• Journal of the Korean Society for Railway
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• v.16 no.5
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• pp.365-371
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• 2013

This study describes impact test methods for a rolling-stock windscreen executed in Korea and Europe. Air-pressurized impact test equipment for the front windscreens of high speed trains was designed and manufactured. The equipment is capable of launching a projectile at 500km/h, in accordance with EN 15152's impact test method. Calibration of the test equipment was conducted to find an equation relating air pressure and projectile velocity. Specimens ($1000mm{\times}700mm$) having similar specifications with the front windscreens in metro and conventional trains were used to conduct impact tests with this equipment to research the impact characteristics of the screens according to the impact velocity.

• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.2072-2072
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• 2009

최근 연구들에서, 증강 현실(Augmented Reality; AR) 환경에서의 촉각 상호작용에 대한 가능성이 논의되었다. 비젼 기반의 트래킹을 기초로 한 증강 현실 기술은 미리 정의된 2차원 마커(marker)를 이용하여, 카메라로부터 획득된 실시간 영상 위에 가상 물체를 증강한다. 그러나, 카메라로부터 획득된 데이터는 몇몇 오차 요인들, 예를 들어 마커의 위치를 인식하는데 나타나는 오차, 카메라 안에 존재하는 센서 잡음 등으로 인해서 마커 잡음(마커를 인식하면서 나타나는 잡음)이 불가결하게 발생하게 된다. 이러한 이유로 인해서, 사용자가 한 손에는 마커를, 다른 한 손으로는 촉감 장치를 이용하여, 마커에 증강된 물체를 만질 때, 마커 잡음은 힘의 떨림(force trembling)을 발생시킨다. 심지어, 이러한 현상은 정지된 마커에 증강된, 마커가 움직이지 않는 상황에서도 발생한다. 게다가, 마커 위에 증강된 물체가 약간 빠른 속도로 이동하게 될 경우, 측정된 이동 거리는 연속적인 프레임(frame)들 간의 불연속적일 수 있다. 만약 사용자가, 대략 30Hz로 위치와 방향이 갱신되는 가상물체를 촉각적으로 상호작용하려 한다면, 계산되는 반력은 급작스런 힘의 변화를 생성하게 될 수도 있다. 이러한 현상을 극복하기 위해서, 마커 잡음을 최소화하기 위해서 정적 임계값(constant threshold)을 이용할 뿐만 아니라, 보간법을 같이 사용한 방법이 있었다. 하지만, 이러한 방법은 정적 임계값을 이용하고, 영상 프레임 갱신 속도와(video frame rate)와 촉각 프레임 갱신 속도가 일정하다는 가정을 사용하였기 때문에, 여전히 힘의 불연속적인 발생이 나타난다. 따라서, 이 논문에서는 두 가지 방법을 이용하여 증강 현실 내에서, 발생할 수 있는 힘의 불연속적인 변화를 보정하는 두 가지 방법, 잡음 제거를 위한 확장된 칼만 필터(Extend Kalman Filter)와 영상과 촉각 갱신 속도 차이에 따른 갑작스런 힘의 변화를 제거하기 위한 적응적 외삽법(Adaptive Extrapolation method)을 제안한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.1
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• pp.67-76
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• 2011

An exact curved path has to be fixed and velocity profile for travelling on the curved path is required by a moving stage. In this study, we decide the curved path on the basis of the information on three point locations. The path of the moving stage is traced by simulating the designed curve path and the velocity profile, and the results are compared with the given three points to determine how closely the moving stage follows the given path. Further, we propose a method to calibrate a curved path and velocity profile. The proposed moving paths were evaluated by performing experiments. Finally, the designed curved path and the actual path were compared.

• Journal of Korean Society of Transportation
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• v.26 no.5
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• pp.73-80
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• 2008

ALINEA algorithm, which is one of the best on-ramp metering algorithms, was designed to control the traffic volume from on-ramp in order to maintain the optimal occupancy rate of the detectors installed downstream of the merge area. But, the reliability of occupancy rate estimated from the loop detectors, which are used most commonly in Korea, is relatively lower than other parameters such as speed and volume. Moreover, because occupancy rate depends on the length of loop detectors and site, lots of calibration work is required whenever they are installed in order to estimate the occupancy rate. Therefore, there exists room for improvement of ALINEA algorithm because only occupancy rate having some problems is considered as a control parameter in ALINEA algorithm. Practically it is difficult to measure or perceive the occupancy rate for traffic engineers and drivers. On the other hand, speed can be good alternative which can overcome the defect induced by using occupancy. In this study, occupancy based ALINEA algorithm is converted to speed based ALINEA assuming the linear relationship between density and speed.

• International Journal of Highway Engineering
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• v.11 no.1
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• pp.59-67
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• 2009

With the development of high-cost vehicle detectors, low-cost detectors have also been studied due to the advantage that more detectors are provided within limited budgets. This study proposed a method to estimate vehicle speeds using vehicles' track data from auto manufacturers and time stamps obtained when vehicles' tires pass an inclined sensor (here, a tape switch sensor). In speed estimation, small vehicles and large vehicles is distinguished according to the ratio of time stamps for a wheelbase and a rear track obtained from a tape switch sensor. In particular, speed estimation can be adjusted through a parameter to determine vehicles' size so as to take into account location properties such as vehicles' classification ratio. The low-cost vehicle detector with an inclined sensor proposed in this study is expected to be widely utilized to monitor traffic conditions thanks to low cost.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.1
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• pp.27-34
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• 2016

The type of ultrasound transducer used influences the quality of a reconstructed ultrasound image. This study analyzed the effect of transducer type on ultrasound computed tomography (UCT) image quality. The UCT was modeled in an ultrasound simulator by using a 5 cm anatomy model and a ring-shape 5 MHz 128 transducer array, which considered attenuation, refraction, and reflection. Speed-of-sound images were reconstructed by the Radon transform as the UCT image modality. Acoustic impedance images were also reconstructed by the delay-and-sum (DAS) method, which considered the speed of sound information. To determine the optimal combination of transducers in observation, point-source, flat, and focused transducers were tested in combination as trasmitters and receivers; UCT images were constructed from each combination. The combination of point-source/flat transducer as transmitting and receiving devices presented the best reconstructed image quality. In UCT implementation, the combination of a flat transducer for transmitting and a point transducer for receiving permitted acceptable image quality.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.37 no.3
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• pp.101-108
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• 2019

Due to recent improvements in computer processing speed and image processing technology, researches are being actively carried out to combine information from camera with existing GNSS (Global Navigation Satellite System) and dead reckoning. In this study, developed a vision-based positioning assistant algorithm to estimate the distance to the object from stereo images. In addition, GNSS/on-board vehicle sensor/vision based positioning algorithm is developed by combining vision based positioning algorithm with existing positioning algorithm. For the performance analysis, the velocity calculated from the actual driving test was used for the navigation solution correction, simulation tests were performed to analyse the effects of velocity precision. As a result of analysis, it is confirmed that about 4% of position accuracy is improved when vision information is added compared to existing GNSS/on-board based positioning algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.9
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• pp.1180-1186
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• 2020

One of the Embedded systems Tiny Processing Unit (TPU) usually acts in harsh environments like external shock or insufficient power. In these cases, data could be polluted, and cause critical problems. As a solution to data pollution, many embedded systems are using Error Correcting Code (ECC) to protect and restore data. However, ECC processing in TPU increases the overall processing time by increasing the time of instruction fetch which is the bottleneck. In this paper, we propose an architecture of parallelized ECC block to the reduce bottleneck of TPU. The proposed architecture results in the reduction of time 10% compared to the original model, although memory usage increased slightly. The test is evaluated with a matrix product that has various instructions. TPU with proposed parallelized ECC block shows 7% faster than the original TPU with ECC and was able to perform the proposed test accurately.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.16-16
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• 2022

영상유속계는 영상을 이용한 비접촉식 유속계로 하천과 같은 넓은 범위의 유속 및 유량을 간편하게 측정할 수 있다는 장점이 있어 현재 국내외에서 영상유속계의 실용화 연구가 수행되고 있다. 특히 유속 및 유량을 측정하기 위해 카메라 외에 별도의 측정 장비가 필요없기 때문에 드론에 장착하여 표면유속을 측정하는 연구 또한 활발히 이루어지고 있다. 기존 드론 영상을 이용한 표면유속 측정 연구에서는 드론을 측정하고자 하는 하천 영역 위에서 정지하여 영상을 촬영하여 표면유속을 측정하고 있다. 이때 한 화면에 하폭이 다 담기지 않는 넓은 하천의 경우 촬영 위치를 옮겨서 다시 영상을 촬영하거나 하폭이 담길 때까지 비행 고도를 높여 촬영하고 있다. 하지만 촬영 위치를 옮겨 촬영하는 방식의 경우 넓은 하천을 다 담기 위해 여러 번의 촬영을 하고 이를 정합하는 과정이 필요하다는 단점이 있으며 비행 고도를 높여 촬영하는 방식의 경우 촬영 품질 저하로 인해 측정한 유속의 불확도가 크게 산정된다는 단점이 있다. 이에 본 연구에서는 드론을 이동하며 촬영한 연속적인 영상을 이용하여 하천의 표면유속을 측정하는 방법에 대한 연구를 수행하였다. 하천을 가로질러 비행하며 촬영한 드론 이동영상을 활용하면 폭이 넓은 하천의 경우도 간편하게 유속 분포를 측정할 수 있다. 이동영상을 이용하여 유속을 측정하기 위해서는 연속된 이동영상 내에서 지표면의 공통된 특징점을 찾아 흔들림 보정 알고리즘을 적용하여 유속을 산정하는 방법과 드론의 이동 속도를 이용하여 영상의 수표면 이동속도와 벡터연산을 적용하는 두가지 방법을 사용할 수 있다. 이 두가지 방법 중 영상 분석에 필요한 전처리 과정이 적고 지표면의 고정점이 필요 없는 드론의 이동속도를 이용한 벡터 연산을 적용하는 방법을 실제 흐름에 적용하였다. 측정한 수표면의 유속을 전자파표면유속계로 측정한 유속과 비교한 결과 평균 5 % 이내의 차이를 보이는 것을 확인하였다. 향후 다양한 흐름 조건과 드론의 비행속도를 변경하여 측정하는 등의 유속 측정 적용성을 검토하는 연구가 수행된다면 하폭이 넓은 하천 등 다양한 조건에서 드론 영상을 이용한 유속 측정이 가능할 것으로 기대한다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.12 s.354
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• pp.55-64
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• 2006

This work proposes a calibration-free 14b 70MS/s 0.13um CMOS ADC for high-performance integrated systems such as WLAN and high-definition video systems simultaneously requiring high resolution, low power, and small size at high speed. The proposed ADC employs signal insensitive 3-D fully symmetric layout techniques in two MDACs for high matching accuracy without any calibration. A three-stage pipeline architecture minimizes power consumption and chip area at the target resolution and sampling rate. The input SHA with a controlled trans-conductance ratio of two amplifier stages simultaneously achieves high gain and high phase margin with gate-bootstrapped sampling switches for 14b input accuracy at the Nyquist frequency. A back-end sub-ranging flash ADC with open-loop offset cancellation and interpolation achieves 6b accuracy at 70MS/s. Low-noise current and voltage references are employed on chip with optional off-chip reference voltages. The prototype ADC implemented in a 0.13um CMOS is based on a 0.35um minimum channel length for 2.5V applications. The measured DNL and INL are within 0.65LSB and l.80LSB, respectively. The prototype ADC shows maximum SNDR and SFDR of 66dB and 81dB and a power consumption of 235mW at 70MS/s. The active die area is $3.3mm^2$.