• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.37 no.6
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• pp.473-479
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• 2019

This study applied SGM (Semi Global Matching) to generate DSM (Digital Surface Model) using WorldView-1 high-resolution satellite stereo pair in Terrassa, Spain provided by ISPRS (International Society for Photogrammetry and Remote Sensing). The SGM is an image matching algorithm that performs the computation of the matching cost for the stereo pair in multi-paths and aggregates the computed costs sequentially. This method finally calculates the disparity corresponding to the minimum (or maximum) value of the aggregation cost. The cost was applied to MI (Mutual Information), NCC (Normalized Cross-Correlation), and CT (Census Transform) in order to the SGM. The accuracy and performance of the outline representation result in DSM by each cost are presented. Based on the images used and the subject area, the accuracy of the CT cost results was the highest, and the outline representation was also most clearly depicted. In addition, while the SGM method represented more detailed outlines than the existing software, many errors occurred in the water area.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.6
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• pp.42-53
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• 2015

In this study, the influence of Al particle size, as an additive for solid propellant, on the mechanical erosion of the carbon-composite nozzle was evaluated. A new model which can predict the size and distribution of the agglomerated reaction product($Al(l)/Al_2O_3(l)$) was established, and the size of agglomerate were calculated according to the various initial size of Al in the solid propellant. With predicted results of the model, subsequently, the characteristics of mechanical erosion on the carbon-composite nozzle was estimated using a commercial CFD software, STAR CCM+. The result shows that the smaller the initial Al particles are, in the solid propellant, the lower is the mechanical erosion rate of the composite nozzle wall, especially for the nano-size Al particle.

• Korean Journal of Construction Engineering and Management
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• v.1 no.3 s.3
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• pp.101-107
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• 2000

On 1 July, 2000, the Ministry of Construction and Transportation announced the Earned Value Management System(EVMS) will be applied in public sector soon. However the arguments over the EVMS applied to our unique construction environment still exist and create strong concerns and worries among some experts it would be another mistakes proposed by the government. We do know the EVMS comes from C/SCSC which was first released by the United States Department of Defense in December 1967, and proved very powerful and efficient project management tool from a lot of practices. Although it is an excellent tool, we can not ignore our many experienced failures appling foreign system due to the differences of construction culture and law between the Korean and US construction industries. The purpose of the EVMS's success in Korea, therefore, this paper tests and proves the EVMS's adaptability and credibility to our construction environment by EAC model, that is one of the most important functions in the EVMS, using very scare EV data of the Korean construction projects.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.3
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• pp.185-193
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• 2013

The plume infrared signature effects at various flight conditions of aircraft were investigated for the purpose of reducing infrared signature level. The nozzle of a virtual subsonic unmanned combat aerial vehicle was designed through a performance analysis. Nozzle and associated plume flowfields were first analyzed using a density-based CFD code and plume IR signature was then calculated on the basis of the narrow-band model. Finally, qualitative information for the plume infrared signature characteristics was obtained through the analysis of the IR signature effects at various flight conditions.

• Korean Journal of Construction Engineering and Management
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• v.3 no.4 s.12
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• pp.114-122
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• 2002

Earned Value Management System(EVMS) is a management technique that is emerging as a valuable tool in the management of all projects, including and in particular construction projects. It is based on C/SCSC that has been released by the U.S. Department of Defense (DOD) in 1967. In a project that employs the earned value management concept, the project's measurable performance plans will be formed with the creation of CAPs. The formation of CAPs is a planning step necessary to form an earned value baseline. In this paper, a method is proposed to form CAPs using Material Requirement Planning(MRP) that is also known as a useful planning tool in the manufacturing industry. An application to a real project has been carried through workpackaging model.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.1
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• pp.68-76
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• 2018

Target prioritization is necessary for a multifunction radar(MFR) to track an important target and manage the resources of the radar platform efficiently. In this paper, we consider an artificial neural network(ANN) model that calculates the priority of the target. Furthermore, we propose a neural network learning algorithm based on the steepest descent method, which is more suitable for target prioritization by combining the conventional gradient descent method. Several simulation results show that the proposed scheme is much more superior to the traditional neural network model from analyzing the training data accuracy and the output priority relevance of the test scenarios.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.3
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• pp.148-156
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• 2013

Since the demand for new military vehicle to fulfill the necessary conditions such as multi-purpose, high-mobility, and survivability has raised continuously from the army, the prototype of a Korean light tactical vehicle was developed to meet these requirements using our own technology. In particular, the new tactical vehicle was equipped with a double wishbone independent suspension to improve ride and handling and maximize off-road driving performance. In this paper, a comprehensive virtual durability process to evaluate the service life of the prototype is presented. A reliability of the trimmed body model based on CATIA data was verified by comparison result between mode analysis and modal test. The dynamic model was constructed using ADAMS/Car, and then the weight distribution and lateral slope driving performance of it were compared with the results of static weight and lateral slope tests. The validity of the VTL(Virtual Test Lab) was checked with test results from the 3-inch spaced impact road. The durability performances of trimmed body and suspension components were evaluated through MSM(Modal Superposition Method) fatigue analysis. It is shown that the virtual durability process could be a helpful tool to find out the weak areas and improve their structures in developing new military vehicle.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.4
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• pp.24-36
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• 2015

In the present study, numerical predictions of infrared spectrum of rocket plume with considering effect of particles based on approximation theories were performed by using a line-by-line radiation model with radiation databases. The high-resolution radiation databases were used to predict thermal emission spectra of gas molecules within the rocket plume regime. The particles were modeled as soot particles by using 1st term approximation of Mie theory and Rayleigh approximation. The reliability of modeled effect of soot particles using the two approximation theories was verified, and the spectral radiance of rocket plume was predicted based on the verification. The results were improved in the short wavelength range by considering the effect of soot particles.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.5
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• pp.37-45
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• 2015

Prediction of combustion instability within a solid-propellant rocket motor has been conducted with the classical acoustic analysis. The effect of particle size distribution on the instability has been analyzed by comparing the log-normal distribution to the fixed mono-sized particle followed by a survey of motor length scale effect between the baseline model and small scale model. Particle damping effect was more efficient for the small scale motor which has a relatively high unstable mode frequencies. It was also revealed that the prediction results by considering the particle size distribution show an overall attenuation of fluctuating pressure amplitude with respect to the mono-sized case.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.8
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• pp.23-32
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• 2007

We propose a group-based security scheme for hierarchical wireless sensor networks. We model the network for secure routing with 3-tier sensor network comprised of three types of nodes: Base Station, Group Dominator and ordinary Sensor Nodes. Group-based deployment is performed using Gaussian (normal) distribution and show that more than 85% network connectivity can be achieved with the proposed model. The small groups with pre-shared secrets form the secure groups where group dominators form the backbone of the entire network. The scheme is devised for dealing with sensory data aggregated by groups of collocated sensors; i.e., local sensed data are collected by the dominating nodes and sent an aggregated packet to the base station via other group dominators. The scheme is shown to be light-weight, and it offers a stronger defense against node capture attacks. Analysis and simulation results are presented to defend our proposal. Analysis shows that robustness can significantly be improved by increasing the deployment density using both the dominating and/or ordinary sensor nodes.