• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권9호
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• pp.4603-4624
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• 2016

In this paper, a new reversible watermarking algorithm with adaptive embedding threshold matrix is proposed. Firstly, to avoid the overflow and underflow, two flexible thresholds, TL and TR, are applied to preprocess the image histogram with least histogram shift cost. Secondly, for achieving an optimal or near optimal tradeoff between the embedding capacity and imperceptibility, the embedding threshold matrix, composed of the embedding thresholds of all blocks, is determined adaptively by the combination between the composite chaos and the average energy of Integer Wavelet Transform (IWT) block. As a non-liner system with good randomness, the composite chaos is suitable to search the optimal embedding thresholds. Meanwhile, the average energy of IWT block is calculated to adjust the block embedding capacity, and more data are embedded into those IWT blocks with larger average energy. The experimental results demonstrate that compared with the state-of-the-art reversible watermarking schemes, the proposed scheme has better performance for the tradeoff between the embedding capacity and imperceptibility.

• International Journal of Contents
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• 제2권2호
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• pp.10-16
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• 2006

In this paper, we propose a predictive resource metric region (RMR) based radio resource metric estimation (RRME) mechanism, which utilizes a resource metric mapping function (RMMF), both of which permit efficient inter-working between the physical layer and higher layers for envisaging multimedia service applications over a CDMA communication system platform. The RMR can provide the acceptable resource region where QoS and acceptable link quality can be guaranteed with an achievable resource margin to be utilized in terms of capacity margin, the degree of confidence (DCL) of user, second-order statistics of Eb/Io. With predicted capacity margin and variance, DCL can deliver decision parameters with which an adaptive QoS based admission control can perform well taking capacity and resource availability into account in a dynamic and predictive manner. Combined with advanced techniques such as adaptive modulation or rate control and power control, the proposed mechanism can adjust the conventional stringent link quality information efficiently, and deliver accurate information of the resource availability. Thus, these can guarantee the maximization of resource utilization of multimedia service applications.

• Computers and Concrete
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• 제25권1호
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• pp.1-14
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• 2020

This study presents applications of the multivariate adaptive regression splines (MARS) method for predicting the ultimate loading carrying capacity (N_u) of rectangular concrete-filled steel tubular (CFST) columns subjected to eccentric loading. A database containing 141 experimental data was collected from available literature to develop the MARS model with a total of seven variables that covered various geometrical and material properties including the width of rectangular steel tube (B), the depth of rectangular steel tube (H), the wall thickness of steel tube (t), the length of column (L), cylinder compressive strength of concrete (f'_c), yield strength of steel (f_y), and the load eccentricity (e). The proposed model is a combination of the MARS algorithm and the grid search cross-validation technique (abbreviated here as GS-MARS) in order to determine MARS' parameters. A new explicit formulation was derived from MARS for the mentioned input variables. The GS-MARS estimation accuracy was compared with four available mathematical methods presented in the current design codes, including AISC, ACI-318, AS, and Eurocode 4. The results in terms of criteria indices indicated that the MARS model was much better than the available formulae.

• 대한전자공학회논문지TC
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• 제46권2호
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• pp.11-17
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• 2009

본 논문은 공평성 제한(fairness constraint)이 존재하는 재생(regenerative) 직교 주파수 분할 다중 접속 (OFDMA: Orthogonal Frequency Division Multiple Access) 중계 네트워크(relay network)에서 새로운 적응 중계기 선택(adaptive relay selection) 기법을 제안한다. 제안된 기법에서 K 개의 중계기 중 시스템 용량(system capacity)을 최대화하는 M 개의 중계기를 선택한다. 선택된 중계기 사이에서는 공평성 제한을 만족하면서 시스템 성능 열화(system performance degradation)를 최소화하도록 부반송파를 재할당(subcarrier reallocation)한다. 그런 다음 보다 향상된 성능을 얻기 위해 워터필링(water-filling) 방법을 통한 적응적 전력할당이 이루어진다. 시스템 용량과 공평성 사이의 트레이드오프(trade-off) 관계를 이용하여 제안된 기법의 개선 방법 또한 연구되었다.

• Steel and Composite Structures
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• 제48권5호
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• pp.531-545
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• 2023

Composite dowels are implemented as a powerful alternative to headed studs for the efficient combination of Ultra High-Performance Concrete (UHPC) with high-strength steel in novel composite structures. They are required to provide sufficient shear resistance and ensure the transmission of tensile forces in the composite connection in order to prevent lifting of the concrete slab. In this paper, the load bearing capacity of puzzle-shaped and clothoidal-shaped dowels encased in UHPC specimen were investigated based on validated experimental test data. Considering the influence of the embedment depth and the spacing width of shear dowels, the characteristics of UHPC square plate on the load bearing capacity of composite structure, 240 numeric models have been constructed and analyzed. Three artificial intelligence approaches have been implemented to learn the discipline from collected experimental data and then make prediction, which includes Artificial Neural Network-Particle Swarm Optimization (ANN-PSO), Adaptive Neuro-Fuzzy Inference System (ANFIS) and an Extreme Learning Machine (ELM). Among the factors, the embedment depth of composite dowel is proved to be the most influential parameter on the load bearing capacity. Furthermore, the results of the prediction models reveal that ELM is capable to achieve more accurate prediction.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1998년도 학술발표대회 논문집 제17권 2호
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• pp.201-204
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• 1998

This paper study on blind adaptive interference suppression algorithm without training sequence to solve Near-Far problem due to multi access interference. And the performance of each algorithm in the presence of the multipath fading channels over DS-CDMA is evaluated. Simulation results showed that Modified LMS-CMA algorithm has a higher capacity than MOE in SIR/SNR.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.1000-1005
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• 1993

In this paper asymptotic formulate for performance characteristics throughput, delay) of large scale token-passing networks with priorities and limited service are given. In particular, adaptive control procedures for obtaining optimal buffer capacity with respect to each priority and optimal limited service are shown. All results obtained are supported by simulations.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.143-144
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• 2006

This paper presents an adaptive OFDM system with multistep predictor to effectively compensate multiple feedback delays. The proposed scheme adaptively changes the modulation order per subcarrier based on the predicted CSI to improve data capacity and system performance.

• 한국초지조사료학회지
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• 제41권3호
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• pp.189-197
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• 2021

Climate change effects are particularly apparent in many cool-season grasslands in South Korea. Moreover, the probability of climate extremes has intensified and is expected to increase further. In this study, we performed climate change vulnerability assessments in cool-season grasslands based on the analytic hierarchy process method to contribute toward effective decision-making to help reduce grassland damage caused by climate change and extreme weather conditions. In the analytic hierarchy process analysis, vulnerability was found to be influenced in the order of climate exposure (0.575), adaptive capacity (0.283), and sensitivity (0.141). The climate exposure rating value was low in Jeju-do Province and high in Daegu (0.36-0.39) and Incheon (0.33-0.5). The adaptive capacity index showed that grassland compatibility (0.616) is more important than other indicators. The adaptation index of Jeollanam-do Province was higher than that of other regions and relatively low in Gangwon-do Province. In terms of sensitivity, grassland area and unused grassland area were found to affect sensitivity the most with index values of 0.487 and 0.513, respectively. The grassland area rating value was low in Jeju-do and Gangwon-do Province, which had large grassland areas. In terms of vulnerability, that of Jeju-do Province was lower and of Gyeongsangbuk-do Province higher than of other regions. These results suggest that integrating the three aspects of vulnerability (climate exposure, sensitivity, and adaptive capacity) may offer comprehensive and spatially explicit adaptation plans to reduce the impacts of climate change on the cool-season grasslands of South Korea.

• 환경정책연구
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• 제9권2호
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• pp.185-205
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• 2010

기후변화 적응정책을 수립하기 위해서는 지역에 기초한 취약성 평가가 선행되어야 한다. 지금까지 기후변화 취약성에 관한 연구는 주로 국가별 취약성의 비교 및 분석에 집중되었기 때문에 지역별 기후변화 취약성을 평가하고 비교하기 위한 방법론은 아직 국내외적으로 확립되어 있지 않은 실정이다. 본 논문의 목적은 기후변화 취약성의 개념적 틀을 확립하고 이를 지역적으로 평가하기 위한 일반적인 방법론을 개발하는 데에 있다. 기후변화 취약성을 IPCC (1996) 개념틀에 따라 기후노출과 시스템의 민감도, 그리고 시스템이 대응할 수 있는 적응능력의 함수로 보았다. 여러 기후노출 중 본 논문에서는 기후변화에 의해 일차적으로 피해를 입을 수 있는 해수면 상승을 상정하였다. 방법론 적용 대상도시로는 국내 해안에 위치한 목포시를 선정하였다. 이는 목포시가 포함된 우리나라 서남해 지역의 평균 해수면이 전반적으로 증가추세를 보이고 있고, 특히 목포시가 가장 큰 증가폭을 보였으며, 하구언과 방조제 건설 이후 이상고조 발생 가능성이 현격하게 높아진 해역이기 때문이다. 해수면 상승에 따른 민감도는 GIS 기술을 활용하여 해수면이 1~5m 상승할 경우의 침수 시뮬레이션 결과를 기반으로 계산하였다. 행정구역(동)별 침수면적 비율에 기초하여 여기에 인구밀도 및 65세 이상 인구비율에 대한 통계자료를 고려하였고, 표준화 과정(dimension index)을 거쳐 민감도 지수를 도출하였다. 적응능력으로는 하드웨어적인 측면과 소프트웨어적인 측면을 고려하였는데, 하드웨어적 적응능력으로는 방파제와 방조제의 존재여부 및 높이를 고려하였고, 소프트웨어적 적응능력은 목포시 75명 공무원을 대상으로 설문조사를 수행하여 평가하였다. 설문조사 문항에는 기후변화에 대한 인식, 거버넌스, 경제적 능력 및 정책 기반이 포함되었는데, 0~1 사이의 정량적인 값을 설문문항 응답수준에 따라 부여하였다. 해수면 상승에 따른 취약성은 민감도에서 적응능력을 뺀 나머지로 표현하였다. 목포시의 해수면 상승에 따른 취약성은 총 20개 동 중 7개 동이 높은 것으로 나타났다. 본 연구결과를 이용하여 기후변화 적응대책 수립의 방향성을 제시하기 위해서는 첫째, 과거 침수피해와의 상관관계 다이어그램을 통하여 적응정책 시행의 우선순위 지역을 선정하고, 둘째, 우선순위 지역에 대한 단기, 중기, 장기 개발계획 및 프로젝트를 검토한 후 이에 합당한 적응조치를 제언할 수 있을 것으로 사료된다.