• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.364-370
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• 2008

Spinning detonations propagating in a circular tube were numerically investigated with a one-step irreversible reaction model governed by Arrhenius kinetics. The time evolution of the simulation results was utilized to reveal the propagation mechanism of single-headed spinning detonation. The track angle of soot record on the tube wall was numerically reproduced with various levels of activation energy, and the simulated unique angle was the same as that of the previous reports. The maximum pressure histories of the shock front on the tube wall showed stable and unstable pitch modes for the lower and higher activation energies, respectively. The shock front shapes and the pressure profiles on the tube wall clarified the mechanisms of two modes. The maximum pressure history in the stable pitch remained nearly constant, and the single Mach leg existing on the shock front rotated at a constant speed. The high and low frequency pressure oscillations appeared in the unstable pitch due to the generation and decay of complex Mach interaction on the shock front shape. The high frequency oscillation was self-induced because the intensity of the transverse wave was changed during propagation in one cycle. The high frequency behavior was not always the same for each cycle, and therefore the low frequency oscillation was also induced in the pressure history.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.39 no.5
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• pp.329-341
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• 2021

This study derives the risk-Influence factors for subway structures, the basis for the transition from the current subway disaster recovery-oriented maintenance system to a preemptive disaster management system, to reduce risk factors for existing subway structures. To apply reasonable risk assessment techniques, risk influence factors for subway underground structures using statistical information(spatial information) and risk influence factors according to frequency of accidents were selected to derive the risk factors. The significant risk factors were verified through ground subsidence (SI: Subsidence Impact)-based correlation analysis. This process confirmed that the subsidence of the ground was a risk influence factor for the subway structure. The main result of this study is that derive the risk factors to improve the risk factors of subway structures due to the rapid increase in disaster risk factors. The derived risk factors that were expected to affect the depression around subway stations and track structures did not show a noticeable correlation, but the cause of this may be that there is no physical connection between them, but on the other hand, the accumulated data may not accurately record the surrounding depression. Accordingly, in order to evaluate the risk of depression around the station and track, more intensive observation and data accumulation around the structure are required.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.06a
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• pp.373-374
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• 2022

The sea-communication fishing equipment installed on small vessels such as offshore fishing vessels is highly dependent on foreign products due to its high dependence on foreign products. From the perspective of domestication, the development of localization at the overseas level is underway, and we intend to demonstrate it by creating a dedicated testbed in order to secure track records. In this paper, we wanted to derive the testbed shape and design method through basic research for the design of the testbed.

• Journal of the Korea Society of Computer and Information
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• v.23 no.12
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• pp.49-55
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• 2018

In this paper, we propose schemes of blockchain utilization in tactical communication environment. The military tactical communication environment has similar characteristics with blockchain network such as distributed architecture, decentralization, and the need for data integrity. A communication node constituting a tactical communication network is constituted by a system capable of configuring and connecting a network for each node. When a communication node, having such capabilities, is configured as a node of blockchain network, various functions could be performed. In this paper, we propose utilization schemes of authentication, integrity, record management, and privilege control based blockchain technology. Functions for authentication, integrity verification, and record management need to ensure the stored data and could track history. The requirement of function's characteristics are matched to blockchain which is storing data sequentially and difficult to hack data, so that it could perform functionally and sufficiently well. Functions for authority control should be able to assign different privileges according to the state of the requestor. Smart contract will function when certain conditions are satisfied and it will be able to perform its functions by using it. In this paper, we will look over functions and utilization schemes of blockchain technology which could reliably share and synchronize data in a tactical communication environment composed of distributed network environment.

• Smart Structures and Systems
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• v.31 no.6
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• pp.561-571
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• 2023

Ensuring the safety of a structure necessitates that repairs are carried out based on accurate inspections and records of damage information. Traditional methods of recording damage rely on individual paper-based documents, making it challenging for inspectors to accurately record damage locations and track chronological changes. Recent research has suggested the adoption of building information modeling (BIM) to record detailed damage information; however, localizing damages on a BIM model can be time-consuming. To overcome this limitation, this study proposes a method to automatically localize damages on a BIM model in real-time, utilizing consecutive images and measurements from an inertial measurement unit in close proximity to damages. The proposed method employs a visual-inertial odometry algorithm to estimate the camera pose, detect damages, and compute the damage location in the coordinate of a prebuilt BIM model. The feasibility and effectiveness of the proposed method were validated through an experiment conducted on a campus building. Results revealed that the proposed method successfully localized damages on the BIM model in real-time, with a root mean square error of 6.6 cm.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.10 no.1
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• pp.23-31
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• 2015

The purpose of this study is to find the factors of the box office record in Korean popular music. For this purpose, 1.239 musics were selected in the Gaon digital weekly album chart from second week July 2013 to first week July 2014. The result can be summarized as follows: First, entertainment of music company, distribution of music company, singer, OST(Original Sound Track), television show, SNS and high ranking in the first week of its release are the factors of the box office record in Korean popular music. Second, entertainment of a large number of music production company is more effective than the others, but there is no difference in the case of distribution music company. Third, musics of singers who have large number of music ranked Gaon digital chart and appearance of television show program are effective in the box office record in Korean popular music. Fourth, SNS are great factors to promote Korean popular music. Fifth, it is important to rank high position in the first week of its release.

• Journal of the military operations research society of Korea
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• v.6 no.2
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• pp.129-149
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• 1980

In medical follow-up, equipment lifetesting, various military situations, and other fields, one often desires to calculate survival probability as a function of time, p(t). If the observer is able to record the time of occurrence of the event of interest (called a 'death'), then an empirical, non-parametric estimate may simply by obtained from the fraction of survivors after various elapsed times. The estimation is more complicated when the data are truncated, i.e., when the observer loses track of some individuals before death occurs. The product-limit method of Kaplan and Meier is one way of estimating p(t) when the mechanism causing truncation is independent of the mechanism causing death. This paper proposes jackknife estimators of logistic trans-formation and compares it to the product-limit method. A computer simulation is used to generate the times of death and truncation from a variety of assumed distributions.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.435-442
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• 2000

In this thesis the dynamic behavior of the vehicles is analyzed while the track is subjected to lateral vibration due to earthquakes. A computer program is developed which can simulate dynamic responses of vehicles subjected to earthquake loading. The analysis considers two types of two types of vehicles : I. e. a 2-axle vehicle with 13 DOF's an da power car of K-TGV with 38 DOF's It can also consider the interaction with substructures such as tracks and bridges. El Centro record is considered as earthquake loading. The creep force module developed in this study is verified and the results of this study are compared with those of others. Furthermore he running safety of high-speed railway vehicles(K-TGV) subjected to earthquake loading is studied. Based on the results of this study the running safety of the K-TGV can be confirmed against el centro earthquake.

• Proceedings of the KSRS Conference
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• v.1
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• pp.39-42
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• 2006

The paper reports on the first experimental evidence for space-observed manifestation of the open ocean tsunami in the microwave radar backscatter (in C- and Ku-bands). Significant variations of the radar cross section synchronous with the sea level anomaly were found in the geophysical data record of the altimetry satellite Jason-1 for the track which crossed the head wave of the catastrophic tsunami of 26 December 2004. The simultaneous analysis of the available complementary data provided by the satellite three-channel radiometer enabled us to exclude meteorological factors as possible causes of the observed signal modulation. A possible physical mechanism of modulation of short wind waves due to transformation of the thin boundary layer in the air by a tsunami wave is discussed. The results open new possibilities of monitoring tsunamis from space..

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.3
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• pp.312-321
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• 2013

In this study, we review the status of Southwest sea 2.5GW offshore wind project and expected various problems. And we suggest government policies for offshore wind industrialization. Especially, we would like to mention the necessity of offshore wind development in order to diversify power sources and guarantee energy security in Korea. And we would like to mention necessity and direction to make offshore wind into growth engine industry thorough fusion between industries and energization for the existing industry such as civil, shipbuilding, steel, etc. that was headed into downturn.