Showing papers by "Kwangwoon University published in 1999"
TL;DR: A new optical image encryption technique based on exclusive-OR (XOR) operations for a security system that controls the entrance of authorized persons is proposed and some simulation results that verify the proposed method are presented.
Abstract: Kwangwoon UniversityDepartment of Electronic Engineering447-1, Wolge-Dong, Nowon-GuSeoul 139-701South KoreaAbstract. We propose a new optical image encryption technique basedon exclusive-OR (XOR) operations for a security system that controls theentrance of authorized persons. The basic idea is that we convert agray-level image to eight bit planes for image encryption. We use theXOR operation that is commonly used such as the well-known encryp-tion method. The input image is encrypted by performing optical XORoperations with the key bit stream that are generated by digital encryp-tion algorithms. The gray level input image is converted to eight bitplanes, which are represented on a liquid crystal device (LCD). The keydata represented on different LCDs is reproduced to eight bit planes by alenslet array. The optical XOR operations between the key data and thebit planes are performed by the polarization encoding method. The re-sults of XOR operations, which are detected by a CCD camera, areconverted to an encrypted gray-level image and the image is used as aninput to the binary phase extraction joint transform correlator (BPEJTC)for comparison with reference images. We present some simulation re-sults that verify the proposed method.
157 citations
TL;DR: In this article, a wavelet-Galerkin scheme based on the time-dependent Maxwell's equations is presented, and the storage effectiveness, execution time reduction, and accuracy of this scheme are demonstrated by calculating the resonant frequencies of the homogeneous and inhomogeneous cavities.
Abstract: A wavelet-Galerkin scheme based on the time-dependent Maxwell's equations is presented. Daubechies' wavelet with two vanishing wavelet moments is expanded for basis function in spatial domain, and Yee's leap-frog approach is applied. The shifted interpolation property of Daubechies' wavelet family leads to the simplified formulations for inhomogeneous media without the additional matrices for the integral or material operator. The storage effectiveness, execution time reduction, and accuracy of this scheme are demonstrated by calculating the resonant frequencies of the homogeneous and inhomogeneous cavities.
88 citations
TL;DR: Using a gain-saturated semiconductor optical amplifier, a large increase has been achieved in the signal-to-noise ratio that is much better than previous results to the knowledge as mentioned in this paper.
Abstract: Using a gain-saturated semiconductor optical amplifier, we have suppressed the intensity noise in spectrum-sliced incoherent light communication systems. A large increase has been achieved in the signal-to-noise ratio that is much better than previous results to our knowledge. Using this technique, we have transmitted a 0.36-nm bandwidth 2.5-Gb/s incoherent light signal over 20 km of conventional single-mode fiber without any dispersion compensation. The transmission penalty was 1.5 dB and the error floor level was less than 10/sup -10/.
57 citations
TL;DR: A local shape-adaptive template filtering is proposed for the enhancement of the signal-to-noise ratio (SNR) without the loss of resolution in magnetic resonance (MR) imaging, where multiple templates are defined in the proposed algorithm.
Abstract: A local shape-adaptive template filtering is proposed for the enhancement of the signal-to-noise ratio (SNR) without the loss of resolution in magnetic resonance (MR) imaging. Unlike conventional filtering, where the template shape and coefficients are fixed, multiple templates are defined in the proposed algorithm. An optimal template is selected and optimal filtering, based on the template, is applied on a pixel-by-pixel basis. Using the proposed process, edge blurring is minimized and SNR enhancement is maximized by selecting the optimally matched template. Compared to existing two-dimensional (2-D) adaptive linear least square error (LLSE) filters or direction-adaptive recursive filters, the proposed adaptive template filter provides higher SNR and sharper edges for both MR and artificial resolution phantom images.
41 citations
TL;DR: In this paper, a one-dimensional numerical model is proposed to predict soil deformation and unsaturated transient water flow in swelling soil on a laboratory scale using a Lagrangian description (LD).
40 citations
TL;DR: In this article, the hydroxyl-terminated poly(dimethylsiloxane) (PDMS) was used to measure swelling equilibria for solvent(1)/PDMS(2) and solvent( 1)/solvent(2)/ PDMS(3) systems.
Abstract: The hydroxyl-terminated poly(dimethylsiloxane) (PDMS) was used to measure swelling equilibria for solvent(1)/PDMS(2) and solvent(1)/solvent(2)/PDMS(3) systems. PDMSs were vulcanized to prepare four compounds (PDMS-35, PDMS-40, PDMS-45, and PDMS-50) having different hardness. The swelling ratios of the binary and the ternary systems were measured and supplied at various temperatures from 303.15 K to 318.15 K. They were used to describe the swelling abilities of the cross-linked PDMS absorbing mixed solvents into the polymers. A Flory−Huggins model was combined with three different expressions to describe swelling equilibria of the binary and the ternary systems. The experimental swelling equilibria data were correlated with the models to estimate the Flory−Huggins (FH) interaction energy parameters and the average molecular weights of chains between the cross-linked PDMS. The swelling behaviors of the cross-linked PDMSs were described by the FH interaction energy parameters.
37 citations
TL;DR: In this paper, three experiments were conducted to examine whether the interestingness of a story would be influenced by the degree of causal bridging inferences a reader generates during reading, and it was found that the implicit versions were rated as more interesting than the explicit versions.
Abstract: Three experiments were conducted to examine whether the interestingness of a story would be influenced by the degree of causal bridging inferences a reader generates during reading. Implicit and explicit versions of the same story were used as experimental materials because it was assumed that the implicit versions lead the reader to generate causal bridging inferences. In Expt 1, it was found that the implicit versions were rated as more interesting than the explicit versions. When Rapid Serial Visual Presentation (RSVP) rate of less than 400 milliseconds was used to prevent inference generation in Expt 2, there was no difference in interestingness ratings between the implicit and explicit versions. However, when the RSVP rate was increased to more than 400 milliseconds in Expt 3, implicit versions produced greater interest than explicit versions. The results of three experiments suggest that the implicit versions are no more interesting than the explicit versions unless the readers generate causal bridging inferences. It is concluded that the interestingness of a story is affected by inference generation. A hypothetical model of the occurrence of the cognitive interest is also discussed.
36 citations
TL;DR: In this paper, a single rectangular TE/sub 10/ feed four-slot coaxial coupler is designed and built for excitation of a TE/ sub 011/ cylindrical cavity mode for use in high-power millimeter-wavelength gyroklystron amplifiers.
Abstract: A single rectangular TE/sub 10/ feed four-slot coaxial coupler is designed and built for excitation of a TE/sub 011/ cylindrical cavity mode for use in high-power millimeter-wavelength gyroklystron amplifiers. A high degree of mode purity is obtained and matching of the cavity to the input line is studied. A model based on the mode-matching technique and dipole radiators has been formulated to predict operation of this coupler. The resulting numerical code is capable of finding resonant frequency and cavity bandwidth in a small fraction of the time taken by more general finite-difference/finite-element design tools. The model can be extended to self-consistently include an electron beam, and the model is compared to a coupler design based on Hewlett-Packard's High-Frequency Structure Simulator code. The coupler has been successfully used in a high-power gyroklystron-amplifier experiment.
33 citations
13 Jun 1999
TL;DR: In this paper, the HP EEsof Libra ver. 6.1 has been used for the nonlinear design of the K-band hairpin resonator oscillators and the output power of 0.83 dBm and 1.67 dBm, and phase noise of -86 dBc/Hz and -90 dBc /Hz at the offset frequency of 100 kHz are obtained, respectively.
Abstract: K-band hair-pin resonator oscillators using a frequency doubler and the push-push method are presented in this paper. An HP EEsof Libra ver. 6.1 has been used for the nonlinear design of the oscillators. For the oscillators using the frequency doubler and the push-push method, the output power of 0.83 dBm and -1.67 dBm, and phase noise of -86 dBc/Hz and -90 dBc/Hz at the offset frequency of 100 kHz are obtained, respectively.
32 citations
TL;DR: A simple method of enzyme immobilization was investigated which is useful for fabrication of enzyme sensors based on polymeric ion-selective membranes and was applied to the fabrication of a potentiometric butyrylcholinesterase-based biosensor for the determination of organophosphorus pesticides.
30 citations
TL;DR: Two different types of one-component room temperature vulcanized (RTV) silicone rubbers (Dow Corning 3140 and 730 RTV) are further examined as alternatives to PVC for formulating ion-selective membranes as discussed by the authors.
TL;DR: In this article, the solid solubility of the SrAl 2 O 4 -CaAl 2O 4 system was investigated using both XRD patterns and cathodoluminescence from Eu 2+ in the host lattices.
TL;DR: In this article, two cascaded semiconductor optical amplifiers are used to suppress the intensity noise of a spectrum-sliced incoherent channel with a bit rate as high as 10 Gbit/s for 2.6 nm channel bandwidth.
Abstract: Two cascaded semiconductor optical amplifiers are used to suppress the intensity noise of a spectrum-sliced incoherent channel with a bit rate as high as 10 Gbit/s for 2.6 nm channel bandwidth. The incoherent channel is transmitted over 100 km of dispersion-shifted fibre with a negative transmission penalty caused by intra-channel four-wave mixing.
TL;DR: In this paper, carbon and hydrogen free tetranitratotitanium was synthesized, which is believed to thermally decomposed primarily as: Ti(NO3)4→TiO2+4NO2+O2.
Abstract: Carbon and hydrogen free tetranitratotitanium was synthesized, which is believed to thermally decomposed primarily as: Ti(NO3)4→TiO2+4NO2+O2. The by-products of the thermal decomposition of tetranitratotitanium, which include NO2 and O2, may possibly provide a robust ultrathin tunnel interfacial layer. Due to the hydrogen free nature of thermolysis, N2O may form an oxynitride layer which has been shown to produce thermal oxynitrides with higher quality than NH3-based nitride oxides. Unlike titanium tetrakis isopropoxide (TTIP) deposited films, the interface state density more closely follows the “U” shape characteristic of conventional thermal SiO2/Si interfaces. The integrated interface state density is considerably less for the film annealed at higher temperature, which should produce considerably higher inversion layer mobilities. This improvement of the interface, compared to TTIP deposited films, is believed to be due to the elimination of water vapor from the deposition ambient.
TL;DR: An algorithm suitable for general chemical process optimization problems is proposed in this paper, which is based on a feasible point strategy and combination of a stochastic global algorithm and a deterministic local algorithm.
TL;DR: In this article, three types of hydrophilic polyurethane (HPU) coated Ag/AgCl electrodes of the second kind have been examined, i.e., 42%, 100% and 206% water uptake.
Abstract: Potentiometric properties of hydrophilic polyurethane (HPU) coated Ag/AgCl electrodes of the second kind have been examined. Three types of HPUs which have 42% (HPU-A), 100% (HPU-B), and 206% (HPU-C) of water uptake have been used as coating membranes for Ag/AgCl electrodes. Both HPU coated and bare Ag/AgCl electrodes exhibited virtually the same potentiometric response to chloride. On the other hand, all the electrodes exhibited a three step response to bromide; fast initial response to bromide, followed by gradual potential changes (from –2 to –25 mV/min), and an abrupt potential drop (between about –60 and –80 mV) after some period of time. Fitting the potentiometric response curves to the diffusion model proposed initially by Hulanicki and Lewenstam, and modified later by Morf, it was possible to estimate the relative permeability of HPU membranes: the concentration of bromide that reached the surface of AgCl layer from the bulk solution was reduced by a factor of 1/20 with HPU-A, 1/12 with HPU-B and 1/3 with HPU-C membrane. The ratio of peak currents measured at the HPU coated Pt electrode and that at the bare Pt electrode for various neutral and anionic species indicated that the HPU membranes effectively discriminate the passage of those molecules by their size (e.g., Mw < 400 for neutral and Mw < 200 for anionic molecules). As the HPU membranes substantially reduce the diffusion of larger anions than chloride, e.g., bromide and thiocyanate, the HPU modified Ag/AgCl electrodes accurately determine the chloride level in clinical samples even in the presence of those interfering anions. Since the HPU membrane also effectively prevent the surface fouling of the electrode from protein adsorption, the HPU coated Ag/AgCl electrode was successfully employed to measure the chloride in serum or whole blood.
TL;DR: In this paper, a mode-locked sampled-grating distributed-Bragg-reflector (SGDBR) laser diode was proposed for generating a train of light pulses at terahertz repetition rates.
Abstract: A mode-locked sampled-grating distributed-Bragg-reflector (SGDBR) laser diode for generating a train of light pulses at terahertz repetition rates is proposed with a numerical analysis based on a time-domain large-signal model. The device consists of three parts: the saturable absorber section which serves as a mode-locker, the gain section as an amplifier, and the SGDBR as a spectrum filter. It is predicted that spectrum filtering of the SGDBR along with passive mode locking due to the saturable absorber is effective in generating a train of transform-limited mode-locked pulses at a high repetition rate.
TL;DR: In this article, PZT(40/60)/PZT60/40) heterolayered thin films were fabricated by spin-coating method on the Pt/Ti/SiO2/Si substrate alternately using PZTs 40/60 and PZt 60/40 alkoxide solutions.
TL;DR: The controllability and the observability of continuous linear time-varying systems with norm-bounded parameter perturbations are analyzed and the sufficient conditions which ensure the controllable of the perturbed system are presented by using the derived state transition matrix relationship between the nominal system and the pert disturbed system.
Abstract: The controllability and the observability of continuous linear time-varying systems with norm-bounded parameter perturbations are analyzed. The sufficient conditions which ensure the controllability of the perturbed system are presented by using the derived state transition matrix relationship between the nominal system and the perturbed system. The proposed sufficient conditions allow the evaluation of controllability under the norm-bounded parameter perturbations. The robustness of the observability is also studied for continuous linear time varying systems with norm-bounded parameter perturbations, and the corresponding sufficient conditions are provided.
TL;DR: In this paper, annealed TiN thin films were grown on stainless steel substrates by using the reactive radiofrequency magnetron-sputtering technique at relatively low temperature (∼200°C) using Ti and N2.
24 Oct 1999
TL;DR: The postprocessing method to reduce the blocking artifact in low-bit-rate coded JPEG images, which is based on minimum block-boundary-discontinuity criterion, can provide better visual quality as well as PSNR than any other method.
Abstract: We proposed the post-processing method to reduce the blocking artifact in low-bit-rate coded JPEG images, which is based on minimum block-boundary-discontinuity criterion. We analyzed the statistical property of block boundary pixel difference, classified all blocks into one of two types using OSLD (overlapped sub-laplacian distribution), and compensated the quantization error depending on the type of block, adaptively. Our postprocessing method can provide better visual quality as well as PSNR than any other method.
TL;DR: The authors transmitted 16/spl times/10 Gbit/s wavelength division multiplexed signals over 240 km of dispersion-shifted fibre using periodic-unequally-spaced-channel allocation, with far greater channel number scalability than USCA.
Abstract: The authors transmitted 16/spl times/10 Gbit/s wavelength division multiplexed signals over 240 km of dispersion-shifted fibre using periodic-unequally-spaced-channel allocation. A similar power margin to that obtained using unequally-spaced-channel allocation (USCA) was obtained, with far greater channel number scalability than USCA.
TL;DR: In this paper, the critical streamwise position to mark the onset of stationary longitudinal vortex rolls was predicted as a function of the Prandtl number, and a new correlation of transport properties on mixed convection was derived.
TL;DR: In this article, a naturally parallelizable numerical method is introduced and analyzed for parabolic partial differential equations, instead of solving the problem in the space-time formulation, they propose to solve it in the Space-frequency formulation.
TL;DR: In this article, the effects of polymerization temperature and initiator concentration on polymerization behavior and molecular structures of polyvinyl pivalate (PVPi) and corresponding poly(vinyl alcohol) (PVA) microfibrillar fiber obtained by saponification in KOH/methanol/water were investigated.
Abstract: Vinyl pivalate (VPi) was bulk-polymerized at 30, 40, and 50°C using a low temperature initiator, i. e. 2,2′-azobis(2,4-dimethylvaleronitrile) (ADMVN). The effects of polymerization temperature and initiator concentration were investigated in terms of polymerization behavior and molecular structures of poly(vinyl pivalate) (PVPi) and corresponding poly(vinyl alcohol) (PVA) microfibrillar fiber obtained by saponification in KOH/methanol/water. Low polymerization temperature using ADMVN proved to be successful in obtaining PVA of syndiotacticity-rich high molecular weight. PVPi had a number-average degree of polymerization (Pn) of 27 100–35 900, and a degree of branching for pivaloyl group of 0.8–1.0 at 30°C, 1.0–1.3 at 40°C, and 1.4–1.7 at 50°C at conversions below 40%. Saponification of PVPi yielded PVA having a Pn of 10 400–16 500, and syndiotactic diad (S-diad) content of 58.8–61.5%. It was found that all PVA specimens represented microfibrillar morphologies, with high crystallinity and orientation. The S-diad content and crystal melting temperature were higher with PVA prepared from PVPi polymerized at lower temperatures.
Vinylpivalat (VPi) wurde bei 30, 40 und 50°C mit dem Niedertemperaturinitiator 2,2′-Azobis(2,4-dimethylvaleronitril) (ADMVN) polymerisiert. Der Einflus von Polymerisationstemperatur und Initiatorkonzentration auf das Polymerisationsverhalten und die molekulare Struktur von Polyvinylpivalat (PVPi) und von durch Verseifung von PVPi in KOH/Methanol/Wasser zu Polyvinylalkohol (PVA) erhaltenen mikrofibrillaren PVA-Fasern wurde untersucht. Durch die niedrige Polymerisationstemperatur mit ADMVN konnte PVA mit einer hohen Syndiotaktizitat und hohem Molekulargewicht erhalten werden. Das PVPi hatte zahlenmittlere Polymerisationsgrade (Pn) von 27 100–35 900 und Verzweigungsgrade der Pivaloylgruppen von 0.8–1.0 bei 30°C, 1.0–1.3 bei 40°C und 1.4–1.7 bei 50°C und Umsatzen jeweils unter 40%. Das durch Verseifung von PVPi erhaltene PVA (Pn = 10 400–16 500) hatte einen Anteil an syndiotaktischen Diaden (S-Diaden) von 58.8–61.5%. Alle PVA-Proben zeigten eine mikrofibrillare Morphologie mit hoher Kristallinitat und Orientierung. Der Gehalt an S-Diaden und die Kristallitschmelztemperatur von PVA waren um so hoher, je niedriger die Polymerisationstemperatur des PVPi war.
TL;DR: In this article, photo-induced-current transient spectroscopy and capacitance-voltage measurements on nominally undoped p-CdTe single crystals grown by a Bridgman method have been carried out to investigate the hydrogenation and the annealing effects on the deep levels and on acceptor neutralization.
TL;DR: In this article, the spin-coated Pb(ZrxTi1-x)O3 (PZT; x=0.2, 0.8) heterolayered thin films were fabricated by the spincoating method on the Pt electrode alternately using PZT(20/80) and PZt(80/20) metal alkoxide solutions.
Abstract: Ferroelectric Pb(ZrxTi1-x)O3 (PZT; x=0.2, 0.8) heterolayered thin films were fabricated by the spin-coating method on the Pt electrode alternately using PZT(20/80) and PZT(80/20) metal alkoxide solutions. All PZT heterolayered films show dense structure without the presence of the rosette structure. The lower PZT layers provide the nucleation site for the formation of a perovskite phase in the upper PZT films. Pb-deficient pyrochlore phase was formed at PZT/Pt interface due to diffusion of the Pb element into the Pt bottom electrode. The relative dielectric constant and dielectric loss of the six coated PZT heterolayered film were approximately 1385 and 3.3% at 1 kHz, respectively.
15 Nov 1999
TL;DR: A proxy server architecture that facilitates highly effective latency reduction over the wireless link without modifying any of the existing applications is proposed and the improvement in the retrieval time is shown.
Abstract: Information access through the WWW has become one of the most important applications for mobile clients. However, efficient wireless data connectivity is difficult to achieve due to physical and technological limitations. In this paper, we propose a proxy server architecture that facilitates highly effective latency reduction over the wireless link without modifying any of the existing applications. Based on the capabilities of the client devices, Web browsers, the user preferences, and Web content types, several different levels of wireless-adaptation for Web content are performed. The functions included in the wireless-adaptation are general-purpose lossless data compression, data-type specific lossy compression and re-authoring of HTML documents. We show the improvement in the retrieval time through experiments in which a mobile host accesses the WWW via the proxy architecture over a CDMA cellular network.
TL;DR: In this paper, a novel method adopting a split-step algorithm is used to numerically solve the time-dependent coupled-wave equations, which are frequently used in the analysis of photonic devices including DFB/DBR structures.
Abstract: A novel method adopting a split-step algorithm is used to numerically solve the time-dependent coupled-wave equations, which are frequently used in the analysis of photonic devices including DFB/DBR structures The new split-step algorithm is shown to be much more accurate and efficient than the conventional algorithm
TL;DR: A new optical stream cipher system based on a threshold generator used as a random key bit stream generator is presented and one of the major advantages of the proposed system is that the programmable tapping points can be realized easily by updating the pixel value represented on LCD.
Abstract: A new optical stream cipher system based on a threshold generator used as a random key bit stream generator is presented. To implement the threshold generator optically, we use conventional twisted nematic type spatial light modulators (SLMs). This proposed system is based on the shadow casting technique for the AND operation between taps and register stages. It is also based on the proposed polarization multiplication by rotation and shift (PMRS) method for modulo-2 addition. The proposed PMRS method uses the property of light polarization on a liquid crystal device (LCD) and can be implemented optically using one LCD and some mirrors. One of the major advantages of the proposed system is that the programmable tapping points can be realized easily by updating the pixel value represented on LCD. We present some simula- tion results that verify this proposed method. © 1999 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(99)00801-6)