• 한국산학기술학회논문지
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• 제16권10호
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• pp.6917-6924
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• 2015

인간의 시각구조는 시야각과 가시거리에 의해 형성된다. 그러나 시지각에 기반한 대다수의 공간구조분석이론은 시야각을 반영하고 있지 않거나 평면적인 시야각만을 고려하고 있다. 일부 반영하는 이론들도 시야각에 포함된 부분과 제외된 부분을 이분법적으로 분리시킨 이론으로서 인간의 보편적 주시특성이 배제되어 있다. 본 연구는 아이트래킹 실험을 통하여 시야각의 한계를 실증적으로 파악하고 시야각별 주시확률을 도출하여, 이를 3차원 가시성 분석이론에 적용하였다. 그리고 시야각체 제한이 가능한 공간 시지각 분석어플리케이션을 제작하고 여기에 시야각별 Multiple frustum culling의 개념을 적용하여 그 가능성을 파악하였다. 주시특성 파악은 33명을 대상으로 이동형 아이트래커를 이용하여 임의의 공간에 대한 3분간의 보행과정을 측정한 데이터를 수집하였으며, 각도별로 주시고정 빈도 확률을 분석하여 데이터를 마련하였다.

• 로봇학회논문지
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• 제18권1호
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• pp.53-58
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• 2023

In general, in order to operate an autonomous underwater vehicle (AUV) in an underwater environment, a navigation system such as a Doppler Log (DVL) using a Doppler phenomenon of ultrasonic waves is used for speed and direction estimation. However, most of the ultrasonic sensors in underwater is large for long-distance sensing and the cost is very high. In this study, not only canal neuromast on the fish's lateral lines but also superficial neuromast are studied on the simulation to obtain pressure values for each pressure sensor, and the obtained pressure data is supervised using spherical CNN. To this end, through supervised learning using pressure data obtained from a pressure sensor attached to an underwater vehicle, we can estimate the speed and angle of the underwater vehicle in a quasi-static underwater environment and propose a method for a non-ultrasonic based navigation system.

• 전자공학회논문지CI
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• 제48권5호
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• pp.33-41
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• 2011

본 논문에서는 지상라이다를 사용해 구조물을 측정한 점군데이터가 갖는 중복성을 피하고, 목표 구조물외에 불필요한 정보의 수를 감소시키도록 하는 점군데이터의 무손실 압축 기법을 제안한다. 제안된 방법을 적용하기 위해, 호프 변환을 이용하여 구조물과 지상라이다의 수평방향 사이의 각도를 찾아, 이를 점군데이터의 회전 변환에 적용하였다. 이로써 x축에 평행하도록 구성된 점군데이터에 대한 y좌표의 중복성은 기존의 데이터보다 많아지고, 따라서 압축률도 향상시킬 수 있다. 추가로, 불필요한 데이터를 찾아 정보량을 감소시키는 방법을 적용한다. 하나는 점군데이터를 데시메이션하는 것이고, 다른 하나는 목표 구조물이 갖는 y좌표의 범위를 찾아 목표로 하는 범위내 점군데이터만 추출하는 것이다. 제안한 방법은 실험을 통해 압축률이 향상되었음을 확인할 수 있다. 또한, 별도의 추가 정보 없이 점군데이터의 위치 정보만으로 데이터를 압축할 수 있고, 이 압축알고리듬으로 처리속도를 높일 수 있다.

• 천문학회보
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• 제40권1호
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• pp.61.3-62
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• 2015

Remote-sensing observation is one of the observation methods that provide valuable information, such as composition and surface physical conditions of solar system objects. The Hayabusa spacecraft succeeded in the first sample returning from a near-Earth asteroid, (25143) Itokawa. It has established a ground truth technique to connect between ordinary chondrite meteorites and S-type asteroids. One of the scientific observation instruments that Hayabusa carried, Asteroid Multi-band Imaging Camera(AMICA) has seven optical-near infrared filters (ul, b, v, w, x, p, and zs), taking more than 1400 images of Itokawa during the rendezvous phase. The reflectance of planetary body can provide valuable information of the surface properties, such as the optical aspect of asteroid surface at near zero phase angle (i.e. Sun-asteroid-observer's angle is nearly zero), light scattering on the surface, and surface roughness. However, only little information of the phase angle dependences of the reflectance of the asteroid is known so far. In this study, we investigated the phase angle dependences of Itokawa's surface to understand the surface properties in the solar phase angle of $0^{\circ}-40^{\circ}$ using AMICA images. About 700 images at the Hayabusa rendezvous phase were used for this study. In addition, we compared our result with those of several photometry models, Minnaert model, Lommel-Seeliger model, and Hapke model. At this conference, we focus on the AMICA's v-band data to compare with previous ground-based observation researches.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.571-576
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• 2000

This paper summarized deformation properties of hydroelectric power concrete dam through the comparison between measured and analysed data. This is a part of the process to evaluate concrete dam safety, which has become a critical concern in the country. We analysed strain and angle deformation data by considering only the effect of atmosphere temperature to evaluate deformation properties of Gaisan hydroelectric power concrete dam. Analysis results are almost identical with measured data, and behavior of Gusian dam can be cleared up more reliably in case of acting the external loads (seismic, wind water pressure, etc.) except the influence of temperature.

• Smart Structures and Systems
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• 제33권2호
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• pp.119-131
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• 2024

Drift angle is a significant index for diagnosing post-event structures. A common way to estimate this drift response is by using modal parameters identified under natural excitations. Although the modal parameters of shear structures cannot be identified accurately in the real environment, the identification error has little impact on the estimation when measurements from several floors are used. However, the estimation accuracy falls dramatically when there is only one accelerometer. This paper describes the susceptibility of single sensor identification to modelling error and simulations that preliminarily verified this characteristic. To make a robust evaluation from measurements of one floor of shear structures based on imprecisely identified parameters, a novel scheme is devised to approximately correct the mode shapes with respect to fictitious frequencies generated with a genetic algorithm; in particular, the scheme uses constrained minimization to take both the mathematical aspect and the realistic aspect of the mode shapes into account. The algorithm was validated by using a full-scale shear building. The differences between single-sensor and multiple-sensor estimations were analyzed. It was found that, as the number of accelerometers decreases, the error rises due to insufficient data and becomes very high when there is only one sensor. Moreover, when measurements for only one floor are available, the proposed method yields more precise and appropriate mode shapes, leading to a better estimation on the drift angle of the lower floors compared with a method designed for multiple sensors. As well, it is shown that the reduction in space complexity is offset by increasing the computation complexity.

• 대한족부족관절학회지
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• 제14권2호
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• pp.157-160
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• 2010

Purpose: The purpose of this study is to find out the correlation factors for prognosis of calcaneal fractures. Materials and Methods: 120 cases (feet) of calcaneal fractures, all of them followed up for more than 1 year after surgical procedures, consisted of 101 men (105 feet) and 13 women (15 feet) were reviewed retrospectively. The collected clinical data were as follows : injury mechanism, surgical procedures, time to procedure, time to work and the radiologic data: Bohler angle, heel width, displacement of posterior facet. AOFAS hindfoot score and VAS score were checked. With ANOVA test and multiple regression analysis, the data processed statistically. Results: According Sanders classification, type II was 37 cases (31%), type III 66 cases (55%), and type IV 17 cases (14%). On plane radiography, the Bohler angle improved to average 28.4 degree from 5.6 degree, and the displacement of posterior facet was corrected to average 1.2 mm. AOFAS hindfoot score was checked average 81.7 points postoperatively, and the meaningful difference existed between types of Sanders classification. The Bohler angle represented the outline of the calcaneus had the better correlation with the clinical outcome of calcaneal fractures rather than the anatomical reduction of the posterior facet did. And the width of calcaneus had good correlation with the clinical score. Conclusion: We should also concern about the outline of calcaneus, the width of calcaneus and the Bohler angle representing anatomical reduction, not only the acute reduction of the posterior facet.

• Journal of Astronomy and Space Sciences
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• 제27권4호
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• pp.337-343
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• 2010

Optical observation system provides angle-only measurement for orbit determination of space object. Range measurement can be directly acquired using laser ranging or tone ranging system. Initial orbit determination (IOD) by using angle- only data set shows discrepancy according to the measurement time interval. To solve this problem, range measurement data should be added for IOD. In this study, two-site optical observation was used to derive the range information. We have observed nine geostationary earth orbit satellites by using two-site optical observation system. The determination result of the range shows the accuracy over 99.5% compared to the results from the satellite tool kit simulation. And we confirmed that the orbit determination by the Herrick-Gibbs method with the range information obtained from the two-site observation is more accurate than the orbit determination by Gauss method with the one-site observation. For more accurate two-site optical observation, a baseline should satisfy an optimal condition of length and more precise observation system needed.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.504-507
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• 2006

Airborn Lidar technology has been applied to diverse applications with the advantages of accurate 3D information. Further, Lidar intensity, backscattered signal power, can provid us additional information regarding target's characteristics. Lidar intensity varies by the target reflectance, moisture condition, range, and viewing geometry. This study purposes to generate normalized airborne LiDAR intensity image considering those influential factors such as reflectance, range and geometric/topographic factors (scan angle, ground height, aspect, slope, local incidence angle: LIA). Laser points from one flight line were extracted to simplify the geometric conditions. Laser intensities of sample plots, selected by using a set of reference data and ground survey, werethen statistically analyzed with independent variables. Target reflectance, range between sensor and target, and surface slope were main factors to influence the laser intensity. Intensity of laser points was initially normalized by removing range effect only. However, microsite topographic factor, such as slope angle, was not normalized due to difficulty of automatic calculation.

• 한국CDE학회논문집
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• 제12권1호
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• pp.1-7
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• 2007

In this paper, we present a machining time estimation algorithm for 5-axis high-speed machining. Estimation of machining time plays an important role in process planning and production scheduling of a shop. In contrast to the rapid evolution of machine tools and controllers, machining time calculation is still based on simple algorithms of tool path length divided by input feedrates of NC data, with some additional factors from experience. We propose an algorithm based on 5-axis machine behavior in order to predict machining time more exactly. For this purpose, we first investigated the operational characteristics of 5-axis machines. Then, we defined some dominant factors, including feed angle that is an independent variable for machining speed. With these factors, we have developed a machining time calculation algorithm that has a good accuracy not only in 3-axis machining, but also in 5-axis high-speed machining.