• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.12
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• pp.1328-1336
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• 2012

Compared to terrestrial RF communications, underwater acoustic communications have several limitations such as limited bandwidth, high level of fading effects, and a large underwater propagation delay. In this paper, in order to tackle those limitations of underwater communications and to make it possible to form a large underwater monitoring systems, we propose a hierarchical underwater network architecture, which consists of underwater sensors, clusterheads, underwater/surface sink nodes, autonomous underwater vehicles (AUVs). In the proposed architecture, for the maximization of packet delivery ratio and the minimization of underwater sensor's energy consumption, a hybrid routing protocol is used. More specifically, cluster members use Tree based routing to transmit sensing data to clusterheads. AUVs on optimal trajectory movements collect the aggregated data from clusterhead and finally forward the data to the sink node. Also, in order to minimize the maximum travel distance of AUVs, an Integer Linear Programming based algorithm is employed. Performance analysis through simulations shows that the proposed architecture can achieve a higher data delivery ratio and lower energy consumption than existing routing schemes such as gradient based routing and geographical forwarding. Start after striking space key 2 times.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1C
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• pp.67-77
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• 2007

Virus throttling technique, one of many early worm detection techniques, detects Internet worm propagation by limiting connect requests within a certain ratio. The typical virus throttling controls the period of rate limiter autonomically by utilizing weighted average delay queue length to reduce connection delay time without hanving a large effect on worm detection time. In the existing virus throttling research, a minimum period of variable rate limiter is fired and a turning point which is a point that the period of rate limiter has been being decreased and starts to be increased is also fixed. However, these two performance factors have different effects on worm detection time and connection delay. In this paper, we analyze the effect of minimum period and turning point of variable rate limiter, and then propose an algorithm which determines values of performance factors by referencing current traffic pattern. Through deep experiments, it is verified that the proposed technique is more efficient in respect of reducing worm detection time and connection delay than the existing virus throttling which fixed the performance factors.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.8
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• pp.1790-1802
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• 1997

A wavelet transform coding method that fulfills the requirements of HD-VCR(high definition video casstte recorder) for studio applications in proposed. A constant bit rate is achieved by a forward rate control technique whcih determins the quantizer stepsize based on the coding results fo the previous frame. We also propose a two-level coder that consists of both the IDC(independently decodable code) and the DDC(dependently decodable code). To minimize error propagation, the transformed coefficients are restructured into transform blocks which are represented by a tree structure. The result shows thta the proposed coding scheme produces better picture quality with block effects than that of DCT(discrete cosine transform) based coding schemes at the same compression ratio. The proposed method meets most of the requirements of HD-VCR.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.1563-1570
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• 2015

Conformational change during chain propagation of alanine oligomer was investigated by quantum chemical calculation(QCC) using 2~5mers(${\times}=2{\sim}5$) models. For estimation of the end group effects, two types of end group. "amide type" ($CH_3CONH-and-CONHCH_3$) and "methyl type" ($CH_3CONH-and-CONHCH_3$), were prepared as both ends(N-and-C). Conformers optimized for 5-mer converged to three types of ${\Phi}/{\Psi}$ : ${\alpha}$-helix(g+/g+, or g-/g-), PPII-like(extended helix-like, g+/g-, or g-/g+), and ${\beta}$-extended (t+/t-, or t-/t+), in the order of lower energy, and the energies of left- and right- handed conformers were the same (5-mer. amide type ${\Delta}E=-1.05$, right type ${\Delta}E=-1.62$). Energies of the monomer unit(${\Delta}E$) of ${\alpha}$-helix decreased with increases of monomer.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.9B
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• pp.1527-1533
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• 2000

Basically, a general characterization procedure based on the extraction of the characteristic impedance and propagation constant for analyzing a single MIS(Metal-Insulator-Semiconductor) transmission line is used. In this paper, an analysis for a new substrate shielding MIS structure consisting of grounded cross-bars at the interface between Si and SiO2 layer using the Finite-Difference Time-Domain (FDTD) method is presented. In order to reduce the substrate effects on the transmission line characteristics, a shielding structure consisting of grounded cross bar lines over time-domain signal has been examined. The extracted distributed frequency-dependent transmission line parameters and corresponding equivalent circuit parameters as well as quality factor have been examined as functions of cross-bar spacing and frequency. It is shown that the quality factor of the transmission line can be improved without significant change in the characteristic impedance and effectve dielectric constant.

• Korean Journal of Medicinal Crop Science
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• v.20 no.1
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• pp.47-53
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• 2012

This study was conducted to examine effects of plant growth regulators and light resources on the formation of multiple shoot and plant regeneration of Hovenia dulcis var. koreana Nakai. Stem and shoot tip were cultured on MS medium or WPM supplemented with various plant growth regulators. At the single treatment, the highest shoot formation was obtained when stem explants were cultured on WPM supplemented with kinetin $1.0mg{\cdot}L^{-1}$. MS medium containing NAA 0.1 and TDZ $0.1mg{\cdot}L^{-1}$ gave the best results for shoot induction rate and shoot growth in combination treatments. Of the BAP and kinetin tested, BAP $0.5mg{\cdot}L^{-1}$ on WPM was found to be more effective for shoot growth from shoot tip. Under white fluorescent light treatment, shoot growth was much higher than blue, red LED treatments. Root induction from in vitro growth of plantlet was the best on WPM supplemented with $1.0mg{\cdot}L^{-1}$ IBA. The results suggest that selection of plant growth regulators and light resources could be important factor to achieve an efficient in vitro growth.

• Tribology and Lubricants
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• v.13 no.2
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• pp.96-104
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• 1997

This paper was focused on the wear characteristics of ion-nitrided metal and with ion-nitride processing, which is basically concerned with the effects of carbon content in workpiece and added carbon content gas atmosphere on the best wear performance. Increased carbon content in workpiece increases compound layer thickness, but decreases diffusion layer thickness. On the other hand, a small optimal amount of carbon content in gas atmosphere increase compound layer thickness as well as diffusion layer thickness and hardness. Wear tests show that the compound layer of ion-nitrided metal reduces wear rate when the applied wear load is small. However, as the load becomes large, the existence of compound layer tends to increase wear rate. Compressive residual stress at the compound layer is the largest at the compound layer, and decreases as the depth from the surface increases. It is found in the analysis that under small applied load, the critical depth where voids and cracks may be created and propagated is located at the compound layer, so that the adhesive wear is created and the existence of compound layer reduces the amount of wear. When the load becomes large, the critical depth is located below the compound layer and delamination, which may explained by surface deformation, crack nucleation and propagation, is created and the existence of compound layer increases wear rate. For the compound layer, at added carbon contents of 0 percent and 0.5 at. percent, the $\varepsilon$ monophase is predominant. But at 0.7 at. percent added carbon, the $\varepsilon$ monophase formation tends to be severely inhibited and r' and $Fe_3C$ polyphase formation becomes dominant. This increased hard $\varepsilon$ phase layer was observed to be more beneficial in reducing friction and wear.

• Korean Journal of Plant Tissue Culture
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• v.25 no.2
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• pp.119-123
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• 1998

In order to investigate the possibility of in vitro mass propagation via somatic embryogenesis from Sicyos angulatus L., effects of plant growth regulators and carbon sources on callus induction and somatic embryogenesis were evaluated. Optimal combinations of plant growth regulator for callus induction from cotyledon and inflorescence explants were 2,4-D 2.0 mg/L + BA 0.1 mg/L and 2,4-D 1.0 mg/L + BA 0.1 mg/L in MS basal medium supplemented with sucrose 30 g/L,, respectively. Somatic embryogenesis was observed from cultured inflorescence explants, but it could not be achieved from leaf or cotyledon explants. The most effective plant growth regulators for somatic embryogenesis from callus was NAA 1.0 mg/L + kinetin 10 mg/L in the half strength of MS basal medium supplemented with 20 g/L sucrose.

• Korean Journal of Plant Tissue Culture
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• v.25 no.3
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• pp.171-175
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• 1998

Chinese foxglove (Rehmannia glutinosa) is receiving much attention as one of the principal medicinal crops and the crude drug damand expands rapidly.This study was conducted to obtain the basic breeding information of Chinese foxglove. Effects of supplemental plant growth regulators were investigated on leaf tissue for proliferation. 100% callus formation, 31% plantlet regeneration and 6% root differentiation were obtained by adding 0.5 mg/L NAA and 2.0 mg/L BA. 2,4-D and Zeatin treatment also resulted in 95% increase in callus formation, but shoot was not formed. During the subculture, callus propagation rate recorded 15.4% with 0.2 mg/L NAA and 1.0 mg/L BA and plant regeneration improved on MS medium supplemented with 0.2 mg/L NAA and 0.5 mg/L kinetin. The number of shoot formed ranged from 1.7 on WPM medium to 3.4 on MS medium with 0.1 mg/L NAA and 0.5 mg/L BA. Supplementation of 1.0 g/L activated charcoal improved the In vitro plant growth.

• Journal of Plant Biotechnology
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• v.41 no.4
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• pp.236-241
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• 2014

An efficient regeneration protocol for stem disc culture of Populus euramericana, which is important species for bioenergy resource in agroforestry, was established. The number of explants that were obtained and the number of explants that regenerated varied with the genotypes. However, in all the genotypes, stem disc culture produced more regenerated shoots than did in axillary bud culture. A comparison of the effects of cytokinin type and concentration on shoot regeneration in different explants (i.e., petiole, leaf, and root segments of P. euramericana) revealed that a concentration of $0.002mg\;l^{-1}$ thidiazuron (TDZ) used on petiole segments resulted in the greatest shoot regeneration (95.83%). The hormonal requirements for the greatest shoot regeneration in the three explant types varied. Different concentrations of $AgNO_3$ and $CoCl_2$ were added separately to the medium to stop the yellowing and subsequent necrosis of the regenerated shoots. Lower concentrations (3 and $5mg\;l^{-1}$) of these compounds improved shoot regeneration and elongation, compared with the control. The in vitro-regenerated shoots were transferred to rooting medium and subsequently acclimatized. The highly efficient regeneration system of P. euramericana reported here can be used for mass propagation of this recalcitrant for regeneration, economically important tree species.