• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.368-373
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• 2008

This paper describes the dynamic shock effects on the pretensioned concrete member by the detensioning using finite element analysis. The investigation was performed by linear and nonlinear dynamic analysis. In nonlinear dynamic analysis, Brittle Cracking Model was applied for concrete behavior. It was shown that the amplitude of stress wave was significantly decreased when time for cutting of tendon was above 0.05sec. The maximum stress values obtained from linear and nonlinear dynamic analysis was nearly same. However, the position forthe maximum tensile stresses were different.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.1
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• pp.63-77
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• 2015

Tsunami take away life, wash houses away and bring devastation to social infrastructures such as breakwaters, bridges and ports. The coastal structure targeted object in this study can be damaged mainly by the wave pressure together with foundation ground failure due to scouring and liquefaction. The increase of excess pore water pressure composed of oscillatory and residual components may reduce effective stress and, consequently, the seabed may liquefy. If liquefaction occurs in the seabed, the structure may sink, overturn, and eventually increase the failure potential. In this study, the bore was generated using the water level difference, its propagation and interaction with a vertical revetment analyzed by applying 2D-NIT(Two-Dimensional Numerical Irregular wave Tank) model, and the dynamic wave pressure acting on the seabed and the surface boundary of the vertical revetment estimated by this model. Simulation results were used as input data in a finite element computer program(FLIP) for elasto-plastic seabed response. The time and spatial variations in excess pore water pressure ratio, effective stress path, seabed deformation, structure displacement and liquefaction potential in the seabed were estimated. From the results of the analysis, the stability of the vertical revetment was evaluated.

• Structural Engineering and Mechanics
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• v.3 no.4
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• pp.391-410
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• 1995

The application of adaptive finite element method to dynamic problems is investigated. Both the kinetic and strain energy errors induced by space and time discretization were estimated in a consistent manner and controlled by the simultaneous use of the adaptive mesh generation and the automatic time stepping. Also an optimal ratio of spatial discretization error to temporal discretization error was discussed. In this study it was found that the best performance can be obtained when the specified spatial and temporal discretization errors have the same value. Numerical examples are carried out to verify the performance of the procedure.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.539-544
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• 2001

The holographic measurement techniques can be applied to various industrial fields such as automobile, airplane, construction, electronics, medical, mechanics and physics. The visualization of fluids is very important in aerodynamics, heat transfer and stress analysis. There are classically optical methods such as shadowgraph, schlieren method, and Mach-Zehnder interferometry for visualizing the fluid flow phenomena. But, it is difficult to understand the continuous state of fluids well in those methods. In this study, the real-time holographic interferometer with high-speed camera is applied to the flow visualization. In addition, collimated laser beam and rotating wedge are used for recording and formation of carrier fringes, respectively.

• Korean Journal of Family Social Work
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• no.62
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• pp.39-69
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• 2018

Women with children suffer from double burden of childcare and household labor. Based on the framework of social determinants of mental health, this study investigated the moderated mediation effect of income in the relationship between time poverty and mental health among women with children. The study sample included 1,505 women from the $6^{th}$ wave of Korean Longitudinal Survey of Women and Families (KLoWF). Results showed that the lower level of time poverty was associated with decreased stress and depression, and stress mediated the relationship between time poverty and depression. Income had a moderated mediation effect in the relationship between time poverty, stress, and depression. Time poor women were more vulnerable to poor mental health, and income buffered the effect of time poverty on women's mental health. This implies that women in the lower end of socioeconomic ladder are more prone to the effect of time poverty. The study speaks to the importance of social factors on mental health which has usually been considered an individual problem. Policies and services need to address women's working conditions and income security in order to increase their mental health.

• Korea-Australia Rheology Journal
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• v.14 no.1
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• pp.33-45
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• 2002

Recent results obtained for the port-pom model and the constitutive equations with time-strain separability are examined. The time-strain separability in viscoelastic systems Is not a rule derived from fundamental principles but merely a hypothesis based on experimental phenomena, stress relaxation at long times. The violation of separability in the short-time response just after a step strain is also well understood (Archer, 1999). In constitutive modeling, time-strain separability has been extensively employed because of its theoretical simplicity and practical convenience. Here we present a simple analysis that verifies this hypothesis inevitably incurs mathematical inconsistency in the viewpoint of stability. Employing an asymptotic analysis, we show that both differential and integral constitutive equations based on time-strain separability are either Hadamard-type unstable or dissipative unstable. The conclusion drawn in this study is shown to be applicable to the Doi-Edwards model (with independent alignment approximation). Hence, the Hadamardtype instability of the Doi-Edwards model results from the time-strain separability in its formulation, and its remedy may lie in the transition mechanism from Rouse to reptational relaxation supposed by Doi and Edwards. Recently in order to describe the complex rheological behavior of polymer melts with long side branches like low density polyethylene, new constitutive equations called the port-pom equations have been derived in the integral/differential form and also in the simplifled differential type by McLeish and carson on the basis of the reptation dynamics with simplifled branch structure taken into account. In this study mathematical stability analysis under short and high frequency wave disturbances has been performed for these constitutive equations. It is proved that the differential model is globally Hadamard stable, and the integral model seems stable, as long as the orientation tensor remains positive definite or the smooth strain history in the flow is previously given. However cautious attention has to be paid when one employs the simplified version of the constitutive equations without arm withdrawal, since neglecting the arm withdrawal immediately yields Hadamard instability. In the flow regime of creep shear flow where the applied constant shear stress exceeds the maximum achievable value in the steady flow curves, the constitutive equations exhibit severe instability that the solution possesses strong discontinuity at the moment of change of chain dynamics mechanisms.

• Ecology and Resilient Infrastructure
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• v.5 no.4
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• pp.219-228
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• 2018

This study measured the Physiological Equivalent Temperature (PET) of the hottest day time in a day, in order to verify the characteristics of human thermal comfort in case of heat wave during summer time in each region, by subdividing the urban areas in accordance with the climatic characteristics with the use of Local Climate Zone (LCZ) as a method of classifying the type of urban climate and the land cover map, targeting the Homaesil residential development district in Suwon. In the results of measurement, the forest and paddy field showed the moderate heat stress while the urban park showed the strong heat stress. Other developed areas showed the extreme heat stress. Such results show the possibility of institutional utilization for the improvement of human thermal comfort through the verification of climatic characteristics and differences in each type of urban areas, and the efficient placement of green infrastructure and the planning of land use to cope with the heat wave even in the planning stage for the establishment of urban planning.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.22 no.2
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• pp.79-85
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• 1989

The generation and propagation of shelf wave-like oscillations induced by local wind at a basin with continental shelf and slope are studied by a numerical experiment. Three types of vortices are generated along western boundary and they propagate along the boundaries in the counter-clockwise direction. The first vortex is generated at the early stage of wind stress and its center is located off the continental slope. The second type centered on the continetal slope is generated at about the terminating time of wind stress and follows the first one. The third, centered on continental shelf, decays so soon that its propagation pattern is hard to be identified. Each of those vortices is probably to be one of free modes of the model basin.

• Korean Journal of Social Welfare
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• v.64 no.4
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• pp.285-310
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• 2012

This study examined the causal relationship of between stressors and depression using the wave 1~4 of Korean Welfare Panel Study by social stress theory. According to the result, the level of depression and depressed group was decreased in the course of time. As a panel regression analysis, Factors affecting the reduction of depression was upward of the income hierarchy, increase the satisfaction of family and social relationships, and residential satisfaction. Based on the results, the author suggested that social work policies and intervention direction should decrease social stress factors with causality to depression of the men in baby boom generation.

• Proceedings of the Korean Geotechical Society Conference
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• 1995.10a
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• pp.15.2-22
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• 1995

Evaluating stiffness of near-surface materials has been one of the critically important tasks in many civil engineering works. It is the main goal of geotechnical characterization. The so-called deflection-response method evaluates the stiffness by measuring stress-strain behavior of the materials caused by static or dynamic load. This method, however, evaluates the overall stiffness and the stiffness variation with depth cannot be obtained. Furthermore, evaluation of a large-area geotechnical site by this method can be time-consuming, expensive, and damaging to many surface points of the site. Wave-propagation method, on the other hand, measures seismic velocities at different depths and stiffness profile (stiffness change with depth) can be obtained from the measured velocity data. The stiffness profile is often expressed by shear-wave (S-wave) velocity change with depth because S-wave velocity is proportional to the shear modulus. that is a direct indicator of stiffiiess. The crosshole and downhole method measures the seismic velocity by placing sources and receivers (geophones) at different depths in a borehole. Requirement of borehole installation makes this method also time-consuming, expensive, and damaging to the sites. Spectral-Analysis-of-Surface-Waves (SASW) method places both source and receivers at the surface, and records horizontally-propagating surface waves. Based upon the theory of surfacewave dispersion, the seismic velocities at different depths are calculated by analyzing the recorded surface-wave data. This method can be nondestructive to the sites. However, because only two receivers are used, the method requires multiple measurements with different field setups and, therefore, the method often becomes time-consuming and labor-intensive. Furthermore. the inclusion of noise wavefields cannot be handled properly, and this may cause the results by this method inaccurate. When multi-channel recording method is employed during the measurement of surface-waves, there are several benefits. First, usually single measurement is enough because multiple number (twelve or more) of receivers are used. Second, noise inclusion can be detected by coherency checking on the multi-channel data and handled properly so that it does not decrease the accuracy of the result. Third, various kinds of multi-channel processing techniques can be applied to f1lter unwanted noise wavefields and also to analyze the surface-wavefields more accurately and efficiently. In this way, the accuracy of the result by the method can be significantly improved. Fourth, the entire system of source, receivers, and recording-processing device can be tied into one unit, and the unit can be pulled by a small vehicle, making the survey speed very fast. In all these senses, multi-channel recording of surface waves is best suited for a routine method for geotechnical characterization in most of civil engineering works.