• Journal of the Korean Institute of Telematics and Electronics
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• v.11 no.1
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• pp.1-7
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• 1974

This paper discribes the reflector type ultrasonic concentrator which makes hghintencity of ultrasonic field. This was made by rotating parabolic surface which only using total reflection aria, that makes boundary by the critical angle of reflection of sound. I made two binds of concentrator acording to the type of ultrasonic transduser: one is internal surface reflector type concentrator, which is available for disc type transducer, and the other is external surface reflector type concentrator which is available cylinderical transduser. In the mony aspects the reflector tripe concentrator is supel'ier to the reflection type concentrator as plastics lens; It is more durable in high temperature and high intencity ultrasonicfield then refrector type concentrator because of it is made by glass or metal, and it has higher. efficiency because of it wasts made by only total reflection aria that is without absoption lose. I think this is useful ultrasonic concentrator in mony industrial field, in which high intencitr of ultrasonic energy was used.

• Journal of Ocean Engineering and Technology
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• v.16 no.3
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• pp.1-7
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• 2002

In this paper, a numerical model to analyze the performance of a vertical slit-type wave absorber is developed under the assumption of inviscid water waves. The formulation combines the linear potential theory with a semi-empirical description of the eddy-shedding at a slit-type wave absorber. We investigated the reflection coefficients over a wide frequency range for a vertical slit-type wave absorber both with and without a solid rear wall. Model test was conducted at KRISO' s two dimensional wave tank to validate the theoretical results. It is found that the agreement between theoretical results and experimental data is surprisingly good. We found that the wave absorbing system using a vertical slit plate has sufficient potentials for breakwaters for ocean development.

• Journal of the Korean Society for Marine Environment & Energy
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• v.6 no.4
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• pp.45-51
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• 2003

The reflection and transmission of submerged breakwater with trapezoidal type are computed numerically using boundary element method. The analysis method is based on the wave pressure function with the contlnuit? in the analytical region including fluid and porous structures. Wane motion within the porous structures is simulated by introducing the linear dissipation coefficient and added mass coefficient. The results indicate that transmission and reflection coefficient are determined due to the change of slope of submerged breakwater with trapezoidal type.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.1 s.139
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• pp.18-23
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• 2005

The transmission and reflection coefficiencies of a BBDB-type floating breakwater in water of finite depth are studied taking account of fluctuating air pressure in the air chamber. The wave potential is calculated by a hybrid integral equation consisting of a Green integral equations associated with the Rankiue Green function inside the BBDB and the Kelvin Green function outside. The transmission and reflection coefficients of the breakwater are obtained directly from the potential solution in the outer region.

• Korean Medical Education Review
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• v.19 no.3
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• pp.169-174
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• 2017

This study explores the phenomenon of learner reflection in writing. Sixty-nine reflection logs were submitted by students after medical interview role plays. Using thematic analysis methodology, the following three steps were carried out: (1) the entire contents of the logs were analyzed and coded, (2) the coded contents were reclassified and categorized into higher themes, and (3) all reflection logs were re-analyzed to derive the frequency according to their classifications. The learners' reflection contents were classified into 'preparation,' 'experience,' and 'future plan.' The levels of reflection were 'simple information and appreciation,' 'acquisition and application of knowledge,' and 'analysis and criticism.' The types of reflection were identified only at the level of 'analysis and criticism' and could be classified into 'relativization,' 'objectification,' and 'internalization.' Students' reflection levels were highest in the levels of 'acquisition and application of knowledge' (49.3%), and 'analysis and criticism' (37.7%). A total of 14.5% of the students showed 'internalization.' In order to enable internalized reflection at a critical level, instructional strategies to induce and promote reflection are needed.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2003.12a
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• pp.117-121
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• 2003

In this paper, a micromachined low-loss and ultra wide band reflection-type phase shifter (RTPS) is proposed. The phase shifter shows a constant phase shift from 5 to 17 GHz and consists of two cascaded reflection-type phase shifter. Low-loss reflection termination consists of digital capacitive switches, and air-gap overlay CPW couplers are used in order to employ the low-loss 3 dB coupling. The fabricated phase shifter showed the 5 discrete states, $0^{\circ},{\;}22.5^{\circ},{\;}45^{\circ},{\;}67.5^{\circ},{\;}90^{\circ}$ respectively, the average insertion loss of 3.48 dB, and maximum rms phase error of ${\pm}1.80^{\circ}$ for the relative phase shift from $0^{\circ}{\;}to{\;}90^{\circ}$ over 5-17 GHz.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.2
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• pp.120-125
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• 2015

With rapid urbanization, the volume of traffic in urban area has been significantly increased. This in turn led to problem which can be described as Road Traffic Noise. Currently, to alleviate the road traffic noise damage, a demand for installation of soundproofing walls is rising. Among different shapes of soundproof walls being installed, the reflection-type acoustical insulation panel is highly drawing attentions of residents due to the fact that it does not obstruct their field of vision in contrast with the opaque acoustical insulation panel. On the other hand, improving the soundproofing wall of the reflection-type acoustical insulation barrier panel needs to be focused on since it has a possibility to cause a secondary damage by reflected sounds. Therefore, in this research, study has been carried out to improve the forms in order to minimize travelling of reflected sounds through changing the frontal surface shape and geometrical shape of the reflection-type soundproofing panel. A result from comparison between the normal reflection-type soundproofing panel and the improved soundproofing panel, with reduction effects in the noise reflection, showed that the curved type of soundproofing panel has an impact on reducing the noise up to 1.5 dB. Furthermore, from the research conducted, it appears that the increase and decrease in the reflected sounds can be changeable depending on various design factors. Thus, it turns out that the study shows a potential possibility to develop a reduction technology of the reflected sounds pertaining to overall condition on the soundproofing walls.

• Journal of Astronomy and Space Sciences
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• v.33 no.3
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• pp.197-205
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• 2016

We investigated two flares in the solar atmosphere that occurred on June 3, 2012 and July 6, 2012 and caused propagation of Moreton and EIT waves. In the June 3 event, we noticed a filament winking which presumably was caused by the wave propagation from the flare. An interesting feature of this event is that there was a reflection of this wave by a coronal hole located alongside the wave propagation, but not all of this wave was transmitted by the coronal hole. Using the running difference method, we calculated the speed of Moreton and EIT waves and we found values of 926 km/s before the reflection and 276 km/s after the reflection (Moreton wave) and 1,127 km/s before the reflection and 46 km/s after the reflection (EIT wave). In the July 6 event, this phenomenon was accompanied by type II and type III solar radio bursts, and we also performed a running difference analysis to find the speed of the Moreton wave, obtaining a value of 988 km/s. The speed derived from the analysis of the solar radio burst was 1,200 km/s, and we assume that this difference was caused by the different nature of the motions in these phenomena, where the solar radio burst was caused by the propagating particles, not waves.

• Geophysics and Geophysical Exploration
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• v.7 no.1
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• pp.1-6
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• 2004

High-resolution S-wave reflection surveying has been successfully conducted on paved areas using a Land Streamer originally designed by the author. The main feature of the Land Streamer tool is the non-stretch woven belt on which geophone units are mounted to form a multichannel geophone array similar to a marine streamer. Because it is easily towed by a vehicle or by hand, the tool leads to high performance in field measurements and resultant cost-effectiveness of high-resolution reflection surveys. Although each geophone unit is coupled to the pavement through a metallic baseplate instead of being firmly planted in the ground, the Land Streamer tool provides comparatively clean data, unaffected by traffic noise even on the pavement. Thus, the tool is capable of expanding the opportunity for S-wave reflection surveys in urban areas where many surfaces are paved and traffic noise is severe. A series of high-resolution S-wave reflection surveys on paved areas delineated detailed structures of surface layers shallower than 60 m, and proved the wide applicability of the tool to engineering, environmental applications, and earthquake disaster prevention projects.

• Korean Journal of Optics and Photonics
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• v.4 no.3
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• pp.276-280
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• 1993

Holographic reflection filters are fabricated by using the dichromated gelatin film. The characteristics of diffraction efficiency, center wavelength, and bandwidth which are important parameters of reflection-type holographic optical elements is explained from the experimental results, and control method of these parameters is presented.