• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.8 no.4
• /
• pp.451-462
• /
• 1996

In this study, which focuses on ice storage, a fundamental study in cooling and solidification was performed, including the interesting phenomena of density inversion, supercooling and dendritic ice. A numerical study was performed for natural convection and ice formation considering existence of subcooling and dendritic ice were analyzed numerically by using finite difference method and boundary fixing method. In the mesh, the solid fraction was introduced with adding as a term to the energy conservation equation. A flow in the dendrite was modelled as a flow in a porous medium, and the momentum conservation equation was modified to incorporate resistance forces involved in flows through porous media. A numerical solution of the time dependencies of dendrite area and dense ice front was successfully obtained, and the numerical results were good agreement with experimental results. Based on this methodology, a discussion was made of phenomena and characteristics of cooling and freezing processes under various conditions.

• Journal of The Korean Association For Science Education
• /
• v.10 no.2
• /
• pp.11-24
• /
• 1990

The objectives of this study are to find out the research methodology about misconception, the types of scientific concepts to be misconcepted the analysis methodology of causes of misconception, and remediation methodology of misconception. The research methods of this study are descriptive ques tionnare, interview, classroom observation and curriculum analysis. The results of this study are: ${\circ}$ The descriptive questionnaire is sufficient to obtain children's ideas. ${\circ}$ The types of science concepts to be misconcepted are 'the invisible natural phenomena,' 'the vague Understanding', 'the contents of teachers' lecture', 'the lack of children's cognitive development,'and 'the influence of nursery stories.' ${\circ}$ The Cause analysis methods of misconception are that the analysis of the cognitive level of the questionnaire items, the examining the item concepts are taught or not and the investigation about the agreement of the cognitive level of the questionnaire item and children. ${\circ}$ Remediation methods are visualijation and instrustion of invisible natural phenomena, concrete presentation of the scientific concepts, and acceleration of the cognitive development.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.4
• /
• pp.903-911
• /
• 1994

This study addresses the phenomena of bubbling, icing, eruption, component varieties of the evaporated natural gas, and volumetric heat transfer coefficients obtained during the operation of a proposed LNG evaporator between LNG and water in direct contact. In the present investigation, the explosive and eruption phenomena within the water column were not observed during the entire operation of the heat exchanger. Compared with the natural gas produced by conventional LNG evaporator, the analysis of the gas produced by the direct contact LNG evaporator shows that nitrogen, methane, and ethane components were reduced by 0.002~0.007mol%(4~14%), 1.6~1.92mol%(1.9~2.3%) and 0.17~1.28mol%(1.1~8.4%) respectively, while the moisture content was rather increased by 0.51~0.76mol%. The maximum volumetric heat transfer coefficient of the direct contact heat exchanger was found to be $21, 800kW/m^3\cdotK$.

• Water for future
• /
• v.6 no.1
• /
• pp.87-99
• /
• 1973

The calculation of the comsumptive use by crop can be most accurate when it is actually measured. The mankind is not yet able tole grasp all the natural conditions or phenomena. The induces of actual measurement at a representive observatory and the formula abtained from the area werowere made as close as possible, which is called as the Blaney Criddle formcula, published in 1945. In calculating the water require-ment of consumptive use of water by farm crops, a more accurate and reasonable formula should be induced as the factors other than temperature and day-time hours according to the location of project area have also influences. The formula of Mr. Jerald E. Christianen published in 1969 is based on the induces of the records of actural measurements for 3, 928 months at 80 different stations and his formula couers a wider range of functions that calculate water requirement to induce the functions of moisture, wind, velocity, sunshine at elevatons, in addition to temperature and daytime hours in accordance with latitude and was modified to be fit to natural phenomena. The formula is being widely in use in many contries with their modification since it is worth while for usealso in korea, the formula is introduced and explained in the following.

• Journal of Elementary Mathematics Education in Korea
• /
• v.18 no.3
• /
• pp.379-397
• /
• 2014

According to Kant, time is integral to all human cognitive experiences. Human beings perceive things in the frame of time. Phenomena are perceived in successive way or in coexistent way. In this paper, I argue that the perspective of temporality and atemporality can be a framework to consider the issues of teaching and understanding of mathematical knowledge. Significance of temporal inquiry of atemporal phenomena is discussed with examples of mathematical expressions and geometric figures. Significance of atemporal inquiry of temporal phenomena is also discussed with examples of the sum of natural numbers, geometric pattern, and the probability of two events. Teachers should understand the potential of mathematical tasks from the perspective of temporality and atemporality and provide students with opportunities to inquire temporal phenomena atemporally and atemporal phenomena temporally.

• Journal of Korean Academy of Nursing
• /
• v.8 no.1
• /
• pp.85-98
• /
• 1978

This study was designed to investigate the elderly people's attitude toward death for the purpose of identifying the issues needed in the planning of health management and care activities for the aged. The total number of subjects in this study was 354 elderly people who were accommodated in house for elderly people (185) and school for elderly people (169). The scale for the attitude toward death of aged persons as an instrument of this study was mainly constructed with reference to Schneidman's attitude questioners toward death modified of adjust the Korean cultural characteristics and attitudes concerning death. Theresultsofthisstudywereasfollows: - 1. Out of total 45.8% of the respondents consider that death is a natural phenomena and ending of life. The responses on the meaning of death appeared differently : non-religions (48.1%) and oriental religions (50.3%) consider death as a natural phenomena however western religions (47.4%) consider that death is God's call. This difference was statistically significant. (x$^2$= 56.6419. df = 10. p<0.01). Respondents with a spouses (52.4%) think death is a natural phenomena opposed to respondent without spouses (33.3%). This was statistically significant. (x$^2$= 14.7134. df= 5 p<0.05). 2. Respondents in the house for aged persons (51.9%) replied. They do not wanted death because it meant a separation from their family as compared to those from school for aged persons (26.0%). 57.9% responded that they want to be told when death is confronted. 3. 51.2% of the respondents replied that the main factor to influence their attitude toward concept of death was the dying of their friends & relatives. 79.9% of respondents expressed that wished to die. The main reason for dying was economic shortage (28.3%). 4. 70.1% of the respondents want their body to be hurried while only 1.1% of the respondents want to donate their body to a medical research. 5. Over two thirds of the respondents replied that they do not believe in a life in heaven or that they will be rebirth. 6. The questioners of this study stimulated 56.8% of the respondents to feel that they should spend the leu of their life more effectively and 15.5% of the respondents felt it gave them the opportunity to think about their death seriously.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.10
• /
• pp.3313-3321
• /
• 1996

A fundamental study in cooling and solidification process focused on ice storage was performed, including the interesting phenomena of density inversion, supercooling and dendritic ice. A numerical study was performed for natural convection and ice formation in the cooling and freezing processes with supercooling in a space between double cylinders. When water was cooled under the freezing point by a cooling wall in a cavity, solidification was not started at once, but a subcooled region was formed near the wall. Especially, when the cooling rate was low, subcooled region extended to a wide area. However, after a few minutes, supercooling is released by some triggers. Dendritic ice is suddenly formed within a subcooled region, and a dense ice layer begins to be developed from the cooling wall. Due to the difficulties, most previous studies on solidification process with numerical methods had not treated the supercooling phenomena, i.e. the case considering only the growth of dense ice. In this study, natural convection and ice formation considering existence of supercooling and dendritic ice were analyzed numerically with using finite difference method and boundary fixing method. The results of numerical analysis were well compared with the experimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2011.10a
• /
• pp.101-106
• /
• 2011

In the present paper, the phenomena of abnormal noise and vibration due to acoustic resonance of CFBC(Circulating Fluidized Bed Combustion) boiler was presented. The acoustic resonance which occurred in the gas path of CFBC boiler system was caused by coincidence of vortex shedding frequency of tube bank and acoustic natural frequency of duct and hopper. And, the phenomena of beating arose from the interference of two closed resonant waves at 66.4Hz and 70.8Hz. There are two control methods for acoustic resonance in this system. The first method is to change the vortex shedding frequency from the structural alterations on the tube bank. And the second method is to change the acoustic natural frequency of the gas path with the installation of anti-noise baffles. The second one which is relatively easy to apply, was adapted in this study. As a result, the noise and vibration level have been decreased by 41dB and 94% at 66.4Hz, respectively. And the improvement of noise and vibration at 70.8Hz was identified by sensory evaluation.

• Journal of The Korean Association For Science Education
• /
• v.41 no.1
• /
• pp.47-57
• /
• 2021

This study aims to explore the epistemic goals that pre-service elementary teachers can construct in their biology-related knowledge construction activities, how these goals are constructed, and how the shaping of the knowledge construction activities around the goals was afforded or constrained. The research participants were 26 pre-service teachers, divided into 11 groups of two or three to engage in the activity. Their discussions and products were collected and used as data for this study. The analysis revealed that the teachers constructed three types of epistemic goals: making sense of natural phenomena, proposing the most effective course of action, and proposing solutions to problems based on their causes. Construction of different types of goals depended on the conclusions the pre-service teachers expected to draw based on the explored natural phenomena. It was found that the elicitation of the pre-service teachers' epistemic goals could facilitate their shaping of the knowledge construction activity as an evidence-based justification. The participants planned the construction of mechanistic explanations of natural phenomena with the epistemic goals of 'making sense of natural phenomena' or 'proposing solutions to problems based on their causes.' However, enacting their knowledge construction plans with sophisticated epistemic features was constrained due to the limited resources available. This study can contribute to developing instructional strategies that facilitate learners' epistemic agency and addressing epistemic agency in the development of pre-service teacher education methods.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.9
• /
• pp.2280-2285
• /
• 1993

Many items, as internal pressure, thrust, temperature, strain, etc. are measured in Ground Firing Test (GFT) of rocket motors. But these items are influenced by various phenomena occurred during propellant combustion. In this study, natural frequencies of motor itself and system(motor+loadcell) on Stand were measured. Also motor responses were measured during burning and analyzed so that the vibration characteristics occurred during GFT and the causes and characteristics of vibration signal appearing on thrust curve were identified.