• Ocean Systems Engineering
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• 제12권2호
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• pp.247-265
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• 2022

In the present study, we focus on the CFD simulations for the performance and the rotor-generated wake of a model-scale wind turbine which was designed for wave tank experiments. The CFD simulations with fully resolved rotor geometry are performed using MARIN's community-based open-source CFD code ReFRESCO. The absolute formulation method (AFM) is leveraged to model the rotating wind turbine. The k - ω SST turbulence model is adopted in the incompressible Reynolds Averaged Navier-Stokes (RANS) simulations. First, the thrust and torque coefficients, C_T and C_P, are calculated at different Tip Speed Ratios (TSR), and the results are compared against the experimental data and previous numerical results. The pressure distribution of the turbine blades at the 70% span is obtained and compared to the results obtained by other tools. Then, a verification study aiming at quantifying the discretization uncertainty of the turbine performance with respect to the grid resolution in the wake region is performed. Last, the rotor-generated wake at the TSR of 7 is presented and discussed.

• 한국항해항만학회지
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• 제31권10호
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• pp.859-864
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• 2007

미래 항만내 항법에서 요구하는 sub-meter 수준의 위치정확도를 만족하기 위해 DGPS와 같은 위성전파항법 보강시스템의 활용이 필요하다. 일반적으로 해양에서 사용하는 DGPS 기준국용 수신기는 RSIM Ver. 1.1에서 제시한 DGPS 기준국용 수신기 성능 요구사항을 만족해야 하고, 이에 대한 성능검증이 필요하다. 본 논문에서는 해양에서 사용하는 DGPS 기준국용 수신기의 성능검증방법을 제안하였다. 그리고 제안한 DGPS 기준국용 수신기 성능검증 방법으로 실시한 상용 DGPS 기준국용 수신기의 성능검증 실험을 통하여 제안한 성능검증 방법을 검증하였다.

• 전기저널
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• 2호통권98호
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• pp.16-22
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• 1985

• 한국대기환경학회지
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• 제31권3호
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• pp.201-208
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• 2015

We investigated the pollution levels of $PM_{2.5}$ at Wangsimni station at which four subway lines (Line 2, Line 5, the Jungang line, and the Bundang Line) are simultaneously under the operation. The analysis of $PM_{2.5}$ was made for the period of 1~ 11 Nov. 2014. The results of our field campaign were analyzed to assess the effects of various factors and conditions on the $PM_{2.5}$ pollution (such as installation of the screen door, density of floating population, weekdays and weekend, and the depth of platforms). The mean concentrations of $PM_{2.5}$ in each subway line of the Wangsimni station was measured as: the line 2 ($22.5{\mu}g/m^3$) ; the line 5 ($18.3{\mu}g/m^3$) ; the Jungang line ($31.8{\mu}g/m^3$); and the Bundang line ($32.2{\mu}g/m^3$). Based on the detailed analysis of $PM_{2.5}$ pollution at four subway lines, we aimed to provide some perspectives on reducing the concentration of ultrafine particles in a highly populated urban area.

• 한국대기환경학회지
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• 제29권6호
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• pp.701-712
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• 2013

The purpose of this study is to determine concentrations and compositions of $PM_{2.5}$ and their characteristic variations at Ieodo Ocean Research Station in the East China Sea and to examine the influence of air pollutants transported from Asia continents. $O_3$ and meteorological parameters were measured since June 2003 and $PM_{2.5}$ filter samples were collected from June 2004 to June 2008. In total, 244 samples were analyzed for water soluble ions and carbonaceous compounds. The mean mass concentration of $PM_{2.5}$ and $O_3$ were $21.8{\pm}14.9{\mu}g/m^3$ and $51.6{\pm}16.1$ ppb, respectively. The average concentrations (mass fractions) of sulfate and ammonium were $6.26{\mu}g/m^3$ (28.74%) and $1.59{\mu}g/m^3$ (7.31%), respectively. Nitrate was considered to be lost through evaporation due to long stay at the station. The mean concentrations of EC and OC were $1.01{\mu}g/m^3$ and $2.34{\mu}g/m^3$, respectively, from June 2006 to June 2008. The average OC/EC ratio was 2.31. The organic matter converted from OC by multiplying 2.1 and elemental carbon constituted 22.60% and 4.66% of $PM_{2.5}$ mass, respectively.

• Plant Resources
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• 제6권1호
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• pp.16-26
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• 2003

Molecular markers are useful tools for evaluating genetic diversity and determining cultivar identity. Present study was conducted to evaluate the genetic diversity within a diverse collection of rice accessions used for Korean breeding programs. Two hundred eighty-seven rice cultivars, composed of temperate japonica, tropical japonica, indica, and Tongil-type of Korean crossing parents were evaluated by means of 15 simple sequence repeat (SSR) markers. A total of 99 alleles were detected, and the number of alleles per marker ranged from 4 to 11, with an average of 6.6 per locus. Polymorphism information content (PIC) for each of the SSR markers ranged from 0.2924 to 0.8102 with an average of 0.5785. These results, with the result that use of only 15 SSR markers made all rice cultivars examined could be uniquely distinguished, imply the efficiency of SSR markers for analysis of genetic diversity in rice. Cluster analysis was performed on similar coefficient matrics calculated from SSR markers to generate a dendogram in which two major groups corresponding to japonica (Group I) and indica and Tongil type rice (group II) with additional subclasses within both major groups. The narrowness of the Korean breeding germplasm was revealed by the fact that most of the Korean-bred and Japan-bred temperate japonica cultivars were concentrated into only 2 of the sub-group I-1 (143 cultivars) and I-2 (58 cultivars) among six sub-groups in major group of japonica. This is because of the japonica accessions used in this study was a very closely related ones because of frequent sharing of the crossing parents with similar genetic background with synergy effect of the inherited genetic difference between indica and japonica. A rice breeding strategy with the use of molecular markers was discussed for overcoming of genetic vulnerability owing to this genetic narrowness.

• 한국수산과학회지
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• 제56권5호
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• pp.701-707
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• 2023

We investigated Euphausia pacifica population in Korean waters in 2016 By samplings for genetic structur at five stations. Three sampling stations were located in the middle of the water masses which were clustered by temperature and salinity whereas the other stations were at the boundaries of the water masses. We amplified a 566 bp region and compared it with sequences of E. pacifica distributed in other waters. Sequences were classified two clades, and a clade was formed in the station E. Genetic distance of station E was close to E. pacifica present in Bering Sea, while it was distant to E. pacifica present in Yellow Sea near China. In genetic analysis, seven haplotypes were formed. Hap-1 and Hap-2 were shared in all five stations, while Hap-3 was shared in station W and WS. Four independent haplotypes were present in station E. Haplotype and nucleotide diversity were the highest in station E and the lowest in station S. The F_ST distances between station E and other stations were the highest, but distances among other stations were low. As a result, we concluded that E. pacifica, which is distributed in Korean waters, has a genetic population differentiation in the East Sea (station E).

• 한국항행학회논문지
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• 제27권6호
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• pp.782-787
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• 2023

KASS (korea augmentation satellite system) 시스템 통합 및 검증(IVQ; integration, verification, qualification) 활동은 시스템 및 하위시스템 요구사항 검증 활동으로 IART(inspection, analysis, review of design, test) 기반으로 상세설계 (CDR; critical design review) 이후 하위시스템 공장수락시험 (FAT; factory acceptance test)부터 현장수락시험 (SAT; site acceptance test) 그리고 시스템 통합 검증 시험 (TRR; test readiness review) 까지 수행하였다. FAT 단계의 활동은 개발된 장비를 테스트 플랫폼에 설치하고 각 장비별 인터페이스 검증과 통합운영국(KCS; kass control station)과의 연동시험을 통해 성능을 검증하였다. SAT 단계의 활동은 FAT 단계에서 검증된 KRS (kass reference station), KPS (kass processing station), KUS (kass uplink station), KCS를 운영 현장에 설치하고 검증하는 단계이며 개발 일정 및 여건을 고려하여 3단계로 구분하여 수행하였다. TRR 단계의 활동은 항공위성1호기에서 방송되는 SBAS (satellite based augmentation system) 메시지를 이용하여 SAT을 통해 검증된 장비를 FAT 단계에 수행했던 시험 항목과 추가 시험 항목 검증을 통해 전체 시스템에 대한 성능 검증을 완료하였다.

• 한국입자에어로졸학회지
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• 제13권2호
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• pp.87-95
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• 2017

Radon ($Rn^{222}$) is a radioactive gas and is found at high concentrations underground. Investigations were done in many years specifically on public transportations such as in the subway stations, concourses and platforms for these are located underground areas. This study correlates the $Rn^{222}$ concentrations with the Particulate Matter (PM) concentration for the gas could be attached or trapped inside these particles. It was done on the opening subway tunnel of Miasageori Station going to Mia Station (Line 4) last August 2016. Based on the result, the $Rn^{222}$ were more influenced on the mass ratio (%) of PM present in the air instead of its mass concentration (${\mu}g/m^3$). As the $PM_{10}$ mass ratio increases ($42.32{\pm}1.03%$) during morning rush-hours, radon starts to increase up to $0.97{\pm}0.03pCi/L$. But during the afternoon $Rn^{222}$ concentrations decreased while the composition were stable at $22.96{\pm}3.0%$, $39.04{\pm}0.6%$ and $38.01{\pm}0.3%$ in $PM_1$, $PM_{2.5}$ and $PM_{10}$ respectively. It was then assumed that it could be the composition of the morning hours of the station were influencing the concentration of the radon.

• Journal of Radiation Protection and Research
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• 제47권2호
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• pp.77-85
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• 2022

Background: After the Fukushima Daiichi Nuclear Power Station (FDNPS) accident, a model was developed to estimate the external exposure doses for residents who were expected to return to their homes after evacuation orders were lifted. However, the model's accuracy and uncertainties in parameters used to estimate external doses have not been evaluated. Materials and Methods: The model estimates effective doses based on the integrated ambient dose equivalent (H^*(10)) and life patterns, considering a dose reduction factor to estimate the indoor H^*(10) and a conversion factor from H^*(10) to the effective dose. Because personal dose equivalent (H_p(10)) has been reported to agree well with the effective dose after the FDNPS accident, this study validates the model's accuracy by comparing the estimated effective doses with H_p(10). The H_p(10) and life pattern data were collected for 36 adult participants who lived or worked near the FDNPS in 2019. Results and Discussion: The estimated effective doses correlated significantly with H_p(10); however, the estimated effective doses were lower than H_p(10) for indoor sites. A comparison with the measured indoor H^*(10) showed that the estimated indoor H^*(10) was not underestimated. However, the H_p(10) to H^*(10) ratio indoors, which corresponds to the practical conversion factor from H^*(10) to the effective dose, was significantly larger than the same ratio outdoors, meaning that the conversion factor of 0.6 is not appropriate for indoors due to the changes in irradiation geometry and gamma spectra. This could have led to a lower effective dose than H_p(10). Conclusion: The estimated effective doses correlated significantly with H_p(10), demonstrating the model's applicability for effective dose estimation. However, the lower value of the effective dose indoors could be because the conversion factor did not reflect the actual environment.