• 소음진동
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• 제4권4호
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• pp.497-505
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• 1994

This paper presents a design scheme of the active noise absorber that consists of the feedforward and feedback controller. The feedback controller aims to increase damping for the specific acoustic mode. The feedforward controller synthesizes the input signal coherent with the primary noise source in order to attenuate the noise field in the broad frequency range. The feedforward controller is adapted to the variation of acoustic plants using the proposed algorithm which compensates the effect of feedback link. Experimental results demonstrate that the proposed method is effective for the active control of band-limited noise fields in the enclosure.

• 대한안전경영과학회지
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• 제17권3호
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• pp.125-132
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• 2015

The primary purpose of present study, to take appropriate measures to prevent occupational accidents in the food service industry, was to evaluate characteristics of working condition and occupational safety and health. In order to fulfill our objective, profession and working environment, safety recognition and education, safety activities, physical conditions and accident experience were surveyed. To collect information and opinion in the field, face-to-face interviews were, using a structured questionnaire, carried out. Also, food service industry's accidents reported by Korean Occupational Safety and Health Agency at 2014 were statistically analyzed. In the resulting of analyzing data from a questionnaire survey of food service industry employees, safety/health train and management were increased.

• 한국정보통신학회논문지
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• 제10권1호
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• pp.184-190
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• 2006

본 논문에서는 다중빔 스위칭 기능을 갖는 Ka 대역 통신해양기상위성의 통신 중계기를 이용한 고속 통신 서비스를 위한 링크 설계와 양질의 전송 서비스를 제공할 수 있는 최적의 전송 채널을 제안한다. 다양한 전송 서비스를 제공하는 Ka 대역 통신 중계기의 열화 요인으로 작용하는 군지연 및 비선형 그리고 이득 평탄도에 대한 채널 모델링과 성능 열화를 해석한다. 전송 데이터가 증가함에 따라 군지연과 비선형에 의한 영향은 증가하며, 군지연의 선형 성분과 비선형의 AM-AM 성분이 시스템 성능 열화에 지배적으로 작용하는 것을 알 수 있었다. 고속 데이터에 따른 광대역 전송 대역폭으로 낮은 군지연과 이득 평탄도를 얻기가 어려우므로 주로 열화 요소를 등화하여 넓은 범위의 초고속 위성통신 서비스에 효과적으로 제공하여야 한다. 분석된 결과는 통신해양기상위성을 이용한 최적의 고속 위성전송 시스템을 설계하고 운용하는데 활용될 수 있다.

• 지능정보연구
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• 제12권1호
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• pp.57-73
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• 2006

제조 라인의 설계에 있어서 물류설비의 선정은 매우 중요한 부분이다. 생산라인의 특성을 충분히 고려하여 물류설비를 선정하기 위해서는 다양한 요소들이 고려되어야 하며 그 요소들 가운데는 정량적인 요소(예, 자재 부피, 무게)들 뿐만 아니라 정성적인 요소(예, 유지 보수, 통합성)들도 포함된다. 정량적인 요소는 해당 물류설비의 사양 등을 통해 보다 쉽게 평가가 가능하지만 정성적인 요소는 객관적인 분석이 매우 어려운 부분이다. 실제 사례에서도 물류설비선정 시 정량적인 요소들만 검증되고 정성적인 요소들은 대부분 배제되는 것으로 나타나고 있다. 본 연구에서는 물류설비의 보다 효율적인 평가 및 선정을 위해 정량적인 요소뿐만 아니라 정성적인 요소들을 반영할 수 있는 방안을 제시하고자 한다. 이를 위해 전문가 지식 기반의 룰 (Rule) 및 퍼지 로직을 연계한 통합 방안을 개발하였다. 우선 전문가 지식 기반의 룰을 통해 해당 공정간 적절한 물류설비 유형 및 가능한 대안 유형들을 찾아내고 이들 중 정성적인 요소들까지를 반영하여 최적의 물류설비를 선정하기 위해 퍼지이론이 적용되었다. 본 연구를 통해 퍼지 이론의 제조 물류부분 적용 가능성을 제시하였다.

• Asian Pacific Journal of Cancer Prevention
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• 제15권18호
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• pp.7673-7677
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• 2014

Background: Patients with long-standing inflammatory bowel disease (IBD) have an increased risk of developing colorectal cancer (CRC). Colon cancer risk in IBD increases with longer duration and greater anatomic extent of colitis, the presence of primary sclerosing cholangitis, family history of CRC and degree of inflammation of the bowel. This study aimed to characterize the histopathological pattern of benign colorectal diseases among Saudi patients and to highlight age and gender variations of lesions as base line data for future studies to investigate the link between benign/IBD and colorectal cancers in the local population. Materials and Methods: The materials consisted of 684 biopsies, reported as benign (excluding malignancies and polyps) at the Department of Pathology, King Fahad Hospital, Madinah, Saudi Arabia from January 2006 to December 2013. Data collected and entered in MS-Excel and were analyzed using SPSS-20. Results: Of 684 colorectal tissues reviewed, 408 specimens (59.6%) were from male patients and 276 specimens (40.4%) were from females giving a male: female ratio of 1.5:1. Age of the patients ranged from 4 to 75 years with a mean of 39.6 years. The most frequent histologic diagnosis was a chronic non specific proctocolitis followed by ulcerative colitis, accounting respectively for 52.6% and 31.7% of all cases. These were followed by Crohn's disease 22 (3.2%), ischemic bowel disease 20 (2.9%), diverticular disease 14 (2%), eosinophilic colitis 12 (1.7%) and solitary rectal ulcer 12 (1.7%). A minority of 21 patients (3.1%) were cases of acute nonspecific proctocolitis, schistosomiasis, tuberculosis, volvulus and pseudomembranous colitis. Conclusions: These data show that although chronic non specific proctocolitis and ulcerative colitis were the dominant diagnoses, Crohn's disease, ischemic bowel disease and diverticular disease also existed to a lesser extent and should be considered in the differential diagnosis of benign colorectal diseases. This study provides a base line data for future studies which would be taken up to investigate the link between benign/IBD and colorectal cancers in the local population.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 춘계종합학술대회
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• pp.1113-1116
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• 2005

본 논문에서는 다중빔 스위칭 기능을 갖는 Ka 대역 통신해양기상위성의 통신 중계기를 이용한 고속통신 서비스를 위한 링크 설계와 양질의 전송 서비스를 제공할 수 있는 최적의 전송 채널을 제안한다. 다양한 전송 서비스를 제공하는 Ka 대역 통신 중계기의 열화 요인으로 작용하는 군 지연 및 비선형 그리고 이득 평탄도에 대한 채널 모델링과 성능 열화를 해석한다. 전송 데이터가 증가함에 따라 군지연과 비선형에 의한 영향은 증가하며, 군지연의 선형 성분과 비선형의 AM-AM 성분이 시스템 성능 열화에 지배적으로 작용하는 것을 알 수 있었다. 고속 데이터에 따른 광대역 전송 대역폭으로 낮은 군지연과 이득 평탄도를 얻기가 어려우므로 주요 열화 요소를 등화하여 수십 Mbps에서부터 수백 Mbps의 넓은 범위의 서비스를 동일 시스템에서 효과적으로 제공하여야 한다. 분석된 결과는 통신해양기상위성을 이용한 최적의 고속 위성전송 시스템을 설계하고 운용하는데 활용될 수 있다.

• 전력전자학회논문지
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• 제26권6호
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• pp.437-445
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• 2021

This paper proposes an operating frequency design method that limits the voltage applied to aload-side converter during the initial operation of a loosely coupled resonant dual-active bridge (LCR-DAB) converter and an initial operating strategy that applies it. The LCR-DAB converter uses two wireless power transfer coils instead of the high-frequency transformer of the general DAB converter. The wireless power coil has a physical distance of several tens of millimeter or more between the two coils; thus, the LCR-DAB converter is a bidirectional isolated power conversion system that can easily achieve high insulation performance. However, for the initial operation of the LCR-DAB, if the power-side converter is operated at the resonance frequency while the load-side converter is not operating, then a very high voltage due to resonance is applied to the load-side converter, thereby causing damage to the converter. Therefore, a method that can stably charge the DC link voltage of the secondary-side converter during the initial operation is needed. This paper proposes a method to initially charge the secondary-side DC link by operating the primary-side converter at a frequency with limited voltage gain rather than at a steady-state operating frequency. The validity of the proposed frequency design method and initial operating sequence is verified through simulation and experimentation of the 1 KW LCR-DAB converter.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권3호
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• pp.890-910
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• 2014

This paper investigates the spectrum hole utilization of cooperative schemes for the two-way relaying model in order to improve the utilization efficiency of limited spectrum holes in cognitive radio networks with imperfect spectrum sensing. We propose two specific bidirectional secondary data transmission (BSDT) schemes with two-step and three-step two-way relaying models, i.e., two-BSDT and three-BSDT schemes, where the spectrum sensing and the secondary data transmission are jointly designed. In the proposed cooperative schemes, the best two-way relay channel between two secondary users is selected from a group of secondary users serving as cognitive relays and assists the bi-directional communication between the two secondary users without a direct link. The closed-form asymptotic expressions for outage probabilities of the two schemes are derived with a primary user protection constraint over Rayleigh fading channels. Based on the derived outage probabilities, the spectrum hole utilization is calculated to evaluate the percentage of spectrum holes used by the two secondary users for their successful information exchange without channel outage. Numerical results show that the spectrum hole utilization depends on the spectrum sensing overhead and the channel gain from a primary user to secondary users. Additionally, we compare the spectrum hole utilization of the two schemes as the varying of secondary signal to noise ratio, the number of cognitive relays, and symmetric and asymmetric channels.

• 천문학회지
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• 제36권spc1호
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• pp.125-133
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• 2003

New Jersey Institute of Technology (NJIT), in collaboration with the University of Hawaii (UH), is upgrading Big Bear Solar Observatory (BBSO) by replacing its principal, 65 cm aperture telescope with a modern, off-axis 1.6 m clear aperture instrument from a 1.7 m blank. The new telescope offers a significant incremental improvement in ground-based infrared and high angular resolution capabilities, and enhances our continuing program to understand photospheric magneto-convection and chromospheric dynamics. These are the drivers for what is broadly called space weather - an important problem, which impacts human technologies and life on earth. This New Solar Telescope (NST) will use the existing BBSO pedestal, pier and observatory building, which will be modified to accept the larger open telescope structure. It will be operated together with our 10 inch (for larger field-of-view vector magnetograms, Ca II K and Ha observations) and Singer-Link (full disk H$\alpha$, Ca II K and white light) synoptic telescopes. The NST optical and software control design will be similar to the existing SOLARC (UH) and the planned Advanced Technology Solar Telescope (ATST) facility led by the National Solar Observatory (NSO) - all three are off-axis designs. The NST will be available to guest observers and will continue BBSO's open data policy. The polishing of the primary will be done in partnership with the University of Arizona Mirror Lab, where their proof-of-concept for figuring 8 m pieces of 20 m nighttime telescopes will be the NST's primary mirror. We plan for the NST's first light in late 2005. This new telescope will be the largest aperture solar telescope, and the largest aperture off-axis telescope, located in one of the best observing sites. It will enable new, cutting edge science. The scientific results will be extremely important to space weather and global climate change research.

• 한국정보통신학회논문지
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• 제16권4호
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• pp.701-712
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• 2012

장애 복구형 백본 네트워크에서 경로의 짧은 거리 및 빠른 전파 지연시간은 주 경로와 백업 경로의 설정시 활용될 수 있는 중요한 성능 인자이기에 이에 $k$-최단 분리 경로 개념은 이러한 백본 네트워크 환경에서 매우 중요하게 고려된다. 이에 본 논문에서는 선박 장비 간의 중복 메시지 전송 기능을 명세하는 IEC61162-410 표준이 적용된 장애 복구형 선박 백본 네트워크에서 $k$-최단 분리 경로 개념의 적합성을 비교 평가하였다. 성능 평가는 링크 용량, 주경로 및 백업 경로의 홉 및 거리, 트래픽 흐름의 균등 분포, 백업 경로의 장애 복구 시간, 그리고 물리 네트워크 토폴로지의 연결성 측면에서 수행되었다.