• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.1
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• pp.484-510
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• 2017

Network security is rapidly developing, but so are attack methods. Network worms are one of the most widely used attack methods and have are able to propagate quickly. As an active defense approach to network worms, the honeynet technique has long been limited by the closed architecture of traditional network devices. In this paper, we propose a closed loop defense system of worms based on a Software-Defined Networking (SDN) technology, called Worm-Hunter. The flexibility of SDN in network building is introduced to structure the network infrastructures of Worm-Hunter. By using well-designed flow tables, Worm-Hunter is able to easily deploy different honeynet systems with different network structures and dynamically. When anomalous traffic is detected by the analyzer in Worm-Hunter, it can be redirected into the honeynet and then safely analyzed. Throughout the process, attackers will not be aware that they are caught, and all of the attack behavior is recorded in the system for further analysis. Finally, we verify the system via experiments. The experiments show that Worm-Hunter is able to build multiple honeynet systems on one physical platform. Meanwhile, all of the honeynet systems with the same topology operate without interference.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.3
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• pp.78-83
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• 2014

A special part such as a flow passage opening device is required to prevent the disconnection of fuel transfer in a pressurized fuel tank. To meet this requirement, the device utilizing an acceleration follow-up technique was invented. RecurDyn, a dynamic analysis tool, is introduced in this article to predict the device's performance and to determine parameters affecting it. In the analysis, it is shown that balancing weights can open the passage in accordance with fuel position.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.4
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• pp.319-327
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• 2020

In this study a methodology to evaluate fatigue life of the electronic parts for the fighter radar unit under random vibration loading is presented. To do this, one parameter for the 3-σ RMS quation of Steinberg fatigue model is modified to come up with a printed circuit board(PCB) with multiple electronic parts, while fundamental frequency and dynamic deflection of the PCB are calculated from a MATLAB based finite element computer code. For the RIFA structure selected in this study, the 3-σ RMS fatigue limit displacement is reduced to 0.741 times as much as the Steinberg model. This investigation allows to assess the life of multiple electronic parts mounted on the PCB with reinforced metal cover/body showing non-sinusoidal deflection patterns.

• Journal of the Korean Society of Safety
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• v.22 no.6
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• pp.27-34
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• 2007

Static or dynamic elastomeric O-ring seals are installed between joining parts, and play key roles of high pressure-tightening. Sealing performance and structural safety of the O-ring are dependent on groove design, plain diameter, squeeze and applications such as pressure and temperature. In this study, to solve O-ring problem squeezed and highly pressurized under laterally one-sided constrained condition, hyperelastic FE analyses are performed, and FE results are compared with measured ones by computer-aided tomography, deformed shape and extrusion depth of the O-ring. Through the comparisons, FE analysis technique was verified. In order to evaluate design sensitivity, Taguchi method was used to select FE analysis cases. Adjustment parameters are clearance gap, groove comer radius, plain diameter and squeeze. By means of verified FE analysis technique, it has been analysed how the parameters have effects on contact stress fields, internal stress fields, and extrusion depths. Sealing performance has been evaluated based on contact stress fields and contact widths, and structural safety on internal stress and strain, extrusion lengths.

• Journal of the Society of Naval Architects of Korea
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• v.61 no.2
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• pp.77-87
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• 2024

In the present study, seakeeping performance for an amphibious vehicle in regular head waves was analyzed and evaluated experimentally and numerically. First, seakeeping tests were performed to confirm the vehicle's motion response of heave, pitch motion and vertical acceleration in restricted wavelength ratio conditions for a simplified vehicle shape. Numerical analyses were also conducted for a simplified vehicle shape to validate the numerical solver. To simulate the vehicle's motions, multi-degrees of freedom were calculated by a dynamic fluid-body interaction solver in STAR-CCM+. Comparison between numerical and experimental results was carried out for a simplified vehicle shape. Numerical results are in good agreement with experimental results. Second, numerical analyses were performed for a detailed vehicle shape considering seaway wavelength conditions. The seakeeping performance for an amphibious vehicle was evaluated by comparing with the existing ship's seakeeping performance standards.

• IMMUNE NETWORK
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• v.19 no.1
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• pp.6.1-6.14
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• 2019

Plasmacytoid dendritic cells (pDCs) are a unique subset of cells with different functional characteristics compared to classical dendritic cells. The pDCs are critical for the production of type I IFN in response to microbial and self-nucleic acids. They have an important role for host defense against viral pathogen infections. In addition, pDCs have been well studied as a critical player for breaking tolerance to self-nucleic acids that induce autoimmune disorders such as systemic lupus erythematosus. However, pDCs have an immunoregulatory role in inducing the immune tolerance by generating Tregs and various regulatory mechanisms in mucosal tissues. Here, we summarize the recent studies of pDCs that focused on the functional characteristics of gut pDCs, including interactions with other immune cells in the gut. Furthermore, the dynamic role of gut pDCs will be investigated with respect to disease status including gut infection, inflammatory bowel disease, and cancers.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.3
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• pp.576-585
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• 2002

A three-dimensional Lagrangian explicit time-integration finite element code for analyzing the dynamic impact phenomena was developed. It uses four node tetrahedral elements. In order to consider the effects of strain rate hardening, strain hardening and thermal softening, which are frequently observed in high-velocity deformation phenomena, Johnson-Cook model is used as constitutive model. For more accurate and robust contact force computation, the defense node contact algorithm was adopted and implemented. In order to evaluate the performance of the newly developed three-dimensional hydrocode NET3D, numerical simulations of the oblique impact of mild steel plate by mild steel sphere were carried out. Ballistic limit about various oblique angle between 0 degree and 80 degree was estimated through a series of simulations with different initial velocities of sphere. Element eroding by equivalent plastic strain was applied to mild steel spheres and targets. Ballistic limits and fracture characteristics obtained from simulation were compared with experimental results conducted by Finnegan et al. From numerical studies, the following conclusions were reached. (1) Simulations could successfully reproduce the key features observed in experiment such as tensile failure termed "disking"at normal impacts and outwards bending of partially formed plus segments termed "hinge-mode"at oblique impacts. (2) Simulation results fur 60 degrees oblique impact at 0.70 km/s and 0.91 km/s were compared with experimental results and Eulerian hydrocode CTH simulation results. The Lagrangian code NET3D is superior to Eulerian code CTH in the computational accuracy. Agreement with the experimentally obtained final deformed cross-sections of the projectile is excellent. (3) Agreement with the experimental ballistic limit data, particularly at the high-obliquity impacts, is reasonably good. (4) The simulation result is not very sensitive to eroding condition but slightly influenced by friction coefficient.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.8
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• pp.639-646
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• 2017

In this paper, a new load monitoring system for military aircraft is introduced. This system consists of sensors, an onboard device and an ground analysis equipment. The sensors and onboard device are mounted on the aircraft and the ground analysis equipment is operated on the ground. Through this system, structural static load can be estimated with flight parameters and structural responses can be measured by sensors due to static load, dynamic load and unexpected events. Especially, optical fiber sensors with mutiplexing capability are utilized. The onboard device was specially designed for complying the requirements of relevant military specifications and was verified through a series of the environment tests. This system was used and evaluated through ground structural tests before flight tests. In the near future, this system will be applied to military aircraft as a structural load monitoring system after flight test evaluation.

• 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.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.5
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• pp.279-286
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• 2019

In this study, a numerical investigation is conducted for the shock deceleration prediction of a conical impactor in gas-gun tests. With the development of weapon systems, gas-gun tests are required to validate the survivability and structural reliability of devices under test (DUT) in high-G shock environments, such as those over ten thousand Gs or more. As shock endurance is highly influenced by various bird parameters, such as mass, velocity, and pressure, it is important to determine the appropriate test conditions to generate a high-G shock environment. However, experimental repetitive studies are inefficient to validate test conditions in terms of economic aspects. Therefore, a numerical technique is required to replace experimental gas-gun tests. Here, a numerical investigation is conducted with ANSYS AUTODYN using explicit code. Through this investigation, the dynamic behavior of DUT is presented. In addition, the results of numerical studies are verified through a comparison with the experimental results of a gas-gun test.