• Journal of the Korean Society of Safety
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• v.17 no.4
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• pp.189-195
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• 2002

The differential quadrature method (DQM) is applied to computation of the eigenvalues of out-of-plane bucking of curved beams. Critical moments including the effect of radial stresses are calculated for a single-span wide-flange beam subjected to equal and opposite in-plane bending moments with various end conditions, and opening angles. Results are compared with existing exact solutions where available. The differential quadrature method gives good accuracy even when only a limited number of grid points is used. New results are given for two sets of boundary conditions not previously considered for this problem: clamped-clamped and clamped-simply supported ends.

• Physical Therapy Korea
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• v.26 no.3
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• pp.32-41
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• 2019

Background: Limitations in hip flexion caused by tight hamstrings lead to excessive lumbar flexion and low back pain. Accordingly, many studies have examined how to stretch the hamstring muscle. However, no study has focused on the effect of hamstring eccentric exercise for tight hamstrings on trunk forward bending. Objects: We compared the short-term effect of hamstring eccentric exercise (HEE) and hamstring static stretching (HSS) on trunk forward bending in individuals with tight hamstrings. Methods: Thirty individuals with tight hamstrings participated in the study. The subjects were randomly allocated to either a HEE or HSS group. To determine whether the hamstrings were tight, the active knee extension (AKE) test was performed, and the degree of hip flexion was measured. To assess trunk forward bending, subjects performed the fingertip to floor (FTF) and modified modified Schober tests, and the degree of trunk forward bending was measured using an inclinometer. We used paired t-tests to compare the values before and after exercise in each group and independent t-tests to compare the two groups on various measures Results: The FTF test results were improved significantly after the exercise in both groups, and AKE for both legs increased significantly in both groups. There was no significant difference in the hip angles, mmS test results, or degree of trunk forward bending between groups after the exercise. No test results differed significantly between the two groups at baseline or after the exercise. Both groups increased hamstring flexibility and trunk forward bending. Conclusion: HSS and the HEE groups increased hamstring flexibility and trunk forward bending. However, HEE has additional benefits, such as injury prevention and muscle strengthening.

• Journal of the Korean Geotechnical Society
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• v.22 no.2
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• pp.5-17
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• 2006

In order to investigate the stabilizing effect of nails against sliding, a series of model tests were carried out. The apparatus of model test was designed to perform the model test of soil slope reinforced by nails. The instrumentation system was used to measure the deflection behavior of nails during slope failure. As a result of model tests, the quantity and the occurred position of the maximum bending stress are changed according to the area ratio and the inclination angles of nails. The maximum stabilizing effect against sliding of nails is presented at 0.7$\%$ of the area ratio because the biggest maximum bending stress occurs at this time. But, the stabilizing effect of nails decreases with more than 0.7$\%$ of the area ratio. In the same condition of the area ratio, the stabilizing effect of nails is excellent at -10$^{circ}$ of the inclination angles of nails. The sliding surface can be predicted on the basis of the position of the maximum bending stress in each nails. The shape and depth of sliding surface are changed according to the area ratio and the inclination angles of nails.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.11
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• pp.1765-1772
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• 1997

The layered composites have a character to change of structure stiffness with respect to the layup angles. The deformations in the fan-blades to be initially designed by considering efficiency and noise, etc., which arise due to the pressure during the fan operation, can make the fan inefficient. Thus, so as to minimize the deformations of the blades, it is needed to increase the stiffness of the blades. An investigation has been performed to develop the three dimensional layered composite shell element with the drilling degree of freedom and the optimization module for finding optimal layup angles with sensitivity analysis. And then they have been verified. In this study, the analysis model is engine cooling fan of automobile. In order to analyzes the stiffness of the composite fan blades, finite element analysis is performed. In addition, it is linked with optimal design process, and then the optimal angles that can maximize the stiffness of the blades are found. In the optimal design process, the deformations of the blades are considered as multiobjective functions, and this results minimum bending and twisting simultaneously.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.29 no.3
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• pp.1-11
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• 2023

Background: The aim of this study was to compare the effects of squat training on an unstable support surface with different knee flexion angles on the balance ability of normal adults balance ability. Methods: 41 university students in their 20s attending N University in Cheonan, Chungcheongnam-do were divided into a 45-degree knee-bending squat training group and a 90-degree knee-bending squat training group. The groups trained on an unstable support surface 20 minutes per day, 3 times a week, for a total of 4 weeks. Results: Changes in static balance ability were not significant within and between the groups for both the sway distance and sway area in the eyes open and eyes closed states (p<.05). The changes in dynamic balance ability were significant in the forward, leftward, and rightward angles in both groups at the limit of stability (p<.05), but not significant in the backward angle (p>.05), and the comparison between groups was not significant (p>.05). Conclusion: No significant difference between static balance-related variables within and between the groups was found. Significant changes in dynamic balance-related variables within the groups were found but not between the groups. Therefore, in future studies, it is considered necessary to study various ages and differentiated intervention periods, such as young adults and the population of elderly people, with sufficient intervention periods to affect balance ability.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.3
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• pp.313-318
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• 2012

In CANDU, feeder pipes supply heavy water to pressure tube and steam generator. Under service conditions, Flow-Accelerated Corrosion (FAC) produces local wall-thinning in the feeder pipes. The wall-thinning in these pipes affects the integrity of the piping system, as verified in previous research. This paper provides limit loads for wallthinned feeder pipes with $45^{\circ}$ and $60^{\circ}$ bend angles, and proposes an equation that predicts the limit loads for wallthinned feeder pipes with arbitrary bend angles. On the basis of finite element limit analyses, limit loads are obtained for wall-thinned feeder pipes under in-plane bending and internal pressure. There are two cases of in-plane bending: the in-plane closing direction and the in-plane opening direction. The material is considered the effect of the large deformation, so an elastic-perfectly-plastic material is assumed in the calculations.

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.1
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• pp.78-86
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• 1992

This paper aims at investigating the effect of steel ratio and the magnitude of edge-ratio on the mechanical characteristics of reinforced concrete ring sector plate. The influence of steel bars was taken into account by coupling stiffness matrix of the steel bar element with that of the concrete plate element without dealing with separate element of steel bar and by establishing the composite stiffness matrix, which leads to the desirable result which does not increase th number of element could be obtained. Through case studies with 6 cases various steel ratios in ring sector plate supported at four edges and 4 cases with different open angles, the influence of the steel ratio was examined. A numerical analysis to find out the effect of the steel ratio d ue to above mentioned cases was carried out by 4 boundary conditions ; all edges clamped (B.C-1), all edges simply supported (B.C-2), curvilinear two edges clamped and other edges free (B.C-3) and curvilinear two edges simply supported and other edges free(B.C-4). The main results obtained are summarized as follows : 1. The effect of steel ratio on the magnitude of lateral deflection and x-directional bending moment at the center of sector plate and the midpoint of outer and inner curvilinear edges is almost the same up to $30^{\circ}$ of open angle. Beyond $30^{\circ}$ of the angle, the larger the angle, the greater the effect of ratio. 2. In design works using balanced steel ratio, the effect of steel bar can be ignored. But for larger open angles, especially greater than $90^{\circ}$, it proves desirable to consider the effect of steel bar. 3. The effect of the arc length of center circle/straight edge on lateral deflection and bending moment is remarkable in B.C-2. For larger open angle, the effect is also noted except for B.C-3 which turn out hardly affected. 4. The effect of the radius of curvature/straight side length on lateral deflection and x-directional bending moment is noted in B.C-2. As open angle increases, B.C-1 and B.C-3 almost agree and B.C-2 approaches B.C-4.

• Journal of the Korean Society of Clothing and Textiles
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• v.45 no.1
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• pp.106-122
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• 2021

This study confirmed the mechanical properties of an auxetic re-entrant pattern prepared using 3D printing technology and its composite fabric with neoprene for the production of functional auxetic patterns/textiles for safety shoes. Samples were prepared by the tilt angle of a re-entrant pattern of 0°, 30°, 45°, 60° and 90°, and then analyzed using Poisson's ratio, bending, compression, and tensile properties. A 3D printed auxetic re-entrant pattern (3DP-RE) and its composite fabric (3DP-RE/NP) showed a negative Poisson's ratio in all tilting angles that indicated auxetic properties. The results of the bending property shown that strength of 3DP-RE/NP was 1.5 times lower than NP, but the strain improved 2.0 times. It was confirmed that the deformation of 3DP-RE/NP is possible with a low load. Each sample type of compression behavior indicated similar regardless of the tilting angles; in addition, the compression toughness of 3DP-RE/NP increased 1.2 times compared with NP. In the case of tensile properties, 3DP-RE and 3DP-RE/NP were affected by the tilting angle, samples with 90° (the opposite of load direction) showed best tensile property and toughness. 3DP-RE/NP indicated improved bending, compression, and tensile properties.

• Journal of the Korean Wood Science and Technology
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• v.29 no.3
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• pp.14-20
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• 2001

On the bending process, metal-strap plays an important role in dispersing the stress generated in wood. Therefore, the metal-strap has more influence on the property of bentwood materials. The effect of the metal-strap thickness for bentwood was examined. The effect of metal-strap on the bending properties of Korean red pine(Pinus densiflora Sieb. et Zucc.)was investigated in this research. The metal-strap thickness is divided into 4 kinds such as 1.0, 0.8, 0.6, 0.4 mm. The specimens were selected by grain such as annual ring angles, flat grain and half-edge grain specimens. As a result of this study, the bending ability of 1.0, 0.8 mm, thickness of half-edge grain specimens was better than flat grain specimens but the result of 0.6, 0.4 mm were reversed. The bending ability of half-edge grain was better than flat grain and the grade was higher. When the processed specimens were dried, the radius of curvature(ROC) was decreased became drying-stress was not perfectly dispersed. An optimum drying-condition would deminish this phenomenon.

• Journal of the Korean Society of Clothing and Textiles
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• v.42 no.4
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• pp.561-570
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• 2018

This study defined the changes of mechanical properties of silk fabric according to bias angles and investigated the influence of bias angles and fabric characteristics on hand value. For the experiments, 4 types of commercial silk plain weave fabrics were chosen. All fabrics had the same density, but different yarn characteristics. Fabric samples were cut into 12 different bias angles between $0^{\circ}$ and $165^{\circ}$ with $15^{\circ}$ gap and measured for tensile, shear, bending, surface properties by the KES-FB system. As a result, most mechanical parameters showed an asymmetry shape with $90^{\circ}$. The most flexible and easiest angles are $45^{\circ}$, $135^{\circ}$. Furthermore, the bias angles of silk fabrics were classified into three clusters with mechanical properties such as WT, 2HG, 2HG5, B, and SMD. The parameters according to fabric samples showed significant differences at WT, RT, B, 2HB, and MIU. It showed bigger effects as yarn fineness; in addition, twists were higher except RT. The results of hand value indicated that Koshi and Hari were highest with a bias angle of $75^{\circ}$; however, Shinayakasa was highest at bias angle of $45^{\circ}$. Finally, Shari was lowest at $45^{\circ}$.