• Design & Manufacturing
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• v.15 no.2
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• pp.56-62
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• 2021

In this study, design technology of a non-mechanical flow meter using fluidic oscillation generated during the fluid flow in the chamber was investigated. To with respect to design a splitter, which is the most important factor in fluid oscillation, a transient flow simulation analysis was performed for three types of shapes and changes in inlet flow velocity. The oscillation characteristics with respect to the time in each case were compared, and it was confirmed that the SM03 model was the best among the presented models. In addition, the FFT analysis of the fluid oscillation results for the SM03 model was used to obtain a linear correlation between the flow velocity change and the maximum frequency, and a frequency of 20.957 (Hz/m/s) per unit flow velocity was obtained. Finally, injection molding simulation and molding experiment of the chamber with the designed splitter were performed.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.760-765
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• 1993

A multivariable learning control is designed in frequency domain. A general to of feedback assisted learning scheme is considered and an inverse model based learning algorithm is derived through convergence analysis in frequency domain. Performance of the proposed control method is evaluated through numerical simulation.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.259-262
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• 1999

This paper presents the design of highly efficient one-chip CMOS DC/DC converter. The converter operates at the switching frequency of 1MHz for reducing the size of passive elements. And use the zero voltage switching(ZVS) for minimizing switching loss at high frequency. The simulation shows that the circuit can achieve a 95% efficiency while delivering a load of 1W at 2V output.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.8
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• pp.52-59
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• 1998

New types of PFD (phase-frequency detector) are proposed with reset time and propagation delay reduced. The perfomrance of our proposed PFDs are confirmed by SPICE simulation with 0.8.mu.m CMOS process parameter. As a result of simulation, the reset time of PFDs are 0.32 nsec and 0.030 nsec in capture-process. The proposed PFDs can be used in hihg-speed phase-licked loop (PLL).

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.365.2-365
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• 2002

The flow field around a symmetrical airfoil in a uniform flow under the generation of noise was studied by experiments and numerical simulation. The experiments are conducted by visualizing the surface flow over the airfoil with a shear-sensitive liquid-crystal coating and by measuring the instantaneous velocity field around the trailing edge of the airfoil. The numerical simulation was carried out by LES. (omitted)

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.8
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• pp.702-710
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• 2007

Direct numerical simulation (DNS) is performed to investigate suppressed wake transition and occurrence of lock-on in the wake of a circular cylinder disturbed by sinusoidal perturbation at the Reynolds number of 220 (A-mode instability regime). The sinusoidal perturbation, of which the frequency is near twice the natural shedding frequency, is superimposed on the free stream velocity. It is shown that the wake transition behind the circular cylinder can be suppressed due to the perturbation of the free stream velocity. This change causes a jump in the Strouhal number from the value corresponding to A-mode instability regime to the value corresponding to retarded wake transition regime (extrapolated from laminar shedding regime) in the Strouhal-Reynolds number relationship. As a result, vortex shedding frequency is locked on the perturbation frequency depending not on the natural shedding frequency but on the modified shedding frequency.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.593-598
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• 2005

At-site analysis is not appropriate if the record length is shorter than target return period T. If the record length is longer than 27 years, then at-site analysis may be sufficient(Institute of Hydrology, 1999). However, in such a case, regional frequency analysis is recommended for purpose of comparison. Record lengths of annual maximum rainfall data in Korea are usually shorter than 50 years. It is therefore essential to apply regional frequency analysis for estimating rainfall quantiles of more than 100 years return period. In this research, regional rainfall frequency analysis is performed for hourly rainfall data of South Korea. Homogeneous regions are idntified by clusgter analysis which is a standard method of statistical multivariate analysis for dividing a data set into groups. An appropriate distribution is chosen by goodness-of-fit test. GLO is found to be an appropriate distribution as a result of goodness-of-fit measure (Hosking & Wallis, 1997). Simulation experiments are performed to check the performance of frequency analysis techniques. The effects of discordant sites on quantiles are considered.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1752-1758
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• 2015

This paper presents partial discharge localization in stator winding of generators using multi-conductor transmission line (MTL) and RLC ladder network models. The high-voltage (HV) winding of a 6kV/250kW generator has been modeled by MATLAB software. The simulation results of the MTL and the RLC ladder network models have been evaluated with the measurements results in the frequency domain by applying of the Pearson’s correlation coefficients. Two PD generated calibrator signals in kHz and MHz frequency range were injected into different points of generator winding and the signals simulated/measured at the both ends of the winding. For partial discharge localization in stator winding of generators is necessary to calculate the frequency spectrum of the PD current signals and then estimate the poles of the system from the calculated frequency spectrum. Finally, the location of PD can be estimated. This theory applied for the above generator and the simulation/measured results show the good correlation for PD Location for RLC ladder network and MTL models in the frequency range of kHz (10kHz<f<1MHz) and MHz (1MHz<f<5MHz) respectively.

• Journal of the Korean Society of Safety
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• v.33 no.5
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• pp.127-133
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• 2018

The Saemangeum master plan includes dredging and waterproofing materials, construction projects that can change the hydraulic characteristics of the Saemangeum and Mangyeong and Dongjin River basins. In this study, the river safety of 2030 when the Saemangeum master plan was completed for 100 year frequency, 500 year frequency and 100 year frequency applied RCP 8.5 scenario was examined using Delft3D. As a result of the analysis, it was confirmed that there was no overflowing point at the 100 year frequency, but the difference between the flood level and the river bank elevation was relatively small at the curved and river joint part. At the 100-year frequency with the 500-year frequency and the RCP 8.5 scenario, the possibility of overflowing at several locations was confirmed. The possibility of river bed loss due to fast velocity appears in the upstream part of Mankyung River and it is necessary to monitor the safety of hydraulic structures continuously. In addition, it is expected that the expansion of the area showing the characteristics of the lake due to dredging will affect the sediment mechanism and water quality, so detailed and diverse studies will be needed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.11
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• pp.1033-1040
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• 2012

Recently, several researches are focused on the frequency sharing and the liberalization of frequency use for utilizing the limited frequency resources efficiently. In military, as Network Centric Warfare(NCW), which requires significant mutual operability of battle elements and real-time operation speed, has come to the fore front as an important aspect of modern warfare, the methods to manage limited frequency resources in wireless communications environment efficiently has been studied and utilized. In this paper, we propose a Spectrum COP(Common Operation Picture) design suitable for the battlefields of air force. To construct the Spectrum COP of Air Force, we analyze the requirements and design the frequency management system by using EA(Enterprise Architecture) Framework. The simulation results of the proposed design proved the effectiveness by using EADSIM(Extended Air Defense Simulation) of Air Force.