• International Journal of Control, Automation, and Systems
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• 제5권1호
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• pp.24-34
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• 2007

Closed-loop active twist control of integral helicopter rotor blades is investigated in this paper for reducing hub vibration induced in forward flight. A four-bladed fully articulated integral twist-actuated rotor system has been designed and tested successfully in wind tunnel in open-loop actuation. The integral twist deformation of the blades is generated using active fiber composite actuators embedded in the composite blade construction. An analytical framework is developed to examine integrally twisted helicopter blades and their aeroelastic behavior during different flight conditions. This aeroelastic model stems from a three-dimensional electroelastic beam formulation with geometrical-exactness, and is coupled with finite-state dynamic inflow aerodynamics. A system identification methodology that assumes a linear periodic system is adopted to estimate the harmonic transfer function of the rotor system. A vibration minimizing controller is designed based on this result, which implements a classical disturbance rejection algorithm with some modifications. Using the established analytical framework, the closed-loop controller is numerically simulated and the hub vibratory load reduction capability is demonstrated.

• 대한기계학회논문집A
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• 제20권11호
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• pp.3549-3559
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• 1996

In this study, the effect of parameter and modal filter errors on the vibration control characteristics of flexible structures is analyzed for IMSC ( Independent Modal Space Control). If the control force is designed on the basis of the mathematical model with the parameter and modal filter errors, the closed-loop performance of the vibration control system will be degraded depending on the magnitude of the errors. An asymptotic stability condition of the system with parameter and modal filter errors has more significant effect on the stability condition of the system with parameter and modal filter errors has been drived using Lyapunov approach. It has been found that modal filter error has more significant effect on the stability of closed-loop system than parameter error does. The extent of the response deviation of the closed-loop system is also derived and evaluated using operator thchniques.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권6호
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• pp.1606-1626
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• 2012

This paper investigates the performance of an amplify-and-forward (AF) two-way relaying system with antenna correlation. The system consists of two multiple-antenna sources, which exchange information via the aid of a single-antenna relay. In particular, we derive the exact outage probability expression. Furthermore, we provide a simple, tight closed-form lower bound for the outage probability. Based on the lower bound, we obtain the closed-form asymptotic outage probability and the average symbol error rate expressions at high signal-to-noise ratio (SNR), which reveal the system's diversity order and coding gain with antenna correlation. To investigate the system's throughput performance with antenna correlation, we also derive a closed-form lower bound for the average sum-rate, which is quite tight from medium to high SNR regime. The analytical results readily enable us to obtain insight into the effect of antenna correlation on the system's performance. Extensive Monte Carlo simulations are conducted to verify the analytical results.

• 제어로봇시스템학회논문지
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• 제4권2호
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• pp.203-208
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• 1998

This paper presents an adaptive fuzzy controller using an neural network and adaptation algorithm. Reference-model following neuro-fuzzy controller(RMFNFC) is invesgated in order to overcome the difficulty of rule selecting and defects of the membership function in the general fuzzy logic controller(FLC). RMFNFC is developed to tune various parameter of the fuzzy controller which is used for the discrete nonlinear system control. RMFNFC is trained with the identification information and control closed loop error. A closed loop error is used for design criteria of a fuzzy controller which characterizes and quantize the control performance required in the overall control system. A control system is trained up the controller with the variation of the system obtained from the identifier and closed loop error. Numerical examples are presented to control of the discrete nonlinear system. Simulation results show the effectiveness of the proposed controller.

• 대한건축학회논문집:구조계
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• 제34권11호
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• pp.81-87
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• 2018

Among various types of geothermal heat pump systems, Vertical Closed-Loop Geothermal Heat Pump (VGSHP) has received increasing attention due to a variety of advantages such as the potential to be installed in a relatively small space and improved energy efficiency. In this research, the performance of VGSHP system coupled with heat storage tank was evaluated, by analyzing operational behavior of heat storage tank, the variations of heat pump energy performance due to the connection with heat storage tank, part load ratios characteristics of heat pump and the corresponding energy cost, compared to chiller and boiler based conventional system. The results of this study showed that the VGSHP system coupled with heat storage tank showed an energy saving effect of about 18% for cooling and about 73% for heating, and annual heating/cooling energy cost reduction of 43,000,000 KRW ($ 39,000), compared to the conventional air conditioning system. In addition, after considering both energy cost and initial investment cost including equipment, installation and auxiliary device expenses, payback period of approximately 11.8 years was required.

• 한국초전도ㆍ저온공학회논문지
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• 제8권1호
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• pp.59-64
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• 2006

A closed-loop cryogenic cooling system for high field magnets is presented. This design is motivated by our recent development of cooling system for 21 tesla Fourier Transform ion Cyclotron Resonance (FT-ICR) superconducting magnets without any replenishment of cryogen. The low temperature superconducting magnets are immersed in a subcooled 1.8 K bath, which is connected hydraulically to the 4.2 K reservoir through a narrow channel. Saturated liquid helium is cooled by Joule-Thomson heat exchanger and flows through the JT valve, isenthalpically dropping its pressure to approximately 1 6 kPa, corresponding saturation temperature of 1.8 K. Helium gas exhausted from pump is now recondensed by two-stage cryocooler located after vapor purify system. The amount of cryogenic Heat loads and required mass flow rate through closed-loop are estimated by a relevant heat transfer analysis, from which dimensions of JT heat exchanger and He II heat exchanger are determined. The detailed design of cryocooler heat exchanger for helium recondensing is performed. The effect of cryogenic loads, especially superfluid heat leak through the gap of weight load relief valve, on the dimensions of cryogenic system is also investigated.

• 방송공학회논문지
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• 제15권2호
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• pp.157-162
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• 2010

본 논문에서는 양��향 통신 시스템에서 폐회로 다중 안테나 송수신 (closed-loop multiple-input multiple-output) 기법을 사용하는 적응형 협동 다중 홉 중계 시스템을 제안한다. 중계기와 기지국 사이의 이동성이 낮기 때문에, 폐회로 다중 안테나 송수신 기법은 개회로 다중 안테나 송수신 기법보다 높은 다이버시티 이득을 얻을 수 있다. 이 때, 한 개 이상의 중계 터미널들은 기지국으로 전송을 공유하고 프리코딩 가중치 벡터를 피드백하기 위해 하나의 협동 그룹에 포함되어야 한다. 피드백 비트의 증가로 인한 전송량 감소를 최소화하기 위해 코드북 기반의 최대비 전송 기법을 사용하여 피드백 비트수를 제한한다. 기지국은 협동 중계 그룹 중에서 채널 상태가 가장 좋은 중계기를 선택하고, 프리코딩을 위한 인덱스 값을 중계기에 피드백한다. 이러한 중계 시스템을 위해 피드백 형태와 선택 프로토콜 시나리오를 제안하고, 모의실험을 통해 중계기 선택에 따른 성능을 확인한다.

• 한국전자파학회논문지
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• 제28권11호
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• pp.886-893
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• 2017

RCS 기술의 발달과 레이다 기술의 발달에 따라 바이스태틱, 멀티스태틱 레이다 시스템이 많이 사용되고 있다. 본 논문은 바이스태틱 MIMO 레이다 시스템의 수신신호 모델링 유도 과정을 보이고, ML 도래각 추정 알고리즘에 바이스태틱 신호를 적용했을 때의 성능 분석을 다룬다. ML 도래각 추정 알고리즘인 경우, 신호원의 개수에 따라 도래각 추정에 요구되는 탐색 차원 또한 증가하게 되어 많은 계산량을 요구한다. 해당 문제점을 해소하기 위해 본 논문은 해당 알고리즘의 추정오차를 closed-form 표현으로 유도함으로써 별도의 도래각 추정 없이 바이스태틱 환경의 수신신호에 대한 ML 알고리즘의 성능분석이 가능함을 보인다.

• 펄프종이기술
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• 제44권6호
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• pp.9-14
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• 2012

Currently a variety of efforts to conserve and restore the injured the Annal of the Joseon Dynasty are continued and many studies about the aging pathway of the beeswax-treated volume have being progressed. In this study, two chambers were set up to assess the influence of VOCs(Volatile Organic Compounds) generated in process of beeswax deterioration. One chamber was closed and the other was continuously ventilated in order to remove the VOCs. In results, the acid compounds of beeswax-treated Hanjis aged in closed chamber was more than that aged in ventilated chamber. The folding endurance of beeswax-treated Hanjis aged in closed chamber was lower than that aged in ventilated chamber. Accumulated acid compounds of beeswax-treated Hanji in closed chamber may cause accelerated aging and strength decrease. In conclusion, accumulated acid compounds can accelerate the aging of beeswax-treated Hanji and cause the severe deterioration of inside of beeswax-treated volume. Therefore, to preserve more safely beeswax-treated volumes of the Annals of the Joseon Dynasty, it is essential that VOCs emitted from beeswax-treated volume are ventilated.

• 한국기록관리학회지
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• 제20권3호
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• pp.55-76
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• 2020

우리나라 대부분의 의료기관이 전자의무기록을 도입하고 있지만, 의료기관이 폐업했을 경우의 기록물 관리 및 보존에 있어서 많은 맹점이 존재한다. 폐업 의료기관의 기록은 적법한 절차에 따라 체계적으로 관리될 필요가 있음에도 불구하고 보건소로 기록을 이관하는 폐업 의료기관의 수가 현저히 적고, 전자의무기록을 사용하는 의료기관마다 사용하는 시스템 및 서식이 상이하기 때문에 이관을 받는 보건소에서도 해당 기록을 열람조차 하지 못하는 경우가 많다. 또한, 보건소의 현실과 전자의무기록이라는 특수성에 부합한 관리기준 및 지침 또한 부재한 상황이다. 최근 폐업 의료기관의 의료기록에 대한 보건소의 보관책임 강화 법안이 통과함에 따라 본 연구에서는 관할 보건소의 효율적인 기록물 관리를 위한 방안 마련에 주목하였다. 이를 위해 관계 법령을 살펴보고 관리·보존이 미흡한 폐업 의료기관 전자의무기록 관리 현황을 파악하기 위한 문헌조사를 비롯한 정보공개청구 및 전화인터뷰 등의 조사를 실시하였으며, 그 문제점을 분석하여 제도적·기술적·행정적인 측면에서의 개선방안을 제안하였다.