• Journal of the Korean Mathematical Society
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• v.43 no.3
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• pp.623-634
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• 2006

Various methods have been studied to construct a fuzzy regression model in order to present a fuzzy relation between a dependent variable and an independent variable. However, in the fuzzy regression analysis the value of the center point of estimated fuzzy output may be either greater than the value of the right endpoint or smaller than the value of the left endpoint. In the case, we cannot predict the fuzzy output properly. This paper presents sufficient conditions to construct the fuzzy regression model using several methods investigated by some authors and then introduces the censored fuzzy regression model using the censored samples to manipulate the problem of crossing of the center and the end points of the estimated fuzzy number. Examples show that the censored fuzzy regression model is an extension of the fuzzy regression model and also it improves the problem of crossing.

• Journal of Positioning, Navigation, and Timing
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• v.12 no.4
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• pp.349-358
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• 2023

The Satellite-Based Augmentation System (SBAS) plays a significant role in the fields of aviation and navigation: it corrects signal errors of the Global Navigation Satellite System (GNSS) and provides integrity information to facilitate precise positioning. These SBAS systems have been adopted as international standards by the International Civil Aviation Organization (ICAO). In recent SBAS system design, the Minimum Operational Performance Standards (MOPS) defined by the Radio Technical Commission for Aeronautics (RTCA) must be followed. In October 2014, South Korea embarked on the development of a Korean GPS precision position correction system, referred to as Korea Augmentation Satellite System (KASS). The goal is to achieve APV-1 Standard of Service Level (SoL) service level and acquisition of CAT-1 test operating technology. The first satellite of KASS, KASS Prototype 1, was successfully launched from the Guiana Space Centre in South America on June 23, 2020. In December 2022 and June 2023, the first and second service signals of KASS were broadcasted, and full-scale KASS correction signal broadcasting is scheduled to start at the end of 2023. The aim of this study is to analyze the precision of both the GNSS system and KASS system by comparing them. KASS is also compared with Japan's Multi-functional Satellite Augmentation System (MSAS), which is available in Korea. The final objective of this work is to validate the usefulness of KASS correction navigation in the South Korean operational environment.

• Journal of the Korean institute of surface engineering
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• v.38 no.6
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• pp.207-211
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• 2005

In this work a multi-layered nanostructured TiAIN/CrN superlattice coatings was synthesized using closed-field unbalanced magnetron sputtering method and the relationships between their superlattice period (1), micro-structure, hardness and elastic modulus were investigated. In addition, wear test at $500^{\circ}C$ and oxidation resistance test at $900^{\circ}C$ were performed to investigate high temperature properties of these thin films. The coatings were characterized in terms of microstructure and mechanical properties by transmission electron microscopy (TEM) and nano-indentation test. Results from TEM analysis showed that superlattice periods was inversely proportional to the jig rotation speed. The maximum hardness and elastic modulus of 37 GPa and 375 GPa were observed at superalttice period of 6.1 nm and 4.4 nm, respectively. An higher value of microhardness from TiAIN/CrN thin films than either TiAIN (30 GPa) or CrN (26 GPa) was noted while the elastic modulus was approximately an average of TiAIN and CrN films. These enhancement effects in superlattice films could be attributed to the resistance to dislocation glide across interface between the CrN and TiAIN layers. Much improved plastic deformation resistance ($H^3/E^2$) of 0.36 from TiAIN/CrN coatings was observed, compared with 0.15 and 0.16 from TiAIN and CrN, respectively. Also the wear resistance at $500^{\circ}C$ was largely increased than those of single TiAIN and CrN coatings and TiAIN/CrN coatings showed much reduced weight gain after exposure at $900^{\circ}C$ for 20 hours.

• Journal of Convergence for Information Technology
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• v.10 no.9
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• pp.147-153
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• 2020

As demand for drone test flight is rapidly increasing, it is difficult for Goheung Aviation Center alone to meet the test flight demand. Newly developed drones or modified existing aircraft carry potential flight risks due to unpredictable flight performance or poor pilot skill when performing test flights outside the test site. Therefore, it is necessary to ensure sufficient test flight space for the safety verification of manned and unmanned aircraft. Therefore, this study analyzed the status of domestic flight test site and chapter 5 of ICAO DOC 9184-AN / 902 Part 1 (Airport Planning Manual). And to build a comprehensive flight test infrastructure, the methodology for preliminary evaluation of candidate sites for flight test sites and a method for evaluating infrastructure test sites was presented.

• Journal of Advanced Navigation Technology
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• v.4 no.1
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• pp.23-35
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• 2000

In this paper, the design for a PCS base station antenna which is using broadband method by a stacked structure has been studied. The sensitive parameters, such as the parasitic elements, the height of air layer between the upper and lower patch, and the variation of feed point, of the microstrip antenna that has stacked structure in a characteristics variation situation are classified and the characteristics has been investigated through the simulations. A designed antenna has following characters. Impedance bandwidth is Z57.5MHz(VSWR${\leq}$2), horizontal beamwidth is $64.1^{\circ}$, and gain is 14.7dBi. Therefore, it is confirmed the characteristics is good. In this paper, through the designing of a stacked microstrip antenna, we has investigated the availability for Korea PCS base station antenna.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.12
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• pp.1861-1867
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• 2016

Korea augmentation satellite system (KASS), which is a satellite-based augmentation system tailored for Korea, was launched for development in 2014. SBAS is a standard for aviation but it can also be utilized in non-aviation applications. The type and content of transmitted in SBAS data format are restricted. In order to utilize SBAS in fields that require the precision within centimeters, additional information has to be transmitted. It is important that data transmitted in nonstandard SBAS data not affect any operation of SBAS equipment. In this paper, we propose a non-standard SBAS data transmission method applicable to non-aviation applications that does not affect aviation SBAS receivers.

• Journal of Advanced Navigation Technology
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• v.23 no.1
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• pp.8-19
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• 2019

Pilots have used checklist as a valuable tool to improve aviation safety and to reduce human error. A checklist however is too complex for a student pilot to use with less flight experience or time than a commercial pilot. It is agreed upon such complex checklist be a factor to threaten aviation safety for student pilots. This paper has focused on a checklist by dividing it into a couple of basic three flight procedures. Making exploratory case study of student pilots, researchers could analyze the correlation between checklist factors and those of human errors. First of all, it was necessary for student pilots to be educated professional knowledge regarding aircraft structures and engines to perform preflight inspection reducing human errors. Moreover it was recommended student pilots as well as maintenance crew confirm checklist together to enhance aviation safety.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.19 no.1
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• pp.38-48
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• 2011

This paper tried to research a field employee's character, its correlation to service attitude and its impact on service using MBTI characteristics functional indicators, working at airline customer service center. It is proved employees with Sensing Feeing(SF), Intuition Feeling(NF) and Intuition Thinking(NT) have showed lower satisfaction on their duty than employees with Sensing Thinking(ST) have. In analysis of MBTI characteristics' impact on organization-related characteristics, it is also found out employees with Sensing Feeing(SF) and Intuition Feeling(NF) have showed lower trust than employees with Sensing Thinking(ST) have. Considering other controled factors, this paper found that the more job satisfaction employees have, employees with 1 to 5 years of experience on their duty showed more significant service-focused attitude. Moreover, deputy directors or high-ranked people with the higher job satisfaction were seemed to be more service-oriented.

• Korean Journal of Materials Research
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• v.15 no.1
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• pp.54-60
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• 2005

Recently a lots of problems have observed in high densified and high integrated electronic components. One of them is ion migration phenomena, which induce the electrical short of electrical circuit. ion migration phenomena has been observed in the field of exposing the specific environment and using for a long tin e. This study was evaluated the generation time of ion migration and was investigated properly test method through water drop test and high temperature high humidity test. Also we observed direct causes and confirmed generation mechanism of dendritic growth as we reproduced the ion migration phenomena. We utilized PCB(printed circuit board) having a comb pattern as follows 0.5, 1.0, 2.0 mm pattern distance. Cu, SnPb and Au were electroplated on the comb pattern. 6.5 V and 15 V were applied in the comb pattern and then we measured the electrical short time causing by ion migration. In these results, we examined a difference of ion migration time depending on pattern materials, applied voltage and pattern spacing of PCB conductor.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.31 no.1
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• pp.18-25
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• 2023

In recent years, UAM (Urban Air Mobility) has emerged as a solution to these urbanization problems, and many related reports and diverse prospects have been reported. UAM flights are planned to take off and land at a Vertiport located in the city center and fly along a pre-established corridor. In order for UAM to operate safely in the city center, it must ensure a safe flight path that avoids the buildings in the city center and many surrounding obstacles. Therefore, in this study, we compared and examined the installation standards of the obstacle limitation surface necessary for UAM to take off and land safely at the Vertiport. First, we analyzed the helicopter obstacle limitation surfaces in Japan and overseas, and the UAM Vertiport installation standards and obstacle limitation surface application standards recently announced at the FAA and EASA. It identified differences and similarities between heliport and Vertiport, and considered improvements to domestic helicopter obstacle limitation surfaces and criteria that could meet FAA and EASA standards.