• International Journal of Computer Science & Network Security
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• v.22 no.11
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• pp.241-247
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• 2022

Ad hoc network is self-organized network powered by battery. The reliability of virtual user identification and channel security are reduced when SNR is low due to limited user energy. In order to solve this problem, a joint virtual user identification and channel security en/decoding method is proposed in this paper. Transmitter-receiver-based virtual user identification code is generated by executing XOR operation between orthogonal address code of transmitter and pseudo random address code of receiver and encrypted by channel security code to acquire orthogonal random security sequence so as to improve channel security. In order to spread spectrum as well as improve transmission efficiency, data packet is divided into 6-bit symbols, each symbol is mapped with an orthogonal random security sequence. Subspace-based method is adopted by receiver to process received signal firstly, and then a judgment model is established to identify virtual users according to the previous processing results. Simulation results indicate that the proposed method obtains 1.6dB E_b/N₀ gains compared with reference methods when miss alarm rate reaches 10^-3.

• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.6
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• pp.237-246
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• 2022

Based on the random-vibration-theory methodology, dynamic responses of nuclear facilities subjected to obliquely incidental and incoherent earthquake ground motions are calculated. The spectral power density functions of the 6-degree-of-freedom motions of a rigid foundation due to the incoherent ground motions are obtained with the local wave scattering and wave passage effects taken into consideration. The spectral power density function for the pseudo-acceleration of equipment installed on a structural floor is derived. The spectral acceleration of the equipment or the in-structure response spectrum is then estimated using the peak factors of random vibration. The approach is applied to nuclear power plant structures installed on half-spaces, and the reduction of high-frequency earthquake responses due to obliquely incident incoherent earthquake ground motions is examined. The influences of local wave scattering and wave passage effects are investigated for three half-spaces with different shear-wave velocities. When the shear-wave velocity is sufficiently large like hard rock, the local wave scattering significantly affects the reduction of the earthquake responses. In the cases of rock or soft rock, the earthquake responses of structures are further affected by the incident angles of seismic waves or the wave passage effects.

• Journal of Ocean Engineering and Technology
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• v.36 no.3
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• pp.161-167
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• 2022

Three-dimensional finite element analysis (3D-FEA) models have been used to evaluate the shock-resistance responses of various equipments, including armaments mounted on a warship caused by underwater explosion (UNDEX). This paper aims to check the possibility of using one-dimensional (1D) FEA models for the shock-resistance responses. A frigate was chosen for the evaluation of the shock-resistance responses by the UNDEX. The frigate was divided into the thirteen discrete segments along the length of the ship. The 1D Timoshenko beam elements were used to model the frigate. The explosive charge mass and the stand-off distance were determined based on the ship length and the keel shock factor (KSF), respectively. The UNDEX pressure fields were generated using the Geers-Hunter doubly asymptotic model. The pseudo-velocity shock response spectrum (PVSS) for the 1D-FEA model (1D-PVSS) was calculated using the acceleration history at a concerned equipment position where the digital recursive filtering algorithm was used. The 1D-PVSS was compared with the 3D-PVSS that was taken from a reference, and a relatively good agreement was found. In addition, the 1D-PVSS was compared with the design criteria specified by the German Federal Armed forces, which is called the BV043. The 1D-PVSS was proven to be relatively reasonable, reducing the computing cost dramatically.

• Journal of the Korean Wood Science and Technology
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• v.14 no.4
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• pp.14-20
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• 1986

These experiments were carried out to determine the ultraviolet absorption spectra of AcBr lignins(acetyl bromide lignin) from 10 hardwood species grown in Mt. Jiri. 1. There were 3 peak positions, at 249nm(max. peak), at 262-266nm(shallow min. peak) and at 270-280nm(lower max. peak). The Bj$\ddot{o}$rkman lignin and lignin sulfonatic acid spectra had shoulders, but the AcBr lignin didn't. 2. Average absorbances of the AcBr lignin at peak positions were 0.457${\pm}$0.0077 at 249nm, 0.297${\pm}$0.0029 at 262-266nm and 0.309${\pm}$0.0067 at 270-280nm. 3. Average absorptivities of the AcBr lignin at peak positions were 25.005${\pm}$0.3825 at 249nm, 16.264${\pm}$0.2347 at 262-266nm and 16.863${\pm}$0.3444 at 270-280nm. 4. AcBr lignin absorptivities in each species were as follows: 16.939${\pm}$0.3735 in Acer pseudo-sieboldianum var. koreanum, 17.411${\pm}$0.2937 in Carpinus laxiflora, 16.579${\pm}$0.4348 in Comus controversa, 16.385${\pm}$0.4140 in Fraxinus rhynchophylla, 16.287${\pm}$0.4156 in Meliosma myriantha, 16.492${\pm}$0.1432 in Platycarya strobilacea, 16.343${\pm}$0.3177 in Prunus sargentii, 17.549${\pm}$0.3253 in Sophora japanica, 18.400${\pm}$0.2925 in Stewartia koreana, 16.245${\pm}$0.4339 in Styrax obassia. 5. As the spectra of AcBr lignin from hardwood showed the unpromounced peak from 270nm to 280nm, it was supposed that thes hardwood lignins were the guaiacyl-syringyl copolymers.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.2
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• pp.137-143
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• 2006

Three candidate processes(ozone alone, UV alone and ozone/UV combined processes) were evaluated for the removal of diethyl phthalate(DEP). Of the candidates, the ozone/UV process showed the highest removal efficiency of DEP. To elucidate a major oxidant for DEP oxidation in the ozone/UV process, the effects of pH and hydroxyl radical($OH^{\circ}$) scavenger were investigated. As a result, it was found that $OH^{\circ}$ plays a important role for DEP elimination. Meanwhile, the direct reaction between ozone and DEP was negligible. Observing the pseudo first-order rate of DEP removal in ozone alone and ozone/UV processes, the different pattern was obtained from two processes. The ozone/UV process was well plotted following the pseudo first-order. but in the ozone alone process the rate was divided into fast and slow phases. DEP degradation characteristics in ozone alone and ozone/UV was also investigated by observing the HPLC spectrum. We detected unknown compounds that were guessed to DEP byproducts and observed the formation and disappearance of the unknown compounds according to reaction time. Observing of high removal of TOC in ozone/UV combined process, it was found that DEP and DEP byproducts are completely oxidized by ozone/UV combined process.

• Korean Journal of Optics and Photonics
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• v.31 no.5
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• pp.223-230
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• 2020

In this paper, we have studied the characteristics of stimulated Brillouin scattering (SBS) and mode instability (MI) in a ytterbium-doped polarization-maintaining fiber laser with master oscillator power amplifier configuration. We measured the laser output power and back-reflection spectrum for a variety of ytterbium-doped fibers and seed lights, to investigate the power-scaling limits of fiber lasers. By optimizing the laser structure, we demonstrated an all-fiber high-power polarization-maintaining fiber laser with near-diffraction-limited beam quality. The output power of 1.5 kW was achieved with a linewidth of 10 GHz, generated by pseudo-random binary sequence (PRBS) phase modulation. The beam quality M² was about 1.15 at the maximum output power. The polarization extinction ratio (PER) was greater than 17 dB.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.1 s.53
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• pp.67-77
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• 2007

Site coefficients in IBC and KBC codes have some limits to predict the rational seismic responses of a structure, because they take into account only the effect of the soil amplification without the effects of the structure-soil interaction. In this study, upper and lower limits of the site coefficients are estimated through the pseudo 3-D elastic seismic response analyses of structures built on the linear or nonlinear soil layers taking Into account the effects of the structure-soil interaction. Soil characteristics of site classes of A, B and C were assumed to be linear, and those of site classes of D and E were done to be nonlinear and the Ramberg-Osgood model was used to evaluate shear modulus and damping ratio of a soil layer depending on the shear wave velocity of the soil layer, Seismic analyses were performed with 12 weak or moderate earthquake records scaled the peak acceleration to 0.1g or 0.2g and deconvoluted as earthquake records at the bedrock located at 30m deep under the outcrop. With the study results of the elastic seismic response analyses of structures, new standard response spectrum and upper and lower limits of the site coefficients of $F_{a}\;and\;F_{v}$ at the short period range and the period of 1 second are suggested including the effects of the structure-soil interaction, and new site coefficients for the KBC code are also suggested.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.10C
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• pp.1032-1041
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• 2007

The global navigation satellite system (GNSS), which is the core technique for the location based service, adopts the direct sequence/spread spectrum (DS/SS) as its modulation method. The success of a DS/SS system depends on the synchronization between the received and locally generated pseudo noise (PN) signals. As a step in the synchronization process, the tacking scheme performs fine adjustment to bring the phase difference between the two PN signals to zero. The most widely used tracking scheme is the delay locked loop with early minus late discriminator (EL-DLL). In the ideal case, the EL-DLL is the best estimator among various DLL. However, in the band-limited multipath environment, the EL-DLL has tracking bias. In this paper, the timing offset range of correlation function is divided into advanced offset range (AOR) and delayed offset range (DOR) centering around the correct synchronization time point. The tracking bias results from the following two reasons: symmetry distortion between correlation values in AOR and DOR, and mismatch between the time point corresponding to the maximum correlation value and the synchronization time point. The former and latter are named as the type I and type II tracking bias, respectively. In this paper, when the receiver has finite bandwidth in the presence of multipath signals, it is shown that the type II tracking bias becomes a more dominant error factor than the type I tracking bias, and the correlation values in AOR are not almost changed. Exploiting these characteristics, we propose a novel tracking bias mitigation scheme and demonstrate that the tracking accuracy of the proposed scheme is higher than that of the conventional scheme, both in the presence and absence of noise.

• The Korean Journal of Ecology
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• v.16 no.4
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• pp.439-457
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• 1993

The present study was undertaken to classify and describe the forest vegetation on Imha-dam area, located at the northern part of Kyungsang-pookdo, Korea by the phytosociological method of the Z-M school. The field investigations were carried out in 60 plots around the dam area from May 1, 1991 to October 10, 1992. The vegetation data obtained were classified by the table comparison method. As a result, the following vegetation units were recognized: A. Pinus densiflova community A-a. Miscanthus sinensis group A-b. Carex humilzs group A-c. Typical group B. Quercetum variabili-serratae Kobayashi, Muranaga et Takeda 1976 C. Robinin pseudo-acacia-Conzmeli~ta comnzultis community D. Larix leptolepis community The vascular plant species of these forest communities consist of 63 families, 144 genera, 191 species and 30 varieties. Also the relationship of the vegetation units with their environments such as altitude, slope, topography and soil condition was discussed here. On the basis of the floristic composition, life-form spectrum and soil analysis, a sere for the forest vegetation was proposed as follows: Rohinia pseitdo-acacia-Conz~neli~za communis community and Larix leptolepis community $\rightarrow$ Pinus densiflora community $\rightarrow$ Quercetunz variahili-serratae $\rightarrow$ Quercus mongolica community. Lastly, relating to the nature conservation of dam area, some of plans were discussed.

• BMB Reports
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• v.28 no.2
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• pp.112-117
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• 1995

Succinic semialdehyde reductase was inactivated by o-phthalaldehyde. The inactivation followed pseudo-first order kinetics, and the second-order rate constant for the inactivation process was 28 $M^{-1}s^{-1}$ at pH 7.4 and $25^{\circ}C$. The absorption spectrum ($\lambda_{max}$ 337 nm) and fluorescence excitation ($\lambda_{max}$ 340 nm) and fluorescence emission spectra ($\lambda_{max}$ 409 nm) were consistent with the formation of an isoindole derivative in the catalytic site between a cysteine and a lysine residue approximately about 3 $\AA$ apart. The substrate, succinic semialdehyde, did not protect enzymatic activity against inactivation, whereas the coenzyme NADPH protected against o-phthaladehyde induced inactivation of the enzyme. About 1 isoindole group per mol of the enzyme was formed following complete loss of enzymatic activity. These results suggest that the amino acid residues of the enzyme participating in a reaction with o-phthalaldehyde are cysteinyl and lysyl residues at or near the NADPH binding site.