• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.49-55
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• 2018

Under the era of energy crisis, hydrogen energy is considered as one of the most potential alternative energies. Liquid hydrogen has much higher energy density per unit volume than gas hydrogen and is counted as the excellent energy storage method. In this study, Navier-Stokes equations based on 2-phase model were solved by using a computational fluid dynamics program and the liquefaction process of gaseous hydrogen passing through a cryogenic cooling tube was analyzed. The copper with high thermal conductivity was assumed as the material for cryogenic cooling tube. For different inlet velocities of 5 m/s, 10 m/s and 20 m/s for hydrogen gas, the distributions of fluid temperature, axial and radial velocities, and volume fractions of gas and liquid hydrogens were compared. These research results are expected to be used as basic data for the future design and fabrication of cryogenic cooling tube to transform the hydrogen gas into liquid hydrogen.

• Journal of Science Education
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• v.35 no.1
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• pp.23-33
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• 2011

The purposes of this study were to analyze the effects on scientific creativity of the Science Gifted Program, to survey recognition of gifted learners on the Program, and to obtain implications for the development direction of guidance program. The subjects of this study were 20 persons of the class for the gifted in an elementary school science, which belonged to Education Institute for the Gifted, Office of Education in Jeju city. The Science Gifted Program were applied during 28 times. The effects of the program were analyzed using the scientific creativity test, recognition questionnaire and interview of the Science Gifted Program. The results of this study were as follows. First, after applying Science Gifted Program, the scientific creativity of the gifted in science was enhanced. Especially, fluency was enhanced most remarkably. Second, after applying Science Gifted Program, students stated that they had the positive feeling about this program. The suggestions of results of recognition questionnaire of the Science Gifted Program were as follows. First, the Science Gifted Program must include experiment and research of subject. Second, it is necessary to guide concretely of the learning method before beginning of the Science Gifted Program. Third, it is necessary to control content level and quantity of the task for the student's easy comprehension.

• Korean Journal of Heritage: History & Science
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• v.48 no.4
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• pp.4-23
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• 2015

Buried bronze objects are naturally corroded by their surrounding environment, which results in producing corrosion layers containing a number of constituents. Corrosion layers in stable condition protect the objects from the environment and also could provide information in terms of the objects. Characteristic and mechanism of the corrosion layers is likely to be valuable information for the conservation treatment. Many research have been conducted to figure out the formation and characteristic of the corrosion layers, but the more research should be conducted with various approach and analytical methods. Raman spectroscopy is one of the analytical methods to identify microcrystal as a compound while other analytical methods are used to identify element. Therefore, the aim of this research is to identify the characteristic of corrosion layers of both excavated bronze objects through the raman spectroscopy. Two analytical methods, which are raman spectroscopy and SEM~EDS, were used to analyse four excavated bronze bowls. In the case of bronze bowls, malachite was found from the exterior corrosion layer and albite, quartz, and microcline, which are minerals, were also found. Cuprite was detected from the interior corrosion layers illustrating slightly different spectrum due to the combined compound. Lead segregation shows the form of PbO, $PbSO_4$ and $PbCO_3$ or it replaced as cuprite. In this study, small number of samples were analysed. This research is likely to be useful information to figure out not only the characteristic of the corrosion layers but also the authenticity of the artifacts if relevant research will be conducted. Therefore, further comprehensive researches on the various archaeological objects and corrosion environment condition are required in the future.

• Korean Journal of Environment and Ecology
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• v.36 no.5
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• pp.460-467
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• 2022

In this study, we collected snake roadkill data from 2006 to 2017 and developed a species distribution model to identify the pattern of snake roadkill and predict the potential hotspot of snake roadkill in the Odaesan National Park of South Korea. During the study period, snake roadkills occurred most frequently on the road, which passes through between forest and stream at an altitude of about 600 m. The modeling result showed that the occurrence probability of snake roadkill was high on a road with a gentle slope at a distance of 25 m from the stream and an altitude of 600 m. The most susceptible regions for snake roadkill in the Odaesan National Park were located on National Route 6, about 2.2 km and 11.7 km away from the southern border of the park, and on Local Road 446, 3.44 km away from the southern border of the park. The results of this study suggest that providing alternative basking places and eco-corridors and installing protection fences that block the inflow of snakes into roads, preferentially around roads and streams at an altitude lower than 700 m would be an effective way of reducing snake roadkill in the Odaesan National Park.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1B
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• pp.35-45
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• 2009

In this study, a laboratory experiment has been performed on a S-curved channel with two curved sections. In the experiments, effects of 3-D velocity structures on mixing characteristics of tracer material were investigated. As a result, it was clearly noticed that the primary flow travels taking the shortest course of the meandering channel and has a very ununiform distribution at the bends. The secondary cell which was developing at the first bend disappears at the crossover, and then, at the next bend, secondary cell is re-developing in the opposite direction. The experimental results show that mixing of tracer is significantly affected by the combined action of ununiform primary flow and secondary cell. The ununiform primary flow separates the tracer cloud in the longitudinal direction, and the secondary cell further separates the retarding tracer cloud mainly in the transverse direction. As a result, these complex flow structures cause separation and spreading of tracer cloud both in the longitudinal and in the transverse directions. The measured dimensionless transverse dispersion coefficients calculated using 2-D routing procedure ranges 0.012-0.875, and is generally proportional to width to depth ratio (W/h). The predicted values calculated by the theoretical equation overestimate slightly the measured transverse dispersion coefficients.

• Journal of The Korean Association For Science Education
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• v.27 no.1
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• pp.59-69
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• 2007

The aim of this study was to investigate teachers' perceptions on MBL (microcomputer-based laboratory) experiment training program for teachers, the expecting effects of MBL experiment and application of MBL experiment after conducting MBL experiment training for science classes in schools. This study showed that most of the teachers who participated in the training program thought that the MBL experiment training program was very useful and instructive. Many teachers considered that MBL experiments using a computer could decrease time spent in the experiment by accurate and fast data collection and analysis. They also thought that the reduced time could be used more effectively in the analysis of experimental data and discussion activities leading to correct concept formation as well as in the development of graphical analysis and science process skills. However, they thought that MBL experiments were ineffective in learning how to operate experiment apparatus. This study also revealed that most teachers intended to apply MBL experiments in real classrooms context right after the training course and they pointed out many obstacles in introducing MBL experiments into their classrooms such as a budget to purchase equipment, poor laboratory conditions, and few MBL experiment training opportunities. In order to apply MBL experiment into the real classrooms, further changes were suggested as follows; development of technologies to reduce unit cost of equipment for MBL experiments, production and supply of many kinds of sensors, development of MBL experiment materials, and expansion of the training program for teachers.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.1
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• pp.68-75
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• 2016

This study was conducted to provide information regarding changes in antioxidant activity in response to conching temperatures, conching times, and cacao mass content (CMC) in dark chocolate. The radical scavenging activities and functional components of cacao nibs were highest for raw cacao nib (R0) under all conditions. Moreover, antioxidant activities and functional compounds increased during roasting for 25 min. As the conching temperature increased, the radical scavenging activities and functional components increased. Quantitative analysis of major catechin-derived compounds by HPLC revealed that R0 had the highest value for other roasted cacao nibs in all aspects (P<0.05). The content of procyanidin B2, catechin, and epicatechin increased during roasting for 25 min. Finally, evaluation of couvertures revealed that procyanidin B1 content increased as conching time increased to 48 h, except for 70% CMC and conched at $60^{\circ}C$ (HH) and 70% CMC and conched at $50^{\circ}C$. Overall, HH48 contained the richest catechin-derived components.

• Journal of Korean Home Economics Education Association
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• v.19 no.3
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• pp.169-183
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• 2007

The purpose of this study is to examine the effects of self-esteem, relationships with parents and peer relationships on adolescents' school adjustment. Total of 900 middle school students residing in Guri, Geonggi-Do participated in the survey and the data collected from 874 students (557 male and 317 female students) were analyzed for this study. The followings summarize results of the study. First, the findings suggested that there is no significant difference between female and male students in school adjustment. Secondly, the study revealed that there is no difference between female and male students in self-esteem and relationship with parents. Thirdly, this study provided clear evidence that students with high self-esteem and close relationship with parents and schoolmates adapt to school life better than those with low self-esteem and distant relationship with parents and schoolmates. Fourthly, students with high self-esteem and close relationship with parents and schoolmates displayed higher adaptability to school life, and as for male students, close relationship with schoolmates was the most prominent factor which helps them adapt to school life better while female students' adaptability to school lifewas mainly affected by relationship with parents.

• Korean Journal of Agricultural and Forest Meteorology
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• v.24 no.2
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• pp.63-77
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• 2022

Our aim was to reduce estimation errors of a wind velocity model used as an early warning system for weather risk management in the agricultural sector. The Rural Development Administration (RDA) agricultural weather observation network's wind velocity data and its corresponding estimated data from January to December 2020 were used to calculate linear regression equations (Y = aX + b). In each linear regression, the wind estimation error at 87 points and eight time slots per day (00:00, 03:00, 06:00, 09.00, 12.00, 15.00, 18.00, and 21:00) is the dependent variable (Y), while the estimated wind velocity is the independent variable (X). When the correlation coefficient exceeded 0.5, the regression equation was used as the wind velocity correction equation. In contrast, when the correlation coefficient was less than 0.5, the mean error (ME) at the corresponding points and time slots was substituted as the correction value instead of the regression equation. To enable the use of wind velocity model at a national scale, a distribution map with a grid resolution of 250 m was created. This objective was achieved b y performing a spatial interpolation with an inverse distance weighted (IDW) technique using the regression coefficients (a and b), the correlation coefficient (R), and the ME values for the 87 points and eight time slots. Interpolated grid values for 13 weather observation points in rural areas were then extracted. The wind velocity estimation errors for 13 points from January to December 2019 were corrected and compared with the system's values. After correction, the mean ME of the wind velocities reduced from 0.68 m/s to 0.45 m/s, while the mean RMSE reduced from 1.30 m/s to 1.05 m/s. In conclusion, the system's wind velocities were overestimated across all time slots; however, after the correction model was applied, the overestimation reduced in all time slots, except for 15:00. The ME and RMSE improved b y 33% and 19.2%, respectively. In our system, the warning for wind damage risk to crops is driven by the daily maximum wind speed derived from the daily mean wind speed obtained eight times per day. This approach is expected to reduce false alarms within the context of strong wind risk, by reducing the overestimation of wind velocities.

• Economic and Environmental Geology
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• v.46 no.4
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• pp.313-327
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• 2013

In the study, three-dimensional geostatistical simulations on McMurray Formation which is the largest oil sand reservoir in Athabasca area, Canada were performed, and the optimal site for steam assisted gravity drainage (SAGD) was selected based on the predictions. In the selection, the factors related to the vertical extendibility of steam chamber were considered as the criteria for an optimal site. For the predictions, 110 borehole data acquired from the study area were analyzed in the Markovian transition probability (TP) framework and three-dimensional distributions of the composing media were predicted stochastically through an existing TP based geostatistical model. The potential of a specific medium at a position within the prediction domain was estimated from the ensemble probability based on the multiple realizations. From the ensemble map, the cumulative thickness of the permeable media (i.e. Breccia and Sand) was analyzed and the locations with the highest potential for SAGD applications were delineated. As a supportive criterion for an optimal SAGD site, mean vertical extension of a unit permeable media was also delineated through transition rate based computations. The mean vertical extension of a permeable media show rough agreement with the cumulative thickness in their general distribution. However, the distributions show distinctive disagreement at a few locations where the cumulative thickness was higher due to highly alternating juxtaposition of the permeable and the less permeable media. This observation implies that the cumulative thickness alone may not be a sufficient criterion for an optimal SAGD site and the mean vertical extension of the permeable media needs to be jointly considered for the sound selections.