• 대한물리의학회지
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• 제13권3호
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• pp.75-80
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• 2018

PURPOSE: Scapular stability is very important to arm function during activities of daily living. The push-up plus exercise is commonly used to stabilize the shoulder muscles. In the present study, we designed an elastic shoulder band (ESB) that could be used with the push-up plus exercise and studied muscle activities of the serratus anterior (SA) and the lower and the upper trapezius (LT and UT) on stable and unstable support. METHODS: Fifteen healthy people participated in this study. Three muscles were investigated using surface EMG with and without the ESB on stable and unstable support. All subjects performed each trial three times for 7 seconds per set and rested for 30 seconds. Repeated one-way ANOVA was used for statistical analyses. RESULTS: The EMG activity of the SA was significantly different during the push-up plus exercise on stable support with the ESB compared with that on unstable support without the ESB (p<.05). However, there were no differences in the activities of UT and LT on stable and unstable support (p>.05). CONCLUSION: The ESB was effective for the activity of SA during the push-up plus exercise on stable support; therefore, it has the potential for use by people during push-up plus exercises. However, further studies are required to investigate the rehabilitation tools for patients with shoulder instability.

• Geomechanics and Engineering
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• 제22권6호
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• pp.475-488
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• 2020

The recent increase in the use of Expanded Polystyrene (EPS) geofoam in construction and geotechnical projects has driven researchers to investigate its behavior, more deeply. In this paper, a series of experimental tests to investigate the stress-strain behavior and the mechanical properties of EPS blocks, under monotonic axial loading are presented. Four different densities of cylindrically shaped EPS with different dimensions are used to investigate the effects of loading rate, height and diameter, as well as the influence of the density of EPS on the stress-strain response. The results show that increasing the height of the EPS samples leads to instability of the sample and consequent lower resistance to the applied pressure. Large EPS samples show higher Young's modulus and compressive resistance due to some boundary effects. An increase in the rate of loading can increase the elastic moduli and compressive resistance of the EPS geofoam samples, which also varies depending on the density of the samples. It was also determined that the elastic modulus of EPS increases with increasing EPS density. By implementing an efficient numerical procedure, the stress-strain response of EPS geofoam samples can be reproduced with great accuracy. The numerical analysis based on the proposed method can used to evaluate the effect of different factors on the behavior of EPS geofoam.

• 한국해양공학회지
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• 제15권3호
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• pp.75-80
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• 2001

The elastic plastic fracture toughness of this material is evaluated by the an unloading compliance method according to the ASTM E813-97 and E1152-97 method on the smooth and side groove 1CT specimens. The effect of smooth and side groove is studied on the material tearing modulus and characterizes the crack tip field under the plane stress and strain. SG-365 steel is observed that J-R curve and Tmat value decrease as 0%, 20%, 30%, and 40%. The 40% side grooved specimen is very useful in estimation of the $J_IC$. Because it is much easier than the smooth specimen to the onset of the ductile tearing by the R curve method. Besides. it improves the accuracy of toughness values, decreases the scattering the them and tunneling and shear lip by the side groove. Applicability of tearing modulus($T_J$ proposed by paris et al as instability panameter for this material is investigated.

• 한국유체기계학회 논문집
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• 제5권3호
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• pp.7-14
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• 2002

A new foil bearing, ViscoElastic Foil Bearing(VEFB) is suggested with the need for a high damping foil bearing. Sufficient damping capacity is a key technical hurdle to super-bending-critical operation as well as widespread use of foil bearings into turbomachinery. The super-bending-critical operation of the conventional bump foil bearing and the VEFB is examined, as well as the structural dynamic characteristics. The structural dynamic test results show that the equivalent viscous damping of the VEFB is much larger than that of the bump bearing, and that the structural dynamic stiffness of the VEFB is comparable or larger than that of the bump bearing. The results of super-bending-critical operation of the VEFB indicate that the enhanced structural damping of the viscoelastic foil dramatically reduces the vibration near the bending critical speed. With the help of increased damping resulting from the viscoelasticity, the suppression of the asynchronous orbit is possible beyond the bending critical speed.

• 한국해안해양공학회지
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• 제13권4호
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• pp.290-295
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• 2001

해저파이프라인은 부식. 지반 불안정, 앵커 충돌 등으로 인해 파손될 가능성이 있다. 해저파이프라인의 안정성을 위협하는 주된 요소중의 하나는 자유경간이다. 본 논문에서는 자유경간을 형성하고 있는 해저파이프라 인에 대해 축방향 하중을 고려하고 경계조건을 일반화시킨 경우에 대해 동적 자유경간의 허용길이 변화를 해석하였다. 자유경간 양단의 해저지반은 탄성기초로 간주하였으며, 이를 선형 및 회전 스프링으로 치환하여 경계조건을 일반화시켰다. 동적 자유경간의 길이를 산정할 수 있는 무차원화 된 곡선을 얻었다. 이 곡선은 자유경간을 갖는 해저파이프라인의 설계에 유용하게 작용될 수 있음을 보여 주었으며 예제 연구를 통하여 그 적용방법을 소개하였다.

• Steel and Composite Structures
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• 제2권3호
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• pp.209-222
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• 2002

This paper describes the buckling phenomenon of a tubular truss with unsupported length through a full-scale test and presents a practical computational method for the design of the trusses allowing for the contribution of torsional stiffness against buckling, of which the effect has never been considered previously by others. The current practice for the design of a planar truss has largely been based on the linear elastic approach which cannot allow for the contribution of torsional stiffness and tension members in a structural system against buckling. The over-simplified analytical technique is unable to provide a realistic and an economical design to a structure. In this paper the stability theory is applied to the second-order analysis and design of the structural form, with detailed allowance for the instability and second-order effects in compliance with design code requirements. Finally, the paper demonstrates the application of the proposed method to the stability design of a commonly adopted truss system used in support of glass panels in which lateral bracing members are highly undesirable for economical and aesthetic reasons.

• Steel and Composite Structures
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• 제10권5호
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• pp.385-414
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• 2010

In current European Standard EN 1993, the moment-rotation characteristics of beam-to-column joints made from steel with a yield stress > 460MPa are obtained from elastic design procedures. The strength of the joint basic components, such as the column web subject to local transverse compression, is thus limited to the yield resistance rather than the plastic resistance. With the recent developments of higher strength steel grades, the need for these restrictions should be revisited. However, as the strength of the steel is increased, the buckling characteristics become more significant and thus instability phenomena may govern the design. This paper summarizes a comprehensive set of finite element parametric studies pertaining to the strength behaviour of high-strength steel unstiffened I-columns in transverse compression. The paper outlines the implementation and validation of a three-dimensional finite element model and presents the relevant numerical test results. The finite element predictions are evaluated against the strength values anticipated by the EN 1993 for conventional steel columns and recommendations are made for revising the specifications.

• 한국공간구조학회논문집
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• 제16권1호
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• pp.65-72
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• 2016

Aerodynamic performance of solar wing system has been evaluated through wind tunnel test. The test model has 12 panels, each supported by 2 cables. The panels were installed horizontally flat, and gaps between panels were set constant. Sag ratios of 2% and 5%, and wind directions between $0^{\circ}$ and $90^{\circ}$ were considered. Mass of test model was determined considering the mass of full scale model, and Froude number and Elastic parameter were satisfied by adjusting the mean wind speed. From the wind tunnel test, it was found that the aerodynamic performance of the solar wing system is very dependent on the wind directions and sag ratios. When the sag was 2%, the fluctuating displacements between the wind directions of $0^{\circ}$ and $30^{\circ}$ increase proportionally to the square of the mean wind speed, implying buffeting-like vibration and a sudden increase in fluctuating displacement was found at large mean wind speed for the wind directions larger than $40^{\circ}$. When the wind direction was larger than $60^{\circ}$, a sudden increase was found both at low and large mean wind speed. When the sag ratio is 5%, distribution of mean displacements is different from that of sag ratio of 2%, and the fluctuating displacements show very different trend from that of sag ratio of 2%.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제36권1호
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• pp.28-38
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• 2010

The factors influencing the relapse and recurrence of skeletal deformity after the orthognathic surgery include various factors such as condylar deviation, the amount of mandibular set-back, stretching force by the soft tissues and muscles around the facial skeleton. The purpose of this report is to recognize and analyze the possible factors of reoperation after orthognathic surgery, due to early relapses. Six patients underwent reoperation after the orthognathic surgeries out of 110 patients from 2006 to 2009 were included in this study. In most cases, clincal signs of the insufficient occlusal stability, anterior open bite, and unilateral shifting of the mandible were founded within 2 weeks postoperatively. Although elastic traction was initiated in every case, inadequate correction made reoperation for these cases inevitable. The chief complaints of five cases were the protruded mandible combined with some degree of asymmetric face and in the other one case, it was asymmetric face only. Various factors were considered as a major cause of post-operative instability such as condylar sagging, counter-clockwise rotation of the mandibular segment, soft tissue tension related with asymmetrical mandibular set-back, preoperatively existing temporomandibular disorder (TMD), poor fabrication of the final wafer, and dual bite tendency of the patients.

• 대한기계학회논문집A
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• 제21권2호
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• pp.245-251
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• 1997

The dynamic behavior of elastic columns under the action of the subtangential force is studied in this paper. The subtangential force is the combination of the tip mass dead load and pure follower thrust. In this study, the tip mass is assumed to be a rigid body rather than a point mass. The equations of motion are derived based on the extended Hamilton's principle and the finite element method. Then the equations of motion are trasformed into a dimensionless form, and several parameters are identified. It is found that the critical subtangential force can be changed subtangentially by considering the parameters related to tip mass. It is also shown that the nonconservativeness of the applied force has a significant effect on the type of instability. The influence of the self-weight of the column on the variation of the critical force is also investigated.