• Journal of Industrial and Engineering Chemistry
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• 제68권
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• pp.238-245
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• 2018

The skin experiences constant physical stimuli, such as stretching. Exposure to excessive physical stimuli stresses the skin and can accelerate aging. In this study, we applied a method that allowed human fibroblasts and keratinocytes to be perfused with media to form 3D skin equivalents that were then uniaxially 10%-stretched for 12 h per day (at either 0.01 or 0.05 Hz) for up to 7 days to form wrinkled skin-on-a-chip (WSOC). There was more wrinkling seen in skin equivalents under 0.01 Hz uniaxial stretching than there was for non-stretched skin equivalents. At 0.05 Hz, the stratum corneum almost disappeared from the skin equivalents, indicating that stretching was harmful for the epidermis. At both frequencies, the production of collagen and related proteins in the skin equivalents, such as fibronectin 10 and keratin, decreased more than those in the non-stretched equivalents, indicating that the dermis also suffered from the repeated tensile stress. These results suggest that WSOCs can be used to examine skin aging and as an in vitro tool to evaluate the efficacy of anti-wrinkle cosmetics and medicines.

• The Journal of Korean Physical Therapy
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• 제30권1호
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• pp.23-28
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• 2018

Purpose: This study examined the effectiveness of iliopsoas self-stretching on the hip extension angle, gluteus maximus (GM) activity, and pelvic compensated angle during prone hip extension (PHE) in subjects with iliopsoas shortness. Methods: Twenty-healthy subjects with iliopsoas shortness were recruited. Electromyography (EMG) was used to examine erector spinae (ES), multifidus (MF), GM, and biceps femoris (BF) while performing PHE. An electromagnetic tracking motion analysis device was used to measure the pelvic compensations. The pelvic compensations while performing PHE were considered to be anterior tilting and rotation. A modified Thomas test was used to monitor the hip extension angle before and after iliopsoas self-stretching. A paired t-test was used to investigate the significant difference after iliopsoas self-stretching during PHE. The level of statistical significance was set to ${\alpha}=0.05$. Results: Muscle activity of GM and hip extension angle were significantly greater after iliopsoas self-stretching compared to that before iliopsoas self-stretching during PHE (p<0.05). BF and pelvic rotation angle were significantly lower after iliopsoas self-stretching compared to that before iliopsoas self-stretching during PHE (p<0.05). The muscle activity of ES was not significantly different between PHE before and after iliopsoas self-stretching (p>0.05). Conclusion: Iliopsoas self-stretching can be effective in selectively strengthening the GM muscles with minimized pelvic compensation in subjects with iliopsoas shortness.

• 대한물리의학회지
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• 제18권4호
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• pp.77-87
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• 2023

PURPOSE: The purpose of this study was to investigate the changes in the flexibility and elasticity of the muscles when the hamstrings were stretched in one direction and when they were stretched in three directions. METHODS: In this study the subjects were divided into two groups, namely the 'one-direction stretching exercise of the hamstring muscle in the neutral position' group (female: 14 people, male: 14 people) and the 'three-way stretching exercise' group (female: 12 people, male: 14 people) considering the positions of the three hamstring muscles. The elasticity and flexibility of the hamstring muscles were measured before and after the self-extension exercise, and the average value of two measurements was noted. To evaluate the flexibility of the hamstring muscle, a 'sit and reach' test was performed, and muscle elasticity was measured using the MyotonPRO® device. RESULTS: After the stretching exercise, flexibility increased in both groups. In terms of muscle elasticity, the body dynamic strength and resonance frequency of the stretching one-direction stretching group decreased after the stretching exercise. CONCLUSION: To alter the muscle characteristics and increase the flexibility when performing a stretching exercise, selecting and stretching only one muscle with the lowest range of motion yields effective results. The ideal technique to be employed appears to be to stretch the entire hamstring muscle in one direction from the neutral position.

• 대한물리의학회지
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• 제17권3호
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• pp.79-86
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• 2022

PURPOSE: By virtue of its location, the iliopsoas muscle has the potential to affect the function of the diaphragm. Therefore, the purpose of this study was to investigate the effects of passive stretching of the iliopsoas muscles on pulmonary function. METHODS: Twenty male university students participated in this study. Subjects with low back pain, negative results on the modified Thomas test, and chest breathing patterns not directly related to the function of the iliopsoas muscles were excluded from this study. A digital pulmonary function measuring device (Pony FX, COSMED Inc, Italy) was used to test pulmonary function. The test was performed three times: the first test before passive stretching, the second test 10 minutes after the first test, and the third after passive stretching. Passive stretching was performed 5 times for each of the left and right iliopsoas muscles. Passive stretching was carried out for 20 seconds followed by a 10-second break. The SPSSWIN (ver. 27.0) statistics program was used for data analysis, and the significance level was α =.05. RESULTS: Among slow vital capacity (SVC) parameters, tidal volume (VT), inspiratory reserve volume (IRV), inspiratory capacity (IC) and vital capacity (VC) improved significantly after passive stretching. Also, among the maximal effort vital capacity (MEVC) parameters, forced vital capacity(FVC) and forced expiratory volume in one second(FEV1) improved significantly after passive stretching. CONCLUSION: The results showed that among the various pulmonary function parameters measured, passive stretching of the iliopsoas muscles can improve the SVC and MEVC. Therefore, passive stretching of the iliopsoas muscles may be considered for use as a treatment method to improve pulmonary function.

• 대한물리의학회지
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• 제5권4호
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• pp.667-674
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• 2010

Purpose : The purpose of this study was to investigate the effect of motion-based game exercise program and stretching exercise program on static and dynamic standing balance in elderly women. Methods : Subjects participated in the exercise program was 40 eldery women took part in this study. The average age of the elderly was 70.60 years. All subjects could walk without an assistive device. All subjects were participated in this study during 4 weeks(3 days per week, 30min/day). All participants were assessed on berg balance scale(BBS), functional reach test(FRT), timed up&go test(TUG). Results : The data were analyzed using paired t-test. After 4 weeks exercise training, the result of this study were as follows: The BBS of the elderly was significant difference between test-retest(p<0.05). The TUG of the elderly were significant difference between test-retest(p<0.05). The Motion-Based game from FRT of the was more significant difference than stretching exercise program(p<0.05). we also found significant differences for both groups FRT scores, and changes in mean BBS, TUG scores, but BBS, TUG were not significant. Conclusion : We findings suggest that elderly women person could improve their standing balance through Motion-Based game exercise program, and stretching exercise program.

• 대한물리의학회지
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• 제7권4호
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• pp.509-514
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• 2012

PURPOSE: This study aims to compare the effects of upper backbone joint mobilization and self-stretching exercise in the patients with chronic neck pain. METHODS: Thirty seven patients with chronic neck pain were divides into self stretching group(SSG, n=18) and mobilization group(MG, n=19). To assess the degree of neck pain, the visual analog scale (VAS) was utilized, and to measure the joint range of motion at the flexion-extension, it was compared and analyzed by using the cervical range of motion (CROM) device. RESULTS: The joint range of motion and visual analog scale of SSG and MG showed significant effects on both groups. In the comparison of groups, there was no significant difference, but it indicated effects on improving the pain and the range of joint motion in MG. CONCLUSION: According to the analysis, not only self-stretching exercise intervening for direct treatment but also upper backbone joint mobilization intervening for indirect treatment are effective to improve the pain and the range of motion.

• 대한기계학회논문집A
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• 제33권7호
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• pp.629-636
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• 2009

Mechanical stimulation is known to play a vital role on the differentiation of mesenchymal stem cells (MSCs) to pre-osteoblasts. In this research, we developed a tensile cell stimulator, composed of a DC motor-driven actuator and LVDT sensor for measuring linear displacement, to study the effects of tensile stress on osteogenic differentiation of MSCs. First, we demonstrated the reliability of this device by showing the uniform strain field in the silicon substrate. Secondly, we investigated the effects of tensile stretching on osteogenic differentiation. We imposed a pre-set cyclic strain at a fixed frequency on cell monolayer cultured on a flexible silicon substrate while varying its amplitude and duration. 60 min of resting period was allowed between 30 min of cyclic stretching and this cycle is repeated up to 7 days. Under the combined stimulation with osteogenic media and mechanical stretching, the osteogenic markers such as alkaline phosphatase (ALP), osterix, and osteopontin began to get expressed as early as 4 days of stimulation, which is much shorter than what is typically required for osteogenic media induced differentiation. Moreover, different markers were induced at different magnitudes of the applied strains. Lastly, for the case of ALP, we observed the antagonistic effects of osteogenic media when combined with mechanical stretching.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권1호
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• pp.25-44
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• 2010

With the increasing popularity of mobile devices, it has become necessary to protect private information and content in these devices. Face recognition has been favored over conventional passwords or security keys, because it can be easily implemented using a built-in camera, while providing user convenience. However, because mobile devices can be used both indoors and outdoors, there can be many illumination changes, which can reduce the accuracy of face recognition. Therefore, we propose a new face recognition method on a mobile device robust to illumination variations. This research makes the following four original contributions. First, we compared the performance of face recognition with illumination variations on mobile devices for several illumination normalization procedures suitable for mobile devices with low processing power. These include the Retinex filter, histogram equalization and histogram stretching. Second, we compared the performance for global and local methods of face recognition such as PCA (Principal Component Analysis), LNMF (Local Non-negative Matrix Factorization) and LBP (Local Binary Pattern) using an integer-based kernel suitable for mobile devices having low processing power. Third, the characteristics of each method according to the illumination va iations are analyzed. Fourth, we use two matching scores for several methods of illumination normalization, Retinex and histogram stretching, which show the best and $2^{nd}$ best performances, respectively. These are used as the inputs of an SVM (Support Vector Machine) classifier, which can increase the accuracy of face recognition. Experimental results with two databases (data collected by a mobile device and the AR database) showed that the accuracy of face recognition achieved by the proposed method was superior to that of other methods.

• 한국기계가공학회지
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• 제14권4호
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• pp.28-33
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• 2015

In this study, the optimal design for the support and the binding device for the protection of crops for the maximum allowable stress of the shape necessary to minimize volume has been proposed. Optimization of the support and the binding device for the crops should be designed to support businesses in terms of profit, in part to reduce the material, and to profit from the ease and speed of working that part of the farmers. We used CATIA for the mechanical design and the ANSYS program for the structural analysis. Additionally, the optimization was performed by PIAnO with seven design variables for the binding device and three parameters for the support. The weight method using a multi-objective function was also determined by the Pareto optimal solution. The volume of the binding device in the optimum design result was found to be reduced by 16%, from $2.278e-005m^3to1.912e-005m^3$. From the result, we confirmed the effectiveness of the design method proposed as a multi-objective function optimization problem.

• 마이크로전자및패키징학회지
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• 제22권1호
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• pp.55-61
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• 2015

신축성 전극소재는 웨어러블 밴드나 전자피부와 같은 플렉서블 제품으로의 적용 때문에 주목 받고 있다. 플렉서블 소자로서 사용하기 위해선 구부리거나 비틀거나 늘리는 등 물리적 변형에도 전기저항의 증가가 최소화되어야 한다. 카본블랙은 저가의 간단한 공정, 특히 인장 시 비저항의 감소라는 장점 때문에 후보소재로 고려되고 있다. 하지만 카본블랙의 전도도는 전극으로 사용되기에 상대적으로 낮다. 이에 비해 그래핀은 뛰어난 전기전도도 및 유연성 때문에 촉망받고 있는 전자소재이다. 따라서 그래핀을 첨가한 카본블랙은 신축성 전극으로 적합한 소재로 예상된다. 본 논문을 통해 인장 시 그래핀을 첨가한 카본전극의 전기적 특성을 연구하였다. 기계적인 인장은 전극 내의 균열(crack)을 형성시켜 도전경로의 파괴를 일으켰다. 하지만 인장으로 정렬된 그래핀은 카본필러 간의 연결성을 강화하고 도전구조를 유지하였다. 무엇보다도 그래핀 첨가로 인하여 인장 시 카본전극의 전자구조가 변화하여 전자를 효과적으로 전도하게 하였다. 결론적으로 그래핀 첨가를 통해 카본블랙 복합체에 신축성 전극으로의 가능성을 부여하였다.