• Journal of Elementary Mathematics Education in Korea
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• v.14 no.1
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• pp.135-151
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• 2010

The purpose of this study is to investigate the effect of learner-centered instructions using instructional materials which are developed in the light of constructivism and implementing practices of the instruction. According to the result of Recall Test, experimental group and comparing group have not statistically meaningful difference. However, in the result of Generation Tests which include the contents not dealt with during the experiment treatments, the two groups have statistically meaningful difference. It can be drawn from the result that students who take learner-centered instruction are in a good readiness for learning of the contents which will be addressed in future.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.4
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• pp.344-350
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• 2009

The goal of this study is to introduce the theoretical background of acoustic nonlinearity in surface wave and to verify its characteristics by experiments. It has been known by theory that the nonlinear parameter of surface wave is proportional to the ratio of $2^{nd}$ harmonic amplitude and the power of primary component in the propagated surface wave, as like as in bulk waves. In this paper, in order to verify this characteristics we constructed a measurement system using contact angle beam transducers and measured the nonlinear parameter of surface wave in an Aluminum 6061 alloy block specimen while changing the distance of wave propagation and the input amplitude. We also considered the effect of frequency-dependent attenuation to the measurement of nonlinear parameter. Results showed good agreement with the theoretical expectation that the nonlinear parameter should be independent on the input amplitude and linearly dependent on the input amplitude and the $2^{nd}$ harmonic amplitude is linearly dependant on the propagation distance.

• Journal of The Korean Association For Science Education
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• v.22 no.4
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• pp.820-836
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• 2002

Constructivism has had a great influence on science education over the last two decades. The purpose of this article is twofold: First, to describe the characteristics of constructivism and, second, to suggest an ideal forms of science education in Korea as implied in constructivism. A review of the literatures in the first area shows that constructivism is philosophical/psychological view which believe in the social nature of the construction of scientific knowledge and its learning. And the analyses of a few schools of constructivism suggest decision-making as a goal of science education, learning as the active construction of meaning through interaction between learner and learning environments, and discussion and cooperation as appropriate teaching strategies. At the same time, the results necessitate teaching ethical aspects of science in the secondary schools, and also imply that performance assessment must be emphasized in evaluation of science education.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.5
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• pp.542-548
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• 2001

A robust, accurate, broad-band, alternating current sensor using fiber-optics is being developed as a part of optical over current protection relay system. The sensor uses the Faraday effect in optical fiber and polarimetric measurements tc sense electrical current. The current sensing coil consists of a length of twisted optical fiber and Faraday rotator mirror to suppress the linear birefringence effect. Due to its single-ended closed path structure, it can not only be easily installed to the target with great isolation from other fields in the vicinity, but the sensitivity can be increased by using multiple turns. This paper reports on the theoretical backgrounds of the sensor design and the preliminary experimental results.

• Journal of the Korean Society for Nondestructive Testing
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• v.13 no.4
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• pp.9-17
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• 1994

It is well recognized recently that ultrasonic technique is one of the most widely used methods of nondestructive evaluation to characterize material properties of nonconventional engineering materials. Therefore it is very important to understand physical phenomenon on propagation behavior of elastic wave in these materials, which is directly associated with ultrasonic signals in the test. In this study, the theoretical analysis on multi-scattering of harmonic elastic wave due to the particulate with interface between matrix and fiber in metal matrix composites(MMCs) was done on the basis of Lax's quasi-crystalline approximation and extinction theorem. SiC particulate (SiCp) reinforced A16061-T6 composite material was chosen for this analysis. From this analysis, frequency dependences of phase velocity and amplitude attenuation of effective plane wave due to the change of volume fraction of SiC particulate were clearly found. It was also shown that the interface condition between matrix and fiber in MMCs gives a direct effect on the variation of phase velocity of plane wave in MMCs.

• Journal of the Korean Society for Nondestructive Testing
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• v.19 no.3
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• pp.200-206
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• 1999

This paper describes the stress analysis of a curved beam by using photoelasticity. In order to measure accurate isochromatic fringe orders at certain locations. fringes are doubled and sharpened by digital image processing. After fringe multiplication and sharpening. fringe orders can be read as a quarter order interval (N=0, 1/4, 2/4, 3/4,...). The results obtained from photoelastic experiment are compared with those calculated by using theory. Two results are agreed well even though there are some scatter bands with maximum 8 percent for the results of photoelastic measurements and theoretical calculation. Difference may be occurred due to the slight misalignment of the direction to which axial load is applied in photoelastic experiment. It is confirmed that accurate measurement of stress distribution can be possible by using the techniques of fringe multiplication and sharpening in photoelasticity.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.1
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• pp.38-44
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• 2004

An experimental study for a crane hook was performed to investigate the stress distribution along a certain line where the maximum and minimum stresses to be developed. On this line, the isoclinic fringe and/or principal stress direction is constant. The crane hook was modeled into a 2-dimensional plate made of urethane rubber called 'Photoflex' The Photoflex is very sensitive to a load and has low photoelastic fringe constant. The Tardy compensation method with the fringe sharpening process and the 4-step phase shifting method, was used for the photoelastic technique. Experimental results by photoelasticity were compared with the calculated stresses from the simple curved beam theory and tile finite element analysis. Ail the results were close to each other.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.6
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• pp.331-339
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• 2002

This paper presents a garbage collection protocol for checkpoints and message logs which are staved on the stable storage or volatile storage for fault tolerancy. The previous works of garbage collections in coordinated checkpointing protocol delete all the checkpoints except for the last checkpoints on earth processes. But implemented in top of reliable communication protocol like as TCP/IP, rollback recovery protocol based on only last checkpoints makes sympathetic rollback. We show that the old checkpoints or message logs except for the last checkpoints have to be preserved in order to replay the lost message. And we define the conditions for garbage collection of checkpoints and message logs for lost messages and present the garbage collection algorithm for checkpoints and message logs in coordinated checkpointing protocol. Since the proposed algorithm uses process information for lost message piggybacked with messages, the additional messages for garbage collection is not required The proposed garbage collection algorithm makes 'the lazy garbage collectioneffect', because relying on the piggybacked checked checkpoint information in send/receive message. But 'the lazy garbage collection effect'does not break the consistency of the whole systems.

• Journal of the Korean Chemical Society
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• v.46 no.1
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• pp.83-89
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• 2002

In this study, students' responses to anomalous data in studying ‘density' were analyzed, and the relationships among trait/state self-regulation strategies, the degree of cognitive conflict, and conceptual change were examined. A trait self-regulation strategy test, a preconception test, and a test of response to anomalous data were administered to 352 eighth graders. Among them, 146 students whose preconceptions were consistent with the presented initial theory were selected. After they had read a scientific explanation, a state self-regulation test and a researcher-made conception test were administerd. There were no significant correlations among the subcategory scores of trait/state self-regulation strategies and the degree of cognitive conflict. The scores of the conception test were significantly correlated with those of trait planning, trait effort, state planning, state self-monitoring, and state effort. State effort was only a significant predictor on students' conceptual change.

• Journal of Gifted/Talented Education
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• v.24 no.5
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• pp.733-755
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• 2014

This study aims to develop and validate Creative Problem Solving Profile Inventory (CPSPI) which is a scale to measure the creative thinking style, based on the CPS theory. For redeeming the limits of existing scales, this study developed an inventory which includes an evaluation for cognitive ability as well as cognitive preference and the stage to share an idea with others and persuade (Persuasion & communication stage). At the early stage, 7 factors (stages) and 82 items were developed and finally, 5 factors and 39 items were selected through item analysis and validation of construct validity. In conclusion, CPSPI will be used as an educational tool for self-development by knowing own's strengths and weaknesses in the creative problem-solving process, and help in displaying cooperative creativity by understanding other people and interaction, based on creative thinking profiles of group members.