• Journal of Korean Society of Transportation
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• v.16 no.1
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• pp.111-128
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• 1998

양방향 2차로에서 지체는 교통사고유발이나 운전자에게 심리적부담을 주는 중용한 문제이다. 그 러나 이지체현상중 지체시간산정에 대한 연구는 많지 않다. 본 연구에서는 일반적으로 사용할수 있는 지체시간산정모형(PDEM)을 개발했다. 우선적으로 감가속이 일어나지 않은 곡선부에 적용할 수 있는 모 형을 고려했다. 검증은 기존에 제시되었던 Morrall 모형, TWOPAS모형과 비교하여 개선한 효과를 제시 하는 방법과 모형의 변수들을 변화시킬 때 모형의 값이 합리적으로 변하는지를 살펴보는 민감도분석방 법을 이용했다. 본 연구에서 갤발한 모형에 덧붙여 앞으로 연구해야 할 과제는 감가속과 추월을 고려한 경우의 모형개발과 본 모형에서 계산한 값을 서비스수준지표로 사용하는 방법에 대한 모색이다.

• Korean Journal of Soil Science and Fertilizer
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• v.42 no.1
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• pp.37-45
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• 2009

Susceptibility assessment of groundwater contamination is a useful tool for many aspects of regional and local groundwater resources planning and management. It can be used to direct regulatory, monitoring, educational, and policy-making efforts to highly vulnerable areas. In this study, a semi process-based was proposed to evaluate relative susceptibilities to groundwater contamination by nitrate on a regional scale. Numerical simulation based on data from each soil series was done to model water flow within soil profiles that were related to groundwater contamination by nitrate. Relative vulnerability indices for each soil series were produced by manipulation of amount of leaching flux, amount of average water storage in a soil profile, and amount of average water storage change. These indices were designed to convey the trend of leaching flux and to maximize spatial resolution. The resulting vulnerability distribution map was used to locate highly vulnerable sites easily with an appropriate grouping the indices, and was then compared with those from groundwater nitrate concentrations monitored. An excellent agreement was obtained across nitrate concentrations from the highly vulnerable regions and those from the low to stable regions.

• Journal of Radiation Protection and Research
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• v.33 no.1
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• pp.21-26
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• 2008

When the calibration on Liquid Scintillation Counter using the Solid $^3H$ Standard Source of 200,000DPM is executed, the uncertainty due to activity and geometry difference, exists. Therefore, this paper intends to evaluate environmental samples comparatively accurately as decreasing this uncertainty existing in the process of calibration. For this, measurements on samples manufactured by $^3H$ Standard Source and sensitivity study were performed. Also, this paper verified calibration results using Radioactivity-Error-Analysis Method, and evaluated quantitatively the effect by geometry and activity difference based on verification result. According to the result of sensitivity study, in case of using the exposure time of 75 sec and Repeat method, the measuring accuracy and precision of about $1{\sim}3%$ were increased in comparison with the existing method. By analysis result, the effect by activity difference did not appear, and a plastic cell existing into Teflon vial made a role as reflector. The less the effect of plastic cells are decreased, the more activity is high, and the effect of those can be neglected at the activity of 200,000 DPM.