• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.1
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• pp.60-68
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• 2012

In this study, the manufacturing process of micro capsulized PCM (phase changing material) for thermal storage performance of latent heat was investigated to save energy during the use of buildings: i.e. use of melamine-type resin as the micro-capsule material and paraffin wax as the inner material that are together used in concrete walls. For the manufacturing process of the micro-capsulized PCM, the amount of SDS addition as surfactant was the key variable and the resulting thermal storage performance depended on the SDS amount. With increasing amount of SDS, the micro capsulation became much easier while the capsule surface became harder. The micro capsules became uniform at an optimum SDS addition. The addition of SDS also affected the thermal capacity: with increasing SDS amount, the heat storage and release tendency at melting point was more clearly manifested. The current investigation is part of a study under progress to explore the use of PCM in concrete walls to save building maintenance cost and energy.

• Fire Science and Engineering
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• v.22 no.1
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• pp.1-9
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• 2008

Carbon dioxide($CO_2$) agent, which has more safely extinguished fire than any other gaseous fire extinguishing agents, has been widely used in various protected enclosures and types of fires. According to the concept of performance-based design(PBD). $CO_2$ extinguishing system to be designed is needed to be evaluated for the performance of fire suppression with possible fire scenarios in an enclosure. In this paper, CFD simulations were carried out to study the effects of opening area on the performance of $CO_2$ extinguishing system and the flow characteristics in the machine room of $100m^3$ in which kerosene spill fire happened. This study showed that time of fire suppression increased linearly in proportion to the size of opening area, and fires for each model were completely suppressed prior to the end of discharge of $CO_2$ agent. It was shown that mass flow rate through opening was influenced by the combined effects of heat release rate of fire and discharge of $CO_2$ agent. After $CO_2$ agent was completely discharged, oxygen concentrations in enclosures for each model were lower than the limit concentration of combustion.

• Fire Science and Engineering
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• v.13 no.1
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• pp.37-47
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• 1999

The spreading fire of very small floating particles after they are ignited is fast and t therefore dangerous. The research on this area has been limited to experiments and global simulations which treat them as dusts or gaseous fuel with certain concentration well m mixed with air. This research attempted micro-scale analysis of ignition of those particles modeling them as liquid droplets. For the beginning, the in-line array of fuel droplets is modeled by two-dimensional, unsteady conservation equations for mass, momentum, energy and species transport in the gas phase and an unsteady energy equation in the liquid phase. They are solved numerically in a generalized non-orthogonal coordinate. The single step chemical reaction with reaction rate controlled by Arrhenius’ law is assumed to a assess chemical reaction numerically. The calculated results show the variation of temperature and the concentration profile with time during evaporation and ignition process. Surrounding oxygen starts to mix with evaporating fuel vapor from the droplet. When the ignition condition is met, the exothermic reactions of the premixed gas initiate a and burn intensely. The maximum temperature position gradually approaches the droplet surface and maximum temperature increases rapidly following the ignition. The fuel and oxygen concentration distributions have minimum points near the peak temperature position. Therefore the moment of ignition seems to have a premixed-flame aspect. After this very short transient period minimum points are observed in the oxygen and fuel d distributions and the diffusion flame is established. The distance between droplets is an important parameter. Starting from far-away apart, when the distance between droplets decreases, the ignition-delay time decreases meaning faster ignition. When they are close and after the ignition, the maximum temperature moves away from the center line of the in-line array. It means that the oxygen at the center line is consumed rapidly and further supply is blocked by the flame. The study helped the understanding of the ignition of d droplet array and opened the possibility of further research.

• Journal of radiological science and technology
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• v.34 no.4
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• pp.351-357
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• 2011

The $^{18}F$-FDG is one of the widely used isotopes for PET/CT scans. Dose amount injected to the patient depends on the characteristics of PET/CT systems. Obviously, the technologists who contact with patients would be exposed as well. In this study, we evaluated the exposed dose of the technologist who works on the PET/CT scanner. The exposed dose were measured every month with the TLDs from 6 technologists. Each technologist is shift-worker who manages 3 different PET/CT systems(Scanner 1(S1): 0.15 mCi/kg, Scanner 2(S2): 0.17 mCi/kg, Scanner 3(S3): 0.12 mCi/kg). The average exposed doses of technologists for each PET/CT system were measured as 0.76 mSv for S1, 0.93 mSv for S2 and 0.47 mSv for S3. The maximum dose was 1.12 mSv and minimum was 0.42 mSv. The results showed that there was a correlation between exposed dose and PET/CT system(p<0.005). Less injected dose for patient occurs less exposed dose for technologist. Various studies for the low dose PET/CT system are required for not only the patient but also the technologist.

• Korean Journal of Optics and Photonics
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• v.8 no.6
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• pp.510-515
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• 1997

Packaging takes an extremely important element of optical module cost due primarily to the added complication of alignment between semiconductor devices and optical fiber, and many efforts have been devoted on reducing the cost by eliminating the complicated optical alignment procedures in passive manner. In this study, we fabricated silicon optical benches on which the optical alignments are accomplished passively. To improve the positioning accuracy of a flip-chip bonded LD, we adopted fiducial marks and solder dams which are self-aligned with V-groove etch patterns, and a stand-off to control the height and to improve the heat dissipation of LD. Optical sub-assemblies exhibited an average efficiency of -11.75$\pm$1.75 dB(1$\sigma$) from the LD-to-single mode fiber coupling and an average sensitivity of -35.0$\pm$1.5 dBm from the fiber and photodetector coupling.

• Fire Science and Engineering
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• v.23 no.5
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• pp.57-65
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• 2009

This study was intended to conduct a Real-scale fire test to predict the fire behavior by unit space at the apartment building where a huge casualties and injuries are likely. After setting the inflammables inside the house, the test aimed to identify the fire characteristics to each unit item was carried out. The house was divided into 4 unit space such as kitchen, living room, bedroom and a study for a real scale fire test. As a result, bedroom reached to flashover state in 5minutes after setting the fire, indicating a rapid fire growth such as 7433.3kW of maximum thermal emissivity, 578.6ppm of carbon monoxide, 1.25ppm of carbon dioxide and $1,350^{\circ}C$ of maximum indoor temperature. Particularly, the fire growth was made up to critical temperature which might cause a severe damage to the people within 3minutes, if the fire were not extinguished at inflammable space at the early stage of fire, which stressed the need of early response. The result of a real scale fire test could be compared with the outcome of expanded simulation test and used in predicting the fire spread at the space for different use.

• Fire Science and Engineering
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• v.30 no.5
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• pp.93-99
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• 2016

This study tested the combustion characteristics of veneer specimens coated with four kinds of ammonium salts. Each veneer specimen was coated three times with 20 wt.% ammonium salt solutions at room temperature. After drying, the combustion characteristics of the specimens coated with chemicals, were investigated using the cone calorimeter (ISO 5660-1, 2). The specimens coated with monoammonium phosphate (MAPP) and, diammonium phosphate (DMPP) showed a 6.7% and, 10.0%, lower mean heat release rate ($HRR_{mean}$), respectively, than that of the uncoated specimen. On the other hand, the specimens coated with MAPP showed a 15.7% higher $CO_{peak}$ production rate and the specimens coated with DAPP showed by 8.2% lower rate than that of the uncoated specimen. The veneer coated with ammonium sulfate (AMSF) and DAPP showed a 9.6% and 33.3% lower the peak smoke production rate ($SPR_{peak}$) than that of the uncoated specimen. In addition, the time to the peak smoke extinction area ($SEA_{peak}$) was delayed by 38.4% in the specimens coated with DAPP than the uncoated specimen. Therefore, DAPP inhibited the combustion properties of the veneer and showed a tendency to reduce smoke production.

• The Journal of the Korea Contents Association
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• v.19 no.12
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• pp.84-92
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• 2019

The deterioration of the urban heat environment due to climate change and the occurrence of heat-related diseases have emerged as one of the major social problems. This has led to more research on climate change, including heat waves, but it is mainly focused on climate factors. However, the urban heat island phenomenon accelerates the summer heat wave, and the increasing trend of heat-related patients in urban areas suggests the impact of the city's environment. Thus, this study analyzed the effects of physical and social characteristics of urban areas on heat-related patients in Seoul and Gyeonggi-do. The analysis showed that the ratio of the total area of residential, commercial and industrial facilities, the main source of heat energy locality, among the land use statuses, was not statistically significant, but the road area and the green area were found to have a positive and negative The population density and the percentage of people aged 65 or older, the percentage of people living alone and the proportion of people receiving basic living were all shown to be significant, with only the ratio of elderly living alone and the ratio of population density having negative effects. The results of the study can be used to develop urban policy alternatives related to local warming patients.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.4
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• pp.178-184
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• 2010

The $12CaO{\cdot}7Al_2O_3$(C12A7) powders were successfully synthesized using combustion method with microwave-assistant and C12A7:H were fabricated by post-annealed process in Ar/H atmosphere. X-ray diffraction patterns and TGDSC were used for investigating to the precursors of crystalline and reaction depending on temperature. C12A7:H that was treated post-annealed process were investigated TG-MS and Hall-measurement for confirming H ions doping and checking electrical resistivity of C12A7:H. H ion substituted to $O^{2-}$ ions in the C12A7 cages were confirmed at $289.5^{\circ}C$ by TG-MS and C12A7:H calcined at $1000^{\circ}C$ in Ar/H=8:2 atmosphere for 8~10 h has low electrical resistivity about $10^2{\Omega}{\cdot}cm$ at room temperature.

• Journal of the Korean Chemical Society
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• v.44 no.6
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• pp.526-532
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• 2000

Cation exchange separation and inductively coupled plasma atomic emission spectrometric(ICP-AES) determination of ruthenium in HCl solutions were studied to quantitatively determine ruthenium in spent nuclear fuels. Ruthenium-bearing samples were dissolved with the mixed acid solution(9 : 1 mole ratio, HCl-HNO$_3$) using an acid digestion bomb. Based on the absorption spectra and ion exchange behaviour of ruthenium in hydrochloric acid media, its possible chemical species were discussed. On a cation exchange column (0.7 ${\times}$ 8.0 cm) packed with AG 50W ${\times}$ 8(100~200 mesh) and equilibrated with 0.5 M HCl, ruthenium was eluated with 0.5 M HCl while uranium was retained on the column. The established separation method was applied to a simulated spent nuclear fuel and resulted in the recovery of 98.5% with a relative standard deviation of 0.7%.