• 대한기계학회논문집A
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• 제20권9호
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• pp.2792-2799
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• 1996

It was shown in the previous study that the numerically derived elastic work factor for CLS specimen was independent of fiber direction for a unidirectional case. Also, it was proposed the elastic work factor could be used to determine energy release rate from a single test record. In the present study, elastic work factor was derived from a simple beam theory to investigate its dependence on material property and geometric condition. Also, the elastic work factor of CLS specimen was applied experimentally to determine critical energy release rate in order to prove its validity determining critical energy release rate from a single specimen. For this purpose, critical energy release rate determined using the elastic work factor was compared with that determined by the compliance method. The results showed that while elastic work factor is affected by $t_2/t_1$ and $L_2/L_1$ it is independent of fiber angle for a unidirectional case. It was also found that critical energy release rates determined by both methods are comparable each other, thus elastic work factor approach can be used to determine energy release rate from a single test specimen.

• 대한의생명과학회지
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• 제13권1호
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• pp.55-60
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• 2007

Computerized image processing and analysis system was used for quantitative assessment of skin tissue components in color histological sections. The purpose of this study was to determine that the changes in the collagen fiber density and elastic fiber density in dermis in the rat skin as aging. And also to determine that the correlation between fibroblast density and collagen fiber density and elastic fiber density in the aged rat skin. Ten weeks old ($130{\sim}150g$) eight and fifty-four weeks old ($300{\sim}350g$) eight female Sprague-Dawley rats were used. The full-thickness skin biopsy specimens were prepared serial sections and stained with hematoxylin and eosin, Masson's trichrome and Verhoeff-van Gieson. The collagen fiber and the elastic fiber were identified using the image analysis processing system and then calculated the collagen fiber density rate and the elastic fiber density rate in the dermis. It also identified fibroblast and calculated fibroblast density in the dermis. By using a Student's t-test, a decrease in the collagen fiber density rate (t=-4.650, P<0.001) and the elastic fiber density rate (t=-6.494, P<0.001) of dermis can be observed in aged rats as compared with the young rats. A Student's t-test showed a significantly less fibroblast density in the aged rats than the young rats (t=-4.497, P<0.001). There were significantly positive correlation between the fibroblast density and the collagen fiber density rate (r=.69, P<0.001) and the elastic fiber density rate (r=.91, P<0.001). These results indicate that the aging may decrease the collagen fiber density and elastic fiber density due to reduced the proliferative and synthetic activity of fibroblast in the dermis.

• International journal of advanced smart convergence
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• 제12권4호
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• pp.395-406
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• 2023

Ten women in their 20s and 10 women in their 50s were selected to investigate the effect of an elastic band exercise program for 8 weeks according to age on women's knee speed expression rate and balance. Knee isokinetic muscle strength measurement, single-legged standing with eyes closed, and YBT were performed 1 week before and after the exercise program. The measured data were analyzed through a mixed design two-way ANOVA, and if there was a significant difference, post hoc verification was performed using the bonferoni method. In our study, as a result of an 8-week elastic band exercise program, there was no difference in the speed development rate according to the measurement period, and the speed development rate according to age was found to be higher in people in their 50s than in their 20s. In our study, there was no difference in balance ability depending on the measurement period, and there was also no difference in balance ability depending on age. Discussing the results of our study, we found that 8 weeks of elastic band exercise cannot bring about significant changes in speed development ability and balance ability, which become more accurate with age.

• 대한기계학회논문집A
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• 제24권8호
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• pp.1917-1922
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• 2000

The split Hokinson pressure bar(SHPB) test has been used to find the mechanical property of materials at high strain rate. A tensile split Hopkinson pressure bar test system is developed and the threaded tensile specimen and the split collar are placed between elastic bars. When the compressive elastic wave generated by a striker is transferred from the transmit bar to the incident bar, some elastic wave is reflected at the threaded parts of the specimen and the transmit bar. This reflected wave can interfere with the transmitted wave. A proper length of elastic bars and the location of strain gage in these elastic bars are determined to avoid this interference. In order to avoid the interference of elastic wave reflected at the threaded parts of specimen and elastic bar, the length of transmit bar must be longer than that of incident bar. Strain gage in transmit bar must be located as close as possible from the interface of a transmit bar and specimen. In the developed tensile SHPB test system, A12011-T3 and A17075-T6 are tested to get the true stress-strain relation in the range of strain rate at $10^3/sec$

• 대한기계학회논문집A
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• 제23권6호
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• pp.912-921
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• 1999

Shear stress acting on the arterial wall by blood flow is an important hemodynamic factor influencing blocking of blood vessel by thickening of an arterial wall. In order to study the effects of wall elasticity on the wall shear rate distribution in an artery-divergent graft anastomosis, a rigid and a elastic model are manufactured. These models are placed in a pulsatile flow loop, which can generate the desired flow waveform. Flow visualization method using a photochromic dye is used to measure the wall shear rate distribution. The accuracy of measuring technique is verified by comparing the measured wall shear rate in the straight portion of a model with the theoretical solution. Measured wall shear rates depend on the wall elasticity and flow waveform. The mean and maximum shear rate in the elastic model are lower than those in rigid model, and the decreases are more significant near the end of a divergent tube. The reduction of mean and maximum of wall shear rate in an elastic model are up to 17 percent.

• 한국정밀공학회지
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• 제21권4호
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• pp.148-153
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• 2004

It is well-known that the mechanical behavior of fiber-reinforced composites under hydrostatic pressure environment is different from that of atmospheric pressure environment. It is also known that the mechanical behavior of fiber-reinforced composites is affected by a strain rate. In this work, we investigated the effect of strain rate on the compressive elastic modulus, fracture stress, and fracture strain of carbon/epoxy composites under hydrostatic pressure environment. The material used in the compressive test was unidirectional carbon/epoxy composites and the hydrostatic pressures applied was 270㎫. Compressive tests were performed applying three strain rates of 0.05％/sec, 0.25％/sec, and 0.55％/sec. The results showed that the elastic modulus increased with increasing strain rate while the fracture stress was little affected by the strain rate. The results also showed that the fracture strain decreased with increasing strain rate.

• The Journal of Korean Physical Therapy
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• 제26권5호
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• pp.372-378
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• 2014

Purpose: The aim of this study was to evaluate the effect of side walking training with an elastic-band on gait and balance ability of stroke patients. Methods: Twenty three patients with stroke participated in the study. Participants were randomly assigned to the side walking with elastic-band group (n=7), the side walking without elastic-band group (n=8), and the walking on the treadmill group (n=8);. 10 m walking test (10MWT), Dynamic Gait Index (DGI), Berg Balance Scale (BBS), and modified Functional Reach Test (mFRT) were performed for evaluatione of pre- and post-intervention in gait and balance ability of participants. Results: Significantly differences in 10 MWT, DGI, BBS, and mFRT were observed between pre- and post-intervention in three groups (p<0.05). Improvement of pre- and post-intervention of mFRT showed significant difference (p<0.05). The highest rate of change was observed in the side walking with elastic-band group and rate of change showed in the order of the side walking without elastic-band group, walking on the treadmill group. Conclusion: This study suggests that side walking training with an elastic-band may help to improve gait and balance ability of stroke patients.

• 한국응급구조학회지
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• 제15권3호
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• pp.71-80
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• 2011

Purpose : This research was designed to provide basic data for advanced pre-hospital airway management by comparing the ease of intubation, the success rate and the time for intubation performed with Macintosh Laryngoscope, Gum Elastic Bougie and Pentax AirWay Scope on the floor and table. Methods : Intubation was performed 30 times in total, including 5 times for each of intubation using Macintosh Laryngoscope, Gum Elastic Bougie and Pentax Airway Scope on the table and floor, only on subjects who passed the practice test of the national exam for paramedics. Data were collected by measuring the ease of intubation, the success rate and the time for intubation, and then analyzed by descriptive analysis, paired t-test, ANOVA using SPSS 18.0. Results : 1. There was a significant difference in the ease of intubation according to intubation devices. 2. There was a significant difference in the ease of intubation according to table height for intubation. 3. There was a significant difference in the success rate according to intubation devices. 4. There was no significant difference in the success rate according to table height for intubation. 5. There was a significant difference in the intubation time according to intubation devices. 6. There was a partially significant difference in the intubation time according to table height for intubation. Conclusion : Sufficient training not only with Macintosh Laryngoscope but also with Gum Elastic Bougie and Pentax Airway Scope could improve the survival rate by intubation in patients with difficult airway.

• 대한기계학회논문집B
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• 제37권2호
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• pp.111-117
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• 2013

탄성튜브가 연결된 펌핑 챔버를 이용한 무밸브 펌프를 가상경계방법을 이용하여 수치적으로 연구하였다. 탄성 튜브와 펌핑 챔버 사이의 상호작용으로 인하여 무밸브 펌프 내의 유동이 생성되었으며, 탄성튜브의 스트레칭 계수, 벤딩 계수, 종횡비가 무밸브 펌프의 전체 유량에 미치는 영향을 살펴보았다. 펌프의 메커니즘을 이해하고자, 시간에 따른 탄성 튜브의 움직임과 그에 따른 유동 속도의 변화를 자세히 살펴보았으며, 탄성 튜브의 직경 크기와 펌프의 평균 유량 사이의 관계를 분석하였다.

• 대한치과교정학회지
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• 제16권1호
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• pp.133-144
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• 1986

This study was conducted to evaluate the effects of loop formation and heat treatment upon the elastic properties of orthodontic wires. The specimens selected were .016', .018', .016x.022', and .018x.022' sized stainless steel (standard) and cobalt-chromium-nickel wires, and were divided into 7 groups as; 1. straight non-heat treated 2. U looped non-heat treated 3. L looped non-heat treated 4. Circle looped non-heat treated 5. U looped heat treated 6. L looped heat treated 7. Circle looped heat treated Heat treatment was performed in Big Jane furnace at 850' F for 3 minutes. The elastic limit and the elastic range of each specimen were determined by bending test, and load deflection rate was computed from those values. The findings were as follows; 1. The formation of loop resulted in increased load-deflection rate for both stainless steel and cobalt-chromium-nickel wires. 2. The heat treated group showed higher load-deflection rate than non-heat treated group, which was more apparent in cobalt-chromiumnickel wire than in stainless steel wire. 3. L loop had the highest load-deflection rate among 3 types of loops, followed by U loop and circle loop. 4. The specimens with greater diameter displayed the more increase in load-deflection rate by looping and heat treatment.