• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.4
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• pp.371-380
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• 2020

Video is principal information that facilitates commander's immediate command decision. Due to fading characteristics of radio link, however, it is difficult to stably transmit video in a multi-hop wireless environment. In this paper, we propose a MANET structure composed of a link adaptive routing protocol and a TDMA MAC protocol to stably transmit video traffic in a ultra-narrowband video streaming network. The routing protocol can adapt to link state change and select a stable route. The TDMA protocol enables collision-free video transmission to a destination using multi-hop dynamic resource allocation. As a result of simulation, the proposed MANET structure shows better video transmission performance than proposed MANET structure without link quality adaption, AODV with CSMA/CA, and OLSR with CSMA/CA structures.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.9
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• pp.1069-1080
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• 2016

TDOA(Time Difference Of Arrival)-based localization system such as the passive surveillance system performs the time synchronization between the receivers after separated installing multiple receivers to set the same clock for all receivers. And it estimates 2D(or 3D) location of the target by solving intersection of the multiple hyperbola(or hyperboloid) using TDOA. To perform time synchronization, one receiver must be set to the master, and it provide the reference data to compensate the clock of the rest of the slaves. The positioning accuracy of TDOA-based localization system is changed in accordance with the master that is selected among multiple receivers. So, the optimum receiver which is selected among multiple receivers must be set to master to get best performance in the considered deployment of receivers. In this paper, we propose a selection scheme of master receiver for time synchronization using DOP(Dilution Of Precision) which is based on location of the target and the multiple receivers. The proposed scheme has low complexity and short processing time, and it is easy to automate in the TDOA-based localization systems.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.6
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• pp.1317-1330
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• 2017

To collect server information and construct network map enable us to prevent security breach, prepare for national cyber warfare and make effective policies. In this paper, we analyze well-known network scanners, Nmap and ZMap, and construct network map using banner grabbing. We use multiple threads in order to increase scanning speed and arrange IP lists by specific order to reduce the load on information gathering targets. Also, we applied performance tests to compare the real-time banner grabbing tool with the existing network scanners. As a result, we gathered server information from domestic and overseas servers and derived a risk index based on the collected database. Although there are slight differences among countries, we can identify the risky situation that many users in every country are exposed to several security breaches.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.5
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• pp.599-606
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• 2019

The Arena Fragmentation Test(AFT) is one of the important tasks for designing a high-explosive warhead. In order to measure the statistics of a warhead in the test, fragments of a warhead that penetrate steel plates are detected by using complex and expensive measuring equipment. In this paper, instead of using specific hardware to measure the statistics of a warhead, we propose to use an image processing based object detection algorithm to detect fragments in AFT. To this end, we use a hard-thresholding method with a brightness feature and apply a morphology filter to remove noise components. We also propose a simple yet effective temporal filtering method to detect only the first penetrating fragments. We show that the performance of the proposed method is comparable to that of a hardware system under the same experimental conditions. Furthermore, the proposed method can produce better results in terms of finding exact positions of fragments.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.3
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• pp.54-64
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• 2015

This paper deals with an acceleration controller design for a kill vehicle equipped with a divert and attitude control system (DACS). In the proposed method, the attitude control system (ACS) is used to produce the thrust command to nullify angle-of-attack. For the angle-of-attack control, a nonlinear angle-of-attack controller is proposed based on the feedback linearization methodology. Since the flight path angle is identical to the attitude angle under the condition of zero angle-of-attack, the divert control system (DCS) can directly produce the lateral acceleration which is demanded from the guidance loop. In the proposed method, we can minimize the aerodynamic uncertainty due to the propulsive force. Additionally, we can simplify the operation logic of DCS and ACS. In this paper, nonlinear simulations are performed to show the performance of the proposed method.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.5
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• pp.43-53
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• 2014

Shock tunnels are known to be capable of simulating flow-field environments of supersonic and hypersonic flights. They have been operated successfully world-wide for almost half a century. As a consequence of the strong interest in hypersonic vehicles in Korea, attention has been given on this type of facility and so an intermediate-sized shock tunnel has lately been built at KAIST. In the light of this, this paper presents our tunnel performance and some of the model scramjet test data. The freestream flow used in this work replicates a supersonic combustor environment for a Mach 5.7 flight speed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.321-328
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• 2019

A military shelter for communication and information is necessary to optimize the integrated combat ability of weapon systems in the network centric warfare. Therefore, the military shelter is required for EMI shielding performance. This study examines the stable measurement points for EMI shielding effectiveness of a military shelter for communication and information. The measurement points were found by analyzing the EMI shielding effectiveness measurement data with data mining technique and process capability analysis. First, a support vector machine was used to separate the measurement point that has stable EMI shielding effectiveness according to set condition. Second, this process was conducted with process capability analysis. Finally, the results of data mining technique were compared with those of process capability analysis. As a result, 24 measurement points with stable EMI shielding effectiveness were found.

• Korean Journal of Optics and Photonics
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• v.30 no.1
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• pp.1-7
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• 2019

MANPADS (man-portable air defense system) is a counterweapon system against enemy aircraft, tracking the MWIR (mid-wavelength of infrared) signature of the plume. Under foggy conditions, however, multiple scattering phenomenon caused by the particles affects the MWIR transmittance, and the MANPADS detection performance. Therefore, in this study we analyzed the lock-on range of MANPADS with varying fog conditions and plume characteristics. To analyze the optical extinction properties and transmittance in fog, Mie scattering theory and analytic solution of the radiative-transfer equation are utilized. In addition, we used flare signature as an alternative MWIR light source. We confirmed that the lock-on range could be noticeably reduced under conditions of mist, and proportional to the flare temperature.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.5
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• pp.383-388
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• 2021

Air-breathing engines used in aircraft have a performance limit as the altitude increases, and this determines the service and absolute ceiling altitude. The method of maintaining altitude and speed in a fixed-wing aircraft in level flight using classical control method is generally using thrust for speed increase/deceleration and pitch attitude for altitude increase/decrease. If this method is used near the service ceiling altitude, increasing the pitch to reduce the altitude error results in a speed reduction. Therefore, it is necessary to use a control method that maintains the speed first using the pitch attitude. Especially in the case of unmanned aerial vehicles, these two methods should be automatically available at the right time. In this paper, we propose a method of switching the speed and altitude maintenance algorithm near service ceiling altitude.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.234-241
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• 2021

By recognizing the importance of demand forecasting, the military is conducting many studies to improve the prediction accuracy for repair parts. Demand forecasting for repair parts is becoming a very important factor in budgeting and equipment availability. On the other hand, the demand for intermittent repair parts that have not constant sizes and intervals with the time series model currently used in the military is difficult to predict. This paper proposes a method to improve the prediction accuracy for intermittent repair parts of the Patriot. The authors collected intermittent repair parts data by classifying the demand types of 701 repair parts from 2013 to 2019. The temperature and operating time identified as external factors that can affect the failure were selected as input variables. The prediction accuracy was measured using both time series models and data mining models. As a result, the prediction accuracy of the data mining models was higher than that of the time series models, and the multilayer perceptron model showed the best performance.