• International Journal of Contents
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• 제5권1호
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• pp.21-26
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• 2009

Peer to Peer (P2P) utilizes the resources of an offered service without the need for a central server or preexistent server-client, making it a desirable network environment for data exchange based on direct connection between peers. Proposed by Sun Microsystems. JXTA(Juxtapose) is a typical P2P system and distributed computing model that does not require central service resources and is flexible to deal with various network configuration changes. Meanwhile. Mobile Ad-hoc NETwork(MANET) is a typical wireless network configured with mobile nodes and without an infrastructure. where a network is established by direct connection or through other peers in the propagation area. Thus, MANET maintains the latest path information by establishing paths and changing path information for communication between peers in a highly mobile wireless network. Accordingly. this article proposes the JXTAMANET method for wireless networks to enable JXTA to be applied to MANET. NS2 is used to evaluate the performance and the proposed architecture is shown to produce better results than a conventional flooding method.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.14-19
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• 1993

In this paper, we proposed an indirect learning and direct adaptive control schemes using neural networks, i.e., composite adaptive neural control, for a class of continuous nonlinear systems. With the indirect learning method, the neural network learns the nonlinear basis of the system inverse dynamics by a modified backpropagation learning rule. The basis spans the local vector space of inverse dynamics with the direct adaptation method when the indirect learning result is within a prescribed error tolerance, as such this method is closely related to the adaptive control methods. Also hash addressing technique, similar to the CMAC functional architecture, is introduced for partitioning network hidden nodes according to the system states, so global neuro control properties can be organized by the local ones. For uniform stability, the sliding mode control is introduced when the neural network has not sufficiently learned the system dynamics. With proper assumptions on the controlled system, global stability and tracking error convergence proof can be given. The performance of the proposed control scheme is demonstrated with the simulation results of a nonlinear system.

• 경영과학
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• 제26권3호
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• pp.169-184
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• 2009

Recently, mobile telecommunication businesses contend with each other to expand their customer base by using aggressive marketing strategies. In order to determine if there strategies are effective, customer's switching behavior needs to be studied. This study identifies and analyzes direct, indirect factors that may customer switching behavior : attractiveness of alternatives, network externality, and switching cost. Results reveals that attractiveness of alternatives, network externalities have a direct impact on customer switching behavior. These two factors also have moderating effects on customer switching behavior but the switching cost does not In short, network externalities and alternatives strategically determine the success of 3.5G service. In this regard, mobile business should improve their own attractiveness of alternatives by developing specialized service in 3.5G service.

• International Journal of Control, Automation, and Systems
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• 제3권4호
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• pp.552-563
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• 2005

In this paper, we propose a wavelet based fuzzy neural network (WFNN) based direct adaptive control scheme for the solution of the tracking problem of mobile robots. To design a controller, we present a WFNN structure that merges the advantages of the neural network, fuzzy model and wavelet transform. The basic idea of our WFNN structure is to realize the process of fuzzy reasoning of the wavelet fuzzy system by the structure of a neural network and to make the parameters of fuzzy reasoning be expressed by the connection weights of a neural network. In our control system, the control signals are directly obtained to minimize the difference between the reference track and the pose of a mobile robot via the gradient descent (GD) method. In addition, an approach that uses adaptive learning rates for training of the WFNN controller is driven via a Lyapunov stability analysis to guarantee fast convergence, that is, learning rates are adaptively determined to rapidly minimize the state errors of a mobile robot. Finally, to evaluate the performance of the proposed direct adaptive control system using the WFNN controller, we compare the control results of the WFNN controller with those of the FNN, the WNN and the WFM controllers.

• 지식경영연구
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• 제17권4호
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• pp.77-104
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• 2016

The effective management of R&D employees is critical for a small or medium sized firm's sustainable growth. R&D employees have professional skills and choose expertise-oriented or management-oriented careers in the process of organizational socialization. This study synthetically verifies the direct and indirect effects of R&D employees' social network and self-esteem on their career orientation by organizational commitment based on social network theory and social recognition theory. The research model has been analyzed through structural equation modeling using survey responses from 220 R&D employees at small- and medium-sized firms in Korea. The analysis results show that internal network activities have direct and indirect impacts on organizational commitment and career orientation, but external network activities do not have significant effects on self-esteem, organizational commitment, or career orientation. There is no consensus in prior studies on whether expert orientation and management orientation are distinct concepts. In this study, these two types of orientation are verified as distinct concepts. It is also found that R&D employees' internal network activities are significant factors for a company's growth. A company should implement an educational system of roles and duties using which individuals can pursue career progression. In addition, it is necessary to provide career development programs such as job rotation, mentoring, and career counseling.

• International Journal of Advanced Culture Technology
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• 제5권2호
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• pp.19-25
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• 2017

The research is to identify social networks of problems that have an influence on the quality of ageing people's lives by using social network analysis, based on the premise that there are differences in networks of ageing problems in urban and rural areas. From analyzing network of ageing people's problems using NodeXL, vertices in the networks of both urban and rural areas are well-connected. For urban areas, financial poverty is the core problem related to the quality of life. It has direct connections with illness and health, family responsibility, housing, role loss in community, and employment, which have positive or negative interactions with the quality of older people's lives. For rural areas, on the other hand, role loss in community is the major problem. It has direct connections with the elderly abuse, financial poverty, leisure activity, divorce, isolation and loneliness from society, education, and suicide. As a result, the research shows that the problems of ageing people have strong linkages and interactive effects with a structure of network, and the networks are different depending on types of places for living.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.453-456
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• 1996

In this paper, the direct adaptive control using neural networks is presented for the control of chaotic nonlinear systems. The direct adaptive control method has an advantage that the additional system identification procedure is not necessary. In order to evaluate the performance of our controller design method, two direct adaptive control methods are applied to a Duffing's equation and a Lorenz equation which are continuous-time chaotic systems. Our simulation results show the effectiveness of the controllers.

• 전자공학회논문지SC
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• 제44권6호
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• pp.1-10
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• 2007

본 논문에서는 비선형 다변수 시스템에 적응할 수 있는 신경회로망을 이용한 PID 구조를 갖는 직접 다변수 자기동조 제어기를 제안한다. 제어기에 적용되는 플랜트는 잡음, 시간지연과 상호결합항이 존재하며 파라미터가 변하는 비선형 다변수 시스템이다. 비선형 다변수 시스템은 선형부분과 비선형부분으로 분리한 형태로 구성되며, 선형제어기는 외부환경 변화에 적응할 수 있는 PID 제어기 특성을 가진 자기동조 PID 제어기 이다. 선형부분의 제어기 파라미터는 순환최소자승법으로 직접 추정하고 비선형 부분의 파라미터는 신경회로망으로 추정한다. 그리고 각 부분에서 추정한 파라미터를 합한 후 비선형 다변수 일반화 자기동조 제어기의 제어법칙에 적용한다. 제어 알고리듬의 타당성을 확인하기 위해 시간 지연이 있고 일정한 시간이 경과한 후 시스템의 파라미터가 변하는 비선형 다변수 시스템에 대해 컴퓨터 시뮬레이션을 하였다. 또한 기존의 신경회로망을 이용한 직접 다변수 적응 제어기에 비해 효과적이다.

• 전자공학회논문지C
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• 제35C권6호
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• pp.99-108
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• 1998

본 논문에서는 비선형 시스템의 직접제어방식을 위한 다층 신경회로망을 제안하였다. 제안한 방식은 신경회로망이 플랜트의 역 모델을 학습하는 방식으로 플랜트의 사전지식을 시스템의 입출력 정보를 이용하여 추정하고, 플랜트의 역 모델을 선형부분과 비선형 부분의 직렬연결로 구성하고 선형부분과 비선형부분의 모델을 신경회로망을 이용하여 구성한 직접제어방식이다. 제안한 제어기의 선형부분은 선형 시스템의 시스템동정을 위해 이용되었던 반복최소자승법을 이용하여 구하여진 플랜트의 선형입력으로 학습을 수행하고, 비선형부분은 기준 궤적과 실제 출력의 오차를 이용해 학습을 수행한다. 단일 관절 매니플레이터를 이용하여 추종제어에 대한 시뮬레이션과 실험을 하여 기존의 다층신경회로망을 이용한 직접제어방식과 제어성능을 비교 검토한 결과 신경회로망 구성의 간단함과 정밀성 등의 우수함을 확인하였다.

• 한국경제지리학회지
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• 제26권3호
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• pp.256-273
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• 2023

본 연구는 2009년부터 2021년까지 IMF의 CDIS(Coordinated Direct Investment Survey) 자료를 이용하고 사회 네트워크 분석 방법을 활용하여 글로벌 해외직접투자 네트워크의 변화를 분석하였다. 주요 분석 결과는 다음과 같다. 첫째, 코로나19 팬데믹 이후 국가 간 FDI 관계의 긴밀성이 약화되고, 상호 관계 활동성이 축소되었다. 둘째, 글로벌 해외직접투자 네트워크에서 가장 영향력이 있는 국가는 미국, 네덜란드, 영국 등인 것으로 나타났다. 셋째, 불안정한 글로벌 경제 환경 속에서 중국의 연결 중심성이 크게 변화하였다. 넷째, 해외직접투자 네트워크의 클러스터와 지역 간에는 유의미하게 연관성이 있는 것으로 나타났으며, 긴밀하게 연결되어 있는 개별 국가들의 투자 파트너들은 시간의 흐름에 따라 차별적인 특징을 보인다.