• Journal of the Korea Institute of Military Science and Technology
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• v.4 no.1
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• pp.147-154
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• 2001

The underwater explosion shock test is performed for the evaluation of the shock-resistant capability which is a very critical factor considering the survivability of the battle ship. Some measured signals have impulsive noise and gaussian white noise because of the unstable power supply system and the transient movement of cables during the underwater explosion shock test. The advanced shock signal analysis method which remove the noise of measured signal using the threshold policy of the median filter and the orthogonal wavelet coefficients are proposed. It is verified that the signal-to-noise ratio was improved about 30㏈ by the numerical simulation.

• Journal of the Korean Society for Nondestructive Testing
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• v.1 no.1
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• pp.13-21
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• 1981

When we use the strain gauge in the high temperature water, lowering of insulation resistance between test material and gauge is the matter. The lowering makes the measurement unstable and is the primary factor of an error. This study devises the waterproofing method in empirically that has the best insulating property in the hot water($100^{\circ}C$), In this way, we can reach the conclusion that on the condition of a few hours we can measure precisely in the high temperature like normal temperature.

• Economic and Environmental Geology
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• v.33 no.2
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• pp.129-138
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• 2000

The various types of geohazards like landslides resulted from civil construction (i.e. highway construction) must of analysed considering all the possible influential factor systematically. Thus, by using GIS, slope stability can be evaluated, and it can be used as a data for further detailed investigation. So the aim of this study is to present a data for decision making in selecting suitable point for remediation. For analysing slope instability, through appropriate definition and classification, landslide mechanism must be understood. In building GIS model, the selection of appropriate factors and their rating system should be made. For this, the characteristics and the mechanism of landslide have to be understood. And suitable coverage should be chosen for the model considering the slope conditions. In this study, field investigation in lst and 2nd Section, Chung-ang highway was carried out. From the field data, GIS model on slope instability was created. 5 coverages were used for it. From the result of this study, 12 unstable sections were found out and more detailed investigation is needed there.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.13 no.1
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• pp.21-29
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• 2009

This paper treats the conditions for the existence and stability properties of stationary solutions of a predator-prey interaction with self and cross-diffusion. We show that at a certain critical value a diffusion driven instability occurs, i.e. the stationary solution stays stable with respect to the kinetic system (the system without diffusion) but becomes unstable with respect to the system with diffusion and that Turing instability takes place. We note that the cross-diffusion increase or decrease a Turing space (the space which the emergence of spatial patterns is holding) compared to the Turing space with self-diffusion, i.e. the cross-diffusion response is an important factor that should not be ignored when pattern emerges.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.485-488
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• 2001

This paper provides the result of analysis of the structure and I-V characteristics of D.C. 1500 V surge arresters which were installed in railway line currently. As Porcelain housed surge arresters have unstable elements such as exploding and dispersion, so it is thought that the system is protected more stably with replacement of polymer housing. The adoption of gap mitigates the voltage stress which is degradation factor of surge arresters and the research is needed to enhance the life characteristic in additive and manufacturing process. Therefore, it is thought that the research should be continued to develop homemade the surge arresters for D.C. railway line as well as transmission line.

• Proceedings of the KSR Conference
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• 2003.10b
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• pp.397-402
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• 2003

Infiltration of rainfall causes railway embankment to be unstable and may result in failure. Basic relationship between the rainfall and stability of railway embankment are defined to analyze the stability of embankment by rainfall. An experimental study for defining of infiltration rate of rainfall into slope is conducted in the lab. The results of Rainfall infiltration show that rainfall infiltration is not equal to infiltration as like reservoir because rate of rainfall infiltration is controlled by slope angle. Based on these results, boundary condition of rainfall is altered and various numerical analysis are performed. The variation of shear strength, the degree of saturation and pore-water pressure for railway slope during rainfall can be predicted and the safety factor of railway slope can be expressed as the function of rainfall amount, namely rainfall index. Therefore, it is judged that this rainfall index can be a good tool for the rail-transport operation control.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.2
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• pp.126-131
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• 2003

Convective instability driven by surface tension is analyzed in an initially quiescent water absorbing ammonia gas with heat transfer using the linear stability analysis. The propagation theory is adapted to find the critical conditions of the onset of Marangoni convection. In this theory, the solutal penetration depth is chosen as the length scale factor. The results show that the liquid layer becomes more stable with decreasing the Schmidt number and increasing the Lewis number. It is also found that there is a critical Biot number to make the liquid layer be most unstable, and there is a linear relationship between the thor-mal Marangoni number and the solutal Marangoni number.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.743-747
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• 2000

The coordinated mechanism of terrestrial vertebrates enables them to maneuver over all of the terrain conditions since they have a distinct ability to adapt to varying conditions. Their locomotions remain infinitely more advanced and elegant than that of present-day existing mechanical walking robots. However, the principles of existing walking robots are based more on technical rather than on biological concepts, yielding unstable locomotion with low speed. In order to apply these advanced biological phenomena to the mechanical design of 4-legged walking robot, modeling methods are introduced and mathematical equations are also introduced.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.247-249
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• 2011

Pre-foaming, one of the manufacturing way of foamed concrete, is influenced by foaming agent. When the foaming agent diluted with water, surface tension and viscosity are varied. Therefore, this study is reviewing the surface tension, viscosity and unit weight of foam by experimental factor such as foaming agent types(AES, AOS, VS FP) and foam agent dilution concentration (1, 3, 5%) and temperature of materials (5, 10, 20℃). As an expeimental result, the surface tension and viscosity slightly increased with increasing concentrations. Meanwhile, when increasing temperature, the viscosity has decreased. FP produce relatively stable foams only in case 3% or more, which produce unstable foams containing large amount of water content by decreasing only insignificant surface tension when diluted at concentration of 1%.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.155-160
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• 2001

This paper describes a probabilistic fracture mechanics (PFM) analysis based on Monte Carlo (MC) simulation. In the analysis of CANDU pressure tube, it is necessary to perform the PFM analyses based on statistical consideration of flaw generation time. A depth and an aspect ratio of initial semi-elliptical surface crack, a fracture toughness value, delayed hydride cracking (DHC) velocity, and flaw generation time are assumed to be probabilistic variables. In all the analyses, degradation of fracture toughness due to neutron irradiation is considered. Also, the failure criteria considered are plastic collapse, unstable fracture and crack penetration. For the crack growth by DHC, the failure probability was evaluated in due consideration of flaw generation time.