• Journal of Biosystems Engineering
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• v.34 no.5
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• pp.325-330
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• 2009

This study was performed to develop accelerated life test methods for agricultural tractor transmission receiving variable load. To acquire parameters for calculation of accelerated life test, endurance tests were performed under different torque conditions. Test results showed that the shape factor of Weibull distribution was 1.5 and fatigue damage exponent was 5.4. The calculated test time was 5,877 hours under the conditions of average life (MTBF) 3,000 hours and 90% reliability for one test sample. According to the linear cumulative damage rule, test time could be reduced using increased test load. Test time could be reduced by 252 hours when 1.2 times of the rated load compared with 0.67 times of the rated equivalent load calculated by load spectrum of the agricultural tractor. Calculated acceleration coefficient was 23.3.

• Journal of Electrical Engineering and Technology
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• v.3 no.2
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• pp.184-191
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• 2008

Electrical endurance is the critical characteristic of Magnetic contactors(MCs), which are widely used in such power equipment as elevators, cranes, and factory control rooms in order to close and open control circuits. Testing time, however, is not short in typical cases in which some method of reducing the testing period is required. This study shows the method of determining the stress level of electrical ALT(Accelerated Life Test) through optical temperature sensor and the relationship between 0.05 s and 0.1 s for on-time. The tool used for analyzing the test result is MINITAB. I will propose the method of determining the optimized stress level through optical temperature sensor, which will contribute to minimize the testing time and development period and also raise the product reliability.

• Advances in aircraft and spacecraft science
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• v.10 no.5
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• pp.393-418
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• 2023

Drones are increasingly used in logistics delivery due to their low cost, high-speed and straight-line flight. Considering the small cargo capacity, limited endurance and other factors, this paper optimized the pickup and delivery vehicle routing problem with time windows in the mode of "truck+drone". A mixed integer programming model with the objective of minimizing transportation cost was proposed and an improved adaptive large neighborhood search algorithm is designed to solve the problem. In this algorithm, the performance of the algorithm is improved by designing various efficient destroy operators and repair operators based on the characteristics of the model and introducing a simulated annealing strategy to avoid falling into local optimum solutions. The effectiveness of the model and the algorithm is verified through the numerical experiments, and the impact of the "truck+drone" on the route cost is analyzed, the result of this study provides a decision basis for the route planning of "truck+drone" mode delivery.

• The Journal of the Korea Contents Association
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• v.8 no.10
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• pp.301-308
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• 2008

The purpose of this study was to investigate the change of physical fitness, MDA, SOD after short-term weight reduction through exercise, food restriction and exhalation of sweat among Taekwondo players. The subjects ten male collage Taekwondo players with excellent practical skills, and more than seven years of experiences. They were asked to reduce about 5% of their body weight in seven days. Physical fitness levels were analyzed through grip strength, muscle endurance, flexibility, power, agility, balance, reaction time and MDA and SOD through blood test. The results of this study were as follows; First, there was no significant change in physical fitness due to short-term weight reduction in muscle strength, muscle endurance, flexibility, power, agility, balance and reaction time. Second, The change of MDA and SOD, resulting from short-term weight reduction did not show significant difference statistically. Therefore, the results of this study indicate that the Taekwondo players' short-term weight reduction of 5% of their body weight did not influence on their athletic performance and physiological capacity. Therefore athletes and coaches should endeavor to take exercise, dietary, and dehydration into consideration when conducting 5% of their body weight reduction in a week.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.56-56
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• 2011

투명 메모리 소자는 향후 투명 디스플레이 등 투명 전자기기와 집적화해 통합형 투명 전자시스템을 구현을 위해 지속적으로 연구가 진행 되고 있으며, 산학계에서는 다양한 메모리 소자중 큰 밴드-갭(>3 eV) 특성을 가지는 저항 변화 메모리(Resistive Random Access Memory, ReRAM)를 이용한 투명 메모리 구현 가능성을 지속적으로 보고하고 있다. 현재까지의 저항 변화 메모리 연구는 물질 최적화를 위해 다양한 금속-산화물계(Metal-Oxide) 저항 변화 물질에 대한 연구가 활발하게 진행 되고 있지만, 금속-산화물계 물질의 경우 근본 적으로 그 제조 공정상 산소에 의한 다수의 산소 디펙트 형성과 제작 시 쉽게 발생할 수 있는 표면 오염의 문제점을 안고 있으며, 또한 Endurance 및 Retention 등의 신뢰성에 문제를 보이고 있다. 따라서, 이러한 문제점을 근본 적으로 해결하기 위해 새로운 저항 변화 물질에 관한 물질 최적화 연구가 요구 되며, 본 연구진은 다양한 금속-질화물계(Metal-Nitride) 물질을 저항변화 물질로 제안해 연구를 진행 하고 있다. 이전 연구에서, 물질 고유의 우수한 열전도(285 W/($m{\cdot}K$)) 및 절연 특성, 큰 밴드-갭(6.2 eV), 높은 유전율(9)을 가지고 있는 금속-질화물계 박막인 AlN를 저항변화 물질로 이용하여 저항변화 메모리 소자 연구를 진행하였으며, 저전압 고속 동작 특성을 보이는 신뢰성 있는 저항 변화 메모리를 구현하였다. 본 연구에서는 AlN의 큰 밴드-갭 특성을 이용하여 투명 메모리 소자를 구현하기 위한 연구를 진행 하였다. 투과도 실험 결과, 가시광 영역 (380-700 nm)에서 80% 이상의 투과도를 보였으며, 이는 투명 메모리 소자로써의 충분한 가능성을 보여 준다. 또한, I-V 실험에서 전형적인 bipolar 스위칭 특성을 보이며, 스위칭 전압 및 속도는 VSET=3 V/Time=10 ns, VRESET=-2 V/Time=10ns에서 가능하였다. 신뢰성 실험에서, 108번의 endurance 특성 및 105 초의 retention 특성을 보였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.427-427
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• 2012

Ferroelectric-gate field effect transistor based memory using a nanowire as a conducting channel offers exceptional advantages over conventional memory devices, like small cell size, low-voltage operation, low power consumption, fast programming/erase speed and non-volatility. We successfully fabricated ferroelectric nonvolatile memory devices using both n-type and p-type Si nanowires coated with organic ferroelectric poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] via a low temperature fabrication process. The devices performance was carefully characterized in terms of their electrical transport, retention time and endurance test. Our p-type Si NW ferroelectric memory devices exhibit excellent memory characteristics with a large modulation in channel conductance between ON and OFF states exceeding $10^5$; long retention time of over $5{\times}10^4$ sec and high endurance of over 105 programming cycles while maintaining ON/OFF ratio higher $10^3$. This result offers a viable way to fabricate a high performance high-density nonvolatile memory device using a low temperature fabrication processing technique, which makes it suitable for flexible electronics.

• Journal of Korean Physical Therapy Science
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• v.15 no.3
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• pp.73-79
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• 2008

Background : Treadmill training has been proposed as a useful adjunct to conventional physical therapy to restore ability to walk after stroke. The purpose of this study to inform clinical practise by evaluating the research evidence for the effectiveness of treadmill training after stroke. Methods : We searched to the effectiveness of any form of intervention for effect of treadmill training by Dankook University electronic library databases of Medline, Embase, Cinahl, Amed and PEDro combined with a hand search of papers published in relevant peer-reviewed journals. Any type of study relevant to the topic published in English during time period from 1980 to 2007 was included. Results : The literature search identified 35 studies. The included studies enrolled a total of 374 subjects. 1. Treadmill retraining without partial body weight support might be more effective than no treatment at improving gait velocity, get up and go time, gait endurance and step length symmetry. 2. Treadmill retraining with partial body weight support might be more effective than no treatment in improving step length symmetry, gait velocity, gait endurance and balance. 3. Treadmill retraining might be more effective with partial body weight support than without it at improving gait velocity and motor improvement as measured by The Stroke Rehabilitation Assessment of Movement(STREAM). 4. Treadmill retraining without partial body weight support may be no different from physiotherapy and increase gait velocity to conventional gait therapy. 5. Treadmill retraining with partial body weight support may be no different from physiotherapy for gait velocity, motor recovery and balance. Conclusion The review suggests that although treadmill training of gait, especially with partial body weight support, might Improve gait parameters and functional mobility, unless treadmill training is directed at Improving gait speed it might be no more effective than conventional physical therapy at improving gait parameters.

• Journal of Electrical Engineering and Technology
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• v.12 no.4
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• pp.1641-1648
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• 2017

Many researchers had examined the validity of using the high-to-low ratio between two fixed frequency band amplitudes (H/L-FFB) from the surface electromyography of a face and body as the first spectral index to assess muscle fatigue. Despite these studies, the disadvantage of this index is the lack of a criterion for choosing the optimal border frequency. We tested the potential of using the high-to-low ratio between two signal spectral moments (H/L-SSM), without fixed border frequencies, to evaluate muscle fatigue and predict endurance time ($T_{end}$), which was determined when the subject was exhausted and could no longer follow the fixed contraction cycle. Ten healthy participants performed five sets of voluntary isotonic contractions until they could only produce 10% and 20% of their maximum voluntary contraction (MVC). The $T_{end}$ values for all participants were $138{\pm}35s$ at 10% MVC and $69{\pm}20s$ at 20% MVC. Changes in conventional spectral indices, such as the mean power frequency (MPF), Dimitrov spectral index (DSI), H/L-FFB, and H/L-SSM, were extracted from surface EMG signals and were monitored using the initial slope computed every 10% of $T_{end}$ as a statistical indicator and compared as a predictor of $T_{end}$. Significant correlations were found between $T_{end}$ and the initial H/L-SSM slope as computed over 30% of $T_{end}$. In conclusion, initial H/L-SSM slope can be used to describe changes in the spectral content of surface EMG signals and can be employed as a good predictor of $T_{end}$ compared to that of conventional spectral indices.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.10
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• pp.1409-1416
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• 2012

This study examined the effects of four herbal sports drinks containing Prunus mume, Liriope platyphylla, and Acanthopanax senticosus fruit extracts on body fat and endurance of rats trained by a progressive loaded exercise program. Forty male Sprague-Dawley rats (6 weeks old) were divided into five groups and fed experimental diets for 6 weeks according to the following protocol: C, exercise-trained control group (n=8); A, exercise group with Acanthopanax senticosus extract (n=8); L, exercise group with Liriope platyphylla extract (n=8); PA, exercise group with Prunus mune fruit extract plus Acanthopanax senticosus extract (n=8); PL, exercise group with Prunus mune fruit extract plus Liriope platyphylla extract (n=8). Endurance was measured by a progressive loaded exercise test using a treadmill. PA and PL supplementation significantly extended time to exhaustion compared to the control group (p<0.05). Further, the four herbal sports drinks all significantly reduced epididymal and interscapular white adipose tissue weights compared to the control group (p<0.05). Plasma triglyceride concentration was significantly lower in the A group compared to the control group. Plasma free fatty acid concentration was higher in the A group compared to the control group. On the other hand, Acanthopanax senticosus fruit extract supplementation tended to reduce the plasma glucose concentration compared to the control group. PA and PL supplementation significantly increased gastrocnemius muscle LDH activities compared to the control group (p<0.05). These results show that sports drink containing Acanthopanax senticosus improved endurance capacity, plasma lipids, and glucose concentrations. Sports drink with Prunus mume and Liriope platyphylla or Acanthopanax senticosus was synergistically improved endurance.

• Journal of the Korean Applied Science and Technology
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• v.41 no.2
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• pp.413-423
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• 2024

Sixteen male college students were divided into two groups: a face-to-face group(n=8) and a real-time non-face-to-face exercise group(n=8), engaging in 30minute sessions twice a week for a duration of 8 weeks. Body composition and physical strength were measured as dependent variables before and after the home training period. For data analysis, a two-way ANOVA with repeated measures was conducted to evaluate the effects on body composition and physical strength, considering differences in exercise methods and measurement periods. Post hoc analysis using Bonferroni correction was applied. To compare the mean difference in change between groups, the pre-post difference was calculated, and an independent t-test was performed. The statistical significance level was set at p<.05. The results showed that 8 weeks of home training led to an increase in skeletal muscle mass and improvements in muscle strength, muscular endurance, and cardiorespiratory endurance in male college students, regardless of whether they participated in face-to-face or real-time non-face-to-face exercise. Moreover, there was no significant difference in exercise effectiveness between the face-to-face and real-time non-face-to-face exercise methods. Thus, these findings suggest that real-time non-face-to-face exercise can be as effective as face-to-face exercise in enhancing skeletal muscles and physical strength in male college students. Additionally, if a real-time non-face-to-face exercise program is validated for individuals with mobility issues or the elderly, it could serve as an effective alternative for those who face challenges in participating in face-to-face exercise sessions.