• The Journal of the Korea Contents Association
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• v.16 no.7
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• pp.681-688
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• 2016

This study assess their quality of radiation on analysis of the spectrum of resolution suggesting IEC 61267 in radiation quality that RQA3, RQA5, RQA7, RQA9 and combination of clinical condition using several quality of radiation. In experiments edge method first, the spatial resolution assessment used image of the additional filter and SID is obtained the IEC 62220-1, spatial resolution and sharpness of the obtained image was evaluated in the MTF value 10%(0.1), MTF value 50%(0.5) using a Matlab program. Second, MCNPX simulation used spatial resolution analysis was radiation quality particle fluence and spectrum analysis in energy. As a result, make use of additional filter, image quality evaluation of SID that RQA3 radiation quality combination qualification is higher spatial resolution and sharpness make unused of additional filter and SID 100cm. RQA7 radiation quality combination qualification is higher that spatial resolution make unused of additional filter and SID 150cm. RQA9 radiation quality combination qualification is higher that spatial resolution and sharpness make used of additional filter and SID 180cm. spectrum analysis of radiation quality by reducing consequent errors occurring in the experiment that error due to the reproducibility of the X-ray tube, occur in an error of correction the detector suggest ideal conditions from spectrum analysis through MCNPX simulation. In conclusion, by suggesting spatial resolution and sharpness of result for various radiation quality, It provide basic data that radiation quality condition and quantitative assessment method for laboratory in clinical using detector evaluation.

• Journal of the Mineralogical Society of Korea
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• v.28 no.3
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• pp.233-244
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• 2015

In order to study the phase transformation of pyrite and to determine the maximum Fe leaching factors, pyrite samples were an electric furnace and microwave oven and then ammonia leaching was carried out. The rim structure of hematite was observed in the sample exposed in an electric furnace, whereas a rim structure consisting of hematite and pyrrhotite were found in the microwave treated sample. Numerous interconnected cracks were only formed in the microwave treated sample due to the arcing effect, and these cracks were not found in the electric furnace treated sample. Under XRD analysis, pyrite and hematite were observed in the electric furnace treated sample, whereas pyrite, hematite and pyrrhotite were found in the microwave treated sample. The results of the pyrite sample leaching experiments showed that the Fe leaching was maximized with the particle size of -325 mesh, sulfuric acid of 2.0 M, ammonium sulfate of 1.0 M, and hydrogen peroxide of 1.0 M. The electric furnace and microwave treated samples were tested under the maximum leaching conditions, the Fe leaching rate was much greater in the microwave treated sample than in the electric furnace treated sample and the maximum Fe leaching time was also faster in the microwave treated sample than in the electric furnace treated sample. Accordingly, it is expected that the microwave heating can enhance (or improve) Fe leaching in industrial minerals as well as pyrite decomposition in gold ores.

• Journal of Powder Materials
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• v.24 no.6
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• pp.437-443
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• 2017

SiC-based composite materials with light weight, high durability, and high-temperature stability have been actively studied for use in aerospace and defense applications. Moreover, environmental barrier coating (EBC) technologies using oxide-based ceramic materials have been studied to prevent chemical deterioration at a high temperature of $1300^{\circ}C$ or higher. In this study, an ytterbium silicate material, which has recently been actively studied as an environmental barrier coating because of its high-temperature chemical stability, is fabricated on a sintered SiC substrate. $Yb_2O_3$ and $SiO_2$ are used as the raw starting materials to form ytterbium disilicate ($Yb_2Si_2O_7$). Suspension plasma spraying is applied as the coating method. The effect of the mixing method on the particle size and distribution, which affect the coating formation behavior, is investigated using a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) analysis. It is found that the originally designed compounds are not effectively formed because of the refinement and vaporization of the raw material particles, i.e., $SiO_2$, and the formation of a porous coating structure. By changing the coating parameters such as the deposition distance, it is found that a denser coating structure can be formed at a closer deposition distance.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.11
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• pp.1017-1023
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• 2010

This study investigated the effect of surfactants (nonionic surfactant (Tween 20), biosurfactant) on enhancing transport of bacteria (Bacillus subtilis ATCC 6633) in geological materials. Column experiments were performed under various surfactant conditions with columns packed with quartz sand (particle size distribution: 0.5~2.0 mm, mean diameter: 1.0 mm). Bacterial mass recovery, sticking efficiency, and other parameters were quantified from breakthrough curves. Results indicate that bacterial attachment to sand surfaces increased considerably in the presence of mineral salt medium (MSM), especially at the inlet, which was due to the increase of ionic strength by MSM. It was observed that bacterial transport in sand columns was enhanced in the presence of surfactant. Results also show that simultaneous injection of both surfactant and MSM or pre-injection of surfactant was more effective in bacterial transport enhancement than after-injection of surfactant. This study suggests that transport of bacteria in geological materials could be influenced by surfactants and their injection methods.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.10
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• pp.1028-1033
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• 2008

Sequential quick crushing and alkali hydrolysis(SeCAH), as a pretreatment for foodwaste, incorporating mechanical crushing and alkali hydrolysis was proposed and investigated in this study. Focuses were placed on the improvement of biodegradability of foodwaste and the estimation of potential inhibitors for anaerobic digestion. The solubility of the pretreated foodwaste by SeCAH was increased 2.5 times rather than mechanical crushing. Considering solubility improvement and energy consumption, 2,000 rpm of crushing strength and 5$\sim$10 sec of crushing time are recommended. After SeCAH, the fraction of large organic particles(>2.36 mm) of foodwaste was sharply decreased from 88.0% to 29.0%, otherwise the fraction of small particles(<75 $\mu$m) was greatly increased from 10.5% to 40.7%. Ammouinum, potassium and sulfate were estimated as potential inhibitors for anaerobic digestion and their concentrations in pig slurry were 3331.3 mg/L, 4256.5 mg/L and 1017.5 mg/L, respectively.

• Journal of Astronomy and Space Sciences
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• v.14 no.2
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• pp.312-319
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• 1997

The magnetometer is one of the most important payloads for scientific satellite to monitor the near-earth space environment. The electromagnetic variations of the space environment can be observed with the electric and magnetic field measurements. In practice, it is well known that the measurement of magnetic fields needs less technical complexities than that of electric fields in space. Therefore the magnetometer has long been recognized as one of the basic payloads for the scientific satellites. In this paper, we discuss the scientific fluxgate magnetometer which will be on board the KITSAT-3. The main circuit design of the present magnetometer is based on that of KITSAT-1 and -2 but its facilities have been re-designed to improve the resolution to about 5nT for scientific purpose. The calibration and noise level test of this circuit have been performed at the laboratory of the Tierra Tecnica company in Japan.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.487-494
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• 2020

The distance between the source and the detector, the diameter of the detector, and the volume effect of the radiation source result in a change in solid angle at the detector entrance, which affects the determination of detection efficiency by causing a difference in path length within the detector. A typical analysis method for calculating solid angles was useful only for a source (⁶⁰Co) with a simple geometric structure, so in this experiment, the distance between the detector and the source was measured by switching on for up to 25 cm with the reference point of window cap 0.5 cm. In addition, 450 and 1000 ㎖ Marinelli beaker of standard volumetric sources were closely adhered to the detector. For circular point sources co-axial with the detector, the change in the solid angle to the distance from the detector window is equal to half the square radius of the source versus the square radius of the detector, if the resulting relationship of the calculation analysis results in the detector being less than the radius of the source. Since the solid angular difference is 0.5 the result of Monte Carlo is acceptable. The relationship between detector and source distance is shown. Solid angles have been verified to decrease rapidly with distance. Measurement and simulation results for a volumetric source show a difference of ±1.01% from a distance of 0 cm and less than 4 % when the distance is reduced to 5 and 10 cm. It can be seen that the longer distance, the smaller efficiency angle, and the exponential increase in attenuation as the energy decreases, is reflected in the calculation of efficiency. Thus, the detection efficiency has proved sufficient for the use of solid angle and Monte Carlo codes.

• The Korean Journal of Nuclear Medicine
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• v.24 no.2
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• pp.237-243
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• 1990

Pulmonary embolism demands rapid and accurate diagnosis. And ventilation imaging has greatly improved the diagnostic accuracy of pulmonary embolism in addition to perfusion imaging. Agents currently used include xenon-133, krypton-81m and technetium-99m radioaerosols. However radioactive gases are compromised by availability and cost for krypton-81m, radiation dose, gamma energy and non?physiologic behaviour for xenon-133. Radioaerosols of technetium-99m componds are rapidly cleared from the lung after inhalation, and their relative low effeciency (specific radioactivity) and wide distribution of particle sizes make them also suboptimum. A new ventilation agent, Technegas is a suspension of structured graphite ellipsoids with diameter below 20nm, labelled with $^{99m}Tc$ in a carrier gas of Argon. This report describes the authors' clinical experience with Technegas. This is the first reported clinical study of this agent in Korea. A comparison of Technegas and $^{99m}Tc-DTPA$ aerosol was performed in 12 patients with various pulmonary diseases such as COPD, pulmonary tuberculosis and pleural effusion. All patients were studied with $^{99m}Tc-DTPA$ aerosol inhalation and Technegas ventilation. In both studies image quality was assessed (1) semiquantitatively by scoring bronchial and gastric activity, (2) subjectively by direct visual comparison of peripheral lung images and (3) quantitatively by computing the peripheral penetration index(PI) for each lungs. The bronchial activites were seen in 7 out of 12 cases with $^{99m}Tc-DTPA$ aerosol and in 5/12 with Technegas. The gastric activities were seen in 5/12 and 1/12 cases respectively. The average values of PI were 61.26% with $^{99m}Tc-DTPA$ aerosol and 69.20% with Technegas (p>0.05). Using $^{99m}Tc-DTPA$ aerosol, COPD patients showed deposition in the central airways with poor visualization of the peripheral areas of the lungs. In Technegas studies these phenomena were less prominent, and the examination is well tolerated by pateients and requires only a minimum of patient cooperation. With superiority of easy availability and handling, better physical characteristics and favorable Image quality, Technegas is a Promising agent for lung ventilation scanning.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.50.2-50.2
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• 2011

염료감응형 태양전지는 기존의 실리콘 태양전지에 비해 저렴한 가격과 다양한 날씨 조건에서도 태양광과의 반응성이 안정하다는 여러 가지 장점을 갖고 있다. 하지만 광전 변환 효율이 기존의 실리콘 태양전지에 비해 현저히 떨어진다는 문제점과 장기적으로 안정하지 못하다는 단점을 가지고 있다. 이러한, 염료감응형 태양전지에서 크게 광전 변환 효율을 향상시킬 수 있는 재료는 염료, $TiO_2$와 같은 반도체 산화물전극 재료, 전해질이다. 이 중 $TiO_2$의 특성 및 크기는 염료감응형 태양전지의 효율에 영향을 미친다. 염료감응형 태양전지의 광전 변환 효율을 증가시키기 위해서 $TiO_2$는 넓은 비표면적, 높은 전자의 이동성 및 태양광과의 우수한 반응성을 가져야 한다. Microwave hydrothermal 방법에 의해 제조된 hollow $TiO_2$를 염료감응형 태양전지에 적용시킬 경우 기존의 $TiO_2$의 광흡수 반응이 200~400 nm 사이에서 발생하는 반면, hollow $TiO_2$의 광흡수 반응은 기존의 UV 영역인 200~400 nm 뿐만 아니라 가시광 영역인 400~460 nm 에서도 광흡수 반응이 가능하기 때문에 염료감응형 태양전지에서 광전 변환효율을 증가 시킬 수 있을 것으로 기대된다. 또한, microwave hydrothermal법에 의해 제조된 hollow $TiO_2$는 150-200 nm의 크기를 갖으며 20-30 nm 크기의 $TiO_2$ particle들로 이루어져 있다. hollow $TiO_2$ (150-200 nm)를 기존의 $TiO_2$ (10-20 nm) 층 위에 올려 염료감응형 태양전지의 electrode에 적용할 경우 기존의 $TiO_2$ 단층을 이용한 것보다 우수한 light-scattering 효과를 갖게 되어 광전 변환 효율 증가에 긍정적인 영향을 미칠 것이다. 본 연구에서는 hollow $TiO_2$의 광학적 특성 및 결정성이 염료감응형 태양전지에 미치는 영향을 조사하였다. hollow $TiO_2$의 광학적 특성 및 결정성의 변화를 위하여 microwave hydrothermal 법의 합성 온도 및 합성시간에 변화를 주었다. hollow $TiO_2$의 광학적 특성은 UV-visible spectrometer를 이용하여 조사하였으며, hollow $TiO_2$의 형상과 결정학적 특성은 TEM과 SEM 그리고 X선 회절 분석을 이용하여 관찰되었고, hollow $TiO_2$의 비표면적 측정은 BET 측정법을 이용하였다. 또한 염료감응형 태양전지 cell을 제작하여 $100mW/cm^2$(AM 1.5G) 기준에서 광전 변환 효율을 측정하였다.

• Journal of Wetlands Research
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• v.16 no.4
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• pp.477-486
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• 2014

Integrated sand control including sediment discharge from hinterland rivers is necessary to maintain coastal sand resources over a long term. In this regard, the following subjects should be considered; efficient ways to transfer discharged sand from a river to the neighboring coast, measures to improve storage efficiency of the discharged sand at the river delta and/or river terrace, measures to prevent the sand resources from being discharged into the deep sea during flooding. From the 1997 to January 2004, the jetty of 156 m length was constructed the Heoya-river mouth to protect the blockade of river mouth. Several tests were carried out to investigate the characteristics of sediment transport and morphological change due to the construction of the jetty at the Heoya-river mouth. Firstly, The sand discharge from Heoya river is quantified by one-dimensional numerical analysis assuming the mixed sand of three different particle diameters. Also the numerical mode system, which predicts the sea bed changes obtained from the Bailard's energy model(1981), was combined with the wave, wave-induced currents and sediment transport models. Then, to understand the changes to the blockade of the river mouth, several aerial photographs were compared, which showed that the changes were significant.