• Journal of Power System Engineering
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• v.10 no.4
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• pp.71-77
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• 2006

This study introduces the seismic qualification of safety related equipments for nuclear power plants to verify the possibility of resonance in regard to the operating speed and the structural integrity due to external piping nozzle loads as well as seismic dynamic loads using El-Centro earthquake, which was occurred in the 1940's previously. As a first step, it is necessary to investigate the natural frequency of the vertical mixed flow pump in order to determine whether static or dynamic equipment comparing with seismic cut-off frequency, 33hz. Also the normal mode analysis was carried out with the introduction of seismic redesign straint at the middle of vertical pump to increase the natural frequency. In terms of structural integrity, the application of static analysis with normal, upset and faulted nozzle loads event was presented for the comparison of material allowable stress. Also the dynamic analysis was performed to show the design adequacy through the application to the case of El-Centro earthquake.

• Current Optics and Photonics
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• v.5 no.2
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• pp.141-146
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• 2021

We have evaluated the suppression effect of atmospheric-turbulence-induced optical scintillation in terrestrial free-space optical (FSO) communication systems using a gain-saturated erbium-doped fiber amplifier (EDFA). The variation of EDFA output signal power has been measured with different amounts of gain saturation and modulation indices of the optical input signal. From the measured results, we have found that the peak-to-peak power variation was decreased drastically below 2 kHz of modulation frequency, in both 3-dB and 6-dB gain compression cases. Then, the power spectral density (PSD) of optical scintillation has been calculated with Butterworth-type transfer function. In the calculation, different levels of atmospheric-turbulence-induced optical scintillation have been taken into account with different values of the Butterworth cut-off frequency. Finally, the suppression effect of optical scintillation has been estimated with the measured frequency response of the EDFA and the calculated PSD of the optical scintillation. From our estimated results, the atmospheric-turbulence-induced optical scintillation could be suppressed efficiently, as long as the EDFA were operated in a deeply gain-saturated region.

• Proceedings of the IEEK Conference
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• 2000.11b
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• pp.249-252
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• 2000

A new Smart rower IC's based on the Partial SOI technology was designed for such applications as mobile communication systems, high-speed HDD systems etc. A new methodology of integrating a 0.8${\mu}{\textrm}{m}$ BiCMOS compatible Smart Power technology, high voltage bipolar device, high speed SAVEN bipolar device, LDD NMOSFET and a new LDMOSFET based on the Partial SOI technology is presented in this paper. The high voltage bipolar device has a breakdown voltage of 40V for the output stage of analog circuit. The optimized Partial SOI LDMOSFET has an off-state breakdown voltage of 75 V and a specific on- resistance of 0.249mΩ.$\textrm{cm}^2$ with the drift region length of 3.5${\mu}{\textrm}{m}$. The high-speed SAVEN bipolar device shows cut-off frequency of about 21㎓. The simulator DIOS and DESSIS has been used to get these results.

• Korean Journal of Optics and Photonics
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• v.26 no.3
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• pp.162-167
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• 2015

In this paper, we developed a MTF (Modulation Transfer Function) measurement system using a knife-edge scanning method for infrared optics. It consists of an objective part to generate the target image, a collimator to make the beam parallel, and a detector to analyze the image. We used a tungsten filament as the light source and MCT (Mercury Cadmium Telluride) to detect the mid-infrared(wavelength $3-5{\mu}m$) image. We measured the MTF of a standard lens (f=5, material ZnSe) to test this instrument and compared the result to the theoretical value calculated using the ZEMAX commercial software. It was found that the difference was within ${\pm}0.035$ at the cut-off frequency (50 1/mm). Also, we calculated the A-type measurement uncertainty to check the reliability of the measurement. The result showed only 0.002 at 20 1/mm in spatial frequency, which means very little variation in the MTF measurement under the same conditions.

• Journal of Advanced Navigation Technology
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• v.13 no.1
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• pp.41-47
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• 2009

In this paper, a band pass filter with a rejection band is proposed for UWB(Ultra Wide Band) communication system. First, low pass filter accessed cut off frequency of 10.2 GHz was designed using structure stepped impedance. And high pass filter accessed cut of frequency of 3.2 GHz was designed using parallel short-stub. There was implemented composite connection of designed low pass filter and high pass filter. The relative dielectric constant, the height, the loss tangent of the PCB substrate were ${\varepsilon}_r$=2.2, h=0.508 mm and loss tangent = 0.0009 respectively. The fabricated band pass filter shows a compact size of 3 cm. The fabricated band pass filter was characterized using 37169A VNA(Vector Network Analyzer). And measured result were obtained 7.5 GHz of bandwidth and -10 dB of return loss and -3 dB of insertion loss from pass band. The result of the research can be used for the UWB communications and MIC/MMIC, RFIC system.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.5
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• pp.315-320
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• 2000

This paper presents the fabrication and test of a micropump with an electromagnetic actuator and a pair of aluminum flap valves. The actuator consists of a solenoid coil, a permanent magnet and an actuator diaphragm. The actuator diaphragm is fabricated by the spin coating of silicone rubber. The valve are passive ones and are fabricated by micromachining. The deflection of the fabricated actuator diaphragm is measured with a laser vibrometer. The deflection of the actuator diaphragm is proportional to the input current. The measured deflection of the fabricated diaphragm is $400 \mum$,/TEX> when the input is 118 mApp, and the cut-off frequency is 50 Hz. The maximum flow rate of the fabricated micropump with the electromagnetic actuator is about 5$0 \muell/min$ at 5 Hz when the input current and the duty ratio of the square was are 118 mApp and 50%, respectively.

• ETRI Journal
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• v.19 no.2
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• pp.48-58
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• 1997

Using high quality high-$T_c$ superconducting (HTS) YBCO thin films, we designed and fabricated 3-pole, 5-pole, and 7-pole lowpass filters consisting of microstrip transmission lines and open-stub lines. We measured the microwave response of the filters in the temperature range of T=85 K to 27 K. AtT=30 K, the observed inband insertion loss was 0.14dB and 0.02dB for the 5-pole and 7-pole filters, respectively. The cut-off frequency was 4.7 GHz for the 5-pole filter and 7.9GHz for the 7-pole filter. To the authors' knowledge, the measured inband insertion losses are the best values reported so far for the open-stub line type HTS multipole lowpass filters. The skirt property of the 5-pole filter showed a large improvement over that of the 3-pole filter as predicted from the simulation. We found that, to obtain a stable performance, the HTS multipole lowpass filters should be operated at the temperatures between 60% and 70% of $T_c$.

• ETRI Journal
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• v.35 no.3
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• pp.538-541
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• 2013

A compact microstrip lowpass filter (LPF) with an elliptic function response is proposed. A high equivalent capacitance and inductance between the structures of the resonator result in the sharp transition band of 0.04 GHz from 4 GHz to 4.04 GHz with an attenuation level of -3 dB and -20 dB, respectively. To improve the LPF rejection band, multiple open stubs are connected to the proposed resonator. A filter with a 3-dB cut-off frequency at 4 GHz is designed, fabricated, and measured, and agreement between the measured and simulated results is achieved. The results show that a stopband bandwidth of 131% with a suppression level better than -20 dB is obtained while achieving a compact size with a wide stopband.

• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1469-1478
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• 2014

Use of acetonitrile in electrolytes promotes better operation of supercapacitors. Recent efforts show that electrolytes containing acetonitrile can also function in a wide range of operating temperatures. Therefore, this paper addresses the dielectric relaxation processes, structure and dynamic properties of the bulk acetonitrile at various temperatures. Systems of acetonitrile were modeled using canonical ensemble and simulated by employing Molecular Dynamics method. Results show that interactions among the molecules were correlated within a cut-off radius while parallel and anti-parallel arrangements are observed beyond this radius at relatively high and low temperatures respectively. Furthermore, effects of C-C-N and C-H bending modes were greatly appreciated on the power spectral density of time rate change of dipole-dipole correlations whereas frequency shifts were observed on all modes at the lowest temperature under consideration. Linear variations with temperature were depicted for reorientation times and self-diffusion coefficients. Shear viscosity was also computed with a good accuracy within a certain range of the temperature as well.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.82-85
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• 2002

A compact rail to rail CMOS voltage follower is presented. The circuit is based on the symmetrical class AB voltage follower and can operate under supply voltages of ${\pm}$ 1.5 V. The proposed circuit has power dissipation of 5.2㎽ under quiescent condition and can drive ${\pm}$1.25 V to 250$\Omega$ load with a total harmonic distortion of less than 0.5 percent and cut off frequency of 237 ㎒. Although simple, the proposed circuit enables the output transistors to drive load efficiently.