• 한국태양에너지학회 논문집
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• 제25권2호
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• pp.63-69
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• 2005

This study is the survey of a transition procedure of building services systems(heat source, HVAC, water supply) through the survey of existing office buildings, building design documents. The preference & major consideration of system selection is the engineer's opinions. The results of this survey can be used in selection of building services system design. In this survey, "Hot & cold water generator system" and "single duct CAV+FCU system", "Elevated water tank system" are selected. The most important consideration in system selection is the energy saving in heat source system, and comfort in HVAC system, and water pressure in water supply system. They prefer "steam boiler+absorption chiller system" for heat source system, "steam boiler+ice thermal storage system", "hot & cold water generator system", "district heating+absorption chiller system" : "single duct CAV+FCU system" and "single duct VAV+convector system" for HVAC system: and "booster pump system" for water supply system.

• 기술혁신학회지
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• 제19권1호
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• pp.1-28
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• 2016

현재 우리나라 혁신시스템은 기존의 성장 및 기술공급 위주의 발전전략이 한계를 노정하면서 새로운 전환기를 맞고 있다. 이에 새로운 혁신 경로 창출을 위한 과학기술 ICT 정책 패러다임 전환은 물론 지속가능한 에너지, 농업 농촌 등 다양한 영역에서의 시스템 전환이 필요한 상황이다. 리빙랩은 사용자 참여를 기반으로 하는 새로운 혁신모델이자 지속가능한 시스템 전환의 니치 실험으로서 유럽을 중심으로 논의되고 있다. 본 연구에서는 과학기술 ICT가 에너지 전환, 농업 농촌 시스템 전환, ICT 정책 패러다임의 전환에 적용된 리빙랩 사례를 살펴보고 우리나라에서의 시사점을 도출하였다. 유럽의 SusLab 프로젝트, C@R 프로그램, 대만의 리빙랩 사례 모두 사전기획 단계부터 지역 사용자의 배경과 경험을 적극적으로 수집하고, 사용자 주도의 혁신활동을 개발프로세스 전반에서 유지함으로써 다양한 전환 실험을 성공적으로 추진하였다. 이러한 결과는 중앙정부와 지자체가 리빙랩 도입을 검토하는 현 상황에 맞춰 다양한 시사점을 제공한다. 리빙랩은 국가 또는 지역 전반의 사회 기술시스템의 전환을 위한 전략적 니치 실험, 정책 간 연계통합의 수단, 새로운 지역혁신 모델로 활용될 수 있다. 또한 최근 혁신정책 패러다임에서 강조하고 있는 사용자 및 수요 측면을 반영한 정책통합을 실현할 수 있는 중요한 플랫폼이 될 수 있다.

• ETRI Journal
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• 제23권4호
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• pp.151-157
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• 2001

Spectroscopic and thermal analysis indicates that tellurite glasses doped with $B_2O_3$ and $GeO_2$ are promising candidate host materials for wide-band erbium doped fiber amplifier (EDFA) with a high 980 nm pump efficiency. In this study, we measured the thermal stabilities and the emission cross-sections for $Er^{3+}:^{4}I_{13/2}\;{\to}\;^{4}I_{15/2}$ transition in this tellurite glass system. We also determined the Judd-Ofelt parameters and calculated the radiative transition rates and the multiphonon relaxation rates in this glass system. The 15 mol% substitution of $B_2O_3$ for $TeO_2$ in the $Er^{3+}-doped\;75TeO_2-20ZnO-5K_2O$ glass raised the multiphonon relaxation rate for $^4I_{11/2}\;{\to}\;^4I_{13/2}$ transition from 4960 $s^{-1}$ to 24700 $s^{-1}$, but shortened the lifetime of the $^4I_{13/2}$ level by 14 % and reduced the emission cross-section for the $^4I_{13/2}\;{\to}\;^4I_{15/2}$ transition by 11%. The 15 mol% $GeO_2$ substitution in the same glass system also reduced the emission cross-section but increased the lifetime by 7%. However, the multiphonon relaxation rate for $^4I_{11/2}{\to}^4I_{13/2}$ transition was raised merely by 1000 $s^{-1}$. Therefore, a mixed substitution of $B_2O_3$ and $GeO_2$ for $TeO_2$ was concluded to be suitable for the 980 nm pump efficiency and the fluorescence efficiency of $^4I_{13/2}{\to}^4I_{15/2}$ transition in $Er^{3+}-doped$ tellurite glasses.

• Journal of Preventive Medicine and Public Health
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• 제43권5호
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• pp.423-435
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• 2010

Objectives: The low benefit coverage rate of South Korea's health security system has been continually pointed out. A low benefit coverage rate inevitably causes catastrophic health expenditure, which can be the cause of the transition to poverty and the persistence of poverty. This study was conducted to ascertain the effect of catastrophic health expenditure on the transition to poverty and the persistence of poverty in South Korea. Methods: To determine the degree of social mobility, this study was conducted among the 6311 households that participated in the South Korea Welfare Panel Study in both 2006 and 2008. The effect of catastrophic health expenditure on the transition to poverty and the persistence of poverty in South Korea was assessed via multiple logistic regression analysis. Results: The poverty rate in South Korea was 21.6% in 2006 and 20.0% in 2008. 25.1 - 7.3% of the households are facing catastrophic health expenditure. Catastrophic health expenditure was found to affect the transition to poverty even after adjusting for the characteristics of the household and the head of the household, at the threshold of 28% or above. Conclusions: 25.1% of the households in this study were found to be currently facing catastrophic health expenditure, and it was determined that catastrophic health expenditure is a cause of transition to poverty. This result shows that South Korea's health security system is not an effective social safety net. As such, to prevent catastrophic health expenditure and transition to poverty, the benefit coverage of South Korea's health security system needs to the strengthened.

• 한국철도학회논문집
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• 제17권4호
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• pp.260-269
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• 2014

본 논문의 목적은 철도교량 단부 전환부 궤도의 구조적 거동특성을 평가하는 것이다. 국내 고속철도 교량상 궤도표준단면을 이용하여 전환부 궤도구조를 설계 및 제작하여 피로시험 전, 후에 대한 전환부 궤도시스템의 중립축 및 동특성(고유진동수 및 감쇠비)의 변화를 비롯하여 피로균열 발생경향을 수치해석 결과와 비교, 검토하였다. 연구결과, 국내 고속철도 궤도설계기준을 준용하여 설계한 전환부 궤도시스템에 대한 동특성을 실험적으로 산정하였으며 국내 철도하중 및 충격효과를 고려한 피로하중에 대한 구조적 건전성을 실험 및 해석적으로 입증하였다.

• Journal of Power Electronics
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• 제19권5호
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• pp.1224-1234
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• 2019

Hybrid rotor position estimation methods that integrate a fundamental model and high frequency (HF) signal injection are widely used for the wide speed-range sensorless control of interior permanent-magnet synchronous machines (IPMSMs). However, the direct transition of two different schemes may lead to system fluctuations or system instability since two estimated rotor positions based on two different schemes are always unequal due to the effects of parameter variations, system delays and inverter nonlinearities. In order to avoid these problems, a seamless transition strategy to define and construct a virtual q-axis inductance is proposed in this paper. With the proposed seamless transition strategy, an estimated rotor position based on a fundamental model is forced to track that based on HF signal injection before the transition by adjusting the constructed virtual q-axis inductance. Meanwhile, considering that the virtual q-axis inductance changes with rotor position estimation errors, a new observer with a two-phase phase-locked loop (TP-PLL) is developed to accurately obtain the virtual q-axis inductance online. Furthermore, IPMSM sensorless control with maximum torque per ampere (MTPA) operations can be tracked automatically by selecting the proper virtual q-axis inductance. Finally, experimental results obtained from an IPMSM demonstrate the feasibility of the proposed seamless transition strategy.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.513-520
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• 2004

A steady-state/transient performance simulation model was newly developed for the propulsion system of the CRW (Canard Rotor Wing) type UAV (Unmanned Aerial Vehicle) during flight mode transition. The CRW type UAV has a new concept RPV (Remotely Piloted Vehicle) which can fly at two flight modes such as the take-off/landing and low speed forward flight mode using the rotary wing driven by engine bypass exhaust gas and the high speed forward flight mode using the stopped wing and main engine thrust. The propulsion system of the CRW type UAV consists of the main engine system and the duct system. The flight vehicle may generally select a proper type and specific engine with acceptable thrust level to meet the flight mission in the propulsion system design phase. In this study, a turbojet engine with one spool was selected by decision of the vehicle system designer, and the duct system is composed of main duct, rotor duct, master valve, rotor tip-jet nozzles, and variable area main nozzle. In order to establish the safe flight mode transition region of the propulsion system, steady-state and transient performance simulation should be needed. Using this simulation model, the optimal fuel flow schedules were obtained to keep the proper surge margin and the turbine inlet temperature limitation through steady-state and transient performance estimation. Furthermore, these analysis results will be used to the control optimization of the propulsion system, later. In the transient performance model, ICV (Inter-Component Volume) model was used. The performance analysis using the developed models was performed at various flight conditions and fuel flow schedules, and these results could set the safe flight mode transition region to satisfy the turbine inlet temperature overshoot limitation as well as the compressor surge margin. Because the engine performance simulation results without the duct system were well agreed with the engine manufacturer's data and the analysis results using a commercial program, it was confirmed that the validity of the proposed performance model was verified. However, the propulsion system performance model including the duct system will be compared with experimental measuring data, later.

• Journal of Power Electronics
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• 제11권4호
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• pp.464-470
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• 2011

In this paper, the feasibility of applying a position sensorless control technique to hybrid electric vehicles (HEVs) is practically evaluated. The proposed position estimator has a straightforward structure with properties that combines the model and the saliency tracking-based rotor position estimation for interior permanent magnet synchronous motors (IPMSMs). The proposed method can be used in the event of sensor loss or sensor recovery to sustain continuity of operations. The developed system takes into account the estimated position transition between two distinct sensorless methods. The transition is enhanced by introducing a synchronized transition algorithm based on a single tracking observer. Extensive experimental results are presented to verify the principles and show a reliable estimation performance over the entire speed range including standstill under 150% load conditions.

• 한국기계가공학회지
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• 제10권3호
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• pp.100-107
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• 2011

To evaluate the wear characteristics of very thin ceramic coated layer, it is very important to investigate its wear process in great detail. An effective method for investigating the wear of a thin layer is the observation of wear process in microscopic detail, using in-situ system. In this study, based on the SEM Tribosystem as in-situ system, the microscopic wear mode of TiN coatings was investigated in repeated sliding. Consequently, four modes were revealed for TiN coatings: Ploughing, powder formation, flake formation and coating delimitation. Sc(Severity of contact) can clarify transition condition of those microscopic wear modes.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.167-169
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• 2003

This paper presents a theoretical study concerning multibubble dynamics in a sound field and the numerical validation for it by employing our new CFD code MTS-DiCUP. In recent papers, the author has shown theoretically that an unknown characteristic frequency, named 'transition frequency,' exists in a multibubble system. For a N -bubble case, up to 2N -1 transition frequencies per bubble have been predicted, only N ones of them correspond to the natural frequencies of the system. The transition frequencies that do not correspond to the natural frequencies give rise to the phase reversal of bubbles' pulsation without resonant response. In this paper, it has been suggested theoretically that those transition frequencies may cause the sign reversal of the secondary Bjerknes force, which is an interaction force acting between acoustically coupled gas bubbles. This theoretical result has been validated by the direct numerical simulation, at least in a qualitative sense.