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Health effects of exposure to radon: implications of the radon bed mattress incident in Korea
서송원,Wi-Ho Ha,강진규,이달님,박수진,권태은,진영우 한국역학회 2019 Epidemiology and Health Vol.41 No.-
Radon is a naturally occurring radioactive material formed by the slow decay of uranium and thorium found in the earth’s crust or construction materials. Internal exposure to radon accounts for about half of the natural background radiation dose to which humans are exposed annually. Radon is a carcinogen and is the second leading cause of lung cancer following smoking. An association between radon and lung cancer has been consistently reported in epidemiological studies on mine workers and the general population with indoor radon exposure. However, associations have not been clearly established between radon and other diseases, such as leukemia and thyroid cancer. Radiation doses are assessed by applying specific dose conversion coefficients according to the source (e.g., radon or thoron) and form of exposure (e.g., internal or external). However, regardless of the source or form of exposure, the effects of a given estimated dose on human health are identical, assuming that individuals have the same sensitivity to radiation. Recently, radiation exceeding the annual dose limit of the general population (1 mSv/yr) was detected in bed mattresses produced by D company due to the use of a monazite-based anion powder containing uranium and thorium. This has sparked concerns about the health hazards for mattress users caused by radiation exposure. In light of this event, this study presents scientific information about the assessment of radon and thoron exposure and its human implications for human health, which have emerged as a recent topic of interest and debate in society.
SPH에서 임의 형상의 강체면에 대한 탄소성 접촉 해석
서송원(Songwon Seo),이재훈(Jaehoon Lee),민옥기(Oakkey Min) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
There is few research about contact problem for a rigid surface with an arbitrary shape in SPH. The variational equation based on the virtual work principle is derived and its solution is obtained by the penalty method. It is proposed a new method that can determine the parameters for a penetration and a penetration rate used in the penalty method. The reproducing condition is adopted to correct the deficiency of kernel on the boundary. In order to calculate a penetration of particles, after checking boundary particles for deformable body boundary normal vectors were determined on the rigid surface. Numerical simulations for models which have rigid surface with an arbitrary shape were conducted to validate the proposed method in 2D. The results of those analysis represent that the contact algorithm proposed in this study works properly.
서송원(Seo Songwon),민옥기(Min Oakkey) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
There is few research about contact problem in SPH because it is primarily suitable to analyze the large deformation problem. However, an elasto-plastic problem with small deformation need to be considered about contact characteristics. The numerical formulating methods for SPH is induced to be able to abtain solutions based on a varitional method in contact problem. The contact algorithm presented is applied to the elastic impact problem in ID and 2D. The results show that an imaginary tension and a numercal instability which happen in inpacting between different materials can be removed and contact forces which could not have been calculated are able to obtain.
서송원(Songwon Seo),민옥기(Oakkey Min) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.9
SPH is an appealing and valuable computational tool using no background mesh, especially for high deformation events such as impact. But, although research has widely done since invented in 1977, this method still have several problems-lacking consistency, tensile instability and especially boundary condition treatment. This paper review current works for the method of imposing boundary conditions and test several model to certify a validity of its methods. It is compared a method using a ghost particle with that using a boundary condition about a symmetric model. Numerical tests are shown a reasonable result when impose a traction or velocity constraint to the models by equations of boundary constraint condition.
Radon and Lung Cancer: Disease Burden and High-risk Populations in Korea
진영우,서송원 대한의학회 2018 Journal of Korean medical science Vol.33 No.29
Radon, a well-known human carcinogen, is a radioactive gas naturally occurring from uranium and thorium in the ground. Among the 34 known radioactive isotopes of radon, 222 Rn and 220 Rn (thoron) were found at significant concentrations in the human environment with half-lives of 3.82 days and 55.6 seconds, respectively. Thus, outside air typically contains very low levels of radon; however, when contained in a closed environment, it builds up to higher concentrations. In Korea, a local company has reportedly sold beds with radioactive materials, which is a monazite containing radon and thoron, in an anion powder formed inside the mattress covers, emitting radiation above the dose limit of 1 mSv/year for the public; consequently, health concerns from people who have used these mattresses are becoming a social issue. Lung cancer is the most evident health effect from radon exposure, and radon is stipulated as the second leading cause of lung cancer, after smoking by the World Health Organization.1 Radon can spontaneously decay or change to other atoms, called radon progeny (or daughter), which are electrically charged and can attach to tiny dust particles in the air. When the dust particles are inhaled, they can adhere to the epithelia of the lungs. The deposited atoms decay or change by emitting alpha radiation (alpha particles), which can potentially damage cells or DNA in the lungs. Because the alpha radiation travels only short distances (a few centimeters) and is not able to penetrate human skin, it cannot reach any other organs, which resulted in the lung cancer as the only potentially important cancer hazard posed by radon. Although some studies indicated that radon exposure was associated with diseases other than lung cancer such as leukemia and skin cancer, these findings were not consistent with other studies and lacked biological feasibility.
Failure mechanism for metal cylinder under explosive loading
노동환,서송원,이재근,Minki Jang,윤정환 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.9
This paper presents the numerical study of dynamic fracture for metal cylinder under internal explosive loading. Also, the effects of fracture models and groove designs on fracture behavior are investigated. For the dynamic hardening behavior, the Lim-Huh model including the thermal softening effect is adopted [1, 2]. Also, the Lou-Huh fracture model considering the strain rate dependency is used for fracture prediction [3]. The tensile fracture occurs first at the outer surface, and the shear fracture is observed near the inner surface. In addition, finite element analyses are performed to study the effect of various groove designs on dynamic fracture; single U-groove and V-groove at the outer surface. The tensile and shear fracture lines are predicted near the groove tip and inner surface, respectively. It is concluded that the stress triaxiality parameter is one of the critical factors in the dynamic fracture prediction of the metal cylinder.