• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.198.1-198.1
• /
• 2012

저궤도 위성이 발사체에서 분리된 후 탑재 소프트웨어에 의한 초기 동작이 수행되고 나면 초기 운용이 시작된다. 초기 운용 기간에 수행할 모든 절차와 대처 가능한 긴급 상황이 발생할 경우 수행할 절차는 발사 전에 미리 준비된다. 위성의 각 부분의 설계 마진은 최악 조건을 기준으로 반영되어 있기 때문에 발사 이후의 버스 시스템 관점에서의 위성 특성은 요구 사항을 만족하는 범위가 될 것으로 예상이 가능하다. 실제로 발사 후 위성 텔레메트리 분석을 통해 대부분의 항목에서 요구 조건을 만족하는 것으로 확인되었다. 또한 텔레메트리 분석을 통해 설계 단계에서 예상했던 것 보다 정확한 궤도 특성이 반영된 위성 특성을 파악하였다. 이러한 특성은 설계 시 고려했던 상황과 다르더라도 실제 궤도 특성이 반영된 특성이므로 초기 운용 및 정상 운용 시에 정상적인 상황인 것으로 고려해야 한다. 첫째, 지구 알베도 특성에 따라 태양센서 값이 궤도에 따라 변화한다. 위성의 자세가 정확히 태양을 지향하고 있더라도 태양센서에 지구에서 반사된 빛이 입사되어 자세 제어에 영향을 주게 된다. 알베도의 영향은 적도에서 극지방으로 갈수록 커지며, 계절에 따라 다른 특성을 보인다. 알베도의 영향을 최소화하기 위해 자세 제어 모델에 알베도 효과를 고려하거나 알베도 효과를 무시할 수 있을 정도로 자세 제어 오차 한계를 조정할 수 있다. 둘째, 위성의 지구 회피 회전에 의해 태양 전지판의 온도가 궤도에 따라 변화한다. 위성체는 위성체에 장착된 두 개의 별센서의 가시성 확보를 위해 태양 지향 자세에서 요축으로 일정 속도로 회전한다. 남극 부근에서는 두 태양 센서가 모두 지구의 반대편인 남쪽을 지향하도록 하며, 북극 부근에서는 북쪽을 지향하도록 한다. 이 때 두 태양 센서의 방향에 장착된 태양 전지판은 극지방에서 지구 반대편에 위치하므로 다른 태양 전지판에 비해 낮은 온도를 갖게 된다. 이 논문에서는 위성의 궤도 특성에 따른 고려 사항에 대해 설명하였다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.10A
• /
• pp.784-795
• /
• 2009

An accurate positioning estimation in the wireless sensor networks (WSN) is very important in which each sensor node is aware of neighbor conditions. The multi-hop positioning estimation technique is considered as one of the suitable techniques for the WSN with many low power devices. However geographical holes, where there is no sensor node, may severely decrease the positioning accuracy so that the positioning error can be beyond the tolerable range. Therefore in this paper, we analyze error factors of DV-hop and hole effect to obtain node's accurate position. The proposed methods include boundary node detection, distance level adjustment, and unreliable anchor elimination. The simulation results show that the proposed method can achieve higher positioning accuracy using the hole detection and enhanced distance calculation methods compared with the conventional DV-hop.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.6
• /
• pp.83-89
• /
• 2021

To improve the performance of self-driving cars, the introduction of V2X, a communication technology that connects vehicles, infrastructure, and vehicles, is essential. Even if traffic information of the other vehicle is known, the structure of the intersection and a distance calculation algorithm are required for accurate calculations at roundabouts. This paper proposes a design algorithm for a rotating intersection and implemented in Matlab that complies with the national design rules and enables accurate calculations. Assuming the roundabout and the entrance/exit path to be a circle, a method for measuring the distance between vehicles at an arbitrary point was proposed using the horizontal shift of the entrance circle to the main circle. The algorithm could be used in fully autonomous vehicles by designing a roundabout suitable for the terrain by arbitrarily varying the angle between branches and the radius of curvature of the entrance and exit roads, and transmitting a warning signal when a collision between two driving vehicles is expected.

• Korean Journal of Construction Engineering and Management
• /
• v.13 no.3
• /
• pp.67-77
• /
• 2012

O Having a highly reliable plan for the process and estimating an accurate construction period during the early stages of a construction project can prevent falsifying the plan and reduce the occurrence of construction delays. Moreover, it allows a succession of swift and accurate decisions to happen. The difficulty in obtaining an accurate estimate of the construction period is especially prominent in high-rise building projects because the works involved are very complicated and costly. As such, it is important that research is done to find out the impacts a reliable plan and good estimate of the construction period can bring with regards to the monthly work efficiency and success of a high-rise building project. However, due to the difference in climatic conditions at high altitude and surface level, the current way of calculating work efficiency in a typical project is inaccurate for a high-rise building project. With that, this paper aims to compute the work efficiency with height, taking into consideration the change in climatic elements at different working heights. A comparison of the results according to the climatic features of each city can also be done in this paper. According to the results calculated in work altitudes, the work efficiency in Busan falls the most. On the other hands, the work efficiency in Seoul falls the least. The reason these results are shown is the influence of wind speed at high altitude. The estimation of work efficiency at high altitude would be used for estimating construction period, feasibility studies, and selecting a city of high-rise building projects.

• Korean Journal of Cognitive Science
• /
• v.26 no.1
• /
• pp.53-67
• /
• 2015

Metacognitive monitoring refers to high dimensional cognitive activities. Understanding one's own cognitive processes accurately can make effective controls for their performance. Brain area related with metacognition is PFC which is completed the order of late and it can be inferred that monitoring abilities is developing during late adolescent. In this study, we explored the developmental difference in monitoring accuracy between high school students and college students using by measuring JOL(Judgment of Learning). Participants was asked that they study Spanish-Korean word pairs and judge their future performance of memory. In the result, people in both groups thought that they could remember word pairs better than their actual performance. Absolute bias scores which mean the degree to predict their performance apart from true scores showed the interaction between subject groups and task difficulty. Specifically, people judged their learning state quite accurately in easy task condition. However, in difficult task condition, both groups showed inaccuracy for predicting their learning and the magnitude of the degree was bigger in the group of high school students.

• Journal of Internet Computing and Services
• /
• v.11 no.2
• /
• pp.61-72
• /
• 2010

This paper addresses the problem of moving object localization using Ultra-Wide-Band(UWB) range measurement and the method of location accuracy improvement of the indoor moving object. Unlike outdoor environment, it is difficult to track moving object position due to various noises in indoor. UWB is a radio technology that has attention for localization applications recently. UWB's ranging technique offer the cm accuracy. Its capabilities for data transmission, range accurate estimation and material penetration are suitable technology for indoor positioning application. This paper propose a positioning algorithm of an moving object using UWB ranging technique and particle filter. Existing positioning algorithms eliminate estimation errors and bias after location estimation of mobile object. But in this paper, the proposed algorithm is that eliminate predictable UWB range distance error first and then estimate the moving object's position. This paper shows that the proposed positioning algorithm is more accurate than existing location algorithms through experiments. In this study, the position of moving object is estimated after the triangulation and eliminating the bias and the ranging error from estimation range between three fixed known anchors and a mobile object using UWB. Finally, a particle filter is used to improve on accuracy of mobile object positioning. The results of experiment show that the proposed localization scheme is more precise under the indoor.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.1
• /
• pp.259-266
• /
• 1990

Leaks at the piston seal and the by-pass port of a small volume prover have relatively large influence on the proving accuracy in comparison with a conventional ball prover. The pulse interpolator, which is to increase the discrimination, is affected by the characteristic of the flowmeter signal. In this study, a small volume prover of the double cylinder type was designed in order to study the pulse interpolation error as well as the leak error. The basic volume of the prover determined by a water draw method was about 9.68L. Experimental results revealed that interpolation data attained by the repeated piston pass for turbine meters at a fixed flowrate may be treated effectively by applying a statistical method. It was possible to limit the pulse interpolation error less than .+-. 0.02% at the 95% confidence level. However, in the case of the bulk meter, if failed to achieve the required repeatability level because of the pulse characteristics. The basic volume change appeared to be independent of the piston velocity within the .+-. 0.05% of tolerance.

• Journal of Chest Surgery
• /
• v.31 no.7
• /
• pp.730-734
• /
• 1998

Background: It is important to know the location, number, size and shape of bullae before thoracotomy or VATS bullectomy. Chest X-ray and chest CT may be used but with some limitation. The purpose of this study was to compare the diagnostic value of thoracography with that of chest X-ray in preoperative detection of bullae. Meterial and Method: Thoracography was performed by injection of non-ionic water-soluble dye into pleural space in 22 primary spontaneous pneumothoraces, which underwent thoracotomy or VATS bullectomy. Chest X-ray and thoracography were compared through operative finding. Results: Sensitivity and accuracy of thoracography(75% and 72.7%) were higher than those of chest X-ray(30% and 36.4%). However, specificity of thoracography(50%) was lower than that of chest X-ray (100%). There were no complications during or after thoracography. Conclusion: Thoracography is a safer and more useful method for preoperative detection of bullae when compared with chest X-ray.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.11 no.2
• /
• pp.23-40
• /
• 1974

Semisubmersible 해양석유시추선의 기본설계에 필요한 파랑중(波浪中)에서 운동(運動)을 계산(計算)하는 이론적방법(理論的方法)을 제시하고 "MOHOLE"과 "SEDCO 1350-F" 석유시추선들의 운동(運動)을 해석하였다. 이 규칙파에서 운동계산을 불규칙해양파(波)에 적용하는 응용해석을 보여주었다. 현재 이론적 방법으로는 6자유도(自由度)의 운동을 해양파의 어떤 방향에 대해서도 정확히 계산할 수 있으며 계산의 정확성은 수조(水槽)에서의 모형선의 운동측정치와 실선(實船)의 운동측정치와 비교하여 증명되었다. 또 현재의 방법은 종전에 개발된 방법보다 더 일반적(一般的)인 경우를 다룰 수 있으며 결과치도 더 정확하다. 극소운동특성을 갖는 해양석유시추선과 부체(浮體)해양구조물의 설계는 경비가 비싸고 시간이 많이 드는 모형실험보다는 유체역학적(流體力學的) Parameters를 신속 정확히 자주 변경 검토해야 하는 기본설계단계에서는 정확한 이론적인 전자계산기에 의한 계산방법이 절실히 필요하다. 예상(豫想)과 같은 부가질량(附加質量)과 감쇠력(減衰力)은 Resonance 운동주기에서만 운동에 영향을 준다. 해양구조물에 작용하는 파력(波力)은 Froude-Krilov force, 부가질량(附加質量) 및 감쇠력(減衰力)과 Restoring force로 구성했으며 규칙파(規則波)에서의 6자유도(自由度) 운동방정식은 본 논문에 제시된 실험측정치(値)와 실험으로 정확도가 증명된 이론치(値)의 부가질량과 감쇠력 계수(係數)를 써서 풀었다. 규칙파(規則波)에서의 계산된 운동을 Pierson Moskowitz 해양파(海洋波) 스펙트럼과 linear superposition principle에 의해 불규칙해양파(不規則海洋波)에서의 운동을 계산하는데 사용했다. 불규칙파(不規則波)에서의 운동은 운동스펙트럼과 통계적 운동치로 나타냈다. 현재의 계산방법은 실제 기본설게에 사용되어 왔으며, 다른 응용분야는 파랑중(波浪中)에서의 파면(波面)과 Deck간(間)의 Clearance, 계류선(係留線)의 동장력(動張力)계산의 기본 Data 및 기본설계의 Draft 등 Parameters를 통(通)한 Optimum Design 등(等)이다. 파(波)의 한 방향(方向)에 대(對)한 전자계산기(電子計算機)(IBM 370 또는 CDC 6400)에 의한 운동계산은 10초(秒)미만밖에 안걸린다. 또 현재의 계산방법은 해양석유시추선뿐 아니라 이와 비슷한 부체(浮體)해양구조물과 Pipe-laying선(船) 또 Supply Boat설계(設計)에도 쓰여지고 있다.

• The Journal of the Korea Contents Association
• /
• v.21 no.3
• /
• pp.23-32
• /
• 2021

Semantic image segmentation technology in the field of computer vision is a technology that classifies an image by dividing it into pixels. This technique is also rapidly improving performance using a machine learning method, and a high possibility of utilizing information in units of pixels is drawing attention. However, this technology has been raised from the early days until recently for 'lack of detailed segmentation' problem. Since this problem was caused by increasing the size of the label map, it was expected that the label map could be improved by using the edge map of the original image with detailed edge information. Therefore, in this paper, we propose a post-processing algorithm that maintains semantic image segmentation based on learning, but modifies the resulting label map based on the edge map of the original image. After applying the algorithm to the existing method, when comparing similar applications before and after, approximately 1.74% pixels and 1.35% IoU (Intersection of Union) were applied, and when analyzing the results, the precise targeting fine segmentation function was improved.