• Journal of the Korean earth science society
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• v.23 no.1
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• pp.15-29
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• 2002

Bayesian inversion for gravity and resistivity data was performed to investigate the cavity structure appearing as a lava tunnel in Cheju Island, Korea. Dipole-dipole DC resistivity data were proposed for a prior information of gravity data and we applied the geostatistical techniques such as kriging and simulation algorithms to provide a prior model information and covariance matrix in data domain. The inverted resistivity section gave the indicator variogram modeling for each threshold and it provided spatial uncertainty to give a prior PDF by sequential indicator simulations. We also presented a more objective way to make data covariance matrix that reflects the state of the achieved field data by geostatistical technique, cross-validation. Then Gaussian approximation was adopted for the inference of characteristics of the marginal distributions of model parameters and Broyden update for simple calculation of sensitivity matrix and SVD was applied. Generally cavity investigation by geophysical exploration is difficult and success is hard to be achieved. However, this exotic multiple interpretations showed remarkable improvement and stability for interpretation when compared to data-fit alone results, and suggested the possibility of diverse application for Bayesian inversion in geophysical inverse problem.

• Wind and Structures
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• v.29 no.6
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• pp.441-455
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• 2019

In this study, vortex induced vibrations of a cylinder mounted on a flexible rod are analyzed. This simple configuration represents the key element of new conception bladeless wind turbine (Whitlock 2015). In this study the structure oscillations equation coupled to the wake oscillation equation for this configuration are solved using analytical perturbation method, for the first time. An analytical expression that predicts the lock-in phenomena range of wind speed is derived. The discretized equations of motion are also solved using RKF45 numerical method. The equations of motion are discretized by Galerkin method. Free vibration mode shape of the structure taking into account the discontinuity of the cross section are used as comparison function. Numerical results are compared to the analytical results, and they show a satisfying agreement. The effect of system parameters on the oscillations of structure and wake as well as on the lock-in domain are presented. Moreover, it is shown that the values of wind speed triggering the start and the stop of the lock-in phenomenon, for increasing wind speed are different from those values obtained during the reverse process, i.e., when the wind speed decreases.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.2
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• pp.479-491
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• 1994

Discrete vortex method was applied for simulating an active control of turbulent leading- edge separation bubble. The leading-edge separation zone was perturbed by a time-dependent sinusoidal perturbation of different frequencies and levels. In order to describe the local sinusoidal perturbation at the separation point, a source pulsation vortex technique was proposed. The present two-dimensional vortex simulations were qualitatively compared with the experimental results for a blunt circular cylinder, where perturbation was introduced along the square-cut leading edge of the cylinder $(Kiya et al.^{(6,7)}).$ It was found that the reattachment length attained a minimum point at low levels of perturbation and two minima at a moderate higher perturbation frequency. The effects of local perturbation on the evolution of leading-edge separation bubble were scrutinized by comparing the perturbed flow with the natural flow. These comparisons were made for the distributions of mean velocity and its velocity fluctuations, intermittency and wall velocity. The motions of instantaneous reattachment in the space-time domain were demonstrated, which were also compared with the experimental findings. In order to investigate the reduction mehanism of reattachment length in the separation bubble, various cross-correlations for velocity and pressure and the relevant convection velocities were evaluated. It was observed that the convection velocity was closely associated with its corresponding pulsationg frequency.

• Water for future
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• v.25 no.4
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• pp.61-73
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• 1992

There are needs to examine the consequences of a regulation in effect to control the migration of leachates from disposal sites. The main objective of this study is to illustrate the methodology to evaluate basic disposal designs for compliance with a certain regulation, The "100/100 rule" is selected for demonstration purpose which dictates that the time for the leachates to travel a horizontal distance of 100feet (30.5m) away from the property where the landfill or pond is located must exceed 100 years. The two primary methods for disposal of ash from coal-fired utility plants, landfill and pond, are studied, Numerical groundwater flow analysis resulted in pressure head distribution and flux information in the cross-section of the domain while path line analysis provided travel path and time of leachate migration to compliance zone.ance zone.

• Korean Journal of Veterinary Research
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• v.37 no.3
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• pp.547-554
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• 1997

Galectin-3 is known as an animal ${\beta}$-galactoside-binding lectin charicterized with S-type carbohydrate recognition domain. It plays a role in growth, adherence and movement of cells. It is, also, related to the cell transformation and metastasis of tumor cells. In this study, we have expressed and purified recombinant human galectin-3 (rHgalectin-3) using E coli system and asialofetuin affinity chromatography for the future development of monoclonal antibody to Hgalectin-3, which is suggested as the tumor marker for the gastric and thyroid gland cancers. Expressed protein was confirmed as the Hgalectin-3 by immunoblot with cross-reactive murine monoclonal antibody. Lectin activity and specificity of purified protein were, also, confirmed by the competitive inhibition with galectin-3 specific carbohydrate, lactose. Like physiological galectin-3, lectin activity of the molecule was not changed in nonreduced condition. Dimer formation, furthermore, was observed at high concentration of the protein even in the reduced condition, which is well known in physiological galectin-3. These results showed purified rHgalectin-3 has the same activity and molecular nature compared to the physiological galectin-3.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.6
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• pp.929-938
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• 2000

A summary of the development and verifications of a computer code being developed at Pohang University of Science and Technology (POSTECH) for calculating the radar cross section(RCS) of complex targets is presented. The complex targets are modeled in terms of patches and wedges. This code utilizes physical optics, physical theory of diffraction and shooting and bouncing rays method to calculate the RCS of complex targets. For the verification of the RCS prediction code, a simple-shaped scale-model was manufactured and the RCS was measured at the POSTECH compact range. The obtained RCS was processed to give frequency-domain RCS patterns and ISAR images. The predicted RCS shows good agreement with measured one. The RCS prediction methods presented here are applicable to stealth design and target recognition.

• Wind and Structures
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• v.7 no.2
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• pp.107-130
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• 2004

This paper presents a time-domain approach for analyzing nonlinear random vibrations of long-span suspended cables under transversal wind. A consistent continuous model of the cable, fully accounting for geometrical nonlinearities inherent in cable behavior, is adopted. The effects of spatial correlation are properly included by modeling wind velocity fluctuation as a random function of time and of a single spatial variable ranging over cable span, namely as a one-variate bi-dimensional (1V-2D) random field. Within the context of a Galerkin's discretization of the equations governing cable motion, a very efficient Monte Carlo-based technique for second-order analysis of the response is proposed. This procedure starts by generating sample functions of the generalized aerodynamic loads by using the spectral decomposition of the cross-power spectral density function of wind turbulence field. Relying on the physical meaning of both the spectral properties of wind velocity fluctuation and the mode shapes of the vibrating cable, the computational efficiency is greatly enhanced by applying a truncation procedure according to which just the first few significant loading and structural modal contributions are retained.

• Journal of Astronomy and Space Sciences
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• v.6 no.1
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• pp.1-15
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• 1989

Magnetospheic substorm in the magnetotail region is studied numerically by means of a three dimensional MHD code. The analytic solution for the quiet magnetotail is employed as an initial configuration. The localized solar wind is modeled to enter the simulation domain through the boundaries located in the magnetotail lobe region. As a result of the interaction between the solar wind and the magnetosphere, the magnetic field lines are stretched, and the plasma sheet becomes thinner and thinner. When the current driven resistivity is generated, magnetic reconnection is triggered by this resistivity. The resulting plasma jetting is found to be super-magnetosonic. Although the plasmoid formation and its tailward motion is not quite clear as in the two dimensional simulation, which is mainly because of the numerical model chosen for the present simulation, the rarification of the plasmas near the x-point is observed. Field aligned currents are observed in the late expansive stage of the magnetospheric substorm. These field aligned currents flow from the tail toward the ionosphere on the dawn side from the ionosphere to ward the tail on the dusk side, namely in the same sense of the region 1 current. As the field aligned currents develop, it is found that the cross tail current in the earth side midnight section of the magnetic x-point is reduced.

• Wind and Structures
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• v.21 no.5
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• pp.461-487
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• 2015

In recent years, the Graphics Processing Unit (GPU) has become a competitive computing technology in comparison with the standard Central Processing Unit (CPU) technology due to reduced unit cost, energy and computing time. This paper describes the derivation and implementation of GPU-based algorithms for the analysis of wind loading uncertainty on high-rise systems, in line with the research field of probability-based wind engineering. The study begins by presenting an application of the GPU technology to basic linear algebra problems to demonstrate advantages and limitations. Subsequently, Monte-Carlo integration and synthetic generation of wind turbulence are examined. Finally, the GPU architecture is used for the dynamic analysis of three high-rise structural systems under uncertain wind loads. In the first example the fragility analysis of a single degree-of-freedom structure is illustrated. Since fragility analysis employs sampling-based Monte Carlo simulation, it is feasible to distribute the evaluation of different random parameters among different GPU threads and to compute the results in parallel. In the second case the fragility analysis is carried out on a continuum structure, i.e., a tall building, in which double integration is required to evaluate the generalized turbulent wind load and the dynamic response in the frequency domain. The third example examines the computation of the generalized coupled wind load and response on a tall building in both along-wind and cross-wind directions. It is concluded that the GPU can perform computational tasks on average 10 times faster than the CPU.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.43 no.2
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• pp.33-38
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• 2020

Anomaly detection of Machine Learning such as PCA anomaly detection and CNN image classification has been focused on cross-sectional data. In this paper, two approaches has been suggested to apply ML techniques for identifying the failure time of big time series data. PCA anomaly detection to identify time rows as normal or abnormal was suggested by converting subjects identification problem to time domain. CNN image classification was suggested to identify the failure time by re-structuring of time series data, which computed the correlation matrix of one minute data and converted to tiff image format. Also, LASSO, one of feature selection methods, was applied to select the most affecting variables which could identify the failure status. For the empirical study, time series data was collected in seconds from a power generator of 214 components for 25 minutes including 20 minutes before the failure time. The failure time was predicted and detected 9 minutes 17 seconds before the failure time by PCA anomaly detection, but was not detected by the combination of LASSO and PCA because the target variable was binary variable which was assigned on the base of the failure time. CNN image classification with the train data of 10 normal status image and 5 failure status images detected just one minute before.