• Journal of Information Processing Systems
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• 제17권4호
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• pp.690-706
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• 2021

Classification is a substantial operation in data mining, and each element is distributed taking into account its feature values in the corresponding class. Metaheuristics have been widely used in attempts to solve satellite image classification problems. This article proposes a hybrid approach, the flower pigeons-inspired optimization algorithm (FPIO), and the local search method of the flower pollination algorithm is integrated into the pigeon-inspired algorithm. The efficiency and power of the proposed FPIO approach are displayed with a series of images, supported by computational results that demonstrate the cogency of the proposed classification method on satellite imagery. For this work, the Davies-Bouldin Index is used as an objective function. FPIO is applied to different types of images (synthetic, Alsat-2B, and Sentinel-2). Moreover, a comparative experiment between FPIO and the genetic algorithm genetic algorithm is conducted. Experimental results showed that GA outperformed FPIO in matters of time computing. However, FPIO provided better quality results with less confusion. The overall experimental results demonstrate that the proposed approach is an efficient method for satellite imagery classification.

• 한국추진공학회지
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• 제22권6호
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• pp.72-83
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• 2018

본 연구에서는 단일 전단 동축 분사기를 이용한 수소 로켓 연소기의 전산유체 해석을 수행하였다. 2차원 축대칭 형상에서 난류연소 해석을 위해 hybrid RANS/LES 난류모델을 적용하였다. 적합한 해석기법을 찾기 위해 3가지 화학 반응기구, 3가지 고해상도 기법 및 3단계 격자해상도 조합을 비교하였다. 벽면 열유속을 실험결과와 비교하여 해석 성능을 살펴보았으며, 유동장 결과 분석으로 동축 분사기를 가지는 로켓 연소기의 난류연소특성을 살펴볼 수 있었다.

• 천문학회지
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• 제53권6호
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• pp.139-147
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• 2020

The sunspot area is a critical physical quantity for assessing the solar activity level; forecasts of the sunspot area are of great importance for studies of the solar activity and space weather. We developed an innovative hybrid model prediction method by integrating the complementary ensemble empirical mode decomposition (CEEMD) and extreme learning machine (ELM). The time series is first decomposed into intrinsic mode functions (IMFs) with different frequencies by CEEMD; these IMFs can be divided into three groups, a high-frequency group, a low-frequency group, and a trend group. The ELM forecasting models are established to forecast the three groups separately. The final forecast results are obtained by summing up the forecast values of each group. The proposed hybrid model is applied to the smoothed monthly mean sunspot area archived at NASA's Marshall Space Flight Center (MSFC). We find a mean absolute percentage error (MAPE) and a root mean square error (RMSE) of 1.80% and 9.75, respectively, which indicates that: (1) for the CEEMD-ELM model, the predicted sunspot area is in good agreement with the observed one; (2) the proposed model outperforms previous approaches in terms of prediction accuracy and operational efficiency.

• Structural Engineering and Mechanics
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• 제83권1호
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• pp.93-108
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• 2022

Real-time hybrid simulation (RTHS) was applied to investigate the train-bridge interaction of a high-speed railway system, where the railway bridge was selected as the numerical substructure, and the train was physically tested. The interaction between the two substructures was reproduced by a servo-hydraulic shaking table. To accurately reproduce the high-frequency interaction responses ranging from 10-25Hz using the hydraulic shaking table with an inherent delay of 6-50ms, an adaptive time series (ATS) compensation algorithm combined with the linear quadratic Gaussian (LQG) was proposed and implemented in the RTHS. Testing cases considering different train speeds, track irregularities, bridge girder cross-sections, and track settlements featuring a wide range of frequency contents were conducted. The performance of the proposed ATS+LQG delay compensation method was compared to the ATS method and RTHS without any compensation in terms of residual time delays and root mean square errors between commands and responses. The effectiveness of the ATS+LQG method to compensate time delay in RTHS with high-frequency responses was demonstrated and the proposed ATS+LQG method outperformed the ATS method in yielding more accurate responses with less residual time delays.

• Advances in concrete construction
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• 제15권5호
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• pp.303-312
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• 2023

The present study investigates the effects of Cattaneo-Christov thermal effects of stagnation point in Walters-B nanofluid flow through lubrication of power-law fluid by taking the slip at the interfacial condition. For the solution, the governing partial differential equation is transformed into a series of non-linear ordinary differential equations. With the help of hybrid homotopy analysis method; that consists of both the homotopy analysis and shooting method these equations can be solved. The influence of different involved constraints on quantities of interest are sketched and discussed. The viscoelastic parameter, slip parameters on velocity component and temperature are analyzed. The velocity varies by increase in viscoelastic parameter in the presence of slip parameter. The slip on the surface has major effect and mask the effect of stagnation point for whole slip condition and throughout the surface velocity remained same. Matched the present solution with previously published data and observed good agreement. It can be seen that the slip effects dominates the effects of free stream and for the large values of viscoelastic parameter the temperature as well as the concentration profile both decreases.

• 한국공간구조학회논문집
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• 제23권1호
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• pp.45-52
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• 2023

This study proposes an RCS composite damping device that can achieve seismic reinforcement of existing buildings by dissipating energy by inelastic deformation. A series of experiments assessing the performances of the rubber core pad, hysteretic steel slit damping device, and hybrid RCS damping device were conducted. The results showed that the ratios of the deviations to the mean values satisfied the domestic damping-device conformity condition for the load at maximum device displacement in each direction, at the maximum force and minimum force at zero displacement, as well as the hysteresis curve area. In addition, three analysis models based on load-displacement characteristics were proposed for application to seismic reinforcement design. In addition, the validity of the three proposed models was confirmed, as they simulated the experimental results well. Meanwhile, as the shear deformation of the rubber-core pad increased, the hysteretic behavior of super-elasticity greatly increased the horizontal force of the damping device. Therefore, limiting the allowable displacement during design is deemed to be necessary.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권10호
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• pp.2701-2717
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• 2023

In this paper, a hybrid fuzzy-based method is suggested for determining India's best system for power generation. This suggested approach was created using a fuzzy-based combination of the Giza Pyramids Construction (GPC) and Recalling-Enhanced Recurrent Neural Network (RERNN). GPC is a meta-heuristic algorithm that deals with solutions for many groups of problems, whereas RERNN has selective memory properties. The evaluation of the current load requirements and production profile information system is the main objective of the suggested method. The Central Electricity Authority database, the Indian National Load Dispatch Centre, regional load dispatching centers, and annual reports of India were some of the sources used to compile the data regarding profiles of electricity loads, capacity factors, power plant generation, and transmission limits. The RERNN approach makes advantage of the ability to analyze the ideal power generation from energy data, however the optimization of RERNN factor necessitates the employment of a GPC technique. The proposed method was tested using MATLAB, and the findings indicate that it is effective in terms of accuracy, feasibility, and computing efficiency. The suggested hybrid system outperformed conventional models, achieving the top result of 93% accuracy with a shorter computation time of 6814 seconds.

• 한국습지학회지
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• 제19권3호
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• pp.271-278
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• 2017

최근 비점오염물질 처리를 위하여 저영향개발(low impact development) 기술이 적용되고 있으며, 레인가든 기술은 생물학적 및 물리화학적 처리에 의하여 비점오염물질 저감에 기여하기에 광범위하게 적용되고 있는 LID 기술 중 하나이다. 그러나 유지관리를 지속적으로 수행하지 않아 시설 내 막힘 현상 등의 문제가 발생한다. 따라서 본 연구는 효율적인 물수지 및 오염물질 저감을 위해 레인가든 기술의 구성 요소 배치의 개발 및 평가를 위하여 수행하였으며, 서로 다른 2개의 하이브리드 레인가든 시스템 구축을 통하여 시스템의 최적화된 설계 및 구성요소의 배열을 도출하였다. 분석 결과, 시스템의 구성요소를 직렬로 배열 시 저감량은 유출량의 경우 96%, 오염물질 중 입자상 물질은 99%, 유기물질은 93% 및 중금속은 95%로 나타났다. 반면 시스템이 병렬로 배열 될 시, 유출량은 65% 저감되었으며, 평균 오염물질 저감효율은 TSS는 94%, 영양물질은 80% 및 중금속은 85%으로 평가되었다. 또한, 시스템의 구성요소가 비점오염물질 저감에는 침전, 침투도랑 및 식재부의 순서가 중요한 영향인자로 나타났다. 향후 레인가든 시스템 개발 시 최적화 설계 인자로 활용 가능할 것으로 기대된다.

• 한국구조물진단유지관리공학회 논문집
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• 제27권6호
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• pp.22-29
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• 2023

재료 및 부재의 내진성능평가 실험 시 재하속도와 수직하중은 성능에 중대한 영향을 미칠 수 있다. 반복 가력 및 하이브리드 실험 시 재하속도는 입력 변위와 출력 변위 사이의 시간 지연현상으로 인해 고속으로 제어하기 어려우며 횡방향 변위에 의해 수직하중을 일정하게 유지하는 것이 어려워 일정한 수직하중이 유지되는 고속 및 실시간 실험은 거의 이루어지지 않았다. 본 연구에서는 면진받침의 속도 의존성과 수직하중의 영향을 조사하기 위해 저속 및 고속 반복 가력 실험과 실시간 하이브리드 실험을 수행하였다. 실험에서 수평 변위와 수직 하중의 실시간 제어를 위해 Adaptive Time Series(ATS) 보정 방법과 State estimator가 포함된 FLB System을 구축하였다. 고속 또는 실시간으로 재하되는 수평 변위 제어 속도와 상부구조물에 의한 수직하중은 면진받침의 강도 및 지진 시 거동에 상당한 영향을 미칠 수 있음을 확인하였으며 내진성능평가를 위한 실험 시 실제와 유사하도록 구현되어야함을 알 수 있었다. 본 연구는 내진성능평가를 위해 구축하고 사용된 시스템의 우수한 성능을 보여주며 정확하고 효율적인 내진성능평가가 가능하도록 하였다.

• 인터넷정보학회논문지
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• 제12권4호
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• pp.157-172
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• 2011

최근 분산 OLAP은 분산 환경에 적용하기 위하여 DHT기반의 P2P OLAP과 그리드 OLAP연구가 활발하게 진행되고 있다. 그러나 클라우드 컴퓨팅 환경에 적용하기 위하여 P2P OLAP은 structured P2P 특성 때문에 다차원 범위 질의에 문제점이 있고, Grid OLAP은 인접성 및 시계열 고려가 없기 때문에 쿼리 자체의 서브 �V 조회 알고리즘 연구에 치중되어 있다. 따라서 본 논문은 클라우드 컴퓨팅에 적합한 환경 제공을 위해 사용자의 조회 결과가 시계열적 특성으로 여러 사용자에 의해 재사용이 가능하고, 서버상의 휘발성 조회 큐브가 사용자 로컬 메모리에서 직접 분석 질의 시 효율이 좋다는 것에 초점을 두어 중앙관리 P2P방식을 제안하였다. 또한 빠른 질의 결과 및 다차원 범위질의를 위한 다단계 Hybrid P2P방식에 인덱스 부하 분산 및 성능 향상을 위한 클라우드 시스템을 접목하여 Cloud P2P OLAP을 제안하였다. 이를 위한 인덱스 구조로는 큐브 위상관계 트리와 인접성 2차원 Quadtree에, 시계열 Interval-트리를 접목하였으며, 이는 조회나 갱신 시에 일반 OLAP에 비해 큰 효율성을 보였다.