• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.20 no.1
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• pp.11-16
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• 1984

The backscattering cross sections of live fish and the probability density function of fish echoes were measured at side aspect. The measurements were made at 40 and 170 in KHz. The specimen fishes on the experiments were two catfish-total length of 16.8cm(L/λ is about 4.5, where the L is length, the λ is the sound wavelength) and 23cm(L/λ, ~6.1), a carp(Cyprinus carpio) of 17.5cm(L/λ, ~4.7), a Telapia(Tilapia mossambica)of 19.5cm(L/λ, ~5.2) and several fishes. Those lengths ranged from 10.7 to 24.0cm. The results of the measured maximum backscattering cross sections were 5.62$\times$10 super(-5) to 7.23$\times$10 super(-4) m super(2). Huang and clay reported that, when the fish was moving gently, the probaiblity density function of the fish echces was approximately the same with the Rayleigh probability density function. Thereafter Ehrenberg et al. also reported that the Rayleigh probability density function on fish was performed at the critical acoustic length ratio or more in theoretical base. Recently Dahl and Mathisen tested the Rayleigh probability density function on fish when the fish-length-to-wavelength ratios were greater than 100. In this paper the experimental result was also not accorded with the Rayleigh probability density function when the fish-length-to-wavelength rations were lower than the critical ratio.

• Journal of Korea Water Resources Association
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• v.51 no.3
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• pp.207-219
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• 2018

In this study, the ecological flow rate of the Zacco playtypus habitat was simulated based on the Instream Flow Incremental Methodology (IFIM) in reachs of urban and natural stream using the habitat suitability index (HSI) of the probability density function (PDF). To apply this method, PHABSIM model was used in this study. However, in this study, the HSI of the probability density function was developed by adjusting the parameters of the PDF based on Kang (2010) HSI. As a result, the normal distribution is closest to the ecological flow rate of the Kang (2010) in the urban stream. However, the two-parameter log-pearson distribution tended to be the closest in the natural stream. The ecological flow rate was simulated by the HSI and the reach of stream with the PDF. Based on the comparison of simulation results, we propose an ecological flow rate estimation method using probabilistic method.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.5
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• pp.619-629
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• 1998

An experimental work was conducted to investigate a feasibility of simultaneous measurement of gas-liquid two-phase flowrates with double orifice plates using air and water. The tests were carried out under the atmospheric pressure and at the ambient temperature using two different tube sizes. Qualities of an air-water flow in the present study have values less than 0.1 and thus the mixed flow showed bubbly, plug, slug flow regimes. The probability density function (PDF) and the power spectral density function (PSDF) of the instantaneous pressure drop traces for the flow regimes were obtained. It is found that some distinctive features exist in the distribution of these functions, depending upon the two-phase flow pattern. The time-averaged value of the instantaneous pressure drop increases with increasing gas and liquid flowrates, showing a single-valued function for the total mass flowrate and the quality. It is also found that the two-phase discharge coefficient exhibits a consistent trend for variation of dimensionless parameters such as the superficial velocity ratio and the gas Reynolds number. The results indicate that simultaneous measurement of two-phase flowrate may be possible based upon a statistical analysis of the instantaneous pressure drop curves monitored using double orifice plates.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1987.04a
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• pp.191-195
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• 1987

When a 160QAM receiver in the band of spread spectrum system is interfered with a pseudo-random frequency-hopp-ing signal the interference signal has the form of the pulse amplitude probability density function. Each interfrering pulse amplitude probability density function Each interfering pulse amplitude is dependent upon theprobability density function of hopping frequency and the selectivity characteristic of 16QAM system in this paper the error rate equation of a system performance has been derived in the above condition which are interfrerence form and impulsive noise environmensts. The results of system analysis show us that the system performance is de-graded by impulsive noise and interference power, which improved as the frequency hopping bandsidth increases whit respect to receiver bandwidth

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.6
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• pp.993-999
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• 2004

The estimation of fatigue life at the design stage of membrane type LNG tank is very important in order to arrive at feasible and cost effective solutions considering the total lifetime of the tank. In this study, the practical procedure of fatigue life prediction by use of cumulative damage factors based on Miner-Palmgren hypothesis and probability density function has been shown with the corner region of Gaz Transport Membrane type LNG tank being used as an example. In particular the parameters of Weibull distribution that determine the stress spectrum are discussed. The main results obtained from this study are as follows: 1. The recommended value for the shape parameter of Weibull distribution for the LNG tank is 1.1 in case of using the direct calculation method proposed in this study. 2. The calculated fatigue life is influenced by the shape parameter of Weibull distribution and stress block. The safe fatigue design can be achieved by using higher value of shape parameter and the stress blocks divided into more stress blocks.

• Journal of ILASS-Korea
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• v.22 no.3
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• pp.137-145
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• 2017

This paper describes numerical modeling of transcritical and supercritical fluid flows within a liquid propellant rocket engine. In the present paper, turbulence is modeled by standard $k-{\varepsilon}$ model. A conserved scalar approach in conjunction with multi-environment probability density function model is used to account for the turbulent mixing of real-fluids in the transcritical and supercritical region. The two real-fluid equations of state and dense-fluid correction schemes for mixtures are used to construct thermodynamic data library based on the conserved scalar. In this study, calculations are made on two cryogenic nitrogen jets under different chamber pressures. Sensitivity analysis for two different real-fluid equations of sate is particularly emphasized. Based on numerical results, precise structures of cryogenic nitrogen jets are discussed in detail. Numerical results show that the current real-fluid model can predict the essential features of the cryogenic liquid nitrogen jets.

• Structural Engineering and Mechanics
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• v.67 no.5
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• pp.439-455
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• 2018

Within a probabilistic framework, this paper addresses the determination of the static structural response of beams and frames with partially restrained (semi-rigid) connections. The flexibility of the nodal connections is incorporated via an idealized linear-elastic behavior of the beam constraints through the use of rotational springs, which are here considered uncertain for taking into account the largely scattered results observed in experimental findings. The analysis is conducted via the Probabilistic Transformation Method, by modelling the spring stiffness terms (or equivalently, the fixity factors of the beam) as uniformly distributed random variables. The limit values of the Eurocode 3 fixity factors for steel semi-rigid connections are assumed. The exact probability density function of a few indicators of the structural response is derived and discussed in order to identify to what extent the uncertainty of the beam constraints affects the resulting beam response. Some design considerations arise which point out the paramount importance of probability-based approaches whenever a comprehensive experimental background regarding the stiffness of the beam connection is lacking, for example in steel frames with semi-rigid connections or in precast reinforced concrete framed structures. Indeed, it is demonstrated that resorting to deterministic approaches may lead to misleading (and in some cases non-conservative) outcomes from a design viewpoint.

• The Journal of the Acoustical Society of Korea
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• v.20 no.2
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• pp.3-9
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• 2001

In this paper, a random number generator for simulation of speech-waveform coders was designed. A random number generator having a desired probability density function and a desired power spectral density is discussed and experimental results are presented. The technique is based on Sondhi algorithm which consists of a linear filter and a memoryless nonlinearity. Several methods of obtaining memoryless nonlinearities for some typical continuous distributions are discussed. Sondhi algorithm is analyzed in the time domain using the diagonal expansion of the bivariate Gaussian probability density function. It is shown that the Sondhi algorithm gives satisfactory results when the memoryless nonlinearity is given in an antisymmetric form as in uniform, Cauchy, binary and gamma distribution. It is shown that the Sondhi algorithm does not perform well when the corresponding memoryless nonlinearity cannot be obtained analytically as in Student-t and F distributions, and when the memoryless nonlinearity can not be expressed in an antisymmetric form as in chi-squared and lognormal distributions.

• Communications for Statistical Applications and Methods
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• v.15 no.6
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• pp.939-946
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• 2008

In this paper the support vector method is presented for the probability density function estimation when the sample observations are contaminated with random noise. The performance of the procedure is compared to kernel density estimates by the simulation study.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1984.10a
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• pp.92-95
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• 1984

This paper describes the output P.D.F. of various Compandors, optimum, -law and A-law for the Gaussian and Laplacian Density as an input analog signal. Also we consider the truncated densities compensated by weighted impulse or density coefficient.