• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.3
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• pp.109-116
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• 2007

The present study examined mechanical properties according to the change of outer circumference in the friction welding of A2024-T4 stock, which is used much as aircraft structure, truck wheel, stainless materials and A2024-T4 stock with 10 hollow at the center. Welding conditions were fixed at RPM 2,000rpm, friction pressure of 50MPa, friction time of 1.5sec, upset pressure of 120MPa and upset time of 2.0 seconds. From the result of this study were drawn conclusions as follows : According to the result of a tensile strength test, the solid shaft showed linear increase of tensile strength with the change of outer circumference, the hollow shaft showed maximum tensile stength when the length (L) was 2mm and decrease of tensile strength with the change of outer circumference, hardness appeared to increase and then decrease for welding interface, and it showed maximum hardness 155Hv at L=5mm of the solid shaft. Bending strength increased linearly far change of the distance (L) of outer circumference in the solid shaft and then decreased linearly in the hollow shaft. the result of examining tissue, the tissue grew finer around the welding interface and divided the basic material and the welding surface.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.4
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• pp.114-122
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• 2002

The integration of the landing gear system is a complex relationship between the many conflicting parameters of shock absorption, minimum stow area, complexity, weight and cost. Especially ground impact load and dynamic behaviors greatly influence design load of landing gear components as well as load carrying structural attachment. This study investigates ground impact load and dynamic behaviors of the T-50 landing gear system using ADAMS. Taking into account for various operational/environmental conditions, an analysis of shock absorbing characteristics at ground impact is performed with experience derived from a wide range of proprietary designs. Analytical results are presented for discussing the effects of aircraft horizontal and vertical speed, landing attitudes, shock absorbing efficiency. This analysis leads us to the conclusion that the proposed program is shown to be a better quantitative one that apply to a new development and troubleshooting of the landing gear system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.5
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• pp.507-513
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• 2008

In this paper, we present a development of an Avionics Hot Bench(AHB) used for the verification of operational flight programs and fault analysis using various simulation and stimulation software. We propose an application of the open system architecture to develop the AHB which can be used for the development of a real aircraft avionics system. In the design of the AHB, to reduce the development period and cost we use as many as commercial off-the-shelf hardware and software items. The developed AHB is compared with the existing proven AHB which was used for T-50 avionics system development. Thorough comparison between the test results using the developed AHB and those using the existing AHB is performed and the overall comparison results are very satisfactory.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.6
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• pp.117-125
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• 2004

This paper describes the test technique for the full-scale airframe durability test according to the military handbook(MIL-HDBK-1530) and ASIP(Aircraft Structure Integrity Program) to evaluate structural integrity and to obtain basic data for IPA(Initial Production Approval) of the Korean advanced trainer(T-50). This paper covers the full-scale airframe floating setup technique, the optimized test load simulation method, test rig design technique, test setup design and installation techniques, test safety device design and operation technique, and durability test results. As 1st life durability test was successfully performed, it was confirmed that this method is available in a full-scale airframe structural test.

• Industrial Engineering and Management Systems
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• v.11 no.4
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• pp.346-352
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• 2012

While systems engineering has been widely applied to complex system development, some evidences are reported about major budget and schedule overruns in systems engineering applied. On the other hand, many organizations have been deploying Design for Six Sigma (DFSS) to build Six Sigma momentums in the area of design and development for their products and processes. To explore the possibility of having a DFSS complement systems engineering process, this process reviews the systems engineering with their categories of effort and DFSS with its methodologies. A comparison of the systems engineering process and DFSS indicates that DFSS can be a complement to systems engineering for delivering higher quality products to customers faster at a lower cost. We suggest a simplified framework of systems engineering process, that is, PADOV which was derived from the generic systems engineering process which has been applied to the development of T-50 advanced supersonic trainer aircraft by Korea Aerospace Industries (KAI) with technical assistance of Lockheed Martin. We demonstrated that each phase of PADOV framework is comprehensively matched to the pertinent categories of systems engineering effort from various standards.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.4
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• pp.255-267
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• 2020

Under SLD conditions, due to the large size of droplets, physical phenomena such as wall-droplet interaction and deformation have a significant effect on the icing process. Accordingly, many studies have been conducted in order to computationally simulate SLD effects. As one of the efforts, post-processing method have been proposed to describe wall-droplet interaction effect, which modified collection efficiency using Wright model. However, since the model doesn't properly consider the wall condition, it still overestimated collection efficiency and impingement limit. To solve this problem, impingement areas were divided into 3 different regions, and the post-processing method was introduced with the new wall-droplet interaction model developed based on Bai and Gosman rebound model. In order to consider the effect of deformation, the most suitable model was selected by comparing the deformation models used in the various icing codes. As a result, the modified post-processing method showed improved accuracy in predicting the impingement limits and collection efficiency by further estimating mass flux loss due to rebound, and it was observed that the result was the closest to the experimental data when the deformation effect was included by using Wiegand model.

• The Korean Journal of Community Living Science
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• v.17 no.4
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• pp.151-161
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• 2006

This study was made to find out how health practice affect on nutrition status of the college freshmen in male and female. 400 freshmen students in 4year colleges were surveyed. Questionnaire and blood analysis were made. The contents of questionnaire contained general characteristics, health practice behavior, and food intake. The physical measurement included height, weight and blood pressure. The questions for health practice were about drinking, smoking, BMI, skipping breakfast and sleeping. Nutrient intake was expressed by DDS(Dietary Diversity Score by 5 food groups) and DVS (Dietary Variety Score) and 24-hrs recall method was used to find out the quantity of daily food intake. EAR% was calculated and NAR and MAR were produced. The results are as follows: 1) BMI was $22.77kg/m^2$ for males and $20.42kg/m^2$ for females. The ratio maintaining normal weight indicated by BMI of 18.5-23 was higher(p<0.001) for female students(63.2%) than males(56.5%). The ratio of overweight with over $23kg/m^2$ of BMI was 28.5% for males and 8.8% for females(p<0.001). 2)The ratio of drinking students was 59.4% for males and 40.6% for female(p<0.001). And the ratio of smoking students was 95.2% for males and 4.8% for females(p<0.001). 3) The ratio of poor health practice group was 35.7% for males and 25.5% for females, and that of excellent one was 25.4% for males and 33.1% for females(p<0.05). 4) In NAR, the lowest ratio was observed for the intake of Ca, Fe, Vitamin C and Vitamin $B_2$. The intake of Fe, Vitamin $B_2$ and phosphorus were different significantly according to sexuality. For Fe, female students showed lower level than male students(p<0.001). For Vitamin $B_2$, and phosphorus female students showed higher level(p<0.001). 5) In MAR, there was no difference according to sexuality in almost all of the ingredients. 6) For energy intake, male and female students showed 59% and 66% of EAR and it was insufficient for them. 7) For protein, more than 100% was obtained. The lowest ratio was observed for the intake of vitamin C 50.8%, Ca 53.6% and Fe 65.1% of EAR were obtained. The lowest intake ratio and for the intake of Fe female students obtained just 37.5% of EAR showing high risk of anemia. The intake of energy(p<0.001), phosphorus(p<0.01), niacin(p<0.05), Fe(p<0.001), and Vitamin $B_2$ (p<0.001) were different significantly according to sexuality. For Fe, female students showed lower level than male students(p<0.001). For energy, phosphorus, niacin, and Vitamin $B_2$ female students showed higher level(p<0.001) than male students. 8) For blood pressure, male students showed normal level of 120.7/79.1 mmHg, however, female students showed 114.5/75.4 mmHg lower than male (p<0.001). 9). In blood, for hemoglobin female students showed significantly lower level than that of male(p<0.001). T-Cholesterol and HDL-Cholesterol female students showed higher level than males (p<0.001), And for triglyceride male students showed higher level than females(p<0.001). Ca and Fe female students showed lower level (p<0.001).