• Analytical Science and Technology
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• v.35 no.6
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• pp.256-266
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• 2022

It is important to determine the concentration of long-lived radionuclides (e.g., ¹²⁹I) in nuclear waste to ensure safety when handling it. To analyze nuclides in a solid sample (e.g., concrete and soil), it is essential to effectively separate and purify the nuclides of interest in the sample. This study reports the comprehensive efforts made to validate the analytical procedure for ¹²⁹I detection in solid samples, using a high-temperature combustion furnace. ¹²⁹I volatilized from the sample collected in 0.01 M HNO₃ solution with a reducing agent (e.g., NaHSO₃) and was rapidly measured by ICP-MS. Analytical conditions, such as pyrolysis temperature and types of mobile phase gas, catalyst, and trapping solution, were optimized to obtain a high recovery rate of spiked ¹²⁹I. Finally, the optimized method was applied for the simultaneous analysis of other volatile radionuclides, such as ³H and ¹⁴C. The performance test results for the optimized method confirmed that the LSC (for ³H and ¹⁴C) and ICP-MS (for ¹²⁹I) measurements, with the separation of volatile nuclides using a high-temperature combustion furnace, were reliable.

• Journal of the Korean Geotechnical Society
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• v.39 no.10
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• pp.41-48
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• 2023

The presence of abnormalities in the subgrade of roads poses safety risks to users and results in significant maintenance costs. In this study, we aimed to experimentally evaluate the temperature distributions in abnormal areas of subgrade materials using infrared cameras and analyze the data with machine learning techniques. The experimental site was configured as a cubic shape measuring 50 cm in width, length, and depth, with abnormal areas designated for water and air. Concrete blocks covered the upper part of the site to simulate the pavement layer. Temperature distribution was monitored over 23 h, from 4 PM to 3 PM the following day, resulting in image data and numerical temperature values extracted from the middle of the abnormal area. The temperature difference between the maximum and minimum values measured 34.8℃ for water, 34.2℃ for air, and 28.6℃ for the original subgrade. To classify conditions in the measured images, we employed the image analysis method of a convolutional neural network (CNN), utilizing ResNet-101 and SqueezeNet networks. The classification accuracies of ResNet-101 for water, air, and the original subgrade were 70%, 50%, and 80%, respectively. SqueezeNet achieved classification accuracies of 60% for water, 30% for air, and 70% for the original subgrade. This study highlights the effectiveness of CNN algorithms in analyzing subgrade properties and predicting subsurface conditions.

• Journal of the Korea Concrete Institute
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• v.22 no.6
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• pp.851-858
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• 2010

In this study, waste glass and bottom ash were used as basic materials in order to secure a recycling technology of by-products which was mostly discarded and reclaimed. In addition, because softening point of waste glass is less than $700^{\circ}C$ and bottom ash includes combustible material, it was possible to manufacture low-temperature sintering lightweight aggregates for energy saving at $800{\sim}900^{\circ}C$ that it is as much as 20~30% lower than sintering temperature of existing lightweight aggregates. Thermal conductivity of newly-developed lightweight aggregates was 0.056~0.105W/m. K and its porosity was 40.36~84.89%. A coefficient of correlation between thermal conductivity and porosity was -0.97, it showed very high negative correlationship. With this, we were able to verify that porosity is key factor to affect thermal conductivity. Microstructure of lightweight aggregates by $CaCO_3$ content and replacement ratio of bottom ash in the variation of temperature were that $CaCO_3$ content increased along with pore size while replacement ratio of bottom ash increased as pore size decreased. Specially, most pores were open pore instead of closed pore of globular shape when replacement ratio of bottom ash was 30%, and pore size was small about 1/10~1/5 as compared with case in bottom ash 0~20%. In addition, open pore shapes were remarkably more irregular form of open pore in $900^{\circ}C$ than $700^{\circ}C$ or $800^{\circ}C$ when replacement ratio of bottom ash was 30%. We reasoned hereby that these results will influence on absorption increase, strength and thermal conductivity decrease of lightweight aggregates.

• Journal of Aquaculture
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• v.4 no.1
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• pp.1-12
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• 1991

A series of rearing experiments were conducted to determine the growth rates and feed conversion efficiencies of tilapia in accordance with body size or age in nearly total closed system glass aquariums ($270\;\ell$ each in water volume) and concrete tanks ($4000\;\ell$) from April 10 to October 16, 1987. The fish used for the experiments was a Japanese strain of Oreochromis niloticus, and the size of the fish ranged from 7 g to more than 1,000 g in body weight. The starting stocking rates for each experimental lot were 10 to 20 kg in the glass aquarium ($3.7{\%}$ to $7.4{\%}$ of water volume) and 200 kg in the concrete tank ($5{\%}$ of water volume). A single experimental rearing term was 14 days with slight variations on occasions. Water temperature was designed to be kept at $26^{\circ}C$ but slight fluctuations were inevitable. Dissolved oxygen level was designed to be maintained at around $3\;mg/\ell$, but it also showed some variations. The ammonia level in the glass aquarium section once reached up to $18\;mg/\ell$, but generally remained at around $4\;mg/\ell$, and in the concrete tank section it was maintained at around $1\;mg/ell$. The feed was composed of mainly soybean meal with a small amount of fish meal as the protein source, and the crude protein content was about $32{\%}$. Mean daily growth rate was $3.5{\%}$ of body weight with 0.9 in food conversion ratio in the glass aquarium when the mean weight of fish was around 10 g with gradually reduced performances as the fish grew bigger. When the mean weight was 800 g, mean daily growth rate was $0.5{\%}$ with about 1.5 in food coversion for fish in the glass aquarium, and $0.8{\%}$ and 1.6 for fish in the concrete tank, respectively. According to the mean growth rate obtained from this experiment, it was calculated that the fish reared in the concrete tank require 223 days from 50 g to reach 1,000 g which is the ideal size for market in Korea, at the conditions provided as above, and 302 days from 10 g fingerlings to 800 g fish in the glass aquarium conditions of the closed recirculating water system.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.53-62
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• 2018

Follofwing the accelerating speed-up of trains and rising demand for large-volume transfer capacity, not only in Korea, but also around the world, track structures for trains have been improving consistently. Precast concrete slab track (PST), a concrete structure track, was developed as a system that can fulfil new safety and economic requirements for railroad traffic. The purpose of this study is to provide the information required for the development and design of the system in the future, by analyzing the behavior of each structural member of the PST system. The stress distribution result for different combinations of appropriate loads according to the KRL-2012 train load and KRC code was analyzed by conducting a three-dimensional finite element analysis, while the result for different thicknesses of the grouting layer is also presented. Among the structural members, the largest stress took place on the grouting layer. The stress changed sensitively following the thickness and the combination of loads. When compared with a case of applying only a vertical KRL-2012 load, the stress increased by 3.3 times and 14.1 times on a concrete panel and HSB, respectively, from the starting load and temperature load. When the thickness of the grouting layer increased from 20 mm to 80 mm, the stress generated on the concrete panel decreased by 4%, while the stress increased by 24% on the grouting layer. As for the cracking condition, tension cracking was caused locally on the grouting layer. Such a result indicates that more attention should be paid to the flexure and tension behavior from horizontal loads rather than from vertical loads when developing PST systems. In addition, the safety of each structural member must be ensured by maintaining the thickness of the grouting layer at 40 mm or more.

• Journal of the Korean Institute of Landscape Architecture
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• v.40 no.6
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• pp.190-197
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• 2012

The purpose of this study was to evaluate thermal environment and heat budget of light thin layer green roof through an experiment in order to quantify its heat budget. Two concrete model boxes($1.2m(W){\times}1.2m(D){\times}1.0m(H)$) were constructed: One experiment box with Zoysia japonica planted on substrate depth of 10cm and one control box without any plant. Between June 6th and 7th, 2012, outside climatic conditions(air temperature, relative humidity, wind direction, wind speed), evapotranspiration, surface and ceiling temperature, heat flux, and heat budget of the boxes were measured. Daily maximum temperature of those two days was $29.4^{\circ}C$ and $30^{\circ}C$, and daily evapotranspiration was $2,686.1g/m^2$ and $3,312.8g/m^2$, respectively. It was found that evapotranspiration increased as the quantity of solar radiation increased. A surface and ceiling temperature of those two boxes was compared when outside air temperature was the greatest. and control box showed a greater temperature in both cases. Thus it was found that green roof was effective in reducing temperature. As results of heat budget analysis, heat budget of a green roof showed a greater proportion of net radiation and latent heat while heat budget of the control box showed a greater proportion of sensible heat and conduction heat. The significance of this study was to analyze heat budget of green roof temperature reduction. As substrate depth and types, species and seasonal changes may have influences on temperature reduction of green roof, further study is necessary.

• Journal of Agricultural Extension & Community Development
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• v.11 no.2
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• pp.291-301
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• 2004

As Russian government signs the Kyoto Protocol on November 2004, it will go into effect on Feb. 16 2004. Under the Protocol, 38 industrialized countries are to reduce their combined emissions of six major greenhouse gases, including carbon dioxide and methane, to below 1990 levels during the 2008-2012 period. Korea ratified the Protocol in 2002 and is currently exempt from the reduction measures. It is expected, however, that Korea will be pressured to join the reduction scheme from 2013. Although the Kyoto Protocol is national-level agreement each country's urban governments are expected and have to play important role to make it successful one. It is more so for such mesa cities as Seoul which has experienced rapidly worsening environment recent years. Statistics shows that the annual average temperature in Seoul has increased by $1.5^{\circ}C$ for the last century, which is much higher than the national average. 'Heat Island' effect is not unusual any more in Seoul. This study reviews the key points of the Kyoto Protocol, urban warming phenomena in Seoul and its policy responses. In doing so, this study evaluates Tokyo case as a comparative one. It is found that Seoul needs to develop more concrete and feasible policy measures to get current efforts more effective.

• Journal of the Korea Institute of Building Construction
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• v.16 no.3
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• pp.211-217
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• 2016

In this research, the performance of surface covering technique using a white-colored bubble sheet on reducing the cracking due to the plastic, and drying shrinkages for high rise building construction were evaluated by comparing the exposed surface without any surface treatment. From the results of the experiment conducted during fall season, desired results of decreased numbers, length, maximum width, and area of cracking were obtained without a significant difference on heat of hydration and cumulative temperature. Therefore, it is considered that the surface covering technique using bubble sheet is an appropriate method for preventing plastic and drying shrinkage cracking at fall season concrete construction.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.6 no.1
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• pp.55-63
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• 2008

A swelling clay should remain physically and chemically stable for a long time to perform its functions as a buffer material of a high-level waste (HLW) repository. The longevity issues in the swelling clay were reviewed to evaluate their importance in the performance of a repository. The review results suggest that an elevated temperature due to decay heat, groundwater chemistry, high pH environment by concrete, organic matter and microbes, radiation, and mechanical disturbance might significantly affect the long-term performance of a swelling clay as a buffer material. This paper will be used as basic informations to design the swelling clay buffer for a HLW repository.

• Structural Engineering and Mechanics
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• v.74 no.4
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• pp.481-494
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• 2020

In this paper, a probability-based procedure to evaluate the performance of existing RC structures exposed to seismic and fire actions is presented. The procedure is demonstrated with reference to an existing old school building, located in Italy. The vulnerability assessment of the building highlights deficiencies under both static and seismic loads. Retrofit operations are designed to achieve the seismic safety. The idea of the work consists in assessing the performance of the existing and retrofitted building in terms of both the seismic and fire resistance. The seismic retrofit and fire resistance upgrading follow different paths, depending on the specific configuration of the building. A good seismic retrofit does not entail an improving of the fire resistance and vice versa. The goal of the current work is to study the variation of response due to the uncertainties considered in records/fire curves selection and to carry out the assessment of the studied RC structure by obtaining fragility curves under the effect of different records/temperature. The results show the fragility curves before and after retrofit operations and both in terms of seismic performance and fire resistance performance, measuring the percent improving for the different limit states.