• 한국전자파학회논문지
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• 제29권4호
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• pp.285-289
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• 2018

본 논문에서는 지능적인 원거리 무선전력전송의 방식으로 시간 역전(time reversal) 기반 전파 집속 방법을 제시하였다. 시간 역전 기반의 무선전력전송은 복잡한 전파환경에서도 기기의 위치에 상관없이 전파를 선택적으로 집속하여 높은 peak 전력을 전달할 수 있다. 현실과 가까운 전파환경 시뮬레이션을 통하여 시간 역전 기반의 시 공간 전파 집속 현상을 검증하였고, 집속된 RF를 정류하여 전달된 DC 전압을 확인하였다. 또한 일반적인 협대역 신호(CW) 대비 시간 역전 신호의 peak 향상률과 정류 전력비를 확인한 결과, 최대 12 dB 향상된 peak 전력이 전송되었으며, 따라서 보다 높은 효율로 전력전송이 이루어짐을 확인하였다.

• 한국기계가공학회지
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• 제16권6호
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• pp.81-86
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• 2017

The high-pressure resin transfer molding (HP-RTM) process has a very effective for the mass production of carbon fiber reinforced plastic (CFRP) for light weight in the automotive industry. In developing robust equipment, new process and fast cure matrix systems reduces significantly the cycle time less than 5 minutes in recent years. This paper describes the cavity pressure, temperature and molding characteristics of the HP-RTM process. The HP-RTM mold was equipped with two cavity pressure sensors and three temperature sensors. The cavity pressure characteristics of the HP-RTM injection, pressurization, and curing processes were studied. This experiment was conducted with selected process parameters such as mold cap size, maximum press force, and injection volume. Consequently, this monitoring method provides correlations between the selected process parameters and final forming characteristics in this work.

• 대한전기학회논문지:시스템및제어부문D
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• 제52권2호
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• pp.107-111
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• 2003

In the power-line communication systems, there are many factors of noise and attenuation in the power-line channels, because they were designed for not the communication but the power transmission. Also the transfer function of the channels is highly changed with the topology and the load of the power-lines. To cope with these poor channel situation, channel modeling, one of the many studies in progress, is being studied hard. Channel modeling is essential to apply the active schemes to overcome the bad channel(e.g. modulation technique, channel coding, signal coupling & filtering, etc.) to the power-line communications. In this paper, we have realized the statistical model(this model is suggested as the channel modeling method for the power-line channels) that is combined the transfer function with the various noises. And we have compared and examined the results with the measured data. Also we have studied the plan which can effectively establish the channel data base for the channel information consisted of the parameters that are derived from this modeling, and we have studied the plan to utilize the data base.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.969-974
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• 2007

In this paper, a beamforming technique is introduced to measure the acoustic impedance at both normal and oblique incidence in a free field. The acoustic impedance is obtained by separating incident and reflected signals using the adaptive nulling method which is one of the various beamforming algorithms. To obtain better results, pressure vector commonly used in array signal processing is replaced with the transfer function vector between each microphone and the white Gaussian noise is suppressed by a wavelet shrinkage technique. The experiments conducted in a semi-anechoic room show that the proposed method is efficient and accurate in measuring the acoustic impedance of sound absorbing materials under a free field condition.

• 한국통신학회논문지
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• 제28권7A호
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• pp.520-528
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• 2003

본 논문에서는 다자간 화상회의 시스템에서 합성 입체 음향을 재현하는 방법과 음향반향제거 방법을 제안한다. 합성 입체 음향은 HRTF(head related transfer function)을 이용하여 구현하고 반향제거를 위하여 주변잡음에 대하여 강건한 적응 알고리즘을 제안한다. 제안하는 알고리즘은 SMAP(set-membership affine projection)을 변형한 것으로 적응필터의 계수를 갱신할 때 입력신호와 추정오차신호의 상호상관을 입력신호의 자기상관 행렬과 투영 차수를 곱한 추정오차신호 전력의 합으로 정규화한다. 제안하는 적응알고리즘은 SMAP 알고리즘과 비교하여 투영차수와 주변잡음에 대하여 강건한 특성을 갖는다. 컴퓨터 시뮬레이션을 통해 제안하는 합성 입체음향 반향제거기의 성능이 효과적으로 반향을 제거할 수 있음을 보인다.

• Korean Chemical Engineering Research
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• 제55권4호
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• pp.556-560
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• 2017

A hemoglobin/silver nanoparticle heterolayer was fabricated for bioelectronic device with electrochemical signal-enhancement effect. As a device element, a hemoglobin, the metalloprotein, contained the heme group that showed the redox property was introduced for charge storage element. For electron transfer facilitation, a silver nanoparticle was introduced for electrochemical signal facilitation, the hemoglobin was immobilized onto Au substrate using chemical linker 6-mercaptohexanoic acid (6-MHA). Then, the silver nanoparticle was immobilized onto fabricated hemoglobin/6-MHA heterolayers by layer-by-layer (LbL) method. The surface morphology and surface roughness of fabricated heterolayer were investigated by atomic force microscopy (AFM). The redox property of hemoglobin/silver nanoparticle heterolayer was investigated by a cyclic voltammetry (CV) experiment for obtaining an oxidation potential and reduction potential. Moreover, for the assessing charge storage function, a chronoamperometry (CA) experiment was conducted to hemoglobin/silver nanoparticle-modified heterolayer electrode using oxidation and reduction potentials, respectively. Based on the results, the fabricated hemoglobin/silver nanoparticle heterolayer showed that an increased charge storage effect compared to hemoglobin monolayer-modified electrode.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1998년도 추계학술대회
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• pp.96-97
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• 1998

3D TOF MR Angiography is able to obtain thinner slice thickness, higher SNR, therefore higher spatial resolution than 2D TOF MR Angiography. Since it uses longer TR than 2D TOF MRA to allow stronger in-flow effect, the background tissue may not be fully saturated. Thus background tissue signal can be further suppressed by MTS(Magnetization Transfer Saturation). Flow-compensation was accomplished by GMN(Gradient Moment Nulling), and tracking saturation was used to suppress vein signal. The different flow signal at the entry of the slab and output of the slab can be compensated by TONE(Tilted Optimized Non-saturating Excitation) RF pulse.

• 한국공작기계학회논문집
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• 제16권3호
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• pp.31-36
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• 2007

The excavator is complex machinery which has widely used in the construction site, deck of harbor and deep sea. The one of important issue of excavator system in recent is an automation of it in order to improve a working efficiency, a convenience working circumstance and work satisfaction. However, since there are large nonlinearities of control circuit, actuating cylinder, joiners of hydraulic units and changing loads etc., it is difficult to develope an automatic excavator system. Therefore, in this study, toy scale pneumatic excavator system is constructed and the remote control system is installed on it, before developing the automatic excavator system. In order to design the control system of the developed pneumatic excavator system, the transfer function is obtained using signal processing method and the controller gains of PID are decided based on CDM(coefficient diagram method). The obtained transfer function and the performance of the proposed control system is evaluated through experiments and computer simulation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.122-127
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• 2002

A frequency-domain PES estimation and its prediction method are proposed for the tightly-coupled servo/mechanical design of high-TPI HDD system above 100 kTPI. The major two disturbance energies which are related with mechanical vibrations inside of HDD are used to predict the drive-level PES, while considering closed-loop servo dynamics. One is the torque disturbance which mainly comes from aerodynamic excitation of HSA system and the other is the displacement disturbance from disk-spindle dynamics. In order to obtain the accurate error transfer function of closed-loop servo control, the plant model is measured by accurate experiment. The measured PES is compared with predicted one in terms of frequency-domain PES spectrum and its standard variation value. It is proved that the proposed frequency-domain PES estimation/prediction method is capable of predicting drive-level PES of high-TPI hard disk drive.

• 대한기계학회논문집A
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• 제21권11호
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• pp.1837-1843
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• 1997

This study experimentally demonstrates the use of active muffler attached to the automotive exhaust system to reduce exhaust noise. For improving the signal to noise ratio in the process of estimation of secondary path transfer functions, the on-line algorithm that conventional inverse modeling is combined with adaptive line enhancer is used as the control algorithm. Active muffler is designed that the primary noise and the control sound are propagated as a plane wave in the outlet. Therefore, the error microphone could be placed out of the tail pipe center of a high temperature and the radiation noise to the outside could be reduced in the whole area around the outlet. The control experiment for reducing exhaust noise with active muffler is implemented during run-up at no load. From the experimental results presented, compared with the conventional off-line method, the proposed on-line method is capable to acquire a reduction of exhaust noise above 5 dB in overall sound power level.