• Nuclear Engineering and Technology
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• 제51권3호
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• pp.825-836
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• 2019

One of the most challenging safety precautions for workers in dynamic, radioactive environments is avoiding radiation sources and sustaining low exposure. This paper presents a sampling-based algorithm, DL-RRT*, for minimum dose walk-path re-planning in radioactive environments, expedient for occupational workers in nuclear facilities to avoid unnecessary radiation exposure. The method combines the principle of random tree star ($RRT^*$) and $D^*$ Lite, and uses the expansion strength of grid search strategy from $D^*$ Lite to quickly find a high-quality initial path to accelerate convergence rate in $RRT^*$. The algorithm inherits probabilistic completeness and asymptotic optimality from $RRT^*$ to refine the existing paths continually by sampling the search-graph obtained from the grid search process. It can not only be applied to continuous cost spaces, but also make full use of the last planning information to avoid global re-planning, so as to improve the efficiency of path planning in frequently changing environments. The effectiveness and superiority of the proposed method was verified by simulating radiation field under varying obstacles and radioactive environments, and the results were compared with $RRT^*$ algorithm output.

• 전기학회논문지
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• 제57권2호
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• pp.294-302
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• 2008

In this paper, we present a new image up-sampling method which registers low resolution images to the high resolution grid when Bayesian super-resolution image processing is performed. The proposed up-sampling method interpolates high-resolution pixels using high-frequency data lying in all the low resolution images, instead of up-sampling each low resolution image separately. The interpolation is based on B-spline non-uniform re-sampling, adjusted for the super-resolution image processing. The experimental results demonstrate the effects when different up-sampling methods generally used such as zero-padding or bilinear interpolation are applied to the super-resolution image reconstruction. Then, we show that the proposed hybird up-sampling method generates high-resolution images more accurately than conventional methods with quantitative and qualitative assess measures.

• 대한원격탐사학회지
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• 제19권5호
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• pp.363-370
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• 2003

This paper describes a rectification procedure that relies on a polynomial model derived from the imaging geometry without loss of accuracy. By using polynomial model, one can effectively eliminate the iterative process to find an image pixel corresponding to each output grid point. With the imaging geometry and ephemeris data, a geo-location polynomial can be constructed from grid points that are produced by solving three equations simultaneously. And, in order to correct the local distortions induced by the geometry and terrain height, a distortion model has been incorporated in the procedure, which is a function of incidence angle and height at each pixel position. With this function, it is straightforward to calculate the pixel displacement due to distortions and then pixels are assigned to the output grid by re-sampling the displaced pixels. Most of the necessary information for the construction of polynomial model is available in the leader file and some can be derived from others. For validation, sample images of ERS-l PRI and Radarsat-l SGF have been processed by the proposed method and evaluated against ground truth acquired from 1:25,000 topography maps.

• 항공우주시스템공학회지
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• 제3권2호
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• pp.24-30
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• 2009

MI LV1B images, geometric corrected data of COMS MI, has no time information per each line, but field of weather prediction using the MI LV1B images needs time information on it. This paper explains two calculation methods for receiving time on lines of MI LV1B images and analyzes difference between two calculation methods using simulated data.

• 한국항공우주학회지
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• 제50권3호
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• pp.157-164
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• 2022

본 논문에서는 무인기의 경로 계획을 위한 산악 지형, 레이더 그리고 방공망 등을 3차원 환경으로 구현하고, Sampling 기반의 경로 계획 알고리즘인 PRM 알고리즘을 사용하여 경로 계획 및 재계획을 수행하는 방안에 대해 서술한다. 기존의 PRM 알고리즘의 경우 생성된 노드 사이에 장애물 존재 여부를 확인하기 위한 계산이 노드 간 1:1로 이루어지고 연속적으로 수행되어 노드 수나 노드를 연결하는 거리에 계산량이 크게 영향을 받는다. 이러한 부분을 개선하기 위해 제안하는 LineGridMask 기법을 통해 장애물 존재 여부 확인 방식을 단순화하고, 병렬화를 통해 경로 계획의 계산 시간을 감소시킨다. 마지막으로 기존 PRM 알고리즘과의 성능을 비교한 결과, 경로 계획에서는 최대 88%, 재계획의 경우 최대 94%까지 계산 시간이 감소하였음을 확인하였다.