• 한국정보통신학회논문지
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• 제5권2호
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• pp.289-296
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• 2001

본 논문에서는 뒤틀린 니매틱 액정디스플레이를 가변적인 위상마스크로 사용하여 기존의 2진 데이터 영상에 위상변조를 추가하는 방법을 제안한다 이를 위해 액정디스플레이의 위상변조특성을 이론 및 실험적으로 조사하였고, 입사빔 세기가 매우 커지면 위상변조 특성이 변하는 현상이 존재함을 실험적으로 보였다. 위상변조가 가미된 2진 데이터 영상의 저장특성을 실험적으로 조사하기 위해 여덟 장의 홀로그램을 각다중 을 사용해서 Dupont 사의 광폴리머의 한 지점에 기록하였다. 위상변조를 사용하여 Fourier 면 홀로그램을 기록할 경우, 기존의 진폭변조방식만 사용하는 경우에 비해 빔세기 균일도를 높일 수 있어서, 같은 조건에서 더 많은 홀로그램을 기록할 수 있음을 보였다.

• Journal of Positioning, Navigation, and Timing
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• 제11권4호
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• pp.297-304
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• 2022

The models used for ionosphere error correction in positioning using Global Navigation Satellite System (GNSS) are representatively Klobuchar model and NeQuick model. Although these models can correct the ionosphere error in real time, the disadvantage is that the accuracy is only 50-60%. In this study, a method for polynomial modeling of Global Ionosphere Map (GIM) which provides Vertical Total Electron Content (VTEC) in grid type was studied. In consideration of Ionosphere Pierce Points (IPP) of satellites with a receivable elevation angle of 15 degrees or higher on the Korean Peninsula, the target area for model generation and provision was selected, and the VTEC at 88 GIM grid points was modeled as a polynomial. The developed VTEC polynomial model shows a data reduction rate of 72.7% compared to GIM regardless of the number of visible satellites, and a data reduction rate of more than 90% compared to the Slant Total Electron Content (STEC) polynomial model when there are more than 10 visible satellites. This VTEC polynomial model has a maximum absolute error of 2.4 Total Electron Content Unit (TECU) and a maximum relative error of 9.9% with the actual GIM. Therefore, it is expected that the amount of data can be drastically reduced by providing the predicted GIM or real-time grid type VTEC model as the parameters of the polynomial model.

• 로봇학회논문지
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• 제16권2호
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• pp.103-111
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• 2021

This study addresses a low-cost lidar sensor-based glass feature extraction method for an accurate map representation using statistical moments, i.e. the mean and variance. Since the low-cost lidar sensor produces range-only data without intensity and multi-echo data, there are some difficulties in detecting glass-like objects. In this study, a principle that an incidence angle of a ray emitted from the lidar with respect to a glass surface is close to zero degrees is concerned for glass detection. Besides, all sensor data are preprocessed and clustered, which is represented using statistical moments as glass feature candidates. Glass features are selected among the candidates according to several conditions based on the principle and geometric relation in the global coordinate system. The accumulated glass features are classified according to the distance, which is lastly represented on the map. Several experiments were conducted in glass environments. The results showed that the proposed method accurately extracted and represented glass windows using proper parameters. The parameters were empirically designed and carefully analyzed. In future work, we will implement and perform the conventional SLAM algorithms combined with our glass feature extraction method in glass environments.

• 대한의용생체공학회:의공학회지
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• 제28권4호
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• pp.530-538
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• 2007

Magnetocardiography (MCG) is a device to measure the magnetic field from the heart. It is a noninvasive device and takes only few minutes to record magnetocardiogram from a subject. In this study, we compared the difference of MCG data recorded from 56 normal subjects in early twenties (28 males and 28 females, mean $age=21.0{\pm}1.6$ years) and 36 elderly subjects (20 males and 16 females, mean $age=61.9{\pm}6.9$ years) for the analysis of the age and gender difference. A total of 24 parameters used in the analysis were derived from QRS complex, R-wave, T-wave, and ST-T period. As a result, seven parameters including maximum current angle and map angle showed the significant difference (p<0.01 and p<0.05, respectively) between young males and young females. Significant difference (p<0.05) between elderly males and elderly females was found from a parameter, pole distance at T-wave peak. In the comparison of age difference, seven parameters regarding current moment, pole distance, and dynamics showed the significant difference between young and elderly males. Eight parameters also showed significant difference (p<0.05) between two younger and elderly female groups. Results showed that parameters regarding current moment, pole distance, and dynamics might be changed when people get older. In conclusion, gender and age difference should be considered when MCG data are analyzed for certain parameters.

• 한국콘텐츠학회논문지
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• 제12권1호
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• pp.329-337
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• 2012

본 연구의 목적은 퇴행성 슬관절염 환자의 신경근전기자극의 적용이 내측광근의 기능적 변화에 미치는 영향을 알아보기 위해서이다. 퇴행성 슬관절염으로 진단받은 여성 30명을 대상으로 보존적 물리치료를 적용한 대조군 15명과 신경근전기자극치료를 병행한 실험군 15명을 임의 배치하여 주 5회, 총 4주간의 치료후, 실험 전 후의 통증, 대퇴사두근력, 대퇴둘레, 그리고 대퇴각도의 변화를 측정하였다. 실험군에서 대퇴사두근력과 대퇴둘레를 측정한 결과 유의한 증가를 나타내었고, 통증의 측정결과에서는 실험군과 대조군 모두 유의한 감소를 나타내었다. 군 간의 비교에서는 대퇴사두근력과 대퇴둘레에서 유의한 차이가 나타났다. 결과적으로 신경근전기자극을 이용한 내측광근의 선택적 강화가 슬관절염 환자의 통증 감소 및 슬관절의 근 기능을 향상시키는데 효과가 있었음을 확인할 수 있었다.

• 한국생산제조학회지
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• 제21권3호
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• pp.459-464
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• 2012

The point of impact, the shot group, and the flight traces depend on the combination of unique features which decide moving traces of the arrow (paradox of the archer, length of the arrow shaft, weight, angle of the feather, and spline of the arrow shaft). The more dense the impact points in the shot group and the earlier elimination of paradox of the archer, the higher assessment is given for the product. However, there is no way to objectively assess the efficiency and quality of the arrow, and there is no numeric data to be used as the basis for comparison with other products. Although capturing the images of flying arrow using a high-speed motion picture camera is possible, we are limited to observation from specific view angle only. Hence, the criteria for efficiency and quality assessment are mostly based on subjective opinions of experts or hunters, or review on consumers' remarks. In this paper, we propose a hardware composition that are based on three detection frames consisting of line lasers and photo diode arrays without the high-speed motion picture camera. Predicated on measured coordinates data, a nobel method for the archer's paradox measurement, a key parameter that determine the arrow's trajectory, and corresponding numerical analysis model is proposed.

• 로봇학회논문지
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• 제11권4호
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• pp.256-261
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• 2016

An insect-like flapping-wing flying-robot should be able to produce flight forces and control moments at the same time only by flapping wings, because there is no control surface at tail just like an insect. In this paper, design principles for the flapping mechanism and control moment generator are briefly explained, characteristics measured force and moment generations of the robot are presented, and finally controlled flight of the flying robot is demonstrated. The present insect-like robot comprises a lightweight flapping mechanism that can produce a flapping angle larger than $180^{\circ}$ and a control moment generator that produces pitch, roll, and yaw moments by adjusting location of the trailing edges at the wing roots. The measured force and moment data show that the control input angles less than $9^{\circ}$ would not significantly reduce the vertical force generation. It is also observed that the pitch, roll, and yaw control moments are produced only by the corresponding control input. The simple PID control theory is used for the controlled flight of the flying robot, controlling pitch, roll, and yaw motions. The flying robot successfully demonstrated controlled flight for about 40 seconds.

• Structural Engineering and Mechanics
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• 제24권2호
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• pp.137-154
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• 2006

The reliable pushover analysis of RC structures requires a realistic prediction of moment-curvature relations, which can be obtained by utilizing proper constitutive models for the stress-strain relationships of laterally confined concrete members. Theoretical approach of Mander is still a single stress-strain model, which employs a multiaxial failure surface for the determination of the ultimate strength of confined concrete. Alternatively, this paper introduces a simple and practical failure criterion for confined concrete with emphasis on introduction of significant modifications into the two-parameter Drucker-Prager model. The new criterion is only applicable to triaxial compression stress state which is exactly the case in the RC columns. Unlike many existing multi-parameter criteria proposed for the concrete fracture, the model needs only the compressive strength of concrete as an independent parameter and also implies for the influence of the Lode angle on the material strength. Adopting Saenz equation for stress-strain plots, satisfactory agreement between the measured and predicted results for the available experimental test data of confined normal and high strength concrete specimens is obtained. Moreover, it is found that further work involving the confinement pressure is still encouraging since the confinement model of Mander overestimates the ultimate strength of some RC columns.

• Advances in aircraft and spacecraft science
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• 제4권3호
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• pp.237-267
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• 2017

Automatic trajectory re-planning is an integral part of unmanned aerial vehicle mission planning. In order to be able to perform this task, it is necessary to dispose of formulas or tables to assess the flyability of various typical flight segments. Notwithstanding their importance, there exist such data only for some particularly simple segments such as rectilinear and circular sub-trajectories. This article presents an analysis of a new, very efficient, way for an airplane to fly on an inclined circular trajectory. When it flies this way, the only thrust required is that which cancels the drag. It is shown that, then, much more inclined trajectories are possible than when they fly at constant speed. The corresponding equations of motion are solved exactly for the position, the speed, the load factor, the bank angle, the lift coefficient and the thrust and power required for the motion. The results obtained apply to both types of airplanes: those with internal combustion engines and propellers, and those with jet engines. Conditions on the trajectory parameters are derived, which guarantee its flyability according to the dynamical properties of a given airplane. An analytical procedure is described that ensures that all these conditions are satisfied, and which can serve for producing tables from which the trajectory flyability can be read. Sample calculations are shown for the Cessna 182, a Silver Fox like unmanned aerial vehicle, and an F-16 jet airplane.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2021년도 춘계학술대회
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• pp.31-33
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• 2021

본 논문에서는 욜로(You Only Look Once, YOLO) 기반의 손가락 방향 감지 알고리즘을 이용하여 손가락 방향 감지 정확도 향상을 위한 데이터셋을 설계 및 구축하였다. 손가락 방향 감지 성능 향상을 위해 약 200개의 손가락 이미지 데이터셋을 학습하였으며, 손바닥의 각도에 따른 손가락 방향 감지 정확도를 확인하기 위해 서로 다른 각도의 비교군을 각각 50개씩 구성하여 실험하였다. 실험결과, 수평기준 90°도에 근접한 방향에 위치한 손가락 방향 감지 정확도는 다른 각도의 경우보다 더 높게 나옴을 확인하였다.