• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.7
• /
• pp.9-17
• /
• 2005

The wake patterns and thrust characteristics of dual flapping airfoils in a biplane configuration are investigated using an unsteady panel method. To trace complicated wake shapes behind airfoils, a core addition scheme, a vortex core model, and the fourth order Runge-Kutta convection scheme are employed. Present results are verified by comparing them with flow visualization, exact solution and published computed results. The thickness and camber of thick airfoils has an effect of decreasing thrust. The airfoils produce maximum thrust when the phase angles between plunging and pitching motions are both 90 and 120 degrees. Thrust increases as the plunge velocity is increased, which is also found as the pitch amplitude is stepped up. Thrust decreases when the distance between the airfoils is less than 0.6c.

• Journal of the Korea Society of Computer and Information
• /
• v.28 no.12
• /
• pp.175-182
• /
• 2023

In this paper, we propose a study compared and analyzed the CPR results and muscle fatigue of the three groups. There is a group that counts loudly when compressing the mannequin's chest (Group A), a group that breathes autonomously without counting (Group B), and a group that breathes abdominally without counting (Group C). Twelve people were assigned to each group, and after performing chest compressions for 5 minutes, the results of CPR were analyzed using a program connected to the mannequin, and the muscle fatigue of the performers was analyzed using wireless electromyography. The most efficient method was found to be group B. If we only look at the speed and depth of compression within the normal range, Group C would be more efficient, but Group B showed significantly lower muscle fatigue, and Group A did not reach the normal range in depth of chest compression and muscle fatigue was the highest. Group B was also found to be the most accurate in hand positioning accuracy, and was also found to be the most efficient in maintaining concentration on chest compressions.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.3
• /
• pp.41-48
• /
• 1965

This study was aimed at knowing the magnitude of year variation in rice heading dates under the different seasonal cultures, and to estimate the heading date in advance. Using six rice varieties such as Kwansan, Suwon＃82, Suwon ＃144, Norin＃17, Yukoo＃132 and Paltal, the early, ordinary and late seasonal cultures had been carried out at Paddy Crop Division, Crop Experiment Station at Suwon for the six-year period 1959 to 1964. In addition the data of the standard rice cultures at the Provincial Offices of Rural Development for the 12-year period 1953 to 1954, were analyzed for the purpose of clarifying a relationship between variation of rice heading dates and some of meteorological data related to the locations and years. The results of this study are as follows: 1. Year variation of rice heading dates was as high as 14 to 21 days in the early seasonal culture and 7 to 14 days in the ordinary seasonal culture, while as low as one to seven days in the late seasonal culture which was the lowest among three cultures. The magnitude of variation depended greatly on variety, cultural season and location. 2. It was found out that there was a close negative correlation between the accumulated average air temperature for 40 days from 31 days after seeding and number of days to heading in the early seasonal culture. Accordingly, it was considered possible to predict the rice heading date through calculation of the accumulated average air temperature for the above period and then the linear regression(Y=a+bx). On the other hand, an estimation of the heading date in the late seasonal culture requires for the further studies. In the ordinary seasonal culture, no significant correlation between the accumulated average air temperature and number of days to heading was obtained in the six-year experiments conducted at Suwon. There was a varietal difference in relationship between the accumulated average air temperature for 70 days from seeding and number of days to heading in the standard cultures at the provincial offices of rural development. Some of varieties showed a significant correlation between two factors while the others didn't show any significant correlation. However, there was no regional difference in this relationship.