• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.5
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• pp.71-77
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• 2015

Internal ballistics is a phenomenon happened in tens of milliseconds during the gun firing. The configuration variables of the solid propellant are important factors which have influences on the performance of the gun system. In this study, the performance analysis of the 7-perforated propellant has been conducted using the numerical program for the interior ballistics. The effect of the configuration variables on the gun system performance has been analyzed. The propellant design has been conducted for the satisfaction of the performance requirements. As results, the relationship between the configuration variables and the performance has been obtained and the basic design concept of the multi-perforated propellant has been provided.

• Composites Research
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• v.31 no.5
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• pp.238-245
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• 2018

The hydrodynamic ram (HRAM) phenomenon is one of the main types of ballistic battle damages of a military aircraft and has great importance to airframe survivability design. The HRAM effect occurs due to the interaction between the fluid and structure, and damage can be investigated by measuring the pressure of the fluid and the dynamic strains on the structure. In this paper, HRAM test of a composite T-Joint was performed using a ram simulator which can generate HRAM pressure. In addition, calibration tests of PVDF sensor were performed to determine the circuit capacitance and time constant of the measurement system. The failure behavior of the composite T-Joint due to HRAM pressure was examined using the strain gauges and a PVDF sensor which were attached to the surface of the composite T-Joint.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.12
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• pp.89-100
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• 1997

This paper investigated a new type of low voltage threshold switch (LVTS). As distinguished from the many other types of electronic threshold switches, the LvTS is ; voltage controlled, occurs at low voltages ($V_{2}$ $O_{5}$lV devices. The average low threshold voltage < $V_{LVT}$>=218 mV (standard deviation =24mV~kT/q, where T=300K), and was independent of the device area (x100) and amorphous oxide occurred in an ~22.angs. thick interphase of the V/amorphous- $V_{2}$ $O_{5}$ contacts. At $V_{LVT}$ there was a transition from an initially low conductance (OFF) state into a succession of quantized states of higher conductance (ON). The OFF state was spatically homogeneous and dominated by tunneling into the interphase. The ON state conductances were consistent with the quantized conductances of ballistic transport through a one dimensional, quantum point contact. The temeprature dependence of $V_{LVT}$, and fit of the material parameters (dielectric function, barrier energy, conductivity) to the data, showed that transport in the OFF and ON states occurred in an interphase with the characteristics of, respectively, semiconducting and metallic V $O_{2}$. The experimental results suggest that the LVTS is likely to be observed in interphases produced by a critical event associated with an inelastic transfer of energy.rgy.y.rgy.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.1
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• pp.47-55
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• 2012

This paper describes the developed HILS and test equipment in order to test the performances of MMW(Millimeter-Wave) seeker which can detect and track a high speed of short-range ballistic missile and aircraft. This system is used to 141 horn antenna array, array switching, and gain and phase control algorithm to simulate various kind of targets and trajectory of high speed and maneuver moving target. In addition, it simulates not only velocity and range for these targets but also clutter and jamming environments. System configuration and implementation and the measurement results of major subsystems such as target motion simulator, simulation signal generator, high speed data aquisition unit, and central control unit are presented. These systems could verify the detection and tracking performance of MMW seeker through dynamic real-time test based on simulation flight scenario.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.561-566
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• 2001

A long bar impact test to alumina plates(AD 85 and AD 90) was carried out by using fabricated impact testing apparatus. The apparatus adopting a long bar of 2.1m in length made it possible to measure directly the applied impact force to the specimen during bar impact. The dimension of specimens was $33{\times}33mm$ and thickness was 3.4mm. Confinement of D2=18mm outer diameter and D1=10.5mm inner diameter was used to provide contact pressure to the specimen. Contact pressure of p=100 or 200MPa was applied to specimen before impact test. Damage caused in those cases were compared with the case of without contact pressure. The damage of specimen was different depending upon the pressure level of confinement. The existence of confinement had suppressed the development of radial cracks from the bottom of specimen and reduced the extent of damage as compared with cases without contact pressure(p=0MPa). Because the application of contact pressure to the specimen increased the apparent flexural stiffness of specimen during bar impact, it had produced the change of developed damage in the specimen; from the radial cracks to the local contact stress dominant damage. It would contribute to the improvement of the ballistic property in ceramic plates.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.490-490
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• 2011

Graphene, hexagonal network of carbon atoms forming a one-atom thick planar sheet, has been emerged as a fascinating material for future nanoelectronics. Huge attention has been captured by its extraordinary electronic properties, such as bipolar conductance, half integer quantum Hall effect at room temperature, ballistic transport over ${\sim}0.4{\mu}m$ length and extremely high carrier mobility at room temperature. Several approaches have been developed to produce graphene, such as micromechanical cleavage of highly ordered pyrolytic graphite using adhesive tape, chemical reduction of exfoliated graphite oxide, epitaxial growth of graphene on SiC and single crystalline metal substrate, and chemical vapor deposition (CVD) synthesis. In particular, direct synthesis of graphene using metal catalytic substrate in CVD process provides a new way to large-scale production of graphene film for realization of graphene-based electronics. In this method, metal catalytic substrates including Ni and Cu have been used for CVD synthesis of graphene. There are two proposed mechanism of graphene synthesis: carbon diffusion and precipitation for graphene synthesized on Ni, and surface adsorption for graphene synthesized on Cu, namely, self-limiting growth mechanism, which can be divided by difference of carbon solubility of the metals. Here we present that large area, uniform, and layer controllable graphene synthesized on Cu catalytic substrate is achieved by acetylene-assisted CVD. The number of graphene layer can be simply controlled by adjusting acetylene injection time, verified by Raman spectroscopy. Structural features and full details of mechanism for the growth of layer controllable graphene on Cu were systematically explored by transmission electron microscopy, atomic force microscopy, and secondary ion mass spectroscopy.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.9
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• pp.839-847
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• 2011

This paper proposes a new guidance law for increasing the lethality of munitions. The well known PNG (Proportional Navigation Guidance) is inadequate for the munitions because of some weaknesses. Even if the munition does not have the impact point error, the acceleration command is non zero because the line-of-sight changes at all times in flight. Therefore, we use a difference between a target and an impact point. This proposed guidance law is similar to PNG in the form, but this guidance law concentrates a correction rate of flight path angle instead of the LOS (Line of Sight) rate. The correction of flight path angle is defined as the amount of impact point error. This impact point error can be calculated by neural networks rapidly. Finally, we show that the simulation results prove the suitability of this law.

• STI Policy Review
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• v.2 no.3
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• pp.1-12
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• 2011

North Korea is now under the pressure of international sanctions due to its nuclear tests, firing of long-range ballistic missiles, the sinking of the ROK naval frigate the Cheonan, and the artillery attack on Yeonpyeong Island that killed four people. To overcome the burden of sanctions North Korea has exerted various efforts to reconstruct its industries. However, it is very unlikely that these reconstruction efforts would produce significant results due to the structural problems of the antiquated infrastructure of North Korean industries. In the future, it is expected that South Korea will have to cooperate with North Korea for the reconstruction of the North Korean economy after the North Korean nuclear issue will be peacefully resolved. South Korean government has to prepare for the reconstruction with careful planning based on analysis of North Korean industries. But, the number of previous studies that have analyzed the technological level of North Korean industries are quite limited. In preparation for the future inter-Korean industrial cooperation, this study tries to analyze the technological level of North Korean industries. The steel industry has been selected as the focus for the main analysis of this study due to the importance of the steel industry as one of key infrastructure industries. Additionally, this study tests the sustainability of the North Korean steel industry by looking into the possibility of whether the North Korean steel industry can sustain or grow while maintaining global competitiveness in the future when the market opens to the world. Such analysis is expected to contribute to the joint prosperity of two Koreas in the short term and the reduction of unification costs in long term.

• Korean Journal of Computational Design and Engineering
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• v.19 no.4
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• pp.324-331
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• 2014

In the design of a combat vehicle, various performances such as firepower, mobility and survivability, etc., should be considered. Furthermore, since these performances relate to each other, design framework which can treat an integrated system should be employed to design the combat vehicle. In this paper, we use empirical interior ballistic and 3D combat vehicle analyses for predicting firepower and mobility performances which are developed in previous study (1) integrated performance modeling. In firepower performance, pitch and roll angle by sequential firing are considered. In mobility performance, vertical acceleration after passing through a bump is regarded. However, since there are many design variables such as mass of vehicle, mass of suspension, spring and damping coefficient of suspension and tire, geometric variables of vehicle, etc., for firepower and mobility performance, we utilize analysis of variance and quality function deployment to reduce the number of design variables. Finally, integrated design optimization is carried out for integrated performance such as firepower and mobility.

• Composites Research
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• v.28 no.4
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• pp.176-181
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• 2015

In this study, the Z-shape fabric design is proposed as the way to enhance the ballistic performance of fabrics which are used as the intermediate layer of stuffed Whipple shield configurations. The Z-shape fabric employs a different boundary condition from those of conventional configurations of fabrics which include 4 edge fixed. Impact analysis on Z-shape aramid yarns and fabrics using LS-DYNA software was performed and the results were compared with 2 edge fixed and 4 edge fixed fabrics to identify the high velocity impact energy absorption characteristics of the Z-shape fabric. It was revealed that the Z-shape showed different impact behavior and higher energy absorption performance than 2 and 4 edge fixed fabrics.