• 한국분말재료학회지
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• 제8권2호
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• pp.131-135
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• 2001

The ferroelectric properties of barium titanate strongly depend on its microstructure, in particular, grain size and distribution. During sintering, $BaTiO_3$ usually exhibits abnormal grain growth, which deteriorates considerably the ferroelectric properties. A typical technique to suppress the abnormal grain growth is the addition of dopants. Dopant addition, however, affects the ferroelectric properties and thus limits the application of $BaTiO_3$. Here, we report a simple but novel technique to prevent the abnormal grain growth of $BaTiO_3$ and to overcome the limitation of dopant use. The technique consists of stepwise sintering in a reducing atmosphere and in an oxidizing atmosphere. The materials prepared by the present technique exhibit uniform grain size and high dielectric properties. The technique should provide opportunities of having $BaTiO_3$-based materials with superior ferroelectric properties.

• 한국군사과학기술학회지
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• 제16권3호
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• pp.382-389
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• 2013

In anti-jamming GPS receiver, adaptive signal processing techniques in which the radiation pattern of adaptive array antenna of elements may be adaptively changed used to reject interference, clutter, and jamming signals. In this paper, I describes adaptive signal processing technique using the sample matrix inversion(SMI) algorithm. This adaptive signal processing technique can be applied effectively to wideband/narrowband anti-jamming GPS receiver because it does not consider the satellite signal directions and GPS signal power level exists below the thermal noise. I also analyzed the effects of covariance matrix sample size and diagonal loading technique on the system performance of five-element circular array antenna. To attain near optimum performance, more samples required for calculation covariance matrix. Diagonal loading technique reduces the system nulling capability against low-power jamming signals, but this technique improves robustness of adaptive array antenna.

• Journal of the Korean Wood Science and Technology
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• 제24권2호
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• pp.1-6
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• 1996

This study was performed to investigate the feasibility of using sonic stress-wave technique in the longitudinal direction for the assessment of incipient decay of radiata pine wood. Decayed bending specimens by Tyromyces palustris and Gloeophyllum trabeum for varoious periods were tested nondestructively using stress-wave technique in the longitudinal direction and destructively. Decay detection, quantitative assessment of decay, and the prediction of residual strength of decayed wood with less than five percent weight loss can be feasible using stress-wave parameters (wave velocity, wave impedance, stress-wave elasticity) measured by stress-wave technique in the longitudinal direction and their percent reduction due to decay.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.503-503
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• 2000

This paper presents the design technique of the using of PlI, PID and PIDA Controllers in order to achieve the desired transient and steady state responses. The merit of the proposed technique is any tuning method is not being required. By using of the forward controller, so that all given specifications to be designed can be obtained via the root locus approach.

• Journal of Power Electronics
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• 제17권6호
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• pp.1600-1610
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• 2017

We propose maximum power extraction from a rooftop solar photovoltaic (PV) array during partial shading conditions. Partial shading is unavoidable during power extraction from rooftop PV systems due to nearby tall buildings (construction of additional floors) and trees (growth of trees). Many reconfiguration techniques can be used to extract maximum power in partial shading conditions, but in several cases, the real maximum power output is not achieved. In this study, a new switched PV technique is proposed to enhance the power output. The proposed technique is simple to use and more cost effective than other reconfiguration techniques. Therefore, it is suitable for rooftop applications. The power output of the proposed technique is compared with that of existing techniques with similar shading patterns. Eight panels with ratings of 250 watts (2 kW) each are used for testing. MATLAB simulation and hardware verification are done for the proposed and existing techniques. The proposed technique is implemented on a $4{\times}2$ PV array, although it can be extended to a number of arrays.

• 한국환경복원기술학회지
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• 제13권1호
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• pp.112-120
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• 2010

This study was carried out to develop the environmental friendly restoration technique for various disturbed slopes using native plants seed chips. As the result of the separated seeding using the developed seed chips of native plant combination, average germination rate and survival rate of trees, shrubs, and herbs were higher than those of the direct seeding, as 79~70%, 83~73%, and 59~53% or so, respectively. Also, the germination rates and the survival rates of trees, shrubs, and herbs in the separated seeding by the native plants seed chips were 10~15 times higher than those of the direct seeding. Numbers of plants survived were at least 10 times of that of the simple seeding. The native plants seed chip technique is more efficient in soil slopes compared with stone slopes. The application of the native plants seed chip technique makes the restoration stabilized through the herbs dominant vegetation to the woody dominant 1 within 3 years, and the Landscapes also changed from herbs to variously combined herbs and woody. The technique using native plants seed chips that can be applicable to various disturbed slops is more efficient than conventional restoration techniques in the respect of economics and landscape.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.430-430
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• 2012

The surface recombination velocity of the silicon solar cell could be reduced by passivation with insulating layers such as $SiO_2$, SiNx, $Al_2O_3$, a-Si. Especially, the aluminium oxide has advantages over other materials at rear surface, because negative fixed charge via Al vacancy has an additional back surface field effect (BSF). It can increase the lifetime of the hole carrier in p-type silicon. The aluminium oxide thin film layer is usually deposited by atomic layer deposition (ALD) technique, which is expensive and has low deposition rate. In this study, ICP-assisted reactive magnetron sputtering technique was adopted to overcome drawbacks of ALD technique. In addition, it has been known that by annealing aluminium oxide layer in nitrogen atmosphere, the negative fixed charge effect could be further improved. By using ICP-assisted reactive magnetron sputtering technique, oxygen to nitrogen ratio could be precisely controlled. Fabricated aluminium oxy-nitride (AlON) layer on silicon wafers were analyzed by x-ray photoelectron spectroscopy (XPS) to investigate the atomic concentration ratio and chemical states. The electrical properties of Al/($Al_2O_3$ or $SiO_2/Al_2O_3$)/Si (MIS) devices were characterized by the C-V measurement technique using HP 4284A. The detailed characteristics of the AlON passivation layer will be shown and discussed.

• Journal of Power Electronics
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• 제12권1호
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• pp.88-97
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• 2012

This paper presents a method for the digital control of a high power factor AC/DC converter employing the power balance control technique to achieve a fast response of the output voltage control. To avoid the effects of an output voltage ripple in the voltage control loop, the average output voltage is sampled and used as a feedback signal for the output voltage controller. The proposed control technique was verified by simulations using MATLAB/Simulink and its implementation was realized by a dsPIC30F4011 digital signal processor to control a CUK topology AC/DC converter with a 48V output voltage and a 250 W output power. The experimental results agree with the simulation results. The proposed control technique achieves a fast transient response with a lower line current distortion than is achieved when using a conventional proportional-integral controller and the power balance control technique with the conventional sampling method.

• 한국군사과학기술학회지
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• 제19권5호
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• pp.598-605
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• 2016

One of the effective methods for angular deception against monopulse radar is a cross eye technique. The typical cross eye technique can cause significant angular errors to monopulse radar by using two transceivers which transmit the signals with opposite phases. However, typical cross eye systems have high complexity of implementation because two transceivers should be installed with enough distance on the platform. In this paper, we propose a new cross eye technique with single transceiver based on the multipath effect. Then, angular deception performance of the proposed technique is analyzed.

• Journal of Power Electronics
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• 제12권6호
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• pp.851-858
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• 2012

This paper presents resonant inverter tuning for current source parallel resonant induction heating systems based on a new self oscillating switching technique. The phase error is suppressed in a wide range of operating frequencies in comparison with Phase Locked Loop (PLL) techniques. The proposed switching method has the capability of tuning under fast changes in the resonant frequency. According to this switching method, a multi-frequency induction heating (IH) system is proposed by using a single inverter. In comparison with multi-level inverter based IH systems, the advantages of this technique are its simple structure, better transients and wide range of operating frequencies. A laboratory prototype was built with an operating frequency of 35 kHz to 55 kHz and 300 W of output power. The performance of the IH system shows the validity of the new switching technique.