same near-held width. In fact the emission angle is determined mainly by the disk radius instead of the disk thickness. A scalar diffraction theory in the cylindrical coordinate is developed to explain such an emission-angle-narrowing phenomenon and numerical calculation based on a vectorial diffraction theory is carried out to explain the measured polarization state. (C) 1998 American Institute of Physics.
Genetic watermaking based on transform-domain techniques
(2004-03-01)
Shieh, CS
;
Huang, HC
;
Wang, FH
;
Pan, JS
;
電子工程學系及電子研究所
An innovative watermarking scheme based on genetic algorithms (GA) in the transform domain is proposed. It is robust against watermarking attacks, which are commonly employed in the literature. In addition, the watermarked image quality is also considered. In this paper, we employ GA for optimizing both the fundamentally conflicting requirements. Watermarking with GA is easy for implementation. We also examine the effectiveness of our scheme by checking the fitness function in GA, which includes both factors related to robustness and invisibility. Simulation results also show both the robustness under attacks, and the improvement in watermarked image quality with GA. (C) 2003 Pattern Recognition Society. Published by Elsevier Ltd. All rights reserved.
Mode emission characteristics of semiconductor microdisc and microring lasers
(1996-10-01)
Lee, TD
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Cheng, PH
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Pan, JS
;
Tai, K
;
Lai, Y
We fabricate both microdisc and microring InGaAsP-InGaAs quantum well semiconductor lasers using an etching-and-bonding technique. Their emission properties are studied by optical pumping at 77 K. Single mode lasing is achieved for discs with a diameter of 5 mu m. Multimode emission is observed for rings with larger diameters. Both fundamental and higher order lasing modes are observed and are found to exhibit interesting emission characteristics.
Mode emission properties of semiconductor micro-disk and micro-ring lasers
(1999)
Lee, TD
;
Cheng, PH
;
Pan, JS
;
Tai, K
;
Lai, Y
We have successfully fabricated optically pumped semiconductor micro-disk and micro-ring lasers under the InGaAsP/InGaAs system at the 1.5 mu m wavelength and under the InGaP/InGaAlP system at the 0.66 mu m wavelength. The spontaneous emission factor beta of these micro-lasers is estimated directly from their output-pump curves and its dependence on the cavity volume is verified. Interesting phenomena regarding the far-field emission pattern and lasing linewidth of these micro-cavity lasers are experimentally observed and theoretically studied.
Oxide-confined vertical-cavity surface-emitting lasers pumped Nd : YVO4 microchip lasers
(2002-03-01)
Lan, YP
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Chen, YF
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Huang, KF
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Lai, HC
;
Pan, JS
In this letter, we demonstrate an experimental study of using a large area oxide-confined vertical-cavity surface-emitting laser (VCSEL) to pump a Nd:YVO4 microchip laser. The maximum output power of 1.2 mW in TEM00 mode is obtained with a pump power of 8.2 mW. Experimental results show that the complex transverse modal behavior of VCSELs in the higher injection current may cause an impediment of power scaling.
Progressive watermarking techniques with genetic algorithms
(2003)
Huang, HC
;
Pan, JS
;
Shieh, CS
;
Wang, FH
;
電子工程學系及電子研究所
An innovative watermarking scheme based on progressive transmission with genetic algorithms (GA) is proposed. We implement the watermarking embedding and extraction system in the discrete cosine transform (DCT) domain, and apply the JPEG spectral selection mode for progressive transmission. By employing GA with a proper fitness function into the watermarking system, both the watermark imperceptibility and watermark robustness requirements are considered and optimized. In addition, the embedded watermark can be partly extracted in the receiver side even when the watermarked image is being transmitted. Simulation results show both the robustness and the effectiveness of progressive transmission under different attacking schemes and different bandwidth variations.
Robust image watermarking based on multiple description vector quantisation
(2004-10-28)
Pan, JS
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Hsin, YC
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Huang, HC
;
Huang, KC
;
電子工程學系及電子研究所
An innovative scheme for watermarking based on vector quantisation for transmitting over noisy channels is proposed. By modifying multiple description vector quantisation for watermark embedding and extraction, simulation results not only demonstrate effective transmission of the watermarked image, but reveal the robustness of the extracted watermark.
Robust VQ-Based digital watermarking for the memoryless binary symmetric channel
(2004-07-01)
Pan, JS
;
Sung, MT
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Huang, HC
;
Liao, BY
;
電子工程學系及電子研究所
A new scheme for watermarking based on vector quantization (VQ) over a binary symmetric channel is proposed. By optimizing VQ indices with genetic algorithm, simulation results not only demonstrate effective transmission of watermarked image, but also reveal the robustness of the extracted watermark.
Spontaneous emission factor versus cavity volume in low dimensional photonic micro-cavities
(1997-10-15)
Cheng, PH
;
Lee, TD
;
Pan, JS
;
Lai, Y
;
Tai, K
Micro-ring and micro-disk lasers an formed at the same time by transferring the epitaxial layers of 1.55 mu m wavelength InGaAs/ZnGaAsP quantum wells on a glass substrate. The spontaneous emission factor beta in such micro-rings of 5 mu m diameter and 0.2 x 0.5 mu m(2) cross-section is 0.16, which is four times that in micro-disk lasers of the same diameter. The result confirms for the first time that the micro-ring being a lower dimensional photonic system has a larger beta. Study of beta versus the cavity size indicates that the observed spontaneous emission factor is approximately the reciprocal of the normalized cavity volume, when normalization is done to the cubic of the wavelength in the medium. (C) 1997 Elsevier Science B.V.
Spontaneous emission factor versus cavity volume in low dimensional photonic micro-cavities
(1997-10-15)
Cheng, PH
;
Lee, TD
;
Pan, JS
;
Lai, Y
;
Tai, K
Micro-ring and micro-disk lasers an formed at the same time by transferring the epitaxial layers of 1.55 mu m wavelength InGaAs/ZnGaAsP quantum wells on a glass substrate. The spontaneous emission factor beta in such micro-rings of 5 mu m diameter and 0.2 x 0.5 mu m(2) cross-section is 0.16, which is four times that in micro-disk lasers of the same diameter. The result confirms for the first time that the micro-ring being a lower dimensional photonic system has a larger beta. Study of beta versus the cavity size indicates that the observed spontaneous emission factor is approximately the reciprocal of the normalized cavity volume, when normalization is done to the cubic of the wavelength in the medium. (C) 1997 Elsevier Science B.V.
The application of tabu search approach to energy allocation and index assignment for VQ-based binary phase shift keying
(2002-01-01)
Shieh, CS
;
Huang, HC
;
Pan, JS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Allocating the energy to the transmitted bits according to their error sensitivities has been shown to significantly overcome the channel errors compared with the codevector index assignment algorithms for vector quantization. In this paper, we combine the tabu energy allocation algorithm with the 'tabu index assignment algorithm' for VQ-based signal compression to reduce the channel distortion caused by the channel decoding error. Experimental results demonstrate that the tabu energy allocation algorithm is superior to the conventional energy allocation algorithm by evaluating the performances under different channel distortion levels. Moreover, the combination of tabu energy allocation and index assignment has better output to compare with tabu index assignment algorithm, conventional energy allocation algorithm and tabu energy allocation algorithm for VQ-based BPSK.
The molecular mechanism of actinomycin D in preventing neointimal formation in rat carotid arteries after balloon injury
(2005-05-01)
Wu, CH
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Pan, JS
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Chang, WC
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Hung, JS
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Mao, SJT
The pathological mechanism of restenosis is primarily attributed to excessive proliferation of vascular smooth muscle cells (SMC). Actinomycin D has been regarded as a potential candidate to prevent balloon injury-induced neointimal formation. To explore its molecular mechanism in regulating cell proliferation, we first showed that actinomycin D markedly reduced the SMC proliferation via the inhibition of BrdU incorporation at 80 nM. This was further supported by the G1-phase arrest using a flowcytometric analysis. Actinomycin D was extremely potent with an inhibitory concentration IC50 at 0.4 nM, whereas the lethal dose LD50 was at 260 mu M. In an in vivo study, the pluronic gel containing 80 nM and 80 lMactinomycin D was applied topically to surround the rat carotid adventitia; the thickness of neointima was substantially reduced (45 and 55%, respectively). The protein expression levels of proliferating cell nuclear antigen ( PCNA), focal adhesion kinase (FAK), and Raf were all suppressed by actinomycin D. Extracellular signal-regulated kinases (Erk) involved in cell-cycle arrest were found to increase by actinomycin D. These observations provide a detailed mechanism of actinomycin D in preventing cell proliferation thus as a potential intervention for restenosis.
Vector quantization based on genetic simulated annealing
(2001-07-01)
Huang, HC
;
Pan, JS
;
Lu, ZM
;
Sun, SH
;
Hang, HM
Genetic algorithm (GA) has been successfully applied to codebook design for vector quantization (VQ). However, most conventional GA-based codebook design methods need long runtime because candidate solutions must be fine tuned by LBG. In this paper, a partition-based GA is applied to codebook design, which is referred to as genetic vector quantization (GVQ). In addition, simulated annealing (SA) algorithm is also used in GVQ to get more promising results and the corresponding method is referred to as GSAVQ. Both GVQ and GSAVQ use the linear scaling technique during the calculation of objective functions and use special crossover and mutation operations in order to obtain better codebooks in much shorter CPU time. Experimental results show that both of them save more than 71-87% CPU time compared to LEG. For different codebook sizes, GVQ outperforms LEG by 1.1-2.1 dB in PSNR, and GSAVQ outperforms LBG by 1.2-2.2 dB in PSNR. In addition, GVQ and GSAVQ need a little longer CPU time than, the maximum decent (MD) algorithm, but they outperform MD by 0.2-0.5 dB in PSNR. (C) 2001 Elsevier Science B.V. All rights reserved.
VQ-based gray watermark hiding scheme and genetic index assignment
(2004)
Wang, FH
;
Pan, JS
;
Jain, L
;
Huang, HC
;
電子工程學系及電子研究所
A vector quantisation (VQ) based watermarking scheme for hiding the gray watermark is presented. It expands the watermark size, and employs VQ index assignment procedure with genetic algorithm, called genetic index assignment (GIA), for watermarking. The gray watermark is coded by VQ and obtained indices are translated into a binary bitstrearn with a much smaller size. We partition the codebook into two sub-codebooks, and use either one of them based on the value of the bit for embedding. Next, GIA is employed to find better imperceptibility of watermarked image. Experimental results show that the proposed method possesses advantages over other related methods in literature.