• Ocean Systems Engineering
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• v.3 no.3
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• pp.203-217
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• 2013

A PTO (power-take-off) mechanism by using relative heave motions between a floating buoy and its inner mass (magnet or amateur) is suggested. The inner power take-off system is characterized by a mass with linear stiffness and damping. A vertical truncated cylinder is selected as a buoy and a special station-keeping system is proposed to minimize pitch motions while not affecting heave motions. By numerical examples, it is seen that the maximum power can actually be obtained at the optimal spring and damper condition, as predicted by the developed WEC(wave energy converter) theory. Then, based on the developed theory, several design strategies are proposed to further enhance the maximum PTO, which includes the intentional mismatching among heave natural frequency of the buoy, natural frequency of the inner dynamic system, and peak frequency of input wave spectrum. By using the intentional mismatching strategy, the generated power is actually increased and the required damping value is significantly reduced, which is a big advantage in designing the proposed WEC with practical inner LEG (linear electric generator) system.

• Journal of Korea Society of Digital Industry and Information Management
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• v.12 no.4
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• pp.25-31
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• 2016

In this research, to analyze the concentration of heavy metal ions in water, we tried to find the measuring time at which the faradaic electric currents flowing by the pure oxidation-reduction reaction from the pushing up mercury electrode of the stripping scan square wave voltammetry(SV+SWV) methods system becomes larger than the capacitance electric current. In order to do this, a method for analyzing signals using FPGA has been designed and we conducted 120 experiments using it. As a result, when the frequency of the square wave is 40Hz, The valid potential-current signal was measured from 96.6667% to 96.7155% of the end of the pulse of the forward and reverse, and the optimal signal was measured at 96.6667%. In addition, the experiment was carried out 40 times by changing the pulse height of the square wave from 10Mv to 40Mv. As a result, at a size smaller than 40Mv, there is little change in the magnitude of the potential-current, and an invalid signal was generated when it is out of this size.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.835-838
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• 2002

A running high voltage equipments produce ultrasonic wave that has unique sound by the specific characteristics of the electricity. The generation of the ultrasonic wave is made by the electric transform like arcing, corona, and tracking so on. The mechanical losses and fatal human damages are happened by the electric failure of high voltage equipments. To prevent and diagnose the obstacle factors of the high voltage equipments, the measurement of the ultrasonic wave became to be prominent. However standardized data have been a deficient situation by now. This paper measures the ultrasonic wave coming from the real running transformer equipments and transforms it as an audio frequency. Measured data represents as frequency and time domain through the FFT(Fast Fourier Transform) transform. In conclusion, the purpose of this paper is to standardize the analyzed data.

• Ocean Systems Engineering
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• v.14 no.1
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• pp.17-52
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• 2024

In this paper, the authors explore the modeling and control of a point absorber wave energy converter, which is connected to the electric grid via a power converter that is based on a linear permanent magnet synchronous generator (LPMSG). The device utilizes a buoyant mechanism to convert the energy of ocean waves into electrical power, and the LPMSG-based power converter is utilized to change the variable frequency and voltage output from the wave energy converter to a fixed frequency and voltage suitable for the electric grid. The article concentrates on the creation of a predictive control system that regulates the speed, voltage, and current of the LPMSG, and the modeling of the system to simulate its behavior and optimize its design. The predictive model control is created to guarantee maximum energy output and stable grid connection, using Matlab Simulink to validate the proposed strategy, including control side generator and predictive current grid-side converter loops.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.6
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• pp.861-866
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• 2011

This paper described the hybrid power generation using ocean wave that consists of linear power generation system and vibrational power generation system. The linear power generation system is made up of the winding coil, the permanent magnet and it is performed stable generation regardless of the wave frequency using directly the ocean wave velocity. And the vibration power generation system consists of the winding coil, the permanent magnet and spring. When the vibration system natural frequency in the vibrational power generation system is tuned to the ocean wave frequency, the relative velocity of between the winding coil and the permanent magnet is faster than the velocity of ocean wave up and down motion, then we can obtain more the electric power. Therefore, in this paper, the proposed hybrid power generation using ocean wave have merits that obtaining the more electric energy in resonance frequency and carrying out stable generation even over the range of resonance frequency.

• Korean Journal of Food Science and Technology
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• v.39 no.5
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• pp.506-514
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• 2007

In this study, carrot juice was treated with high voltage pulsed electric fields (PEF) and the changes in its physical and chemical properties during storage at $4^{\circ}C$ and $25^{\circ}C$ were investigated. The sterility fur bacteria, yeast and mold in carrot juice increased with increasing electric field strength and treatment temperature. While yeast and mold were completely inactivated at 65kV/cm with a treatment time of $200{\mu}s$ in a continuous PEF treatment system, bacteria were reduced by four log cycles. The results also showed that square wave pulse treatment was more effective for inactivating microorganisms than exponential decay pulse, and this effect was more apparent for carrot juice of lower pH. Although we observed significant changes in physical and chemical properties such as soluble solid content, pH, acidity, color, and carotene retention when the PEF treated samples were stored at the ambient temperature $(20^{\circ}C)$, no significant physical and chemical changes were found at the cold storage temperature $(4^{\circ}C)$ during 28 days of storage. The results indicate that the PEF treated carrot juice is appropriate for commercial refrigerated storage.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.10a
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• pp.125-126
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• 2016

WAVE/DSRC 복합 통신 시스템은 기존 국내의 ITS 방식인 DSRC의 단점을 보완한 시스템이다. 본 논문에서는 V2I통신 고속 이동체의 링크 연결 지연 최소화를 위해 새로운 핸드오버 방식을 제안하였다.

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.161-164
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• 1989

When an electric (or a magnetic) line source is located near the surface, surface wave type field is generated and the energy associated with this field is guided very close to the impedance surface. In this paper, field strength is calculated by the exact modal and ray methods for a line source excited parallel plate waveguide. The surface wave contribution to the modal and ray solutions is anticipated very strong and must be included in both solutions.

• Korean Journal of Optics and Photonics
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• v.10 no.4
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• pp.294-300
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• 1999

The density matrix is solved more rigorously, compared with the third-order pertubation method used in the conventional theory, for a semiconductor laser amplifier. Then the coupled wave equations are derived to explain the wavelength conversion due to the spectral hole burning in the semiconductor optical amplifier. It is shown that our results can explain the effect of saturation of the population density on the electric polarization, which affects the four-wave mixing and wavelength conversion, better than the conventional theroy where the third-order pertubation is used.

• Journal of applied mathematics & informatics
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• v.41 no.4
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• pp.811-819
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• 2023

In this research we have used the definition of standard fractional vector cross product to obtain fractional curl and fractional field of a standing wave, a travelling wave, a transverse wave, a vector field in xy plane, a complex vector field and an electric field. Fractional curl and fractional field for a complex order are also discussed. We have supported the study with calculation of impedance at γ = 0, 0 < γ < 1, γ = 1. The formula discussed in this paper are useful for study of polarization, reflection, impedance, boundary conditions where fractional solutions have applications.