• Current Optics and Photonics
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• 제6권1호
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• pp.39-43
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• 2022

Underwater optical wireless communication (UOWC) is a good candidate for high-speed underwater wireless communication. In this work, we compare the performance of several modulation techniques for a UOWC system consisting of a light-emitting diode (LED) with an operating wavelength of 405 nm and a Si avalanche photodiode (APD). In this work, we consider six modulation schemes: 4-quadrature amplitude modulation (QAM), 8-QAM, quadrature phase shift keying (QPSK), binary phase shift keying (BPSK), on-off keying (OOK), and 4-pulse amplitude modulation (PAM). We also consider the cases of pure water and seawater for the working conditions. Our results show that 4-QAM and 8-QAM perform the best, in terms of communication distance and transmission power efficiency, for all water types considered.

• 센서학회지
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• 제30권4호
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• pp.223-228
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• 2021

This work presents a low-power CMOS image sensor (CIS) with a multi-column-parallel (MCP) readout structure while focusing on improving its performance compared to previous works. A delta readout scheme that utilizes the image characteristics is optimized for the MCP readout structure. By simply alternating the MCP readout direction for each row selection, additional memory for the row-to-row delta readout is not required, resulting in a reduced area of occupation compared to the previous work. In addition, the bias current of a pre-amplifier in a successive approximate register (SAR) analog-to-digital converter (ADC) changes according to the operating period to improve the power efficiency. The prototype CIS chip was fabricated using a 0.18-㎛ CMOS process. A 160 × 120 pixel array with 4.4 ㎛ pitch was implemented with a 10-bit SAR ADC. The prototype CIS demonstrated a frame rate of 120 fps with a total power consumption of 1.92 mW.

• Communications for Statistical Applications and Methods
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• 제29권5호
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• pp.533-545
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• 2022

Collection of data on several variables, especially in the field of medicine, results in the problem of measurement errors. The presence of such measurement errors may influence the outcomes or estimates of the parameter in the model. In classification scenario, the presence of measurement errors will affect the intrinsic cum summary measures of Receiver Operating Characteristic (ROC) curve. In the context of ROC curve, only a few researchers have attempted to study the problem of measurement errors in estimating the area under their respective ROC curves in the framework of univariate setup. In this paper, we work on the estimation of area under the multivariate ROC curve in the presence of measurement errors. The proposed work is supported with a real dataset and simulation studies. Results show that the proposed bias-corrected estimator helps in correcting the AUC with minimum bias and minimum mean square error.

• 한국재료학회지
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• 제32권8호
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• pp.333-338
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• 2022

In this work, we developed silver nanowires and a silicon based Schottky junction and demonstrated ultrafast broadband photosensing behavior. The current device had a response speed that was ultrafast, with a rising time of 36 ㎲ and a falling time of 382 ㎲, and it had a high level of repeatability across a broad spectrum of wavelengths (λ = 365 to 940 nm). Furthermore, it exhibited excellent responsivity of 60 mA/W and a significant detectivity of 3.5 × 10¹² Jones at a λ = 940 nm with an intensity of 0.2 mW cm^-2 under zero bias operating voltage, which reflects a boost of 50 %, by using the AC PV effect. This excellent broadband performance was caused by the photon-induced alternative photocurrent effect, which changed the way the optoelectronics work. This innovative approach will open a second door to the potential design of a broadband ultrafast device for use in cutting-edge optoelectronics.

• 한국정밀공학회지
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• 제10권1호
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• pp.62-69
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• 1993

The accuracy of machine tools is the major factor concerned with the acuracy of the processed work. The feed errors of feed system in machine tool, therfore, make the machining errors of work directly on processing. In this point, this study focused on the generative elements of feed errors in CNC cylindrical grinding machine, such as supporting method of ball screw, the effect of pitch and yaw error and the position detecting method in servo system when operating its shaft of grinding wheel head. Furthermore, in order to improve the driving accuracy of this machine tool, feed errors are measured by a laser interferometer. Results obtained in this study provide some useful informations to attain high accuracy of CNC machine tool.

• 대한안전경영과학회지
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• 제25권2호
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• pp.91-97
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• 2023

Ensuring the safe arrival of delivery cargo at its intended destination is of utmost importance. Truck drivers play a crucial role in guaranteeing the secure delivery of cargo without any mishaps. However, there are various factors that may lead to delayed arrival of trucks at their destination, such as late departures or prolonged loading operations. The timely departure of cargo transportation is contingent upon several variables, including the driver's experience, cargo volume, and loading time. If the transportation commencement is delayed, it may increase the risk of accidents due to an elevated operating speed. Consequently, we conducted a study to investigate the correlation between cargo loading time, cargo volume, driving experience, and the likelihood of accidents. Our findings indicate that both cargo volume and driver experience can impact the likelihood of vehicle accidents. Furthermore, all factors can have an interactive effect on the occurrence of accidents. However, extending the loading time may mitigate the impact on the likelihood of accidents.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2020년도 추계학술대회
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• pp.153-154
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• 2020

컨테이너 터미널 업무 중 현장 근무가 필요하지 않은 업무를 중심으로 스마트워크 서비스로 대체 할 수 있다. 여기서, 클라우드 서비스는 초기 시스템 구축에 들어가는 비용과 시간을 줄이고, 필요한 만큼 사용료를 지불할 수 있어 중소규모 하역회사에 도움이 된다. 본 연구는 터미널운영시스템에 첨단 ICT를 연계 활용 할 수 있도록 산업 표준을 준수하는 웹서비스 개발에 대한 사례 연구를 소개한다.

• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.418-425
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• 2022

For a commercial building, property managers play an important role in maximizing the benefit by reducing cost and increasing revenue in the operation and maintenance phase of the building. However, most of property managers are spending their time in monitoring facility managers who have little impact on cost reduction and maximization of operating profit. The industry practitioners have difficutlty in increasing the efficiency of thier work due to this work environment. In addition, both property managers(PMr) and facility managers(FMr) are dependent on the paper drawings and manuals, which can worsen the inefficiency and human errors are inevitable. This study aims to contribute to improvement of the current practice by developing a novel algorithm that autmatically links the facility information with 3D model, which can provide an efficient property management for commercial buildings.

• 통상정보연구
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• 제14권2호
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• pp.249-269
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• 2012

본 연구는 선행 연구와 실증연구를 병행하여 글로벌 제휴네트워크 추진 동기가 기업 역량, 파트너 역량, 운영구조, 제휴 성과에 미치는 영향을 실증하였다. 연구 개념 사이에 영향을 검증하기 위하여 글로벌 제휴나 협력을 공시한 업체 중 기준에 적합한 업체 114곳에서 설문자료를 수집하여 빈도분석, 신뢰도분석, 요인분석, 확인 요인분석, 구조방정식 모형분석, 회귀분석을 각각 하였다. 연구결과를 요약하면 다음과 같다. 첫째, 추진 동기는 기업 역량, 파트너 역량, 운영구조에 영향을 미치는 것으로 나타났다. 추진 동기는 제도환경에 적응, 실물옵션 행사(위험을 분산하기 위한 포트폴리오 구성), 자원의 확보와 활용, 거래비용 절감, 시장지배력 강화로서 다양한 동기가 제휴 전후에 영향을 미친다고 볼 수 있다. 특히 추진 동기는 운영구조에 영향을 더 많이 미쳤는데, 지식을 공유하고 습득하기 위한 활동과 규범 개발, 성과평가 등으로 제휴목표를 달성하려는 것으로 볼 수 있다. 둘째, 기업 역량과 파트너 역량은 운영구조에 영향을 미쳤다. 운영구조는 기업 역량과 파트너 역량으로써 각 고유한 특성을 반영하여 문화, 제도 등을 확립하고 제휴활동을 원활히 하기 위한 것으로 볼 수 있다. 셋째, 기업 역량과 운영구조는 제휴 성과에 영향을 미쳤다. 제휴 성과는 전략 목표나 제휴 목표의 달성, 사업가치의 증진 등으로 나타났는데, 목표를 달성하려면 고유한 자원, 능력, 지식, 기술이 중심이 되어 파트너 역량을 흡수하고 통합하는 과정이 제휴 성과에 영향을 미친다고 볼 수 있다. 특히 운영구조는 기업 역량과 파트너 역량이 거의 비슷하게 영향을 미쳤지만, 제휴 성과는 파트너 역량이 제외되어 파트너 역량을 내부화하고 학습하는 과정이 반영되었다고 볼 수 있다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제31회 춘계학술대회
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• pp.219-226
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• 2000

Frictional performance of ring pack in internal engine is investigated by varying spatial dimensions of ring pack and operating speed. This investigation is performed with commercial software by Ricardo Consultant Engineers, Inc. which is now in wofdwide use in automobile industries. Among the ring performances, blow-by rate, axial ring motions and frictional behaviors of top and second rings are studies in our work.