• Journal of Advanced Navigation Technology
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• v.27 no.2
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• pp.182-189
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• 2023

Depth estimation is a key technology in 3D map generation for autonomous driving of vehicles, robots, and drones. The existing sensor-based method has high accuracy but is expensive and has low resolution, while the camera-based method is more affordable with higher resolution. In this study, we propose self-attention-based unsupervised monocular depth estimation for UAV camera system. Self-Attention operation is applied to the network to improve the global feature extraction performance. In addition, we reduce the weight size of the self-attention operation for a low computational amount. The estimated depth and camera pose are transformed into point cloud. The point cloud is mapped into 3D map using the occupancy grid of Octree structure. The proposed network is evaluated using synthesized images and depth sequences from the Mid-Air dataset. Our network demonstrates a 7.69% reduction in error compared to prior studies.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.4
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• pp.607-616
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• 2022

A new axial flux permanent magnet machine with soft magnetic composited cores is proposed for electric vehicle application in this paper. The windings and soft magnetic composited cores can be designed to form a very compact structure, and; thus, the torque density can be improved greatly. To obtain the a good flux concentrating ability, two toroidally wound internal stator machines are designed and analyzed, and the designed motor is with NdFeB magnet for high-performance electric vehicle application. The 3-D finite-element method is used to analyze the electromagnetic parameter and performance, for performance comparison, a commercial axial flux permanent magnet machine is used. The proposed motor reduced weight about 5.8%, produced torque higher than about 8Nm for existing motor.

• Journal of KIISE:Databases
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• v.30 no.3
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• pp.225-236
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• 2003

MOLAP systems store data in a multidimensional away called a 'cube' and access them using way indexes. When a cube is placed into disk, it can be Partitioned into a set of chunks of the same side length. Such a cube storage scheme is called the chunk-based MOLAP cube storage scheme. It gives data clustering effect so that all the dimensions are guaranteed to get a fair chance in terms of the query processing speed. In order to achieve high space utilization, sparse chunks are further compressed. Due to data compression, the relative position of chunks cannot be obtained in constant time without using indexes. In this paper, we propose a bitmap index for chunk-based MOLAP cubes. The index can be constructed along with the corresponding cube generation. The relative position of chunks is retained in the index so that chunk retrieval can be done in constant time. We placed in an index block as many chunks as possible so that the number of index searches is minimized for OLAP operations such as range queries. We showed the proposed index is efficient by comparing it with multidimensional indexes such as UB-tree and grid file in terms of time and space.

• Journal of Korea Game Society
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• v.10 no.6
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• pp.157-168
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• 2010

A terrain is an essential element for constructing a virtual world in which game characters and objects make various interactions with one another. Creating a terrain requires a great deal of time and repetitive editing processes. This paper presents a 3D terrain reconstruction system to create 3D terrain in virtual space based on real terrain data. In this system, it converts the coordinate system of the height maps which are generated from a stereo camera and a laser scanner from global GPS into 3D world using the x and z axis vectors of the global GPS coordinate system. It calculates the movement vectors and the rotation matrices frame by frame. Terrain meshes are dynamically generated and rendered in the virtual areas which are represented in an undirected graph. The rendering meshes are exactly created and updated by correcting terrain data errors. In our experiments, the FPS of the system was regularly checked until the terrain was reconstructed by our system, and the visualization quality of the terrain was reviewed. As a result, our system shows that it has 3 times higher FPS than other terrain management systems with Quadtree for small area, improves 40% than others for large area. The visualization of terrain data maintains the same shape as the contour of real terrain. This system could be used for the terrain system of realtime 3D games to generate terrain on real time, and for the terrain design work of CG Movies.

• Journal of Navigation and Port Research
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• v.46 no.4
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• pp.367-374
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• 2022

The purpose of this study was to propose a deep learning algorithm that applies to the fault diagnosis of fuel pumps and purifiers of autonomous ships. A deep learning algorithm reflecting the time dependence of the measured signal was configured, and the failure pattern was trained using the vibration signal, measured in the equipment's regular operation and failure state. Considering the sequential time-dependence of deterioration implied in the vibration signal, this study adopts Conv1D with sliding window computation for fault detection. The time dependence was also reflected, by transferring the measured signal from two-dimensional to three-dimensional. Additionally, the optimal values of the hyper-parameters of the Conv1D model were determined, using the grid search technique. Finally, the results show that the proposed data preprocessing method as well as the Conv1D model, can reflect the sequential dependency between the fault and its effect on the measured signal, and appropriately perform anomaly as well as failure detection, of the equipment chosen for application.

• Korean Journal of Remote Sensing
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• v.22 no.4
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• pp.243-253
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• 2006

As the ocean and beaches have suffered from the losses of sand, it is necessary to monitor the zones that are prone to erosion continuously with the object of the long-term management. However, each ward offices are busy trying to supply sand without analyzing the marine and beach topographic changes. Therefore a long term effect of erosion has not been shown. In this study, we proposed methods to collect accurate spatial data of the oceans and beaches through sounding and GPS surveys, and detected and analyzed topographic changes quantitatively and qualitatively, by using an integrated RS and GIS techniques. The result of this study revealed that the marine topography has been eroded for 25 years, because of the straight construction of the river and the vast development of urban features, in addition with change of the mean depth 0.40 m, the water surface area 11,028 $m^2$, and submarine volume 2,207,884 $m^3$. The beach topography has accreted for 5 years and the change of the mean elevation is 0.27m, the area 6,501 $m^2$, and volume 25,667 $m^3$, because of the installation of geogrids and the seasonal effect. We conducted monitoring works on the topographic survey of the ocean and beaches and analyzed the present condition of the coastal erosions. Therefore, it is estimated that necessary information on the supply of sand, the safe marine leisure and the management of bating place could be provided.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.4
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• pp.577-584
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• 2021

Electrical energy is an essential component in present societies, which is an important basis for our technological society. In the design of new power infrastructure, it is important to consider the psychological aspects of how our culture considers and aspects its development as an integral component of the community environment. The construction of new high voltage overhead transmission lines has become a controversial issue for public policy of government due to social opposition. The members of community are concerned about how these power lines may have an impact on their lives, basically caused by their effects on health and safety. The landscape and visual impact is one of the most impact that can be easily perceived for local community. The computer 3D simulation of new landscape is illustrated by a real life use corresponding to the selection of the power line route with least observability for local community. This paper used ArcGIS(geographic information system tool) for planning, survey, basic route and detailed route, route for implementation of transmission line corridor. Also, the paper showed the map of natural environment, living environment, safety and altitude using database of power line corridor, and transmission siting model was developed by this study. The suggested landscape of computer simulation with lowest visibility on a power line zone can contribute to reducing oppositions of local community and accelerating the construction of new power lines.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.153-153
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• 2011

현대 건축은 기능적이고 합리적이었지만 획일적이었던 박스형 건축에서 탈피해 형태와 공간에 있어서 다양한 변화를 시도하고 있다. 특별한 건축물의 실현을 위해 각 나라의 기술력은 급속한 발전을 이루었고, 보다 더 독특한 건축물에 대한 관심은 비정형 건축물에 대한 관심의 증대로 이어지고 있다. 이러한 비정형 건축물에 적합한 구조로써 프리폼(Free-Form) 구조가 있다. 프리폼 구조로 입체골조(Double Layered Structure)를 많이 사용하였으나, 최근 유리로 되어 투명하고 기하학적 모양의 건축물을 추구함에 따라 평면골조(Single Layered Structure)가 증가하고 있는 추세이다. 평면골조는 축력 지배형과 모멘트 지배형으로 분류할 수 있고 프리폼 구조의 구성 요소 중 가장 취약하고 중요한 부분은 노드이다. 본 연구에서는 프리폼 구조 중 가장 큰 관심이 고조되고 있는 평면골조 모멘트 지배형의 노드에 대한 국내외 기술 분석을 통해 향후 연구 방향성을 제시하고자 한다. 입체골조는 하나의 노드에 여러개의 부재가 3차원으로 결합되어야 하기 때문에 다른 골조 시스템에 비해 노드부가 복잡하지만, 건축물의 외관을 유리로 하여 투명하게 하고 비틀리고 구부러진 구조물에 대한 건축적 요구가 많아짐에 따라 평면골조의 인기가 높아지고 있다. 이러한 시대의 흐름에 발맞추어 건물의 구조적, 기하학적 요구를 충족시키기 위해 다양한 노드 시스템이 개발 중이며, 가해지는 하중의 특성에 따라 축력 지배형과 모멘트 지배형으로 구분하여 노드의 양상을 분류할 수 있다. 축력 지배형의 대표적인 시스템은 다이아그리드(Diagrid)이다. 축력 지배형 프리폼 구조의 노드는 전체 구조물의 하중을 축력으로 받아 모두 전달해야 하기 때문에 크기가 크고 가새가 2~4개층에 걸쳐서 설치되기 때문에 중량이다. 모멘트 지배형 노드를 갖는 프리폼 구조의 형태는 대부분 지붕 구조로써 지붕 자체의 하중만을 견디도록 설계된다. 따라서 노드부와 노드에 붙는 부재들이 가볍기 때문에 사람이 들 수 있고 노드의 크기가 작아 시공성이 좋으며 대량 생산이 가능하다는 장점이 있다. 노드의 형태는 힘의 흐름과 쓰임에 따라 다양하다. 평면골조 모멘트 지배형의 노드는 접합방식에 따라 Splice node connection과 End-Face node connection 두 가지로 분류할 수 있다. Splice node connection은 각 부재의 종축으로 노드와 구조부재 사이에 이음재를 두어 연결하고, 연결 형태에 따라 전단력을 전달할 수 있는 1~2개의 접촉면이 생긴다. 전단응력을 받는 볼트로 이음재를 이어 조립하거나 용접으로 접합할 수 있다. 대표 노드로, SBP-1, SBP-2와 POLO-1 등이 있다. End-Face node connection은 각 연결된 부재의 단부와 노드 사이의 연결면은 종축방향의 수직이고, 인장응력을 받는 볼트를 사용하거나 용접에 의해 접합할 수 있다. 대표 노드로 SBP-4, WABI-1, MERO-1(Cylinder), MERO-2(Block), MERO-4(Double Dish) 등이 있다. 본 기술 현황 분석을 통해 현재 개발된 노드를 분류하고 가장 관심이 높은 Single Layer 모멘트 지배형 노드를 비교, 분석하였다. 최근 건물의 경향을 반영한 프리폼 구조를 실현하기 위해서 필수적인 노드의 개발은 국외에서 활발히 연구되고 있지만 그 기술이 개방되어 있지 않다. 국내에서는 동대문 디자인 플라자에 새로운 노드를 적용하고 고려대학교에서 모멘트 지배형 노드를 개발하는 등 발전 가능성을 보이고 있지만 국외 사례들에 비하면 아직 초기 단계라 할 수 있다. 따라서 현장 용접을 지양하고 공장 제작하여 현장에서 조립하며, 프로젝트 별로 상이한 노드를 사용하는 것이 아닌 다양한 요구를 효과적으로 수용하는 구조 효율성을 향상시킨 노드 상세의 개발이 이루어져야 할 것이다.

• Journal of the Korean Geotechnical Society
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• v.29 no.7
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• pp.75-89
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• 2013

This paper describes a GIS-based geohydrologic methodology, called YSGWF (YonSei GroundWater Flow) for predicting the rainfall infiltration-groundwater flow of slopes. This physical-based model was developed by the combination of modified Green-Ampt model that considers the unsaturated soil parameters and GIS-based raster model using Darcy's law that reflects the groundwater flow. In the model, raster data are used to simulate the three dimensional inclination of bedrock surface as actual topographic data, and the groundwater flow is governed by the slope. Also, soil profile is ideally subdivided into three zones, i.e., the wetting band zone, partially saturated zone, and fully saturated zone. In the wetting band and partially saturated zones the vertical infiltration of water (rainfall) from surface into ground is modeled. When the infiltrated water recharges into the fully saturated zone, the horizontal flow of groundwater is introduced. A comparison between the numerical calculation and real landslide data shows a reasonable agreement, which indicate that the model can be used to simulate real rainfall infiltration-groundwater flow.

• Clean Technology
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• v.28 no.4
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• pp.316-322
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• 2022

The flow pattern at the inlet of the catalyst layer in a selective catalytic reduction (SCR) system is one of the key parameters influencing the performance of the denitrification process. In the curved diffusing parts between the ammonia injection grids and the catalyst layers, guide vanes are installed to improve flow uniformity. In the present study, a numerical simulation has been performed to investigate the effect of the geometrical configuration of the guide vanes on the aerodynamic characteristics of a denitrification facility. This application has been made to the existing SCR process in a large-scaled coal-fired power plant. The flow domain to be solved covers the whole region of the flow passages from the exit of the ammonia injection gun to the exit of the catalyst layers. ANSYS-Fluent was used to calculate the three-dimensional steady viscous flow fields with the proper turbulence model fitted to the flow characteristics. The root mean square of velocity and the pressure drop inside the flow passages were chosen as the key performance parameters. Four types of guides vanes were proposed to improve the flow quality compared to the current configuration. The numerical results showed that the type 4 configuration was the most effective at improving the aerodynamic performance in terms of flow uniformity and pressure loss.