• Proceedings of the Korean Information Science Society Conference
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• 2007.10b
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• pp.206-211
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• 2007

현대 그래픽스 장치의 발전은 수년전까지 Pre-Rendered 방식을 사용해서 볼 수 있었던 영상들을 Real-Time Rendering을 통해 실시간으로 인터렉티브하게 제공하고 있다. 이러한 장치의 발전은 게임, 시뮬레이션, 미디어 아트 등의 많은 분야에서 변화를 불러 일으켰으며, 앞으로도 많은 변화를 촉진시킬 것이다. 이러한 변화 중 하나로 기존까지 실시간으로 영상을 생성하기 힘들었던 분야 중의 하나인 미술 기법들의 실시간 재생이 가능해졌다. 본 논문은 미술 기법 중 판화기법과 탁본기법을 가상의 환경에서 모사할 수 있는 어플리케이션인 Virtual Engraving과 Virtual Frottage를 제안한다. Virtual Engraving은 3차원 공간상의 가상의 물체에 대해 3차원 입출력장치와 Bump Mapping을 이용하여 조각행위에 대한 경험을 사용자에게 제공하며, Virtual Frottage는 탁본의 대상을 영상으로 받아들여 영상 처리 기법과 Pixel Shader를 통한 렌더링을 통하여 사용자에게 흥미로운 프로타주 기법의 경험을 제공한다. 두 어플리케이션 모두 시각적인 정보를 통해 사용자에게 미술 기법의 경험을 제공하며, Virtual Engraving의 경우 3차원 입출력장치를 통해 촉각적인 정보를 제공하였고 Virtual Frottage 역시 촉각 피드백을 제공할 수 있도록 연구 중이다. 이러한 미술 기법의 모사 연구는 사용자에게 보다 더 실감적인 경험뿐만 아니라 실 공간에서는 가능하지 않은 여러 효과를 제공할 수 있다.

• Journal of The Geomorphological Association of Korea
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• v.24 no.1
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• pp.1-12
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• 2017

Planting trees is a very common practice in the coastal dunefields of South Korea as a way to stabilize dune landscapes and protect inland residential areas from strong winds and blown sands. On the other hand, disturbing the original foredune environment may deteriorate the ability of coastal landsto recover from coastal erosion after storms, causing a retreat of coastline. However, there is little information of this sort on the surface of forested dunefields. Airborne LiDAR or drone-based mapping is not easily applicable in such areas. In this study, we developed a digital terrain model of Dasari dunefields, Chungnam Province, based on direct topographic surveys with real-time kinematic GPS and total stations. We also analyzed previous two aerial photographs taken in 1947 and 1966, in order to detect an older landforms of the dunefields. Results suggested that there have been little changes in geomorphology of the Dasari dunefields for the last 50 years, despite continued tree plantings. Today, there are remains of U-shaped structures such as blowouts and parabolic dunes in the dunefields.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.346-346
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• 2015

홍수로 인한 인명 및 재산의 피해는 자연재해 중 가장 많은 부분을 차지한다. 홍수의 심각성과 빈도가 증가함에 따라, 홍수 재해와 관련된 경제적 손실을 감소할 필요성에 대해 국제적인 우려가 늘어나고 있다. 홍수로 인해 야기되는 재해는 적절한 예방 대책을 통해 저감시킬 수 있는데 그 중 홍수위험지역을 예측하는 것은 홍수를 완화시킬 중요한 해결책이 될 수 있다. 따라서 미국과 유럽 등에서는 홍수위험지역을 예측하여 실시간으로 국민들에게 정보를 제공해주어 위험성을 미리 인식시키고 대비할 수 있도록 국가적인 지원을 하고 있다. 아직 국내에서는 홍수통제소 등의 국가기관에서 주요 국가하천에서의 홍수위만을 실시간으로 제공하고 있어 홍수위험지도의 제작 및 제공이 필요한 실정이다. 이러한 실시간 홍수위험지도를 제작하기 위한 연구는 지속되어 왔으나 범람구역의 설정 및 복잡한 수리해석 등의 어려움을 동반하여 적용을 위한 노력이 필요한 상황이다. 본 연구에서는 1차원 모형인 FLDWAV 모형을 이용하여 실시간 홍수위험지도 제작을 위한 기초 자료 제공으로 홍수위험지역을 선정해보았다. 국내 홍수예 경보시스템에서 사용하는 FLDWAV 모형을 이용하여 실시간으로 홍수위를 산정하여 홍수위험지역을 선정할 수 있었으며, 그 결과도 홍수흔적도와 상당히 일치하는 것으로 나타났다. 본 연구를 통해 빠르고 정확한 홍수위험지역 선정이 가능할 것으로 판단되며, 정확한 수리계산이 필요한 지역이나 홍수보험의 가입이 필요한 지역의 선정 등에 기여할 수 있을 것으로 판단된다.

• ETRI Journal
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• v.43 no.4
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• pp.603-616
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• 2021

Over the last few years, autonomous vehicles have progressed very rapidly. The odometry technique that estimates displacement from consecutive sensor inputs is an essential technique for autonomous driving. In this article, we propose a fast, robust, and accurate odometry technique. The proposed technique is light detection and ranging (LiDAR)-based direct odometry, which uses a spherical range image (SRI) that projects a three-dimensional point cloud onto a two-dimensional spherical image plane. Direct odometry is developed in a vision-based method, and a fast execution speed can be expected. However, applying LiDAR data is difficult because of the sparsity. To solve this problem, we propose an SRI generation method and mathematical analysis, two key point sampling methods using SRI to increase precision and robustness, and a fast optimization method. The proposed technique was tested with the KITTI dataset and real environments. Evaluation results yielded a translation error of 0.69%, a rotation error of 0.0031°/m in the KITTI training dataset, and an execution time of 17 ms. The results demonstrated high precision comparable with state-of-the-art and remarkably higher speed than conventional techniques.

• Journal of Information Processing Systems
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• v.15 no.3
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• pp.682-693
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• 2019

The traditional classification methods mostly assume that the data for class distribution is balanced, while imbalanced data is widely found in the real world. So it is important to solve the problem of classification with imbalanced data. In Mahalanobis-Taguchi system (MTS) algorithm, data classification model is constructed with the reference space and measurement reference scale which is come from a single normal group, and thus it is suitable to handle the imbalanced data problem. In this paper, an improved method of MTS-CBPSO is constructed by introducing the chaotic mapping and binary particle swarm optimization algorithm instead of orthogonal array and signal-to-noise ratio (SNR) to select the valid variables, in which G-means, F-measure, dimensionality reduction are regarded as the classification optimization target. This proposed method is also applied to the financial distress prediction of Chinese listed companies. Compared with the traditional MTS and the common classification methods such as SVM, C4.5, k-NN, it is showed that the MTS-CBPSO method has better result of prediction accuracy and dimensionality reduction.

• The Journal of Korea Robotics Society
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• v.14 no.1
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• pp.58-64
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• 2019

The paper proposes a stiffness measurement device composed of a measurement part including six indenters and a fixing part including four fixtures. The device is able to make simultaneously measurements of the stiffness of human arm. The six indenters make use of both position and force control schemes sequentially whenever needed. In addition, the loadcells and the digital encoders are attached to the indenters and electric motors, respectively, so that the data can be provided in real time. On the end of the indenter, two-axis potentiometer is attached in order to measure the angle difference between the applied force axis and the axis normal to the skin of human arm, and to convert the force measured on the loadcell into the actual applied force to skin. For this purpose, the mapping between the voltage output and the angle of potentiometer was obtained by fitting it for each axis. Ultimately, the measurement device was able to measure the stiffnesses of six regions of human arm.

• Journal of Power Electronics
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• v.19 no.4
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• pp.1000-1010
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• 2019

The use of internal-model-based linear controller, such as resonant controller, is a well-established technique for the current control of grid-connected systems. Attractive properties for resonant controllers include their two-sequence tracking ability, the simple control structure, and the reduced computational burden. However, in the case of continuous-designed resonant controller, the transient performance is inevitably degraded at a low switching frequency. Moreover, available design methods for resonant controller is not able to realize the direct design of transient performances, and the anticipated transient performance is mainly achieved through trial and error. To address these problems, the zero-order-hold (ZOH) characteristic and inherent time delay in digital control systems are considered comprehensively in the design, and a corresponding hold-equivalent discrete model of the grid-connected converter is then established. The relationship between the placement of closed-loop poles and the corresponding transient performance is comprehensively investigated to realize the direct mapping relationship between the control gain and the transient response time. For the benefit of automatic tuning and real-time adaption, analytical expressions for controller gains are derived in detail using the required transient response time and system parameters. Simulation and experimental results demonstrate the validity of the proposed method.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.4
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• pp.637-644
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• 2019

This paper describes an implementation of a graph-based simultaneous localization and mapping(SLAM) method called the General Graph Optimization. The General Graph Optimization formulates the SLAM problem using nodes and edges. The nodes represent the location and attitude of a robot in time sequence, and the edge between the nodes depict the constraint between the nodes. The constraints are imposed by sensor measurements. The General Graph Optimization solves the problem by optimizing the performance index determined by the constraints. The implementation is verified using the measurement data sets which are open for test of various SLAM methods.

• Advances in Computational Design
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• v.4 no.2
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• pp.91-118
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• 2019

Every year, many people are severely injured or lose their lives in accidents such as fire, chemical spill, public pandemonium, school shooting, and workplace violence. Research indicates that the fate of people in an emergency situation involving one or more hazards depends not only on the design of the space (e.g., residential building, industrial facility, shopping mall, sports stadium, school, concert hall) in which the incident occurs, but also on a host of other factors including but not limited to (a) occupants' characteristics, (b) level of familiarity with and cognition of the surroundings, and (c) effectiveness of hazard intervention systems. In this paper, we present EVAQ, a simulation framework for modeling large crowd evacuation by taking into account occupants' behaviors and interactions during an emergency. In particular, human's personal (i.e., age, gender, disability) and interpersonal (i.e., group behavior and interactions) attributes are parameterized in a hazard-impacted environment. In addition, different hazard types (e.g., fire, lone wolf attacker) and propagation patterns, as well as intervention schemes (simulating building repellent systems, firefighters, law enforcement) are modeled. Next, the application of EVAQ to crowd egress planning in an airport terminal under human attack, and a shopping mall in fire emergency are presented and results are discussed. Finally, a validation test is performed using real world data from a past building fire incident to assess the reliability and integrity of EVAQ in comparison with existing evacuation modeling tools.

• Journal of Information Processing Systems
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• v.16 no.4
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• pp.750-759
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• 2020

The wide application of various integrated location-based services (LBS social) and tourism application (app) has generated a large amount of trajectory space data. The trajectory data are used to identify popular tourist attractions with high density of tourists, and they are of great significance to smart service and emergency management of scenic spots. A hot spot analysis method is proposed, based on spatial clustering of trajectory stop points. The DBSCAN algorithm is studied with fast clustering speed, noise processing and clustering of arbitrary shapes in space. The shortage of parameters is manually selected, and an improved method is proposed to adaptively determine parameters based on statistical distribution characteristics of data. DBSCAN clustering analysis and contrast experiments are carried out for three different datasets of artificial synthetic two-dimensional dataset, four-dimensional Iris real dataset and scenic track retention point. The experiment results show that the method can automatically generate reasonable clustering division, and it is superior to traditional algorithms such as DBSCAN and k-means. Finally, based on the spatial clustering results of the trajectory stay points, the Getis-Ord Gi* hotspot analysis and mapping are conducted in ArcGIS software. The hot spots of different tourist attractions are classified according to the analysis results, and the distribution of popular scenic spots is determined with the actual heat of the scenic spots.