• Radiation Oncology Journal
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• v.16 no.3
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• pp.337-345
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• 1998

Purpose : To obtain the uniform dose at limited depth to entire surface of the body, the dose characteristics of degraded electron beam of the large target-skin distance and the dose distribution of the six-dual electron fields were investigated Materials and Method : The experimental dose distributions included the depth dose curve, spatial dose and attenuated electron beam were determined with 300 cm of target-skin distance (TSD) and full collimator size (35*35 $cm^2$ on TSD 100 cm) in 4 MeV electron beam energy. Actual collimated field size of 105 cm * 105 cm at the distance of 300 cm could include entire hemibody. A patient was standing on step board with hands up and holding the pole to stabilize his/her positions for the six-dual fields technique. As a scatter-degrader, 0.5 cm of acrylic plate was inserted at 20 cm from the body surface on the electron beam path to induce ray scattering and to increase the skin dose. Results : The full width at half maximum(FWHM) of dose profile was 130 cm in large field of 105*105 $cm^2$ The width of $100\pm10\%$ of the resultant dose from two adjacent fields which were separated at 25 cm from field edge for obtaining the dose unifomity was extended to 186 cm. The depth of maximum dose lies at 5 mm and the 80$\%$ depth dose lies between 7 and 8 mm for the degraded electron beam by using the 0.5 cm thickness of acrylic absorber. Total skin electron beam irradiation (TSEBI) was carried out using the six dual fields has been developed at Stanford University. The dose distribution in TSEBI showed relatively uniform around the flat region of skin except the protruding and deeply curvatured portion of the body, which showed excess of dose at the former and less dose at the latter. Conclusion : The percent depth dose, profile curves and superimposed dose distribution were investigated using the degraded electron beam through the beam absorber. The dose distribution obtained by experiments of TSEBI showed within$\pm10\%$ difference except the protruding area of skin which needs a shield and deeply curvatured region of skin which needs boosting dose.

• Journal of the Korean earth science society
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• v.38 no.1
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• pp.24-34
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• 2017

The westerly waves generation is described in the advanced earth science textbook used at high school as follows: as westerly wind approaches and blows over large mountains, the air flow shows wave motions in downwind side, which can be explained by the conservation of potential vorticity. However, there has been no case study showing the phenomena of the mesoscale westerly waves with observational data in the area of small mountains in Korea. And thus the wind speed and time persistency of westerly winds along with the width and length of mountains have never been studied to explain the generation of the westerly waves. As a first step, we assured the westerly waves generated in the downwind side of Sobaek mountains based on surface station wind data nearby. Furthermore, the critical or minimum wind velocity of the westerly wind over Sobaek mountains to generate the downwind wave were derived and calcuated tobe about $0.6m\;s^{-1}$ for Sobaek mountains, which means that the westerly waves could be generated in most cases of westerly blowing over the mountains. Using surface station data and 4-dimensional assimilation data of RDAPS (Regional Data Assimilation and Prediction System) provided by Korea Meteorological Agency, we also analyzed cases of westerly waves occurrence and life cycle in the downwind side of Sobaek mountains for a year of 2014. The westerly waves occurred in meso-${\beta}$ or -${\gamma}$ scales. The westerly waves generated by the mountains disappeared gradually with wind speed decreasing. The occurrence frequency of the vorticity with meso-${\beta}$ scale got to be higher when the stronger westerly wind blew. When we extended the spatial range of the analysis, phenomena of westerly waves were also observed in the downwind side of Yensan mountains in Northeastern China. Our current work will be a study material to help students understand the atmospheric phenomena perturbed by mountains.