• 한국터널지하공간학회 논문집
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• 제8권1호
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• pp.31-40
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• 2006

최근 부각되고 있는 환경친화적인 설계의 결과로서 터널 입출구의 구조물이 연약한 지반(붕적층) 에 불가피하게 건설 되곤 한다. 그런 터널 공사의 경우, 주변 지반뿐만 아니라 라이닝 지보재의 충분한 지지력을 확보해야 한다. 이와 관련하여, 높은 강성을 갖는 H형 강지보재가 라이닝을 지지하기 위해 흔히 사용되었다. 그러나 수치해석에 의한 구조적인 안정성을 평가하는데 있어서 그 효과는 무시되는 젓이 관례였다. 본 연구에서는 붕적층에 적용된 터널에 대하여 강지보재로 사용된 H형강을 수치해석 모델에서 강성 적용을 0%, 50%, 75%, 100%로 반영하여 3차원 유한요소해석을 수행하였고, 각 강성 적용율에 따른 숏크리트 용력 감소효과를 비교 검토하였다. 수치해석으로부터 얻어진 데이터는 현장계측결과와 비교하였다, 연구 결과로부터 강지보재의 숏크리트에 대한 효과가 검증되었고 적절한 강성률은 50~75%의 범위 내에서 적절한 것으로 판단되었다.

• Computers and Concrete
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• 제20권5호
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• pp.539-544
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• 2017

Shear walls have high stiffness and strength; however, they lack energy dissipation and repairability. In this study, an innovative slotted shear wall featuring vertical slots and steel energy dissipation connectors was developed. The ductility and energy dissipation of the shear wall were improved, while sufficient bearing capacity and structural stiffness were retained. Furthermore, the slotted shear wall does not support vertical forces, and thus it does not have to be arranged continuously along the height of the structure, leading to a much free arrangement of the shear wall. A frame-slotted shear wall structure that combines the conventional frame structure and the innovative shear wall was developed. To investigate the ductility and hysteretic behavior of the slotted shear wall, finite element models of two walls with different steel connectors were built, and pushover and quasi-static analyses were conducted. Numerical analysis results indicated that the deformability and energy dissipation were guaranteed only if the steel connectors yielded before plastic hinges in the wall limbs were formed. Finally, a modified D-value method was proposed to estimate the bearing capacity and stiffness of the slotted shear wall. In this method, the wall limbs are analogous to columns and the connectors are analogous to beams. Results obtained from the modified D-value method were compared with those obtained from the finite element analysis. It was found that the internal force and stiffness estimated with the modified D-value method agreed well with those obtained from the finite element analysis.

• 대한토목학회논문집
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• 제35권2호
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• pp.377-386
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• 2015

헬리컬 파일은 한 개 이상의 나선형 원판을 중공형 강재 축에 부착한 후 지반에 회전 관입시켜 지지력을 발현하게 하는 말뚝기초의 한 종류로서 별도로 천공작업 및 그라우팅을 필요로 하지 않고, 시공의 편의성과 말뚝 항타 등에 의한 소음이 없다는 장점이 있어 그 이용이 점차 증가되고 있는 추세이다. 본 연구에서는 Cylindrical shear method로 산정된 헬리컬 파일의 요구 지지력을 최소의 자재비용과 최적의 헬리컬 파일의 형상으로 발현할 수 있도록 하모니서치 알고리즘(Harmony search algorithm)을 적용하여 최적화된 설계법을 제안 하였다. 또한 헬리컬 파일의 최적 설계 결과를 2009 International building code (이하, 2009 IBC)를 참고하여 규격화시킨 설계 결과와 비교 검토하여 두 설계법의 경제성을 분석하였다. 본 논문의 재료비 최소화를 위한 헬리컬 파일 형상의 최적 설계 기법은 헬리컬 파일의 경제성을 향상하여 헬리컬 파일 시장 활성화에 기여할 수 있다.

• 대한지역사회영양학회지
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• 제21권3호
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• pp.265-273
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• 2016

Objectives: This study compared the nutritional status of child-bearing age women between the Democratic People's Republic of Korea (North Korea) and the Republic of Korea (South Korea). Methods: The data presented in the DPRK Final Report of the National Nutrition Survey 2012 was utilized for the nutritional status and food intake of North Korean women. To produce the South Korean women's data comparable to those of North Korean women, the data from the 2012 National Health and Nutrition Survey were analyzed and the data presented in the 2010 Report of the Korean Agency for Technology and Standards were utilized. Results: The prevalence of maternal anemia (blood hemoglobin < 12.0 g/dL) was over 30% in all the age groups of North Korean women and 8.9%, 14.2%, 16.4% in 20-29, 30-39, 40-49 year old South Korean women, respectively. The prevalence of maternal protein-energy malnutrition (Mid-Upper Arm Circumference < 22.5 cm) was 25.2%, 21.4%, 21.8% in 20-29, 30-39, 40-49 year old North Korean women, respectively and less than 10% in all the age groups of South Korean women. Result of dietary diversity comparison showed that North Korean women consumed less food than South Korean women at all food groups: grains, fruits, vegetables, meat, and dairy. Percentage of North Korean women having consumed protein rich foods-meat and fish, eggs or dairy products-were much lower than those of South Korean women. Conclusions: The striking disparity of nutritional status between South and North Korean women indicates that nutrition support for North Korean women is essential in the process of preparation for a unified nation.

• Macromolecular Research
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• 제17권9호
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• pp.672-681
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• 2009

A series of inert and photo-stable Er(III)-encapsulated complexes based on ${\pi}$-extended dendritic anthracene ligands bearing G3-aryl-ether dendron ([G3-AnX]-$CO_2H$), which retain different ${\pi}$-bridging systems, such as single (X= S), double (X= D) and triple (X= T) bonds was designed and synthesized to establish the structure-property relationship. The near infrared emission intensities of Er(III)-encapsulated complexes were enhanced dramatically by increasing the ${\pi}$-conjugated extension of anthracene ligands. The time-resolved luminescence spectra show monoexponential decays with a lifetime of $2.0{\sim}2.4ms$ for $Er^{3+}$ ions in thin films, and calculated intrinsic quantum yields of $Er^{3+}$ ions are in the range of $0.025{\sim}0.03%$. As a result, all Er(III)-encapsulated dendrimer complexes exhibit the near IR emission with the following order: $Er^{3+}-[G3-AnD]_3$(terpy) > $Er^{3+}-[G3-AnS]_3$(terpy) ${\approx}$ $Er^{3+}-[G3-AnT]_3$(terpy), because $Er^{3+}-[G3-AnD]_3$(terpy) has a higher relatively spectral overlap J value and energy transfer efficiency. In addition, the lack of detectable phosphorescence and no significant spectral dependence of the ${\pi}$-extended anthracene moieties on the solvent polarity support energy transfer from their singlet state to the central $Er^{3+}$ ion taking place in $Er^{3+}-[G3-AnX]_3$(terpy).

• 한국임상수의학회지
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• 제29권2호
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• pp.198-201
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• 2012

한달 된 한우 수송아지가 오른쪽 뒷다리 체중부하를 못하는 문제를 가지고 전북동물의료센터에 내원하였다. 방사선검사와 CT 검사 상에서 Salter-Harris III형의 먼쪽 정강뼈 성장판 골절로 진단하였다. 개방골절정복 후 교차핀을 이용하여 고정한 후 임시 외부 골격 고정장치를 이용하여 5주 동안 추가적인 지지를 실시하였다. 수술 5주 후 방사선사진 검사에서 골절된 뼈의 유합이 관찰 되었다. 수술2년 후 과도한 움직임 뒤에 미약한 체중부하 파행이 관찰 되었지만, 거의 정상 수준으로 보행이 가능하였다. 송아지에서 이와 같은 증례는 매우 드물고 교차핀과 추가적인 임시 외부 골격 고정장치를 이용한 골절 정복법은 먼쪽 정강뼈 골절 치료에 유용하게 사용될 거라고 생각 된다.

• 대한기계학회논문집B
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• 제34권3호
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• pp.325-331
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• 2010

3-컵 풍속계는 자동기상측정, 환경 모니터링, 풍력 발전에 필요한 풍속을 측정하기 위해 널리 사용되고 있다. 일반적으로 3-컵 풍속계의 회전부를 지지하는 베어링은 오염물질, 진동 또는 돌풍 등의 여러 요인에 의해 마모되기 쉽고, 이로 인해 풍속에 대한 출력 특성이 장기적으로 변한다. 따라서 3-컵 풍속계를 주기적으로 교정하여 풍속에 대한 출력 특성을 유지 및 관리해야 한다. 본 연구에서는 3-컵 풍속계가 설치된 현장에서 풍속계를 교정 할 목적으로 제트 유동을 이용한 현장용 교정 장치를 제작하였다. 현장용 교정 장치가 3-컵 풍속계를 교정할 수 있는지 확인하기 위해, 현장용 교정 장치의 제트 유동 특성을 측정하였다. 현장용 교정 장치를 가지고 5 종류의 3-컵 풍속계들을 교정하였고, 풍동에서 3-컵 풍속계를 교정한 결과와 비교하였다.

• Structural Engineering and Mechanics
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• 제70권4호
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• pp.381-394
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• 2019

If an alternative path would not be considered for redistribution of loads, local failure in structures will be followed by a progressive collapse. When a vertical load-bearing element of a steel structure fails, the beams connected to it will lose their support. Accordingly, an increase in span's length adds to the internal forces in beams. The mentioned increasing load in beams leads to amplifying the moments there, and likewise in their corresponding connections. Since it is not possible to reinforce all the elements of the structure against this phenomenon, it seems rational to use other technics like specified strengthened connections. In this study, a novel connection is suggested to handle the stated phenomenon which is introduced as a passive connection. This connection enables the structure to tolerate the added loads after failing of the vertical element. To that end, two experimental models were constructed and thereafter tested in half-scale, one-story, double-bay, and bolted connections in three-dimensional spaces. This experimental study has been conducted to compare the ductility and strength of a frame that has ordinary rigid connections with a frame containing a novel passive connection. At last, parametric studies have been implemented to optimize the dimensions of the passive connection. Results show that the load-bearing capacity of the frame increased up to 75 percent. Also, a significant decrease in the displacement of the node wherein the column is removed was observed compared to the ordinary moment resisting frame with the same loads.

• 한국기계가공학회지
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• 제20권3호
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• pp.92-99
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• 2021

An automatic transmission, which consists of several decks of planetary gear sets, provides multiple speed and torque ratios by actuating brakes and clutches (mechanical friction components) for connecting central members of the planetary gear sets. The gear set consists of the sun gear, the ring gear, and the carrier supporting multiple planet gears with pin shafts. In designing a new automatic transmission, there are many steps to design and analyze: gears, brakes and clutches, shafts, and other mechanical components. Among them, selecting thrust bearings that not only allow the relative rotation of the central members and other mechanical components but also support axial forces coming from them is important; doing so yields superior driving performance and better fuel efficiency. In selecting thrust bearings, the magnitude of axial forces on them is a critical factor that affects their bearing size and performance; its results are systematically related to the direction of the helical angle of each planetary gear set (a geometric design profile). This research presents the effects of the helical angle direction on the axial forces acting on thrust bearings in an automatic transmission consisting of planetary gear sets. A model transmission was built by analyzing kinematics and power flows and by designing planetary gear sets. The results of the axial forces on thrust bearings were analyzed for all combinations of helix angle directions of the planetary gear sets.

• 대한토목학회논문집
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• 제28권6C호
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• pp.331-338
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• 2008

기존 쏘일네일사면 설계법들은 보강재, 주변지반 또는 이들의 상호작용에 대하여 각기 다른 가정들을 적용하고 있다. 다수의 방법에서는 단순하게 쏘일네일의 인장력만을 고려하여 이를 외력으로 적용하여 안정해석을 하고 있다. 하지만 쏘일네일사면은 사면을 구성하는 지반에 비하여 상대적으로 큰 휨저항성을 가지므로 쏘일네일의 휨강성을 고려한 안정해석법이 보다 현실적이고 공학적인 설계이다. 본 논문에서는 쏘일네일사면 설계시 쏘일네일의 휨저항성을 고려하며 이때 지반의 극한수평지지력에 따른 변화를 확인하고 이를 이용하여 수정된 FHWA 쏘일네일사면 설계법을 제안한다.