• The Journal of Korean Society for Radiation Therapy
• /
• v.10 no.1
• /
• pp.60-68
• /
• 1998

Treatment of a large diseased area with electron often requires the use of two or more adjoining fields. In such cases, not only electron beam divergence and lateral scattering but also fields overlapping and separation may lead to significant dose inhomogeneities(${\pm}20\%$) at the field junction area. In this study, we made Acrylic Electron Wedges to improve dose homogeneities(${\pm}5\%$) in these junction areas and considered application it to clinical practices. All measurements were made using 6, 9, 12, 16, 20MeV Electron beams from a linear accelerator for a $10{\times}10cm$ field at 100cm SSD. Adding a 1 mm sheet of acryl gradually from 1 mm to 15 mm, We acquired central axis depth dose beam profile and isodose curves in water phantom. As a result, for all energies, the practical range was reduced by approximately the same distance as the thickness of the acryl insert, e.g. a 1 mm thick acryl insert reduce the practical range by approximately 1 mm. For every mm thickness of acryl inserted, the beam energy was reduced by approximately 0.2MeV. These effects were almost independent of beam energy and field size. The use of Acrylic Electron Wedges produced a small increase $(less\;than\;3\%)\;in\;the\;surface\;dose\;and\;a\;small\;Increase(less\;than\;1\%)$ in X-ray contamination. For acryl inserts, thickness of 3 mm or greater, the penumbra width increased nearly linear for all energies and isodose curves near the beam edge were nearly parallel with the incident beam direction, and penumbra width was $35\;mm{\sim}40\;mm$. We decide heel thickness and angle of the wedge at this point. These data provide the information necessary to design Acrylic Electron Wedge which can be use to improve dose uniformity at electron field junctions and it will be effectively applicated in clinical practices.

• Korean Journal of Heritage: History & Science
• /
• v.43 no.1
• /
• pp.236-259
• /
• 2010

The examination of sediment distribution in Seongryu Cave shows existence of rocks contrasting with Joseon Supergroup contrary to existing knowledge. Contrasting especially with the Taeback Group, Daegi Formation, Hwajeol Formation, and Dongjeom Formation has been observed. Unlike Taeback area where Dumugol Formation and Makgol Formation are observed on top of Dongjeom Formation, the rocks of this area are not clear in its separation between the two, so that it was named Geunnam Formation. Seongryu Cave has been developed in this Ordovician Geunnam Formation of the Joseon Supergroup. The cave, mostly horizontal, runs in the NE-SW direction, and contains three lakes. The main passage and branches are about 330 m and 540 m, respectively, making the total length of the cave about 870 m (show cave area = 270 m). Through underwater examination, about 85 m-long underwater passage was newly discovered. Various speleothem such as soda straw, stalactite, stalagmite, column, flowstone, rimston, cave shield, cave coral, curtain, bacon sheet, cave pearl, cave flower, helictite and calcite raft can be found in the cave. There are sections with constant flow of cavern water, but the majority of cavern water in the cave come from the ceiling. The most important discovery in this study is the presence of various speleothem in the submerged part of cave passages. Traces of corrosion and/or erosion can be observed in the speleothem in the submerge passage.

• Resources Recycling
• /
• v.32 no.3
• /
• pp.57-67
• /
• 2023

The treatment of waste plastic has primarily been entrusted to small companies, which has resulted in challenges in obtaining an accurate overview of the current state of affairs and ensuring profitability. Consequently, despite the presence of recycling technology, their practical application has proven to be challenging. In this study, as part of the waste plastic material recycling plan, it is assumed that the PET/OPP laminated waste film is peeled off at the waste film generation site for the second use. The recycling rate of PET/OPP delaminated waste film is assumed to be 2%, 10%, and 30% referring to the figures suggested by "Life-cycle Post Plastic Measures" from the Korean government. In this study, a physical separation method was developed as a recycling approach for waste PET. A result of cost-benefit analysis was conducted to evaluate the economic viability of the recycling process based on changes in the recycling rate. The findings indicated that a recycling rate of waste PET was 30% or higher resulted in a cost-benefit ratio (Benefit-cost ratio, BCR) of 1.32, exceeding the threshold of BCR ≥1, which is considered to meet the minimum requirement for cost-benefit balance. As the government's allocation ratio and unit price are expected to increase in the future, the cost-benefit ratio is expected to increase further. This case is expected to serve as a pilot initiative for waste PET recycling and foster profit creation for businesses in similar industries.