• ALGAE
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• 제32권3호
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• pp.199-222
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• 2017

Occurrence of Cochlodinium polykrikoides red tides have resulted in considerable economic losses in the aquaculture industry in many countries, and thus predicting the process of C. polykrikoides red tides is a critical step toward minimizing those losses. Models predicting red tide dynamics define mortality due to predation as one of the most important parameters. To investigate the roles of heterotrophic protists in red tide dynamics in the South Sea of Korea, the abundances of heterotrophic dinoflagellates (HTDs), tintinnid ciliates (TCs), and naked ciliates (NCs) were measured over one- or two-week intervals from May to Nov 2014. In addition, the grazing impacts of dominant heterotrophic protists on each red tide species were estimated by combining field data on red tide species abundances and dominant heterotrophic protist grazers with data obtained from the literature concerning ingestion rates of the grazers on red tide species. The abundances of HTDs, TCs, and NCs over the course of this study were high during or after red tides, with maximum abundances of 82, 49, and $35cells\;mL^{-1}$, respectively. In general, the dominant heterotrophic protists differed when different species caused red tides. The HTDs Polykrikos spp. and NCs were abundant during or after C. polykrikoides red tides. The mean and maximum calculated grazing coefficients of Polykrikos spp. and NCs on populations of co-occurring C. polykrikoides were $1.63d^{-1}$ and $12.92d^{-1}$, respectively. Moreover, during or after red tides dominated by the phototrophic dinoflagellates Prorocentrum donghaiense, Ceratium furca, and Alexandrium fraterculus, which formed serial red tides prior to the occurrence of C. polykrikoides red tides, the HTDs Gyrodinium spp., Polykrikos spp., and Gyrodinium spp., respectively were abundant. The maximum calculated grazing coefficients attributable to dominant heterotrophic protists on co-occurring P. donghaiense, C. furca, and A. fraterculus were 13.12, 4.13, and $2.00d^{-1}$, respectively. Thus, heterotrophic protists may sometimes have considerable potential grazing impacts on populations of these four red tide species in the study area.

• 한국지반환경공학회 논문집
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• 제13권5호
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• pp.25-33
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• 2012

본 연구에서는 흙막이 가시설 공법중 지반의 변위를 억제하고, 토공사 및 구조물 공사의 시공성을 크게 개선한 IPS 흙막이 가시설 공법을 시공한 현장의 계측자료를 바탕으로, 탄소성보법 수치해석 프로그램(EXCAV/W)을 이용하여 수치해석을 실시하였다. 그 결과, 선행하중을 가한 해석치가 평균 13.2% 감소하였으며, 또한 일반적인 해석치보다 현장 계측치는 평균 26.7% 감소하는 것으로 나타났다. 따라서 IPS 흙막이 가시설 공법은 기존 버팀보 공법에 흙막이벽의 수평변위에 대한 안전성을 확보하고 있음을 알 수 있다. 또한 IPS 흙막이 가시설 공법을 이용한 선행하중 효과를 통해 수평변위가 감소하는 것을 확인할 수 있다.

• 한국환경과학회지
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• 제25권2호
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• pp.247-257
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• 2016

To predict annual energy production (AEP) accurately in the wind farm where located in Seongsan, Jeju Island, Equivalent wind speed (EQ) which can consider vertical wind shear well than Hub height wind speed (HB) is calculated. AEP is produced by CFD model WindSim from National wind resource map. EQ shows a tendency to be underestimated about 2.7% (0.21 m/s) than HB. The difference becomes to be large at nighttime when wind shear is large. EQ can be also affected by atmospheric stability so that is classified by wind shear exponent (${\alpha}$). AEP is increased by 11% when atmosphere becomes to be stabilized (${\alpha}$ > 0.2) than it is convective (${\alpha}$ < 0.1). However, it is found that extreme wind shear (${\alpha}$ > 0.3) is hazardous for power generation. This results represent that AEP calculated by EQ can provide improved accuracy to short-term wind power forecast and wind resource assessment.

• 대기
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• 제17권3호
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• pp.231-240
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• 2007

The flow regimes of continuously stratified flow over a double mountain and the effects of a double mountain on wave breaking, upstream blocking, and severe downslope windstorms are investigated using a mesoscale numerical model (ARPS). According to the occurrence or non-occurrence of wave breaking and upstream blocking, three different flow regimes are identified over a double mountain. Higher critical Froude numbers are required for wave breaking and upstream blocking initiation for a double mountain than for an isolated mountain. This means that the nonlinearity and blocking effect for a double mountain is larger than that for an isolated mountain. As the separation distance between two mountains decreases, the degree of flow nonlinearity increases, while the blocking effect decreases. A rapid increase of the surface horizontal velocity downwind of each mountain near the critical mountain height for wave breaking initiation indicates that severe downslope windstorms are enhanced by wave breaking. For the flow with wave breaking, the numerically calculated surface drag is much larger than theoretically calculated one because the region with the maximum negative perturbation pressure moves from the top to the downwind slope of each mountain as the internal jump propagating downwind occurs.

• 한국지진공학회논문집
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• 제18권6호
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• pp.301-308
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• 2014

A suspension bridge is a type of bridge in which the beam is suspended by load-bearing cables. There are two classifications: the self-anchored suspension bridge has the main cable anchored to the bridge girders, and the earth-anchored suspension bridge has the main cable anchored to a large anchorage. Although a suspension bridge is structurally safe, it is prone to be damaged by various actions such as hurricanes, tsunamis and terrorist incidents because its cables are exposed. If damage to a cable eventually leads to the cable rupture, the bridge may collapse. To avoid these accidents, studies on the dynamic behavior of cable bridges due to the cable rupture have been carried out. Design codes specify that the calculated DAF (dynamic amplification factor) should not exceed a certain value. However, it has been difficult to determine DAFs effectively from dynamic analysis, and thus no systematic approach has been suggested. The current study provides a guideline to determine DAFs reliably from the dynamic analysis results and summarizes the results by applying the method to an earth-anchored suspension bridge. In the study, DAFs were calculated at the location of four structural parts, girders, pylons, main cable and hangers, with variations in the rupture time.

• 천문학논총
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• 제13권1호
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• pp.135-147
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• 1998

We have simulated the interaction of supernova remnants with constant ambient medium to explore the dynamics of Type Ia supernova remnant. We assumed the supernova ejecta density distribution of the central constant and the outer power-law density distribution$({\rho}{\propto}{\gamma}^{-n})$. We have calculated four different cases with different n. By scaling the length and time scales from the initial parameters-ejecta mass, ejecta energy, the ambient density, we could compare effects of the different density distribution of the ejecta on the dynamics of the SNRs. The radius of the outer forward shock converges the Sedov-Talyor solution at t' = 2.3 when the swept-up mass is 8 times of the ejecta mass. On the other hand, the motion of the reverse shock are largely affected by n. The ejecta with smaller n takes comparably long time to thermalize the whole ejecta at $t'{\simeq}5.3,\;M_{sw}{\simeq}18M_{ej}$. We have applied our calculated results to obtain the ejecta density distributions of Tycho and SN1006 with $n{\simeq}6$.

• 자원환경지질
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• 제24권1호
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• pp.63-69
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• 1991

Gravity study was carried out to investigate the structure and total mass of the Bupyeong silver deposits closely related to formation of the Bupyeong caldera. Survey region covers $3.3{\times}6.6km^2$ over silver deposits and is comprised of 334 gravity measurement stations. An apparent regional gravity trend parallel to the west coast line is mainly attributed to isostasy. A least square isostasy model was used for the regional correction. A Fortan subroutine was coded to calculate 3-dimensional subsurface model. The calculated gravity values from the 3-dimensional model of the caldera with silver deposits agree with observed anomalies relatively well. Gravity anomaly due to Bupyeong silver deposits reaches to +3.5 mgal from the background value and anomaly due to the caldera reaches to -4 mgal. But the maximum negative anomaly of the caldera would be much greater at its center. The total mass of silver deposits calculated from the subsurface model is $4.19{\times}10^9$ tons. Although the economic part of silver deposits depends on the grade of orebody, we expect that there are still large amount of silver reserves in Bupyeong area.

• Nuclear Engineering and Technology
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• 제36권1호
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• pp.1-11
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• 2004

Two approximate methods for a cosmic radiation shielding calculation in low earth orbits were developed and assessed. Those are a sectoring method and a chord-length distribution method. In order to simulate a change in cosmic radiation environments along the satellite mission trajectory, IGRF model and AP(E)-8 model were used. When the approximate methods were applied, the geometrical model of satellite structure was approximated as one-dimensional slabs, and a pre-calculated dose-depth conversion function was introduced to simplify the dose calculation process. Verification was performed with mission data of KITSAT-1 and the calculated results were also compared with detailed 3-dimensional calculation results using Monte Carlo calculation. Dose results from the approximate methods were conservatively higher than Monte Carlo results, but were lower than experimental data in total dose rate. Differences between calculation and experimental data seem to come from the AP-8 model, for which it is reported that fluxes of proton are underestimated. We confirmed that the developed approximate method can be applied to commercial satellite shielding calculations. It is also found that commercial products of semi-conductors can be damaged due to total ionizing dose under LEO radiation environment. An intensive shielding analysis should be taken into account when commercial devices are used.

• 전기전자학회논문지
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• 제23권1호
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• pp.318-321
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• 2019

겉보기대지저항률은 층의 깊이와 대지저항률과 같은 다층 대지파라미터들을 추정하는 데 사용된다. 겉보기대지저항률은 측정 될 수 있으며, 또한 겉보기대지저항률은 이들 파라미터들의 함수이기 때문에 주어진 대지 파라미터들로 계산 될 수 있다. 따라서 모든 최적화 알고리즘을 사용하여 계산된 겉보기대지저항률을 측정된 대지저항률에 가깝게 만드는 이들 파라미터들을 찾을 수 있다. 겉보기대지저항률을 계산하기위한 방정식은 0 차 Bessel함수를 포함하는 무한 적분으로 구성되어 있기 때문에 복잡하고 시간 소모적이다. 본 논문에서는 수평 다층 구조의 겉보기대지저항률을 계산하기 위한 빠른 알고리즘이 복소수이미지 방법을 사용하여 제시되었다.

• 한국도로학회논문집
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• 제10권1호
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• pp.41-48
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• 2008

이 논문은 가파른 경사면 전면에 시공되는 낙석방지벽에 작용하는 토압의 특성에 대한 내용을 다룬다. 낙석방지벽 배면되메움 공간은 주동상태의 흙쐐기가 완전히 형성될 만큼의 공간이 없고, 토압의 특성은 벽체의 이동과 벽체와 절취사면 사이의 좁은 간격에서 발생하는 아칭 효과의 영향을 크게 받기 때문에 해석적으로 신뢰성 있는 규명이 되지 않고 있다. 연구는 실내에서 축소모형에 대한 원심력시험을 통하여 수행되었다. 연구결과는 낙석방지공 배면토압이 지반의 경사각과 벽체이동에 크게 영향 받음을 보여주었다 벽체상반부에서는 벽체이동에 의한 토압감소가. 하반부에서는 아칭 효과가 뚜렷하게 나타남을 보였다. 이 연구결과에 의하면 낙석방지벽 설계에서 벽체에 작용하는 토압은 지반경사와 공사중 또는 완공후의 벽체 이동조건을 고려하여야 함을 알 수 있었다.