• 한국환경과학회지
• /
• 제4권2호
• /
• pp.245-251
• /
• 1995

Generally, It is Introduced to well-known other models without considering tidal current of the field. The paper presents field measurements and numerical model solving velocity field of Cheonsu Bay by two-dimensional tidal model. It was proved that this scheme is easy to handle complex topography. Computed results is represented characteristics of tidal current for Cheonsu Bay. The results of the study can be summarized as follows ; 1. Tide form number has 0.21 value. Tidal range estimated 630.3 cm on spring, 454.1 cm on mean and 277.9 cm on neap, respectively 2. Tidal current has semi-diurnal form. Distance of traveling observed 16.6 km on flood and 15.5 km on ebb. 3. Tidal velocity showed reversing current. It was found that tidal velocity above 100 cm/sec is about 20 %. 4. Computed results are in good agreement with the observed data. Applying the algorithm to Cheonsu Bay, velocity fields and dry bank phenomena are simulated well in spite of complex topography. 5. An advanced study on the effects of open boundary conditions should be continuously performed.

• Ocean and Polar Research
• /
• 제42권3호
• /
• pp.211-223
• /
• 2020

With the increasing demand for improved marine environments and safety, greater ability to minimize damages to coastal areas from harmful organisms, ship accidents, oil spills, etc. is required. In this regard, an accurate assessment and understanding of current systems is a crucial step to improve forecasting ability. In this study, we examine spatial and temporal characteristics of current systems in the adjacent seas of Jeju Island using a high-resolution regional ocean circulation model. Our model successfully captures the features of tides and tidal currents observed around Jeju Island. The tide form number calculated from the model result ranges between 0.3 and 0.45 in the adjacent seas of Jeju Island, indicating that the dominant type of tides is a combination of diurnal and semidiurnal, but predominantly semidiurnal. The spatial pattern of tidal current ellipses show that the tidal currents oscillate in a northwest-southeast direction and the rotating direction is clockwise in the adjacent seas of Jeju Island and counterclockwise in the Jeju Strait. Compared to the mean kinetic energy, the contribution of tidal current energy prevails the most parts of the region, but largely decreases in the eastern seas of Jeju Island where the Tsushima Warm Current is dominant. In addition, a Lagrangian particle-tracking experiment conducted suggests that particle trajectories in tidal currents flowing along the coast may differ substantially from the mean current direction. Thus, improving our understanding of tidal currents is essential to forecast the transport of marine pollution and harmful organisms in the adjacent seas of Jeju Island.

• 한국해안·해양공학회논문집
• /
• 제27권3호
• /
• pp.149-158
• /
• 2015

경기만 한강하구에서 주요 수로의 조석 전파 특성을 이용하여, 천문조, 배조 및 복합조의 분포를 파악하고, 조석 형태수의 특징에 따라 구역별 조석체계 (tidal regime)를 분류하였다. 주요 수로에서 보이는 조석 전파 특성은 외해는 천문조로 대표되는 5대분조 (e.g., $M_2$, $S_2$, $N_2$, $K_1$ 및 $O_1$)가 지배적이지만, 상류로 진입할수록 천해 분조 (e.g., $M_4$)와 장주기 분조 (e.g., $MS_f$)의 뚜렷한 증가가 보인다. 반일주조 성분이 우세한 경기만 및 한강하구에서 천문조, 배조 및 복합조를 이용하여 제시된 조석 형태수 (tidal form number)의 특성에 따라 크게 3구역으로 분류하였다. 1구역은 천문조가 우세한 지역으로 외해에서 인천항 전면까지 (염하수로), 외해에서 석모수로의 북쪽 입구로 제시된다. 2구역은 염하수로 남쪽 입구에서 북쪽 입구까지와 강화 북수로 지역으로 단주기 천해 분조 (e.g., $M_4$와 $MS_4$)가 강하게 나타나는 지역이다. 마지막으로 3구역은 신곡 수중보 이후부터 한강 상류지역으로 장주기 복합조 (e.g., $MS_f$)가 제일 우세한 지역이다. 일반적인 하구와 마찬가지로 한강하구의 조석 비선형성은 지형적 특성에 기인한 천해 분조가 증가를 하며, 1/4일주기 (fourth-diurnal) 및 장주기 (long-term period) 분조의 확연한 분포 차이를 보인다. 특히, 수중보의 영향은 구조물의 상류와 하류지점의 조석체계에 지대한 변화를 일으킨다.

• Ocean Science Journal
• /
• 제42권1호
• /
• pp.19-30
• /
• 2007

This study analyzed the current meter records along with wind records for over 500 days obtained in the Kangjin Bay, South Sea, Korea spanning from March, 2003 to Nov. 2005. Various analyses include descriptive statistics, harmonic analysis of tidal constituents, spectra and coherence, the principal axis, progressive vector diagrams. These analyses can illustrate the response of residual current to the local wind resulting in the net drift with rotational motion. Current speed ranges from -28 to 33 (cm/sec), with standard deviations from 6.5 to 12.9 (cm/sec). The harmonic analyses of the tidal current show the average form number, 0.12 with semi-diurnal type and the rectilinear orientation of the major axis toward northeast. The magnitudes of the semi-major range from 12.7 to 17.7 (cm/sec) for M2 harmonics, while for S2 harmonics, they range from 6.3 to 10.4 (cm/sec), respectively. In the spectral and coherency analysis of residual current and wind, a periodicity of 13.6 (day) is found to be most important in both records and plays an important role in the net drift of residual current. The progressive vector diagrams of residual current and wind show two types of behaviors such as unidirectional drift and rotational motion. It was also found that 3 % rule holds approximately to drive 1 (cm/sec) drift current by 30 (cm/sec) wind speed based on the correlation of the semi-major axis of wind and residual current.

• 한국어류학회지
• /
• 제10권2호
• /
• pp.241-249
• /
• 1998

1986년 6월에서 1987년 3월 사이 영광 연안에서 소형 otter trawl를 이용하여 계절별로 저어류를 채집하여 종조성 변화를 분석하였다. 총 33종의 어류가 채집되었으며, 그 가운데 민태(Johnius grypotus), 쉬쉬망둑(Chaeturichthys stigmatias), 보구치(Argyrosomus argentatus)와 참서대(Cynoglossus joyneri)가 우점하여, 이 4종이 총 채집개체수의 81.9%, 총생체량의 71.4%를 차지하였다. 출현종수와 채집량은 온수기에 높았고, 이 시기에는 주거종인 참서대와 회유중인 보구치와 민태가 우점하였다. 냉수기에는 출현종수도 적었고, 쉬쉬망둑과 등가시치(Zoarces gillii)가 우점하였다. 본 연구 주요 우점종의 상대빈도는 1995년의 자료와 유사한 계절변동을 보였다. 한반도 서남 연안 천해역의 저어류 자료와 비교한 결과, 민태와 쉬쉬망둑의 상대빈도는 조류가 빨라짐에 따라 감소하였으나, 참서대는 증가하였다. 이러한 중감 경향은 참서대의 체형이 민태나 쉬쉬망둑에 비하여 바닥에 접촉할 수 있는 면이 넓어 조류가 강한 연안역에서 우점할 수 있는 것으로 추정된다.

• 천문학회보
• /
• 제45권1호
• /
• pp.34.1-34.1
• /
• 2020

The recent discovery of diffuse dwarf galaxies that are deficient in dark matter appears to challenge the current paradigm of structure formation in our Universe. We describe the numerical experiments to determine if the so-called dark matter deficient galaxies (DMDGs) could be produced when two gas-rich, dwarf-sized galaxies collide with a high relative velocity of ~ 300km/s. Using idealized high-resolution simulations with both mesh-based and particle-based gravito-hydrodynamics codes, we find that DMDGs can form as high-velocity galaxy collisions separate dark matter from the warm disk gas which subsequently is compressed by shock and tidal interaction to form stars. Then using a large simulated universe ILLUSTRISTNG, we discover a number of high-velocity galaxy collision events in which DMDGs are expected to form. However, we did not find evidence that these types of collisions actually produced DMDGs in the ILLUSTRISTNG100-1 run. We argue that the resolution of the numerical experiment is critical to realize the "collision-induced" DMDG formation scenario. Our results demonstrate one of many routes in which galaxies could form with unconventional dark matter fractions.

• 천문학회보
• /
• 제38권2호
• /
• pp.76-76
• /
• 2013

The current hierarchical model of galaxy formation predicts that galaxy halos contain merger relics in the form of long stellar streams. In order to find stellar substructures in galaxy, we focused our investigation on the stellar spatial density around globular clusters and on the quantitative properties of the evolved sequences in the color-magnitude diagrams (CMDs). First, we investigated the spatial configuration of stars around five metal-poor globular clusters in halo region (M15, M30, M53, NGC 5053, and NGC 5466) and one metal-poor globular cluster in bulge region (NGC 6626). Our findings indicate that all of these globular clusters show strong evidence of extratidal features in the form of extended tidal tails around the clusters. The orientations of the extratidal features show the signatures of tidal tails tracing the clusters' orbits and the effects of dynamical interactions with the galaxy. These features were also confirmed by the radial surface density profiles and azimuthal number density profiles. Our results suggest that these six globular clusters are potentially associated with the satellite galaxies merged into the Milky Way. Second, we derived the morphological parameters of the red giant branch (RGB) from the near-infrared CMDs of 12 metal-poor globular clusters in the Galactic bulge. The photometric RGB shape indices such as colors at fixed magnitudes, magnitudes at fixed colors, and the RGB slope were measured for each cluster. The magnitudes of the RGB bump and tip were also estimated. The derived RGB parameters were used to examine the overall behavior of the RGB morphology as a function of cluster metallicity. The behavior of the RGB shape parameters was also compared with the previous observational calibration relation and theoretical predictions of the Yonsei-Yale isochrones. Our results of studies for stellar spatial distribution around globular clusters and the morphological properties of RGB stars in globular clusters could add further observational evidence of merging scenario of galaxy formation.

• 한국어류학회지
• /
• 제36권1호
• /
• pp.1-9
• /
• 2024

이 연구는 남해안 여자만에 서식하는 짱뚱어의 초기생활사를 규명하고 그 결과를 같은 망둑어과 어류들과 차이점을 비교하였다. 연구에 사용된 어미는 2015년 6월 전남 벌교읍 갯벌에서 맨손으로 포획하였다. 산란량은 411~11,688개였고, 난은 짧은 타원형으로 크기는 1.40×0.72 mm였다. 수온 25~27℃에서 부화시간은 91시간 35분이 소요되었다. 부화 직후 난황자어는 전장 3.02~3.31 (평균 3.17±0.08, n=30) mm로 난황을 갖고 있었고, 먹이 섭취는 하지 않았다. 부화 후 4일째에는 전장 3.31~3.52(평균 3.43±0.07, n=30) mm로 입과 항문이 열리면서 전기자 어기로 이행하였고, 먹이를 섭취하였다. 부화 후 14일째 전장 5.06~5.25 (평균 5.16±0.06, n=30) mm로 척추 말단 끝부분이 45°로 완전히 휘어지면서 후기자어기로 이행하였다. 부화 후 41일째 전장 14.3~16.8 (평균 15.4±0.85 mm, n=30)로 각 지느러미 기조수는 제1등지느러미 5개, 제2등지느러미 26~27개, 뒷지느러미 24~27개, 배지느러미 6개로 정수에 달하면서 치어기로 이행하였다. 연구 결과 후기자어는 별 모양의 흑색소포가 가슴지느러미 앞쪽부터 꼬리지느러미 기저까지 침착되어 있어 다른 망둑어과 어류 후기자어들과 형태적인 차이가 구분되었다.