• Journal of Aerospace System Engineering
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• v.17 no.4
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• pp.10-17
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• 2023

This paper describes the research and development of a 3.0 m Solar-Powered UAV system for mission flight that is based on the 4.2 m Solar-powered UAV. Both the Solar-Powered UAVs were lightened in weight by applying a composite fuselage and solar charging system. Also, a deep stall landing application and airbag module were installed for usability in mission performance. The flight performance of the Solar-Powered UAV system was verified through flight test. In particular, the 3.0 m Solar-Powered UAV performed continuous flight along the coastline of Jeju Island for 147 km in 3 hours and 50 minutes, and its performance as a mission flight was also confirmed.

• Journal of Life Science
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• v.33 no.5
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• pp.436-444
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• 2023

Scientific training, diet, and ergogenic aids are widely used to overcome the limits of humans' physical abilities and to achieve excellent sports records. The adoption of nutritional strategies is important for athletes to perform at their highest level, and one of the main factors determining endurance ability is increased fat metabolism. A ketogenic diet (high fat, low carbohydrates) has thus been proposed as an alternative strategy to maximize fatty acid oxidation during prolonged periods of exercise. However, studies have shown mixed results regarding the ergogenic value of a ketogenic diet. For this reason, exogenous ketone supplements (EKS, ingestible forms of ketone bodies, ketone esters, and/or salts) have been suggested to obtain nutritional ketosis, an acute transient increase in circulating acetoacetate (AcAc) and b-hydroxybutyrate (bHB) concentrations, without limiting carbohydrate intake. Some studies have suggested the beneficial effects of EKS on the performance of endurance exercises by providing an additional fuel substrate for peripheral tissues, such as cardiac and skeletal muscles, sparing carbohydrates/increasing fat oxidation and post-exercise recovery by increasing glycogen resynthesis in the liver/muscle, attenuating protein degradation, stimulating protein synthesis in the skeletal muscle, etc. However, many studies have failed to observe the beneficial effects of EKS as an ergogenic aid. As such, this review summarizes the theoretical basis of, as well as the proposed and proven effects of EKS on exercise performance and recovery to date.

• Korean Journal of Exercise Nutrition
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• v.25 no.1
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• pp.7-15
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• 2021

[Purpose] Sodium bicarbonate shows ergogenic potential in physical exercise and sports activities, although there is no strong evidence which performance markers show the greatest benefit from this supplement. This study evaluated the effects of sodium bicarbonate supplementation on time trial performance and time to exhaustion in athletes and sports practitioners. [Methods] A systematic review was conducted using three databases, including 17 clinical trials. Among these clinical trials, 11 were considered eligible for the meta-analysis according to the criteria for the assessment of methodological quality using the PEDro Scale. Time to exhaustion was assessed in six studies, while time trial performance was evaluated in five studies. [Results] A significant beneficial effect of supplementation on time to exhaustion was found in a random effects model (1.48; 95% confidence interval [CI], 0.49 to 2.48). There was no significant effect of supplementation on time trial performance in a fixed effects model (slope = -0.75; 95% CI, -2.04 to 0.55) relative to a placebo group. [Conclusion] Sodium bicarbonate has the potential to improve sports performance in general, especially in terms of time to exhaustion.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.12
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• pp.1035-1047
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• 2015

Wind tunnel experiment and computational analysis have been carried out to evaluate the performance of propeller for scale electric-powered HALE UAV, named EAV-2H+. Performance curves are measured for three propellers and their adequacy for EAV-2H+ installation is examined through consideration of operating conditions. Decline in performance coefficients is observed in low rpm region. Also, the effect of transition tape on propeller performance is measured and analyzed. The computational performance analyses are carried out by using commercial CFD program. The thrust and power coefficient from computations show good agreement with experimental results. Performance coefficients are compared and the influence of measurement device which contributes to discrepancy of the results is examined. Transition SST model is confirmed to yield the tendency of performance decline in low rpm range, similar to experimental observation. The decrease in aerodynamic performance of blade element due to low Reynolds number is identified to cause the decline in propeller performance. Analyses for high altitude conditions confirms degradation in propeller performance.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.1
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• pp.89-95
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• 2020

The main scope of this paper is to see if the conventional pump can be properly used for a specific fuel, Di-methyl Ether (DME) despite of its low lubricity and high reactivity in the experimental conditions. A wobble plate type fuel pump was connected to the common rail to verify that the pump could deliver the fuel at the required pressure and resultantly DME could be used as fuel without modifying the original pump. At each required pressure (30 Mpa, 35 Mpa, 40 Mpa, 45 Mpa, and 50 Mpa), the pump met the pressure required by the common rail. In addition, pump performance experiments tended to follow the usual performance curve while the flow rate decreased as the pressure increased. The maximum flow rate of the pump was 470 kg/h at 30 Mpa and all measurements were taken with keeping DME temperature below 60℃.

• The KSFM Journal of Fluid Machinery
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• v.9 no.6 s.39
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• pp.45-53
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• 2006

Turbo-blower as an air supply system is one of the most important BOP (Balance of Plant) systems for FCV(Fuel Cell Vehicle). For generating and blowing compressed air, the motor of air blower consumes maximum 25% of net power, and fuel cell demands a clean air. In this study, turbo-blower supported by air foil bearings is introduced as the air supply system used by 80kW proton exchange membrane fuel systems. The turbo-blower is a turbo machine which operates at high speed, so air foil bearings suit their purpose as bearing elements. Analysis for confirming the stability and endurance is conducted. The rotordynamic stability was predicted using the numerical analysis of air foil bearings and it is verified through experimental works. In spite of various transient dynamic situation, the turbo-blower had stable performances. After the performance test, results are presented. The normal power of driving motor has about 1.6 kW with the 30,000 rpm operating range and the flow rate of air has maximum 160 SCFM. The test results show that the aerodymic performance and stability of turbo-blower are satisfied to the primary goals.

• Physical Therapy Korea
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• v.15 no.3
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• pp.17-25
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• 2008

This study aimed to evaluate the effect of a weekly circuit-group exercise program on functional performance, flexibility of the trunk and lower extremities, and balance in individuals with chronic stroke who are living in a community. Thirteen community-living individuals (eleven males and two females) with chronic stroke participated in this study. The group exercise program was set up as a weekly circuit application with four stations aiming to strengthen the muscles, increase endurance, improve flexibility, and enhance functional capacity. The average duration of a session was an hour, and the sessions were conducted once a week for six months for a total of 24 sessions. Assessments for functional performance, flexibility of the trunk and lower extremities and balance were conducted four times: before treatment, after one month of treatment, after four months of treatment, and after six months of treatment. There were significant improvements in functional performance and flexibility of the trunk and lower extremities in the given time frame. No significant improvement was observed in balance ability. The findings suggest that a weekly circuit-group exercise program has some benefits in terms of managing the physical symptoms of individuals with mobility problems after stroke. Therefore, this program can be adapted and employed as a community-based rehabilitation program for such patients. Further studies with various community-based treatments will be conducted to validate these findings.

• Journal of the Korean institute of surface engineering
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• v.43 no.1
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• pp.41-45
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• 2010

The effect of $MoS_2$ and graphite content on wear resistance and mechanical properties of Cu/Sn bonded diamond micro blades was comparatively investigated in terms of volume and weight fraction. For the evaluation of endurance and cutting performance, instantaneous electric power consumption and cumulative wear loss during cutting glass work piece at constant velocity were measured with the micro blades of the wide range of lubricant content. The energy consumption of blades for glass cutting decreased with the content of lubricants. Wear amount of blade in volume increased with the amount of lubricant addition. It was found to be relevant to the decrease in flexural strength and hardness with the amount of lubricants. With the same amount of lubricant content in volume fraction $MoS_2$ showed superiority in mechanical properties and cutting performance than graphite while graphite could result in stronger effect on lowering electric consumption during cutting work piece for the same weight percent fraction than $MoS_2$ because of lower density.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.10
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• pp.31-35
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• 2020

Hydraulic winches for transportation and logistics in the shipbuilding and marine plant fields require multi-stage planetary gear modules with high gear ratios. Due to environmental conditions in the ship, durability is crucial. Further, we are currently relying on foreign products. The development of domestic technology will reduce cost, save time, and improve the export market. Thus, we developed a multi-stage planetary gear module for a hydraulic winch and evaluated its performance through several tests of the hydraulic brake torque, maximum torque, and load endurance.

• 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.