• Journal of Wetlands Research
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• v.2 no.1
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• pp.49-58
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• 2000

The frequency analysis of annual maximum rainfall data and the derivation of probable rainfall intensity formula at Masan station are performed in this study. Based on the eight different rainfall duration data from 10 minutes to 24 hours, eight types of probability distribution (Gamma, Lognormal, Log-Pearson type III, GEV, Gumbel, Log-Gumbel, Weibull, and Wakeby distributions), three types of parameter estimation scheme (moment, maximum likelihood and probability weighted methods) and three types of goodness-of-fit test (${\chi}^2$, Kolmogorov-Smirnov and Cramer von Mises tests) were considered to find an appropriate probability distribution at Masan station. The Lognormal-2 distribution was selected and the probable rainfall intensity formula was derived by regression analysis. The derived formula can be used for estimating rainfall quantiles of the Masan vicinity areas with convenience and reliability in practice.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.693-696
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• 2003

Piezoelectric ceramics were made by a doctor blade methode and piezoelectric fans were fabricated by sandwiched a slim and long metal between two layers of ceramics. A maximum displacement of piezoelectric fan occurs in the resonance frequency of a long metal and the resonance frequency of them is in inverse proportion to the square of a length of metal. The piezoelectric fan made from a wide and thin piezoelectric ceramics($13{\times}0.2{\times}30mm^3$) showed a maximum displacement in all samples, and the maximum displacement was about 20mm in a commercial power (200V, 60Hz of sine wave).

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1534-1536
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• 1998

We designed and fabricated plate-type linear ultrasonic motor. It used multi-vibration mode, 1st Longitudinal and 4th Bending mode. To analyze vibration mode and find maximum displacement point, we simulated using FEM(Finite Element Method). The plate-type linear ultrasonic motor was fabricated by the simulation results. Also, to confirm application to card-forwarding device, frequency and load characteristics were measured. Its resonance frequency was 49.6 kHz, and its maximum speed was about 0.6m/s when no load. Also, its maximum efficiency was 1.2 % and in that time, speed and torque was 0.3 m/s and 0.7 mNm, respectively.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.6
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• pp.406-413
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• 2015

The piezoelectric coupling in piezoelectric vibration energy harvesters with load resistance induces electrical damping as well as increase in the system stiffness. Starting from analytically deriving the explicit relations through governing equations in the frequency domain, this work identifies the characteristics of the electrically induced damping mechanism and shows that the electrically induced damping serves as a structural hysteretic damping on condition that a piezoelectric vibration energy harvester is excited at its short-circuit resonant frequency and its load resistor is optimally impedance- matched at the same time. Finally, it is analytically verified that the equivalence of a mechanical and an electrically induced damping ratio is required for the maximum power generation at a load resistor, which was claimed in some literature.

• Journal of the Korea Society for Simulation
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• v.8 no.4
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• pp.25-31
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• 1999

To analyze the impulsive response of a motorcycle helmet, a simulation is performed using the finite element method. Based upon the simulation result, an equivalent one degree of freedom vibrational system is adapted, and transient impulsive responses are analysed to investigate the influence of engineering parameters such as damping, natural frequency, and impact velocity on the impulsive response of the helmet. Maximum gravitational acceleration reduces as the damping factor value increases. When the damping factor value is around 0.6 or larger, the maximum acceleration does not change. With respect to the natural frequency and the impact velocity, it increases linearly. The relationship between head injury criterion(HIC) and maximum gravitational acceleration is also presented. The scheme of this study is expected to be utilized to economize the design process of high quality motorcycle helmets.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.12
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• pp.573-578
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• 2003

In this study, new type of induction charging system for electrostatic spraying was manufactured and proposed to improve the electrical safety and charging efficiency. And parameters of proposed system to generate the maximum deposition current with electrical safety were selected and investigated. The selected parameters were frequency of square pulse and thickness of insulation material, outer diameter of device and thickness and positions of electrode. Charging quantity of water drop was measured by deposition current detected from sensing plate indirectly. The maximum deposition current for each parameter were 3.5[uA] at the frequency of 15[kHz] and thickness of 0.25[mm] insulating layer. And maximum deposition currents were 2.8[uA] and 3.0[uA] at 25[mm] outer diameter of charging device and 0.25[mm] thickness of electrode each. Effects of electrode position from spraying nozzle on deposition current was a little.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.656-659
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• 2001

In this paper a neural network controller for achieving maximum power tracking as well as output voltage regulation, for a wind energy conversion system(WECS) employing a permanent magnet synchronous generator, is proposed. The permanent magnet generator (PMG) supplies a dc load via a bridge rectifier and two buck-boost converters. Adjusting the switching frequency of the first buck-boost converter achieves maximum power tracking. Adjusting the switching frequency of the second buck-boost converter allows output voltage regulation. The on-times of the switching devices of the two converters are supplied by the developed neural network(NN). The effect of sudden changes in wind speed ,and/or in reference voltage on the performance of the NN controller are explored. Simulation results showed the possibility of achieving maximum power tracking and output voltage regulation simultaneously with the developed neural network controller. The results proved also the fast response and robustness of the proposed control system.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.6
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• pp.84-89
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• 2015

The thickness of a stable and economical frame has been designed in order to reduce costs. Therefore, this study applied structural analysis and vibration analysis based on a comparison of the thicknesses of frames. Four types of frames (1mm, 2mm, 3mm, and 5mm) were modeled on a bicycle frame that has a length of 842mm, a width of 100mm, and a height of 400.5mm, and all of these frames generated the stress and maximum deformation amount in the state and around the saddle. The maximum stress shown was 25.732 MPa in 1mm, 11.79 MPa in 2mm, and 8.2015 MPa in 3mm, and the maximum deformation amount shown was 0.063611mm in 1mm, 0.031978mm in 2mm, and 0.022319mm in 3mm. The natural frequency of the frame thicknesses 1mm, 2mm, and 3mm was estimated as within 270 Hz. The critical frequency of conditions of 3mm was the biggest at 118.1Hz compared with the 3-mm model; thus, 3mm was shown to have the most satisfactory resistance.

• 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.

• Applied Science and Convergence Technology
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• v.24 no.6
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• pp.224-227
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• 2015

Ferroelectric $Pb_2(Sc,Nb)O_6$ were prepared under two different sintering conditions using the oxide mixing method and the electrical properties were measured. The sintering conditions were $1350^{\circ}C$ for 25 minutes and $1400^{\circ}C$ for 20 minutes. EDX spectroscopy and XRD were used to determine the crystalline characteristic of the $Pb_2(Sc,Nb)O_6$ compositions Pyrochlore phase showed about 2% in all $Pb_2(Sc,Nb)O_6$ specimens. It expands the growth of crystals in samples sintered at $1400^{\circ}C$ than $1350^{\circ}C$, but all samples were the optimal crystallization. The temperature and frequency dependence of the complex dielectric constant and admittance were measured to analyze the electrical properties. The high dielectric constant of the specimens reflects the good stoichiometry and crystallization. The maximum value of the dielectric constant in the two specimens treated with sintering at $1350^{\circ}C$ and $1400^{\circ}C$ were more than 27,000, and the dielectric loss at room temperature is smaller than 0.05. The maximum dielectric constant decreased with increasing frequency, the transition temperature also increased in $Pb_2(Sc,Nb)O_6$ compositions. The admittance and susceptance values reach a peak at all temperatures, and the magnitude of the peak increases with increasing measuring temperature. Strong frequency dependent of maximum admittance, susceptance, dielectric constant and dielectric loss were observed.