• 설비공학논문집
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• 제8권4호
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• pp.451-462
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• 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.

• 한국과학교육학회지
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• 제10권2호
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• pp.11-24
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• 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.

• 대한기계학회논문집
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• 제18권4호
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• pp.903-911
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• 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 $21, 800kW/m^3\cdotK$.

• 물과 미래
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• 제6권1호
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• pp.87-99
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• 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.

• 한국초등수학교육학회지
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• 제18권3호
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• pp.379-397
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• 2014

칸트에 의하면 인간은 현상을 시간의 틀 속에서 수용한다. 이로부터 시간적 현상의 무시간화와 무시간적 현상의 시간화라는 이해의 두 차원을 추출할 수 있다. 이 논문에서는 무시간적인 현상의 시간화와 시간적 현상의 무시간화가 수학적 지식 이해의 문제를 논하는 하나의 관점이 될 수 있음을 몇 가지 예를 들어 고찰한다. 먼저 무시간적 현상의 시간화의 의의를 수식과 도형을 예로 하여 고찰한다. 이어서 시간적 현상의 무시간화의 의의를 자연수의 합, 패턴, 확률 등을 예로 하여 고찰한다. 이러한 고찰을 바탕으로 수학교육에서 무시간적 현상을 시간화하여 이해하려는 성향과 시간적 현상을 무시간화하여 이해하려는 성향의 함양이 중요함을 논한다.

• 대한간호학회지
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• 제8권1호
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• pp.85-98
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• 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.

• 대한기계학회논문집B
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• 제20권10호
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• pp.3313-3321
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• 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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.101-106
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• 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.

• 한국과학교육학회지
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• 제41권1호
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• pp.47-57
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• 2021

본 연구에서는 학습자의 인식적 행위주체성을 촉진하기 위하여 인식적 목표를 명시화하는 지식 구성 활동을 설계하여 초등 예비교사를 위한 생물학 강좌에 도입하였고, 이 활동에 참여한 예비교사들이 어떠한 유형의 인식적 목표를 어떻게 고안하였으며, 이 목표를 중심으로 정교한 수준의 인식적 특성을 지닌 지식 구성 활동이 형성되도록 촉진하거나 이를 제한한 요인을 탐색했다. 이를 위해 활동에 참여한 예비교사들의 실행 및 산출물을 녹음 및 수집했으며, 녹음 자료는 전사하여 본 연구의 분석 자료로 활용하였다. 분석 결과, 예비교사들이 고안한 인식적 목표의 유형은 '자연 현상에 대한 의미 형성하기', '실용적 선택안 제시하기', '문제 현상의 기작에 기반한 해결책 제시하기'로 도출되었다. 각 인식적 목표 유형은 예비교사들이 탐구하기로 선정한 자연 현상에 대한 지식을 바탕으로 어떠한 결론을 얻고자 하는가에 따라 서로 다르게 고안되었다. 예비교사가 인식적 목표를 명시화하는 활동 구조는 이들이 근거 기반의 지식 주장 정당화가 수반되는 지식 구성 활동을 고안하도록 촉진할 수 있는 것으로 분석되었다. 예비교사가 고안한 지식은 지식의 본성 측면에서 주로 현상에 관한 기술에 그쳤으며, 현상의 기작에 관한 설명 구성은 자연 현상이 일어나는 기작에 대한 의미를 형성하고자 하거나 현상의 기작에 대한 이해를 바탕으로 문제해결을 위한 해결책을 제시하고자 계획할 때 나타났다. 그러나 예비교사들이 활용 가능한 시간적·물리적 자원의 한계에 따라 기작에 대한 설명 산출 과정에서 정교한 수준의 인식적 특성을 지닌 지식 구성 활동이 제한될 수 있는 것으로 분석되었다. 본 연구는 학습자의 인식적 행위주체성을 촉진하는 교수학습 전략의 고안 및 인식적 행위주체성을 중심으로 한 예비교사 교육에 대한 논의에 기여할 수 있을 것으로 기대한다.

• 대한기계학회논문집
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• 제17권9호
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• pp.2280-2285
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• 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.