• Geomechanics and Engineering
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• 제23권2호
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• pp.165-178
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• 2020

This paper investigates the effect of the jaw's curvature, also known by contact angle and jaw arc central angle (2α), of the Brazilian test apparatus on indirect tensile strength of various rock types. That's why, ten rock samples including limestone, marble, skarn, granite, diorite, and granodiorite were collected from some quarries in different provinces of Iran. Petrographic, mineralogical and textural investigations were performed using thin section analyses. Physical properties of the selected rock samples namely dry and saturated unit weights, porosity, water absorption, and specific gravity were determined for the rock samples. In addition, Brazilian tensile strength at different 2α angles (i.e., 2α = 0°, 10°, 15°, 20°, 45°, and 60°) were determined for the rocks in the laboratory. Results show that the parameter for the rocks is between 3.81 MPa at 2α=0° and 54.76 MPa at 2α=60°. This means that Brazilian tensile strength increased with increasing 2α angle from 0° to 60°. Also, it was found that the highest change rate of the Brazilian tensile strength occurs in range of 2α=15°-30° for most studied rock samples. In some tested samples, the parameter is decreased only at 2α = 60°. The values of Brazilian tensile strength of the rocks tested by flat and standard jaws are near to each other.

• 대한기계학회논문집 C: 기술과 교육
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• 제2권2호
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• pp.105-111
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• 2014

지구를 둘러싸고 있는 대기의 하층 부분을 구성하는 기체를 보통 공기라 말한다. 지상 20km 이하에서는 그 성분이 거의 일정한 비율로 존재하며, 질소, 산소, 기타 혼합기체로 구성된다. 공기밀도란 단위 부피 중에 포함된 공기의 질량을 말한다. 공기는 거의 일정한 성분으로 조성된 혼합기체이지만, 수증기는 변동이 큰 성분의 하나이다. 같은 온도, 같은 압력에서는 습공기의 밀도가 건공기의 밀도보다 작다. 보통 밀도는 압력이나 온도 변화에 따라 변화된다. 따라서 풍량 계산에 사용되는 중요 인자인 공기 상태량에 따른 밀도 계산과정과 actual air flow 와 standard air flow 의 관계를 살펴 보고자 한다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.12-16
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• 2002

The clear sky radiative forcings of aerosols were evaluated over East Asia. We first investigated optical characteristics of aerosol using sky radiation measurements. An algorithm of Nakajima et al. (1996) is used for retrieving aerosol parameters such as optical thickness, ${\AA}$ngstr$\"{O}$m exponent, single scattering albedo, and size distribution from sky-radiation measurements, which then can be used for examining spatial and temporal variations of aerosol. Obtaining aerosol radiative forcing at TOA and surface, a radiative transfer model is used with inputs of obtained aerosol parameters and GMS-5 satellite-based cloud optical properties. Results show that there is a good agreement of simulated downwelling radiative flux at the surface with observation within 10 W m$^{-2}$ rms errors under the clear sky condition. However, a relatively large difference up to 40 W m$^{-2}$ rms error is found under the cloudy sky condition. The computed aerosol radiative forcing at the surface shows downward flux changes ranging from -100 to -170 W m$^{-2}$ per unit aerosol optical thickness at 0.7 $\mu$m. The different values of aerosol radiative forcing among the stations is mainly due to the differences in single scattering albedo ($\omega$$_{0.7}$) and asymmetric parameter (g$_1$) related to the geographical and seasonal variations.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.231-236
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• 2000

In order to predict depth of the pile forward modeling and inversion of magnetic logging data was conducted by using a finite line of dipoles model. The horizontal component as well as the vertical component of magnetic fields can be measured in the borehole, and the magnetic anomalies can be obtained by subtracting the Earth's magnetic field from the measurement. The magnetic anomalies of the pile are considered as vector sum of induced magnetization due to the Earth's magnetic field and remnant magnetization possessed by steel strings in the pile. The magnetic anomalies are used as input data for inversion from which the length, the magnetic moment per unit length, and the dip angle of the pile can be obtained. From the inversion of synthetic noisy data, and the data obtained from the field model test it is found that the driving depth of the pile can be determined as close to the order of measuring interval (5∼10㎝). It is also found that the resultant magnetic anomalies due to an individual steel string in the pile are almost same as those due to a group of steel strings located at the center of the pile. The magnetic logging method also can be used for locating reinforced bars, pipes, and steel casings.

• 대한임베디드공학회논문지
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• 제13권5호
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• pp.253-259
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• 2018

Recently, small satellite industries are rapidly changing. Demand for high performance small satellites is increasing with the expansion of Earth Observation Satellite market. A next-generation small satellites require a higher resolution image storage capacity than before. However, there is a problem that the HW configuration of the existing small satellite image storage device could not meet these requirements. The conventional data storing system uses SDRAM to store image data taken from satellites. When SDRAM is used in small satellite platform of a next generation, there is a problem that the cost of physical space is eight times higher and satellite price is two times higher than NAND Flash. Using the same satellite hardware configuration for next-generation satellites will increase the satellite volume to meet hardware requirements. Additional cost is required for structural design, environmental testing, and satellite launch due to increasing volume. Therefore, in order to construct a low-cost, high-efficiency system. This paper shows a next-generation solid state recorder unit (SSRU) using MRAM and NAND Flash instead of SDRAM. As a result of this research, next generation small satellite retain a storage size and weight and improves the data storage space by 15 times and the storage speed by 4.5 times compare to conventional design. Also reduced energy consumption by 96% compared to SDRAM based storage devices.

• 대한지구과학교육학회지
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• 제6권1호
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• pp.13-19
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• 2013

The purpose of this research is to examine the current state of inserting illustrations in science textbooks under the 7th Revised Educational Curriculum which is currently enforced in all grades of elementary schools, and to compare and analyze the external and internal differences in illustrations in science textbooks of elementary schools in Singapore and Korea and to present desirable direction of producing illustrations. There are not only some differences in rate of the kinds and role of the illustrations in grades, but also in both countries. For example, in the case of illustrations for motivation, in both Korea and Singapore, interesting photos related to overall contents with regard to the contents of the unit are used. But in the 3rd and 4th grade class in Singapore, story types of cartoons related to learning subjects are presented to draw students' interest and attention. These need to be considered when developing textbook illustrations in the future.

• 대한지구과학교육학회지
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• 제1권1호
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• pp.99-110
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• 2008

The purpose of this study was to develop an instructional module for creativity(lMC) which was mainly based on a unit ('Sun's family' in the 2nd semester of the 5th grade in the textbook), to verify the effect of this module on Elementary student's creativity and attitudes related to science. The subject in this study was two 5th grade classes from J elementary school located in Busan. One of the group took the lessons which were designed for the IMC, and the other group took the normal classes. The effect of this subject for the experimental group and controlled group was verified by post-test: creativity and attitude related to science. The results of this study are as follows. First, the experimental group showed more creativity than controlled group on the post-test. The IMC was more effective to enhance student's creativity than general class. Second, the IMC was effective to enhance student's creativity without the difference in academic ability level. Third, the IMC was effective to enhance student's creativity without the difference in the gender. Fourth, the IMC was more effective to change student's attitude related to science than general class in the module application.

• 과학교육연구지
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• 제37권2호
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• pp.359-373
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• 2013

본 연구는 초등학교영재를 대상으로 '지구와 달' 단원에 대한 STEAM 교수-학습 프로그램의 개발 및 적용 한 후 효과를 알아보는 것이 목적이다. 개발된 프로그램의 타당도는 3인의 전문가에 의해 검증되었다. 프로그램은 총 8차시로 구성되고, 8일에 나누어 진행 되었다. 녹음 수업, 수업 관찰 일지 및 기록 인터뷰 전사 데이터를 측정 한 후 효과를 분석 하였다. 연구 결과로는 '상황 제시'가 아주 중요한 단계임이 확인되었고, 주어진 상황에 대한 이해의 정도는 작업 약속, 과학적 개념 창조적인 디자인과 산출물의 형성에서 영향이 나타났다.

• 한국초등과학교육학회지:초등과학교육
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• 제18권2호
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• pp.103-117
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• 1999

The importance of pedagogical content knowledge(PCK) has been recognized in learning science teaching. PCK is based partly on the essence of subject matter knowledges. Therefore, the effective teaching of science content knowledges is fundamental in preservice education of student teachers. But, particularly the science curriculum of primary teachers' colleges is composed of less lessons than needed. This research was executed to identify the content and context of earth science which were contained in questions by student teachers These questions which were written by the students about the earth science content in elementary science texts and teachers' guide books were collected and analyzed. Frequency and context concentration of questions about the themes of contents were obtained. In each unit of the text books, scatter diagrams of question frequency and context concentration of themes showed various features. The main results were as follows. first, in case of the units which contents ate composed of themes expected to be experienced in everyday life, the question frequency and context concentration showed positive correlation between them. But, other units, which everyday life experiences are not expected to influence, did not show distinct correlation.

• Structural Engineering and Mechanics
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• 제52권3호
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• pp.559-572
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• 2014

This paper presents the results of an experimental investigation on the flexural behavior of doubly reinforced lightweight concrete (R.L.C.) beams tested under cyclic loading. A total of 20 beam specimens were tested. Test results are presented in terms of ductility index, the degradation of strength and stiffness, and energy dissipation. The flexural properties of R.L.C. beam were compared to those of normal concrete (R.C.) beams. Test results show that R.L.C. beam with low and medium concrete strength (20, 40MPa) performed displacement ductility similar to the R.C. beam. The ductility can be improved by enhancing the concrete strength or decreasing the tension reinforcement ratio. Using lightweight aggregate in concrete is advantageous to the dynamic stiffness of R.L.C. beam. Enhancement of concrete strength and increase of reinforcement ratio will lead to increase of the stiffness degradation of beam. The energy dissipation of R.L.C beam, similar to R.C. beam, increase with the increase of tension reinforcement ratio. The energy dissipation of unit load cycle for smaller tension reinforcement ratio is relatively less than that of beam with higher reinforcement ratio.