• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.1647-1652
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• 2008

Track geometry consists of tangent and curved lines, which caused undesirable changes in initial track geometry by traffic loads. The bigger the changes are, the worse the riding comfort and running stability of train. This is so-called track irregularity and is the most important quality parameters of ballasted track. To be able to objectively assess track irregularity, track geometry should be able to be measured. Practically, railway companies use moving chord method, this method determine versine values via a chord. The versine is the vertical distance to curve measured in the middle of the chord. This type of method measures only versine of track irregularity curve by transfer function from specific property of measuring tool. In this report, review the characteristics of two types of measuring tools by comparing the measurements. The one is GRP-1000 system, optical surveying system with Total station and lazar prism trolly. This calculates track geometry by surveying absolute coordinates of two points each on both rail heads. The other is Trackmaster, measures versine with 2m of chord length.

• 전자공학회논문지SC
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• 제48권4호
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• pp.10-16
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• 2011

TV 본체를 둘러싸고 있는 외곽의 판을 캐비닛이라 하며 다양한 디자인이 가능하도록 하기위하여 폴리카보네이트와 같은 재질을 사용하여 만든다. 이러한 캐비닛은 사출 성형, 자외선 접합 등의 공정을 거치는 동안 열 변형을 일으키기 쉽다. 심하게 변형이 일어난 불량 캐비닛은 제품의 품질을 저하시키기 때문에 공정에서 제거되어야 한다. 본 논문에서는 TV 캐비닛의 형상 인식을 자동화하기 위하여 개발된 초음파 센서를 사용한 형상인식 시스템에 대하여 소개한다. 즉, 캐비닛 형상 인식을 위한 실험 시스템 구성과 캐비닛의 형상을 판별할 수 있는 평가 지수의 제안 그리고 초음파 거리 측정 시 발생할 수 있는 바이어스치 제거 알고리듬, 캐비닛의 양 불량품 판정을 위한 검사 알고리듬 등의 개발 및 검증 결과에 관하여 소개한다.

• 천문학논총
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• 제27권3호
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• pp.87-93
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• 2012

A low-dispersion fiber feed Littrow-mounted grating spectrometer for education was designed and fabricated. The dispersion element is a reflective type blazed grating Edmundoptics NT 46-075 (spatial frequency 600 lines/mm, dimension $30mm{\times}30mm$, blazed angle 8.6 degree). The optical fiber coupler module for optical guiding from telescope to spectrometer is composed of a multi-mode FC connector - FC connector optical fiber patch cord (core/cladding diameter $50{\mu}m/125{\mu}m$) and two 1.25" throw-tube couplers. The lens for collimating and imaging is a general purpose focal length 50 mm camera lens (f/1.8). The device for optical path control is a rectangular prism (size $25mm{\times}25mm$). The imaging camera sensor is a Meade DSI Pro 2 CCD sensor (black and white, $752{\times}582$ pixels and pixel size $8.3{\mu}m{\times}8.6{\mu}m$). Softwares for data logging and analysis consist of Meade Autostar Suite, NIH imagej and Vernier Logger Pro 3. The wavelength coverage range of the spectrometer is 205 nm at central wavelength 550 nm. The wavelength resolution is 1.7 nm.

• 설비공학논문집
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• 제24권6호
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• pp.515-520
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• 2012

A daylighting system includes three parts; light collector, light transformer and light distributor. A DBLP(Double blind light pipe) daylighting system consists of a double blind light collector, a mirror duct type light transformer and a prism film light pipe distributor. The double blinds for a light collection are used to track the sun's altitude and azimuth movements throughout the day. Behind both sets of blinds is the light transformer, which is based on a rectangular cone shaped light duct. The light transformer was designed to efficiently deliver the light into the light pipe within a 30 degree radial spread for the efficient light into the distributor. In this study, DBLP system efficiency was simulated, evaluated and optimized by Tracepro as a popular ray trace light design simulation program. The results indicated that DBLP system efficiency evaluated a maximum 22.4% in case of Spring/Fall season solar noon time. While the overall average system efficiency in the morning and afternoon is evaluated about 10%.

• 한국광학회지
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• 제1권2호
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• pp.142-148
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• 1990

Sarid형의 감쇠 전반사 구조를 통하여 장거리 표면 프라즈몬을 여기시켜 은-피리딘 경계면에서 표면증강 라만산란 실험을 수행하였다. 장거리 표면 플라즈몬의 여기를 확인하기 위해 은을 $100\AA$으로 증착하여 실험한 결과, 그 진행을 눈으로 볼 수 있었다. 이것을 이용해서 은 표면에 흡착된 피리딘의 라만신호를 관측하여 체적 상태 및 화학적 흡착이 있는 경우의 피리딘의 라만신호와 비교, 분석하였는데 장거리 표면 프라즈몬을 이용한 표면증강 라만산란 실험을 아직까지 보고된 바 없다.

• 정보저장시스템학회논문집
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• 제7권1호
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• pp.19-24
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• 2011

Holographic Data Storage System, one of the next generation data storage devices, is a 2-dimensional page oriented memory system using volume holograms in writing and retrieving process. Recently photopolymer with disc type substrate was selected as a media for the Holographic Data Storage System. The disc tilt occurs when the media rotates and the external disturbance applies. The disc tilt causes the change of the angle between the reference beam and the media, the data cannot be retrieved with the right angle or other data page is retrieved. The tilt is generated in a 2-axis direction (tangential, radial). The tangential tilt direction is the same with the multiplexing plane, while the radial tilt direction is a perpendicular to the multiplexing plane. In this research we propose 2-axis tilt angle servo system. The tilt errors are measured by using external photo detector and the additional red laser. Then the tangential direction tilt is compensated by using the galvano mirror. Also the radial direction tilt is compensated by the rotating prism between the relay lens in the reference field. Finally we confirm the compensation results through the Signal to Noise Ratio(SNR) and Bit Error Rate(BER).

• Wind and Structures
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• 제39권1호
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• pp.31-45
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• 2024

This paper examines the flow characteristics around an inclined prism with a U-shaped cross-section ("U-profile") and investigates the connection between the flow and flow-induced vibrations. The study employs a combined approach that involves wind tunnel experiments and computational fluid dynamics (CFD) using an unsteady Reynolds-averaged Navier-Stokes (RANS) turbulence model. Distinct vortex formation patterns are observed in the flow field surrounding the stationary inclined profile. When the cavity of the profile faces away from the incoming flow, large vortices develop behind the profile. Conversely, when the cavity is oriented towards the oncoming flow, these vortices form within the cavity. Notably, due to the slow movement of these large vortices through the cavity, the frequency at which vortices are shed in the negative inclination case is lower compared to the positive inclination, where they form in the wake. Wind tunnel experiments reveal an intermittent transition between the two vortex formation patterns at zero inclination. Large vortices sporadically emerge both in the cavity and behind the profile. The simulation results demonstrate that when these large vortices occur at a frequency close to the structure's natural frequency, they induce prominent pitch vibrations. This phenomenon is also sought after and presented in coupled vibration experiments. Additionally, the simulations indicate that when the natural frequency of the structure is considerably lower than the vortex shedding frequency, this type of vibration can be observed.

• 한국광학회지
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• 제21권6호
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• pp.247-253
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• 2010

본 논문에서는 에지 방식의 BLU(Backlight unit)에 사용되는 도광판의 구조를 최적화하여 광학시트를 줄이면서 휘도와 균일도 및 시야각을 유지하기 위한 이중구조의 도광판을 설계하고 시뮬레이션을 통해 휘도와 균일도를 알아보았다. 여기에 사용된 복합 도광판은 이중구조의 도광판으로 상부에는 곡률 R을 갖는 프리즘패턴을 형성하고 곡률 R에 따른 휘도와 균일도를 시뮬레이션하였다. 하부에는 V groove 패턴을 회전시켜 상부패턴과 $90^{\circ}$를 이루게 하여 균일도를 확보하였다. 특히, 하부 패턴에서는 외곽의 피치 간격과 중심의 피치간격의 비(최대:최소), 패턴의 개수와 패턴의 분산을 정의할 수 있는 프로그램을 설계하여 V groove 사이의 간격을 결정하였다. 복합 도광판(dual-layer light guide plate, DLGP)의 최적화를 위해 다시 하부 패턴의 개수를 변화시켜 균일도를 알아보았다. 시뮬레이션 결과 복합 도광판을 이용한 BLU는 균일도 90.6%, 시야각 $145^{\circ}$인 특성을 갖는 것을 확인하였다.

• 대한방사선기술학회지:방사선기술과학
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• 제40권1호
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• pp.13-18
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• 2017

본 논문은 GATE (geant4 application for tomographic emission) 시뮬레이션을 이용하여 다양한 모양과 재질의 팬텀에서 CTDI (computed tomography dose index)를 평가하였다. GATE 시뮬레이션은 실린더 기둥, 타원 기둥과 육각 기둥 형태와 물, PMMA (polymethyl methacrylate), polyethylene 그리고 polyoxymethylene 재질의 다양한 지름(1 ~ 50 cm)의 팬텀을 모사하여 $CTD_{I100center}$ 값을 비교하였다. 120 kV, 200 mAs에서 실린더 기둥, 타원 기둥과 육각 기둥의 $CTDI_{100center}$ 값은 각각 11.1, 13.4 그리고 12.2 mGy이었다. 이 결과는 동일 볼륨이지만 팬텀의 형태에 따라 $CTDI_{100center}$ 값의 차이가 있음을 알 수 있다. 그리고 물, PMMA 그리고 polyoxymethylene 팬텀의 $CTDI_{100center}$ 값을 비교했을 때 물질의 밀도가 높을수록 상대적으로 $CTDI_{100center}$ 값이 낮게 측정되었다. 하지만 polyethylene의 경우 지름이 15 cm ($CTDI_{100center}$ : 35.0 mGy) 이 상에서는 PMMA 보다 $CTDI_{100center}$ 값이 증가하였다. 그리고 30 cm ($CTDI_{100center}$ : 17.7 mGy) 이 상의 지름에서는 물 보다 더 높은 $CTDI_{100center}$ 값을 보였다. 본 실험을 통해 팬텀의 재질 및 모양에 따른 $CTDI_{100center}$ 값을 GATE 시뮬레이션을 이용하여 평가하였다. CT 선량 평가시 다양한 재질 및 인체에 가까운 모양의 팬텀을 사용함으로써 좀 더 정확한 환자선량을 평가할 수 있을 것이다.

• Bulletin of the Korean Chemical Society
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• 제27권7호
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• pp.1038-1042
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• 2006

A new type of DTPA-bis-amides (L1-L4) and their Gd(III)-complexes of the type $[Gd(L)(H_2O)]{\cdot}nH_2O$ (5: L1; 6: L2; 7: L3; 8: L4) have been prepared and characterized by analytical and spectroscopic techniques. The X-ray crystal structure of 8 has been determined for structural confirmation. The coordination geometry adopts a tricapped trigonal prism geometry with L4 acting as a chelate octadentate and a water molecule in the coordination sphere. Crystals are monoclinic, $P2_1$, a = 14.468(3), b = 19.235(4), c = 13.527(2) $\AA$ $\beta$ = $107.245(3)^{\circ}$, V = 3595.2(11) $\AA^3$, Z = 4, $D_{calc}$ = 1.570. Significant increases in relaxivities are observed with 6 and 7 as compared with that of $Omniscan^{(R)}$, a commercial MR agent: R1 = 12.46 $mM^{-1}\;s^{-1}$, R2 = 8.76 $mM^{-1}\;s^{-1}$ for 6; R1 = 12.77 nm-1 s-1, R2 = 7.60 mM-1 s-1 for 7; R1 = 4.9 $mM^{-1}\;s^{-1}$, R2 = 4.8 $mm^{-1}\;s^{-1}$ for $Omniscan^{(R)}$. In the case of 5, however, both R1 and R2 are found to be lower to show 2.09 $mM^{-1}\;s^{-1}$, and 1.82 $mM^{-1}\;s^{-1}$, respectively.