• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.3
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• pp.258-265
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• 2017

This paper validates a system identification method using mathematical optimization using sea trial measurement data as a benchmark. A fast time simulation tool, SIMOPT, and a Rheinmetall Defence mathematical model have been adopted to conduct initial hydrodynamic coefficient estimation and simulate ship modelling. Calibration for the environmental effect of sea trial measurement and sensitivity analysis have been carried out to enable a simple and efficient optimization process. The optimization process consists of three steps, and each step controls different coefficients according to the corresponding manoeuvre. Optimization result of Step 1, an optimization for coefficient on x-axis, was similar compared to values applying an empirical regression formulae by Clarke and Norrbin, which is used for SIMOPT. Results of Steps 2 and 3, which are for linear coefficients and nonlinear coefficients, respectively, was differ from the calculation results of the method by Clarke and Norrbin. A comparison for ship trajectory of simulation results from the benchmark and optimization results indicated that the suggested stepwise optimization method enables a coefficient tuning in a mathematical way.

• Earthquakes and Structures
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• v.19 no.2
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• pp.145-156
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• 2020

The 24 January 2020 (Mw=6.8) earthquake with epicentre in Elazığ (Sivrice) on the East Anatolian Fault Zone caused loss of life and property. The information was given about the seismotectonic setting and regional seismicity along this fault zone and aftershock activity and ground motion data of this earthquake. Earthquake parameters were obtained for five different earthquake stations which were closer to the epicentre. Horizontal and vertical design spectra were obtained for the geographic locations for each earthquake station. The obtained spectra for the earthquake epicentre were compared with selected appropriate attenuation relationships. The damages after earthquake were evaluated via geotechnical and structural aspects. This study also aims to investigate the cause-effect relationships between structural damage in reinforced-concrete and masonry structures, respectively. The lack of engineering services was effective on the amount of damage in masonry structures. Insufficient reinforcement and concrete strength, dimensions and inadequate detailing increased the amount of damage in reinforced-concrete structures. Importance should be given to negative parameters that may weaken the defence mechanisms of structures for earthquake-resistant structural design.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.4
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• pp.307-312
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• 2010

Purpose: In this paper, we have dealt with problems of army supply system for eyeglasses and improvement plan. Methods: We collected the latest service request of MND (Ministry of National Defence) and case of U.S. Army and analyzed the data. Results: We treated contents, construction methods and plans for efficient use of vision DB (database) for Korean Army. We suggested several alternative proposal for eyeglasses supply system which made possible quicker delivery of eyeglasses to the soldiers and increase satisfaction. Conclusions: The Korean Army must construct vision DB to service high quality vision service to the solider. It is urgent that the Korean Army set up a unit to take charge of vision management and service. And the Korean Army need to upgrade supply system for eyeglasses.

• Annual Conference of KIPS
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• 2002.11c
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• pp.1725-1728
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• 2002

국방부는 90년대 후반부터 국방정보체계 구축사업을 본격적으로 추진하면서 정보체계의 상호운용성 문제를 심각하게 인식하고 상호운용성을 보장하는 국방 정보체계를 구축하기 위하여 많은 노력을 추진하고 있다. 상호운용성을 보장하는 정보체계를 구축하기 위한 목표를 국방통합정보체계 구축으로 설정하고 이를 구성하는 요소로 국방정보체계표준, 공통운용환경, 데이터공유환경을 식별하고, 이를 구축하기 위해 추진하고 있다. 이들 가운데 국방정보체계표준은 선정되어, 국방전반에 대하여 효력을 발휘하고 있으며, 공통운용환경은 우리의 국방환경에 적합한 추진방향을 선정하였으나, 데이터공유환경을 구축하기 위한 전략 및 방법에 대한 연구는 부족한 실정이다. 본 연구에서는 선진국의 추진사례와 우리나라 국방 현실에 대한 분석을 통하여 우리의 현실에 맞는 데이터공유환경(SHADE)를 구축하기 위한 전략 및 방법을 제시하며, 그 내용으로는 먼저 현 국방 데이터 관리 실태 분석을 통하여 현 상황을 인식한 후, 구축하고자 하는 목표을 설정하고, 이러한 목표를 달성하기 위한 추진 전략 및 방향, 업무와 관련된 조직 및 인원에 대한 임무, 단계별 추진 과제 등을 식별하고 데이터공유가 요구되는 조직 및 체계에 적용가능한 데이터 관리 절차와 데이터 상호운용성을 만족시키기 위한 접근방법을 제시한다.

• Tunnel and Underground Space
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• v.22 no.1
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• pp.54-59
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• 2012

Deformation of Lead plate blast pressure meter were measured after they were exposed to surface blasting. Blasting pressure was determined by comparing the data with calibration graph which was drawn from the laboratory experiments with gas gun of Hopkinson bar tester. The results were compared with calculated values from the equations of CONWEP (Conventional Weapons Effects Program) and DDESB (Department of Defence Explosives Safety Board). Measured values were lower than calculated values in near field. Gradual decaying tendency of the pressure was observed. It means that estimated blasting pressure of very near field with theoretical equations can be uncertain.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.4
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• pp.359-364
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• 2012

Real-Time Traversability should be analyzed from the equiped sensors' data in real time for autonomous outdoor navigation. However, it is difficult to find out such traversability that considers the terrain roughness and the vehicle dynamics especially in case of skid type vehicle. The traversability based on real time dynamic analysis was proposed to solve such problem but in navigation with strait driving path. To adapt the method into the navigation with curved driving path, a path following controller should be incorporated into the dynamic model even though it cause the real time problem. In this paper, a dynamic model is proposed to solve the real time problem in the traversability analysis based on real time dynamic simualtion. The dynamic model contains the control dummy which is connected to the vehicle body with a universal joint to follow the curved path without controller. Simulation and experimental results on $6{\times}6$ articulated unmanned ground vehicle demonstrate the method's effectiveness and applicability into the traversability analysis on terrain with bumps.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.39-44
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• 2005

The effects of aging of PSF/AS4 laminates on fatigue was studied using the new energy release rate analysis. The analysis by the variational mechanics has been useful in providing fracture mechanics interpretation of matrix microcracking in cross-ply laminates. This paper describes the changes of the critical energy release rate (microcracking toughness) according to the aging period under fatigue loading. The master plot by modified Paris-law gives a characterization of a material system's resistance to microcrack formation. PSF $[0/90_{s}]_{s}$ laminates were aged at four different temperature based on the glass transition temperature for 0 to 60 days. At all temperatures, the toughness decreased with aging time. The decrease of the toughness at higher temperature was faster than at lower temperature. To assess the effects of aging on fatigue, the unaged laminates were compared with the laminates which had been aged for 60 days at 170$^{\circ}C$ near 180 $^{\circ}C$ t$_g$. The slope of dD/dN versus ${\Delta}G_m$. of the aged laminates was lower than that of the unaged laminates. There was a significant shift of the aged data to formation of microcracks at the lower values of ${\Delta}G_m$.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.35 no.2
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• pp.163-172
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• 2012

In this study, It is assumed that customers are both usage unit of spare parts and stores of displaying and selling the goods that are installation unit of having the spare parts. The demand pattern through the effective order of spare parts and issue list in installation unit is investigated based on the assumption. Current ASL (Authorized Stockage List) selection of the army has been conducted in the way of using the analysis result of real usage experiences on spare parts used during the Korea War. For this study, ASL selection criteria and procedures based on army regulations and field manuals are specified. Since the traditional method does not presents the association analysis on spare parts used for the current equipment operating and does not have the clear criterion and analysis system about the ASL selection, in order to solve these problems, it was carried out that the association rule is employed for analyzing relationship between the effective order and issue list of the spare parts in point of the spare parts between usage unit and occurring month about purchase spare parts based on the star-schema table. Finally the new ASL selection way using the analysis result is proposed.

• The Journal of the Acoustical Society of Korea
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• v.37 no.1
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• pp.66-72
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• 2018

In this paper, we propose an adaptive beamforming algorithm of triplet arrays for active sonar systems. The proposed algorithm consists of three steps: matched filters, cardioid beamforming, and line array beamforming. First, we apply a matched filter of a transmitted pulse to received individual sensor signals and obtain filterd signals. Then, we perform the fast Fourier transform to the matched filter results, and make a cardioid beam for each triplet data, respectively. Finally, we apply an adaptive beamforming by assuming that the cardioid beams are input signals of a line array. Experimental results demonstrate that the proposed algorithm provides better performances than conventional algorithms.

• Korean Journal of Computational Design and Engineering
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• v.20 no.4
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• pp.367-374
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• 2015

Sandwich panels consisting of various materials have widely been applied for mitigating dynamic impacts such as ballistic and blast impacts. Especially, the selection of materials for different core set-ups can directly influence its performance. In this study, we design the sandwich panels for alleviating ballistic and blast impacts by controlling the stacking sequence of core materials and their thicknesses. FEM studies are performed to simulate the dynamic behavior of sandwich panels subjected to ballistic and blast impacts. Delamination between the core layers is also considered in the FEM studies for feasible design. Based on the FEM data, kriging models are generated for approximating design space and quickly predicting the FEM outputs. Finally, design optimizations are implemented to find the optimum stacking sequence of core materials and thicknesses with given impact situations.