• ALGAE
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• 제25권2호
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• pp.89-97
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• 2010

To test the feasibility of using chlorophyll ${\alpha}$ fluorescence to assess the establishment success of seagrass transplants, photosynthetic characteristics of eelgrass Zostera marina transplants were measured using a Diving-pulsed amplitude modulation fluorometer in Jindong Bay on the southern coast of Korea. Maximum quantum yield ($F_v/F_m$), photosynthetic efficiency ($\alpha$), saturating irradiance ($E_k$) and maximum electron transport rate ($ETR_{max}$) of transplants and reference plants in a nearby transplant site were measured using the fluorometer for 5 months. Additionally, shoot morphology, individual shoot weight and productivity of transplants and reference plants were also monitored. Shoot height, leaf weight and productivity of transplants were significantly reduced during the first two or three months after transplantation compared to those of reference plants, and then increased to the levels of reference plants Characteristics of chlorophyll a fluorescence, including $F_v/F_m$, $\alpha$, $E_k$ and $ETR_{max}$ of transplants were also significantly reduced in the initial period, but recovered slightly sooner than shoot morphology or leaf productivity. These results indicated that after transplantation, Z. marina transplant photosynthesis recovered faster than shoot morphology, biomass or productivity. Thus, chlorophyll a fluorescence can be used as an indicator for early assessment of the status of eelgrass transplants without destructive sampling.

• Progress in Superconductivity
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• 제10권1호
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• pp.1-5
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• 2008

Magnetocardiography (MCG) is a non-contact, non-invasive, and harmless diagnostic tool to detect the abnormal electrical conductivities of the heart caused by the various coronary artery disease or cardiac muscular disease. The purpose of this study is to identify whether MCG signals and MCG parameter values vary depending on the location of sensor assembly. It will be an important reference for the standard measurement. Four healthy male subjects (33.3$\pm$6.3 years) participated in this study. Basal recording was made at 20 mm apart from the chest surface. All subjects were requested to take a regular breathe while MCG was taken. The gap between the chest surface and the bottom of the sensor assembly was 20, 40, 60, and 80 mm. Recording was made using 64 channel MCG system (Axial type, first order gradiometer) developed by Korea Research Institute of Standards and Science (KRISS). After resting for two minutes in a supine position on the bed in magnetically shielded room, MCG were recorded for 30 s. As the sensor location is getting away from the chest surface signal, the amplitude of R and T wave peak decreases to 70% (at 40 mm gap), 50% (at 60 mm), and 37% (at 80 mm) of the reference strength measured (y = $1.3903e^{-0.0169x}$, $R^2$ = 0.99; where y=amplitude remained after reduction, x=distance between chest surface and sensor location). The regression equations may be used as a good reference to calculate how much strength will be decreased by the distance. In MCG parameters, most values of parameters were decreased as the gap was increased. As an example, the current moment at T-wave peak reduced to 52% (at 40 mm gap), 33% (at 60 mm), and 19% (at 80 mm). However, the difference caused by the gap could be reduced by considering the distance when the MCG parameters were calculated. The study results can be used as a useful reference to design the baseline and the sensor location.

• 한국통신학회논문지
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• 제38C권6호
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• pp.531-539
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• 2013

Wi-Fi 기반 위치 추적 기술은 다양한 방법들이 제시되어 있으나 일반적으로 지정한 참조위치에서 측정한 신호세기 정보를 활용하는 핑거프린트 기법을 주로 이용한다. 그러나 핑거프린트 기법이 높은 해상도와 정밀도를 가지기 위해서는 다수의 참조위치를 필요로 하지만, 다수의 정보를 위해서는 많은 비용의 소모가 발생한다. 본 논문에서는 서비스 지역을 격자로 구분하고 가상의 참조위치를 바탕으로 신호 세기 모델을 만들어서 격자의 신호 세기정보를 예측하고 신뢰도를 부여하여 핑거프린트 맵을 생성한다. 이렇게 생성된 맵은, 위치 추정을 위해 입력된 신호 세기 리스트와 비교하여 추정하고자 하는 대상이 어떠한 격자에 있는지 비교하는데 사용한다. 제안하는 기법과 시스템의 성능을 평가하기 위해 $20m{\times}22m$의 실내 환경에서 기존의 핑거프린트 기법(RADAR)과 비교한 결과 제안하는 시스템을 이용할 때 위치 측정 에러가 감소하는 결과를 확인하였다. 그리고 실험 결과 기존의 방법에 비해 1.74미터의 에러가 감소한 것을 확인했다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 F
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• pp.1872-1875
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• 1998

In the industrial motor drive system, a shaft torsional vibration is often generated when a motor and a load are connected with a flexible shaft. This paper treats the vibration suppression control of such a system. Recently, there are new methods which estimate unknown state variables by using a reduced order observer and feedback these state variables by using a pole placement design method. But there is a trade-off between the fast command following property and the attenuation of disturbances and vibrations in these design methods. In this paper, the vibration suppression control of a two-mass system using a reference model is proposed. Because of using a reference model, the proposed control satisfy the fast command following property and the attenuation of disturbances and vibrations. Control parameter can be changed to maintain high system performance in control using a reference model. Experimental results show the validity of the proposed state feedback control using a reference model, and this controller is compared with the state feedback controller.

• Journal of Magnetics
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• 제18권4호
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• pp.422-427
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• 2013

The aim of this study was to investigate effects of the number of acquisitions (NEX) on signal-to-noise (SNR) and artifacts in SENSE parallel imaging of magnetic resonance imaging (MRI). 3.0T MR System, 8 Channel sensitivity encoding (SENSE) head coils were used along with an in-vivo phantom. Reference sequence of 3D fast field echo (FFE) was consisted of NEX values of 2, 4, 6, 8, 10 and 12. The T2 turbo spin echo (TSE) sequence used for exams achieved SENSE factors of 1.2, 1.5, 1.8, 2.0, 2.2, 2.5, 2.8, 3.0, 3.2, 3.5, 3.8 and 4.0. Exams were conducted five times for each SENSE factor to measure signal intensity of the object, the posterior phase-encode direction and frequency direction. And SNR was calculated using mean values. SENSE artifacts were identified as background signal intensity in the phase-encoded direction using MRIcro. It was found that SNR increased but SENSE artifacts reduced with NEX of 4, 8 and 12 when the NEX increased in reference scan. It is therefore concluded that image quality can be improved with NEX of 4, 8 and 12 for reference scanning.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1996년도 춘계공동학술대회논문집; 공군사관학교, 청주; 26-27 Apr. 1996
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• pp.341-345
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• 1996

We have developed the drawing and part information management system that could integrate drawing information with corresponding part information in design process. The modules developed include the drawing information management (DIM) and the part information management(PIM). DIM consist of processing drawing management, approved drawing management, disused drawing management, and drawing print management. PIM consist of new part management, option management, and part change management. Errors which may occur in the design process can be reduced by reference to part information directly. In addition, the number of parts can be reduced by minimizing the frequency of new parts generation through the systematic management.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
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• pp.153-156
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• 2012

Direct numerical simulations (DNSs) of ignition of lean primary reference fuel (PRF)/air mixtures under homogeneous charge compression ignition (HCCI) conditions are performed using 116-species reduced chemistry. The influence of variations in the initial temperature field, imposed by changing the variance of temperature, and the fuel composition on ignition of lean PRF/air mixtures is studied using the displacement speed analysis.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2020년도 전력전자학술대회
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• pp.106-108
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• 2020

This paper introduces a new pulse-width modulation (PWM) method to reduce common-mode voltages (CMVs) and compare its performance with other reduced CMV-PWM (RCMV-PWM) methods. To avoid the use of zero-vectors which cause high CMV peaks, the introduced method splits every reference vector into two vectors such that the peak-to-peak magnitude of CMV is reduced by one-third of conventional space-vector PWM (SVPWM). The performance of RCMV-PWMs altered by the modulation index are analyzed with simulation results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 심포지엄 논문집 정보 및 제어부문
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• pp.51-52
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• 2008

In this paper, we propose two control schemes. The first control scheme is an adaptive passivity-based excitation control which regulates the terminal voltage to its reference. This controller is obtained through two steps: firstly, a simple direct adaptive passivation controller is designed for the power system with parametric uncertainties; then a linear PI controller is applied to converge the terminal voltage to its reference. The second control scheme is a linear governor control which consists of the frequency and the mechanical power. It is shown that the internal dynamics are locally stable with controllable damping. In the end, the boundness of all electrical variables, the frequency, the mechanical power, and the convergence of the terminal voltage to its reference can be achieved by these control schemes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.265-267
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• 2000

A method to compute the reactive powers of the added buses by the decoupled UPFC model for the optimal voltage profile is presented, by which the voltage magnitudes of PQ buses can get closer to the reference value(usually one p.u.). The performance index for assessing how much the voltage magnitude is closer to the reference value is defined as the squared sum of the present voltage minus the reference voltage multiplied by the weighting number associated with the relative importance of the buses. Numerical example in a 10-unit 39-bus power system with 2 UPFC's shows that the performance index can be very much reduced by operating multi UPFC's with the reactive powers for the optimal voltage profile proposed in this paper.