• Journal of the Korean Wood Science and Technology
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• v.28 no.2
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• pp.19-24
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• 2000

Effects of the cross-sectional dimension and moisture profile of wood specimens on the ultrasonic sound velocities of radiata pine heartwood and sapwood. Each moisture profile model specimen was made by composing five wood pieces with various moisture contents. As the cross-sectional dimensions decreased the ultrasonic velocities of both heartwood and sapwood decreased by 4~8%. In the ultrasonic signals transmitted through the specimens low frequency components more dominated than high frequency components as the dimension of cross section increased. The specimens with the same average MCs and different moisture profiles showed different ultrasonic velocities. By plotting the ultrasonic velocities against the average moisture contents of the inner three pieces of the moisture profile model specimens it was revealed that three distinct plot patterns existed.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.5
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• pp.510-519
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• 2009

Ship structure is composed of the welded mixture members which are plate and stiffeners. Ship structure is also influenced by variable loadings such as wave and inertia load. There have been several fatigue damage problems on the connection between longitudinal and transverse web due to wide usage of high tensile steel and adoption of wide web space to improve shipbuilding productivity. It is impossible to estimate the fatigue lives for all connection details through refined fatigue analysis. It is necessary to use the simplified approach for the fatigue life estimation of the connection details. PLUS analysis, which is suggested by the classification society, is one of the simplified approaches and is widely adopted to get fatigue lives for the connection details along whole cargo hold area. However, ship building yards still have difficulties to get fatigue lives due to large amount of calculation and time even if this approach reduce the time and amount of calculation. This paper treats the computing system developed to reduce efforts of estimating the fatigue lives. The influence factors of mean shear stress and local dynamic pressure are easily calculated and fatigue lives for all hot spots can be estimated automatically by the developed computing system. It is possible to reduce computing time and efforts to get the fatigue lives for the connection details between longitudinals and transverse webs along the ship. This system was applied to get fatigue lives on the connection details of a VLCC and verified the availability.

• The Korean Journal of Community Living Science
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• v.24 no.3
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• pp.343-354
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• 2013

Elderly people living in poverty are one of the most vulnerable population groups who are at risk of experiencing social exclusion. Social participation is an important contributing factor to active aging and social integration of the older adults living in poverty. This study aims to identify factors affecting social participation of the poor elderly. Data from the second wave of the Korean Longitudinal Study of Ageing was used for the analyses and 1,346 poor elderly aged over 65 were analyzed. The findings showed that age, education, health status, a level of depression, financial stress, and economic activity were associated with the social participation of the elderly living in poverty. These results indicated that psychological empowerment and specific needs of the older adults living in poverty should be considered in developing services and programs to promote social participation of the poor elderly.

• Advances in materials Research
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• v.12 no.4
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• pp.309-330
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• 2023

The humid thermal vibration characteristics of a nonhomogeneous thermopiezoelectric nonlocal plate of polygonal shape are addressed in the purview of generalized nonlocal thermoelasticity. The plate is initially stressed, and the three-dimensional linear elasticity equations are taken to form motion equations. The problem is solved using the Fourier expansion collocation method along the irregular boundary conditions. The numerical results of physical variables have been discussed for the triangle, square, pentagon, and hexagon shapes of the plates and are given as dispersion curves. The amplitude of non-dimensional frequencies is tabulated for the longitudinal and flexural symmetric modes of the thermopiezoelectric plate via moisture and thermal constants. Also, a comparison of numerical results is made with existing literature, and good agreement is reached.

• Journal of Ocean Engineering and Technology
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• v.15 no.3
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• pp.81-86
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• 2001

Ultrasonic travel-times obtained with the LCR ultrasonic technique have shown an ability to distinguish among three aluminum plates. The 244$\times$150mm thick, but differ in heat treatment. One is fully annealed, the second is quenched and then tempered, and the third is heat-treated to T651 plate, as received plate. Travel-times were obtained at four locations on each side of all plates. The data for both sides of each plate clearly are in very close agreement except location 1 of each plate. In order to show travel-time variation throughout the plate areas, the average travel-time for both sides of each plate were calculated. For Plate 1, the travel-time data were the highest and the data of Plate, the travel-time data were the highest and the data of Plate 2 were upper than Plate 3. Finally, the residual stresses for each plate were measured by X-ray diffraction method. The results showed a good relation. These preliminary results indicate that the LCR Ultrasonic Technique may be not only further developed for use in quality control in the manufacture of rolled aluminum plates but also industry.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3B
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• pp.315-324
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• 2010

We developed a design chart for very large floating structures through intensive hydroelastic analysis. Using this chart, one can predict the hydroelastic response of very large floating structures preliminarily at design stage without the cost-demanding hydroelastic analysis. This paper presents two new design charts based on the theory of VLFS. The purpose of the first design chart is to determine RAOs of the maximum longitudinal stress of VLFS considering properties of waves and structures. The design chart I can be applied to any sizes of VLFS in same aspect ratios and dimensionless stiffness parameters. The second design chart is developed to take into account the actual wave condition by using the Bretschneider spectrum with Beaufort sea state.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.4
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• pp.345-351
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• 2010

The oblique incidence technique for ultrasonic nonlinear characterization was studied in stainless steel 316L alloy subjected to high cycle fatigue. A dog-bone plate specimen was prepared to make different faitgue-driven deformation at each position where the stress concentration could occur in the middle of specimen. In addition to the normal transmission technique, the oblique incidence technique which is newly suggested in this study, was used to measure ultrasonic nonlinear parameter. The fatigued specimen shows higher ultrasonic nonlinear parameter than the virgin specimen for both techniques. Ultrasonic nonlinear parameter highly increases in the middle of test specimen where the stress concentration existes. Relative nonlinear parameter has strong correlation with fatigue damage. Consequently, the oblique incidence technique with longitudinal wave can be potential to characterize high cycle fatigue damage.

• 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.

• Journal of the Korean Wood Science and Technology
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• v.18 no.3
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• pp.53-68
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• 1990

This research has been executed for maximization of lumber yield and more efficient use of small diameter logs. Sample logs from thinnings carne from densed artificial stands at the Kwangnung Experimental Forests situated in the central region of Korean peninsula. Species of sample logs were obtained to execute sawing and strength test for larch, and lumber strength test in full size for pitch pine and Korean pine. A survey on sawmills consuming domestic logs was carried out to know sawmill production, costs and utilization structure of lumber as a guide to business analysis. Results showed that sawing pattern from small logs less than 15cm in diameter was necessary to cut 9cm by 9cm square per one log in order to obtain high lumber recovery and provide for wide market needs. The total lumber yield of squares plus side boards was 56 percent to 58 percent from small logs and the yield for log sweep in 30 percent decreased by 24.5 percent in sawing production, compared to yield for straight logs. In sawing efficiency, production of lumber by twin band saw could be improved 238 percent higher than lumber of the same species produced by conventional sawmilling methods, and sawing accuracy with twin band saw was much higher at the lumber production than band saw. Lumber from the small larch logs has shown 70 knots per $m^2$ on its faces and also lumber showed lots of face checkings by air drying on the yard, compared to other species. MOR in bending of lumber in full size from small logs of larch was found ranging from 380kg/$cm^2$ to 460kg/$cm^2$, resulting in 40 percent less than the strength from clear small specimens. In lumber containing knots, cross grain, etc, longitudinal stress wave speed was delayed about 48 percent by defects in lumber from both larch and pitch pine logs. The surveyed sample sawmills consumed the domestic logs at the rate of 54 percent to 84 percent in the total timber consumption, showing high consumption at mills located in the mountains.

• Geomechanics and Engineering
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• v.22 no.4
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• pp.291-303
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• 2020

The deformation of the rock surrounding a tunnel manifests due to the stress redistribution within the surrounding rock. By observing the deformation of the surrounding rock, we can not only determine the stability of the surrounding rock and supporting structure but also predict the future state of the surrounding rock. In this paper, we used grey system theory to analyse the factors that affect the deformation of the rock surrounding a tunnel. The results show that the 5 main influencing factors are longitudinal wave velocity, tunnel burial depth, groundwater development, surrounding rock support type and construction management level. Furthermore, we used seismic prospecting data, preliminary survey data and excavated section monitoring data to establish a neural network learning model to predict the total amount of deformation of the surrounding rock during tunnel collapse. Subsequently, the probability of a change in deformation in each predicted section was obtained by using a Bayesian method for detecting change points. Finally, through an analysis of the distribution of the change probability and a comparison with the actual situation, we deduced the survey mark at which collapse would most likely occur. Surface collapse suddenly occurred when the tunnel was excavated to this predicted distance. This work further proved that the Bayesian method can accurately detect change points for risk evaluation, enhancing the accuracy of tunnel collapse forecasting. This research provides a reference and a guide for future research on the probability analysis of tunnel collapse.