• Journal of Advanced Research in Ocean Engineering
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• v.1 no.1
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• pp.44-54
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• 2015

Breakwaters are the coastal structures constructed either perpendicular (shore connected) or parallel (detached) to the coast. The main function of breakwater is to create a tranquil medium on its leeside by reflecting the waves and also dissipating the wave energy arriving from seaside, resulting in ease of manoeuvrability to boats or ships to their berthing places. Different types of breakwaters are being used at present, such as rubble mound breakwater, vertical wall type breakwater and composite breakwater. The objective of this paper is to investigate reflection coefficients (Kr) and dissipation (loss) coefficients (Kl) for physical models of Quarter circle caisson breakwater of three different radii of 0.550 m, 0.575 m and 0.600 m with S/D ratio of 2.5 (S=spacing between perforations, D=diameter of perforations). The models were tested in the monochromatic wave flume of the department, for different incident wave heights (Hi), Wave periods (T) and water depths (d). It was observed that reflection coefficient increased with increase in the wave steepness (Hi/gT2) and decreased with increase in depth parameter (d/gT2) and hs/d (Height of structure including rubble base/depth of water). The loss coefficient decreased with increase in the wave steepness and increased with increase in depth parameter and hs/d.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.6
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• pp.1283-1288
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• 2015

In general, IC chip circuit which is operating a cryptographic computation tends to radiate stronger electromagnetic signal to the outside. By using a power detecter such as a loop antenna near cryptographic device, the encryption key can be identified by probing a electromagnetic signal. To implement a method against non-invasive type attack, multi dielectric slab structure on IC chip to suppress radiated electromagnetic signal was introduced. Multiple dielectric slab was implemented by suitably configured to have the Bragg reflection characteristics, and then the reflection response was computed and verified its effectiveness. As a result, the thickness of the dielectric coating was 2mm and the reflection response characteristics for the vertical incidence was achieved to be 91% level.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.4
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• pp.500-505
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• 2011

In this paper, two types of micro-optic submersion detection systems are proposed and demonstrated. The structures are based on the transmission and reflection of incident light, respectively. Two collimators are separated by 10 mm and installed face to face in straight line. The incident light transmits from one side of collimator to the other through the air, but the optical loss is below 1 dB. On the other hand, when the sensors are submersed into water, most of optical power scattered into water. The systems monitor the dramatical power change to alarm the submersion. Reflection type of sensor system has a Bragg grating at the end of the sensor for back-reflection of sensing signal. This is for simple configuration of systems. The performance of two sensor systems are described in detail.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.357-360
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• 1997

Abstract: In teleoperation field robotic system such as hydraulically actuated robotic excavator, the maneuverability and convenience is the most important part in the operation of robotic excavator. Particularly the force information is important in dealing with digging and leveling operation in the teleoperated excavator. Excavators are also subject to a wide variation of soil-tool interaction forces. This paper presents a new force reflecting joystick in a velocity-force type bilateral teleoperation system. The master system is electrical joystick and the slave system IS hydraulically actuated cylinder with linear position sensor. Particularly Pneumatic motor is used newly in the master joystick for force reflection and the information of the pressure of salve cylinder is measured and utilized as the force feedback signal. Also force-reflection gain greatly affects the excavation performance of a hydraulically actuated robotic system and it is very difficult to determine it appropriately since slave excavator contacts with various environments such as from soft soil to rock. To overcome this, this paper proposes a force-reflection gain selecting algorithm based on artificial neural network and fuzzy logic.

• Proceedings of the Optical Society of Korea Conference
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• 2004.07a
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• pp.190-191
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• 2004

• Proceedings of the Optical Society of Korea Conference
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• 2004.02a
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• pp.282-283
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• 2004

• Journal of The Korean Association For Science Education
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• v.37 no.4
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• pp.553-564
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• 2017

This study investigated the change of pre-service elementary teachers' professional visions through video-based reflection on science teaching with focus on their attention and pedagogical reasoning about student learning. Specifically, we compared two reflection cycles before and after pre-service elementary teachers went through the collaborative video-based reflection process in a professional learning community. The primary data were collected from eight pre-service elementary teachers and included their science lesson plans, videotaped lessons, video-reflection papers, and transcripts from the interviews. Pre-service elementary teachers' attention was categorized in five aspects: classroom management & control, teacher's instruction, students' thinking & learning, subject knowledge, and assessment. The level of their pedagogical reasoning about student thinking and learning was determined with six levels based on the number of evidence, evidence area, and evidence type. The findings revealed that 1) individual reflection is not enough - collaborative reflection is essential to change their attention toward students learning and thinking 2) pedagogical reasoning levels increase gradually throughout the individual and collaborative video-based reflection processes. The participants not only attributed student learning solely to the characteristics of students but also connected it with their own instruction or science content knowledge and used different types of evidences as they went through two reflection cycles. Implications for using video in the teacher education program were discussed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.770-776
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• 2009

We propose and demonstrate an I/Q demodulator using four-port BPSK demodulator base on additive mixing and reflection-type phase shifter using hybrid technique. Previously, the conventional I/Q demodulator base on multiplicative or additive mixing method divides I/Q signal path from mixer to parallel-to-serial converter. In this paper, we propose new I/Q demodulator without dividing I/Q baseband signal path. The proposed schematic requires half size in implementation and half power consumption in baseband path compared with the conventional receiver. Also, the proposed receiver eliminates parallel-to-serial converter after data decoding. The proposed circuit has been successfully demodulated a QPSK signal with the L-band carrier frequency and 20 Mbps data rate.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.5
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• pp.398-408
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• 2007

For better evaluation of material thickness by using the reflection type pulsed eddy current method, various probe models are designed and their response signals, characteristics, and sensitivities to thickness variation are investigated by a numerical analysis method. Since the sensor needs to detect magnetic fields from eddy currents induced in a test material, not from the exciter coil, two types of models that are shielded by the combination of copper and ferrite and only by ferrite are considered. By studying response signals from these shielded probe models, the peak value and the zero crossing time are selected as useful signal features for the evaluation of material thickness. Investigation of sensitivities of these two features shows that the sensitivity of peak value is more useful than that of zero crossing time and that the probe shielded only by ferrite gives much better sensitivity to thickness variation.

• Korean Journal of Social Welfare
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• v.51
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• pp.183-210
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• 2002

The purpose of this study is to investigate correction-level associated with the social support perceived by juvenile delinquents. To accomplish these purposes, this study used sample of 546 juvenile delinquents who are in the process of the beginning stage in the police and prosecution. Social support and correction were assessed with an instrument designed for this study. Juvenile delinquents completed instruments assessing the following variables: (1) perceived social support scale, specially social support types(esteem support, emotional support, informational support) and social support providers (parents, relatives, friends, teachers, community) (2) correction scale, specially social stigma, social deprivation, self reflection, legal consciousness, self concept. The resulting scale of the instrument had good internal reliability(Cronbach's alpha=. ) and was scored so that high scores indicated a willingness to access. To examine this purpose, One way ANOVA, multiple regression analysis were conducted. And the results are as follows: The relationship ratings of the correction factors were positively associated with their rating of the type of social support. Informational support was positively associated with self reflection and esteem support was positively associated with self concept, legal consciousness, self reflection and emotional support were positively associated with esteem. The type of support according to support providers was significant, explaining 25% of the variance in self concept scores. The significant predictor was esteem support from friends and emotional support from a community. The type of support according to support providers was significant, explaining 20% of the variance in legal consciousness scores. The significant predictor was informational support from teachers and esteem support from a community. The type of support according to support providers was significant, explaining 21% of the variance in self reflection scores. The significant predictor was esteem support and emotional one from relatives.