• Journal of the Korean Association of Geographic Information Studies
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• 제15권3호
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• pp.91-102
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• 2012

As the basis of the environmental ecological river management, this research developed a method of habitat classification using imagery information to understand a distribution characteristics of fish living in a natural river. First, topographic survey and investigation of discharge and water temperature were carried out to analyze hydraulic characteristics of fish habitat, and the unmanned aerial photography was applied to acquire river imagery at the observation time. Riffle, pool, and glide regions were selected as river habitat to analyze fish distribution characteristics. Analysis showed that the standard deviation of RGB on the riffle is higher than pool and glide because of fast stream flow. From the classification accuracy estimation on riffle region according to resolution and kernel size using the characteristics of standard deviation of RGB, the highest classification accuracy was 77.17% for resolution with 30cm and kernel size with 11. As the result of water temperature observation on pool and glide using infrared camera, they were $19.6{\sim}21.3^{\circ}C$ and $15.5{\sim}16.5^{\circ}C$ respectively with the differences of $4{\sim}5^{\circ}C$. Therefore it is possible to classify pool and glide region using the infrared photography information. The habitat classification to figure out fish distribution can be carried out more efficiently, if unmanned aerial photography system with RGB and infrared band is applied.

• The KSFM Journal of Fluid Machinery
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• 제17권6호
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• pp.84-88
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• 2014

A long term passive cooling system is considered as the most important safety feature for the nuclear design after the Fukushima Daiichi nuclear power plant accident in 2011. The conventional active pump driven safety systems are not available during a station Black Out (SBO) accident. The current design requirement on cooling time of the Passive Auxiliarly Feedwater System (PAFS) is about 8 hours only. To meet the 72 hours cooling time, the pool capacity of cooling water tank should be increased as much as 3~4 times larger than that of current water cooling tank. In order to extend the cooling time for 72 hours, a new passive air-water combined cooling system is proposed. This paper provides the feasibility of the combined passive air-water cooling system. The current pool capacity of water cooling system is preserved, and the cooling capability is extended by an additional air cooler.

• The Korean Journal of Nuclear Medicine Technology
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• 제12권1호
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• pp.33-38
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• 2008

Purpose: The Gated cardiac blood pool scan is non-invasive method that a quantitative evaluation of left ventricular function. Also this scan have shown the value of radionuclide ejection fraction measurements during the course of chemotherapy as a predictor of cardiac toxicity. Therefore a reliable method of monitoring its cardiotoxic effects is necessary. the purpose of this study is to minimize the overestimate of left ventricular ejection fraction (LVEF) by modified body position to reduce the influence of scattered rays from surrounding organs of the heart in the background region of interest. Materials and Methods: Gated cardiac blood pool scan using in vivo $^{99m}Tc$-red blood cell (RBC) was carried out in 20 patients (mean $44.8{\pm}8.6$ yr) with chemotherapy for a breast carcinoma. Data acquisition requires about 600 seconds and 24 frames of one heart cycle by the multigated acquisition mode, Synchronization deteriorates toward the end of the cycle and with the distance from the trigger signal (R-wave) by ECG gating. Gated cardiac blood pool scan was studied with conventional method (supine position and the detector head in $30-45^{\circ}$ left anterior oblique position and caudal $10-20^{\circ}$ tilt) and compared with modified method (left lateral flexion position with 360 mL of drinking water). LVEF analysis was performed by using the automatically computer mode. Results: The ROI counts of modified scan method were lower than LV conventional method ($1429{\pm}251$ versus $1853{\pm}243$, <0.01). And LVEF of modified method was also decrease compared with conventional method ($58.3{\pm}5.6%$ versus $65.3{\pm}6.1%$, <0.01). Imaging analysis indicated that stomach was expanded because of water and spleen position was changed to lateral inferior compared with conventional method. Conclusion: This study shows that the modified method in MUGA reduce the influence of scattered rays from surrounding organs. Because after change the body position to left lateral flexion and drinking water, the location of spleen, left lobe of liver and stomach had changed and they could escaped from background ROI. Therefore, modified method could help to minimize the overestimate LVEF (%).

• Proceedings of the KSME Conference
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.57-62
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• 2001

Korea Atomic Energy Research Institute (KAERI) launched an intermediate scale steam explosion experiment named Test for Real cOrium Interaction with water (TROI) using reactor material to investigate whether the corium would lead to energetic steam explosion when interacted with cold water at low pressure. The melt-water interaction is confined in a pressure vessel with the multi-dimensional fuel and water pool geometry. The cold crucible technology, where the mixture of powder in a water-cooled cage is heated by high frequency induction, is employed. In this paper, results of the first series of tests ($TROI-1{\sim}5$) were discussed. The ZrO2 jets with 5kg mass and 5cm diameter were poured into the 67cm deep water pool at $30{\sim}95^{\circ}C$. Either spontaneous steam explosions or quenching was observed. The morphology of debris and pressure wave profiles clearly indicates the each case.

• Nuclear Engineering and Technology
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• 제52권1호
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• pp.27-36
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• 2020

Natural convection and thermal stratification phenomena are found in large water pools that are being used as heat sinks for decay heat removal from the reactor core using passive heat removal systems. In this study, the two-phase (water and air) natural convection and thermal stratification phenomena with conjugate heat transfer in the rectangular enclosure were investigated numerically using ANSYS Fluent 17.2 code. The transient numerical simulations of these phenomena in the full-scale computational domain of the experimental facility were performed. Generation of water vapour bubbles around the heater rod and evaporation phenomena were included in this numerical investigation. The results of numerical simulations are in good agreement with experimental measurements. This shows that the natural convection is formed in region above the heater rod and the water is thermally stratified in the region below the heater rod. The heat from higher region and from the heater rod is transferred to the lower region via conduction. The thermal stratification disappears and the water becomes well mixed, only after the water temperature reaches the saturation temperature and boiling starts. The developed modelling approach and obtained results provide guidelines for numerical investigations of thermal-hydraulic processes in the water pools for passive residual heat removal systems or spent nuclear fuel pools considering the concreate walls of the pool and main room above the pool.

• The Journal of the Korea institute of electronic communication sciences
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• 제14권3호
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• pp.505-512
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• 2019

We propose a new method to monitor the water level of spent fuel pool in a nuclear power plant without electric power. We also analyze the performance and limitation of the proposed method. Our method is based on the reflected optical power at the end of optical fiber through a $1{\times}N$ optical coupler. We reveal that there is no problem to monitor the water level when using a $1{\times}8$ optical coupler. However, when a $1{\times}16$ optical coupler is used, only 15 out of 16 output ports can be used due to Rayleigh back-scattering. When a $1{\times}32$ optical coupler is used, only 25 out of 32 output ports can be used to monitor the water level.

• Proceedings of the Korean Nuclear Society Conference
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• 한국원자력학회 2001년도 춘계학술발표회요약집
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• pp.225.2-225
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• 2001

• Proceedings of the Korean Nuclear Society Conference
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• 한국원자력학회 2002년도 춘계공동학술발표회요약집
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• pp.171.1-171
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• 2002

• Korean Journal of Food Science and Technology
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• 제35권5호
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• pp.835-840
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• 2003

Micron-sized alginate microparticles were formed in the water pools of reverse micelles (RM) composed of hexane/aerosol OT(AOT)/water through the gelation process between sodium alginate and $CaCl_2$. The size of microparticles formed increased as Wo (the molar ratio of water to surfactant) increased from 5 to 10. The microparticles became aggregated at Wo of 15, and stable RM no longer existed at Wo of 20. The characteristics of microparticles prepared at Wo of 5 and 10 showed significant differences in area, maximum diameter, minimum diameter, mean diameter, and perimeter of microparticles (p<0.05). However, there was no difference in appearance and roundness between the microparticles These results indicate that the size of microparticles are affected by Wo, whereas the overall shape of microparticles are not substantially influenced within Wo values used for stable RM formation. The mean diameter of microparticles was about $2{\sim}2.5\;{\mu}m$ and much smaller $(70{\sim}1,000\;times)$ than the reported sue of alginate microparticles formed in an aqueous medium.

• Journal of the Korean Society of Environmental Restoration Technology
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• 제20권1호
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• pp.55-75
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• 2017

The purpose of this study is to present the basic data for restoration of physical stream environment by analyzing habitat variables because habitat environment is changed due to the construction of waterfront space in urban streams. Assessment results of 10 habitat variables(three divisions) were almost same as optimal condition, in the reach of reference stream where there are no stream crossing structures and channel alteration. Assessment results of reaches in urban rivers, where streams were improved on water-friendly recreation activities, appeared to be marginal condition. Because habitat environment got worse due to stream improvement works such as construction of weir for water landscape, stepping stones for walking, low water revetment and high water revetment, and high water channel. In addition, in the case of mid gradient stream, the frequency of riffles was small or not existed because the intervals of the river crossing structures was short. In the case of mild stream types, the diversity of the pool was damaged due to the deposition of sludge in the upstream pool of weir and the installation of low water revetment.