• Journal of Adhesion and Interface
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• v.11 no.4
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• pp.149-154
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• 2010

Interfacial evaluation was investigated for single-carbon fiber/phenolic and carbon nanotube (CNT)-phenolic composites by micromechanical technique and electrical resistance measurement combined with wettability test. Compressive strength of pure phenol and CNT-phenolic composites were compared using Broutman specimen. The contact resistance of CNT-phenolic composites was obtained using a gradient specimen by two and four-point methods. Surface energies and wettability by dynamic contact angle measurement were measured using Wilhelmy plate technique. Since hydrophobic domains are formed as heterogeneous microstructure of CNT in the surface, the dynamic contact angle exhibited more than $90^{\circ}$. CNT-phenolic composites exhibited a higher apparent modulus than neat phenolic case due to better stress transferring effect. Work of adhesion, $W_a$ between single-carbon fiber and CNT-phenolic composites exhibited higher than neat phenolic resin due to the enhanced viscosity by CNT addition. It was consistent with micro-failure patterns in microdroplet test.

• Applied Chemistry for Engineering
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• v.20 no.4
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• pp.375-380
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• 2009

Polyepichlorohydrin rubber was treated with sodium azide (Na$N_3$) to replace its chlorine by azide ($N_3$). Then, the azidated polyepichlorohydrin rubber (Az-PECH) was blended with thermoplastic styrene-acrylonitrile copolymer with the rubber/plastic ratio of 80/20, 70/30 and 60/40 (wt/wt). The miscibility, mechanical and dynamic mechanical properties as well as elastic recovery properties of the blends were evaluated by DMA (Dynamic Mechanical Analyzer) and tensile tests. When azidation level in azidated PECH was upto 50%, the blends exhibited excellent miscibility, manifested by a single $T_g$, and fairly good elastic recovery. When azidation level was 75%, the blends showed phase separation. The miscible Az-PECH/SAN blends exhibited typical thermoplastic elastomer like properties, ie. melt processibility and high extensibility as well as good elastic recovery rate. It was also observed from combustion test that higher energy is released with the increase in the azidation level of the Az-PECH in the blends.

• Journal of the Korea Society for Simulation
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• v.27 no.2
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• pp.35-48
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• 2018

The study of air defense against North Korean tactical ballistic missiles (TBM) should consider the rapidly changing battlefield environment. The study for target re-designation for intercept missiles enables effective operation of friendly defensive assets as well as responses to dynamic battlefield. The researches that have been conducted so far do not represent real-time dynamic battlefield situation because the hit probability for the TBM, which plays an important role in the decision making process, is fixed. Therefore, this study proposes a target re-designation algorithm that makes decision based on hit probability which considers real-time field environment. The proposed method contains a trajectory prediction model that predicts the expected trajectory of the TBM from the current position and velocity information by using random forest and moving window. The predicted hit probability can be calculated through the trajectory prediction model and the simulator of the intercept missile, and the calculated hit probability becomes the decision criterion of the target re-designation algorithm for the missile. In the experiment, the validity of the methodology used in the TBM trajectory prediction model was verified and the superiority of using the hit probability through the proposed model in the target re-designation decision making process was validated.

• Korean Chemical Engineering Research
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• v.57 no.4
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• pp.475-483
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• 2019

Special chemical warfare agents are lethal gases that attack the human respiratory system. One of such gases are blood agents that react with the irons present in the electron transfer system of the human body. This reaction stops internal respiration and eventually causes death. The molecular sizes of these agents are smaller than the pores of an activated carbon, making chemical adsorption the only alternative method for removing them. In this study, we carried out a Computational Fluid Dynamics simulation by passing a blood agent: cyanogen chloride gas through an SG-1 gas mask canister developed by SG Safety Corporation. The adsorption bed consisted of a Silver-Zinc-Molybdenum-Triethylenediamine activated carbon impregnated with copper, silver, zinc and molybdenum ions. The kinetic analysis of the chemical adsorption was performed in accordance with the test procedure for the gas mask canister and was validated by the kinetic data obtained from experimental results. We predicted the dynamic behaviors of the main variables such as the pressure drop inside the canister and the amount of gas adsorbed by chemisorption. By using a granular packed bed instead of the Ergun equation that is used to model porous materials in Computational Fluid Dynamics, applicable results of the activated carbon were obtained. Dynamic simulations and flow analyses of the chemical adsorption with varying gas flow rates were also executed.

• Journal of Internet Computing and Services
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• v.21 no.6
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• pp.1-12
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• 2020

Low-Orbit satellite mobile networks can provide services through miniaturized terminals with low transmission power, which can be used as reliable means of communication in the national public disaster network and defense sector. However, the high traffic environment in the emergency preparedness situation increases the new call blocking probability and the handover failure probability of the satellite network, and the increase of the handover failure probability affects the QoS because low orbit satellites move in orbit at a very high speed. Among the channel allocation methods of satellite communication, the FCA shows relatively better performance in a high traffic environment than DCA and is suitable for emergency preparedness situations, but in order to optimize QoS when traffic increases, the new call blocking and the handover failure must be minimized. In this paper, we propose LEO-DBC (LEO satellite dynamic beam width control) technique, which improves QoS by adaptive adjustment of beam width of low-orbit satellites and call time of terminals by improving FCA-QH method. Through the LEO-DBC technique, it is expected that the QoS of the mobile satellite communication network can be optimally maintained in high traffic environments in emergency preparedness situations.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.5
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• pp.879-885
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• 2013

Satellites provide a lot of information and essay roles in the areas of defense and space observations. The precise distances to the satellites are measured by emitting and retro-reflecting a laser. For such surveys, satellite laser ranging (SLR) systems have been developed in different forms and for different areas. The structural integrity of the tracking mount is essential for it to be able to track a high-speed satellite precisely, overcoming the various external and internal disturbances and operating conditions. In this study, the analysis of a tracking mount was performed for weight, wind loads, and inertia loads in order to verify its soundness. The results of the comparison between aluminum and steel were analyzed in order to select the optimal material for the fork and main housing part. In addition, the natural frequency and mode shape were predicted. Optimal material selection and structural integrity will also be verified using static analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2335-2342
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• 2014

If you want to use the unmanned quad rotor for emergency information provision and information about the traffic situation of real-time and moving information is included in the car to help in emergency vehicle operation of the city and in the distribution future innovation the need to consider to have enough safety of the use of silent quad rotor. Therefore, in this study, the unmanned quad rotor system research of safe landing control from the center for the improvement of safety of unmanned quad rotor system you have a motor of four, has taken a good structural balance system based on the dynamic model and motion considering the nonlinear characteristics, and attempts to proceed via non-linearity and system disturbances, tough Fuzzy controller, and analyzed through a computer simulation result.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8654-8664
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• 2015

Beam-type structures with non-uniform cross sections are widely used in mechanical, architectural, and civil engineering fields. This paper deals with dynamic characteristics and vibration problems. Governing equations are first derived by using local coordinates. Their solutions are then assumed by using Galerkin's mode summation method. Bisection method is also applied in solving the determinant of the matrix which can provide natural frequencies. Whereas finite element methods adopt admissible functions satisfying only geometric boundary condition, in this study we apply Galerkin's mode summation method which uses eigen-functions satisfying both governing equations and boundary conditions. Modal analysis and experimental tests are finally performed using simply-supported beams with four different non-uniform cross-sections. Our analytical results then show good agreement with experimental ones.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.11
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• pp.1231-1237
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• 2014

It is essential to perform driving performance tests of military vehicles on rough terrain. A full car test is limited by cost and time constraints, because of which a dynamic analysis via computer simulation is preferred. In this study, a vehicle model is developed using MSC.ADAMS, a commercial multibody analysis program, and compared via experiments. FTire is modeled using the results of a tire performance test to obtain the vertical stiffness. A nonlinear damper is modeled by a characteristic experiment. Leaf springs are modeled with beam force elements and consisted to a vehicle model. The vertical force and acceleration response of the wheel are identified when vehicle is passing over a simple bump as well as a sinusoidal road. The developed vehicle model is verified with the results of a full car test.

• Journal of Mechanical Science and Technology
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• v.16 no.10
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• pp.1187-1200
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• 2002

This paper is concerned with the design or an LMI (Linear Matrix Inequality) -based H$\infty$ controller for a line of sight (LOS) stabilization system and with its robustness performance. The linearization of the system is necessary to analyze various nonlinear characteristics, but the linearization entails modeling uncertainties which reduce its performance. In addition, the stability of the LOS can be adversely affected by angular velocity disturbances while the vehicle is moving. As the vehicle accelerates, all the factors that are Ignored and simplified for the linearization tend to Inhibit the performance of the system. The robustness in the face of these uncertainties needs to be assured. This paper employs H$\infty$ control theory to address these problems and the LMI method to provide a suitable controller with minimal constraints for the system. Even though the system matrix does not have a full rank, the proposed method makes it possible to design a H$\infty$ controller and to deal with R and S matrices for reducing the system order. It can be also shown that the proposed robust controller has a better disturbance attenuation and tracking performance. The LMI method is also used to enhance the applicability of the proposed reduced-order H$\infty$ controller for the system given. The LMI-based H$\infty$ controller has superior disturbance attenuation and reference input tracking performance, compared with that of the conventional controller under real disturbances.