• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.3
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• pp.309-316
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• 2021

In this paper, the electrical power output of the micro-combustor thermophotovoltiac(TPV) system was analyzed. The system consists of a micro-combustor, photonic crystals(PhCs), and photovoltaic cells(PV cells). The system has a micro-combustor that can achieve over 1,000 K surface temperature by consuming 2.5 g/h hydrogen fuel. Also, this system incorporates current state-of-the-art PhCs surfaces(2D Ta PhCs and Tandem Filter) to increase electrical power output. In addition, InGaAsSb PV cell, which bandgap is 0.55 eV, was applied to convert a wide range of radiative energy. The performance analysis shows that a single micro-combustor TPV system can produce 0.4 W ~ 27.7 W electrical power with the temperature change of emitter(900 K ~ 1,500 K) and PV cell(250 K ~ 400 K).

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.1
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• pp.32-37
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• 2021

This study proposes a DC series arc fault detector using a frequency analysis method called the discrete wavelet transform (DWT), in which the processing speed of the DWT algorithm is improved effectively. The processing time can be shortened because of the time characteristic of the DWT result. The performance of the developed DC series arc fault detector for a large photovoltaic system is verified with various DC series arc generation conditions. Successful DC series arc detection and improved calculation time were both demonstrated through the measured actual arc experimental result.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.1
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• pp.43-48
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• 2021

Most existing studies on the wide-area differential global positioning system (WADGPS) used standard positioning service (SPS) receivers in their observation reference stations which provide the central control station global positioning system (GPS) measurements to generate augmentation data. In the present study, it is considered to apply a precise positioning service (PPS) receiver to an observation reference station which is located in the threatened jamming area. Therefore, the reference station network consists of a PPS receiver based observation reference station and SPS receiver based observation reference stations. In this case, to maintain correction performance P1C1 differential code bias (DCB) should be compensated. In this paper, P1C1 DCB estimation algorithm was applied to the PPS/WADGPS system and performance test results using measurements in the Korean Peninsula were presented.

• Journal of Positioning, Navigation, and Timing
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• v.12 no.3
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• pp.307-314
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• 2023

Wide-Area Differential Global Positioning System (WADGPS) is a system that operates a number of reference stations to provide correction information to improve the accuracy of GPS users, and it is available to service users within the area where the wide-area reference stations are installed. Recently, as positioning information has been used in various applications, the need for WADGPS for precise navigation in long-distance spaced areas where the wide-area reference stations cannot be installed has been raised. This paper tested the user navigation performance outside the wide-area reference stations of the WADGPS system, which serves both GPS Precise Positioning Service (PPS) and Standard Positioning Service (SPS) users. Static and dynamic tests were conducted using vehicles, and as a result, position accuracy improvement through WADGPS was confirmed even at points hundreds of kilometers outside the network area of the wide-area reference stations. Through this, the performance of the PPS/SPS correction system and the possibility of expanding the service area were confirmed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.700-707
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• 2016

Recently, ammunition malfunctions of the 40mm grenade were reported during live fire training. When 72 40mm grenades were fired by the army, 11 duds were encountered. The dud ammunition rate was approximately 15%. Because ammunition is used a long time after its manufacture, it is necessary to ensure its performance after long-term storage. In this study, we attempted to decrease the dud ammunition rate of 40mm grenade (K200) fuzes through quality improvement. First, it was determined by the detonator performance test that abnormal explosions occurred due to the degradation of the detonator as a result of its aging characteristics. Second, we improved the fuze quality of the 40mm grenade. Third, we tested its shelf life to estimate its life expectancy. The shelf life of the 40mm grenade fuze obtained using the Arrhenius equation was 6.5 years for the existing grenade fuze and 45.5 years for the improved grenade fuze. This showed that the shelf life of the improved grenade was increased approximately 7 times. Therefore, the improved 40mm grenade fuze contributes to the quality improvement of the 40mm grenade by decreasing the dud ammunition rate during long term storage.

• Journal of Intelligence and Information Systems
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• v.15 no.1
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• pp.51-64
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• 2009

A location tracking sensor such as GPS, INS, Radar, and optical equipments is used in tracking Maneuvering Targets with a multi-sensor, and such systems are used to track, detect, and control UAV, guided missile, and spaceship. Until now, Most of the studies related to tracking Maneuvering Targets are on fusing multiple Radars, or adding a supplementary sensor to INS and GPS. However, A study is required to change the degree of application in fusions since the system property and error property are different from sensors. In this paper, we perform the error analysis of the sensor properties by adding a ground radar to GPS and INS for improving the tracking performance by multi-sensor fusion, and suggest the tracking algorithm that improves the precision and stability by changing the sensor probability of each sensor according to the error. For evaluation, we extract the altitude values in a simulation for the trajectory of UAV and apply the suggested algorithm to carry out the performance analysis. In this study, we change the weight of the evaluated values according to the degree of error between the navigation information of each sensor to improve the precision of navigation information, and made it possible to have a strong tracking which is not affected by external purposed environmental change and disturbance.

• Journal of Internet Computing and Services
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• v.21 no.1
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• pp.179-190
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• 2020

In the Unix-like system environment, the GOT overwrite attack is one of the traditional control flow hijacking techniques for exploiting software privileges. Several techniques have been proposed to defend against the GOT overwrite attack, and among them, the Full Relro(Relocation Read only) technique, which blocks GOT overwrites at runtime by arranging the GOT section as read-only in the program startup, has been known as the most effective defense technique. However, it entails loading delay, which limits its application to a program sensitive to startup performance, and it is not currently applied to the library due to problems including a chain loading delay problem caused by nested library dependency. Also, many compilers, including LLVM, do not apply the Full Relro technique by default, so runtime programs are still vulnerable to GOT attacks. In this paper, we propose a GOT protection scheme using the Control Flow Integrity(CFI) technique, which is currently recognized as the most suitable technique for defense against code reuse attacks. We implemented this scheme based on LLVM and applied it to the binutils-gdb program group to evaluate security, performance and compatibility. The GOT protection scheme with CFI is difficult to bypass, fast, and compatible with existing library programs.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.328-334
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• 2020

At the recent practice test of the Remote Controlled Munition system (for practice), nine out of 125 samples were generated. Although 7.2 % misfires occurred, the acceptance test met the defense standards. Minimizing the probability of broken fuses is essential to reducing the number of samples and improving the AQL according to the process quality. In addition, it is necessary to increase military training and ensure user safety. In the case of practical grenades, hit-type detonators are applied. Unlike the normal design, which takes a hit by strikers, a different design of a hit by pressure from a pressure generator was used. This study analyzed the detonator surface through computational fluid dynamics. The results showed that the probability of functional weakness and retraction increased with increasing slope of the detonator surface. To overcome this, design changes were made to improve the fuse crimping process and increase the detonator holder seat. A performance test with the same number of samples from the whole quantity was operated. The probability of broken fuses was 0 %. Therefore, the reliability and performance of the ammunition can be improved and is expected to contribute to the drawing and process design when developing similar ammunition.

• Composites Research
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• v.29 no.1
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• pp.24-32
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• 2016

Ballistic impact analyses have been performed with the Kevlar fabric impregnated with STF(shear thickening fluid). Multi-layer laminates modeled with 3D isoparametric shell elements were used for the performance analysis and their results are compared with experimental results. Both experiments and numerical analyses have been done to verify the usefulness of STF to enhance the impact resistance performance. The results showed that STF increases friction within a bundle of fiber, and this phenomena is more apparent in the velocity range of under near 450 m/s. In this research, it is emphasized that FEA analyses of STF impregnated Kevlar fabric laminate were successfully conducted using shell elements. Moreover, the effectiveness of the technique and accuracy were verified through the comparison with reliable experimental data.