• Journal of radiological science and technology
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• v.40 no.4
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• pp.549-556
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• 2017

This study compared the spatial scattered dose distribution according to whether the recently developed radiation shielding is used or not in order to understand the spatial scattered dose distribution of C-arm. The horizontal side distribution increased by $30^{\circ}$ in the interval of the radius 50 cm on the height of 95 cm based on the head of the patient, and it was measured by increasing $30^{\circ}$ with the interval of 50 cm in the vertical side of each horizontal side. In the same method, the radiation shielding was installed and measured. The result of measurement shows that the horizontal side of 50 cm distance was $0^{\circ}$, $90^{\circ}$ and $180^{\circ}$, was $1.77{\pm}0.12$, $1.90{\pm}0.13$, $2.12{\pm}0.14$, and $2.69{\pm}0.15mSv/h$ in the $270^{\circ}$ direction, and was $1.59{\pm}0.12$, $0.99{\pm}0.09$, $1.47{\pm}0.11$, and $1.37{\pm}0.11mSv/h$ after the use of the radiation shielding. In addition, the vertical distribution in horizontal direction $90^{\circ}$ with 50 cm distance was $30^{\circ}$, $60^{\circ}$, $120^{\circ}$, was $3.85{\pm}0.18$, $9.15{\pm}0.28$, $10.82{\pm}0.31$, and $5.40{\pm}0.22mSv/h$ in $150^{\circ}$, and was $2.03{\pm}0.13$, $4.32{\pm}0.19$, $2.76{\pm}0.16$, and $1.92{\pm}0.13mSv/h\;mR/h$ after the use of the radiation shielding. Both direction showed decrease according to the use of the radiation shielding. Therefore, radiation related workers who work in operating rooms should recognize the spatial scattered dose distribution exactly and need to try to prevent the risk of radiation exposure with proper protective measures.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.123.1-123.1
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• 2010

수평형 지중열교환기의 최적설계를 위해서는 되메움재의 광물특성 및 입자크기, 열전도도(thermal conductivity), 열용량(heat capacity)등과 같은 열적 특성을 파악 하는 것은 중요하다. 수평형 지중 열교환기용 되메움재의 열전도도를 파악하기 위해 비정상 열선법을 적용한 QTM-500을 사용하여 포화도에 따른 천연규사-물-공기 혼합물의 열전도도를 측정하였다. 측정된 열전도도를 개별요소법(Discrete Element Mothod)에 근거한 2차원 수치해석 프로그램인 PFC2D(Particle Flow Code in 2 Dimension)를 이용하여 비교 분석하였다. 수치해석에서는 혼합물의 건조밀도를 일정하게 유지한 상태에서 포화도에 따라 가상의 물 입자 개수를 변화시켰다. 개별요소법을 이용한 열전달 수치해석에서는 입자의 접촉을 통해 발생한 thermal pipe에 의해 열전달이 이루어진다. 이러한 thermal pipe의 열전도도는 접촉된 두 입자의 열전도도와 접촉면의 평균 열전도도를 고려하여 적용하였다.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.194-201
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• 2005

도시에서의 빛의 연출은 도시의 축을 부각시키고, 가로의 아이덴티티를 연출함으로서 도시의 인지도를 향상시킬 수 있다. 또한 야간의 경관은 인공조명을 이용한 빛의 연출로 주간과는 다른 빛환경 경관을 연출할 수 있다. 이에 본 연구는 도시 가로 중에서 상업가로와 주거가로를 대상으로 주 야간의 빛환경 특성을 분석하여, 가로의 용도에 따른 주야간의 빛환경 차이를 고찰하였다. 이를 위하여 두 가로의 일정길이에 대하여 수평면조도, 스칼라 조도, 휘도 및 색온도를 측정하였으며 측정결과를 용도별, 주 야별로 비교하여 분석하였다. 측정한 결과를 정리하면 다음과 같다. (1)수평면조도의 측정 결과, 주간의 주거가로에 비하여 상업가로가 28.8[%] 높게 나타났으며 야간의 경우 87.2[%] 높게 나타났다. (2) 스칼라조도의 측정결과, 스칼라조도의 특성상 전반적으로 균일한 분포를 보이며, 수평면 조도와 마찬가지로 주간에 비하여 야간에 84[%] 높은 값이 측정되었다. (3) 휘도의 측정 결과, 주간 배경에 대한 대상의 휘도비는 상업과 주거가로가 1:2이하로 나타나 조화로운 가로경관을 연출하며, 야간배경에 대한 대상의 휘도비는 상업가로는 1:17로 활기 있는 경관을 연출하고 주거가로는 1:5로 가로경관 이미지에 적당한 강조효과가 나타났다. (4) 색온도의 측정 결과, 주간의 배경은 맑은 하늘의 색온도를 나타냈으며 대상은 상쾌하고 활동적인 이미지의 색온도를 나타내었다. 또한 야간의 경우 상업가로와 주거가로 모두 나트륨 등의 영향을 받아 전반적으로 따뜻한 느낌의 색온도가 연출되었다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.2 no.2
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• pp.32-40
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• 2000

This paper presents the results of a parametric study on the behavior of tunnel face reinforced with horizontal pipes. A series of reduced-scale model tests was carried out to in an attempt to verify previously performed three-dimensional numerical modeling and to investigate effects of reinforcement layout on the tunnel face deformation behavior. The results of model tests indicate that the tunnel face deformation can significantly reduced by pre-reinforcing the tunnel face with longitudinal members and thus enhancing the tunnel stability. In addition, the model tests results compare fairly well with those from the previously performed three-dimensional finite element analysis. Therefore, a properly calibrated three dimensional model may effectively be used in the study of tunnel face reinforcing technique.

• Journal of the Korean Geotechnical Society
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• v.28 no.4
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• pp.35-42
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• 2012

This paper evaluates the effect of anisotropic conductivity on the seepage face and reliability index of an homogeneous dam with and without toe drain. The analysis are conducted under steady state saturated-unsaturated seepage condition using finite element method. Various anisotropic conductivity ratios were interpreted under such conditions as the vertical conductivity is reduced while the horizon conductivity is fixed. The shear strength of soil is defined by the modified Mohr-Coulomb failure criterion. The analysis results demonstrate that the length of seepage face and reliability index at the downstream and upstream of the dam increase with an increasing anisotropic ratio. These results of the seepage face and reliability index, however, depend on the total head difference between the upstream slope and downstream toe. The difference in seepage face and reliability index is attributed to the different equipotential head with different anisotropic ratios of the dam material.

• The Journal of the Acoustical Society of Korea
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• v.35 no.6
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• pp.419-426
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• 2016

Measurements of bottom loss as a function of grazing angle (in range of $9{\sim}14^{\circ}$) at a frequency range of 4 ~ 8 kHz were conducted on an experimental site off Geoje island in October 2015. Geoacoustic inversion of the surficial sediment thickness is performed using the arrival time difference between the surficial layer and the sub-bottom layer reflected signal. To invert the thickness of surficial sediment, we used the grain size of $8{\sim}10{\phi}$ obtained by KIGAM (Korea Institute of Geoscience and Mineral Resources). The thickness of the surficial sediment was estimated to be 4 ~ 7 m. Finally, this inversion result was compared with the geoacoustic observation conducted by the KIOST (Korea Institute of Ocean Science & Technology) using sub-bottom profiler.

• Tunnel and Underground Space
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• v.23 no.3
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• pp.228-240
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• 2013

Anisotropy observed in sedimentary rock such as sandstone is mainly caused by existence of bedding consequently influencing on its hydraulic characteristics. The aim of this study is to investigate the influence of locally changing pore structure due to bedding on the hydraulic anisotropy of sandstone, in terms of localized porosity. X-ray CT scan is applied to observe the internal pore structures which is hard to be seen by other experimental methods. Permeability test is also conducted for samples cored at every $15^{\circ}$ from $0^{\circ}$ to $90^{\circ}$ with respect to bedding plane. As a result, the permeability anisotropy is manifest having 1.8 of anisotropy ratio ($k_{90^{\circ}}/k_{0^{\circ}}$) and corresponds with the anisotropy of porosity due to bedding.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5C
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• pp.255-262
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• 2008

In order to investigate the strength anisotropy of compacted materials, a series of unsaturated and saturated-drained triaxial compression tests was performed. Three different orientation angles of the axial direction of samples with respect to the horizontal plane were investigated: ${\delta}=0$, 45 and 90 degrees. As the results showed, the suction rate on the strength of the unsaturated specimen was not influenced by ${\delta}$. And the effect of the angle ${\delta}$ on the strength was more pronounced on unsaturated specimen as compared to saturated specimen. Moreover, a new procedure was proposed to take into account the effect of the angle ${\delta}$ on the shear strength of unsaturated soils.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.31 no.4 s.54
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• pp.289-293
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• 2005

Nowadays there are many sun protection cosmetics including organic or inorganic UV filter as an active ingredient. Chemically stable inorganic sunsEreen agents, usually metal oxides, we widely employed in high SPF products. Titanium dioxide is one of the most frequently used inorganic UV filters. It has been used as pigments for a long period of cosmetic history. With the development of micronization techniques, it becomes possible to incorporate titanium dioxide in sunscreen formulations without whitening effect and it becomes an important research topic. However, there are very few works related to quantitations of titanium dioxide in sunscreen products. In this research, we analyzed amounts of titanium dioxide in sunscreen cosmetics by adapting redof titration, reduction of Ti(IV) to Ti(III) and reoxidation to Ti(IV). After calcification of other organic ingredients of cosmetics, titanium dioxide is dissolved by hot sulfuric acid. The dissolved Ti(IV) is reduced to the Ti(III) by adding aluminum metals. The reduced Ti(III) is titrated against a standard oxidizing agent, Fe(III) (ammonium iron(III) sulfate), with potassium thiocyanate as an indicator In order to test accuracy and applicability of the proposed method, we analyzed the amounts of titanium dioxide in four types of sunscreen cosmetics, such as cream, make-up base, foundation and powder, after adding known amounts of titanium dioxide $(1{\sim}25w/w%)$. The percent recoveries of the titanium dioxide in four types of formulations were in the range between 96 and 105%. We also analyzed 7 commercial cosmetic products labeled titanium dioxide as an ingredient and compared the results with those of obtained from ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry), one of the most powerful atomic analysis techniques. The results showed that the titrated amounts were well coincided with the analyzed amounts of titanium dioxide by ICP-AES. Although instrumental analytical methods, ICP-MS (Inductively Coupled Plasma-Mass Spectrometry) and ICP-AES, are the best for the analysis of titanium, it is hard to adopt because of their high prices for small cosmetic companies. It was found that the volumetric method presented here gat e quantitative and reliable results with routine lab-wares and chemicals.

• The Journal of the Acoustical Society of Korea
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• v.20 no.4
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• pp.81-86
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• 2001

126-kHz bistatic sea surface scattering measurements were conducted in the shallow waters off the east coasts of Korea. The range from source to receiver was altered to change the scattering angle at the grazing angles of 38％ and 52％ . Unlike bottom scattering signal, the arrival time and the amplitude of sea surface scattering signals were varied due to the fluctuation of sea surface. The measured forward scattering strengths were compared to model predictions of Kirchhoff approximation and small slope approximation. In overall, the tendency of the scattering strengths showed reasonable agreement among the experimental data, Kirchhoff approximation, and small slope approximation.