• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.1353-1359
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• 2004

There are many massive components added on the railway overhead-line. These components cause larger fluctuations of contact forces, which are due to wave reflections and Doppler effects when a high-speed train passes those. In this paper, mathematical formula are derived for the relation between the added mass and contact force fluctuations. Using the derived formula, we calculate a added mass on the overhead-line which cause amplification factor to become 2.5. German design practice requires that amplification factor due to the wave reflection should be less than 2.5 to obtain good current collection performance. To show the validity of the formula, simulation results are compared with the calculation results. Simulation results showed that contact force fluctuations grow rapidly when an added mass is larger than the calculation result. Therefore, the simple form of formula can be used for estimating maximum added mass not to cause large fluctuations of contact forces in early design phase.

• 한국군사과학기술학회지
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• 제21권2호
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• pp.147-157
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• 2018

There are increasing demands to provide early warning against intruding drones and cope with potential threats. Commercial anti-drone systems are mostly based on simple target detection by radar reflections. In real scenario, however, it becomes essential to obtain drone radar signatures so that hostile targets are recognized in advance. We present experimental test results that micro-Doppler radar signature delivers partial information on multi-rotor platforms and exhibits limited performance in drone recognition and classification. Afterward, we attempt to generate high resolution profile of flying drone targets. To this purpose, wide bands radar signals are employed to carry out inverse synthetic aperture radar(ISAR) imaging against moving drones. Following theoretical analysis, experimental field tests are carried out to acquire real target signals. Our preliminary tests demonstrate that high resolution ISAR imaging provides effective measures to detect and classify multiple drone targets in air.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.86-95
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• 2006

Brillouin backscatter is a type of reflection that occurs when light is shone into an optical fibre. Brillouin reflections are very sensitive to changes in the fibre arising from external effects, such as temperature, strain and pressure. We report here several case studies on the measurement of strain using Brillouin reflections. A mechanical bending test of an I beam, deployed with both fiber optic sensors and conventional strain gauge rosettes, was performed with the aim of evaluating: (1) the capability and technical limit of the DTSS technology for strain profile sensing; (2) the reliability of strain measurement using fiber optic sensor. The average values of strains obtained from both DTSS and strain gauges (corresponding to the deflection of I beam) showed a linear relationship and an excellent one-to-one match. A practical application of DTSS technology as an early warning system for land sliding or subsidence was examined through a field test at a hillside. Extremely strong, lightweight, rugged, survivable tight-buffered cables, designed for optimal strain transfer to the fibre, were used and clamped on the subsurface at a depth of about 50cm. It was proved that DTSS measurements could detect the exact position and the progress of strain changes induced by land sliding and subsidence. We also carried out the first ever distributed dynamic strain measurement (10Hz) on the Korean Train eXpress(KTX) railway track in Daejeon, Korea. The aim was to analyse the integrity of a section of track that had recently been repaired. The Sensornet DTSS was used to monitor this 85m section of track while a KTX train passed over. In the repaired section the strain increases to levels of 90 microstrain, whereas in the section of regular track the strain is in the region of 30-50 microstrain. The results were excellent since they demonstrate that the DTSS is able to measure small, dynamic changes in strain in rails during normal operating conditions. The current 10km range of the DTSS creates a potential to monitor the integrity of large lengths of track, and especially higher risk sections such as bridges, repaired track and areas at risk of subsidence.

• 한국과학교육학회지
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• 제41권6호
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• pp.519-531
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• 2021

본 연구에서는 중등 예비과학교사들이 수업 시연 강좌에 참여하면서 어떠한 정체성을 드러내는지 탐색하고자 하였다. 연구 대상은 서울 소재 사범대학의 '탐구학습과 생명과학실험 지도' 강좌를 수강하는 예비과학교사 22명이다. 연구를 위하여 예비교사들의 탐구 수업 설계 및 시연 과정에서 만들어진 모든 자료를 수집하였고, 수업 시연 및 반성 장면을 녹화 및 전사하였다. 또한, 수업 후에 9명의 예비교사를 대상으로 반구조화된 면담을 실시하고 녹음 및 전사하였다. 연구 결과, 강좌 초반에는 과학 교사 정체성이 잘 드러나지 않았다. 예비교사들의 초기 구두 반성에서는 권위적 담화가 나타났으며, 이는 예비교사들이 구두 반성 활동을 '시연된 수업에 대한 평가 활동'으로 인식하고 있음을 보여준다. 이러한 인식은 예비교사들이 대학교에 재학하는 학생으로서 과제를 수행하고 교수자에게 평가를 받는 입장으로 수업 시연 강좌에 참여함을 보여준다. 강좌 중반부 이후, 예비교사들의 과학 교사 정체성을 보여주는 담화가 관찰되었다. 중반부 이후 구두 반성에서는 종종 대화적 담화가 이루어졌으며, 이는 예비교사들이 구두 반성 활동을 '전문성 신장을 위한 배움 활동'으로 인식함을 보여준다. 또한 후반부에는 자신의 경험을 교사의 활동과 연결 짓고 해석하는 담화가 나타났다. 이는 예비교사들이 이 순간 자기 자신을 교사로서 인식함을 보여준다. 또한 강좌를 통해 실험 수업에 대한 인식이 확장되었다. 강좌 내에서 참여자들의 권위를 평등화하고, 반성의 역할 모델을 제공하였으며, 수업을 둘러싼 다양한 입장을 경험해보는 연습이 이루어졌던 것이 예비교사의 과학 교사 정체성 형성에 긍정적인 영향을 미쳤다. 본 연구는 예비교사의 과학 교사 정체성 형성을 위한 교사 양성 과정에 관한 시사점을 제공한다.

• Child Health Nursing Research
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• 제12권4호
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• pp.486-494
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• 2006

Purpose: This study was done to analyze children's play during hospitalization. Method: Data were collected from 36 play situations of hospitalized children, ages 2 to 6, hospitalized at 4 general hospitals, one in each city, Seoul, Suwon, Daejeon and Daegu. All observations were made in pediatric units during free-play periods. Each child was observed for 5 minutes at each observation and observed three times at each play session. Results: Of the children, 83.3% played on the bed. Play partners were mainly mothers. While 75.0% of children actively took part in play activity and 70.0% played with joy, 63.9% of play partners were more passive in the play. The most frequent play material was a small toy. The level of play was early stage of social and cognitive play, and dramatic play was observed in a few children over the age of 3 years. The play activities were conversional play, reflections of therapeutic procedures, imagination, and exploratory play. In the conversional play, children converted hospital equipments into play materials. Conclusion: It is recommended that health care team members should pay attention and actively participate in play of hospitalized children in order to help them have some control over the stress of the situation.

• KCI Concrete Journal
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• 제13권2호
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• pp.10-18
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• 2001

The spectral analysis of surface waves (SASW) method, which is an in-situ seismic technique, has mainly been developed and used for many years to determine the stiffness profile of layered media (such as asphalt concrete and layered soils) in an infinite half-space. This paper presents a modified experimental technique for nondestructive evaluation of in-place cement mortar compressive strength in single-layer concrete slabs of rather a finite thickness through a correlation to surface wave velocity. This correlation can be used in the quality control of early age cement mortar structures and in evaluating the integrity of structural members where the infinite half space condition is not met. In the proposed SASW field test, the surface of the structural members is subjected to an impact, using a 12 mm steel ball, to generate surface wave energy at various frequencies. Two accelerometer receivers detect the energy transmitted through the medium. By digitizing the analog receiver outputs, and recording the signals for spectral analysis, surface wave velocities can be identified. Modifications to the SASW method includes the reduction of boundary reflections as adopted on the surface waves before the point where the reflected compression waves reach the receivers. In this study, the correlation between the surface wave velocity and the compressive strength of cement mortar is developed using one 36"x36"x4"(91.44$\times$91.44$\times$91.44 cm) cement mortar slab of 2,000 psi (140 kgf/$\textrm{cm}^2$) and two 36"x36"x4"(91.44$\times$91.44$\times$91.44 cm) cement mortar slabs of 3,000 psi (210 kgf/$\textrm{cm}^2$).

• 대한전자공학회논문지SP
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• 제47권5호
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• pp.1-8
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• 2010

본 논문에서는 헤드폰 재생 환경에서의 머리 밖 음상정위를 위한 음상 외재화(externalization) 기법을 제안한다. 제안된 기법에서는 기존의 머리전달함수(HRTF) 또는 초기 반사음 등을 이용한 외재화 기법들에서 발생하는 정위된 음성의 음색 왜곡을 줄이는 것에 그 초점을 맞춘다. 즉, 제안된 음상 외재화 기법은 모델 기반의 HRTF와 잔향 기법을 결합하고, 전방 음상 외재화의 성능 향상을 위하여 decorrelation 및 spectral notch 필터링 기법 등을 포함한다. 제안된 음상 외재화 기법의 성능을 평가하기 위하여 백색잡음, 효과음, 음성 및 오디오 등 다양한 장르의 음원을 이용하여, 평가자의 주관에 의한 청취평가를 수행하였다. 제안된 음상 외재화 알고리즘은 성능평가 결과에서 기존의 방법에 비해 더 좋은 외재화 거리 성능을 보였다.

• 한국음향학회지
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• 제38권3호
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• pp.266-274
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• 2019

국내 문화예술공간에 대한 통계조사에서 나타나듯이, 국내의 많은 공연시설들은 노후화에 따른 크고 작은 규모의 개보수가 필요한 상태이다. 그러나 이와 같은 기존공간의 음향개보수과정에서 참고가 될만한 사례연구가 많지 않은 실정이다. 본 연구는 문화재로써 많은 제약조건을 갖는 SH고등학교 강당을 대상으로 초기 음향검토에서부터 사용자의 요구조건 및 문제점들을 고려한 대안의 수립 그리고 대안들의 적용에 따른 음향성능평가과정 및 그 결과를 분석함으로써 음향리노베이션 설계의 참고자료를 제공하고자 하였다. 개선방안들의 적용결과, 실의 잔향특성이 개선되었으며 언어명료도 및 음악명료도가 개선되었음을 확인하였다. 그러나 라우드니스는 목표한 수준에 미치지 못하였으며 이는 천장에 적용된 슬랫형 구조가 강한 반사음을 제공하지 못하기 때문인 것으로 분석되었다.

• 영어영문학
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• 제56권2호
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• pp.301-328
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• 2010

Many recent British novels engage with the construction and deconstruction of history and identity; and in dealing with these historical, or historicised novels it seems to be an untouchable ground that truth is beyond grasp. Even when approached, its authenticity should be examined under the post-modern "incredulity toward metanarrative" discourses. Julian Barnes's 1998 novel England, England may be one of these. Yet, unlike others it achieves a complicated and controversial status as a new kind of historiographic metafiction by providing selfconscious reflections on the invention of innocence and the questionable notion of historical authenticity against the background of current postmodern historical, cultural, and literary explorations. The book, set in a near-future, namely post-post-modern England, starts with a story of a young girl, Martha Cochrane, whose first memory goes back to her early infantile years. Yet, the narrator comments that it is a lie, "her first artfully, innocently arranged lie," since memory, or history, is a product of identity, and vice versa. Her memory of the jigsaw puzzle is both a reminiscent and a significant component of who she is now, both a simulacrum and the original of herself. The correlation between her individual memory and identity parallels that of a region, England, in formation of its history and nationality. "England, England" is the replicated miniature of the former glorious Kingdom as well as a becoming der Ding an sich (the thing itself). In search of the English history and identity, the author satirizes the modern mind's perception of the unreliability and arbitrariness of memory and history, and further explores the alternative to the postmodern discourses by suggesting the probability of inventing innocence glimpsed in children's face "believing while disbelieving." In doing so, the author reconstructs not only the history of Englishness on the ground where nothing seems to be solid, but more importantly also the postmodern theme of relativity in relation to memory, history and identity.

• 한국음향학회지
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• 제31권3호
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• pp.115-128
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• 2012

본 연구는 확산체의 확산계수 측정결과를 바탕으로 확산체의 설치가 홀 내부 음장분포에 미치는 영향에 대하여 알아보았다. 오케스트라쉘이 설치된 600석 규모의 축소모형 홀을 측정대상으로 이용하였다. 잔향실법 흡음률 측정을 통해 1: 25 축소모형의 벽체와 객석부 재료 (관객 및 의자)가 선정되었고, 만석 시 잔향시간을 기준으로 컴퓨터 시뮬레이션과 대응되도록 제작하였다. 다양한 확산체 부착위치에 따른 물리적 음장의 변화를 측정하기 위해 반구 확산체를 측벽, 발코니전면, 천장 등 부위별로 7가지 조합을 만들어, 확산체 유/무에 따른 음향지표의 변화를 측정하였다. 사용된 음향지표는 잔향시간 (RT), 초기감쇠시간 (EDT), 명료도 (C80), 중심시간 (Ts), 음압레벨 (G)과 더불어 임펄스리스펀스의 자기상관함수 (ACF)로부터 도출되는 Temporal diffusion (TD)을 이용하였다. 실험결과, 확산체 설치에 따라 흠음력과 확산면적이 증가하였고, 이에 따라 평균 RT, 평균 EDT, 평균 G는 감소하는 경향을 보였다. 또한 확산체 설치로 인해 초기반사음의 방향전환이 활발하게 발생했고, 평균 TD은 측정 케이스에 따라 6.05에서 6.30의 값을 보였다. 확산체 설치에 가장 민감한 지표는 RT (R = 0.94)로 나타났고, TD와 EDT의 상관관계 (R = 0.73)가 높은 것으로 나타났다. 확산체 설치부위의 영향은 각 음향지표의 변화양상을 통해 논의되었다.