• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 하계종합학술대회 논문집(1)
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• pp.281-284
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• 2004

This paper presents the design and implementation of a QoS based enhanced collaboration system in MDO. This is an efficient distributed communication tool between designers. It supports text communication, audio/video communication, file transfer and XML data sending/receiving. Specially, this system supports a dynamic QoS self-adaptation by using the improved direct adjustment algorithm (DAA+). The original direct adjustment algorithm adjusts the transmission rate according to the congestion level of the network, based on the end to end real time transport protocol (RTP), and controls the transmission rate by using the information of loss ratio in real time transport control protocol (RTCP). But the direct adjustment algorithm does not consider when the RTCP packets are lost. We suggest an improved direct adjustment algorithm to solve this problem. We apply our improved direct adjustment algorithm to our of QoS (Quality of Service) [1] based collaboration system and show the improved performance of transmission rate and loss ratio.

• ETRI Journal
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• 제46권3호
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• pp.421-431
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• 2024

In this study, a direct position tracking method for non-circular (NC) signals using distributed passive arrays is proposed. First, we calculate the initial positions of sources using a direct position determination (DPD) approach; next, we transform the tracking into a compensation problem. The offsets of the adjacent time positions are calculated using a first-order Taylor expansion. The fusion calculation of the noise subspace is performed according to the NC characteristics. Because the proposed method uses the signal information from the previous iteration, it can realize automatic data associations. Compared with traditional DPD and two-step localization methods, our novel process has lower computational complexity and provides higher accuracy. Moreover, its performance is better than that of the traditional tracking methods. Numerous simulation results support the superiority of our proposed method.

• 문화기술의 융합
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• 제4권3호
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• pp.241-246
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• 2018

영상 기기의 기계적인 문제로 인해 실험 데이터에 발생한 잡음으로 인한 인식 오류를 최소화하기 위해서 영상복원 과정을 거친다. 영상 복원 방법은 실험 데이터를 구성하는 각각의 픽셀에 대해 Direct Neighbor와 Indirect Neighbor의 개수와 위치를 조사해서 잡음을 해결한다. 결과적으로, 영상 복원 과정을 통해 실험 데이터에 발생한 잡음을 최대한 제거하고, 영역 단위로 학습 데이터와 실험 데이터의 차이를 계산해서 잡음에 의한 인식 오류 가능성을 낮춤으로써 만족할만한 인식 결과를 얻을 수 있다.

• 한국초등과학교육학회지:초등과학교육
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• 제36권3호
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• pp.208-218
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• 2017

This study was to investigate factors and disclose causal model of the scientific literacy competency about the motivation for science and the scientific literacy competency. The 3 grade university students and the 1 grade university students as pre-service elementary teachers were participated to questionnaire investigation. The data were analyzed by the factor analysis method and the structural equation model method, and the following results were obtained. First, the 3 grade university students and the 1 grade university students perceived the science interest factors and science usefulness factors as the motivation for science, and also revealed the scientific problem recognition factor and the scientific evidence use factor as the scientific literacy competency. Second, the science interest factor had a greater effect on the scientific problem recognition factor than the scientific evidence use factor in both the 3 grade and 1 grade university students. In the path from the science usefulness factor to the scientific problem recognition factor, the science usefulness factor of the 3 grade university students had a greater influence on the direct route to the scientific problem recognition factor than that of the 1 grade university students. In the path from the science usefulness factor to the scientific evidence use factor, the science usefulness factor of the 1 grade university students influenced more on the direct route to the scientific evidence use factor than that of the 3 grade university students.

• 한국항공우주학회지
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• 제38권7호
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• pp.684-692
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• 2010

본 논문에서는 지구-달 천이를 위한 최적 궤도 설계에 관한 연구를 수행하였다. 지구와 달의 인력을 동시에 고려한 평면상 제한 3체 궤도 운동 모델을 바탕으로 지구 출발시에는 순간 추력을, 지구-달 천이 과정 및 달 임무궤도 투입시에는 연속 추력을 사용하는 혼합형 궤도전이 방법을 제시하였다. 최적화 풀이 방법으로서 Direct Transcription 및 Collocation을 이용한 비선형 프로그래밍 기법을 적용하였으며, 지구 출발 및 달 임무궤도 투입 궤적의 형상은 순간 추력의 연속 추력에 대한 상대 가중치 및 비행시간에 의하여 매우 달라질 수 있음을 파악하였다.

• Journal of applied mathematics & informatics
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• 제28권3_4호
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• pp.837-844
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• 2010

In this paper, a class of initial value problem of hyperbolic equations for fourth order with multiple characteristics is considered and can be solved analytically by variable transforms. Also, similar to Goursat's problem we present a direct integration technique for finding a new solutions of an inhomogeneous hyperbolic equation of fourth order such that the attached conditions are given on its multiple characteristics.

• 전자공학회논문지B
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• 제29B권1호
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• pp.26-33
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• 1992

This paper presents lattice structure of bilinear filter and the conversion equations from lattice parameters to direct-form parameters. Billnear models are attractive for adaptive filtering applications because they can approximate a large class of nonlinear systems adequately, and usually with considerable parsimony in the number of coefficients required. The lattice filter formulation transforms the nonlinear filtering problem into an equivalent multichannel linear filtering problem and then uses multichannel lattice filtering algorithms to solve the nonlinear filtering problem. The lattice filters perform a Gram-Schmidt orthogonalization of the input data and have very good easily extended to more general nonlinear output feedback structures.

• 한국인터넷방송통신학회논문지
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• 제14권3호
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• pp.13-19
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• 2014

노트북, 태블릿, 스마트폰 등 모바일 기기들의 성능 향상으로 인하여 임의의 장소에서의 그룹 회의를 진행하는 사람들이 많아지고 있다. 그러나 회의 참석자들이 근거리에 위치하고 있음에도 불구하고 참석자들 간의 데이터의 교환은 셀룰러 망을 이용하여 이루어지고 있다. 이는 불필요하게 셀룰러망에 부하를 가중시키는 원인이 되어 데이터의 송수신 지연을 발생시키고 원활한 회의의 운영 및 일반 모빌 통신 사업자의 통화 품질을 저하시키는 원인이 된다. 이러한 문제를 해결하기 위하여 본 논문에서는 Wi-Fi Direct 기술을 이용하여 근거리 통신기기들 간의 셀룰러 망을 사용하지 않고 회의 참석자들간 직접 통신을 수행할 수 있는 안드로이드 어플리케이션을 개발하고 그 방법에 대하여 소개한다.

• 전기학회논문지
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• 제61권8호
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• pp.1199-1203
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• 2012

H.264 adopted many compression tools to increase image data compression efficiency such as B frame bi-directional predictions, the direct mode coding and so on. Despite its high compression efficiency, H.264 can suffer from its long coding time due to the complicated tools of H.264. To realize a high performance H.264, several fast algorithms were proposed. One of them is adaptive fast direct mode decision algorithm using mode and Lagrangian cost prediction for B frame in H.264/AVC (MLP) algorithm which can determine the direct coding mode for macroblocks without a complex mode decision process. However, in this algorithm, macroblocks not satisfying the conditions of the MLP algorithm are required to process the complex mode decision calculation, yet suffering a long coding time. To overcome the problem, this paper proposes a fast direct mode prediction algorithm. Simulation results show that the proposed algorithm can determine the direct mode coding without a complex mode decision process for 42% more macroblocks and, this algorithm can reduce coding time by up to 23%, compared with Jin's algorithm. This enables to encode B frames fast with a less quality degradation.

• Steel and Composite Structures
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• 제29권2호
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• pp.175-186
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• 2018

The plastic hinge method and the plastic zone method are extensively adopted in displacement-based elements and force-based elements respectively for second-order inelastic analysis. The former enhances the computational efficiency with relatively less accurate results while the latter precisely predicts the structural behavior but generally requires more computer time. The displacement-based elements receive criticism mainly on plasticity dominated problems not only in accuracy but also in longer computer time to redistribute the forces due to formation of plastic hinges. The multi-element-per-member model relieves this problem to some extent but will induce a new problem in modeling of member initial imperfections required in design codes for direct analysis. On the contrary, a force-based element with several integration points is sufficient for material yielding. However, use of more integration points or elements associated with fiber section reduces computational efficiency. In this paper, a new force-based element equipped with stress-resultant plasticity model with minimal computational cost is proposed for second-order inelastic analysis. This element is able to take the member initial bowing into account such that one-element-per-member model is adequate and complied with the codified requirements of direct analysis. This innovative solution is new and practical for routine design. Finally, several examples demonstrate the validity and accuracy of the proposed method.