• Journal of Aerospace System Engineering
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• v.12 no.5
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• pp.24-31
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• 2018

The objectives of this study is to carry out Bird strike analysis and tests of a blade antenna of aircraft. FEMs (Finite Element Models) were created for the analysis, while dummy and real antennas were used for the bird strike tests. In the analysis, birds were modeled with SPH (Smooth Particle Hydrodynamics) method, and the behaviors of the bird, antenna, and joint structure between antenna and aircraft fuselage were simulated with the FSI (Fluid-Structure Interaction) method. After the bird strike test was performed, the results of the analysis and test showed that they had a positive relationship. The damage of antenna and bolted joint was checked, and the structural integrity of the airframe was proved.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.5
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• pp.319-325
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• 2019

The main purpose of this study is to compare the bird strike analysis result of the radome composed of composite laminate and sandwich structure attached to aircraft with test result. First of all, we generated bird model which has water properties through SPH(Smoothed Particle Hydrodynamics) method. And then bird strike analysis was conducted with initial velocity of bird measured from bird strike test. From analysis result we investigated whether structural failure occurred or not onto the radome and compare maximum displacement of the radome structure with test result. Also reliability of numerical analysis model was confirmed through time-dependent pressure trend on this collision process matched existing research result. Furthermore, we confirmed that failure behavior of the radome can be affected by density of the particles in the bird model.

• Journal of the Korea Institute of Military Science and Technology
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• v.26 no.3
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• pp.302-312
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• 2023

This paper describes the analysis of lightning strike zoning, the indirect lightning data simulation and the protection design for lightning indirect effects of equipment by lightning strike for unmanned aircraft consisting of composite wings. Through the analysis of lightning strike zoning according to the external shape of unmanned aerial vehicles, the structure areas that should be protected during lightning strike is derived, and the protection requirements of lightning indirect effects for flight critical equipments and equipment that must be operated upon lightning strike was derived. Lightning protection levels according to the location of mounting equipment and surrounding structure materials for each equipment was derived, and the protection design of the unmanned aerial vehicle with composite structures was also proposed from direct effect of lightning. Later, the lightning protection technology will be verified by the ground test of lightning direct and indirect effects.

• Communications for Statistical Applications and Methods
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• v.19 no.6
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• pp.819-835
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• 2012

A floating-strike lookback call (or put) option gives the holder the right to buy (or sell) at some percentage of the lowest (or highest) price of the underlying asset. This paper will propose an outside lookback call (or put) option that gives the holder the right to buy (or sell) one underlying asset at its guaranteed floating-strike price that is some percentage times the smaller (or the greater) of a specific guaranteed amount and the lowest (or highest) price of the other underlying asset. In addition, this paper derives explicit pricing formulas for these outside lookback options. Section 3 and Section 4 assume that the underlying assets pay no dividends. In contrast, Section 5 derives explicit pricing formulas for these options when their underlying assets pay dividends continuously at a rate proportional to their prices. Some numerical examples are also discussed.

• East Asian mathematical journal
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• v.35 no.1
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• pp.59-66
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• 2019

In this paper we study implicit-explicit (IMEX) methods combined with a semi-Lagrangian scheme to evaluate the prices of fixed strike arithmetic Asian options under jump-diffusion models. An Asian option is described by a two-dimensional partial integro-differential equation (PIDE) that has no diffusion term in the arithmetic average direction. The IMEX methods with the semi-Lagrangian scheme to solve the PIDE are discretized along characteristic curves and performed without any fixed point iteration techniques at each time step. We implement numerical simulations for the prices of a European fixed strike arithmetic Asian put option under the Merton model to demonstrate the second-order convergence rate.

• Journal of Korean Academy of Nursing Administration
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• v.7 no.3
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• pp.511-529
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• 2001

Purpose : To analyze organization variables related to nursing between the doctors' strike and normal periods. Methods : The sample consisted of 1,220(600 for doctors' strike and 620 for normal periods) nurses working in 5 hospitals. Six instruments were used for data collection including Job Activity Scale(JAS; Laschinger, 1994), Organization Relationship Scale(ORS; Laschinger, 1994), Interpersonal Support Scale(developed by Firth et al., 1986 and revised by Ahn(2000), Self-efficacy Scale(Riggs & Knight, 1994),Job Satisfaction Scale(Slavitts et al., 1978), and Organizational Commitment Questionnaire(OCQ; Mowday et al., 1979). Results : There were significant differences among variables(i.e., formal power, interpersonal support, self-efficacy and organizational commitment)between doctors' strike and normal periods. The formal power was high during the normal period, however interpersonal support, self-efficacy and organizational commitment were high during the doctors' strike. Conclusion : Interpersonal support, self-efficacy and job satisfaction were change by working conditions, but organizational commitment was not changed by working conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.11
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• pp.983-989
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• 2007

The bird strike simulation is a problem characterized by a high degree of uncertainty. It deals with nonlinear dynamics, complicated models of bird materials and geometry, as well as a plenty of possible boundary and initial conditions. In this complex field, uncertainty management plays an important role. This paper aims to assess the effect of input uncertainty of bird strike analysis on the impact behavior of the leading edge of the WIG(Wing in Ground Effect) craft obtained with finite element analysis using LS-DYNA 3D. The uncertainties of the bird strike simulation arise due to imprecision or lack of information, due to variability or scatter, or as a consequence of model simplification. These uncertain parameters are represented by fuzzy numbers with their membership functions quantifying an initial guess for the actual value of the model parameter. Using the transformation method as a special implementation of fuzzy arithmetic, the model can be analyzed with the intention of determining the influence of each uncertain parameter on the overall bird strike behavior.

• Earthquakes and Structures
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• v.20 no.1
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• pp.109-122
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• 2021

Significant progress in the oil and gas industry advances the application of pipeline into an intelligent era, which poses rigorous requirements on pipeline safety, reliability, and maintainability, especially when crossing seismic zones. In general, strike-slip faults are prone to induce large deformation leading to local buckling and global rupture eventually. To evaluate the performance and safety of pipelines in this situation, numerical simulations are proved to be a relatively accurate and reliable technique based on the built-in physical models and advanced grid technology. However, the computational cost is prohibitive, so one has to wait for a long time to attain a calculation result for complex large-scale pipelines. In this manuscript, an efficient and accurate surrogate model based on machine learning is proposed for strain demand prediction of buried X80 pipelines subjected to strike-slip faults. Specifically, the support vector regression model serves as a surrogate model to learn the high-dimensional nonlinear relationship which maps multiple input variables, including pipe geometries, internal pressures, and strike-slip displacements, to output variables (namely tensile strains and compressive strains). The effectiveness and efficiency of the proposed method are validated by numerical studies considering different effects caused by structural sizes, internal pressure, and strike-slip movements.

• Journal of the Korean earth science society
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• v.29 no.5
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• pp.437-445
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• 2008

We analyzed fault plane solutions of the recent twenty-two earthquakes which occurred from 2004 to 2006 in the central part of the Korean Peninsula by using P- and S-wave polarities along with SH/P amplitude ratios. The fault plane solution shows that strike-slip fault is dominant here, especially for the events with local magnitude equal to or greater than 3.0. However, some events with local magnitude less than 3.0 show normal fault or strike-slip fault with normal components. In the case of strike-slip fault, its orientation is almost in the direction of NNE-SSW to NE-SW almost parallel to the general trend of faults, while the compressional axis of the stress field trends ENE to E-W. The result is almost consistent with the stress field in and around the Korean peninsula, as reported previously. We cannot give any appropriate explanations to the normal faulting events along the western offshore and inland areas whether it is related to the local stress changes or tectonically unidentified extensional structures. Thus, an extension of investigations is desirable to clarify the cause of such phenomena.

• Journal of Electrical Engineering and Technology
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• v.10 no.6
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• pp.2356-2363
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• 2015

Localization of lightning strike point (LSP) in the forest is modeled to mitigate the forest fire damage. Though forest fire ignited by lightning rarely happens, its damage on the forest is grievousness. Therefore, predicting accurate location of LSP becomes crucial in order to control the forest fire. In this paper, we proposed a new hybrid localization algorithm by combining the received signal strength (RSS) and the received signal strength ratio (RSSR) to improve the accuracy by mitigating the environmental effect of lightning strike location in the forest. The proposed hybrid algorithm employs antenna theory (AT) model of cloud-to-ground (CG) return stroke lightning channel to forecast the location of the lightning strike. The obtained results show that the proposed hybrid algorithm achieves better location accuracy compared to the existing RSS method for predicting the lightning strike location considering additive white Gaussian noise (AWGN) environment.