• Fire Science and Engineering
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• v.33 no.1
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• pp.7-14
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• 2019

While wood pellets are often used as a fuel in thermoelectric power plants and firewood boilers, there is a risk of ignition temperature when strong wood pellets, which have a high calorific value, for prolonged periods of time. In this research study, the minimum auto ignition temperature and the ignition limitation temperature according to the change in flow rate depending on the size of the test vessel were calculated, and based on these temperatures, the apparent activation energy was calculated to predict the combustive properties of the material. The apparent activation energy was calculated to be 190.224 kJ/mol. The thicker the sample is storage in the vessel, the longer the ignition induction time was due to the increased difficulty in heat being transferred from the surface of the vessel to the middle section area of the vessel. For vessel of the same size, the higher the flow rate, the lower the auto ignition temperature was. It was also confirmed that increases in the size of the test vessel lowered the auto ignition temperature and increased the ignition induction time.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.5
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• pp.30-36
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• 2019

In order to evaluate service life of RC (Reinforced Concrete) structures exposed to chloride attack, chloride penetration analysis is required referred to the chloride diffusion coefficient from the actual mix proportions. In this work, accelerated diffusion coefficients are obtained from NT BUILD 492 and ASTM C 1202 and the related apparent diffusion coefficients are derived via the previously proposed relationship for RC structures near to sea shore. Considering the properties of the mix proportions and the most conservative analysis conditions like critical and surface chloride contents, service lifes in column and exterior wall member are evaluated through conventional program LIFE 365 ver.2. The different built-up period of 10 and 15 years has no significant effect on service life. The results from mix proportions with slag show longer than 75 years of service life with the help of higher time dependent parameter and lower initial diffusion coefficient.

• Geophysics and Geophysical Exploration
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• v.24 no.4
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• pp.171-179
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• 2021

We outline a process for estimating Cole-Cole parameters from time-domain induced polarization (IP) data. The IP transients are all inverted to 2D Cole-Cole earth models that include resistivity, chargeability, relaxation time, and the frequency exponent. Our inversion algorithm consists of two stages. We first convert the measured voltage decay curves into time series of current-on time apparent resistivity to circumvent the negative chargeability problem. As a first step, a 4D inversion recovers the resistivity model at each time channel that increases monotonically with time. The desired intrinsic Cole-Cole parameters are then recovered by inverting the resistivity time series of each inversion block. In the second step, the Cole-Cole parameters can be estimated readily by setting the initial model close to the true value through a grid search method. Finally, through inversion procedures applied to synthetic data sets, we demonstrate that our algorithm can image the Cole-Cole earth models effectively.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.547-552
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• 2022

In this study, we secured a technology for manufacturing expanded glass of uniform quality by using general tempered glass, that is, window glass, among automotive glass that is scrapped, and verified whether the manufactured expanded glass can be used for lithium battery fire suppression. The process of manufacturing expanded glass using waste glass is generally divided into Crushing → Milling → Granulation → Expansion → Cooling. With several trials a nd errors. It is obtained a yield of 0.5 ø mm to 2 ø mm spherical particles of 80 % or more. By comparing the surface analysis and physical properties, a more suitable sample was selected as a fire extinguishing agent for lithium batteries, and it was confirmed that the result of the adaptability test for lithium battery fire was satisfactory.

• Nuclear Engineering and Technology
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• v.26 no.2
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• pp.285-293
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• 1994

The transport of radionuclides in a compacted bentonite is dominated by diffusion. Through-diffusion tests for iodide were performed to investigate the diffusion characteristics of anionic radionuclides in a domestic bentonite. The bentonite used was sampled from the southeastern area of Korea and the solution was synthetic groundwater spiked with a tracer of I -125(as Na$^{125}$ I). The dry densities of compacted bentonite were 1.2, 1.4, and 1.7 Mg/㎥. The apparent diffusion coefficients and the effective diffusion coefficients of the iodide decrease with increasing dry density. The values were from 3.80 to 7.12$\times$10$^{-11}$ $m^2$/s for the apparent diffusion coefficients and from 1.25 to 7.97$\times$10$^{-12}$ $m^2$/s for the effective diffusion coefficient, respectively. The experimental results also showed that the apparent diffusion coefficients depended on the pore structure of compacted bentonite and the effective diffusion coefficients were attributed to the pore structure and the effective porosity that represents the available pathway for the diffusional transport of iodide. The results obtained will be used as basic data for the safety assessment of a repository.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.18 no.2
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• pp.55-61
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• 1982

Simultaneous investigations for drift bottle and dye diffusion experiment were carried out in Suyeong bay. Seawater in Suyeong bay flowed differently in the vicinity of Suyeong river estuary and Nam-cheon Dong respectively. The speed of current did not exceed one knot in this bay. The dye patch moved to Kwangan beach in the dye diffusion experiment. The relationship between apparent diffusivity and diffusion time was appeared as Ka=0.0025t super(1.9). The variance was calculated to be 2.9 power of the diffusion time. And the exponent diffusivity versus the scale of diffusion time was appeared to be 1.3.

• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.2
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• pp.84-92
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• 2010

This research was conducted to investigate physico-chemical characteristics of municipal solid waste (MSW) generated from T City, Gangwon-do and leaching characteristics of the incineration ash. From the results, bulk density of MSW in T city was $231kg/m^3$. Combustible and incombustible components were in 94.0% and 6.0%, respectively. Food waste and papers in combustible component occupied 32.3% and 41.2%. Water, volatile solids, and ash content were 41.3%, 50.5%, and 8.2%. C, H, O, N, S, and Cl showed 51.4%, 6.3%, 26.7%, 1.1%, 0.2%, 0.5%, respectively. Low heating value (2,704 kcal/kg) of T city was similar to 2,764 kcal/kg of Chuncheon and was 1,000 kcal/kg higher than 1,467~1,584 kcal/kg of the past Kuro-gu and Koyang city. The specification of leaching characteristics of the incineration ash were within the Korean regulation standard.

• Geophysics and Geophysical Exploration
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• v.11 no.1
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• pp.52-59
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• 2008

We have developed a new deep-towed marine DC resistivity survey system. It was designed to detect the top boundary of the methane hydrate zone, which is not imaged well by seismic reflection surveys. Our system, with a transmitter and a 160-m-long tail with eight source electrodes and a receiver dipole, is towed from a research vessel near the seafloor. Numerical calculations show that our marine DC resistivity survey system can effectively image the top surface of the methane hydrate layer. A survey was carried out off Joetsu, in the Japan Sea, where outcrops of methane hydrate are observed. We successfully obtained DC resistivity data along a profile ${\sim}3.5\;km$ long, and detected relatively high apparent resistivity values. Particularly in areas with methane hydrate exposure, anomalously high apparent resistivity was observed, and we interpret these high apparent resistivities to be due to the methane hydrate zone below the seafloor. Marine DC resistivity surveys will be a new tool to image sub-seafloor structures within methane hydrate zones.

• Investigative Magnetic Resonance Imaging
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• v.17 no.1
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• pp.1-7
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• 2013

Purpose : The purpose of this study is to correlate the imaging findings and the clinical findings in patients with transient splenial lesions (TSL). Materials and Methods: Total of 7 patients (M: F = 4: 3; age range 11 - 38 years, mean age 25.5 years) were studied between November 2006 and April 2011. The MRI findings and clinical findings in all patients were retrospectively reviewed. The location, MR signal intensity, restricted diffusion, enhancement pattern and reversibility from the follow up images were reviewed. Clinical features were reviewed with respect to the presented symptoms, signs, treatment and outcome. Results: The lesions were located in the splenium of corpus callosum in all patients. All lesions showed high signal intensity on diffusion weighted imaging (DWI), and six patients showed restricted diffusion on the apparent diffusion coefficient (ADC) map. ADC map was not available in one patient. All lesions (n = 7) showed high signal intensity on the T2 weighted image (T2WI). Five of the patients (71.4%) with follow up images (range 7 - 34 days) showed complete resolution of focal high signal intensity on DWI, with recovery of ADC values as well as T2WI. After contrast media administration, none of the lesions showed any enhancements. All lesions with various etiologies including TB medication were developed in younger age patients and showed reversibility after the acceptable period of minimum 7 days with conservative treatment. Conclusion: All TSL showed nonspecific imaging findings, including restricted diffusion on DWI and ADC map on the initial images. However, reversibility of the lesions and the young age preference can be a characteristic finding of TSL with acceptable period of minimum 7 days. In addition, to keep it in mind that various etiologies including TB medication may cause TSL, is important for radiologists as well as clinicians.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.87.2-87.2
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• 2015

국립고흥청소년우주체험센터에서는 1m 반사 망원경의 완성을 눈앞에 두고 있다. 천체 망원경으로 관측을 하기 위해서는 시간과 천구 좌표계의 이해는 필수적이다. 하지만 현재 본 센터에서는 천구의를 활용한 프로그램 이외에는 시간과 좌표계를 다루는 체험 프로그램이 전무한 실정이다. 센터에서는 참가자가 자신의 그림자로 시각을 알 수 있는 지평면 해시계, 센터에서 쓰지 않고 있는 구형 가마솥을 재활용한 앙부일구, 덕흥 천문대 교육동의 벽에 벽면 해시계의 제작 및 설치를 추진하고 있다. 차후 이를 활용한 체험 프로그램을 참가자에게 제공한다면 태양의 겉보기 운동을 통해 시간과 공간에 대한 개념을 쉽게 알려줄 수 있을 뿐만 아니라 우리 민족의 과학적 자긍심을 심어줄 수 있을 것으로 기대한다.