• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.78-78
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• 2017

강우레이더 관측의 정확도는, 호우의 강도나 형태와 같은 기상학적 조건(변동 오차 요소) 외에도, 관측 지점의 레이더로부터의 거리, 고도, 관측유역의 형태나 크기 등 다양한 관측환경 조건(고정 오차 요소)에 의해서도 달라질 수 있기 때문에, 강우레이더 관측의 오차 성분을 정량화할 필요가 있다. 본 연구에서는 거리와 고도에 의한 오차 특성을 이중편파 변수의 특성을 이용하여 실증적으로 분석하였고, 이를 통해 감쇠의 영향과 산지효과(또는 지형효과)로 인한 오차 규모를 정량적으로 산정 비교하였다. 거리가 멀어짐에 따라 고도도 높아지기 때문에 QPE 불확실도의 거리와 고도에 따른 성분을 구분하는 것은 매우 어려운데, 거리에 대한 불확실도 성분이 매우 작은 R(KDP)를 이용한다면 효과적으로 분리가 가능하다. 이러한 원리를 이용하여, 관측 거리에 따른 오차가 매우 작은 R(KDP)를 기준으로 관측 거리에 따른 오차와 고도에 따른 오차를 분리하여 표준화[Z-score] 하였다. R(Z)의 경우는 관측 고도와 거리에 따른 오차가 중첩되어 나타나나, R(KDP)는 거리에 따른 오차는 거의 나타나지 않으므로 이를 기본 가정으로 하여 R(Z)와 R(KDP) 관계로부터 관측 고도에 따른 오차 성분만 분리하였다. 분리 결과, 관측 거리에 따른 표준 오차의 경우 100km 까지는 대략 10%(0.1) 이하로 나타났으나, 150km 이상에서는 30%(0.3)를 초과하는 것으로 나타났다. 관측 고도에 따른 표준 오차의 경우 2~3번째 고도각 까지는 대략10%(0.1) 이하로 나타났으나, 3번째 고도각 이상에서는 20%(0.2), 4번째 고도각 이상에서는 50%(0.5)를 초과하는 것으로 나타나, 고도에 의한 영향이 거리에 의한 영향보다 민감하게 나타났다. 1번째 고도각에서는, 100km 이내 근거리에서 관측 거리가 가까워질수록 오차가 증가하는 경향을 보이는데, 이는 저고도 빔 간섭(빔 차폐) 등의 영향으로 추정되었다.

• The KIPS Transactions:PartB
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• v.19B no.4
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• pp.221-224
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• 2012

The most famous algorithm of splitting and connecting Snake for extracting the boundary of multiple objects is the nearest method using the distance between snake points. It often can't split and connect Snake due to object topology. In this paper, its problem was discussed experimentally. The new algorithm using vector between Snake segment is proposed in order to split and connect Snake with complicated topology of objects. It is shown by experiment of two test images with 3 and 5 objects that the proposed one works better than the nearest one.

• Journal of Advanced Navigation Technology
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• v.28 no.1
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• pp.15-20
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• 2024

The utilization of small unmanned aerial vehicles (UAVs) has expanded into both military and civilian domains, increasing the necessity for research to ensure operational safety and the efficient utilization of airspace. In this study, the calculation of minimum separation distances for the safe operation of small UAVs at low altitudes was conducted. The determination of minimum separation distances requires a comprehensive analysis of the total system errors associated with small UAVs, necessitating sensitivity analysis to identify key factors contributing to flight technology errors. Flight data for small UAVs were acquired by integrating the control system of an actual small UAV with a flight simulation program. Based on this data, operational scenarios for small UAVs were established, and the minimum separation distances for each scenario were calculated. This research contributes to proposing methods for utilizing calculated minimum separation distances as crucial parameters for ensuring the safe operation of small unmanned aerial vehicles in real-world scenarios.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.4
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• pp.314-318
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• 2013

Tests and evaluations following the U.S. MIL-HDBK/STANDARD were successfully conducted to assure the performance of the air-to-surface guidance kit which was developed first in Korea. Various ground tests confirmed the operation capability and reliability of the guidance kit, and flight tests proved very good mid-range gliding performance and accuracy of the gliding bomb which was a general purpose bomb with the guidance kit.

• 도로교통
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• s.93
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• pp.38-49
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• 2003

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.4
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• pp.278-285
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• 1990

It is well know that optical oupler that is composed of the polished single-mode optical fiber can separate two arbitrary wave lengths. Wavelength division ranges of the WDM optical coupler that is made of the bending fiber with radius R vary with the center wavelength of the signal and spacing between two cores. In this paper, when optical fiber is fixed with the radius R, We proposed the spacing between two cores that can provide minimum division range. Also, We proposed the minimum radius R necessary to separate two arbitary wavelengths of the signal.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.3
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• pp.295-304
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• 2008

This paper comprises two specific objectives. The first is to examine the applicability of Ordinary Kriging interpolation(OK) to finite element method that is based on variogram modeling in conjunction with different allowable limits of separation distance. The second is to investigate the accuracy according to theoretical variograms such as polynomial, Gauss, and spherical models. For this purpose, the weighted least square method is applied to obtain the estimated new stress field from the stress data at the Gauss points. The weight factor is determined by experimental and theoretical variograms for interpolation of stress data apart from the conventional interpolation methods that use an equal weight factor. The validity of the proposed approach has been tested by analyzing two numerical examples. It is noted that the numerical results by Gauss model using 25% allowable limit of separation distance show an excellent agreement with theoretical solutions in literature.

• Journal of Advanced Navigation Technology
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• v.14 no.6
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• pp.808-816
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• 2010

Spectrum sharing between wireless systems becomes a critical issue due to emerging new technologies and spectrum shortage. Since WRC-07 allocated 3400-3600MHz band for the coming fourth generation (4G) or IMT-Advanced on a co-primary basis along with existing Fixed Wireless Access (FWA), it requires spectrum sharing studies to solve the interference problems between two systems. In this paper, I propose the separation distance between service coverages as a sharing fundamental criterion based on the interference to noise power ratio (I/N) received in a FWA base station from several IMT-Advanced base stations on the cellular systems. Especially, some results imply that I/N values compared to the worst case can be greatly reduced with MIMO SDMA interference mitigation technique of IMT-Advanced base stations so that these two systems can co-exist in the same frequency with appropriate separation distance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.8
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• pp.1011-1017
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• 2019

This paper proposes reinforcement learning to solve the node-disjoint path problem which establishes multipath for reliable data transmission in wireless ad-hoc networks. The node-disjoint path problem is a problem of determining a plurality of paths so that the intermediate nodes do not overlap between the source and the destination. In this paper, we propose an optimization method considering transmission distance in a large-scale wireless ad-hoc network using Q-learning in reinforcement learning, one of machine learning. Especially, in order to solve the node-disjoint path problem in a large-scale wireless ad-hoc network, a large amount of computation is required, but the proposed reinforcement learning efficiently obtains appropriate results by learning the path. The performance of the proposed reinforcement learning is evaluated from the viewpoint of transmission distance to establish two node-disjoint paths. From the evaluation results, it showed better performance in the transmission distance compared with the conventional simulated annealing.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.7
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• pp.27-35
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• 1999

Researches on the recognition of handwritten script have been conducted under the assumption that the isolated recognition units are provided as inputs. However, in practical recognition system designs, providing the isolated recognition unit is an challenge due to various writing syles. This paper proposes an approach for segmenting words from lines of unconstrained handwritten text, without help of recognition. In contrast to the conventional approaches which are based on physical gaps between connected components, clues that reflect the author's writing style, in terms of spacing, are extracted and utilized for the segmentation using a simple neural network. The clues are from character segments and include normalized heights and intervals of the segments. Effectiveness of the proposed approach compared with the conventional connected component based approaches in terms of word segmentation performance was evaluated by experiments.