• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권9호
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• pp.3782-3796
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• 2020

A three-dimensional (3D) reconstruction is an important research area in computer vision. The ability to detect and match features across multiple views of a scene is a critical initial step. The tracking matrix W obtained from a 3D reconstruction can be applied to structure from motion (SFM) algorithms for 3D modeling. We often fail to generate an acceptable number of features when processing face or medical images because such images typically contain large homogeneous regions with minimal variation in intensity. In this study, we seek to locate sufficient matching points not only in general images but also in face and medical images, where it is difficult to determine the feature points. The algorithm is implemented on an adaptive threshold value, a scale invariant feature transform (SIFT), affine SIFT, speeded up robust features (SURF), and affine SURF. By applying the algorithm to face and general images and studying the geometric errors, we can achieve quasi-dense matching points that satisfy well-functioning geometric constraints. We also demonstrate a 3D reconstruction with a respectable performance by applying a column space fitting algorithm, which is an SFM algorithm.

• 한국항공우주학회지
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• 제45권3호
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• pp.226-232
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• 2017

본 연구에서는 RAE "A" 날개-축대칭 동체 형상을 이용하여 유동흐름 방향, Span 방향과 동체 둘레 방향(${\phi}$ 방향)에 따라 격자에 대한 수렴성 및 비행체의 압력 분포 변화를 수치적으로 연구하였다. 아음속 및 천음속 영역 조건에서 $k-{\omega}$ Wilcox-Durbin+ 난류 모델을 사용하여 2차 정확도의 수치적 해를 예측하는 유동해석을 수행하였다. 아음속 유동 조건에서는 해석결과가 실험결과와 매우 잘 일치하였으나, 충격파가 존재하는 천음속 유동에서는 약간의 차이가 발생하였다. Cubic spline을 사용하는 외삽 방법으로 격자 수렴성을 검토하였다. 외삽 방법을 통해 회전 방향의 격자 조밀도가 격자 수렴성에 가장 큰 영향을 미침을 알 수 있었다. 격자 수렴성에 대한 검토 결과를 바탕으로 더 조밀한 격자를 생성하였다. 이를 통해 특히 RAE-A 형상의 축대칭 동체 표면에서 더 정확한 해석 결과를 얻을 수 있음을 보였다.

• 한국컴퓨터정보학회논문지
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• 제24권9호
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• pp.83-95
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• 2019

Recently, a variety of IoT data is collected by attaching geosensors to many vehicles that are on the road. IoT data basically has time and space information and is composed of various data such as temperature, humidity, fine dust, Co2, etc. Although a certain sensor data can be retrieved using time, latitude and longitude, which are keys to the IoT data, advanced search engines for IoT data to handle high-level user queries are still limited. There is also a problem with searching large amounts of IoT data without generating indexes, which wastes a great deal of time through sequential scans. In this paper, we propose a unified spatial index model that handles both grid and trajectory queries using a cell-based space-filling curve method. also it presents a visualization method that helps user grasp intuitively. The Trajectory query is to aggregate the traffic of the trajectory cells passed by taxi on the road searched by the user. The grid query is to find the cells on the road searched by the user and to aggregate the fine dust. Based on the generated spatial index, the user interface quickly summarizes the trajectory and grid queries for specific road and all roads, and proposes a Web-based prototype system that can be analyzed intuitively through road and heat map visualization.

• 한국안전학회지
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• 제36권5호
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• pp.71-78
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• 2021

There are regularly planned overhaul periods in thermal power plants, which involve the maintenance of the boiler of the power plants. However, thermal power plants workers are always exposed to risk during overhaul periods owing to the narrow space and significant dust inside the boiler. Therefore, it is essential to develop a safety monitoring system that is suitable for operating in this type of environment. In this study, we developed not only a worker three-dimensional (3D)-location monitoring system that can monitor and record the entry/exit of workers, their 3D-location, and fall accidents but also a method to secure the working environment and operation efficiency. This system comprises of a worker tag, which was equipped with an inertial measurement unit, a barometric pressure sensor, and a Bluetooth low energy (BLE), and the tags were given to each worker. In addition, the location of workers inside the boiler was measured using a pedestrian dead reckoning (PDR) method and BLE beacons. The location data of the workers tag were transmitted to the integrated database (DB) server through a gateway, and to the administrator monitoring system. The performance of the system was demonstrated inside an actual thermal power plant boiler, and the accuracy and reliability of the system were verified through a number of repeated tests. These results provide insights on designing a new system for monitoring enclosed spaces.

• 한국산업융합학회 논문집
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• 제7권3호
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• pp.273-279
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• 2004

There are several ways to solve parking problem in the downtown One of them is to manage parking efficiently, that is, to raise use-efficiency of parking place and to help drivers to select easily. When we manage the parking place m the block efficiently, It can prevent disproportion that some parking space is over capacity and the other parking one is under. It causes not only the disproportion of economic efficiency but also the congestion of local road. The precondition to manage parking efficiently is to analyse the parking characteristics. In this study we found out the characteristics of parking vehicles by analyzing the turnover per parking mesh and occupancy rate And we build up total D/B by collecting every information about parking space. We developed the Parking Management System by using GIS with D/B and digital map. The efficient Parking Management System is for convenience of drivers and efficient usage of parking space. And this system is also the basic study to be developed as the total Parking Management System by upgrading every information.

• ETRI Journal
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• 제30권6호
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• pp.871-873
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• 2008

In this letter, we investigate the spectral efficiency of IEEE 802.22 wireless regional area network (WRAN) spectrum overlay when it is used in TV white space. Since 2004, when the FCC published the notice of proposed rule making 04-186 to make use of unused TV spectrum, the IEEE 802.22 working group has been standardizing specifications for WRAN operations. There have been a few papers investigating the spectral efficiency of this, but their analyses were limited to the cases for various guard distances between WRAN base stations. Since WRAN base station (BS) power for WRAN service may differ from country to country, it is important to analyze the spectral efficiency for various WRAN BS powers. In this letter, we analyze the spectral efficiency of WRAN spectrum overlay as a function of the power of WRAN BSs. The simulation results show that spectral efficiency decreases as the power of WRAN BSs and guard distances increase.

• 융합신호처리학회논문지
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• 제12권3호
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• pp.194-198
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• 2011

본 논문에서는 850 MHz 이동 통신 대역에서의 자유공간 빚 오쿠무라-하타 모델 적용하여, 기지국 설치 대상 지역인 러시아 지역의 경로손실 특성을 구하였다. 기존 경로 손실 모델에 측정 대상 지역인 러시아 PNG 지역의 특성을 추가하기 위하여, 최소 자승 평균 기법을 적용하여 측정 지역의 경로 손실 보정값을 구하였다. 이렇게 구한 보정값을 이용하면, 자유 공간 경로 손실 및 하타 경로 손실 설정값과 실제 측정값의 차이가 5 ~ 10 Km 구간에서는 각각 17, 6 dB, 10 ~ 15 Km 구간에서는 각각 28, 14 dB, 15 ~ 20 Km 구간에서는 각각 35, 18 dB의 측정 대상 지역에 대한 구간별 경로 손실 모델을 설정할 수 있었다.

• 한국산업융합학회 논문집
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• 제19권3호
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• pp.133-143
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• 2016

The objective in here is to find the density, stiffness, and strength of truss-wall rectangular (TWR) model which is combined with lattice truss (MLT) inside space. The TWR unit-cell model is defined as a unit cell originated from a solid-wall rectangular (SWR) model and it has an empty space inside. Thus, the empty space inside of the TWR is filled with lattice truss model defined as TWR-MLT. The ideal solutions derived of TWR-MLT are based on TWR with MLT model and it has developed by Gibson-Ashby's theory. To validate the ideal solutions of the TWR-MLT, ABAQUS software is applied to predict the density, strength, and stiffness, and then each of them are compared with the Gibson-Ashby's ideal solution as a log-log scale. Applied material property is stainless steel 304 because of cost effectiveness and easy to get around. For the analysis, SWR and TWR-MLT models are 1mm, 2mm, and 3mm truss diameter separately within a fixed 20mm opening width. In conclusion, the relative Young's modulus and relative yield strength of the TWR-MLT unit model is reasonably matched to the ideal expectations of the Gibson-Ashby's theory. In nearby future, TWR-MLT model can be verified by advanced technologies such as 3D printing skills.t.

• 한국공간구조학회논문집
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• 제10권2호
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• pp.95-103
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• 2010

본 논문에서는 비선형 강성방정식의 정확성 향상에 관해 연구한다. 대공간 구조물은 대경간을 가볍게 만들기 위해 두께비를 얇게 만들어야 하므로, 구조설계시 구조불안정 검토가 중요하다. 쉘형 구조물의 구조불안정은 초기 조건에 매우 민감하게 반응하며, 이는 대변형을 수반하는 비선형 문제에 귀착하게 된다. 따라서 구조불안정을 정확히 알아보기 위해 비선형 강성방정식의 정확성이 향상 되어야 한다. 본 연구에서는 스페이스 트러스를 해석 모델로 하며 접선 강성방정식과 비선형 강성방정식의 두 이론을 프로그램으로 작성하여 비선형 해석을 수행한다. 두 이론의 해석 결과를 비교 고찰하여 비선형 강성방정식의 정확성 및 수렴성 향상에 대해 검토 한다.

• 한국멀티미디어학회논문지
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• 제20권2호
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• pp.298-312
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• 2017

The fourth industrial revolution is expected to show technological innovation that develops among different fields beyond boundaries through the convergence and integration of fields. With the development and convergence of digital technology, users can receive information anywhere in the world. In this paper, we propose an adaptive interaction concept in a various environment by using a mobile robot based on projection augmented reality (AR). Most previous studies have aimed fixed projector or projection for a pre-designed environment. Thus, they provide only limited information. To overcome the abovementioned problem, we provide the adaptive information by implementing a projection AR system that can be mounted on the mobile robot. For that, the mobile robot based on the projection system was defined as Pervasive AR. Pervasive AR is configured with a pervasive display, a pervasive interface, and seamless interaction. The Pervasive AR technology enables the user to access information immediately by expanding the display area into real space, which implies an environment of intuitive and convenient interaction by expanding the user interface. This system can be applied to various areas, such as a home environment and a public space.