• Journal of Ocean Engineering and Technology
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• v.20 no.6 s.73
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• pp.7-17
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• 2006

Depth and heading control of an AUV are considered to follow the predetermined depth and heading angle. The proposed control algorithm is designed. based on a sliding mode control using estimated hydrodynamic coefficients. The hydrodynamic coefficients are estimated with conventional nonlinear observer techniques, such as sliding mode observer and extended Kalman filter. By using the estimated coefficients, a sliding mode controller is constructed for the combined diving and steering maneuver. The simulation results of the proposed control system are compared with those of control system with true coefficients. This paper demonstrates the proposed control system, discusses the mechanisms that make the system stable and follows the desired depth and heading angle, accurately, in the presence of parameter uncertainty.

• Journal of IKEEE
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• v.3 no.2 s.5
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• pp.285-294
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• 1999

This paper presents a method for the generation of GRM coefncients over GF(3) by using a comparison of polarity. In general production method to GRM coefficients over GF(3) is searching for pn different polarity of an n-variable and from these optimal function according to the maximum number of zero coefficients is selected. This paper presents a method for the generation of GRM coefficients by means of compare to the number of zero coefficients without constructing the whole polarity GRM coefficients.

• Nuclear Engineering and Technology
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• v.29 no.4
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• pp.291-298
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• 1997

In advanced nuclear reactors, the passive containment cooling has been suggested to enhance the safety. The passive cooling has two mechanisms, air natural convection and oater cooling with evaporation. To confirm the coolability of PCCS, many works have been performed experimentally and numerically. In this study, the water cooling test was performed to obtain the evaporative heat transfer coefficients in a scaled don segment type PCCS facility which have same configuration with AP600 prototype containment. Air-steam mixture temperature and velocity, relative humidity and well heat flux are measured. The local steam mass flow rates through the vertical plate part of the facility are calculated from the measured data to obtain evaporative heat transfer coefficients. The measured evaporative heat transfer coefficients are compared with an analytical model which use a mass transfer coefficients. From the comparison, the predicted coefficients show good agreement with experimental data however, some discrepancies exist when the effect of wave motion is not considered. Finally, a new correlation on evaporative heat transfer coefficients are developed using the experimental values.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1286-1291
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• 2000

A new electro-rheological squeeze film damper (ER SFD) has been sealed with slotted piston rings which have electrodes at the inside of the constant gap. The slotted ER SFD can prevent the problem of electric discharge which might be occurred in the previous configuration of an ER SFD. The current paper presents the extraction of linearized dynamic coefficients within small orbit where these coefficients are controlled by the application of electric strength. Test rig has been modified to isolate the damper section for dynamic coefficient extraction. The results show that rotordynamic coefficients, damping and inertia terms, increase with increasing supply voltages, while stiffness coefficients decrease with increasing supply voltages. Rotating speed of rigid Shaft does not affect these coefficients.

• Proceedings of the IEEK Conference
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• 2003.07e
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• pp.1875-1878
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• 2003

This paper Proposes a wavelet-based video compression method to improve compressed images using modification of wavelet coefficients. In conventional wavelet-based compression methods, bigger coefficients are transmitted early according to the significance of the coefficients. In this reason, when some coefficients which have more significance but are not bigger are not transmitted, image degradation occurs. The Proposed method considered two human visual characteristics. First, human eyes are more sensitive to the change of middle frequency which represents abrupt change of brightness than that of high frequency which expresses fine region. Second, human eyes are more dull to color component than luminance respectively. By adjusting the coefficients of wavelet transformed signals and allocating more bits for compression to the luminance signal, higher compression could be achieved.

• Journal of applied mathematics & informatics
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• v.18 no.1_2
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• pp.301-310
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• 2005

The coefficients of the Rudin-Shapiro polynomials are $\pm1$. In this paper we first replace-1 coefficient by 0 which on that case the structure of the coefficients will be on base 2. Then using the results obtained for the numbers on base 2, we introduce a quite fast algorithm to calculate the autocorrelation coefficients. Main facts: Regardless of frequencies, finding the autocorrelations of those polynomials on which their coefficients lie in the unit disk has been a telecommunication's demand. The Rudin-Shapiro polynomials have a very special form of coefficients that allow us to use 'Machine language' for evaluating these values.

• Journal of Biomedical Engineering Research
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• v.11 no.1
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• pp.121-130
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• 1990

In this study, the coefficients of ultrasound attenuation for human liver were determined in 6 normal humans and in 38 patients with diffuse liver disease. The coefficients with linear frequency dependency as well as nonlinear frequency dependency were evaluated. Gaussian pulse propagating in a lossy medium suffers downshifting of a center frequency and decreasing in the bandwidth. Such changes in frequency domain spectrum were quantified in terms of changes in the attenuation coefficients with nonlinear dependency, which in turn improve clinical Implications of the coefficients. Statistical analysis shows that the attenuation coefficients evaluated with nonlinear dependency reflect an improved accuracy for the diffuse liver disease than those with linear dependency. The discriminant analysis also indicate the improved classification with nonlinear dependency(75%) than with linear dependency(61%).

• Journal of KSNVE
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• v.10 no.6
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• pp.1029-1034
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• 2000

A new electro-rheological squeeze film damper (ER-SFD) has been sealed with slotted piston rings which have electrodes at the inside of the constant gap. The slotted ER-SFD can prevent the problem of electric discharge which might be occurred in the previous configuration of an ER-SFD. The current paper presents the extraction of linearized dynamic coefficients within small orbit where these coefficients are controlled by the application of electric strength. Test rig has been modified to isolate the damper section for dynamic coefficient extraction. The results show that rotordynamic coefficients, damping and inertia terms, increase with increasing supply voltages, while stiffness coefficients decrease with increasing supply voltages. notating speed of rigid shaft does not affect these coefficients.

• Journal of the Korean Regional Science Association
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• v.12 no.2
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• pp.1-19
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• 1996

The purpose of this paper is to evaluate the accuracy of input coefficients which are usually estimated by various non-survey methods. The resulting analysis showed that there were considerable differences employed. One of the interesting findings was that the simple LQ method was shown to be better then the other non-survey methods with respect to the degree of accuracy. And from a sensitivity analysis which was to show the effect of changes in input coefficients on the level of production by industry, an increase of 10% in the value of input coefficient (machinary and equipment setor) resulted up to 500billion Won in GRP for the case region. Therfore one of the implications which we can derive from the resulting analysis is that it necessary to pay attention to the key coefficients first to save out time and money, while retaining a certain level of accuracy. One thing to be noted, however, is that the key coefficients but the total effects which are calculated through the Leontief inverse matrices. Therfore to enhance the accuracty of input coefficients estimated by nonsurvey methods it is required to handle the relevant setoral data more carefully or to employ semi-survey method in part.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.1
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• pp.52-62
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• 1995

The purpose of this study is to determine the wind pressure coefficients around prismatic structures with different aspect ratios. Air flows around a model of prismatic shape are investigated experimentally in the wind tunnel and simulated using finite volume method. Pressure distributions and the corresponding pressure coefficients are calculated from the experimental and numerical results. The effects of aspect ratios on the pressure coefficients are discussed extensively. The numerical results are compared with those of experiments. The simulated and experimental results for average wind pressure coefficients are considerably lower than those defined in the Korean Architectural Standard Code.