• Wind and Structures
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• 제37권3호
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• pp.211-227
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• 2023

To investigate the non-Gaussian feature of fluctuating wind pressures on rectangular high-rise buildings, wind tunnel tests were conducted on scale models with side ratios ranging from 1/9~9 in an open exposure for various wind directions. The high-order statistical moments, time histories, probability density distributions, and peak factors of pressure fluctuations are analyzed. The mixed normal-Weibull distribution, Gumbel-Weibull distribution, and lognormal-Weibull distribution are adopted to fit the probability density distribution of different non-Gaussian wind pressures. Zones of Gaussian and non-Gaussian are classified for rectangular buildings with various side ratios. The results indicate that on the side wall, the non-Gaussian wind pressures are related to the distance from the leading edge. Apart from the non-Gaussianity in the separated flow regions noted by some literature, wind pressures behind the area where reattachment happens present non-Gaussian nature as well. There is a new probability density distribution type of non-Gaussian wind pressure which has both long positive and negative tail found behind the reattachment regions. The correlation coefficient of wind pressures is proved to reflect the non-Gaussianity and a new method to estimate the mean reattachment length of rectangular high-rise building side wall is proposed by evaluating the correlation coefficient. For rectangular high-rise buildings, the mean reattachment length calculated by the correlation coefficient method along the height changes in a parabolic shape. Distributions of Gaussian and non-Gaussian wind pressures vary with side ratios. It is inappropriate to estimate the extreme loads of wind pressures using a fixed peak factor. The trend of the peak factor with side ratios on different walls is given.

• 수산해양기술연구
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• 제20권1호
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• pp.11-16
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• 1984

어군량의 추정에 필요한 활어체의 후방산란단면적을 실험수조 내에서 40KHz와 170KHz의 음파로써 담수어인 메기.잉어.틸라피아, 해수어인 볼낚.농어.숭어.용치놀래기 등에 대해 측면(side aspect)에서 각각 75~216회 측정한 결과는 다음과 같다. 1. 전장(total length)이 10.7~24.0cm인 어체들의 후방산란단면적은 5.62$\times$10 상(-5) m 상(2) ~7.23$\times$10 상(-4) m 상(2)였으며, 그 표적강도는 -42.50dB~-31.38dB이었다. 2. 어체의 크기와 표적강도의 일반적인 관계는 어종과 주파수에 따라 다르나, 대체로 큰 어체일수록 잘 반사하는 경향을 나타내었다. 3. 활어에 대한 유효산란길이의 확률분포와 Rayleigh 분포화의 적합도를 유의수준 5%에서 x 상(2) 검정한 결과, 파장에 대한 어체의 길이의 비(acoustic length ratio)가 4.5 및 4.7처럼 적을 때에는 Rayleigh 분포를 이루지 않는다는 것을 알 수 있었다.

• 한국정보통신학회논문지
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• 제6권4호
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• pp.527-534
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• 2002

본 논문에서는 다양한 페이딩 채널을 모델화 할 수 있는 나카가미-m 확률밀도함수를 이용하여 이동통실 채널 환경에서 필연적으로 존재하는 페이딩 환경을 고려한 DS/CDMA 시스템의 PN 부호획득에 대한 성능을 분석하였다. 시스템의 성능 분석은 나카가미-m 확률밀도함수를 이용하여 PN 부호 획득에 필요할 검출확률 PD와 오경보확률 PFA에 관한 식을 유도하였으며, 시뮬레이션을 통하여 검증하였다. 또한 DS/CDMA 시스템은 적응형 직렬 탐색 PN 부호 획득 기법을 사용하고, 위상 오류를 보정하기 위하여 레이크 수신기 각각의 브랜치에 PLL을 추가한 후 부호 획득 시간에 영향을 미치는 검출확률 PD와 오경보확률 PFA에 관한 식을 유도하였으며, 유도된 식을 이용하여 검출확률 PD,와 오경보확률 PFA을 시뮬레이션을 통해 검증하였다.

• Journal of the Korean Statistical Society
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• 제31권2호
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• pp.261-276
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• 2002

Probability density or its derivatives may have a discontinuity/change point at an unknown location. We propose a method of estimating the location and the jump size of the discontinuity point based on kernel type density or density derivatives estimators with one-sided equivalent kernels. The rates of convergence of the proposed estimators are derived, and the finite-sample performances of the methods are illustrated by simulated examples.

• 한국태양에너지학회 논문집
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• 제30권2호
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• pp.54-64
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• 2010

Interest in new and renewable energies like solar energy and wind energy is increasing throughout the world due to the rapidly expanding energy consumption and environmental reasons. An essential requirement for wind force power generation is estimating the size of wind energy accurately. Wind energy is estimated usually using meteorological data or field measurement. This study attempted to estimate wind energy density using meteorological data on daily mean wind speed and the Weibull parameters in Seoul, a representative inland city where over 60% of 15 story or higher apartments in Korea are situated, and Busan, Incheon, Ulsan and Jeju that are major coastal cities in Korea. According to the results of analysis, the monthly mean probability density distribution based on the daily mean wind speed agreed well with the monthly mean probability density distribution based on the Weibull parameters. This finding suggests that the Weibull parameters, which is highly applicable and convenient, can be utilized to estimate the wind energy density distribution of each area. Another finding was that wind energy density was higher in coastal cities Busan and Incheon than in inland city Seoul.

• Journal of electromagnetic engineering and science
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• 제8권2호
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• pp.59-63
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• 2008

The adaptive symbol selection scheme(ASSS) is popular in reducing peak to average power ratio(PAPR) for orthogonal frequency division multiplexing(OFDM) signals. The probability density function(pdf) of the samples' amplitudes of the adaptively selected OFDM signal without over-sampling has been considered to be approximately equal to the Rayleigh pdf. In this paper, we derive a more precise pdf which shows the relationship between the probability distribution of the samples' amplitudes and the number of the candidate symbols for ASSS. Using the newly derived pdf in the theoretical analysis, more accurate calculation results can be obtained.

• 전기학회논문지P
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• 제58권3호
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• pp.241-248
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• 2009

This paper presents stochastic methodology based fault detection algorithm for induction motor systems. We measure current of healthy induction motors by means of hall sensor systems and then establish its probability distribution. We propose online probability density estimation which is effective in real-time implementation due to its simplicity and low computational burden. In addition, we accomplish theoretical analysis of the proposed estimation to demonstrate its convergence property by using statistical convergence and system stability theories. We apply our fault detection approach to three-phase induction motors and achieve real-time experiment for evaluating its reliability and practicability in industrial fields.

• Wind and Structures
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• 제4권1호
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• pp.73-84
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• 2001

Analysis of pressures measured on the roof of the full-scale Texas Tech building and a 1/50 scale model of a typical house showed that the pressure fluctuations on cladding fastener and cladding-truss connection tributary areas have similar characteristics. The probability density functions of pressure fluctuations on these areas are negatively skewed from Gaussian, with pressure peak factors less than -5.5. The fluctuating pressure energy is mostly contained at full-scale frequencies of up to about 0.6 Hz. Pressure coefficients, $C_p$ and local pressure factors, $K_l$ given in the Australian wind load standard AS1170.2 are generally satisfactory, except for some small cladding fastener tributary areas near the edges.

• 대한기계학회논문집
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• 제18권2호
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• pp.492-501
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• 1994

This study is an analysis of the turbulent diffusion flame with swirl flow and the calculated results are compared with experimental data in case of various swirl numbers and air-fuel rations. The mathematical model is restricted to single-phase, diffusion controlled combustion with swirl flow. Values of local flow properties were obtained by solving appropriate differential equation for continuity, momentum, stagnation enthalpy, concentration, turbulence energy, dissipation rate of turbulence energy, and the mean square of concentration fluctuation. The method is proposed for calculating the local probability of chemical reaction based on the use of the probability density function for the mixture fraction.

• 한국통신학회논문지
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• 제25권1A호
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• pp.48-55
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• 2000

본 논문에서는 모의 실험을 통하여, 데이터의 분포가 Gauss 분포, 균등 분포 등의 경우, 어느 한 구간이 다른 구간에 비하여 확률도 크고 구간내의 오차도 크다면 이는 최적 양자화가 아니다라는 가정을 하였다. 이 가정을 LBG 알고리즘에 추가하여 수정된 LBG 알고리즘을 만들고, 이 알고리즘의 성능을 측정하였다. 수정된 알고리즘에 의한 코드 북의 오차는 본래의 알고리즘에 비하여 오차의 크기도 감소하였고, 오차의 편차도 감소하였다.