• Journal of Advanced Marine Engineering and Technology
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• v.31 no.4
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• pp.385-393
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• 2007

The strength evaluation of the most weakest junction part is required for the safety design of all structures. Most of all. in order to enhance the reliability and safety of the welding part. whose use is the highest, it is very important to establish the efficient structure manufacturing technology by studying and investigating the evaluation of fatigue strength in various environments. This study analyzed the relations of da/dN, and th according to the welding methods of SMAW, FCAW, and SAW. In the stage II. the value of stress intensity factor range was the highest in SMAW welding method of stress ration R=0.1, and appeared under the sequence of FCAW and SAW and as the completion section of stress intensity factor was low, threshold stress intensity factor was lowly formed in da/dN - The fatigue life of each welding method is sensitively worked in high stress ratio. judging from the fact that the width of life reduction increases in the high stress ratio zone compared to the width of life reduction in the low stress ratio zone. In the fatigue limit of welding methods before corrosion. the welding of SMAW and FCAW shows the same fatigue limit compared to Base metal, and SAW holds the lowest fatigue limit value.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.1
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• pp.65-73
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• 1986

Experiment have been conducted about thin oxide characteristics according to O2/N2 ratio needed for EEPROM cell fabrication. As a result, we think that there is no problem even if we grow oxide layer with large O2/N2 ratio and short exidation time and when the water is implated by As before oxidation, the oxide breakdown field is about IMV/cm lower than that is not implanted. Especially, the thin oxide characteristic seems to be affected largely by wafer cleaning and oxidation in air. On the basis of these, tunnel type EEPROM cell is fabricated by 3um CMOS process and its characteristic is studied. Tunnel oxide thickness(100\ulcorner is chosen to allow Fowler-Nordheim tunneling to charge the floating gate at the desired programming voltage and tunnel area(2x2um\ulcorneris chosen to increase capacitive coupling ratio. For program operation, high voltage (20-22V) is applied to the control gate, while both drain and source are gdrounded. The drain voltage for erase is 16V. It is shown that charge retention characteristics is not limited by leakage in the oxide and program/erase endurance is over 10E4 cycles of program erase operation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.8
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• pp.699-705
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• 2015

Aircraft needs high lift-to-drag ratio and weight reduction of the structure for long endurance flight with a small power. Generally high aspect ratio wing is applied to HALE(High Altitude Long Endurance) aircraft. Also high modulus, and high strength CFRP(Carbon Fiber Reinforced Plastic) has been used in primary structures. and thin mylar(membrane material) film has been applied to skin of wing. As a result, wing is more flexible than the other structures. and the stiffness of thin mylar film has an affect on dynamic stability. In this study, the membrane characteristic of mylar film has been simulated using nonlinear gap elements. And equivalent modeling method using shell elements is presented using the nonlinear simulation result. The linear equivalent model has verified using the results of nonlinear membrane method. Proposed linear equivalent shell model has applied to mode analysis for estimate the effect of mylar mechanical properties on natural frequency.

• Journal of Korean Public Health Nursing
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• v.26 no.3
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• pp.417-427
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• 2012

Purpose: The purpose of this study was to examine the effect of a 12-week combined exercise training program on the body composition, physical fitness levels, and metabolic syndrome profiles of obese women. Methods: Twelve obese women were assigned to the combined exercise training program group. The women underwent training for 70-90 min/d, three times per week for a period of 12 weeks. Paired samples t-tests were performed using SPSS ver. 17.0 for analysis of the results. Results: The results of this study showed that body-composition parameters such as weight, fat-free mass, body fat mass, body-mass index, body fat, waist-hip ratio, basal metabolic rate, and intra-abdominal fat, physical fitness parameters such as muscle strength, muscle endurance, flexibility, and cardiac endurance, and metabolic syndrome biomarkers such as triglyceride levels, high-density lipoprotein cholesterol levels, glucose levels, systolic blood pressure, and waist circumference before participation the training program differed significantly from those after participation in the training program (p<0.05). However, diastolic blood pressure before participation in the training program did not differ significantly from that after participation in the training program (p>0.05). Conclusion: We concluded that a 12-week combined exercise training program could be a good exercise program for improvement of the body composition, physical fitness levels, and metabolic syndrome profiles of obese women.

• Journal of Preventive Medicine and Public Health
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• v.39 no.6
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• pp.462-468
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• 2006

Objectives : The purpose of this study was to gain an understanding of the effects of three exercise types on anthropometric and serum lipids and physiological index factors, which are known to be the three risk factors of cardiovascular disease in male workers. Methods : The experimental study period was 12 weeks. In this study, 30-40's males (N=31) were assigned to 3 experimental groups: regular aerobic(treadmill walking) exercise group, regular anaerobic(muscular endurance) exercise group, irregular aerobic & anaerobic exercise group and a control group using a stratified random assignment method. Results : In relation to anthropometric factors, the regular aerobic & anaerobic exercise groups showed significant decreases in Weight, Broca's index, WC, BMI, WHtR, WHpR and HRrest. With regard to the serum lipid factors, the TC was decreased, but the HDL-c increased among the regular aerobic & anaerobic exercise groups. However, no significant difference was found between the other groups in respect to the LDL-c and TG. Considering the physiological factors, the TC/HD-c, TC-HDL/HDL-c, LDL-C/HDL-c and NON-HDL-c ratios were decreased, but the HDL-c/TC ratio increased among the regular aerobic & anaerobic exercise groups. The TG/HDL-c and HDL-c/LDL-c ratios showed no significant differences between the groups. These results indicated that the positive change for each factor is much larger in the regular exercise groups, especially in the anaerobic exercise group. Conclusions : The results indicate that not only regular aerobic exercise, but also regular anaerobic(muscular endurance) exercise could be utilized in lessening the deleterious effects of the risk index factors for cardiovascular disease.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.6
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• pp.468-477
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• 2014

In this research, how a solar powered HALE (high altitude long endurance) UAV (Unmanned Aerial Vehicle) can climb and reach mission altitude, 18km, starting from the ground using only solar energy. A glider type aircraft was assumed as a baseline configuration which has wing area of $35.98m^2$ and aspect ratio of 25. Configuration parameters, lift and drag coefficients were calculated using OpenVSP and XFLR5 that are NASA open source programs, and climb flights were predicted through energy balance between available energy from solar power and energy necessary for a climb flight. Minimum time climb flight was obtained by minimizing flight velocities at each altitude and total time and total energy consumption to reach the mission altitude were predicted for different take off time. Also, aircraft moving distances due to westerly wind and flight speed were calculated.

• 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.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2927-2934
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• 2023

The influence of the atmospheric radon background on the airborne gamma spectrum can seriously affect researchers' judgement of ground radiation information. However, due to load and endurance, unmanned aerial vehicle (UAV)-borne gamma-ray spectrometry is difficulty installing upward-looking detectors to monitor atmospheric radon background. In this paper, an advanced spectral-ratio method was used to correct the atmospheric radon background for a UAV-borne gamma-ray spectrometry in Inner Mongolia, China. By correcting atmospheric radon background, the ratio of the average count rate of U window in the anomalous radon zone (S5) to that in other survey zone decreased from 1.91 to 1.03, and the average uranium content in S5 decreased from 4.65 mg/kg to 3.37 mg/kg. The results show that the advanced spectral-ratio method efficiently eliminated the influence of the atmospheric radon background on the UAV-borne gamma-ray spectrometry to accurately obtain ground radiation information in uranium exploration. It can also be used for uranium tailings monitoring, and environmental radiation background surveys.

• Steel and Composite Structures
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• v.52 no.2
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• pp.121-134
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• 2024

To investigate the compressive behavior of partially encased recycled aggregate concrete (PERAC) stub columns after exposed to elevated temperatures, 22 specimens were tested. The maximum temperature suffered, the replacement ratio of recycled coarse aggregate (RCA), the endurance time and the spacing between links were considered as the main parameters. It was found that the failure mode of post-heated PERAC columns generally matched that of traditional partially encased composite (PEC) columns, but the flange of specimens appeared premature buckling after undergoing the temperature of 400℃ and above. Additionally, the ultimate strength and ductility of the specimens deteriorated with the elevated temperatures and extended heating time. When 400℃< T ≤ 600℃, the strength reduction range is the largest, about 11% ~ 17%. The higher the replacement ratio of RCA, the lower the ultimate strength of specimens. At the temperature of 600℃, the ultimate strength of specimens with the RCA replacement ratio of 50% and 100% is 0.94 and 0.91 times than that of specimens without RCA, respectively. But the specimen with 50% replacement ratio of RCA showed the best ductility performance. And the bearing capacity and ductility of PERAC stub columns were changed for the better due to the application of links. When the RCA replacement ratio is 100%, the ultimate strength of specimens with the link spacing of 100 mm and 50 mm increased 14% and 25% than that of the specimen without links, respectively. Based on the results above, a formula for calculating the ultimate strength of PERAC stub columns after exposure to high temperatures was proposed.

• Journal of Nutrition and Health
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• v.33 no.1
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• pp.13-22
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• 2000

Effects of high fat diet and/or endurance exercise training on hepatic total and phospholipid(PL) fatty acid compositions were evaluated in rats fed one of the following diets for 31 days. control diet(CD, 5 wt% corn oil) or high fat diet(HFD, 35 wt% corn oil). Half of the rats in each group were exercise-trained regularly on a treadmill for 90 minutes/day during the entire feeding period. Total and PL fatty acid compositions of hepatic lipid extracts were determined by a gas-liquid chromatograph),. Endurance exercise training did not change the daily food intake, but significantly reduced body weight gain and feed efficiency ratio of rats, which were most prominent in animals fed HFD. Exercise training did not significantly change the percentages of ∑saturated fatty acids (SFA) and ∑polyunsaturated fatty acids(PUEA), but decreased the percentage of ∑monounsaturated fatty acids(MUFA) in hepatic total fatty acids, which might be associated with the decrease in (equation omitted) 9-desaturation index of hepatic total fatty acid metabolism. Exercise training significantly lowered the percentages of 16 : 0 and 22 : 5$\omega$3, and increased the percentages of 20 : 1 and 20 : 3$\omega$3 in both total and PL fatty acid compositions in rat liver. Both total fatty acid and PL fatty acid compositions of rat liver responded more sensitively to changes in dietary fat content than to endurance exercise training in this study. Feeding HFD, whoch contains high level of linoleic acid(LA, 18 : 2$\omega$6), significantly decreased the percentages of ∑SFA and $\Sigma$MUFA, and increased the percentages of ∑PUFA and ∑$\omega$6 fatty acids of hepatic total fatty acids. Hepatic total fatty acid composition was affected by dietary fat content and dietary fatty acid composition more sensitively than those found in hepatic PL fatty acid composition. HFD significantly decreased most of desaturation indices, while exercise training significantly decreased elongation index(20 : 5$\omega$3⇒22 : 5$\omega$3) of hepatic total and PL fatty acid metabolism in rats. (Korean J Nutrition 33(1) : 13-22, 2000)