• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.7
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• pp.469-478
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• 2019

Multirotor configurations such as VTOL and urban air mobility have been focused on today due to the high maneuverability. Aerodynamic and aeroacoustic characteristics of multirotor have much difference to those of a single rotor. In this study, a numerical analysis based on the free wake vortex lattice method is used for identifying the wake interaction effect. In order to compare the various configurations and operating conditions, the effects of the spacing between the rotors in hovering flight and the effects of the advancing ratio and the formation in forward flight are discussed. In the hovering flight, the unsteady loading of multirotor changes periodically and loading fluctuation increases as decreasing the spacing. It causes the variation in unsteady loading noise and the noise directivity pattern. In the forward flight, the difference in loading fluctuation and noise characteristics are observed according to the diamond and square formation of rotors. By comparing with results of single rotor analysis, multirotor configurations have different directivity pattern and amplitude of loading noise according to the location of each rotor. As a result, wake interaction effect becomes a highly important factor for aerodynamic and aeroacoustic analysis according to multirotor configurations and operating conditions.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.384-386
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• 2014

As the type of property data of military terrain analysis map is using FACC of DIGEST, there is a limitation in utilizing a domestic thematic map which is in use of other type of property data. However, even though the attempts to utilize the domestic thematic map are made at military sites, the study has not been conducted enough. Therefore, we defined it by matching the property data necessary for the military terrain analysis cartography and property of the domestic thematic map, and analyzed in accordance with the method to analyze the cross-country movement roads specified in FM 5-33. But, there was no data for the diameter of trees in the vegetation map among a terrain analysis map, whereas there being data for the sort of trees. As the diameter of trees can be broken through to the extent of certain diameters by tracked vehicles, they are the factors necessary in analyzing. In this study, the research was conducted focusing on calculating the diameters for some trees described in a stand yield table by using the age-class for trees in a forest floor map with a scale of 1:5000 and calculating the diameters of trees by using the diameter-class for the diameters of other trees.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.605-611
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• 2019

The fuel sloshing due to the rapid manoeuvre of the aircraft causes significant loads on internal components, which may break components or piping. In particular, a significant load is applied to the joint of the external fuel tank by sloshing movement, which may affect the safety of the aircraft when the joint of the external fuel tank is damaged. Therefore, in order to improve the survivability of aircraft and crew members, the design of external fuel tanks, and joints should be performed after evaluating the sloshing load through a numerical analysis of the fuel sloshing conditions. In this paper, a numerical analysis was performed on the sloshing test of the external fuel tank for rotorcraft. ALE (Arbitrary Lagrangian Eulerian) technique was used, and the test conditions specified in the U.S. Military Specification (MIL-DTL-27422D) was applied as the conditions for numerical analysis. As a result of the numerical analysis, the load on the joint of the external fuel tank was calculated. Moreover, the effects of sloshing movement on structural soundness were assessed through analysis of stress levels and margin of safety on metal fittings and composite containers.

• Korea and Global Affairs
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• v.3 no.1
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• pp.77-106
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• 2019

The purpose of this paper is to propose measures to respond to NK's nuclear threat by applying the concept of offset strategy in the US and the fourth industrial revolution technology innovation. Through this study, the concept, technology, and organization were examined to find measures to counter the NK's nuclear threat. The concept was to review the US offset strategy and consider the strategy of paralyzing the enemy's center as an operational concept. And the technologies that can support the 4th Industrial revolution and the 3rd US offset strategy. The organization analyzed the implications for the reform of the National Defense Reform 2.0 and the reorganization of the acquisition of the US DoD. Through the US offset strategy review, it is necessary to reconcile the strategic concepts of Korea and the US, and the interoperability of technologies and the cooperation fields of the ROK-US alliance. In addition, it is necessary to strengthen the capability of responding to NK's nuclear threat in connection with the 4th Industrial Revolution and the National Defense Reform 2.0 promotion. It is necessary to develop the concept of operational performance applying the new paradigm for the NK's nuclear issue and to apply advanced science and technology. And that it is necessary to organize effectively in conjunction with the National Defense Reform 2.0.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.9
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• pp.709-719
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• 2021

Recent progress in analysis and flight simulation methods enables wider use of a virtual certification and reduces number of certification flight tests. Aerodynamic database (AeroDB) is one of the most important components for the flight simulation. It is composed of aerodynamic coefficients at a range of flight conditions and control deflections. This paper proposes and efficient method for construction of AeroDB that combines Gaussian Process based Variable Fidelity Modeling with adaptive sampling algorithm. A case study of virtual certification of a F-16 fighter is presented. Four AeroDB were constructed using different number and distribution of high-fidelity data points. The constructed database is then used to simulate gliding, short pitch, and roll response. Compliance with certification regulations is then checked. The case study demonstrates that the proposed method can significantly reduce number of high-fidelity data points while maintaining high accuracy of the simulation.

• Journal of Korean Library and Information Science Society
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• v.51 no.4
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• pp.83-100
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• 2020

The importance of data publishing in the open-science era is increasing as it can contribute to other scientific discoveries by accelerating the sharing of research data, improving accessibility and citability, and providing standardized technical documentation for research data. In addition, the need for data papers is emerging as a way for data papers to maintain a status equivalent to research papers, and the publication of data journals is on the rise as a new type of scholarly publishing. In particular, the field of Ecology is a field where large-scale research data are produced and managed, thus the data journal publishing in this field is active worldwide. On the other hand, the research on data journal is in its early stages in Korea, and there is no data journal in the field of Ecology. Thus, this study explores and presents strategies for publishing data journals in the ecological field. First, we investigate the publishing status of domestic and international data journals and the publication status of domestic journals. Then, we conducted a focused group interview with experts of scholarly publishing, open access policy and journal publishing in the field of Ecology. Finally, based on the survey and the expert FGI's results, strategies are suggested in terms of publishing data journals in the field of ecology, organizing and publishing journals, organizing journal editors, and receiving manuscripts.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.434-439
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• 2021

We assessed the effects of intravenous (IV) ascorbic acid administration on fatigue in women undergoing laparoscopic myomectomy. We analyzed the secondary endpoint results of a randomized, double-blind, placebo-controlled trial. Fifty patients undergoing laparoscopic myomectomy received IV ascorbic acid (2g) or placebo (randomly 1:1 ratio) intravenously during surgery. On day 2 post-surgery, we measured the level of fatigue using the Brief Fatigue Inventory-Korean version. Forty-five women (experimental arm 23, control arm 22) were eligible for analysis after 5 women (experimental arm 2, control arm 3) were excluded due to withdrawal of consent, cancellation of surgery or non-measurement of the endpoints. The baseline and operative characteristics were similar between arms and the global fatigue score of the experimental arm (4.56 ± 2.63) was not significantly different from that of the control arm (5.21 ± 2.02, P = 0.351). However, the fatigue score of the experimental arm tended to be lower than that of the control arm in most domains. IV ascorbic acid administration did not significantly reduce the level of fatigue in women undergoing laparoscopic myomectomy as compared to placebo. More research is needed to better understand the effects of ascorbic acid on fatigue in surgical patients.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.777-783
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• 2021

Aircraft are affected by various vibrations during maneuvering. These vibrations may have a fatal effect on the survival of aircraft in some cases, so the safety of components applied to the aircraft should be proven against various vibrations through random vibration analysis. In this study, the structural robustness of an external fuel tank and pylon for military aircraft was evaluated under random vibration conditions using commercial software, MSC Random. In the random vibration analysis, a frequency response analysis was performed by imposing a unit load on the boundary condition point, and then excitation was performed with a PSD profile. In this process, the required mode data was extracted through a modal analysis method. In addition, the random vibration profile specified in the US Defense Environment Standard was applied as random vibration conditions, and the PSD profile given in units of G's was converted into units of gravitational acceleration. As a result of the numerical analysis, we evaluated the structural robustness of the external fuel tank and pylon by identifying the safety margins of beam elements, shell elements, and solid elements in a numerical model for random vibration in the x, y, and z directions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.2
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• pp.95-106
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• 2021

Side-jets enable the immediate maneuver of a missile compared to control surfaces; however, they may cause adverse effects on aerodynamic coefficients, for they interfere with freestream. To find out the impact of side-jets on aerodynamic coefficients, we simulate side-jets as air gas and utilize multi-fidelity models to evaluate differences between aerodynamic coefficients obtained with and without side-jets. We computed differences in aerodynamic coefficients to investigate side-jet effects for the changes of a Mach number, a bank angle, and an angle of attack. As a result, asymmetrically developed side-jets affect the longitudinal force and moment coefficients, and the lateral force and moment coefficients drastically change in-between -30 and 30 degrees of bank angles. In contrast, side-jets hardly influence the axial force coefficients. As for the axial moment coefficient, we could not determine the side-jet effect due to a lack of aerodynamic coefficient samples in the Mach number. All in all, we confirm that side-jets lead to the change of a missile attitude as they considerably vary the longitudinal and lateral aerodynamic coefficients.

• The Journal of the Korea Contents Association
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• v.21 no.1
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• pp.649-661
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• 2021

Over recent years, there have been more comprehensive studies conducted word-widely on the WLB covering not only the conflicting relationships between work and life but also facilitating relationships between work and life, in a method of classifying whether a conflict or a facilitation was derived from the work or from the life. However, such studies are hardly identified in Korea. The objective of this study is, therefore, to examine the effect of the WLB on innovative behavior in Korean society, when the WLB are subdivided into three sub-variables defined as work-life conflict, life -work conflict, and work-life facilitation, and to determine the mediated effect of psychological well-being(hedonic well-being and eudaimonic well-being). The hypothesis was verified using factor analysis, descriptive statistics, and regression analysis in questionnaires collected from 299 office workers. As a result, the study found that work-life conflict and work-life facilitation significantly effected psychological well-being and innovative behavior. However, life-work conflict was not a significant factor on hedonic well-being and innovative behavior. In addition, eudaimonic well-being showed mediating effect to the relationship between WLB and innovative behavior, while hedonic well-being did not effectively mediate them.