• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.694-697
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• 2001

A optimal soft switching technique for A/DC full bridge converter is proposed. variable soft switching single stage AC/DC full bridge converter with unit power factor are presented in this paper. Using soft switching, we can reduce a switching losses. As a result, achieving good power factor and achieving a good efficiency. We search a optimal soft switching technique in this paper and to verify the theoretical analysis of the presented AC/DC full bridge converter, a design example is given with its Pspice and Psim simulation and experimental results.

• 한국컴퓨터정보학회논문지
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• 제24권7호
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• pp.71-78
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• 2019

This paper describes a design for a RF receiver to receive satellite digital audio service. The RF receiver designed in this study is a planar structure that is easy to install on the rooftop of a car and is compact in size. In addition, it can be applied to certain commercial models because it has low noise and high gain characteristics. The impedance bandwidth of antenna is 17.8%(415MHz), and the axial ratio is below 3dB as good properties for the bandwidth of 40MHz which is a satellite digital audio service band. Also, it had a broad radiation beamwidth of $95.41^{\circ}$ in H-plane and $117.45^{\circ}$ in E-plane. From the results of the field test of satellite digital audio service reception for the RF receiver, it demonstrated good C/N rate(10.2dB).

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2011년도 춘계학술발표대회
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• pp.1398-1400
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• 2011

2000년 초에 PC간 인터넷을 통한 음성통화를 시작으로 최근에는 스마트폰의 전용 애플리케이션까지 VoIP 기반의 음성통화 서비스가 발전해왔다. 이에 따라, VoIP를 통한 외부 공격 및 침입에 대한 사례가 발생되고 이를 해결하기 위한 보안 소프트웨어들이 나오기 시작하였다. 일반적으로 VoIP기반의 소프트웨어에 대한 품질 기준은 사용자의 통화품질이 최우선 이었다. 하지만, GS시험.인증 과정을 통해 VoIP 보안 소프트웨어가 통화품질에는 직접적인 영향을 미치지는 않지만 전체 운영 시스템에 미치는 영향을 확인하고, 시험 중 발생한 문제에 대한 해결 방안 제시를 통해 VoIP의 품질을 향상시킬 수 있었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권2호
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• pp.583-599
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• 2015

We apply the Bayesian matching pursuit (BMP) algorithm to the estimation of time-frequency selective channels in orthogonal frequency division multiplexing (OFDM) systems. By exploiting prior statistics and sparse characteristics of propagation channels, the Bayesian method provides a more accurate and efficient detection of the channel status information (CSI) than do conventional sparse channel estimation methods that are based on compressive sensing (CS) technologies. Using a reasonable approximation of the system model and a skillfully designed pilot arrangement, the proposed estimation scheme is able to address the Doppler-induced inter-carrier interference (ICI) with a relatively low complexity. Moreover, to further reduce the computational cost of the channel estimation, we make some modifications to the BMP algorithm. The modified algorithm can make good use of the group-sparse structure of doubly selective channels and thus reconstruct the CSI more efficiently than does the original BMP algorithm, which treats the sparse signals in the conventional manner and ignores the specific structure of their sparsity patterns. Numerical results demonstrate that the proposed Bayesian estimation has a good performance over rapidly time-varying channels.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권11호
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• pp.4311-4330
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• 2015

Cloud computing has become a new paradigm by enabling on-demand provisioning of applications, platforms or computing resources for clients. Workflow scheduling has always been treated as one of the most challenging problems in clouds. Commercial clouds have been widely used in scientific research, such as biology, astronomy and weather forecasting. Certainly, it is very important for a cloud service provider to pursue the profits for the commercial essence of clouds. This is also significantly important for the case of providing services to workflow tasks. In this paper, we address the issues of workflow scheduling in commercial clouds. This work takes the communication into account, which has always been ignored. And then, a topology-based workflow-scheduling algorithm named Resource Auction Algorithm (REAL) is proposed in the objective of getting more profits. The algorithm gives a good performance on searching for the optimum schedule for a sample workflow. Also, we find that there exists a certain resource amount, which gets the most profits to help us get more enthusiasm for further developing the research. Experimental results demonstrate that the analysis of the strategies for most profits is reasonable, and REAL gives a good performance on efficiently getting an optimized scheme with low computing complexity.

• Journal of electromagnetic engineering and science
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• 제16권1호
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• pp.13-18
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• 2016

This paper presents a design of an impedance transformer (IT) with high frequency selectivity characteristics. The frequency selectivity can be controlled by even- and odd-mode impedance of a shunt coupled transmission line (TL). For experimental validation, a 50- to $20-{\Omega}$ IT was implemented at a center frequency ($f_0$) of 2.6 GHz for the long-term evolution signal. The measured results were in good agreement with the simulations, showing a return loss higher than 19 dB over a passband bandwidth of 0.63 GHz (2.28-2.91 GHz) and good sharp frequency selectivity characteristic near to the passband. The series coupled TL provides a transmission zero at 5.75 GHz, whereas the shunt coupled TL provides three transmission zeros located at 2 GHz, 3.1 GHz, and 7.14 GHz.

• Journal of Information Processing Systems
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• 제14권3호
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• pp.666-679
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• 2018

The discrete wavelet transform (DWT) has good multi-resolution decomposition characteristic and its low frequency component contains the basic information of an image. Based on this, a fragile watermarking using the local binary pattern (LBP) and DWT is proposed for image authentication. In this method, the LBP pattern of low frequency wavelet coefficients is adopted as a feature watermark, and it is inserted into the least significant bit (LSB) of the maximum pixel value in each block of host image. To guarantee the safety of the proposed algorithm, the logistic map is applied to encrypt the watermark. In addition, the locations of the maximum pixel values are stored in advance, which will be used to extract watermark on the receiving side. Due to the use of DWT, the watermarked image generated by the proposed scheme has high visual quality. Compared with other state-of-the-art watermarking methods, experimental results manifest that the proposed algorithm not only has lower watermark payloads, but also achieves good performance in tamper identification and localization for various attacks.

• 한국임상약학회지
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• 제24권4호
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• pp.272-281
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• 2014

Objective: The provision of pharmaceutical care service in compliance with good pharmacy practice (GPP) standards is important, but there is lack of studies to investigate the barriers that significantly hinder community pharmacies in Korea from adhering to the standards. This study was aimed to identify the major barriers to provision of pharmaceutical care service in compliance with the proposed pharmacy practice standards which have been developed based on the GPP standards recommended jointly by WHO and FIP. Methods: Questionnaires reviewed by the expert committee were posted for 32 days on the website which is most frequently accessed by community pharmacists. The respondents completed them by checking the scores (Max=5, Min=1) for major barriers to provision of pharmaceutical care service focusing on patient information management and drug use review process in prescription fillings. The answered scores were automatically collected using online data processing. Mean differences between scored data were assessed by ANOVA. Results: Total 321 pharmacists participated in the survey. Results indicated that 'difficulty of diagnosis identification' (m=3.92, SD=1.21), 'lack of time' (m=3.48, SD=1.22) and 'lack of updated clinical information' (m=3.17, SD=1.10) were the major barriers to provision of pharmaceutical care service in patient information management. The main barriers to drug utilization review were 'lack of time' (m=3.32, SD=1.21), 'lack of updated clinical information' (m=3.11, SD=1.17), and 'negative feedbacks or refusals from prescribers' (m=3.00, SD=1.38). There were significant differences among the groups by location, employed number of pharmacists and acceptability to the proposed GPP standards. Conclusion: Difficulties in managing patient clinical information and lack of time were found to be the major barriers in providing pharmaceutical care services in community pharmacies in Korea. Further research is recommended to determine ways to reduce these barriers in order to provide quality pharmaceutical care service that is in compliance with the internationally recognized GPP guidelines.

• 한국문헌정보학회지
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• 제46권2호
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• pp.115-132
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• 2012

이 연구의 목적은 차세대 도서관 목록에서 이용자 서평 기능의 이용 현황 및 서지레코드에서 연결될 수 있는 외부 정보원의 이용자 서평의 영향 가능성을 살펴보는 것이다. 2012년 2월 16일부터 4월 4일 사이에 2010년에 출간된 열권의 책을 대상으로 WorldCat에서 소장도서관, 이용자 서평, 태그 및 독서 리스트의 현황 및 변동 추이, 그리고 서지레코드에 연결된 Amazon.com과 GoodReads.com의 이용자 서평 현황을 살펴보았다. WorldCat에서 아직 이용자 참여 기능의 활용도는 매우 낮았으며, 이용자 서평보다는 태그나 독서 리스트를 통한 참여가 더 많았다. 같은 책들에 대한 아마존과 굿리즈의 이용자 서평 참여도는 매우 높았고, 아마존에서 한 권의 책과 관련된 이용자 서평 사례 분석은 이용자 참여 기능이 왜곡될 수 있는 가능성을 암시하였다. 아직은 초기 단계인 도서관 목록에 대한 이용자 참여 기능의 확산 및 안정화 추이의 지속적 관찰, 그리고 이 기능이 이용자의 자료 선택에 미치는 영향의 심층적, 체계적 분석이 필요하다.

• 한국정보전자통신기술학회논문지
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• 제7권2호
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• pp.92-99
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• 2014

기존연구는 양택(陽宅)에서 형기풍수(形氣風水)를 적용한 건축물에 관한 사례연구는 많이 하였으나, 현공풍수(玄空風水)를 적용한 건축물에 대한 사례연구는 미흡하다. 따라서 본 연구에서는 현공풍수(玄空風水)를 적용한 서울시 종로구에 위치하는 A, B, C 빌딩의 사례를 연구하고자 한다. 연구결과 첫째, A빌딩의 지운(地運)이 가장 긴 것으로 나타났다. 이 결과는 A빌딩은 복(福)이 오랫동안 유지된다는 의미이다. 둘째, 4국에서 왕산왕향(旺山旺向)은 A빌딩과 B빌딩에서 파악되었다. 이 결과는 배산임수(背山臨水)와 같은 형국으로 좋은 국(局)을 갖추었다는 의미이다. 셋째, 이기풍수(理氣風水)로 판단한 길흉은 "상"으로 양호한 편으로 나타났다. 이 결과는 시간과 공간이 잘 형성되어 길한 빌딩으로 기업성장에 큰 발전이 있을 것으로 사료된다.