• 전기학회논문지
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• 제62권10호
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• pp.1487-1493
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• 2013

A new simple control method for active power filter, which can realize the complete compensation of harmonics is proposed. In the proposed scheme, a model-based digital current control strategy is presented. The proposed control system is designed and implemented in a form referred to as internal model control structure. This method provides a convenient way for parameterizing the controller in term of the nominal system model, including time-delays. As a result, the resulting controller parameters are directly set based on the power circuit parameters, which make tuning of the controllers straightforward task. In the proposed control algorithm, overshoots and oscillations due to the computation time delay is prevented by explicit incorporating of the delay in the controller transfer function. In addition, a new compensating current reference generator employing resonance model implemented by a DSP(Digital Signal Processor) is introduced. Resonance model has an infinite gain at resonant frequency, and it exhibits a band-pass filter. Consequently, the difference between the instantaneous load current and the output of this model is the current reference signal for the harmonic compensation.

• Smart Structures and Systems
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• 제3권3호
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• pp.373-384
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• 2007

For structural health monitoring (SHM) of civil infrastructures, displacement is a good descriptor of the structural behavior under all the potential disturbances. However, it is not easy to measure displacement of civil infrastructures, since the conventional sensors need a reference point, and inaccessibility to the reference point is sometimes caused by the geographic conditions, such as a highway or river under a bridge, which makes installation of measuring devices time-consuming and costly, if not impossible. To resolve this issue, a visionbased real-time displacement measurement system using digital image processing techniques is developed. The effectiveness of the proposed system was verified by comparing the load carrying capacities of a steel-plate girder bridge obtained from the conventional sensor and the present system. Further, to simultaneously measure multiple points, a synchronized vision-based system is developed using master/slave system with wireless data communication. For the purpose of verification, the measured displacement by a synchronized vision-based system was compared with the data measured by conventional contact-type sensors, linear variable differential transformers (LVDT) from a laboratory test.

• JSTS:Journal of Semiconductor Technology and Science
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• 제8권4호
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• pp.318-325
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• 2008

A 1.2 V 7-bit 1 GS/s CMOS flash ADC with an interpolation factor of 4 is implemented by using a $0.13\;{\mu}m$ CMOS process. A digital calibration of DC reference voltage is proposed for the $1^{st}$ preamp array to compensate for the input offset voltage of differrential amplifiers without disturbing the high-speed signal path. A 3-stage cascaded voting process is used in the digital encoder block to eliminate the conescutive bubbles up to seven completely, if the $2^{nd}$ preamp output is assumed to have a single bubble at most. ENOB and the power consumption were measured to be 5.88 bits and 212 mW with a 195 MHz $400\;mV_{p-p}$ sine wave input.

• 한국문헌정보학회지
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• 제37권1호
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• pp.247-268
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• 2003

최근 인터넷의 빠른 성장과 전자출판으로 인해 정보에 접근하는 방법이 상당히 변화하고 있다. 이와 함께, 디지털 문서에서 적합한 정보를 결정하고 효율적으로 추출할 필요가 있을 것이다. 이 연구는 디지털문서에서 여러 가지 정보를 추출하기 위해 템플릿 마이닝이 사용될 수 있음을 제시하고, 참조연결시스템과 관련된 연구를 고찰하였다. 또한 실제적으로 논문 샘플을 분석한 결과를 이용하여 참조정보를 위한 템플릿을 구축하고, 이 템플릿을 이용하여 수작업으로 논문 샘플을 테스트한 결과, 템플릿 마이닝의 이용은 인용 데이터베이스를 자동으로 만들 수 있는 가능성을 보여주었다.

• 디지털산업정보학회논문지
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• 제16권1호
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• pp.79-92
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• 2020

As the number of systems increases and the network size increases, automated attack prediction systems are urgently needed to respond to cyber attacks. In this study, we developed four types of information gathering sensors for collecting asset and vulnerability information, and developed technology to automatically generate attack graphs and predict attack targets. To improve performance, the attack graph generation method is divided into the reachability calculation process and the vulnerability assignment process. It always keeps up to date by starting calculations whenever asset and vulnerability information changes. In order to improve the accuracy of the attack target prediction, the degree of asset risk and the degree of asset reference are reflected. We refer to CVSS(Common Vulnerability Scoring System) for asset risk, and Google's PageRank algorithm for asset reference. The results of attack target prediction is displayed on the web screen and CyCOP(Cyber Common Operation Picture) to help both analysts and decision makers.

• 한국통신학회논문지
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• 제21권3호
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• pp.612-621
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• 1996

In this paper, we propose the low sidelobe digital FIR doppler filter bank synthesis algorithm through the Gradient Descent method and it can be practially appliable to coherent pulse doppler radar signal processing. This algorithm shows the appropriate calculation of tap coefficients or zeros for FIR transversal fiter which has been employed in radar signal processor. The span of the filters in the filter bank be selected at the desired position the designer want to locate, and the lower sidelobe level that has equal ripple property is achieved than one for which the conventional weithtedwindow is used. Especially, when we implemented filter zeros as design parameters it is possible to make null filter gain at zero frequency intensionally that would be very efficient for the eliminatio of ground clutter. For the example of 10 tap filter synthesis, when filter coefficients or zeros are selected as design parameters the corresponding sidelobelevel is reducedto -70db or -100db respectively and it has good convergent characteristics to the desired sidelobe reference value. The accuracy ofapproach to the reference value and the speed of convergence that show the performance measure of this algorithm are tuned out with some superiority and the fact that the bandwidth of filter appears small with respect to one which is made by conventional weighted window method is convinced. Since the filter which is synthesized by this algorithm can remove the clutter without loss of target signal it strongly contributes performance improvement with which detection capability would be concerned.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 F
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• pp.2018-2020
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• 1998

In design of a digital current controller for a 3$\phi$ voltage-source (VS) PWM converter, its conventional model, i.e., stationary or synchronous reference frame model, is used in obtaining its discretized version. It introduces, however, inherent errors since the following practical problems are not taken into consideration: the characteristics of the space vector-based pulsewidth modulation (SVPWM) and the time delays in the process of sampling and computation. In this paper, the new hybrid reference frame model of the 3$\phi$ VS PWM converter is proposed considering these problems. In addition, the direct digital current controller based on this model is designed without any prediction or extrapolation algorithm to compensate the time delay. So the control algorithm is made very simple. The validity of the proposed algorithm is proved by the computer simulation results.

• 디지털산업정보학회논문지
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• 제9권1호
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• pp.9-23
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• 2013

In recent days, there are many researches of wireless LAN services as the communication environment of wireless LAN are so improved that a lot of services are available in wireless environments. The frequency of the wireless LAN is a general resource that can be used to everyone without any permission. Many technologies using this ISM (Industry Science Medical) frequency band are developed fast and widely. But, as many devices use the same frequency band at th same time, the service quality is degraded and the speed of the service rate id degraded by the result of the interference. For overcome this problem, we must provide the new technology of the mobile devices and a new cell design scheme for obtaining maximum throughput that considering the wireless environments effectively. In this paper, we explain the main technology at the IEEE 802.11n environments and proposes the optimal cell design and reference model for gaining maximum performance to many mobile devices at the same time by investigating real environment testing results.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2019년도 춘계학술대회
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• pp.214-216
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• 2019

최근 다양한 분야에서 디지털 장비의 사용이 증가함에 따라 영상 및 신호처리의 중요성이 높아지고 있다. 하지만 디지털 신호는 송수신 과정에서 많은 종류의 잡음이 발생하며, 이러한 잡음은 시스템의 최종 출력에 큰 영향을 미친다. 본 논문은 임펄스 잡음과 AWGN이 혼합된 잡음 환경에서 화소 유사성에 따른 잡음 제거를 통해 효과적으로 영상을 복원하는 알고리즘을 제안하였다. 제안한 알고리즘은 잡음 종류에 따라 기준치를 설정하여, 기준치와 유사한 화소에 필터링을 적용하여 최종 출력을 구한다. 시뮬레이션 결과 제안한 알고리즘은 우수한 잡음제거 특성을 나타내었으며, 기존 방법들과 비교하기 위해 PSNR 등을 이용하여 비교 및 분석하였다.

• Journal of Smart Tourism
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• 제1권3호
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• pp.31-44
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• 2021

The emergence of the digital economy and easy accessibility to Web 2.0 tools has seen an expansion of the influencer ecosystem within the travel and tourism industry. Founded on the principles of reference groups and peer reference there is a growing trend amongst industry practitioners who are now opting to move away from many of the traditional approaches used to market their products and services and are instead taking advantage of the concept of e-word-of-mouth (eWOM). Whilst there is a growing body of academic literature addressing the notion of influencer marketing, there is little understanding of influencer marketers themselves. Consequentially, this study addresses this gap in the literature through the quantitative examination of those who promote products, services, or companies by distributing eWOM through their online digital channels and presence; otherwise known as travel influencers. A quantitative research approach involving an online survey yielded 255 responses from travel influencers. The research findings indicate that those who work in this field prefer not to be awarded the label "travel influencer," focusing instead on their specific method of influencing, such as blogging and vlogging or sharing Instagram updates. The research also demonstrates how the new influencers have a strong role in generating travel urge and desire. The research contributes to the wider body of academic literature and travel industry practitioners by establishing the general profile of influencers and their increasingly specialized role in tourism and hospitality marketing.