• Journal of The Geomorphological Association of Korea
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• v.18 no.2
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• pp.1-14
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• 2011

Remarkable development of sand bars is an important characteristic of fluviatile landform of Korea. Their development owes, in one part, to the supply of abundant sandy materials to river valley floor, originated from the weathering of essentially granitic rocks, distributed almost all over the country. It owes, in other part, to river valley disposition presenting many angular sinuosity guided by fracture grid, impeding regular migration of sandy materials along valley floor. Besides, high amplitude of river discharge fluctuation of the country plays is proved to be favorable hydrological factor for the development of the sand bars. The sand bars play important roles in favor of river hydro-ecological environment. They mitigate the amplitude of discharge fluctuation regime. In flood spell, sand grains in the main channel migrate so as to broden wet section. At the spell of low water level, they newly accumulate as to impede rapid stream discharge. Especially high quantity of reserved water in porous space of sand bar is preciously available both for human livelihood and for ecological environment.

• Journal of radiological science and technology
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• v.38 no.3
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• pp.221-228
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• 2015

Purpose: In digital mammography QC program was used for the purpose of reducing low-dose and high-definition images of the radiation dose. Materials and Methods: In digital mammography using a QC phantom according to the average glandular dose in the exposure method MLO view $0^{\circ}C$, $30^{\circ}C$, $45^{\circ}C$, $50^{\circ}C$, $55^{\circ}C$, $70^{\circ}C$, was measured at $90^{\circ}C$ intervals, an image with Hologic QC program to the SNR and CNR was measured to evaluate. Results: The average dose in the MLO view was wired to $90^{\circ}C$ when the maximum was 1.75 mGy, it decreased approximately 6% was measured at $45^{\circ}C$ 1.65 mGy. In addition, 1.67 mGy, manual record, there were an average wired in accordance with the exposure dose and the dose of 1.52 mGy difference in the way auto filter. Image quality evaluation at every angular section SNR 50 ~ 52, shows a slight difference in CNR 11 ~ 12, it was included in the manufacturer's recommended value. Conclusion: The dose was lowest in MLO view $45^{\circ}C$, the difference between SNR and CNR were insignificant. The method of exposure will need a way to reduce the exposure of the patient's body or unnecessary patient by placing a difference in settings in which the characteristics.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.14 no.4
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• pp.269-275
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• 1981

The fishing hooks were tested for breaking and unbending due to plastic deformation of the material. Study of tensile test is not complicated, but has not even worked out fully enough, especially when the test specimen is subjected to plastic deformation. The fishing hook is subjected to unbending stress and the critical section is a Point which is furthest from the line of action of the forces. The dynamic force of fish during jerks depends on their speed of movement and body weight, the kinetic energy corresponding to it and also on the rlastic displacement of the rigging which absorb the energy. Six kinds of hook were tested by the dynamometer under tensile speed 290mm/min (subscript s) and 780mm/min (subscript f). According to their results, the breaking load(B: kg) can be induced with the formula $B={\alpha}wd^2+\beta$ where w(mm) is the distance between the barb base and the lower shank and d(mm) is diameter. The coefficients of the formula for the round hooks(R) and the angular hooks(A) are approximately as follows: $$R:\;\alpha_{s}=0.5,\;\beta_{s}=1.6,\;\alpha_{f}=0.4,\;\beta_{f}=1.4$$ $$A:\;\alpha_{s}=1.1,\;\beta_{s}=2.0,\;\alpha_{f}=1.0,\;\beta_{f}=0.9$$ The ratio of $B_{f}\;to\;B_{s}$ is corresponding to 0.8. The ratio of deformation(X) that is moved distance of barb base at break to the distance(H) between head base and barb base is about $50\%$. Further study should be carried out on the subject of impact and fatigue test under the same condition which is exerted force by the hooked fish.