• School Mathematics
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• v.9 no.1
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• pp.119-139
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• 2007

The purpose of this study is to analyze students' misconception in the teaming of the conic sections with the cognitive and pedagogical point of view. The conics sections is very important concept in the high school geometry. High school students approach the conic sections only with algebraic perspective or analytic geometry perspective. So they have various misconception in the conic sections. To achieve the purpose of this study, the research on the following questions is conducted: First, what types of misconceptions do the students have in the loaming of conic sections? Second, what types of errors appear in the problem-solving process related to the conic sections? With the preliminary research, the testing worksheet and the student interviews, the cause of error and the misconception of conic sections were analyzed: First, students lacked the experience in the constructing and manipulating of the conic sections. Second, students didn't link the process of constructing and the application of conic sections with the equation of tangent line of the conic sections. The conclusion of this study ls: First, students should have the experience to manipulate and construct the conic sections to understand mathematical formula instead of rote memorization. Second, as the process of mathematising about the conic sections, students should use the dynamic geometry and the process of constructing in learning conic sections. And the process of constructing should be linked with the equation of tangent line of the conic sections. Third, the mathematical misconception is not the conception to be corrected but the basic conception to be developed toward the precise one.

• Explosives and Blasting
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• v.38 no.1
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• pp.30-37
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• 2020

In this study the split ring (SR) test was investigated for its applicability to the measurement of the tensile strength of rock specimen of NX size. The concept of the SR test is the same as the half ring (HR) test (Choi et al., 2019) except that the expected fracture plane is perpendicular to the loading direction. Because of this perpendicularity, however, it was believed that the SR test could be more accurate than the HR test. Like the HR specimen, the SR specimen is a curved prismatic bar with a uniform section. Appealing to a basic bending theory in strength of materials, the tensile strength for the special bar can be calculated analytically. Numerical simulations using LS-DYNA revealed, as expected, that the strength errors were 1% and 5% for the tensional and compressional SR tests, respectively, which were much lower than that (12%) of the HR test. To identify the performance of the two SR tests, laboratory experiments were conducted. The HR and Brazilian tests were also performed for comparison. The experiments showed that the ratios of the tensional and compressional SR to Brazilian strengths were 1.2~1.4 and 1.1~1.2, respectively, which are too small compared to empirical values in ordinary bend tests. Consequently, it is concluded that the SR test is not appropriate for use in tensile strength test of rock specimen of NX size. But the ratio of the HR to Brazilian strengths was within 1.7~2.0 for both the previous and present studies, showing a good consistency in their test results.

• Journal of Gifted/Talented Education
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• v.22 no.3
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• pp.639-662
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• 2012

The purpose of this study is to develop the evaluation model of gifted curriculum in visual art. For this purpose, first, it discusses about what kinds of issues raised about gifted education in visual art. Second, it critically reviews the evaluation models of gifted curriculum, and investigates the suitable model for developing curriculum evaluation model of gifted in visual art. Third, it suggests the appropriate perspective and evaluation model of gifted curriculum in visual art. Along with the change in the concept of creativity, recent studies on gifted education in visual art concentrate that gifted learners who have the potential find their own way of creating art. Also they emphasize the contextual implementation which recognizes the significance of interaction among field, domain and individual. Based of these inquiry, existing evaluation models of gifted curriculum have limitations in suitability as a evaluation model of gifted curriculum in visual art. This study suggests that the curriculum evaluation of visual art gifted programs should be approached from the decision-making perspective. Also it develops the conceptual framework and the evaluation model of gifted curriculum in visual art based on the CIPP model, which is the representative model of decision-making approach. It concludes with its implications and the discussion about the role of evaluators.

• Journal of Korea Society of Industrial Information Systems
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• v.16 no.2
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• pp.19-29
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• 2011

Due to the development of web technologies and the increasing use of smart devices such as smart phone, in recent various web services are widely used in many application fields. In this environment, the topic of supporting personalized and intelligent web services have been actively researched, and an analysis technique on a web-click stream generated from web usage logs is one of the essential techniques related to the topic. In this paper, for efficient analyzing a web-click stream of sequences, a sequential pattern mining technique is proposed, which satisfies the basic requirements for data stream processing and finds a refined mining result. For this purpose, a concept of interesting sequential patterns with a time-interval constraint is defined, which uses not on1y the order of items in a sequential pattern but also their generation times. In addition, A mining method to find the interesting sequential patterns efficiently over a data stream such as a web-click stream is proposed. The proposed method can be effectively used to various computing application fields such as E-commerce, bio-informatics, and USN environments, which generate data as a form of data streams.

• Journal of The Korean Association For Science Education
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• v.2 no.1
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• pp.31-51
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• 1980

In order to research into the devel of the concept of movement and speed in our own way and compare with the Piaget's method, and then find out the formative period of such development, we have put the 192 primary school children as the model and obtained the following results. 1. As their grade upyards, all the experimental subjects showed the gradual progress generally regardless of sex or regions, while only the relative speed showed irregular progress. 2. There was no experimental subject which showed any remarkable sexual characteristics. But in the relative movement, the lower grade boys and higher grade girls made progress. In the subjects of circulation movement, intuition of speed, relative speed and speed of simultaneous movement, the boys marked better progress, whilst the girls were advanced a little in the speed of continuous movement with, different distance and time. 3. There was no conspicuous difference between the urban and rural areas, except a slight tendency that the urban children made better progress in the change of progressing direction, native continuous procedure of periodical movement, travelling road, and the speed of continuous movement with different distance and time whereas the rural children were more advanced in the relative movement, relative speed and intuition of speed. But it should be 'taken into consideration that the rural regions in our case were relatively developed in comparison with the traditional rural communities, which may explain about little regional difference. 4. Comparing our research results with the Piaget's theory, we have reached below results. Our research reports that the formative period of the conception of the problems of diverse progressing direction and a native continuous procedure of periodical movement was simultaneous, at the Piagetian level(at the fourth grade) which coincides with Piagetian theory. The travelling road should be made up a little lower at 2A/2B according' to Piagetian Level, whereas it was formed at the 4th grade as shown in our previous research. Intuition of speed should belong to the prior stage to concrete operation, but our research shows it was formed late at the 4th grade. Composition of displacement was made at the 6th grade, and it was almost equal to the first stage of formal operation(3A). But in the subjects of relative movement relative speed, the speed of continuous movement with different distance and time, relation and preservation of invariable speed, and accelerated motion, even 6th grade children marked a poor record. Summed up, the procedure conception as a basic movement conception coincides with the Piagetion level. But as for speed intuition, relative speed and speed fixation, it was Jar behind Piagetian level. Therefore it is required that we have to concentrate on the systematic training in these parts on the spot.

• Journal of Korea Port Economic Association
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• v.28 no.1
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• pp.25-52
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• 2012

In order to solve the current problems and inefficiencies within the Port Authorities(PA) in Korea, this study introduces the concept of the integration of PA and analyses the intention of integration. This study is based on analysing the surveys participated by the members of PA. The surveys consist of six main factors which could influence the intention of integration of PA; contribution, autonomy, strategic factor, financial factor, marketing factor and environmental factor. The two main implications from this study can be categorised as follows. First, this study identifies the structural problems such as regional self-centredness of PA, obscurity of organisations' roles and their rights, limitations on diversification of business and restrictions within PA. Second, this study extensively discusses the option of improving the inefficiency whilst maintaining the current system or to switch to the integration of PA. In addition, it has been found that individual PA recognise the little need for integration. Since the results show that the strategic, financial, marketing and environmental factors would cause both significant and little significant impacts, it would be too haste to decide on a conclusion. However, it is possible to say that the rapid integration of PA can neither improve the efficiency nor improve the characteristics of each region. Therefore, the significance of integration of PA must be further discussed from many different perspectives. The results of this research will serve as a basic literature for further studies on the integration of PA in Korea. Moreover, the problems that have been identified and analysed in this study will contribute to establishing the strategy for further development of PA in Korea.

• Korean Journal of Optics and Photonics
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• v.28 no.4
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• pp.158-165
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• 2017

The physical shape of an ultrasound transducer has not been considered in previous studies of the photoacoustic saturation effect, where a photoacoustic signal's magnitude linearly increases as an absorption coefficient increases and it is finally saturated. In this paper, the effect of a spherically focused ultrasound transducer on photoacoustic nonlinearity is investigated. The focused ultrasound transducer's spatial filtering effect on photoacoustic signals is analytically derived considering the combined concept of a virtual point detector and Green function approach. The ultrasound transducer's temporal response (i.e., transfer function) effect on photoacoustic signals is considered by integrating photoacoustic signal values within the absorption area covered by a spatial resolution of the ultrasound transducer. Results from the analytically derived expression show that the magnitude of photoacoustic signals measured by a spherical focused ultrasound transducer shows a maximum at a specific absorption coefficient, and decreases after that maximum point as an absorption coefficient is increased. The origin of this photoacoustic nonlinearity is physically understood by comparing the ultrasound transducer's transfer functions and photoacoustic resonance spectra. In addition, this physical interpretation implies that the photoacoustic nonlinearity is strongly dependent on the irradiance distribution inside an absorption medium.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.1
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• pp.63-74
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• 2000

The main objective of this paper is to apply as the basic data for development of a methodology to discuss the future earthquake preparedness measures in Korea by investigating the concept and applicabilities of the Japanese Standard for Evaluation of Seismic Performance of Existing RC Buildings developed in Japan among the methodologies of all the countries of the world. This paper describes the seismic performance, Is-index, of existing RC buildings in Tokyo, Japan evaluated by the Japanese Standard, also the relationships between Is-index distribution of existing RC buildings in Tokyo and that of Shizuoka and Chiba Prefecture reported already in reference[4][5][6] are investigated. And from the comparison with Is-index to buildings damaged by earthquakes experienced in Japan, the damage ratio due to severe earthquake of 3 districts mentioned above is estimated based on the probabilistic point of view. The results of this study can be utilized to identify urgently required earthquake preparedness measures with highest priority in existing RC buildings, and the methodology to evaluate the seismic performance of existing RC buildings in Japan, statistics analysis method and the methodology to estimate earthquake damage ratio based on the probabilistic point of view shown in this study can be recommended to develop a methodology to discuss the future earthquake preparedness measures in Korea.

• Nuclear Engineering and Technology
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• v.27 no.3
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• pp.393-402
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• 1995

The structural analysis of the reactor coolant system mainly consist of too fields. The one is the static analysis considering the impact of pressure and temperature built up during normal operation. The other is the dynamic analysis to estimate the impact of postulated events such as the seismic loads or postulated branch line pipe breaks event. Since the most important goal of the RCS structural analysis is to prove the safety of the RCS during normal operation or postulated events, a widely proven theory having enough conservatism is adopted. The load occurring on the RCS during normal operation is considered as the basic design loading condition throughout whole plant life time. The most typical characteristic of the RCS during normal operation is the thermal expansion of the RCS caused by reactor coolant with high temperature and pressure. Therefore, the exact estimation on the thermal movement of the RCS is needed to get more clear understanding on the thermal movement behavior of the RCS. In this study, the general structural analysis concept and modeling method to evaluate the thermal movement of the RCS under the normal plant operation condition are presented. To discuss the validation of the suggested analysis, analysis results are compared with the measured data which ore referred from the standardized 1000 MWe PWR plant under construction.

• Korean Security Journal
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• no.15
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• pp.221-242
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• 2008

Protection is to maximize the protectee's physical security by minimizing the threats and minimizing the damages caused by the threats. From this point of view, the assassination case of Israel's former Premier Yitzhak Rabin who devoted himself to proceed peace process in Middle East, on November 4, 1995, gives us a lot of lessons on protection. At that time, Israeli society was chaotic with anti-Rabin and anti-government demonstrations which is against Rabin's peace process, and they openly threatened to assassinate Premier Rabin. However, Shin Bet, Israeli Protective Agency, didn't reacted against the assassination threats effectively. Also they have to try to secure friendly public to widen the width of selection in case of crisis and to secure the credibility of the organization. They have to prevent harmful activities in advance by securing wide intelligence networks to collect and analyze various protective intelligences and preparing proper protective countermeasures. Intelligence is a basic element in protection and any protective measures not supported by intelligence activities are not useful and effective. Potential attackers study their target thoroughly and make an elaborate plan before their attack. Advance team is required to conduct security measures on a basis of analysis of vulnerability and threat factors, and close protection team should be prepared for the changing situations with crisis-consciousness. Is security, 100% perfection is not possible. However, Shin Bet failed to analyze and approach to the existing threats. They forgot the fact that security environment reflects social situations. Protection agents should be conscious of the fact that today is different from yesterday. So we have to expect what is not expected when not expected.