• Journal of Chest Surgery
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• v.42 no.2
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• pp.165-174
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• 2009

Background: With the advances of cardiac surgery, the demand for an artificial prosthesis has increased, and this has led to the development and utilization of diverse alternative materials. We conducted this research to improve an artificial prosthesis by examining the changes of the physical qualities, the pressure related tensile strength, the change in elasticity and the thermostability of a xenograft valve (porcine) and pericardium (bovine, porcine) based on the type of fixation liquid we used. Material and Method: The xenograft valves and pericardium were assigned into three groups: the untreated group, the fixed with glutaraldehyde (GA) group and the glutaraldehyde with GA+solvent such as ethanol etc. group. The surgeons carried out each group's physical activities. Each group's uniaxial tension and elasticity was measured and compared. Thermostability testing was conducted and compared between the bovine and porcine pericardium fixed with GA group and the GA+solvent group. Result: On the physical activity test in the surgeon's hand, no significant difference between the groups was sensed on palpation. For suture and tension, the GA+solvent group was slightly firmer than the low GA concentration group. In general, the circumferential uniaxial tension and elasticity of the porcine aortic and pulmonary valves were better in the fixed groups than that in the untreated group. There was no significant difference between the GA and GA+solvent groups (p>0.05). Bovine and porcine pericardium also showed no significant difference between the GA group and the GA+solvent group (p>0.05). When comparing between the groups for each experiment, the elasticity tended to be stronger in most of the higher GA concentration group (porcine pulmonary valve, porcine pericardium). On the thermostability testing of the bovine and porcine pericardium, the GA group and the G+solvent group both had a sudden shrinking point at $80^{\circ}C$ that showed no difference (bovine pericardium: p=0.057, porcine pericardium: p=0.227). Conclusion: When fixing xenograft prosthetic devices with GA, adding a solvent did not cause a loss in pressure-tension, tension-elasticity and thermostability. In addition, more functional solvents or cleansers should be developed for developing better xenografts.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.45 no.4
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• pp.381-388
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• 2019

Recently, the importance of individual skin characteristic is emphasized for customized beauty products. There are many studies on the concept of the syndrome differentiation, related to individual cosmetics in Korean Medicine. However, skin characteristic according to Yin deficiency syndrome (YDS), which is associated with aging, are yet to be clarified. The objective of this study was to evaluate the skin characteristic and questionnaire of female with YDS compare to with non-YDS. 218 healthy females between 40 and 59 years of age were assessed for the skin hydration, elasticity, brightness (L^* value), redness (a^* value), pore, pigmentation, wrinkle, and sebum by Corneometerr^®, Cutometerr^®, and Janus lll. Independent t-test showed lower hydration, lower elasticity, and higher redness in the YDS group compared to the non-YDS group (all p < 0.05). There was significant difference on the facial fever, insomnia, decreased amount of urine, and skin sensitive checklist. These results suggested that using the questionnaire associated with YDS and skin characteristic could separate skin types and apply to customized beauty products.

• Advances in nano research
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• v.8 no.1
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• pp.13-24
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• 2020

In this paper, for the first time based on the nonlocal strain gradient theory the effect of size dependency in torsional vibration of bi-direction functionally graded (FG) nonlinear nano-cone is study. The material properties were assumed to vary according to the arbitrary function in radial and axial directions. The Navier equation and boundary conditions of the size-dependent bidirectional FG nonlinear nano-cone were derived by Hamilton's principle. These equations were solved by employing the generalized differential quadrature method (GDQM). The presented model can turn into the classical model if the material length scale parameters are taken to be zero. The effects of some parameters, such as inhomogeneity constant, cross-sectional area parameter and small-scale parameters, were studied. As an essential result of this study can be stated that an FG nano-cone model based on the nonlocal elasticity theory behaves softer and based on the strain gradient theory behaves harder.

• Journal of the Korean Society of Physical Medicine
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• v.15 no.4
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• pp.29-35
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• 2020

PURPOSE: This study examined the immediate effects of Graston instrument-assisted soft-tissue mobilization (GIASTM) and self-stretching on the muscular properties of the gastrocnemius in athletes. METHODS: Thirty subjects (All in their 20 s) were distributed randomly and evenly into two groups of 15 each: GIASTM and stretching. The subjects had no history of gastrocnemius damage in the previous three months. The muscle tone, stiffness, elasticity, and mechanical stress relaxation time (MSRT) of the gastrocnemius were blind-tested. RESULTS: The GIASTM group showed significant changes in all categories, while only MSRT changed significantly in the self-stretching group after intervention. A comparison of the two groups revealed significant differences in stiffness, elasticity, and MSRT (Time required for the muscle to recover after distortion after intervention in the GIASTM group. CONCLUSION: In this study, significant decreases in muscle tone and stiffness, as well as significant increases in elasticity, were observed in the gastrocnemius of the GIASTM group. On the other hand, sSelf-stretching showed significant differences in MSRT. Therefore, GIASTM is more effective in the recovery of the gastrocnemius muscle from fatigue than self-stretching. This study suggests that GIASTM can help prevent damage to the gastrocnemius in athletes and contribute to their training and rehabilitation programs.

• Journal of Industrial Convergence
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• v.18 no.5
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• pp.54-61
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• 2020

The purpose of this study was to understand the effect of job stress of female caregivers working in home-based elderly welfare centers on turnover intentions and to understand the moderating effect of self-elasticity in these relationships. The subject of the study was a self-written questionnaire survey of 170 nursing care workers at 28 home-based elderly welfare centers in Seoul, and 150 copies were collected and 133 people were finally analyzed excluding 17 unscrupulous responses. As a result of the study, first, the average value of turnover intention was high in the group with low experience of female caregivers at home-based elderly welfare centers and the group without religion. Second, the higher the job stress of nursing care workers, the higher the intention of turnover. Third, there was a moderating effect of self-elasticity between the job stress and the of turnover of nursing care workers. Therefore, it was necessary to consider measures to prevent job stress of nursing caregivers and improve self-resilience.

• Journal of the Korean Mathematical Society
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• v.52 no.6
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• pp.1195-1207
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• 2015

Lagrange multiplier method for solving the contact problem in elasticity is considered. Based on lower semicontinuity of sensitivity functional we prove the convergence of modified dual scheme to corresponding saddle point.

• Communications of the Korean Mathematical Society
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• v.34 no.4
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• pp.1353-1364
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• 2019

Modified Lagrange functional for solving an elastic problem with a crack is considered. Two formulations of a crack problem are investigated. The first formulation concerns a problem where a crack extending to the outer boundary of the domain. In the second formulation, we consider a problem with an internal crack. Duality ratio is established for initial and dual problem in both cases.

• Journal of Biosystems Engineering
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• v.30 no.2 s.109
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• pp.75-80
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• 2005

Mechanical characteristics of flower stalks (scapes) of garlic such as shear forces, cutting forces, and modulus of elasticities were investigated as a preliminary research to develop a mechanical harvester of garlic bulbils. The average shear forces of garlic scapes was 0.642 N and the maximum and minimum shear forces were 1.42 and 0.25 N, respectively. The shear forces generally increased as the diameter of garlic scapes increased. There was no correlation between the modulus of elasticity and the diameter of garlic scapes and the average modulus of elasticity of garlic scapes was around $2.40\times10^7\;N/m^2$ There was also no correlation between the cutting force and the diameter of garlic scapes. As the downward speed of blade increased, the cutting force of garlic scapes decreased and reversed to increase. The cutting forces of the lower part garlic scapes were lower than those of the upper part. The range of cutting forces of the lower and the upper part of garlic scapes were 3.88-4.04 N and 4.29-4.93 N, respectively.

• Structural Engineering and Mechanics
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• v.64 no.5
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• pp.591-610
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• 2017

This paper is concerned with the static analysis of variable thickness of two directional functionally graded porous materials (FGPM) circular plate resting on a gradient hybrid foundation (Horvath-Colasanti type) with friction force and subjected to compound mechanical loads (e.g., transverse, in-plane shear traction and concentrated force at the center of the plate).The governing state equations are derived in terms of displacements based on the 3D theory of elasticity, assuming the elastic coefficients of the plate material except the Poisson's ratio varying continuously throughout the thickness and radial directions according to an exponential function. These equations are solved semi-analytically by employing the state space method (SSM) and one-dimensional differential quadrature (DQ) rule to obtain the displacements and stress components of the FGPM plate. The effect of concentrated force at the center of the plate is approximated with the shear force, uniformly distributed over the inner boundary of a FGPM annular plate. In addition to verification study and convergence analysis, numerical results are displayed to show the effect of material heterogeneity indices, foundation stiffness coefficients, foundation gradient indices, loads ratio, thickness to radius ratio, compressibility, porosity and friction coefficient of the foundation on the static behavior of the plate. Finally, the responses of FG and FG porous material circular plates to compound mechanical loads are compared.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.4
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• pp.341-349
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• 2018

Recently, it has been reported that the whipping response, which is the elastic phenomenon of the ship, may be one of the causes of the ship accident. Unfortunately, the commonly used methodology for evaluating the whipping effect effectively has not been developed yet. In this study, we developed a procedure to estimate the whipping effect of hull in actual design stage. Fluid-structure interaction analysis was performed for a dominant short term sea state to obtain the time series data of vertical wave bending moment including the whipping response by slamming. In order to estimate the whipping effect by using the time series, some signal processing and statistical techniques such as low pass filtering, Weibull fitting and so on, were applied. the hydro-elasticity analysis was performed on container ships of various sizes to evaluate the whipping effect. The parameters that can affect the response of the hull vibration was selected and the effect of these parameters on whipping was analyzed.