• 한국해양학회지
• /
• 제18권1호
• /
• pp.43-48
• /
• 1983

동계 동해와 황해 표층 수십 메터에서 불안정 성층을 수반한 해양 온도 역전 현상이 종종 발생한다. 수온 역전층 발생의 원인으로서는 (1) 해면으로부터의 열손실을 보상하기 위한 해양 내부의 대류에 기인한 수온 역전, (2) 계절적 수온 변화가 하방으로 전달되면서 진폭과 위상이 바뀜에 따른 동계의 수온 역전, 그리고 (3) 냉수역에서 온수역으로 취송류가 이동함에 따른 수온 역전 등을 들 수 있는 바, 이 논문에서는 위의 세가지 수온 역전 발생 원인에 대하여 해석적인 모델을 제시한다.

• 대한기계학회논문집
• /
• 제17권6호
• /
• pp.1330-1341
• /
• 1993

본 연구에서는 회전대우(revolute joint)들로 이루어진 1자유도 평면기구들의 특성을 파악하고 그래이프이론(graph theory)을 이용하여 기구의 형태를 행렬로 표시 하여 체이터베이스에 저장하였다. 또한 기구의 특성중의 하나인 작업조건(function specification)에 따른 무오차점(precision point)의 최대 개수를 알아내는 프로그램 을 개발하여 이로써 얻은 정보를 또 다른 데이타베이스에 저장하였다. 이와같이 구축 된 데이터베이스들로부터 설계자의 요구에 적합한 기구를 선택하여 형태합성 문제를 해결하였다.

• 대기
• /
• 제22권3호
• /
• pp.321-330
• /
• 2012

Generation mechanisms of the three moderate-or-greater (MOG)-level clear-air turbulence (CAT) encounters over South Korea are investigated using the Weather Research and Forecasting (WRF) model. The cases are selected among the MOG-level CAT events occurred in Korea during 2002-2008 that are categorized into three different generation mechanisms (upper-level front and jet stream, anticyclonic flow, and mountain waves) in the previous study by Min et al. For the case at 0127 UTC 18 Jun 2003, strong vertical wind shear (0.025 $s^{-1}$) generates shearing instabilities below the enhanced upper-level jet core of the maximum wind speed exceeding 50 m $s^{-1}$, and it induces turbulence near the observed CAT event over mid Korea. For the case at 2330 UTC 22 Nov 2006, areas of the inertia instability represented by the negative absolute vorticity are formed in the anticyclonically sheared side of the jet stream, and turbulence is activated near the observed CAT event over southwest of Korea. For the case at 0450 UTC 16 Feb 2003, vertically propagating mountain waves locally trigger shearing instability (Ri < 0.25) near the area where the background Richardson number is sufficiently small (0.25 < Ri < 1), and it induces turbulence near the observed CAT over the Eastern mountainous region of South Korea.

• 한국가시화정보학회지
• /
• 제8권2호
• /
• pp.16-22
• /
• 2010

A flow visualization has been conducted to investigate unsteady flight characteristics of a model of dragonfly. The mechanism of lift generation by flapping wings is analyzed using smoke-wire and high speed camera. The experimental results of flow visualization show a discernible sequential dynamics that three mechanisms and high incidence angle of the wings are responsible for the lift generation. The leading edge vortex by the rapid acceleration of leading edge of the wing during initial stage of stroke causes a strong lift enhancement. Delayed stall during the stroke, fast supination and pronation of the wing near the end of each stroke are also responsible for the lift generation.

• International Journal of Aeronautical and Space Sciences
• /
• 제7권2호
• /
• pp.86-103
• /
• 2006

Using a combination of force transducer measurement to quantify net lift force, high frame rate camera to quantify and subtract inertial contributions, and Digital Particle Image Velocimetry (DPIV) to calculate aerodynamic contributions in the spanwise plane, the contribution of spanwise flow to the generation of lift force in wings undergoing a pure flapping motion in hover is shown as a function of flapping angle throughout the flapping cycle. These experiments were repeated at various flapping frequencies and for various wing planform sizes for flat plate and span wise cambered wings. Despite the previous identification of the importance of span wise fluid structures in the generation of lift force in flapping wings throughout the existing body of literature, the direct contribution of spanwise flow to lift force generated has not previously been quantified. Therefore, in the same manner as commonly applied to investigate the chordwise lift distribution across an airfoil in flapping wings, spanwise flow due to bulk flow and rotational fluid dynamic mechanisms will be investigated to validate the existence of a direct component of the lift force originating from the flapping motion in the spanwise plane instead.

• Journal of Ginseng Research
• /
• 제21권2호
• /
• pp.78-84
• /
• 1997

As a part of our ongoing effort to develop new antineoplastic immunostimulator from natural sources, bioassay-directed fractionationn of polysaccharides from Korean red ginseng was carried out by observing the proliferation of marine spleen cells and the generation of lymphoklne activated killer (LAK) cells. The acidic polysaccharide fractions proliferated spleen cells and generated LAK cells in proportion to their acidity in vitro. The LAK cell which was induced by ginseng showed tumoricidal activity against both NK celt sensitive and insensitive tumor target cells without major histocompatibility (MHC) restriction. Adherent macrophages and CD4+helper T cells were involved in the generation of the LAK cells. The acidic polysaccharide from Korean red ginseng synerglzed with recombinant IL-2 (rIff-2) at lower than 3 U/ml. The optimal doses of the acidic polysaccharide from Korean red ginseng for the proliferation of spleen cells and for the generation of LAK cells were 1 mg/ml and 100 $\mu\textrm{g}$/ml, respectively; this means that the mechanisms for the both activities may be different from each other.

• 전기학회논문지
• /
• 제56권7호
• /
• pp.1205-1210
• /
• 2007

Several mechanisms are introduced for the procurement of capacity adequacy. In the competitive electricity market, however, it is a GENCO that makes generation investment decision. A GENCO will invest a new generator when it can get more profit than cost. There requires a model to evaluate profit with respect to a new generation investment. In the view of long-term investment, evaluation of a profit of a generator in the electricity market is quite different from that of short-term operation. In this paper, a new profit-evaluation model is proposed for the long-term generation investment. It can treat the probabilistic characteristics of generators, ie, forced-outage-rates, which affect profit of generators.

• Molecules and Cells
• /
• 제39권6호
• /
• pp.508-513
• /
• 2016

To investigate the potential therapeutic effects of polyphenols in treating Pb induced renal dysfunction and intoxication and to explore the detailed underlying mechanisms. Wistar rats were divided into four groups: control groups (CT), Pb exposure groups (Pb), Pb plus Polyphenols groups (Pb+PP) and Polyphenols groups (PP). Animals were kept for 60 days and sacrificed for tests of urea, serum blood urea nitrogen (BUN) and creatinine. Histological evaluations were then performed. In vitro studies were performed using primary kidney mesangial cells to reveal detailed mechanisms. Cell counting kit-8 (CCK-8) was used to evaluate cell viability. Pb induced cell apoptosis was measured by flow cytometry. Reactive oxygen species (ROS) generation and scavenging were tested by DCFH-DA. Expression level of tumor necrosis factor-${\alpha}$ (TNF-${\alpha}$), interleukin-1-${\beta}$ (IL-1-${\beta}$) and IL-6 were assayed by ELISA. Western blot and qPCR were used to measure the expression of ERK1/2, JNK1/2 and p38. Polyphenols have obvious protective effects on Pb induced renal dysfunction and intoxication both in vivo and in vitro. Polyphenols reduced Pb concentration and accumulation in kidney. Polyphenols also protected kidney mesangial cells from Pb induced apoptosis. Polyphenols scavenged Pb induced ROS generation and suppressed ROS-mediated ERK/JNK/p38 pathway. Downstream pro-inflammatory cytokines were inhibited in consistency. Polyphenol is protective in Pb induced renal intoxication and inflammatory responses. The underlying mechanisms lie on the antioxidant activity and ROS scavenging activity of polyphenols.

• 한국전기전자재료학회논문지
• /
• 제14권2호
• /
• pp.130-132
• /
• 2001

The mechanisms of pretilt angle generation in nematic liquid crystal (NLC) with negative dielectric anisotropy on a rubbed polyimide (PI) surface for homeotropic alignment were studied. The pretilt angle of negative type NLC was smaller than that of the positive type NLC for all rubbing strength regions on the rubbed PI surface. The pretilt angle generated in NLC does not attributable to steric interaction between the fluorine moiety of NLC and the polymer surface on the rubbed PI surface. Consequently, the mechanism of the pretilt angle generation for homeotropic alignment is different from the one for homogeneous alignment.

• 공학교육연구
• /
• 제13권5호
• /
• pp.3-7
• /
• 2010

As 10th energy consumption country in the world, it is very important to educate the importance of the energy to the elementary school students. The purpose of this class is to let the pupils understand the mechanisms and performances of tidal power generation as a renewable energy application system. To satisfy the educational goals, a lecture material and a simple type of tidal power generator kit is developed. As the survey result after lecture and experiments which include assembly and test, 'Well understood' is marked as 90% among 58 elementary students, and moreover 70% among them feel to participate in higher level course. This project shows the possibility and effect of the renewable energy education course as a service engineering, which is managed and carried out by undergraduates for pupils under the professor's guide.