• 대한수학회보
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• 제59권1호
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• pp.167-177
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• 2022

A vertex v of a graph G = (V, E) is said to ve-dominate every edge incident to v, as well as every edge adjacent to these incident edges. A set S ⊆ V is called a double vertex-edge dominating set if every edge of E is ve-dominated by at least two vertices of S. The minimum cardinality of a double vertex-edge dominating set of G is the double vertex-edge domination number γ_dve(G). In this paper, we provide an upper bound on the double vertex-edge domination number of trees in terms of the order n, the number of leaves and support vertices, and we characterize the trees attaining the upper bound. Finally, we design a polynomial time algorithm for computing the value of γ_dve(T) for any trees. This gives an answer of an open problem posed in [4].

• ETRI Journal
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• 제44권6호
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• pp.936-944
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• 2022

The mobile network allows redundant transmission via disjoint paths to support high-reliability communication (e.g., ultrareliable and low-latency communications [URLLC]). Although redundant transmission can improve communication reliability, it also increases network costs (e.g., traffic and control overhead). In this study, we propose a reliability-guaranteed multipath allocation algorithm (RG-MAA) that allocates appropriate paths by considering the path setup time and dynamicity of the reliability paths. We develop an optimization problem using a constrained Markov decision process (CMDP) to minimize network costs while ensuring the required communication reliability. The evaluation results show that RG-MAA can reduce network costs by up to 30% compared with the scheme that uses all possible paths while ensuring the required communication reliability.

• 전자통신동향분석
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• 제39권3호
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• pp.36-47
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• 2024

Low Earth Orbit (LEO) satellite communications has become a crucial technology for next-generation communication networks owing to its hyperconnectivity capabilities. We examine the progress and application areas of LEO satellite communication services. The LEO satellite communication industry has transitioned from being predominantly driven by governments and institutions to being led by the private sector, following the trajectory of the NewSpace movement. Leading corporations such as SpaceX Starlink and Eutelsat OneWeb are deploying LEO satellite networks to offer internet services, while Telesat is preparing to establish its satellite communication network. LEO satellite communications is expected to have a major impact on various sectors of society, particularly for upcoming sixth-generation services. Therefore, the South Korean government must promptly formulate policy support strategies aimed at invigorating the LEO satellite communication industry. This can be achieved through initiatives such as bolstering research and development and extending corporate assistance.

• Fisheries and Aquatic Sciences
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• 제5권4호
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• pp.295-301
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• 2002

Experiments were carried out to investigate the effects of metal interaction on the accumulation and elimination of Cd and Cu in the liver of flounder, Paralichthys olivaceus, exposed to sub-chronic Cd (0, 5, 10, 50, 100 ${\mu}g/L$)/Cu $(10 {\mu}g/L)$ mixture. Cd exposure resulted in an increased Cd accumulation in the liver of flounder for exposure periods and concentration, and Cd accumulation increased linearly with exposure time. Cu accumulation profiles were similar to those of Cd. Cd concentration in the liver significantly decreased at the 10th depuration period and elimination rate was $66.20\%,\;86.22\%$ in 50 and $100 {\mu}g/L$at the end of depuration periods, respectively. Although, Cu elimination was similar to Cd elimination phase, Cd elimination rate was higher than that of Cu. Co-relationship of Cd and Cu have a positive correlation coefficient r=0.8620 (P<0.001) and support the strong relationship between Cd and Cu accumulation. As increase with the Cd exposure concentration, there were significant (P<0.001) differences between Cd and Cu accumulation.

• 생명과학회지
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• 제14권4호
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• pp.593-607
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• 2004

유해성 적조생물 Cochlodinium polykrikoides/Gyrodinium aurelum을 포함한 43 종류의 와편조류를 대상으로 SSU 부위 유전자를 분석했다. 유전자 염기서열에 의거한 상호 계통수는 parisomny, distance, maxium 방법으로 실행했다. Noctilura scintillans, Gonyaulax spinifera와 Crythecodinium cohnii 종들은 와편모조류 중 가장 유전적으로 먼 것으로 보였다. Alexandrium과 Symbiodinium 종간의 bootstrap는 70% 이상의 상호 단일 계통도를 보인 반면에, Gymnodinium과 Gyrodinium은 근립절약계수와 최대 유사도 방법에서 다형 계통도를 나타내었다. Gyroddinium aurelum과 G. dorsum/G. galathenum의 유전적 분화율은 7.4% (45 bp) 였고, G. aurelum과 G. mikimotoi 상호간에는 0.9% (5bp) 밖에 나타나지 않았다. 또한 C. polykrikoides와 G. aurelum도 5.2% (31bp)로 낮은 유전적 분화율을 보였다. 계통도를 분석한 결과 G. aureolum과 C. polykrikoides는 Gyrodinium 보다 Gymnodinim 속에 훨씬 더 근접하게 나타났다.

• The Korean Journal of Physiology
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• 제30권1호
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• pp.77-83
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• 1996

Platelet-activating factor(PAF) is a phospholipid mediator of pulmonary inflammation, and immunologic reaction. In this study, the role of PAF on tumor necrosis factor$(TNF_{-{\alpha}})$ production by rat alveolar macrophages(AM) was examined. When PAF $(10^{-12}{\sim}10{-16}\;M)$ alone was added to AM culture, $(TNF_{-{\alpha}})$ production was not significantly increased above the resting level. In contrast, the combined addition of PAF $(10^{-6}\;M)$ and muramyl dipeptide(MDP) $(1.0\;{\mu}g\ml)$ to AM cultures markedly enhanced $(TNF_{-{\alpha}})$ production with 8.2 fold increase compared with AM culture in resting state. This potentiative effect was 313% above the sum of the separate effects of PAF and MDP. To characterize MDP effects on $(TNF_{-{\alpha}})$ production, the dose-response of AM cultured with various concentrations of MDP was tested. High level of MDP $(10\;{\mu}g\ml)$ could not significantly enhance the potentiation effect on $(TNF_{-{\alpha}})$ production compared with AM cultures with low level of MDP $(0.1\;{\mu}g\ml)$, i.e. 112.5% vs 107.8%, respectively when $10^{-10}$ M of PAF was simultaneously added to the cell culture. These data support that the potentiation of TNF. g production in AM culture is mediated by PAF rather than MDf It was also evaluated whether the similar result was obtained in silica, respirable toxic particle-treated AM culture. $(TNF_{-{\alpha}})$ production was also significantly enhanced in the PAF $(10^{-6}\;M)$ and silica $(50\;{\mu}g\ml)$-added cell cultures with 4.7 fold above the value of silica alone-stimulated cells. These results indicate that PAF can potentiate $(TNF_{-{\alpha}})$ production by MDP-or silica- stimulated AM and suggest that PAF may play a potent role in lung inflammation and disease associated with microbe and occupational dust exposures.

• 한국환경과학회지
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• 제16권9호
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• pp.1071-1076
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• 2007

Polychlorinated biphenyls(PCBs) and polybrominated diphenyl ethers (PBDEs) were measured in pine needles of Seoul, and Ansung(GyeongGi-do) to investigate composition, source, and regional concentration of PBDEs. Concentration of total PCBs in Seoul and Ansung showed 608, 945 pg/g DW (mean: 777 pg/g DW), respectively, also concentration of total PBDEs(pg/g DW) in Seoul and Ansung showed 7944, 14,255 pg/g DW(mean 11,100 pg/g DW). Tetrachlorinated biphenyls(Tetra-CBs) and Decabromodiphenyl ethers (Deca-BDE) were detected in relatively high concentration compared to other PBDE congeners in Seoul and Ansung. Correlation coefficients(r) of between PCB congeners in pine needles detected of Seoul and Ansung were significant (r=0.85, p<0.01). It suggested that PCBs concentration in pine needles may originate from secondary sources such as air-plant partition. The similarity of between PBDE congeners profile to those of the technical mixture formulation (Bromkal 70-5DE) suggests a source of this product in these sites.

• 한국컴퓨터정보학회논문지
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• 제17권11호
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• pp.93-99
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• 2012

B3G 네트워크는 이종의 네트워크 시스템 및 서비스에 대한 연동을 제공하는 차세대 네트워크 기술로 사용자 요구에 맞는 서비스 제공을 목적으로 구성된다. 본 논문에서는 B3G 네트워크에서 액세스 네트워크로 사용될 수 있는 UMTS와 WLAN과 같은 이종 네트워크에 대한 시스템 연동 방안을 기술하며, 각 네트워크에서의 서비스 제공 및 이종 액세스 네트워크를 기반으로 한 서비스 연동 방안을 기술한다. UMTS와 WLAN 시스템은 각 네트워크 특성에 맞는 서비스를 제공하며 B3G 네트워크 구성에 참여하여 상호 보완적인 서비스 제공을 통하여 이동 가입자의 서비스 사용 효과를 증대시킬 수 있다.

• 한국수산과학회지
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• 제36권2호
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• pp.163-169
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• 2003

The floating bead filter was tested for treatment of aquacultural water in a pilot-scale recirculating aquaculture system. Performance of floating bead filter on the removal of total suspended solids (TSS) and the treatment of nitrogen sourer such as total ammonia nitrogen (TAN), nitrite nitrogen and nitrate nitrogen were evaluated. The system was stocked with Nile tilapia at an initial rearing densities of $5\%\;and\;7\%$ over 30 days. The average TSS removal rates were $43.0\;g/m^2{\cdot}day\;and\;39.5\;g/m^2{\cdot}day$ for rearing density of $5\%\;and\;7\%$, respectively. As rearing density increased from $5\%\;to\;7\%$. the TAN removal efficiency decreased from $22.0\%\;to\;17.7\%$. At the rearing densities of $5\%\;and\;7\%$, the average TAN removal rates and removal efficiencies were $38.8\;g/m^2{\cdot}day,\;15.6\%\;and\;37.8\;g/m^2{\cdot}day.\;17.7\%,$ respectively. The average TAN removal rate was $37.8-38.8\;g/m^3{\cdot}day.$ The oxygen consumption by floating bead filter was higher than theoretical oxygen consumption rate by nitrification.

• ETRI Journal
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• 제38권6호
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• pp.1052-1063
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• 2016

We propose a millimeter wave (MMW)-based mobile hotspot network (MHN) system for application in high-speed railways that is capable of supporting a peak backhaul link throughput of 1 Gbps per train at 400 km/h. The MHN system can be implemented in subways and high-speed trains to support passengers with smart devices and provide access to the Internet. The proposed system can overcome the inherent high path loss in MMW through system designs and high antenna gains. We present a simulation of the system performance that shows that a fixed beamforming strategy can provide high signal-to-interference-plus-noise-ratio similar to those of an adaptive beamforming strategy, with the exception of 15% of the train path in which the network can use link adaptation with low-order modulation formats or trigger a handover to maintain the connection. We also demonstrate the feasibility of the MHN system using a test bed deployed in Seoul subway line 8. The backhaul link throughput varies instantaneously between 200 Mbps and 500 Mbps depending on the SNR variations while the train is running. During the field trial, the smartphones used could make connections through offloading.