한강 3개 보 구간 수변부 11개 지점을 대상으로 2023년 총 2회 채집된 저서성 대형무척추동물은 총 100종 평균 426.0 개체/m2였다. 여주보에서 64종으로 가장 많이 출현하였고, 강천보에서 59종, 이포보에서 54종, 한강보상류 에서 41종, 한강보하류에서 32종이 확인되었다. 전체 평균 개체밀도는 강천보에서 944.1 개체/m2로 가장 많았고, 한강보상류에서 282.7 개체/m2, 여주보에서 251.9 개체/m2, 이포보에서 180.6 개체/m2, 한강보하류에서 172.9 개체 /m2 순으로 확인되었다. 한강 보 구간에서는 플라나리아류, 실지렁이, 깔따구류 등이 우점함. 보구간의 특성상 상대적으로 단순한 하상 및 깊은 수심에 적응성이 높은 실지렁이, 깔따구류의 우점은 일반적인 특성으로 볼 수 있으며 일시적으로 수변부에서 밀집된 플라나리아류의 채집이 이뤄져 우점된 결과를 보인 것으로 보임. 한강 보 구간 수변부 및 중앙부 조사지점별 군집분석을 실시한 결과 한강보 하류는 3개 보에 비해 우점도가 높고 다양도 와 풍부도가 낮았으며 전반적으로 상류부에 위치한 한강보상류 등의 지점에서 군집안정성이 확보되고 있는 것으로 보이며 이러한 점은 상대적으로 다양한 미소서식환경에 기인한 것으로 판단된다.

We analyzed the performance of hubless rim propellers based on the number of blades, maintaining a fixed pitch ratio and expanded area ratio, using computational fluid dynamics (CFD). Thrust coefficient, torque coefficient and efficiency according to the number of blades were analyzed. In addition, the pressure distribution on the discharge and suction sides of the blade was analyzed. As the advance ratio increases, the thrust coefficient decreases. The highest thrust was shown when the advance ratio was lowest. For the three, four, five and six-blades, the torque coefficient tended to decrease as the advance ratio increased. In the case of seven and eight-blades, the torque coefficient tended to increase as the advance ratio increased. The maximum efficiency was found when the advance ratio was 0.8. When the three-blade, it showed high efficiency at all advance ratios. A high pressure distribution was observed at the leading edge of the discharge blade, and a low pressure distribution was observed at the trailing edge. Applying a hubless rim-driven thruster with the three-blade can generate higher thrust and increase work efficiency.

H2O maser emission at 22 GHz in the circumstellar envelope is one of the good tracers of detailed physics and kinematics in the mass loss process of asymptotic giant branch stars. Long-term monitoring of an H2O maser spectrum with high time resolution enables us to clarify acceleration processes of the expanding shell in the stellar atmosphere. We monitored the H2O maser emission of the semi-regular variable R Crt with the Kagoshima 6-m telescope, and obtained a large data set of over 180 maser spectra over a period of 1.3 years with an observational span of a few days. Using an automatic peak detection method based on least-squares fitting, we exhaustively detected peaks as significant velocity components with the radial velocity on a 0.1 km s−1 scale. This analysis result shows that the radial velocity of redshifted and blue-shifted components exhibits a change between acceleration and deceleration on the time scale of a few hundred days. These velocity variations are likely to correlate with intensity variations, in particular during flaring state of H2O masers. It seems reasonable to consider that the velocity variation of the maser source is caused by shock propagation in the envelope due to stellar pulsation. However, it is difficult to explain the relationship between the velocity variation and the intensity variation only from shock propagation effects. We found that a time delay of the integrated maser intensity with respect to the optical light curve is about 150 days.

The purpose of this study is to suggest the modification of activities to introduce the nature of science in earth science classrooms. A small modification can turn ordinary textbook activities into the nature of science activities. Since earth science could provide a good basis for the tentative, creative, and socially and culturally embedded nature of science, as well as appropriate understanding about scientific methods, careful modification of earth science activities could be effective for students to understand the nature of science. Considering which aspects of the nature of science are appropriate, along with the possible change in the activity, teachers will be able to modify textbook activities effectively. An example modification of H-R diagram activity was also suggested.

In this review article we introduce the 'H-R diagram' of black holes. Some fundamental concepts of black hole thermodynamics and electrodynamics are also summarized in detail.

최근 유한요소해석에서 보다 정확한 해를 위한 적응해석법에 대해 많은 연구가 이루어지고 있다. 본 논문은 요소 면적당의 오차를 균일화하여 절점을 최적의 위치로 변화시키는 r법과 오차가 큰 요소를 같은 모양의 요소로 세분시키는 h법을 혼합한 rh형 적응해석법을 사용하였다. 그 결과 같은 자유도에서 h법과 rh법의 오차감소율과 수렴속도는 거의 같에 나타났지만, rh법은 h법만 사용했을 때보다 전체 자유도 증가를 최대한 억제한 상태에서 정확한 유한요소해를 얻을 수 있었다.

About two hundred stars within 50 pc from the sun, whose tangential velocity larger than 100 km/sec, have been selected on the basis of their proper motions and trigonometric parallaxes. A list of them along with their photoelectric UBV data and spectral types is given. The criterion on the tangential velocity, v t > 132 km/sec, was adopted for selection of high-velocity stars. The H-R diagram of these nearby high-velocity stars resembles that of a globular cluster, with the turnoff around B − V ≈ 0.35 and M v ≈ 4.0 , and the subdwarfs among these high-velocity stars are fainter than the main-sequence stars of Hyades by the amount of 1 m .25 ± 0 m .30 in the region with B-V < 1.40 on the average.

Changes in temperature and humidity inside a concrete has correlation with movement speed and reaction rate of deterioration factors such as carbon dioxide and chloride ions. comparison was performed between temperature and relative humidity inside the concrete and meteorological data for exposure environment through measurement at the site for two years.

DNA 메틸화 (DNA methylation)는 유전자의 발현을 조절하는 대표적인 후생학적 조절기작 (epigenetic regulation) 중에 하나이다. DNA 메틸화 양상은 생식세포 형성과정 및 배 발생단계에서 탈메틸화 (demethylation)와 de novo 메틸화의 드라마틱한 변화가 일어난다. 또한 이러한 DNA 메틸화는 배아줄기세포 (embryonic stem cells, ESCs)에서 특징적인 양상을 보이는 것으로 알려져 있다. 본 연구에서는 생쥐 수정란 유래 배아줄기세포와 체세포핵이식 배아줄기세포 (nuclear transplanted ESCs)를 이용해서 대표적 각인유전자 (imprinting genes)로 알려진 Snrpn, Igf2r, H19 유전자들에 대한 메틸화 양상을 알아보고자 하였다. 연구 결과 H19 유전자에 대해서는 DNA 메틸화 양상은 수정란 유래 배아줄기세포와 체세포핵이식 배아줄기세포에서 비슷한 경향을 보였으나, Snrpn과 Igf2r의 경우에는 체세포핵이식 배아줄기세포에서 과메틸화 (hypermethylation) 경향을 보였다.