• Nuclear Engineering and Technology
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• 제40권5호
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• pp.419-428
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• 2008

During the overhaul period of nuclear power plants in Korea, an ROV(Remotely Operated Vehicle) enters the cold-leg pipes connected with the reactor to examine the state of the thermal sleeves and their positions in the safety injection nozzles. To measure the positions of the thermal sleeves or scratches with video images recorded during the examination, time-varying camera parameters should be known, such as the focal length and principal points used for the capturing each video image. In this paper, we propose a camera calibration and measurement scheme by using a single image containing two circular grooves of a cylindrical nozzle whose radius and distance are known.

• 천문학회지
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• 제50권1호
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• pp.1-5
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• 2017

Like Hipparcos, Gaia is designed to give absolute parallaxes, independent of any astrophysical reference system. And indeed, Gaia's internal zero-point error for parallaxes is likely to be smaller than any individual parallax error. Nevertheless, due in part to mechanical issues of unknown origin, there are many astrophysical questions for which the parallax zero-point error ${\sigma}({\pi}_0)$ will be the fundamentally limiting constraint. These include the distance to the Large Magellanic Cloud and the Galactic Center. We show that by using the photometric parallax estimates for RR Lyrae stars (RRL) within 8kpc, via the ultra-precise infrared period-luminosity relation, one can independently determine a hyper-precise value for ${\pi}_0$. Despite their paucity relative to bright quasars, we show that RRL are competitive due to their order-of-magnitude improved parallax precision for each individual object relative to bright quasars. We show that this method is mathematically robust and well-approximated by analytic formulae over a wide range of relevant distances.

• 전기학회논문지
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• 제60권3호
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• pp.600-605
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• 2011

This paper shows field test and evaluation results for a wireless vehicle detector with anisotropic magneto-resistive (AMR) sensors. The detector consists of two AMR sensors and mechanical and electronic apparatuses. The AMR sensor senses disturbance of the earth magnetic field caused by a vehicle moving over the sensor and then produces an output indicative of the moving vehicle. In this paper, vehicle speeds are calculated by using two AMR sensors fixed on a board, with constant distance. To test and evaluate the accuracy of the detector in real traffic situations, the detector was installed on a local highway and vehicle speeds and volumes were measured both in a free running and a highly congested traffic. The measurements from the detector are compared with the reference measurements obtained from a traffic camera with the Mean Absolute Percentage Errors (MAPE), which has proved the usefulness of the detector in the field.

• 한국정밀공학회지
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• 제27권6호
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• pp.7-16
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• 2010

Physical fundamentals of ultrashort femtosecond lasers are addressed along with emerging applications for precision manufacturing and metrology. Femtosecond lasers emit short pulses whose temporal width is in the range of less than a picosecond to a few femtoseconds, thereby enabling extremely high peak-power machining with less thermal damages. Besides, the broad spectral bandwidth of femtosecond lasers constructed in the form of frequency comb permits absolute distance measurements leading to ultraprecision positioning control and dimensional metrology.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1090-1095
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• 2008

Track geometry changes 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 objectively assess track irregularity, track geometry should be able to be measured. Practically, railway companies use moving chord method, which 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 the characteristics of measuring device. 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 trolley. This calculates track geometry by surveying absolute coordinates of two points each on both rail heads. The other is EM-120, measures versine with 10m of symmetrical chord length.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2010년도 추계학술발표대회
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• pp.837-840
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• 2010

Wireless Sensor Networks have been proposed for several location-dependent applications. For such systems, the cost and limitations of the hardware on sensing nodes prevent the use of range-based localization schemes that depend on absolute point to point distance estimates. Because coarse accuracy is sufficient for most sensor network applications, solutions in range-free localization are being pursued as a cost-effective alternative to more expensive range-based approaches. In this paper, we proposed a Coefficient Allocated DV-Hop (CA DV-Hop) algorithm which reduces node's location error by awarding a credit value with respect to number of hops of each anchor to an unknown node. Simulation results have verified the high estimation accuracy with our approach which outperforms the classical DV-Hop.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.387-390
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• 2002

In this paper, we accomplish uncertainty evaluation and performance test of the volumetric interferometer using two spherical wavefronts emitted from the ends of two single mode fibers. We verify that the volumetric interferometer has the volume uncertainty of 690nm through the error analysis and it has the resolution of 0.1 0.1$\mu\textrm{m}$ for x axis which is the same order of repeatability for x axis. Also, we obtain the systematic error of $1\mu\textrm{m}$ for $60\times 60\times 20 mm^3$ working volume using self-calibration with an artifact plate.

• Journal of Astronomy and Space Sciences
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• 제16권2호
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• pp.217-266
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• 1999

우리 은하안에서 암혹물질을 찾는 OGLE 프로젝트가 발견한 식쌍성중에서 6개의 대표적인 접촉형쌍성을 선택하여 광도곡선을 분석하여 측광학적인 해를 구하였다. 이들 쌍성들은 태양 근방의 쌍성과 비교할 때 기울기가 낮게 나타났으며, Roche lobe를 채우는 정도인 filling factor는 0.12-0.90로 다양하게 나타났다. 분광관측이 수행되지 않은 쌍성이므로 케플러 궤적과 isochrone 궤적의 교점을 이용한 간접적인 방법으로 쌍성 계열의 질량을 구하고, 이를 기초로 각 쌍성의 절대량과 거리를 구하였다. 이와같은 방법으로 산출한 쌍성들의 거리는 1 kpc - 6 kpc 사이에 분포하는 것으로 나타났다. 이는 주기가 1일 이하인 접촉형 쌍성이 보일 수 있는 한계 거리로 추정하며, 대부분의 접촉형 쌍성은 은하벌지에 속하지 않은 별들이다.

• 한국산학기술학회논문지
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• 제9권5호
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• pp.1225-1233
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• 2008

본 논문은 2D/3D 변환 알고리즘을 제안하였다. 제안된 알고리즘은 2차원 영상의 단일 프레임을 이용한 것으로 실시간 처리가 가능한 알고리즘이다. 제안된 알고리즘은 하나의 프레임에서 객체의 수직 위치 정보를 이용하여 깊이 지도를 생성한다. 실시간 처리와 하드웨어 복잡도를 개선하기 위해 영상 샘플링, 표준 휘도화를 이용한 객체 분할, 그리고 경계 스캔을 이용한 깊이지도 생성 등을 수행하였다. 동영상, 정지영상 모두 적용이 가능하며, 수직 위치 정보를 이용하므로 원거리 영상 혹은 풍경, 파노라마 사진과 같은 영상도 효과적인 입체 효과를 보여줄 수 있다. 제안된 알고리즘은 객체의 움직임 방향 혹은 속도 또는 장면 전환 등에 제약 없이 입체 효과가 가능하다. 제안 알고리즘 검증은 시각적인 방법과 APD(Absolute Parallax Difference)를 이용하여 MTD (Modified Time Difference)방식과의 비교를 수행하였다.

• 스마트미디어저널
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• 제9권3호
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• pp.122-129
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• 2020

전 세계적으로 무증상의 코로나바이러스 감염증-19 감염자가 자신이 감염된 것을 모르고 주변인들에게 전파할 수 있다는 가능성은 국민이 전염병 확산에 대한 불안과 두려움에서 벗어나지 못하고 있다는 점에서 여전히 매우 중요한 이슈이다. 본 논문에서는 K-평균 군집화 알고리즘 및 딥러닝 기반 군중 집계를 이용한 전염병 확진자 접촉 가능성 여부 판단 모니터링 시스템을 제안하였다. 모든 입력 학습 영상에 대해 300회 반복 학습한 결과, PSNR값은 21.51, 전체 데이터 셋에 대한 최종 MAE값은 67.984였다. 이는 확진자와 주변인과의 거리와 감염률 산출, 잠재적 환자 동선 주변 인원의 위험도 순 그룹 및 감염률 예측에 대한 영상 속 화질 정보, 관측치 간의 평균 절대 오차를 의미하며 각 CCTV 장면에서 군중의 수가 4,000명 이하일 때에는 평균 절대 오차 값이 0에 가까움을 증명하였다.