• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.60-64
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• 2001

In this paper, the tension-compression fatigue test method and the fatigue life characteristics of carbon fabric/epoxy laminate coupon are presented. To avoid the buckling during the compression, a proper design for the test coupons is essential. The critical buckling loads for the coupons are calculated by assuming the coupons as columns under two types of fixed conditions. The first is that both ends of each coupon are perfectly clamped, the second is that both ends of each coupon are simply supported. The strain-load curves are obtained by compressing the representative coupons, on each surface of which a strain gage is attached. The buckling loads obtained from the tests are all between the two calculated critical buckling loads. All the coupons are broken by the compression during the fatigue tests. It is estimated to be the reason that the fatigue load causes delamination before the eventual failure of each coupon, and sequentially the micro-buckling in the delaminated region drives each coupon into fatigue failure during the compression. The S-N curve, the fatigue life characteristics of carbon fabric/epoxy is obtained.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.190-195
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• 2004

The compression-compression fatigue properties of the closed cell Al-Si-Ca alloy foams have been studied. The monotonic and cyclic compressive properties were compared with each other and the fatigue stress-life (S-N) curves were presented. In compression-compression fatigue, the crushing was found to initiate in a single band which broadens gradually with additional fatigue cycles. Progressive shortening of the specimen took place due to a combination of low cycle fatigue failure and cyclic ratcheting which is in accordance with the findings of previous researchers [1-3]. Young's modulus of the foam was found to decrease with the increasing strain in case of fatigue test however in case of monotonic compression test the value of Young's modulus increased with the strain (number of cycles). The endurance limit on the basis of $10^{7}$ cycles obtained by extrapolating the experimental results were 0.98 MPa and 1.70 MPa for load ratios 0.1 and 0.5 respectively which are 34 % and 59 % of the plateau stress.

• 한국디자인학회:학술대회논문집
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• 한국디자인학회 2001년도 Bulletin of The 5th Asian Design Conference International Symposium on Design Science
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• pp.43.2-43
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• 2001

• 한국응급구조학회지
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• 제23권3호
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• pp.67-81
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• 2019

Purpose: The purpose of this study was to compare the difference in compression quality and fatigue levels in a rescuer for three different hand techniques used in cardiopulmonary resuscitation (CPR). Methods: The participants were paramedic students at the basic life support provider level. The hands-only CPR was performed for 10 minutes for each of the three hand techniques without disruption, and the quality of chest compressions and fatigue levels were analyzed. Results: There was no difference between the sexes in the chest compression quality and the physiologic parameters before and after compression. Among the quality indexes of chest compression with each of the techniques performed for 10 minutes, the mean depth (p<.01) and mean accuracy (p=.000) of the compression were found to be higher in the five finger fulcrum technique, while the mean compression rate and relaxation accuracy showed no significant differences. Regarding fatigue levels, the five finger fulcrum technique caused lesser subjective fatigue as compared to other techniques (p<.05), although the heart rate and blood pressure revealed no difference. Conclusion: The five finger fulcrum technique was found to be better than the other techniques in terms of chest compression quality and subjective levels of fatigue, indicating that it should be used in CPR education.

• Journal of Biosystems Engineering
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• 제37권1호
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• pp.51-57
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• 2012

Purpose: The compression strength of corrugated fiberboard containers used to package agricultural products rapidly decreases owing to various environmental factors encountered during the distribution of unitized products. The main factors affecting compression strength are moisture absorption, long-term top load, and fatigue caused by shock and vibration during transport. This study characterized the durability of corrugated fiberboard containers for packaging fruits and vegetables under simulated transportation conditions. Methods: Compression tests were done after corrugated fiberboard containers containing fruit were vibrated by an electro-dynamic vibration test system using the power spectral density of routes typically traveled to transport fruits and vegetables in South Korea. Results: To predict loss of compression strength owing to vibration fatigue, a multiple nonlinear regression equation ($r^2=0.9217$, $RMSE=0.6347$) was developed using three independent variables of initial container compression strength, namely top stacked weight, loading weight, and vibration time. To test the applicability of our model, we compared our experimental results with those obtained during a road test in which peaches were transported in corrugated containers. Conclusions: The comparison revealed a highly significant ($p{\leq}0.05$) relationship between the experimental and road-test results.

• 한국응급구조학회지
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• 제16권2호
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• pp.31-41
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• 2012

Purpose : The purpose of the present study is to analyze the accuracy and fatigue felt by lay persons receiving CPR training when they perform hands only CPR (HOCPR) and traditional CPR (TCPR). The performance of CPR data will provide the criteria of dispatcher guidelines for the general public. Methods : For 2 minutes duration, HOCPR was conducted by 51 subjects and TCPR was conducted by 48 subjects. The accuracy measurement of chest compressions was based on the 2010 AHA guideline; the subjective fatigue level in before and after experiment was measured by a self-administered questionnaire. Results : There were no significant differences between the average depth, chest compression depth and chest compression location in terms of chest compression accuracy. However, there were significant differences between the two experimental groups in the accuracies for average speed and chest compression speed. The subjective fatigue level showed no significant difference. Conclusion : The experimental group performing HOCPR showed more accurate compression speed and lower fatigue level. These results suggested that HOCPR would be more effective in training the lay persons in accordance with the voice-instructed CPR.

• 한국포장학회지
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• 제16권1호
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• pp.1-4
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• 2010

The compression strength of corrugated fiberboard containers for packaging the agricultural products rapidly decreases because of various environmental conditions during distribution of unitized products. Among various environmental conditions, the main factors affecting the compression strength of corrugated fiberboard are absorption of moisture, long-term accumulative load, and fatigue caused by shock and vibration. An estimated rate of damage for fruit during distribution is about 30~40% owing to the shock and vibration. This study was carried out to characterize the durability of corrugated fiberboard containers for packaging the fruits and vegetables under simulated transportation environment. After the packaging freight was vibrated at various experimental conditions, the compression test for the packaging was performed. The compression strength of corrugated fiberboard containers decreased with loading weight and vibration time. The multiple nonlinear regression equation ($R^2$ = 0.9198) for predicting the decreasing rate of compression strength of corrugated fiberboard containers were developed using four independent variables such as input acceleration level, input frequency, loading weight and vibration time.

• Composites Research
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• 제23권5호
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• pp.22-29
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• 2010

본 논문은 철도차량 경량화 재질로 적용된 유리섬유/에폭시 4-매 주자직 적층 복합재료의 인장-압축 피로특성을 평가하였다. 유리섬유/에폭시 4-매 주자직 적층 복합재료의 인장-압축 피로시험은 경사, 위사 그리고 ${\pm}45^{\circ}$ 방향으로 적층된 시험편에 대하여 수행하였다. 인장-압축 피로시험은 5Hz의 주파수를 갖으며, 응력비(R)는 -1로 수행하였다. 인장-압축 피로시험 수행 시 압축하중에 의한 시험편의 좌굴을 방지하기 위하여 좌굴방지지그를 설계하고 이를 시험에 적용하였다. 또한, Goodman 선도는 유리섬유/에폭시 4-매 주자직 적층 복합재의 피로특성과 수명을 평가하기 위해 사용하였다. 유리섬유/에폭시 4-매 주자직 적층 복합재료의 인장-압축 피로시험결과 경사방향 적층 복합재의 피로특성이 기존 금속재 대차에 적용되는 SM490에 비하여 우수한 것으로 나타났다.

• 한국정밀공학회지
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• 제26권8호
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• pp.142-147
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• 2009

Spinal fixation systems provide surgical versatility, but the complexity of their design reduces their strength and fatigue resistance. There is no published data on the mechanical properties of such screws. Screws were assembled according to a vertebrectomy model for destructive mechanical testing. A group of two assemblies was tested in static compression. One group was applied to surface a grit blasting method and another group was applied to surface a bead blasting method. Modes of failure, yield, and ultimate strength, yield stiffness, and cycles to failure were determined for six assembles. Static compression 2% offset yield load ranges was from 327 to 419N. Fatigue loads were determined two levels, 37.5% and 50% of the average load from static compression ultimate load. An assembly of bead blasting treatment only achieved 5 million cycles at 37.5% level in compression bending.

• 한국응급구조학회지
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• 제26권2호
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• pp.61-71
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• 2022

Purpose: This experimental study compared the chest compression quality, muscle activity, and subjective fatigue of paramedic students who did or did not wear a mask. Methods: The subjects of this study were 13 paramedic students at college D located in B city. Frequency percentages, mean standard deviations, and paired sample t-tests were conducted using the SPSS/WIN 23.0 program. Results: This study revealed that chest compression depths (t=-2.151, p=.053) and compression rates (t=-2.714, p=.019) were higher in mask-wearers, while muscle activity and subjective fatigue (t=2.382, p=.035) of the erector spinae (t=7.082, p=.001), rectus abdominis (t=4.776, p=.001), and pectoralis major muscles (t=3.193, p=.008) were lower in mask-wearers. Conclusion: The results of this study can be used as a basis to increase the resuscitation rates of cardiac arrest patients and provision of high-quality chest compressors to rescuers when infectious diseases recur in the future.