• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2441-2446
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• 2018

This paper presents a radio frequency-to-direct current (RF-to-DC) converter for special RF power harvesting application at 915 MHz. The major featured components of the proposed RF-to-DC converter is the combination of a cross-coupled rectifier and an active diode: first, the cross-coupled rectifier boosts the input voltage to desired level, and an active diode blocks the reverse current, respectively. A prototype was implemented using $0.18{\mu}m$ CMOS technology, and the performance was proven from the fact that the targeted RF harvesting system's full-operation with higher power efficiency; even if the system's input power gets lower (e.g., from nominal 0 to min. -12 dBm), the proposed RF-to-DC converter constantly provides 1.47 V, which is exactly the voltage level to drive follow up system components like DC-to-DC converter and so on. And, maximum power conversion efficiency is 82 % calculated from the 0 dBm input power, 2.3 mA load current.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권5호
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• pp.552-567
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• 2017

The floating crane vessel in waves gives rise to the motion of the lifted object which is connected to the hoisting wire. The dynamic tension induced by the lifted object also affects the motion responses of the floating crane vessel in return. In this study, coupled motion responses of a floating crane vessel and a lifted subsea manifold during deep-water installation operations were investigated by both experiments and numerical calculations. A series of model tests for the deep-water lifting operation were performed at Ocean Engineering Basin of KRISO. For the model test, the vessel with a crane control system and a typical subsea manifold were examined. To validate the experimental results, a frequency-domain motion analysis method is applied. The coupled motion equations of the crane vessel and the lifted object are solved in the frequency domain with an additional linear stiffness matrix due to the hoisting wire. The hydrodynamic coefficients of the lifted object, which is a significant factor to affect the coupled dynamics, are estimated based on the perforation value of the structure and the CFD results. The discussions were made on three main points. First, the motion characteristics of the lifted object as well as the crane vessel were studied by comparing the calculation results. Second, the dynamic tension of the hoisting wire were evaluated under the various wave conditions. Final discussion was made on the effect of passive heave compensator on the motion and tension responses.

• 터널과지하공간
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• 제17권1호
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• pp.56-65
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• 2007

기존의 단열 시스템, 지하동굴 건설기술과 새로운 동결링 방벽기술을 결합하여 암반동굴식 지하 LNG 저장시스템이 개발되었다. 이 저장시스템의 기술적 적합성은 파일럿 동굴 실증시설의 건설과 운영을 통해 검증된 바 있으며, 조만간 실규모 프로젝트가 시작될 예정이다. LNG 저장시스템에서 중요한 사항 중의 하나는 극저온 열전달을 통해 장기간의 운영 기간동안 열손실을 최소화하는 것이다. 이 논문은 지하 LNG 저장 시스템의 설계를 위한 몇 가지 중요한 열전달 해석 결과를 제시하며, 기화율, 단열재 두께와 같은 설계 변수를 결정하기 위해 일련의 실규모 동굴에 대한 열전달 및 열-수리 해석을 실시하였다. 열-수리 연계해석결과 LNG 저장시설의 기화율은 초기 단계에서 0.04 %/day로 떨어져 유지되는 것으로 나타났다. 이 값은 암반내 존재하는 불연속면을 고려할 때 더욱 낮아질 수 있을 것으로 판단된다.

• 한국수자원학회논문집
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• 제44권4호
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• pp.285-293
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• 2011

본 연구에서는 제한된 수자원 부존량을 효율적으로 사용하고 각 댐의 저류량, 수요에 대한 용수공급량 및 하천유지용수를 최대화하기 위해 댐 상 하류간의 연계운영 모형을 이용하여 연계운영 효과를 분석하고 댐과 보의 최적 연계운영을 통한 하류단의 수문학적 거동 특성 변화를 검토하여 댐운영 개선방안 도출 등 다양한 하천관리 개선 방안에 대해 연구하였다. 대상유역은 신뢰성 높은 수문자료를 획득 가능한 금강 수계 유역으로 하였으며 수문자료는 순물소모량을 감안한 '67~'06년(40개년) 유입량(수자원장기종합계획, 2006)을 유역의 일유입량으로 변경하여 적용하였다. 연계운영 시 네트워크상에서 용수공급 가능한 범위는 연평가시 95%를 만족하는 신뢰도를 적용하였으며 기존에 건설된 용담, 대청댐에 의해 구해진 저수지수는 0.292로 산정되었고 향후 추가될 금남, 금강, 부여보에 의해 재산출된 저수지수는 0.297로 나타났다. 결과적으로 29.2%를 저류할 수 있는 상태에서 보가 추가되면서 29.7%로 저류량이 증가됨을 나타낸다. 규암지점의 유황변동특성을 분석한 결과, 각 단계가 증가할수록 저수량 $Q_{275}$과 갈수량 $Q_{355}$은 증가하고 풍수량 $Q_{95}$과 평수량 $Q_{185}$은 감소하여 대상지점의 유황이 전반적으로 개선되는 것을 확인할 수 있다. 특히, 갈수량의 경우 댐과 보에 의해 통제가 되지 않은 수치 보다 댐-보연계 시 $16.3m^3/s$ 증가하였다. 본 연구를 통해 자연상태의 유황보다 댐연계 및 댐-보 연계운영에 의해서 유황이 안정되고 이로 인해 안정적으로 이용할 수 있는 용수가 증가되는 것을 확인할 수 있었다.

• 한국전기전자재료학회논문지
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• 제26권1호
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• pp.68-72
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• 2013

The series connection-type superconducting fault current limiter (SFCL) with two magnetically coupled circuits was suggested and its effectiveness through the analysis on the current limiting and recovery characteristics was described. The fault current limiting characteristics of the proposed SFCL as well as the load voltage sag compensating characteristics according to the winding direction were investigated. To confirm the fault current limiting and the voltage sag suppressing characteristics of the this SFCL, the short-circuit tests for the simulated power system with the series connection-type SFCL were carried out. The series connection-type SFCL designed with the additive polarity winding was shown to perform more effective fault current limiting and load voltage sag compensating operations through the fast quench occurrence right after the fault appears and the fast recovery operation after the fault removes than that with the subtractive polarity winding.

• Nuclear Engineering and Technology
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• 제55권9호
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• pp.3213-3228
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• 2023

As an important part of the digital reactor, the pin-by-pin wise fine coupling calculation is a research hotspot in the field of nuclear engineering in recent years. It provides more precise and realistic simulation results for reactor design, operation and safety evaluation. CORCA-K a nodal code is redeveloped as a robust pin-by-pin wise neutronics and thermal-hydraulic coupled calculation code for pressurized water reactor (PWR) core. The nodal green's function method (NGFM) is used to solve the three-dimensional space-time neutron dynamics equation, and the single-phase single channel model and one-dimensional heat conduction model are used to solve the fluid field and fuel temperature field. The mesh scale of reactor core simulation is raised from the nodal-wise to the pin-wise. It is verified by two benchmarks: NEACRP 3D PWR and PWR MOX/UO₂. The results show that: 1) the pin-by-pin wise coupling calculation system has good accuracy and can accurately simulate the key parameters in steady-state and transient coupling conditions, which is in good agreement with the reference results; 2) Compared with the nodal-wise coupling calculation, the pin-by-pin wise coupling calculation improves the fuel peak temperature, the range of power distribution is expanded, and the lower limit is reduced more.

• 한국소음진동공학회논문집
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• 제12권11호
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• pp.847-855
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• 2002

A rotary compressors are used most widely In air-conditioning systems. Noise and vibration of a rotary compressor is an important problems during turning on and off as well as during operating. To estimate the vibration occurring during turning on and off, vibration analysis of a motor-compressor coupled system is required. In this paper, through modeling the motor and solving the forces from the equations of motion of the moving parts, the analysis of vibration of the compressor taking into consideration of the effects of motor and moving parts was performed. The accelerations of accumulator during turning on. turning off and operation are simulated. And simulated accelerations are compared with those of experimental data.

• Journal of the Optical Society of Korea
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• 제14권1호
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• pp.38-41
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• 2010

We design and fabricate a widely tunable laser diode made of InGaAsP-InP. The diode is monolithically integrated with a wavelength-selective coupled-ring reflector and semiconductor amplifiers. For realization of a compact size device, deeply etched multi-mode interference couplers and square ring resonators composed of total-internal-reflection mirrors are adopted and fabricated using a self-aligned process. It is demonstrated that the laser diode exhibits single mode operation and 16 nm tuning range with side-mode-suppression-ratio exceeding 20 dB.

• 한국소음진동공학회논문집
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• 제27권1호
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• pp.14-19
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• 2017

Fuel oil consumption cost varies depending on every ship operation and this roughly amounts to 70 % of shipping companies' total revenue. As such, efforts towards improved fuel economy are being pursued. An annual 1 % reduction in fuel consumption is perceived to result in saving tens million US dollars on the global fleet operation. One approach is the application of power take-off configurations which are seen to increase fuel oil economy and are suitable for power generation. In this study, the dynamic properties of a shaft generator coupled on a 10S90ME main engine of an 18 600 TEU container vessel is presented. The vibratory torque and angular velocity variation was examined through theoretical analysis and actual vibration measurement. The result of the study suggests a review on existing classification rules for generator design and the lowering of vibratory torque and angular velocity variation guideline.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2009년도 학술대회
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• pp.654-659
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• 2009

최근 웹을 기반으로 하는 소프트웨어가 발전하면서, 웹을 통한 서비스가 점차 증가하고 있다. 이것 때문에 많은 연구기관과 보고서들이 웹을 소프트웨어의 플랫폼이라고 부르고 있다. 이렇게 웹 기술이 발전하는 동안 Wireless Sensor Network(WSN)의 미들웨어와 응용 서비스는 데스크탑의 운영체제 기반에서 개발되었다. 그래서 WSN의 기술은 데스크탑 어플리케이션의 한계점을 가지고 있다. 그리고 센서 노드의 하드웨어와 밀접한 관련이 있는 강 결합(Tightly-Coupled) 구조 때문에 WSN의 통합, 응용 서비스 배포, 유지보수 관리 등에 어려움이 있다. 이와 다르게 Web 은 약 결합(Loosely-Coupled)이고 개방된 시스템이기 때문에 Web Service 나 Rich Internet Application(RIA)는 이러한 한계점을 해결할 수 있도록 도와준다. 특히 RIA는 웹 어플리케이션이지만 데스크탑 어플리케이션과 비슷한 사용자환경과 다양한 통신방법을 제공하기 때문에 WSN 응용서비스의 플랫폼이 될 수 있다. 본 연구에서 WSN의 연결성과 접근성을 인터넷으로 확장시키고 RIA를 적용하여 실시간 메시지 시스템을 제안한다.