• Journal of Aerospace System Engineering
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• v.14 no.spc
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• pp.49-55
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• 2020

The average probability of a lightning strike to transport aircraft operating in airline service has been estimated to be approximately one strike in every year (or one strike per 1,000 through 20,000 flight hours). The important thing is not the probability of a lightning strike to aircraft, but the fact that aircraft is struck by lightning. Therefore, lightning protection design for aircraft should be qualified and compliance with airworthiness standards related to lightning protection must be substantiated in the process of certification. In this paper, I studied means of compliance for lightning protection through analysis of some test cases, including the KC-100 airplane that firstly obtained civil type certificate in Korea. Based on this paper, it will be also necessary to study on the effect of lightning for space launch vehicles.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.194-197
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• 2017

Aircraft engine and auxiliary power units are certified in processes of design, production according to airworthiness requirements. The aircraft engines shall demonstrate compliance with the design and production through the Type Certificate and the auxiliary power unit shall demonstrate compliance with the design and production through the Technical Standards Order Approval. MOLIT(Ministry of Land, Infrastructure and Transport) established the law and the airworthiness requirements for aircraft engines such as KAS Part 33 but didn't issue the Technical Standards Order for auxiliary power unit. In this paper, we proposed and explained the plan for improvement of our aircraft engines industry through building and expanding the certification infra-structure for aircraft engines and auxiliary power unit.

• Journal of Korea Society of Industrial Information Systems
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• v.16 no.3
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• pp.47-56
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• 2011

To apply Genetic algorithm toward document clustering, appropriate individual structure is required. Document clustering with the genetic algorithms (DCGA) uses the centroid vector type individual structure. New document clustering with the genetic algorithm (NDAGA) uses document allocated individual structure. In this paper, to find more suitable object structure and process for the document clustering, calculation, amount of calculation, run-time, and performance difference between the two methods were analyzed. In this paper, we have performed various experiments using both DCGA and NDCGA. Result of the experiment shows that compared to DCGA, NDCGA provided 15% faster execution time, about 5~10% better performance. This proves that the document allocated structure is more fitted than the centroid vector type structure when it comes to document clustering. In addition, NDCGA showed 15~25% better performance than the traditional clustering algorithms (K-means, Group Average).

• East Asian mathematical journal
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• v.24 no.5
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• pp.527-545
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• 2008

One of the education purpose of the section "Figures" in the eighth grade is to develop students' deductive reasoning ability, which is basic and essential for living in a democratic society. However, most or middle school students feel much more difficulty or even frustration in the study of formal arguments for geometric situations than any other mathematical fields. It is owing to the big gap between inductive reasoning in elementary school education and deductive reasoning, which is not intuitive, in middle school education. Also, it is very burden for students to describe geometric statements exactly by using various appropriate symbols. Moreover, Usage of the same symbols for angle and angle measurement or segments and segments measurement makes students more confused. Since geometric relations is mainly determined by the measurements of geometric objects, students should be able to interpret the geometric properties to the algebraic properties, and vice verse. In this paper, we first compare and contrast inductive and deductive reasoning approaches to justify geometric facts and relations in school curricula. Convincing arguments are based on experiment and experience, then are developed from inductive reasoning to deductive proofs. We introduce teaching methods to help students's understanding for deductive reasoning in the textbook by using stepwise visualization materials. It is desirable that an effective proof instruction should be able to provide teaching methods and visual materials suitable for students' intellectual level and their own intuition.

• Honam Mathematical Journal
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• v.1 no.1
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• pp.61-75
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• 1979

In this explanation. we shall describle how the de Rham's cohomology on a n-dimensional $C^{**}$-manifold is constructed. The Čech's cohomology defined by only topological structure of $C^{**}$-manifold has a crack that it is dependent on the covering of a $C^{**}$-manifold. At the end of explanation we shall prove that the de Rham's cohomology is isomorphic to Čech's cohomology which is made by simply covering.

• Journal for History of Mathematics
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• v.21 no.2
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• pp.55-70
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• 2008

This study is about the Data which is one of Euclid's writing. It dealt with the organization of contents, formal system and mathematical meaning. First, we investigated the organization of contents of the Data. Second, on the basis of this investigation, we analyzed the formal system of the Data. It contains the analysis of described method of definition, proposition, proof and the meaning of 'given'. Third, we explored the mathematical meaning of the Data which can be classified as algebraic point of view, geometric point of view and the opposite point of view to 'The Elements'.

• Journal for History of Mathematics
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• v.20 no.4
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• pp.23-48
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• 2007

This study begins from posing a problem, 'formal introduction of mathematical induction in school mathematics'. Most students may learn the mathematical induction at the level of instrumental understanding without meaningful understanding about its meaning and structure. To improve this didactical situation, we research on the historical progress of mathematical induction from implicit use in greek mathematics to formalization by Pascal and Fermat. And we identify various types of thinking included in the developmental process: recursion, regression, analytic thinking, synthetic thinking. In special, we focused on the role of regression in mathematical induction, and then from that role we induce the implications for teaching mathematical induction in school mathematics.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.109-116
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• 2008

In order to test the adhesive capacity of carbon fiber sheet, a static loading method for bending-behavior-type beam specimens, cut in half was developed and test was conducted with compressive strength of concrete set as the test parameter. The tests were performed to prescribe adhesive shear strength based upon the result of shear failure as well as verification of testing method. First of all, the test method proved to be reliable in determining the adhesive shear strength. The test result also exhibited two types of variations in adhesive shear strength. Among two types of variations, average and minimum values for adhesive shear strength, relatively stable results, 3.41MPa and 2.11MPa, respectively. Particularity in the adhesive shear strength with respect to compressive shear strength was not found.

• Journal of Advanced Navigation Technology
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• v.27 no.5
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• pp.621-628
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• 2023

This study derived a reverse engineering procedure for verifying the design identity of original parts and developed parts for PMA(Parts Manufacturer Approval) and STC(Supplemental Type Certificate) of metal brake pads for transport aircraft, which are critical parts among aircraft parts and equipment. In Korea, the regulations for reverse engineering procedures are regulated by the Parts Manufacturer Approval Guidelines, and in the United States, AC No. 21. 303-4. In the reverse engineering for the brake pad, the detailed procedures for each component were determined by selecting verification test items to confirm identity based on sample quantity, dimensional tolerance, mechanical property measurement, material, weight and volume characteristics for each component. In addition, as a result of analyzing the regulation of Korea and United States, in the case of Korea, it is necessary to establish technical standards for braking systems for transport aircraft and regulations related to flight tests.

• Journal of Advanced Navigation Technology
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• v.27 no.6
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• pp.821-827
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• 2023

In this study, the aircraft technical standards of the Korea and the United States were analyzed to derive the dynamometer test procedure required to prove the compatibility for flight test certification of the metal brake pad for transport aircraft. Since the design modification of the brake systems is classified as a major change, the STC(Supplemental Type Certificate) and the PMA(Parts Manufacturer Approval) are required. In accordance with the TSO-C135a, the technical standard order for brake system in the United States, the design landing-stop test, accelerate-stop test, and most severe landing stop test were selected among the test items for flight test. The conditions for the dynamometer test are determined according to the specifications provided by aircraft manufacturer, and the brake pad condition, deceleration, and the number of test are defined according to the TSO-C135a.