• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.10
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• pp.1265-1270
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• 2018

One of the ways to improve the stability of power facilities used in power systems is to use power surge arresters and to protect against transient overvoltages and surges in normal operation. Also it is important to reduce the impact of lightning strikes because lightning can create overvoltage in the grid of the wind turbine and affect power quality. So This paper analyzes the effects of overvoltage and adjacent turbines due to single strike and multi strike to ground impedance changes when the surge arrester is deteriorated in a wind power farm.

• Journal of Korean Institute of Industrial Engineers
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• v.42 no.6
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• pp.386-394
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• 2016

In this research, in order to optimize the multi-objective function effectively, we suggested the optimization model to maximize the total destruction of ground targets and minimize the total damage of aircrafts and cost of air munitions by using goal programming. To satisfy the various variables and constraints of this mathematical model, the concept of air strike package is applied. As a consequence, effective attack can be possible by identifying the prior ground targets more quickly. This study can contribute to maximize the ROK air force's combat power and preservation of high value air asset in the war.

• Management Science and Financial Engineering
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• v.17 no.2
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• pp.99-129
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• 2011

This paper analytically studies how to choose hedging instrument for firms with steady operating cash flows from value maximization perspective. I derive a formula to determine option's optimal strike that makes hedged cash flow have the best monetary payoff given a hedger's view on the underlying asset. I find that not only the expected mean but also the expected standard deviation of the underlying asset in relation to the forward price and the implied volatility play a crucial role in making optimal hedging decision. Higher moments play a certain part in hedging decision but to a lesser degree.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.14 no.4
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• pp.87-93
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• 2006

The black-tailed gull chicks, Larus crassirostris, recognize various adult voice signal base on the simple patterns. We investigated behavior change in black-tailed gull chicks through physical manipulation of mew call. They were playback in four situations differing in physical character: 1) frequency manipulation only, 2) duration manipulation only, 3) call intensity(dB) manipulation only, and 4) call interval manipulation only. We observed occurrence of different response of the chicks, which were categorized into two behaviors(hidden and return behavior). The manipulated frequency, duration, and intensity were directly correlated. The chicks exposed to only manipulated call interval(0.5, 1sec) made significantly more hidden and return behavior. Adult black-tailed gull only increased flight time on manipulated call interval. The results suggest that black-tailed gulls use short call interval for alarm signal. The analysis of alarm signal provides an important on basic study of bird strike.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.228-234
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• 1998

To interpret the relationship between movement of the Yangsan fault and tectonics around the Korean peninsula, the six sequential paleostresses were reconstructed from 1, 033 striated small faults which were measured at 37 outcrops along the strike of the Yangsan fault. And, the relationship between these paleostresses of the Yangsan fault and the tectonic events around the Korean peninsula were compared. As compared with the tectonic history around the Korean peninsula, the movement of the Yangsan fault is interpreted as follows; The initial feature of the Yangsan fault was formed with the development of extension fractures by the NW-SE extension. The fault experienced a right-lateral strike-slip movement continuously. The movements had been continued until the Late Miocene age, which was the most active period in faulting. The left-lateral strike-slip movement was followed by subsequent tectonic events. In the last stage, the fault acted with a slight extension or right-lateral movement.

• Journal of the Korean institute of surface engineering
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• v.32 no.3
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• pp.224-234
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• 1999

An attempt was made to characterize the relationship between pretreatment processes, electrolysis conditions and behaviors of the plated gold layer. In order to investigate the effect of pretreatment processes on plating, rest potential measurements of various pretreated stainless steels and a.c.-impedance spectroscopy tests were carried out in the strike plating solution. Characteristics of plated gold layers and adhesions between plated gold layers and stainless steel substrates were examined by scratching tests and micro-Vickers hardness tests. The result shows that the strike plating enhanced the adhesion of interface, the cathodic electro-activation pretreatment process improving both corrosion resistance and adhesion strength. The preferred orientations of plated gold layers were examined by the X-ray diffraction technique. As the current density increases, [111] preferred orientation of plated gold layers was found to become well developed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.12
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• pp.1071-1086
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• 2016

The safety of aircraft can be threatened by environmental factors, such as icing, turbulence, and lightning strike. Due to its adverse effects on aircraft structure and electronic components of aircraft, lightning strike is one of the biggest hazards on aircraft safety. Lightning strike can inject high voltage electric current to the aircraft, which may generate strong magnetic field and extreme hot spots, leading to severe damage of structure or other equipment in aircraft. In this work, mechanism of lightning strike and associated direct and indirect effects of lightning on aircraft were studied. First, on the basis of aircraft lightning regulations provided by Aerospace Recommended Practice (ARP), we considered different lightning waveform and zones of an aircraft. A coupled thermal-electrical computational model of ABAQUS was then used for simulating flow of heat and electric current caused by a lightning strike. A study on fuel tank, with and without lightning protection system, was also conducted using the computational model. Finally, electric current flow on two full scale airframes was analyzed using the EMA3D code.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.117-124
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• 2010

The bird strike to small aircraft has not been an issue because of its low speed and usage as a private aircraft. So, the compliance of the bird strike regulation is limited to large fixed-wing aircraft such as the commuter category in FAR Part 23 and the civil aircraft in FAR Part 25, generally. However, the forecast of dramatic increasing of VLJ(Very Light Jet), the usage of a composite material for an aircraft structure and flight time of general aviation due to Air-taxi for the point to point transportation, would rise up the need of bird strike regulations and a safety enhancement in normal and utility categorized aircraft. In this study, the safety of bird strike to small aircraft wing leading edge made of a metal and a composite material were compared using the explicit finite element analysis.

• Korean Journal of Labor Studies
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• v.24 no.1
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• pp.157-196
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• 2018

This study analyzes non-standard workers' attitudes and behaviors towards standard workers' strikes using the case of a joint strike held by journalists at KBS and MBC in 2012. Tracing the process since 2008 by which a conservative government has tried to control the press and regular journalists have collectively resisted against it, we put our analytical focus on two major groups of freelance broadcast professionals: independent producers and writers in current affairs. Specifically, we examine 1) how they perceived and responded to a series of regular journalists' struggle to protect journalistic value, 2) how such perception of and response to regular journalists could be developed, and 3) how (de)solidarity could form and then deepened between freelance and regular journalists in the 2012 Media Strike. Our findings show that the ways in which regular journalists had controlled freelance journalists at work affected the relationship between class-based and occupation-based rationality freelance journalists held in their minds. Independent producers, who had developed a strong class-based rationality in response to the coercive input-output control, showed cynicism about regular journalists' strike pointing out their hypocrisy and contradiction. In contrast, freelance writers accommodated and joined the strike by regular workers in the spirit of solidarity based on occupational rationality which had developed from normative, process control. Our paper ends with theoretical and practical implications.

• The Journal of Engineering Geology
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• v.32 no.4
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• pp.467-482
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• 2022

The Yeonghae basin is located at the northeastern part of the Yangsan fault (YSF; a potentially active fault). The study of the architecture of the Yeonghae basin is important to understand the activity of the Yangsan fault system (YSFS) as well as the basin formation mechanism and the activity of the YSFS. For this study, Digital Elevation Model (DEM) was used to highlight the marginal faults, and structural fieldwork was performed to understand the geometry of the intra-basinal structures and the nature of the bounding faults. DEM analysis reveals that the eastern margin is bounded by the northern extension of the YSF whereas the western margin is bounded by two curvilinear sub-parallel faults; Baekseokri fault (BSF) and Gakri fault (GF). The field data indicate that the YSF is striking in the N-S direction, steeply dipping to the east, and experienced both sinistral and dextral strike-slip movements. Both the BSF and GF are characterized dominantly by an oblique right-lateral strike-slip movement. The stress indicators show that the maximum horizontal compressional stress was in NNE to NE and NNW-SSE, which is consistent with right-lateral and left-lateral movements of the YSFS, respectively. The plotted structural data show that the NE-SW is the predominant direction of the structural elements. This indicates that the basin and marginal faults are mainly controlled by the right-lateral strike-slip movements of the YSFS. Based on the structural architecture of the Yeonghae basin, the study area represents a contractional zone rather than an extensional zone in the present time. We proposed two models to explain the opening and developing mechanism of the Yeonghae basin. The first model is that the basin developed as an extensional pull-apart basin during the left-lateral movement of the YSF, which has been reactivated by tectonic inversion. In the second model, the basin was developed as an extensional zone at a dilational quadrant of an old tip zone of the northern segment of the YSF during the right-lateral movement stage. Later on, the basin has undergone a shortening stage due to the closing of the East Sea. The second model is supported by the major trend of the collected structural data, indicating predominant right-lateral movement. This study enables us to classify the Yeonghae basin as an inverted strike-slip basin. Moreover, two opposite strike-slip movement senses along the eastern marginal fault indicate multiple deformation stages along the Yangsan fault system developed along the eastern margin of the Korean peninsula.