• ETRI Journal
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• 제42권5호
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• pp.712-720
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• 2020

Recently, to make the best use of limited and precious spectrum resources, spectrum sharing between satellite and cellular networks has received much interest. In this study, we mathematically analyze the success probability of a fixed (satellite) earth station (FES) based on a stochastic geometry framework. Both the FES and base stations (BSs) are assumed to be equipped with a directional antenna, and the location and the number of BSs are modeled based on the Poisson point process. Furthermore, an exclusion zone is considered, in which the BSs are prohibited from locating in a circular zone with a certain radius around the FES to protect it from severe interference from the cellular BSs. We validate the analytical results on the success probability of the cognitive satellite-terrestrial network with directional antennas by comparing it using extensive computer simulations and show the effect of the exclusion zone on the success probability at the FES. It is shown that the exclusion zone-based interference mitigation technique significantly improves the success probability as the exclusion zone increases.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.317-324
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• 2006

Performance-based design concept is needed to evaluate the seismic capacity of building. In this study, the method estimating the performance point of the spatial structures based on capacity spectrum method (CSM) is proposed. And for efficient evaluation for the performance point of the spatial structures, the algorithm to convert spatial structural system to ESDOF system is simulated Its efficiency is confirmed by comparing with time history analysis of full model. And dynamic behaviors of spatial structures are examined by using this method. At last, evaluation of structural performance according to variation of stiffness after plastic deformation on the substructures is carried out.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.232-236
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• 2003

The anchor is laid on seabed and the main engine is worked to against incident environmental loads in typoon. As the main engine is broken down in the storm, the anchor chain is cutted and the vessel is drifted. Although a ship is moored by two point mooring lines to keep the her position, a ship is crashed into a rock because of typoon and the accident of oil spilling may be occured. In this paper, we studied the position-keeping of a ship which is analyized based on the slow motion maneuvering equations considering wave, current and wind. The direct integration method is employed to estimate wave loads. The current forces are calculated by using mathematical of MMG. The two point mooring forces are quasisatatically evaluated by using the catenary equation. The coefficeints of wind forces are modeled from Isherwood’s emperical data and the variation of wind speed is estimated by wind spectrum. The nonlinear motions of a two point moored ship are simulated considering wave, current, wind load in time domain.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.45-54
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• 2012

In order to predict trailing edge noise from a flat plate more effectively and accurately, the prediction algorithm based on semi-analytic model for point pressure spectrum is proposed. The semi-analytic model consists of empirical models for point pressure spectra and theoretical model to determine the boundary layer characteristics needed for the empirical models. The proposed methods are applied to predict the trailing edge noise of the flat plate located in the mean flow of speed 38 m/s, for which the measured data are available. In present study, six empirical models for point pressure spectra are utilized for the predictions of trailing edge noise and their prediction results are compared to the measured data. Through the analysis of these comparisons, it is revealed that the present method based on non-frozen formula using Efimtsov model and Smol'yakov-Tkachenko model can provide more accurate and efficient predictions of trailing edge noise.

• 한국해양공학회지
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• 제18권3호
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• pp.8-12
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• 2004

The anchor is laid on the seabed, and the main engine is working against incident environmental loads in a typhoon. As the main engine is broken Mum in the storm, the anchor chain is cut and the vessel drifts. Although a ship is moored by two-point mooring lines to maintain her position, it has crashed into a rock because of a typhoon, resulting in a possible accidental oil spillage. In this paper, we studied maintenance of a ship's position, which is analyzed based on the slow motion maneuvering equations considering wave, current, and wind. To estimate wave loads, the direct integration method is employed. The current forces are calculated, using MMG (Mathematical Modeling Group). Th two-point mooring forces are quasi-statistically evaluated, using the catenary equation. Th coefficients of wind forces are modeled from Isherwood's empirical data, and the variation of wind speed is estimated by wind spectrum. The nonlinear motions of a two-point moored ship are simulated, considering wave, current, and wind load, in specific domain of time.

• 한국소음진동공학회논문집
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• 제22권6호
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• pp.524-534
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• 2012

In order to predict trailing edge noise from a flat plate more effectively and accurately, the prediction algorithm based on semi-analytic model for point pressure spectrum is proposed. The semi-analytic model consists of empirical models for point pressure spectra and theoretical model to determine the boundary layer characteristics needed for the empirical models. The proposed methods are applied to predict the trailing edge noise of the flat plate located in the mean flow of speed 38 m/s, for which the measured data are available. In present study, six empirical models for point pressure spectra are utilized for the predictions of trailing edge noise and their prediction results are compared to the measured data. Through the analysis of these comparisons, it is revealed that the present method based on non-frozen formula using Efimtsov model and Smol'yakov-Tkachenko model can provide more accurate and efficient predictions of trailing edge noise.

• 산업기술연구
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• 제24권A호
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• pp.185-194
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• 2004

To evaluate seismic performance of reinforced concrete piers two procedures for capacity spectrum method are presented. The capacity spectrum procedures include the reduction factor-ductility-period($R_{\mu}-{\mu}-T$)relationship in order to construct the inelastic demand spectra from the elastic demand spectra. Application of the procedures are illustrated by example analysis. Maximum displacements estimated by the procedures are compared to those by inelastic time history analysis for several artificial earthquakes. The results show that the maximum displacements estimated by the procedures are, on overall, smaller than those by the inelastic time history analysis.

• 음성과학
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• 제10권4호
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• pp.137-147
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• 2003

Speech synthesis can classify by synthesis way, that is waveform coding, source coding and mixture coding. Specially, waveform coding is suitable for high quality synthesis. However, it is not desirable by synthesis techniques of syllable or phoneme unit because it do not separate and handles excitation and formant part. Therefore, there is a need for pitch alteration method applied in synthesis by the rule in waveform coding. This study propose about pitch alteration method that use spectrum scaling after do to flatten spectra by subband linear approximation to minimize spectrum distortion. This paper show evaluation whether show excellency of some measure compared with LPC, Cepstrum, lifter function and method that propose. estimation method seeks distribution of each flattened signal and measured degree of flattened spectra Signal flattened is normalized, So that highest point amounts to zero, and distribution of signal ,whose average is zero, is calculated. this show result that measure the spectrum distortion rate to estimate performance of method that propose. The average spectrum distortion rate was kept below the average 2.12%, so the method that propose is superiors than existent method.

• 한국전자파학회논문지
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• 제25권10호
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• pp.995-1004
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• 2014

전파이용 기술의 발전 및 관련 서비스의 다양화로 전파 자원의 희소성이 높아질수록 주파수 자원 배분은 효율성과 형평성을 제고할 필요성은 높아진다. 개방형 전파 사용 정책은 다양한 의미를 포함하는데, 타인의 이용을 배제하지 않고 누구나 사용할 수 있도록 하는 주파수 공유(spectrum commons)를 의미하는 경우 전파이용의 형평성과 효율성이 증진되고, 나아가 기존의 이용자들이 있는 경우에도 이를 방해하지 않는 범위에서 세분화된 이용권을 설정함으로써 다른 이용자들의 사용에 개방하는 것을 의미하는 경우에도 역시 효율성과 형평성을 제고할 수 있다. 개방형 전파 사용을 위해서는 기술 발전이 우선되어야 하지만, 전파 사용 질서를 형성하는 전파법 제도가 이러한 개방형 전파 사용을 허용하고, 그로부터 발생하는 분쟁을 사전에 예방하고 신속히 조정할 수 있는 메카니즘을 마련하는 등 이를 뒷받침할 필요가 있다. 이 논문에서는 그러한 법제적 조치의 필요성을 주파수 공동사용의 허용, 개시, 관리, 해소의 단계마다 검토하고 기본적인 정비방향을 제시하고 있다.

• 한국방사선학회논문지
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• 제17권6호
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• pp.889-896
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• 2023

핵의학과에서 가장 많이 사용되는 ^99mTc를 점선원과 산란팬텀을 이용하여 에너지스펙트럼 변화를 분석하고 변화된 감마선 에너지에 따른 납 앞치마의 차폐효과를 평가하였다. 산란팬텀의 감마선 에너지 스펙트럼은 점선원보다 광전피크 영역은 감소하고 컴프턴 산란영역은 증가하였다. 감마선원 형태 변화에 따른 에너지 영역별 계수치는 점선원의 계수치보다 20 cm 거리에서 최대 66.1 %의 감소율을 보였으며 컴프턴 산란 영역에서는 산란팬텀의의 계수치가 점선원의 계수치보다 최대 40 cm 거리에서 122.2 % 증가하는 결과를 보였다. 감마카메라를 이용한 선원과 산란팬텀의 거리에 따른 차폐율 차이에서 광전피크 영역은 유사한 결과를 보였으나 컴프턴 산란영역에서는 20 cm거리에서 산란팬텀의 차폐율이 점선원의 차폐율보다 29.2% 증가하였으며 거리가 증가함에 따라 차폐율 차이는 감소하였다. 방사선 선량계를 이용한 납 앞치마 차폐율 측정에서 산란팬텀의 차폐율은 최대 15.3 %의 차이를 보였으며 거리가 증가할수록 두 선원의 차폐율 차이는 감소하였다. 산란팬텀의 납 앞치마 차폐율이 점선원보다 높고 선원과 가까운 거리일수록 납 앞치마의 효과는 증가하는 결과로 방사성의약품을 주입한 환자를 직접 대면할 때 납 앞치마의 착용은 방사선피폭 저감화에 도움이 될 것으로 판단된다.