• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.120-127
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• 1998

An Elliptic model for calculating the combined refraction/diffraction of monochromatic linear waves is developed, including a term which allows for the dissipation of wave energy. Conjugate gradient method is employed as a solution technique. Wave height variations are calculated for localized circular and rectangular dissipation areas. It is shown that the numerical results agree very well with analytical solution in the case of circular damping region. The localized dissipation area creates a shadow region of low wave energy and the recovery of wave height by diffraction occurs very slowly with distance behind the damping region.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2589-2592
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• 2003

In this paper, a robust mixed H$_2$/H$\_$$\infty$/ output feedback control method is applied to the design of loop filter for PLL carrier phase tracking. The proposed method successfully copes with large S-curve slope uncertainty and a significant decision delay in the closed-loop that may exist In modern receivers due to a convolutional decoder or an equalizer. The objective is to design an output feedback controller which minimizes the H$_2$performance while satisfying the H$\_$$\infty$/ performance to guarantee the gain margin and phase margin for linear time invariant(LTI) polytopic uncertain systems. LMIs based approach is given to solve this problem. We can verify the H$\_$$\infty$/ performance satisfaction and minimize the phase detector error through the simulation result.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.2
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• pp.261-265
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• 2014

This paper studies the problem of the sampled-data control for Lur'e system with nonlinearities. The nonlinearities are expressed as convex combinations of sector and slope bounds. It is assumed that the sampling periods are arbitrarily varying but bounded. By constructing a new augmented Lyapunov-Krasovskii functional which have an augmented quadratic form with states as well as the nonlinear function, the stabilizing sampled-data controller gains are obtained by solving a set of linear matrix inequalities. The effectiveness of the developed method is demonstrated by numerical simulations.

• Journal of IKEEE
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• v.2 no.2 s.3
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• pp.263-269
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• 1998

We use the slope bounded saturation nonlinear feedback element instead of relay to find ultimate gain and period of linear plant. Saturation nonlinear element reduces the high harmonics of plant output. The reduction of high harmonics improve the accuracy of describing function method used to find ultimate gain and period. We give a simple procedure to find ultimate gain and period with saturation nonlinear element. A PID controller design method with known time delay element is also given, which is very useful when oscillation is not occurred with nonlinear element.

• YAKHAK HOEJI
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• v.45 no.1
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• pp.29-33
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• 2001

A method for the determination of anionic drug, mefenamate with ion-selective electrode using Fe(II)-1,10-phenanthroline chelate as a counter ion was developed. Benzyl nitrophenyl ether (BNPE) plasticized membrane was more selective and sensitive than the other tested membranes. This membrane electrode exhibits a linear response for 10$^{-2}$ M~5 $\times$ 10$^{-5}$ M of mefenamic acid with a slope of -61.4 mV/dec. in borate buffer solutions (pH 9.0). Potentiometric selectivity measurements revealed negligible interferences from various organic and ionorganic anions. Direct potentiometry and potentiometric titration method of mefenamic acid in capsule preparations are presented and compared.

• Steel and Composite Structures
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• v.22 no.6
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• pp.1391-1415
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• 2016

Limit load of pressure bearing structures was reviewed in this article. By means of the finite element analysis, limit load of pressurized cylinder with nozzle was taken as an example. Stress classification method and Elastic-plastic finite element analysis combining with limit load determination methods were used to determine limit load of cylinder with nozzle. Comparison of limit load determined by different methods, the results indicated that limit load determined by linearization method was the smallest. Limit load determined by twice elastic slope criterion was the nearest than experimental results. Elastic-plastic finite element analysis had comparably computational precision, but required time consuming. And then the requirements of computer processing and storage capacity by power system became higher and higher. Most of criteria for limit load estimation included any human factors based on a certain substantive characteristics of experimental results. The reasonable criterion should be objective and operational.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.549-554
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• 2008

The recent trains are almost being operated by the mechanical propulsion force to drive the gear and wheel with the traction motor. However Magnetic Levitation Vehicle is differently operated. Magnetic Levitation Vehicle is applied with Linear Induction Motor(LIM) that has many advantage like to high capability of going up to slope, low noise, easy to control of speed. So domestic and many advanced countries are interested in Magnetic Levitation Vehicle and they have been studying about it continuously. Thus this paper is studied the LIM test method of static states and guess the optimum driving point by characteristic of static states for LIM. The test items are measurement of thrust force by changed air gap, measurement of thrust force and normal force by changed slip frequency etc.

• Current Optics and Photonics
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• v.5 no.3
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• pp.289-297
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• 2021

We describe a comb-mode resolving spectroscopic technique by direct time-domain phase correction of unstable interferograms obtained from loosely locked two femtosecond lasers. A low-cost continuous wave laser and conventional repetition rate stabilization method were exploited for locking carrier and envelope phase of interferograms, respectively. We intentionally set the servo control at low bandwidth, resulting in severe interferograms' fluctuation to demonstrate the capability of the proposed correction method. The envelope phase of each interferogram was estimated by a quadratic fit of carrier peaks to correct timing fluctuation of interferograms in the time domain. After envelope phase correction on individual interferograms, we successfully demonstrated 1 Hz linewidth of RF comb-mode over 200 GHz optical spectral-bandwidth with 10-times signal-to-noise ratio (SNR) enhancement compared to the spectrum without correction. Besides, the group delay difference between two femtosecond pulses is successfully estimated through a linear slope of phase information.

• The Journal of Engineering Geology
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• v.24 no.1
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• pp.101-110
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• 2014

This study presents the results of a regression analysis of the point-load strength ($I_{s(50)}$) and the uniaxial compressive strength (UCS) of granites in Korea. The regression was carried out for three cases using the least-squares method, reclassifying the granite samples based on their physical properties. The first regression analysis through the origin according to the weathering grade did not give a result with a sufficient degree of confidence, due to the small number of samples. However, the general trend of the correlation between UCS and $I_{s(50)}$according to weathering grade shows that the slope of the linear regression for weathered granite is steeper than that for fresh granite. The second analysis was a simple linear regression for all the granite samples using the least-squares method as well as a linear regression using the bootstrap resampling method in order to increase the confidence level and the accuracy of the regression results. The third regression considered the average strength of granite groups reclassified according to physical properties. These linear regression analyses yielded linear regression equations with slopes of 14 and small standard deviations being similar to values reported in previous studies on Korean granites, but whose intercept values range from 16 to 43 and have a larger standard deviation than those of the present study. In conclusion, it would be advisable to estimate UCS from $I_{s(50)}$, considering the error range derived from the deviation of the regression equations.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.8
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• pp.42-49
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• 2005

A new blockage correction method has been developed for the wall interference correction of closed test-section subsonic wind tunnels based on the nonlinear relationship between separation blockage and separation drag. This method can be applied continuously from the linear lift-slope region to the highly nonlinear post-stall region by on-line processing. The present method was validated by comparing the results with a classical method based on the test results of a bluff body and a measured-boundary-condition method. It was shown that the present method is in good agreement with the measured-boundary-condition method, enabling better wall corrections than the bluff body method in both near-stall and post-stall regions.