• Smart Structures and Systems
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• 제29권3호
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• pp.395-420
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• 2022

A new hybrid quasi-3D and 2D high-order shear deformation theory is studied in this mathematical formulation, for an investigation of the bending, free vibrations and buckling influences on a functionally graded material plate. The theoretical formulation has been begun by a displacement field of five unknowns, governing the transverse displacement across the thickness of the plate by bending, shearing and stretching. The transverse shear deformation effect has been taken into consideration, satisfying the stress-free boundary conditions, especially on plate free surfaces as parabolic variation through its thickness. Thus, the mechanical properties of the functionally graded plate vary across the plate thickness, following three distributions forms: the power law, exponential form and the Mori-Tanaka scheme. The mechanical properties are used to develop the equations of motion, obtained from the Hamilton principle, and solved by applying the Navier-type solution for simply supported boundary conditions. The results obtained are compared with other solutions of 2D, 3D and quasi-3D plate theories have been found in the literature.

• Advances in nano research
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• 제12권2호
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• pp.117-137
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• 2022

Effect of thickness stretching on free vibration, bending and buckling behavior of carbon nanotubes reinforced composite (CNTRC) laminated nanoplates rested on new variable elastic foundation is investigated in this paper using a developed four-unknown quasi-3D higher-order shear deformation theory (HSDT). The key feature of this theoretical formulation is that, in addition to considering the thickness stretching effect, the number of unknowns of the displacement field is reduced to four, and which is more than five in the other models. Two new forms of CNTs reinforcement distribution are proposed and analyzed based on cosine functions. By considering the higher-order nonlocal strain gradient theory, microstructure and length scale influences are included. Variational method is developed to derive the governing equation and Galerkin method is employed to derive an analytical solution of governing equilibrium equations. Two-dimensional variable Winkler elastic foundation is suggested in this study for the first time. A parametric study is executed to determine the impact of the reinforcement patterns, nonlocal parameter, length scale parameter, side-t-thickness ratio and aspect ratio, elastic foundation and various boundary conditions on bending, buckling and free vibration responses of the CNTRC plate.

• Structural Engineering and Mechanics
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• 제85권6호
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• pp.765-780
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• 2023

In this work, a novel combined logarithmic, secant and tangential 2D and quasi-3D refined higher order shear deformation theory is proposed to examine the buckling analysis of simply supported uniform functionally graded plates under uniaxial and biaxial loading. The proposed formulations contain a reduced number of variables compared to others similar solutions. The combined function employed in this study ensures automatically the zero-transverse shear stresses at the free surfaces of the structure. Various models of the material distributions are considered (linear, quadratic, cubic inverse quadratic and power-law). The differentials stability equations are derived via virtual work principle with including the stretching effect. The Navier's approach is applied to solve the governing equations which satisfying the boundary conditions. Several comparative and parametric studies are performed to illustrates the validity and efficacity of the proposed model and the various factors influencing the critical buckling load of thick FG plate.

• PNF and Movement
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• 제17권3호
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• pp.487-497
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• 2019

Purpose: This tutorial review investigated the effect of prior fatigue and passive stretches on eccentric contraction-induced muscle injuries, as well as the underlying mechanisms of eccentric contraction-related injuries. Methods: Contraction-induced muscle damage is the most common disabling problem in sports and routines. The mechanisms underlying the pathology and prevention of muscle damage lessened by prior fatigue or stretches are critical in assessing musculoskeletal injuries. Even though there are treatments to reduce eccentric contraction-induced muscle injuries, fatigue negatively influences them. Therefore, we reviewed previous studies on eccentric contraction-induced muscle injuries with prior treatments using the MEDLINE and PubMed databases. Results: Prior passive stretching had a preventative and therapeutic effect, but prior lengthening contractions did not. On the other hand, prior isometric contractions involving relatively small forces may not provide a sufficient stimulus to induce protection. As a result, high force isometric contractions may be necessary. The studies supported the positive effects of prior fatigue, concluding that it was a factor in determining the amount of damage caused by eccentric exercise. This was due to a reduction in force and increased temperature. Studies that did not support the positive effects of prior fatigue concluded that a shift in optimal length to a longer length and reduced energy absorption during lengthening are evidence that fatigue is not related to muscle injuries induced by lengthening. Conclusion: The variability of the experiment models, conditions, muscles, and treatment methods make it necessary to interpret the conditions of previous studies carefully and draw conclusions without making direct comparisons. Thus, additional studies should be carefully conducted to investigate the positive effect of fatigue on lengthening.

• 대한물리치료과학회지
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• 제25권1호
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• pp.11-19
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• 2018

Purpose : The purpose of this study was to examine the effects of ankle kinesio taping on postural control function during exercise in university students. Method : Thirty subjects were randomly allocated to three groups: Y taping group (n=20), I taping group (n=20) and Non-taping group (n=20). All groups underwent the same exercise program including stretching for 30 minutes. The exercise program proceeded in the following order: five minutes of stretching, a 20-minutes exercise program, and additional five 5 minutes of stretching. Of the eight exercise methods suggested by Purcell et al, seven were chosen (lateral shuffle, forward & backward running, agility ladder, figure-of-8, forward jogging while jumping over cones, wall jumps and zigzags); $90^{\circ}$ cuts with lateral shuffle were omitted. The postural control functions was measured participants's perceptions of stability, confidence, and reassurance using methods suggested by Purcell et al,. Result : The confidence was significant difference in I taping group compared to Non taping group. The reassurance was significant difference in Y taping group and I taping group compared to Non taping group. Conclusion : The Kinesio taping increased confidence, and reassurance during exercise in university students. Additional research on Kinesio taping for improving range of motion and agility is need.

• 대한물리치료과학회지
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• 제16권1호
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• pp.11-20
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• 2009

Background: The purpose of this study was to investigate the effect of stretching and strengthening exercise on the static flexibility and pain intensity for the iliopsoas muscle, which is one of the main reasons for the chronic low back pain. Methods: The subjects of this study were 15 male adult patients with showed 6 score or higher in the visual analogue scale(VAS) and complained of low back pain over three months who visited department of the physical therapy, KIA motors Industrial Health Center, from October, 2008 through December, 2008. Fifteen subjects were trained stretching, mat exercises and sling exercises for iliopsoas muscle at 4-5 times a week for 4 weeks. I measured the changes on the extensibility of iliopsoas muscle, static flexibility of low back and VAS between pre- and post exercise treatment. Date were analyzed using the Wilcoxon's signed rank test considering the size of the samples. Results: 1. The angle of the hip joint that showed the extensibility of iliopsoas muscle was relieved, which was significant statistically (p<.05). 2. The static flexibility was statistically significantly improved in the trunk flexion test, trunk extension test and Schober-Test (p<.05). 3. The VAS showed decrease, which is significant statistically (p<.05). Conclusion: It is believed that the exercise treatment of iliopsoas muscle has the significant effects on the improvement of static flexibility and decrease of pain intensity for the chronic low back pain patients.

• 폴리머
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• 제36권5호
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• pp.606-611
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• 2012

Polyetherimide(PEI)와 poly(vinylidene flouride)(PVdF) 폴리머들을 블렌딩하여 전기방사를 통해 웹을 제조하였다. 낮은 기계적 물성을 증대시키기 위해서 압착과 연신이라는 후처리 공정을 이용하였으며 후처리 공정이 기계적 물성에 미치는 영향을 조사하였다. 물리적 특성을 확인하기 위해 SEM, 인장 시험 측정기를 이용하여 측정하였다. $180^{\circ}C$의 압착 온도에서 1/2, 1/3, 1/4, 1/5의 비율로 압착된 웹들은 초기 상태에 비해 대략 4~5배 가량 인장 강도가 증가하였으며, 이들을 $220^{\circ}C$의 온도에서 30~40% 연신함으로써 2~8MPa의 추가적인 인장 강도 증대를 보였다.

• Physical Therapy Rehabilitation Science
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• 제4권1호
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• pp.22-27
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• 2015

Objective: Jump training helps increase the muscle power by improving the muscle strength and reaction time of the muscle in operation. The purpose of this study was to identify the effects of strengthening, stretching exercise and meditation on electromyographic (EMG) onset timing of rectus femoris and gastrocnemius muscle during vertical jump performance. Design: Cross-sectional study. Methods: Ten healthy adults (5 male and 5 female) who were familiar with the vertical jumping task and had no lower extremity injuries or any bone or joint disorders, were recruited for this study. Muscle onset timing was measured by surface EMG. After EMG onset timing were measured during performing three baseline vertical jump trials, strengthening and stretching exercises of the rectus femoris and gastrocnemius, and meditation were performed in random order. EMG onset timing was measured during vertical jump after intervention, respectively. EMG value was averaged for the three trials and analyzed using one-way repeated ANOVA. Results: During vertical jump, EMG onset timing of gastrocnemius was a significant difference after intervention (p<0.05), and then there was significantly faster in strengthening exercise than meditation (p<0.05). Conclusions: These results indicate the potential positive effect of performing strengthening exercise of the gastrocnemius before a jumping event. Future research is required to identify the effects of intervention over a long period.

• 한국통신학회논문지
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• 제36권8B호
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• pp.979-985
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• 2011

오늘날 관계지수 또는 공존지수라 불리우는 NQ(Network Quotient)가 중요한 사회에 살면서 가장 중요한 것이 상대와의 대화가 되고 있다. 따라서 사회생활에 있어 정확한 발음을 구사하여 자신의 의견을 개진하고 의사 전달력을 극대화시키는 것이 대단히 중요한 항목이 되고 있다. 이를 위해 일상생활에서 자신의 의사 전달력을 높이기 위해 발음 체조 뿐 아니라 성대와 연계된 성대 반사점을 지압하는 행위 등 발음의 정확성을 향상시키고자 하는 노력이 이루어지고 있는 실정이다. 그러나 이런 노력들이 실제 정확한 발음을 향상시키는 역할을 하는지에 대한 객관화된 실증적 연구가 전무한 실정이었다. 따라서 본 논문에서는 IT 기술을 적용하여 발음 체조 등과 같은 방법들이 실제 발음 정확성의 향상에 도움이 되는지에 대한 효용성 입증 및 정량화를 위한 방법을 새롭게 제안하였다. 이를 위해 20대 남성 30명을 대상으로 성대 반사점 지압과 발음 체조를 수행하기 전과 후의 음성을 수집하여 음성 분석을 수행하였다.

• 융합정보논문지
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• 제9권12호
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• pp.184-189
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• 2019

본 연구의 목적은 뇌졸중 환자의 발목관절 가동범위를 증가시키기 위한 중재를 실시한 후 발목가동범위 변화를 비교한 것이다. 본 연구는 총 45명의 뇌졸중 환자를 경사대, PNF 스트레칭 그리고 관절가동술 방법에 따라 각 3군으로 나누어 8주간 실시한 후 발바닥 굽힘과 발등 굽힘을 측정하였다. 발바닥 굽힘은 집단 간에 차이가 유의하게 있었고(p<.001), 시기별 집단 간 차이에서도 차이가 유의하였다. 발등 굽힘은 관절가동술을 적용한 군 내에서 유의하게 증가하였으며(p<.05), 집단 간, 시기별 유의하였다(p<.05). 본 연구를 통해 발목의 가동범위를 증가시키기 위한 방법으로 스트레칭과 관절가동술이 효과가 있음을 알 수 있었다. 향후 연구에서는 뇌졸중 환자의 발목가동범위 증가가 미치는 또 다른 영향에 대한 연구가 있기를 기대한다.