• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.03a
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• pp.123-128
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• 1998

In fracture problems, stress intensity factors obtained theoretically and experimentally have been effectively utilized in the analytical evaluation of the cracks effect. The effect of surface crack of a cylindrical and a hollow cylindrical bar is investigated, as well as the effect of the thickness of a hollow cylindrical bar and inclined crack of a hollow cylinder subjected to torsion moment. In this study, stress intensity factor Km of mode III which expresses the stress state in the neighborhood of a crack tip is used. Stress analysis was conducted of the inside of a hollow cylinder in the axial direction of three dimensional crack tip subjected to torsion moment by combining the caustics method and the stress freezing method.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.5
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• pp.46-52
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• 1998

In fracture problems, stress intensity factors obtained theoretically and experimentally have been effectively utilized in the analytical evolution of the cracks effect. The effect of surface crack of a cylindrical and a hollow cylindrical bar is investigated, as well as the effect of the thickness of a hollow cylindrical bar and inclined crack of a hollow cylinder subjected to torsion moment. In this study, stress intensity factor Km of mode III which expresses the stress state in the neighborhood of a crack tip is used. stress analysis was conducted on the inside of hollow cylinder inthe axial direction of three dimensional crack tip subjected to torsion moment by combining the caustics method and the stress freezing method.

• Journal of The Korean Astronomical Society
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• v.29 no.1
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• pp.1-8
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• 1996

When we follow the lines of the trajectory of photons which intersect the circle, the circle may suffer some deformation as approaching to the observer. We consider an infinitesimal light bundle suffering gravitational bending. We examine the deformation of the deflected light bundle due to the gravitational lens. The size of the deformation is expressed in terms of the focal length of the gravitational lens.

• Journal of The Korean Astronomical Society
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• v.25 no.2
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• pp.79-90
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• 1992

The physical properties of the flux factor K and its application are discussed in connection to the high amplification events. The effects due to random motions of stars in a foreground galaxy are examined in the frame work of moving caustics of gravitational microlenses.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.7
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• pp.1630-1641
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• 1995

The dynamic stress intensity factors (DSIF ; $K_{I}$$^{dyn}$) were studied in some polymeric materials using caustics method with a high speed camera system. Also crack tip propagation speed was measured by dynamic crack propagation velocity measuring device. To calculate DSIF a finite element analysis program-INha Stress Analysis Moving CRack(INSAMCR) was utilized. Dynamic fracture characteristics were investigated to verify a relationship between DSIF and crack tip propagation speed and acceleration in PMMA, Homalite-100 and Polycarbonate. The relationship between dynamic stress intensity factor and crack tip velocity revealed typical shapes. Measured crack tip acceleration data envelope converges to the zero level with increasing DSIF. Equivalently crack tip velocities show a wide spread range at low values of DSIF, but become a constant with a higher DSIF. $1.2MPa{\sqrt{m}}$, $1.4MPa{\sqrt{m}}$ and $1.3 MPa{\sqrt{m}}$ were obtained as $K_{I}$$^{dyn}$ values to arrest the dynamic crack for PMMA, Homalite-100 and Polycarbonate, respectively. INSAMCR was run to verify experimental results in PMMA and shows good agreementment.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.25-26
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• 1996

In the standard theory of the large scale structure formation, matter accretes onto high density perturbations via gravitational instability. Collision less dark matter forms caustics around such structures, while collisional baryonic matter forms accretion shocks which then halt and heat the infalling gas. Here we discuss the characteristics. roles, and observational consequences of these accretion shocks.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1993.07a
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• pp.26-28
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• 1993

해안구조물의 설치나 해안환경 문제를 다룰때 가장 필수적인 것이 그 지역에서의 정확한 파랑자료이다. 파랑은 천해로 전파해 옴에 따라 수심 및 지형변화로 인한 회절 및 굴절을 겪으면서 변하게 되므로 복잡한 지형을 가진 해안에서의 정확한 파랑계산은 용이한 일이 아니다. 이러한 파랑변형에 대한 연구는 Berkhoff(1972)가 완경사방정식을 발표한 후 큰 진전을 보이게되는데 이로 인해 종래 개별적으로 다루던 굴절과 회절을 함께 취급할 수 있게 되고 파향선이 교차할때 생기는 불합리한 에너지의 집중(caustics)을 해결할 수 있게 되었다. (중략)

• Journal of The Korean Society of Clinical Toxicology
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• v.10 no.2
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• pp.91-96
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• 2012

Purpose: A retrospective study with a literature review was conducted to identify the clinical characteristics and prognosis after the acute ingestion of glacial acetic acid. Methods: The medical records of 20 patients,who had presented to the emergency department of Ajou University Hospital complaining of the acute ingestion of glacial acetic acid between January 2006 and December 2011, were examined retrospectively. Results: Among the 172 patients admitted for caustics injury, 20 patients ingested glacial acetic acid. The mean age of the patients was $55{\pm}23.5$, and the mean volume of the acid was $84.5{\pm}71.3$ ml. The clinical features included 1) oral ulcers in 12 patients (63.2%), 2) respiratory difficulties in 11 patients (57.9%), 3) oliguria in 8 patients (42.1%), 4) renal toxicity in 7 patients (36.8%), 5) hepatic failure in 7 patients (36.8%), 6) disseminated intravascular boagulopathyin 7 patients (36.8%), 7) low blood pressure in 8 patients (42.1%), and 8) mental changes in 9 patients (47.4%). Ten patients required endotracheal intubation. Nine patients were admitted to the intensive care unit, and 5 patients expired. Conclusion: The ingestion of glacial acetic acid can cause severe symptoms, such as metabolic acidosis, multiple organ failure and upper airway swelling frequently and has a high mortality rate. Therefore, aggressive treatment, including endotracheal intubation, should be considered at the early stages.

• Journal of The Korean Astronomical Society
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• v.42 no.3
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• pp.33-37
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• 2009

We propose a diagnostic that can resolve the planet/binary degeneracy of central perturbations in caustic-crossing high-magnification microlensing events. The diagnostic is based on the difference in the morphology of perturbation inside the central caustics induced by a planet and a wide-separation binary companion. We find that the contours of excess exhibit a concentric circular pattern around the caustic center for the binary-lensing case, while the contours are elongated or off-centered for the planetary case. This difference results in the distinctive features of the individual lens populations in the residual of the trough region between the two peaks of the caustic crossings, where the shape of the residual is symmetric for binary lensing while it tends to be asymmetric for planetary lensing. We determine the ranges of the planetary parameters for which the proposed diagnostic can be used. The diagnostic is complementary to previously proposed diagnostics in the sense that it is applicable to caustic-crossing events with small finite-source effect.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.232-235
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• 1999

실제 해양에서 동일 수심과 거리에서 둘 이상의 음선이 교차하여 형성되는 Caustic에서는 고전적인 (classical) 음선모델(ray model)에서 나타나는 무한대의 음압이 아니라 주변지역과 비교하여 다소 높은 정도의 음압을 나타낸다. 하지만 caustic이라 할 지라도 음선들이 도달하는 도달시간차(travel time difference)와 펄스길이(pulse length)의 변화에 따라 음압상승현상의 폭이 달라지며 때로는 음압이 상승이 나타나지 않는 경우도 있다. 본 연구에서는 음선모델을 이용하여 caustic위치를 추정하고 펄스길이를 변화시키면서 신호모의를 실시하였다. 모의결과 caustic은 수렴대(convergence zone) 및 도파관(duct)등 음선이 모이는 곳에 집중되어 나타났고 펄스길이의 면화에 따라 음압이 다르게 나타났다.