• 천문학회보
• /
• 제44권1호
• /
• pp.44.4-44.4
• /
• 2019

The supernova remnant Cassiopeia A (Cas A) provides a unique opportunity to observe the fine details of the explosion of core-collapse supernova (SN). Previous optical and near-infrared (NIR) observations of Cas A have shown that the spatial distribution of the metal-enriched SN ejecta is very complicated, indicating that the SN explosion should have been asymmetric and turbulent, especially near the core. Recently, we obtained a long-exposure (~10 hr) image of Cas A by using the UKIRT 3.6-m telescope with a narrow-band filter centered at [Fe II] 1.644 um emission. This 'deep [Fe II] image' provides an unprecedented panoramic view of Cas A, revealing the distribution of dense SN ejecta over the entire remnant. We have carried out NIR multi-object spectroscopic observations of the dense ejecta knots in the northeastern (NE) and eastern (E) outer regions of the remnant using the MMIRS attached on the MMT 6.5-m telescope. A total of 67 ejecta knots are detected. By analyzing their spectra, we have found that the knots in the NE area show strong [S II]/[S III] and [Fe II] lines but little or no [P II] line, while those in the E outer region show strong [Fe II] lines but weak [S II]/[S III] lines. In this talk, we present the preliminary results of our NIR spectroscopic observations and discuss the implications.

• 한국농공학회논문집
• /
• 제61권1호
• /
• pp.75-83
• /
• 2019

Fruit bagging is a traditional way to produce high-quality fruit and to prevent damage from insects and diseases. Growing pears by non-bagging is concerned about the damage from insect, it can be controlled by installing a insect net facility. Wind load should be considered to design the insect net facility because it has the risk of collapse due to the strong wind. So we carried out wind tunnel test for measurement of drag force, where the insect net with porosity about 65% is selected as an experimental subject. As a result of the test, drag force was measured to be 244.14 N when insect net area and wind speed are $1m^2$ and 22.7 m/s respectively. And, drag coefficients for the insect net were found to be about 0.55~0.57, which may be used as the preliminary data to design the insect net facilities at the orchard.

• Geomechanics and Engineering
• /
• 제28권1호
• /
• pp.1-10
• /
• 2022

In Korea, accidents related to the collapse of deteriorated aging reservoirs occur every year. The grouting method is generally applied to reinforce an aging reservoir. However, when using this method, different reinforcing effects appear depending on the ground conditions. Thus, new construction methods and materials capable of providing consistent reinforcing effects are required. In this study, the direct shear test (DST), model test, and simulation analysis were performed to evaluate the impact of surface stabilizers, generally used to reinforce roads, rivers, and slopes of roads, applied using surface curtain walls on aging reservoirs. The DST results indicate that when the surface stabilizer was mixed with in-situ soil, the increase in cohesion was the highest at a mixing ratio of 9%. No changes in the friction angle were evident; therefore, 9% was determined to be the optimal mixing ratio. In addition, the model test and simulation analysis showed that when 9% of the surface stabilizer was mixed and applied to the aging reservoir, the seepage quantity of water and the saturated area were reduced by approximately 42% and 73%, respectively. Moreover, the comprehensive analysis of results showed that the grouting method could be completely replaced by surface stabilizers applied through surface curtain walls because the technique could secure stability by decreasing the seepage in the aging reservoir.

• 국제학술발표논문집
• /
• The 1th International Conference on Construction Engineering and Project Management
• /
• pp.952-955
• /
• 2005

In the early 90's, we had serious shortage of construction engineers in Korea. The shortage was acute especially in construction quality control and supervision area, which were gaining social attention due to the road bridge and the department store collapse that took the hundreds of lives in the early 90's in Seoul, Korea. In order to meet the high demand of construction engineers, the engineering license regulations were changed in 1995. Engineers who did not pass the written exam but have equivalent working experience are given engineering license to practice engineering legally. Since year 2000, while the severe engineer-shortage has been resolved, the opposite situation has occurred: there is serious over-supply of construction engineers. Policy makers and engineering practitioners are agreed to bring back the old-fashioned written exam engineer licensing system like before 1995, i.e., no more written exam exemption. However, the engineers who obtained license without taking written exam may not want to go back to old policy which would take their license. It is required to provide appropriate grace period before the new policy takes effect to minimize the impact of the changes. This paper forecasts the supply-demand of construction engineers providing the basis for the most appropriate policy changes.

• Korean Journal of Radiology
• /
• 제1권1호
• /
• pp.33-37
• /
• 2000

Objective: To describe the radiologic findings of migrating lobar atelectasis of the right lung. Materials and Methods: Chest radiographs (n = 6) and CT scans (n = 5) of six patients with migrating lobar atelectasis of the right lung were analyzed retrospectively. The underlying diseases associated with lobar atelectasis were bronchogenic carcinoma (n = 4), bronchial tuberculosis (n = 1), and tracheobronchial amyloidosis (n = 1). Results: Atelectasis involved the right upper lobe (RUL) (n = 3) and both the RUL and right middle lobe (RML) (n = 3). On supine anteroposterior radiographs (n = 5) and on an erect posteroanterior radiograph (n = 1), the atelectatic lobe(s) occupied the right upper lung zone, with a wedge shape abutting onto the right mediastinal border. On erect posteroanterior radiographs (n = 6), the heavy atelectatic lobe(s) migrated downward, forming a peri- or infrahilar area of increased opacity and obscuring the right cardiac margin. Erect lateral radiographs (n = 4) showed inferior shift of the anterosuperiorly located atelectatic lobe(s) to the anteroinferior portion of the hemithorax. Conclusion: Atelectatic lobe(s) can move within the hemithorax according to changes in a patient s position. This process involves the RUL or both the RUL and RML.

• Geomechanics and Engineering
• /
• 제36권3호
• /
• pp.247-258
• /
• 2024

Tailings are waste materials of mining operations, consisting of a mixture of clay, silt, sand with a high content of unrecoverable metals, process water, and chemical reagents. They are usually discharged as slurry into the storage area retained by dams or earth embankments. Poor knowledge of the hydro-mechanical behaviour of tailings has often resulted in a high rate of failures in which static liquefaction has been widely recognized as one of the major causes of dam collapse. Many studies have dealt with the static liquefaction of coarse soils in saturated conditions. This research provides an extension to the case of silty tailings in unsaturated conditions. The static liquefaction resistance was evaluated in terms of stress-strain behavior by means of monotonic triaxial tests. Its dependency on the preparation method, the volumetric water content, the void ratio, and the degree of saturation was studied and compared with literature data. The static liquefaction response was proved to be dependent mainly on the preparation technique and degree of saturation that, in turn, controls the excess of pore pressure whose leading role is investigated by means of the relationship between the -B Skempton parameter and the degree of saturation. A preliminary interpretation of the static liquefaction response of Stava tailings is also provided within the Critical State framework.

• 한국재난정보학회 논문집
• /
• 제20권1호
• /
• pp.147-155
• /
• 2024

연구목적: 본 연구는 재난 안전 사각지대에 있는 소규모의 민간 건축물을 대상으로 건축물의 위험징후를 분석하고 계측기술을 개발하기 위한 건축물 모니터링 시스템 설치 방안을 제시하는 것을 목적으로 한다. 연구방법: 건축물 위험거동의 원인, 모니터링 계측 기기의 구성요소, 계측기기 설치 위치, 관리 방안 등을 제시한다. 연구결과: 계측기기는 필수적으로 가속도센서, 기울기센서, 자이로센서, GPS 등이 포함된다. 계측장치는 기둥의 높이와 단면적을 고려해야 한다. 결론: 본 연구의 결과는 소규모 민간 건축물에서 발생할 수 있는 건축물 붕괴로부터 발생하는 재난을 대비하여 재난 안전 역량 강화를 할 수 있다.

• 대한치과보철학회지
• /
• 제51권4호
• /
• pp.323-331
• /
• 2013

고정성 국소의치를 이용한 수복 시 보철물 자체의 심미성뿐 아니라 보철물과 조화로운 주변 연조직의 형성 또한 중요한 요소이며, 임시보철물을 이용하여 조화로운 연조직의 형태를 형성할 수 있다. 임시보철물을 통해 형성한 연조직의 형태는 적절한 형태를 갖는 최종 수복물을 제작하는데 필요한 정보를 제공할 수 있도록 최종모형으로 정확하게 복제되어야 한다. 그러나, 임시보철물 주위 연조직의 형태는 인상과정 또는 인상재의 압력 등으로 최종 모형으로의 복제가 어렵다. 따라서, 임시보철물을 이용하여 형성한 구강내의 연조직 형태를 모형으로 복제하여 연조직과 조화로운 최종 수복물을 제작하는 서로 다른 2가지 방법을 본 증례보고에서 소개한다.

• 한국건축시공학회지
• /
• 제2권2호
• /
• pp.165-172
• /
• 2002

A reinforced concrete building neighboring in Pusan or Ulsan where is directly exposed to salt water contrasting with other in land areas contains much salt content percolated from the outside that the high salt content percolates and diffuses through the inside of reinforced concrete; therefore, an immovable tunic surrounding it begins to be destroyed and eroded with high speed. At the time, the cross-sectional area and volume expansion of re-bar reinforcing result in being cracks make a rapid progress gradually until they appear in the surface of the one, the phenomenon such as being a thin layer or falling off the part of it causes a lowering of its durability and might collapse the concrete construction. So far, we've investigated into salt content of reinforced concrete constructions neighboring in a seaside district and damage by carbonation, and we came to a conclusion as follows: $\circled1$ Under the oceanic circumstance a concrete construction is influenced by sea water directly that contains much amount of salt content contrasting with other constructions on inland areas. $\circled2$ Because of chloride penetration the carbonation of reinforced concrete made a rapid progress until more than the covering thickness of re-bar. $\circled3$ An old reinforced concrete building which has been piled up salt injury and proceeding the carbonation of its cross-sectional area. $\circled4$ According to rapidly cracking from the inside to surface of reiforced concrete, the phenomenon of being a thin layer or falling off the part of reinforced concrete results in a lowering of durability and shortening the life-time of concrete construction itself.

• 한국산림과학회지
• /
• 제105권4호
• /
• pp.435-440
• /
• 2016

경상남도 하동군 옥종면 청룡리 땅밀림 산사태지의 인장균열 형성과 그에 따른 토양 물리성 변화를 조사한 결과, 주 인장균열과 국부적 인장균열의 단차와 절취경사는 차이가 없는 것으로 나타났다. 토양 물리성 변화의 경우에는 토양깊이 31~40 cm의 액상이 유의적 차이를 나타내었다. 한편, 액상은 미교란지와 교란지에서 유의적 차이가 나타났는데, 이는 입지요인에 의한 것으로 판단되다. 따라서 하동군 옥종면의 땅밀림 산사태지에서는 붕괴과정 중 토괴가 일체로 미끄러지며, 단적으로는 토양 물리성 변화도 크게 나타나지 않는 것으로 나타났다. 이에 따라 땅밀림 산사태에 대한 보다 연계성 있는 연구가 진행되어야 할 것이다.