• Journal of Science Education
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• v.38 no.1
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• pp.182-195
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• 2014

Ray drawing in geometrical optics is an effective method for visible imagery of light. In this study, we developed peer instruction materials for in-service teachers' training concepts on the refraction of light including drawing rays. And then we applied these programs to 29 pre-service teachers and 21 in-service primary teachers and evaluated the degree of conceptual change in correct points from the pretest and the post one. As a result of pretesting, in spite of experiences for learning this topic in elementary and secondary education courses, most participants in the study did not well understand the path of refracted light before instructions. However, the result of post testing after the application of peer instruction materials shows that they have practiced ray drawing, which is helping visible imagery. Accordingly, in learning geometrical optics, we suggest that peer instruction with ray drawing activity for teachers' training program would be effective. We also suggest that similar approaches would be applied to other context.

• The Journal of the Acoustical Society of Korea
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• v.21 no.8
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• pp.686-694
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• 2002

This paper proposes an algorithm for estimating positions of array elements placed on a sea floor using acoustic signal in multipath ocean environment. The positions of array elements are estimated by using the travel times of m-sequence signal influenced by the multi-paths environment. The horizontal distance between source and receiver calculated based on the ray model. The proposed paper the algorithm is verified by both simulation data and field experiment in the Bast Sea.

• Proceedings of the KSRS Conference
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• v.1
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• pp.312-315
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• 2006

Radio occultation technique has been used in planetary science to obtain reliable and accurate temperature profiles of the other planets' atmosphere for decades. It relies on the fact that radio waves are bent and delayed due to the gradient of atmospheric refractivity along-ray-path. With the advent of Global Positioning System (GPS), it becomes possible to retrieve the refractivity and temperature profiles of the Earth's atmosphere from the occultation data. We have developed a retrieval algorithm and compared the results of our algorithm with the data of CHAMP to verify the accuracy of our algorithm is good enough. In our algorithm, there are some smoothing steps when retrieving. We analysis the data of FORMOSAT-3 and compare the results with and without smoothing and the results of TACC to see is there any phenomenon deleted after smoothing.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.258-263
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• 1999

In this study, the numerical and experimental investigations were conducted to understand ultrasonic wave propagation and to evaluate the degree of fiber waviness in thick composites nondestructively. The path, energy and traveling time of insonified wave were predicted by adopting the ray and plane wave theories. In the analysis, the composites were assumed to have continuous fiber with sinusoidal waviness in a matrix and were modeled as stacks of infinitesimally short length off-axis elements with varying fiber orientation along the length direction. From the experiments on the specially fabricated thick composite specimens with various degrees of uniform fiber waviness, the energy distributions of received wave were obtain for the various positions of transmitter. It was observed that the energy of wave was converged to the adjacent peaks of fiber waviness. The location where maximum energy of wave was detected from the experiments showed good agreement with the location obtained from theoretical predictions. Finally, the test procedure was Proposed to evaluate fiber waviness in thick composites by considering the energy of wave and relative distance between transmitter and receiver.

• Journal of the Korean Society for Heat Treatment
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• v.4 no.3
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• pp.21-30
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• 1991

Microstructural analysis was conducted to observe the effect of aging treatments in a Cr-Mn austenitic stainless steel containing nitrogen, and the amount, size, shape and distribution of precipitates were investigated. It was found that on water quenching from $1000^{\circ}C$ after holding 3 h at that temperature, the steel contained no precipitates observable by optical microscopy. Precipitation of phases begins at places most favorable for the formation of nuclei-in the boundaries of grains and twins. Precipitates were studied in detail by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Chemical compositions of precipitates were examined by the use of scanning transmission electron microscopy (STEM) together with an energy dispersive X-ray (EDX) microanalysis. Also chromium depletion adjacent to grain boundary precipitates was investigated by the use of Auger electron spectroscopy (AES) for a direct examination of the fracture surface chemistry.

• The Journal of the Acoustical Society of Korea
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• v.1 no.1
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• pp.19-26
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• 1982

n optimization technique is adapted to determine the stage enclosure configuration preferred by performers. The merit function which quantifies the ease of ensemble among the performers is derived from a set of qualitative conditions recommended by researchers of hall acoustics. The ray path tracing technique based on the modified method of images is used to analyze acoustical characteristics at any locations of performers in stage enclosure. The gradient search technique is employed to find the geometric parameters which maximmize the merit function. As an example, optimum stage enclosure configuration of the trio chamber music is obtained using the computer program developed. The developed technique can be used in the design of concert hall stage and also in forming a special enclosure with movable reflecting surfaces.

• Korean Journal of Optics and Photonics
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• v.10 no.3
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• pp.237-242
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• 1999

Taking into consideration the thermal lensing effects of laser rods, depolarization losses of laser beams induced by the thermal birefringence were calculated. The numerical model proposed for the calculation, which is based on the paraxial ray optics formulation and provides explicit expressions of optical path lengths for various optical elements, was described in detail. Calculated results were compared with those of Jones matrix formulation and experiments. The calculated results are in good agreement with experimental results.

• Research in Community and Public Health Nursing
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• v.29 no.2
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• pp.194-205
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• 2018

Purpose: The aim of this study is to investigate and elucidate actual experiences of alcoholics' spouses using familial social gatherings. Methods: A total of nine women whose alcoholic husbands were attending Al-Anon meetings held in Y Cathedral in S District of Seoul were included in this study. Data collection of this study was conducted through in-depth interviews with participants from September 24 to November 30, 2015. Data analysis was conducted at the same time as the data collection, and analysis was performed according to the method suggested by Colaizzi(1978). Results: We categorized the participants' experiences into five themes including 'Trapped in a Deep Dark Tunnel', 'Life of Walking in an Endless Tunnel', 'Reaching a Dead End', 'Walking towards a Ray of Light', 'Finding Oneself on a Strange Path'. Conclusion: The results of this study provide an understanding of the essential structure of the life experiences of alcoholic spouses using familial social gatherings.

• The Journal of Engineering Geology
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• v.6 no.3
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• pp.131-136
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• 1996

Attenuation characteristics of AF/MA motions which involve high frequencies were investigated through pencil-lead fracture tests on a fine-grained granite specimen. For the study, calibrated six transducers were employed to detect the signals and the pencil-lead was fractured as a step unloading force to generate AE/MA signals. The arnplitude AE/MA waves is affected by the relative orientation of source and transducer as well as the source distance. The attenuation constant for Charcoal granite is obtained as 1.058 which could be applied for a given ray-path regardless of the relative orientation of source and transducer.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.153-156
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• 2006

본 논문에서는 무선공중망을 이용하여 재택 혹은 원거리에서도 환자의 상태를 확인하고 감시함으로써 의료서비스의 이동성을 제공하기 위한 의료정보 무선전송 시스템을 제안하고, 시뮬레이션 하였다. 제안한 방법은 응급상황 발생 시 의료정보를 디지털 데이터로 변환하여 PDA와 같은 이동형 단말에 전송함으로써 신속한 응급처치 등이 가능토록 한다. 시뮬레이션은 이동 무선채널환경에서 신뢰성 있는 의료정보의 전송을 위하여 IEEE 802.11a에 근거한 OFDM/QPSK 전송방식을 사용하였고, AWGN과 3-ray 이동 다중경로 페이딩 환경에서 신뢰성 있는 정보전송을 위하여 콘볼루션 코딩을 적용하여 시스템 성능을 분석하였다.