• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.4
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• pp.297-305
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• 2018

The role of UCAV is to carry out various missions in hostile situations such as penetration and attack on the enemy territory. To this end, application of RF stealth technology is indispensable so as not to be caught by enemy radar. The X-47B UCAV with blended wing body configuration is a representative aircraft in which modern RCS reduction schemes are heavily applied. In this study, a model UCAV was first designed based on the X-47B platform and then an extensive RCS analysis was conducted to the model UCAV in the high-frequency regime using the Ray Launching Geometrical Optics (RL-GO) method. In particular, the effects of configuration of UCAV considering IR reduction on RCS were investigated. Finally, the effects of RAM optimized for the air intake of the model UCAV were analyzed.

• Journal of the Korean Geosynthetics Society
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• v.5 no.1
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• pp.25-32
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• 2006

Sea dyke construction is simply defined as a cutting procedure of sea water flow. Sea dyke construction is more difficult than in-land construction because it is placed on deep seabed and exposed sea wave attack. Especially, the final closure of sea dyke is most dangerous due to the fast velocity of tidal flow. The final closure is consisted with vast rubble and heavy stone gabion, therefore the discharge velocity at land side of final close section is irregularly and sometime occur the fast discharge velocity. In this paper, the seepage model test performed to evaluate seepage behavior of final closure and continuous sea dyke section such as discharge velocity, hydraulic gradient, and phreatic line with installation of bottom protection filter mat. Based on the seepage model test results, the maximum discharge velocity of final closure section is 1.7m/sec and the discharge velocity is decreased maximum 23.7% with installation of bottom protection filter mat.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.4
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• pp.38-43
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• 2002

A study on the test, design and fabrication of wind tunnel model for measurement of air load distribution on wing surfaces is presented. 447 pressure taps are installed normal to the wing surfaces, and measured by PSI-8400 system using total 8 ESPs modules installed in the model. The test was performed at 50 m/sec constant speed in the low speed wind tunnel of Agency for Defense Development. Tests were carried out to determine effects of angle of attack, angle of sideslip and flap and stores for the load distribution of wing. The test results in this paper can be applied to the design optimization of structure and validation of computational fluid dynamics.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.5
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• pp.1197-1207
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• 2018

PowerShell is command line shell and scripting language, built on the .NET framework, and it has several advantages as an attack tool, including built-in support for Windows, easy code concealment and persistence, and various pen-test frameworks. Accordingly, malwares using PowerShell are increasing rapidly, however, there is a limit to cope with the conventional malware detection technique. In this paper, we propose an improved monitoring method to observe commands executed in the PowerShell and a deep learning based malware classification model that extract features from commands using Convolutional Neural Network(CNN) and send them to Recurrent Neural Network(RNN) according to the order of execution. As a result of testing the proposed model with 5-fold cross validation using 1,916 PowerShell-based malwares collected at malware sharing site and 38,148 benign scripts disclosed by an obfuscation detection study, it shows that the model effectively detects malwares with about 97% True Positive Rate(TPR) and 1% False Positive Rate(FPR).

• The Journal of the Korea Contents Association
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• v.17 no.3
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• pp.231-237
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• 2017

Threat intelligences collected from cyber incident sharing system and security events collected from Security Information & Event Management system are analyzed and coped with expanding malicious code rapidly with the advent of big data. Analytical classification of the threat intelligence in cyber incidents requires various features of cyber observable. Therefore it is necessary to improve classification accuracy of the similarity by using multi-profile which is classified as the same features of cyber observables. We propose a multi-profile ensemble model performed similarity analysis on cyber incident of threat intelligence based on both attack types and cyber observables that can enhance the accuracy of the classification. We see a potential improvement of the cyber incident analysis system, which enhance the accuracy of the classification. Implementation of our suggested technique in a computer network offers the ability to classify and detect similar cyber incident of those not detected by other mechanisms.

• Structural Engineering and Mechanics
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• v.75 no.4
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• pp.487-496
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• 2020

Most of the previous works on numerical analysis of galloping of transmission lines are generally based on the quasisteady theory. However, some wind tunnel tests of the rectangular section or hangers of suspension bridges have shown that the galloping phenomenon has a strong unsteady characteristic and the test results are quite different from the quasi-steady calculation results. Therefore, it is necessary to check the applicability of the quasi-static theory in galloping analysis of the ice-covered transmission line. Although some limited unsteady simulation researches have been conducted on the variation of parameters such as aerodynamic damping, aerodynamic coefficients with wind speed or wind attack angle, there is a need to investigate the numerical simulation of unsteady galloping of two-dimensional iced transmission line with comparison to wind tunnel test results. In this paper, it is proposed to conduct a two dimensional (2-D) unsteady numerical analysis of ice-covered transmission line galloping. First, wind tunnel tests of a typical crescent-shapes iced conductor are conducted firstly to check the subsequent quasisteady and unsteady numerical analysis results. Then, a numerical simulation model consistent with the aeroelastic model in the wind tunnel test is established. The weak coupling methodology is used to consider the fluid-structure interaction in investigating a two-dimension numerical simulation of unsteady galloping of the iced conductor. First, the flow field is simulated to obtain the pressure and velocity distribution of the flow field. The fluid action on the iced conduct at the coupling interface is treated as an external load to the conductor. Then, the movement of the conduct is analyzed separately. The software ANSYS FLUENT is employed and redeveloped to numerically analyze the model responses based on fluid-structure interaction theory. The numerical simulation results of unsteady galloping of the iced conduct are compared with the measured responses of wind tunnel tests and the numerical results by the conventional quasi-steady theory, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.2
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• pp.114-118
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• 1987

The authors carried out a model experiment to examine the hydrodynamic charactristics of the simple camber and the super-V otter board. The model otter boards are made of 1 mm thick iron plate. The simple camber otter board is made to have $12\%$ camber ratio and $432\;cm^2$ plane projected area, and the super-V otter board to have the same camber ratio as the former in every latitudinal section and almost the same plane projected area. The experiment had been done in a circular flow tank in the speed range of $0.1\~1.2m/sec$. As a result, it is examined that in the simple camber otter board the most effective angle of attack is about $25^{\circ}$, the shearing coefficient 1.47 and the drag coefficient 0.42, while in the super-V otter board they are about $20^{\circ}$, 1.40 and 0.40 respectively, so that the simple camber otter board performs a little better efficiency than the super-V otter board.

• Journal of KIISE:Computing Practices and Letters
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• v.12 no.6
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• pp.339-348
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• 2006

Recently, many researches on detecting and responding worms due to the fatal infrastructural damages explosively damaged by automated attack tools, particularly worms. Network service vulnerability exploiting worms have high propagation velocity, exhaust network bandwidth and even disrupt the Internet. Previous worm researches focused on signature-based approaches however these days, approaches based on behavioral features of worms are more highlighted because of their low false positive rate and the attainability of early detection. In this paper, we propose a Distributed Worm Detection Model based on packet marking. The proposed model detects Worm Cycle and Infection Chain among which the behavior features of worms. Moreover, it supports high scalability and feasibility because of its distributed reacting mechanism and low processing overhead. We virtually implement worm propagation environment and evaluate the effectiveness of detecting and responding worm propagation.

• Journal of Aerospace System Engineering
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• v.12 no.4
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• pp.57-63
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• 2018

IR thermography is a non-invasive method and used for the visualization of the surface temperature of the model. However, this technique only derives 2D results and not quantitative data. The goal of this study is to apply the 3D mapping technique for IR thermography. The wind tunnel model is an ogive-cylinder with a wind speed of 20 m/s ~ 80 m/s and the angle of attack ranging from $0^{\circ}$ to $90^{\circ}$. The real location of the model was made to correspond with the position of the IR image using the makers. Based on this result, quantitative results were obtained. The 3D mapping method was verified by comparing the separation point and the theoretical value.

• Convergence Security Journal
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• v.17 no.4
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• pp.11-16
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• 2017

MANET composed of only mobile node is applied to various environments because of its advantage which can construct network quickly in emergency situation. However, many routing vulnerabilities are exposed due to the dynamic topology and link failures by the movement of nodes. It can significantly degrade network performance. In this paper, we propose a secure routing protocol based on trust model. The domain-based network structure is used for efficient trust evaluation and management of nodes in the proposed technique. The reliability evaluation of nodes was performed by the discard ratio of control packet and data packet of the nodes. The abnormal nodes are detected by performing traffic check and inspecting of nodes on a path that generates excessive traffic in order to increase the efficiency of routing. It is confirmed through experiments of the proposed technique that data transmission is performed securely even if an attack exists on the path.