• Journal of the Korean Society of Visualization
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• v.15 no.3
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• pp.20-26
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• 2017

The two-fluid equations are widely used to simulate two-phase flows in a nuclear reactor. For the two-fluid momentum equation, the wall and interfacial drag terms play an important role in predicting a two-phase flow behavior. Since the bubble density is much smaller than the water density, the bubble accelerates faster than the liquid in a nozzle. As a result, the bubble phase becomes faster than the liquid phase in the nozzle. In contrast, the opposite phenomena occur in the diffuser. The purpose of our study is to experimentally show these behaviors in an area-varying channel such as nozzle and diffuser. Experiments were made of turbulent bubbly flows in an area-varying horizontal channel. The velocities of the bubble and liquid phases were measured by the PIV technique. It was shown that the two-phase velocities were no longer close to each other in the area-varying regions. The bubble was faster than the liquid in the nozzle; in contrast, the bubble was slower than the liquid in the diffuser. Code simulations were also performed using the MARS code. By replacing the original wall drag model in the MARS code with Kim (1)'s wall drag partition model, we obtained the simulation results being consistent with experimental observations.

• Imaging Science in Dentistry
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• v.42 no.1
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• pp.5-12
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• 2012

Purpose : This study was performed to evaluate possible variations in maxillary and mandibular bone texture of normal population using the fractal analysis, particles count, and area fraction in intraoral radiographs. Materials and Methods : Periapical radiographs of patients who had full mouth intraoral radiographs were collected. Regions of interest ($100{\times}100$ pixels) were located between the teeth of the maxillary anterior, premolar, and molar area, as well as the mandibular anterior, premolar, and molar areas. The fractal dimension (FD) was calculated by using the box counting method. The particle count (PC) and area fraction (AF) analyses were also performed. Results : There was no significant difference in the FD values among the different groups of age, gender, upper, and lower jaws. The mean FD value was $1.49{\pm}0.01$. The mean PC ranged from 44 to 54, and the mean AF ranged from 10.92 to 11.85. The values of FD, PC, and AF were significantly correlated with each other except for the upper molar area. Conclusion : According to the results, patients with normal trabecular pattern showed a FD of approximately 1.5. Based on these results, further investigation would be recommended if the FD value of patient significantly differenct from this number, since the alteration of this value indicates microstructural modification of trabecular pattern of the jaws. Additionally, with periapical radiographs, simple and cost-effective, PC and AF could be used to assess the deviation from the normal.

• Journal of Korean Society of Forest Science
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• v.94 no.3 s.160
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• pp.129-134
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• 2005

Ths study was carried out to understand the geo-topographical characteristics of the landslide area (1.5 ha) in Maeri, Sangdong-myeon, Gimhaesi, Gyeongsangnam-do. The bedrock of the landslide area was diollites and the area in and around the upper slope with the scattered talus was composed of Masanam originated from Igneous rocks. The landslide occurred in 19th of April, 2004 and the amount of rainfall for 3 days before the landslide was 74mm. The landslide by land creeping in this area was mainly attributed to geo-topographical characteristics such as well developed colluvial and/or weathered soils, and land cutting in lower slope, although the landslide could be affected by the rainfall. The type of the landslide can be classified into the land creeping by concave colluvial soils.

• Journal of Elementary Mathematics Education in Korea
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• v.5 no.1
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• pp.55-75
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• 2001

The purpose of this paper is to find out the full extent of abilities of elementary students on area of operations and the effects on student's affective domain toward mathematics, after providing 3rd grade students with Skemp's play activities instead of providing activities suggested in the textbook of 7th curriculum. For this study, we will first analyse new elementary mathematics curriculum of 3rd grade and then explore mathematical factors for play activities related to operational sections. The play activities are revised from that of Skemp's for our classroom circumstances, but the ideas included from Skemp's such as thinking aloud were not changed. The experimental group while consists of 39 students were taught Skemp's play activities instead of usual textbook activities for 30 hours for the second term. In all other area, both the experimental group and the comparative group were taught the same contents. Statistical data is as follows 1) In addition and subtraction, the experimental group had 5.6% higher score than the comparative's, but the difference of mean of the both groups is not significant within 5% level. 2) In multiplication and division, the experimental group had 7.8% higher score than the comparative's and also the difference of mean of the beth within 5% level is significant. 3) When measured the effects in affective domain, the interests, attitude, and values for mathematics had about 10% higher score after the experiment than before the experiment. So we conclude that Skemp's activities are more effective than the activities suggested in the textbook on the area of operations, especially in multiplication and division.

• Journal of Navigation and Port Research
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• v.34 no.6
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• pp.493-501
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• 2010

In the central Busan area from Haeundae to Saha, fishing villages are vanished actually in the progress of urbanization, and 17 fishing ports surrounded by urbanized area are left alone and isolated. But, we think these urbanized fishing ports are the very resource which grant the identity as the marine city and they have considerable potentials to enhance the value of neighboring community depending on the proper development of it. In this study, we defined the fishing ports in central Busan area as the representatives of 'urban fishing port', and tried to find the way of coexistence and harmony between 'city' and 'fishing port'. For this purpose, we investigated the fishery potentials, physical environments and development demands of 17 fishing ports in central Busan area, and composed opinions from fishing communities and neighboring inhabitants to set up the long term directions of urban fishing ports development for harmonious coexistence of city and fishing port.

• Journal of Korea Water Resources Association
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• v.41 no.6
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• pp.575-585
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• 2008

It is essential to obtain accurate and highly reliable streamflow data for water resources planning, evaluation and management as well as design of hydraulic structures. A new discharge computation method proposed in this research uses Chiu's velocity distribution and estimation of maximum velocity. This method shows acceptable channel discharges comparing these by the exiting velocity-area method. When velocity-area method is used, it is required to observe velocities at every specified point and vertical line using a velocity meter like Price-AA. If the method proposed in this research, is used, however it is not necessary to observe all point velocities needed in the velocity-area method. But this method can not be applied for the cases of very complex and strongly asymmetric channel cross-sections because Chiu's velocity distribution using entropy concept may be quite biased from that of natural rivers.

• Journal of Korean Society of Forest Science
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• v.95 no.3
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• pp.240-249
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• 2006

Recently, dispersion of damaged forest by pine wilt disease has been regarded as a serious social issue. Damages by pine wilt disease have been spreaded by natural area expansion of the vectors in the damaged area, while the national wide damage spread has induced by human-involved carrying infected trees out of damaged area. In this study, damaged trees were detected and located on the digital map by aerial photograph and terrestrial surveys. The spatial distribution pattern of damaged trees, and the relationship of spatial distribution of damaged trees and some geomorphological factors were geostatistically analysed. Finally, we maked natural spread pattern map of pine wilt disease using geostatistical CART(Classification and Regression Trees) model. This study verified that geostatistical analysis and CART model are useful tools for understanding spatial distribution and natural spread pattern of pine wilt diseases.

• Journal of Environmental Impact Assessment
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• v.22 no.5
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• pp.491-511
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• 2013

In this study, three survey areas in Changnyeong, Miryang and Jinju of the confirmed the habitation of nutria and carried out the performance on the plant diet resource. From the habitat trace survey in the nutria habitat, a total of 336 trace points was shown. There were 181 trace points (54%) confirmed from St. 1 as the highest showing, followed by 52 trace points (15.4%) from St. 2, and 103 trace points (30.6)% from St. 3. The vascular plants distributed in the habitat area were a total of 182 taxonomic group with 57 families, 99 genus, 16 hybrids, and 1 race. The vascular plant living types in the habitat area are 1-year plant (Th, Th(w)) for 63class groups (34.6%), hemicryptophyte (H) for 42class groups(23.1%). plants, trees, crop plants were included. As a result of analyzing the overseas research cases on the diet plants of nutria, there are 195 taxonomic groups in a total of 39 families, 126 genus, 183 breeds, and 12 hybrids. In the study areas, feeding the plants was confirmed by the 7 taxonomic groups, aquatic plant, terrestrial From the total of 182 taxonomic groups discovered in the habitat area, 20 class groups, in 3 habitation region, 10 class groups of commonly appearing 49 class groups were shown to be the breed confirmed for diet in existing case studies, and assuming from it basis, the nutria habitating in the survey area is considered to have the supply of diverse diet resource to have flawless habitation. This is implication of having potential breeding possibility.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.21 no.1
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• pp.55-71
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• 2018

To improve the ecological function of urban areas, the guideline for applying the Biotope Area Ratio to the Environmental Impact Assessment (EIA) was developed in 2005 and modified in the July, 2017. This study investigates whether the guideline has been actually practiced in the real world by searching reports including 648 cases of the Strategic Environmental Impact Assessment (SEIA) and 471 cases of the EIA. The results show that the 38% of SEIA and the 43% of EIA include sections about Biotope Area Ratio, and the 15% of SEIA and the 25 % of EIA are satisfied the threshold of the Biotope Area Ratio suggested by the guideline. The statistical analysis results show that this low level of practice was not improved through the modification of the guideline in 2017. This is because the guideline is forcibleness, its explanation is unclear, and stockholders' understanding of it lacks. In addition, lack of tracking management on SEIA and EIA also contributes to the low level of practice of the guideline. To promote the practice, the efforts to legislate and publicize the guideline are required.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.1
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• pp.88-91
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• 2016

In this paper, we have proposed the frequency interference analysis system using both LabVIEW and Universal Software Radio Peripheral(USRP) for performance degradation analysis of Multi Input Multi Output-Orthogonal Frequency Division Multiplexing(MIMO-OFDM) Wireless Local Area Network(WLAN) due to Wireless Local Area Network(WPAN) interferer. The proposed system consists of three part, i.e., victim, channel, and interferer. Both victim and interferer are implemented by LaBVIEW and a USRP board. Then interfering signal and additive white Gaussian noise are combined with the wanted signals of a victim. Measured Bit Error Rate(BER) at the victim receiver is compared with theoretical BER according to various signal to interference plus noise power ratio (SINR) values. Measured and theoretical BER curves show good agreement.