• Journal of Mechanical Science and Technology
• /
• v.16 no.5
• /
• pp.583-590
• /
• 2002

When a mechanical structure is driven by stationary wide band random point forces, the resulting vibration depends upon the number, location, and joint statistical properties of the exciting forces. In this study, under the assumption of light damping, an approximate procedure for analyzing plates is briefly outlined. The effects of number, location and correlation of the force field on the vibration level are then investigated for various cases in which random point forces with band limited white noise are applied, and the optimal spacing between input forces that produces a relative minimum in the vibration response is predicted.

• Journal of the Korean Society for Precision Engineering
• /
• v.11 no.1
• /
• pp.166-176
• /
• 1994

The problem of reducing the vibration level of elastic plates driven by multiple random point forces is analyzed in this study. First, the analytical solution for the vibration level of finite thin plates with four simply supported edges under the action of multiple random point force is derived. By assuming the plates to be lightly damped, an approximate solution for the vibration level of the plate is obtained. A numerical study is carried out to determine an optimal spacing distance between the multiple point forces in order to produce a relative minimum in the plate's vibration level. The optimal spacing distance is shown to depend on the given excitation band. The effects of wave cancellation in the near field of the multiple point forces are discussed by using the equivalence of certain stationary random responses and deterministic pulse responese.

• Journal of information and communication convergence engineering
• /
• v.16 no.1
• /
• pp.38-42
• /
• 2018

In this paper, we consider measurement allocation problem in a spatially correlated sensor field. Our goal is to determine the probability of each sensor's being measured based on its contribution to the estimation reliability; it is desirable that a sensor improving the estimation reliability is measured more frequently. We consider a spatial correlation model of a sensor field reflecting transmission power limit, noise in measurement and transmission channel, and channel attenuation. Then the estimation reliability is defined distortion error between event source and its estimation at sink. Motivated by the correlation nature, we model the measurement allocation problem into a cooperative game, and then quantify each sensor's contribution using Shapley value. Against the intractability in the computation of exact Shapley value, we deploy a randomized method that enables to compute the approximate Shapley value within a reasonable time. Besides, we envisage a measurement scheduling achieving the balance between network lifetime and estimation reliability.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2003.09a
• /
• pp.90-97
• /
• 2003

The purpose of this study is to understand the dissipation pattern of excess pore pressure after liquefaction which governs the post-liquefaction behavior of liquefied sand deposits. 1-g shaking table tests were carried out on 5 different kinds of sands, all of which had high liquefaction potentials. During the tests excess pore pressure at various depths, and surface settlements were measured. The measured curve of the excess pore pressure dissipation was simulated using the solidification theory, and from the analysis of the velocity of dissipation, the dissipation pattern of excess pore pressure after liquefaction was examined. The dissipation velocity of excess pore pressure after liquefaction had a linear correlation with the effective grain size ( $D_{10}$) divided by the coefficient of uniformity ( $C_{u}$), and the increase in the initial relative density of the ground played a role in shifting this correlation curve toward an increased dissipation velocity. From the correlation, an approximate method was recommended for prediction of the dissipation curve of excess pore pressure after liquefaction in saturated sand deposits.s.s.

• Korean Journal of Microbiology
• /
• v.28 no.4
• /
• pp.283-289
• /
• 1990

The competence time of Streptomyces viridochromogenes for aerial mycelium formation was determined. Within 10 hrs after spore inoculation the submerged mycelium was programed to form aerial mycelium, when the former was laid on agar plate. The white aerial mycelium was formed 17-22 hrs after the transfer. Ascorbic acid oxidizing enzyme band on native gel showed chracteristic mobility change during aerial mycelium formation. Total activity of this enzyme did not show any correlation with the differentiation. The asay condition for the crude enzyme was determined. EDTA and $FeCl_{2}$ showed stimulatory effect. Approximate ratio of oxygen consumed to ascorbic acid oxidized was 1:1.

• Bulletin of the Korean Chemical Society
• /
• v.16 no.11
• /
• pp.1113-1118
• /
• 1995

The Schlo'gl model with the first order transition for a photochemical reaction is considered to study the dynamic behaviors in the neighborhood of the Gaussian white noise by obtaining the explicit results of the time-dependent variance and time correlation function with the aid of approximate methods based on the stationary properties of the system. Then, we discuss the effect of external noise strength on the stability of the model at steady states in detail.

• Bulletin of the Korean Chemical Society
• /
• v.6 no.5
• /
• pp.295-299
• /
• 1985

An approximate solution of the Fokker-Planck equation with the nonlinear drift term due to a Schlogl model is obtained and the result is compared with the methods proposed by Suzuki. Also the effect of nonlinearity on the correlation length at the stable steady state is studied.

• Journal of the Korean Wood Science and Technology
• /
• v.49 no.6
• /
• pp.541-549
• /
• 2021

This paper reports a method to evaluate the residual strength of insect-damaged radiata pine lumber, such as the screw withdrawal strength as a semi-destructive method and a compression parallel to the grain test to assess the density changes after exposure to outdoor conditions. The screw withdrawal strength test was used as a semi-destructive method to estimate the residual density of decayed lumber. A compression parallel to the grain test was applied to evaluate the residual density. Three variables, such as the screw withdrawal strength, compression parallel to the grain, and residual density, were analyzed statistically to evaluate their relationships. The relationship between the residual density and screw withdrawal strength showed a good correlation, in which the screw withdrawal strength decreased with decreasing density. The other relationship between the residual density and compression parallel to the grain was also positively correlated; the compression parallel to the grain strength decreased with decreasing density. Finally, the correlation between the three variables was statistically significant, and the mutual correlation coefficients showed a strong correlation between the three variables. Hence, these variables are closely correlated. The test results showed that the screw withdrawal strength could be used as a semi-destructive method for an in situ estimation of an existing wood structure. Moreover, the method might approximate the residual density and compression parallel to the grain if supplemented with additional data.

• The Bulletin of The Korean Astronomical Society
• /
• v.46 no.2
• /
• pp.72.3-73
• /
• 2021

Baryon Acoustic Oscillations (BAO) are caused by acoustic density waves in the early universe and act as a standard ruler in the clustering pattern of galaxies in the late Universe. Measuring the BAO feature in the 2-point correlation function of a sample of galaxies allows us to estimate cosmological distances to the galaxies mean redshift, , which is important for testing and constraining the cosmology model. The BAO feature is also expected to appear in the higher order statistics. In this work we measure the generalized spatial N-point point correlation functions up to 4th order. We made measurements of the 2, 3, and 4-point correlation functions in the SDSS-III DR12 CMASS data, comprising of 777,202 galaxies. The errors and covariances matrices were estimated from 500 mock catalogues. We created a theoretical model for these statistics by measuring the N-point functions in halo catalogues produced by the approximate Lagrangian perturbation theory based simulation code, PINOCCHIO. We created simulations using initial conditions with and without the BAO feature. We find that the BAO is detected to high significance up to the 4-point correlation function.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1999.10a
• /
• pp.117-122
• /
• 1999

Laboratory and field investigations of the coefficient of vertical and horizontal consolidation for Yangsan clay deposit were carried out using the conventional oedometer, Rowecell and piezocone test. Correlation among these test methods were also studied. In this paper, the relationship between vertical and horizontal consolidation were suggested such as C$\sub$h(Oed)/=0.75∼1.46 C$\sub$v(Oed)/, C$\sub$h(Rowecell) =1.95∼2.93 C$\sub$v(Oed)/, C$\sub$h(piezocone)/ =1.0∼5.0 C$\sub$v(Oed)/. As a result, a fair approximate estimations of C$\sub$h/ can be made by simple test using the conventional oedometer tests.