• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.42-42
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• 2015

사행수로에서의 원심력은 비선형적인 압력분포를 야기하여 이차류, 편수위 등과 같은 불규칙하고 복잡한 흐름을 발생시킨다. 일반적으로 이들 흐름은 난류이고 매우 3차원적이며 자유수면과의 상호작용이 중요한 역할을 할 수도 있다. 환경, 유사이동, 지형 변화와 관련된 환경 수리학적 관점에서 사행수로에서의 흐름을 이해하고 설계하기 위해서는 이러한 복잡한 3차원 흐름을 정확하게 계산하는 것이 매우 중요하다. 이 연구에서는 유한차분법에 근거한 3차원 흐름해석 모형을 이용하여 사행수로에서의 난류 흐름을 모의하고자 한다. 지배방정식은 3차원 비정상 RANS(Reynolds averaged Navier-Stokes) 방정식이며, 난류 해석을 위해서 공학적으로 널리 이용되고 있는 난류 모형 중 k-omega 모형을 이용한다. 수치모형은 시간과 공간에 대해서 2차 정확도의 이산화 기법을 적용한다. 자유수면의 변동은 이상(two-phase) VOF (volume of fluid) 기법을 이용하여 계산한다. 수치모형의 적용 대상은 기존 문헌에서 제시되어 있는 키노시타 사인곡선을 이용하여 만든 폭 60cm의 사행수로에서 후르드수 0.23 그리고 레이놀즈수 41,700의 조건에서 발생시킨 난류 흐름이다. 적용한 난류모형들을 이용하여 해석한 결과들을 유속벡터분포와 수위의 항으로 비교분석하여 사행수로에서 발생되는 이차류와 편수위 변화 재현에 대한 수치모형의 적용성을 평가하고 각 난류모형들의 특성을 제시한다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.2
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• pp.127-133
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• 2019

Since frequent item extraction so far requires searching for patterns and traversal for the FP-Tree, it is more likely to store the mining data in a tree and thus CPU time is required for its searching. In order to overcome these drawbacks, in this paper, we provide each item with its location identification of transaction data without relying on conditional FP-Tree and convert transaction data into 2-dimensional position information look-up table, resulting in the facilitation of time and spatial accessibility. We propose an algorithm that considers the mapping scheme between the location of items and items that guarantees the linear time complexity. Experimental results show that the proposed method can reduce many execution time and memory usage based on the data set obtained from the FIMI repository website.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.752-755
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• 2009

Recently, the production process system is largely composed automatic system using the wired network. The production process system using wired network has disadvantages that take place expense when the installed and inspected production of equipment was replaced. The each equipment happens to repair cost for control and management in production processes. In this paper, the industrial equipment that applied for IEEE 802.15.4(ZigBee) technology solves a complicated space at the plant. And then when the industrial equipments replace wired network with wireless network, this paper studied its user interface.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.2
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• pp.13-22
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• 2005

To improve the anomaly IDS using system calls, this study focuses on Neural Networks Learning using the Soundex algorithm which is designed to change feature selection and variable length data into a fixed length learning pattern. That is, by changing variable length sequential system call data into a fixed length behavior pattern using the Soundex algorithm, this study conducted neural networks learning by using a backpropagation algorithm with fuzzy membership function. The back-propagation neural networks and Neuro-Fuzzy technique are applied for anomaly intrusion detection of system calls using Sendmail Data of UNM to demonstrate its aspect of he complexity of time, space and MDL performance.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.247-247
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• 2022

제트류는 복잡한 흐름 중 하나로 다양한 크기의 에디가 다양한 운동량을 가지고 있다. 이러한 제트류를 구현하기 위해서는 난류 운동 에너지 등 제트류의 특성을 잘 반영하여야 한다. 제트를 구현하기 위해서는 수리학적 모델, 현장 실험 등 많은 방법이 있으며, 본 연구에서는 상대적으로 공간, 시간적 비용이 적게 드는 수치해석 방법을 사용하여 연구를 진행하였다. 대표적인 수치해석방법에는 DNS(Direct Numerical Simulation), LES(Large Eddy Simulation), RANS(Reynolds Averaged Navier Stokes) 등이 있다. RANS는 시간 평균 흐름 특성만 산출하며 제트의 복잡성을 재현하는 데 한계가 있어, 본 연구는 DNS와 LES 모델을 이용하여 제트류를 구현하는 것에 초점을 맞추었다. DNS는 해당 격자에서 발생하는 모든 에디를 직접 해석 때문에 난류 모델링이 필요하지 않지만, 많은 수의 그리드가 필요하여 수치해석 시 소요시간이 긴 편이다. LES는 대규모 에디는 직접 해석하지만 일정 크기 이하의 소용돌이를 해석하기 위해서 모델이 필요하다. 따라서 서브 그리드 모델에 따라 약간 다른 결과를 보인다. 이러한 문제점을 해결하기 위해 본 연구에서는 LES의 기존 서브 그리드 모델을 사용하지 않고 신경망 모델로 학습한 DNS 결과를 활용하는 방법을 제안한다. 우선 DNS와 LES 모델을 사용하여 에너지 스펙트럼을 비교하여 서브 그리드 모델이 시작하는 파수를 찾는다. 이후 특정 파수 아래의 작은 에디를 모사할 적절한 신경망 모델을 결정하여 DNS의 작은 에디를 신경망 알고리즘이 모사할 수 있도록 학습시킨다. 이후 기존 서브 그리드 모델을 사용하지 않고 학습된 신경망 알고리즘을 사용한 LES 모델이 모사한 제트류와 실제 DNS 모델을 사용한 제트류를 비교 및 평가한다.

• Journal of IKEEE
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• v.27 no.4
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• pp.456-463
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• 2023

In this paper, we introduce the SSResUNet network model, which integrates the SPADE structure with the U-Net network model for accurate land cover classification using high-resolution satellite imagery without requiring user intervention. The proposed network possesses the advantage of preserving the spatial characteristics inherent in satellite imagery, rendering it a robust classification model even in intricate environments. Experimental results, obtained through training on KOMPSAT-3A satellite images, exhibit superior performance compared to conventional U-Net and U-Net++ models, showcasing an average Intersection over Union (IoU) of 76.10 and a Dice coefficient of 86.22.

• Korean Journal of Remote Sensing
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• v.35 no.3
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• pp.483-489
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• 2019

True color images display colors similar to natural colors. This has the advantage that it is possible to monitor rapidly the complex earth atmosphere phenomenon and the change of the surface type. Currently, various organizations are producing true color images. In Korea, it is necessary to produce true color images by replacing generations with next generation weather satellites. Therefore, in this study, visual enhancement for true color image production was performed using Top of Atmosphere (TOA) data of Advanced Himawari Imager (AHI) sensor mounted on Himawari-8 satellite. In order to improve the visualization, we performed two methods of Nonlinear enhancement and Histogram equalization. As a result, Histogram equalization showed a strong bluish image in the region over $70^{\circ}$ Solar Zenith Angle (SZA) compared to the Nonlinear enhancement and nonlinear enhancement technique showed a reddish vegetation area.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.2
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• pp.65-72
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• 2007

As embedded system has strict cost and space constraints, it is impossible to apply conventional fault-tolerant techniques directly for increasing the dependability of embedded system. In this paper, we propose software fault-tolerant mechanism which requires only minimum redundancy of system component. We define an utility metric that reflects the dependability of each embedded system component, and then measure the defined utility of each reconfiguration combinations to provide fault tolerance. The proposed utility evaluation process shows exponential complexity. However we reduce the complexity by hierachical subgrouping at the software level of each component. When some components of embedded system are tailed, reconfiguration operation changes the system state from current faulty state to pre-calculated one which has maximum utility combination.

• Journal of the Korean Institute of Intelligent Systems
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• v.13 no.1
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• pp.6-11
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• 2003

Recently, the modular network was proposed in a way to keep the size of the neural network small. The modular network solves the problem by splitting it into sub-problems. In this aspect, fuzzy systems act in a similar way. However, in a fuzzy system, there must be an expert rule which separates the input space. To overcome this, fuzzy-neural network has been used. However, the number of fuzzy rules grows exponentially as the number of input variables grow. In this paper, we would like to solve the size problem of neural networks using modular network with the hierarchic structure. In the hierarchic structure, the output of precedent module affects only the THEN part of the rule. Finally, the rules become shorter being compared to the rule of fuzzy-neural system. Also, the relations between input and output could be understood more easily in the Proposed modular network and that makes design easier.

• The Transactions of the Korea Information Processing Society
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• v.7 no.10
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• pp.3138-3147
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• 2000

EC(Electronic Commerce) which is cone the virtual space through Internet, has the advantage of time and space. On the contrary, it also has weak point like security probelm because anybody can easily access to the system due to open network attribute of Internet. Theretore, we need the solutions that protect the EC security problem for safe and useful EC activity. One of these solution is the implemonlation of a strong cipher algorithm. YK2(YoungKu Kang) cipher algorithm proposed in this paper is advantage for the EC security and it overcomes the limit of the current 6/1 bits block cipher algorithm using 128 bits key length for input, output, encryption key and 32 rounds. Moreover, it is degigned for the increase of time complexity and probability calculation by adapting more complex design for key scheduling regarded as one of the important element effected to enciyption.