• Journal of the Microelectronics and Packaging Society
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• v.30 no.3
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• pp.111-118
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• 2023

MXene, a two-dimensional transition metal carbide or nitride, has recently attracted much attention as a lightweight and flexible electromagnetic shielding material due to its high electrical conductivity, good mechanical strength and thermal stability. In particular, the Ti-based MXene, Ti₃C₂T_x and Ti₂CT_x are reported to have the best electrical conductivity and electromagnetic shielding properties in the vast MXene family. Therefore, in this study, Ti₃C₂T_x and Ti₂CT_x films were prepared by vacuum filtration using Ti₃C₂T_x and Ti₂CT_x dispersions synthesized by interlayer metal etching and centrifugation of Ti₃AlC₂ and Ti₂AlC. The electrical conductivity and electromagnetic shielding efficiency of the films were measured after heat treatment at high temperature. Then, X-ray diffraction and photoelectron spectroscopy were performed to analyze the structural changes of Ti₃C₂T_x and Ti₂CT_x films after heat treatment and their effects on electromagnetic shielding. Based on the results of this study, we propose an optimal structure for an ultra-thin, lightweight, and high performance MXene-based electromagnetic shielding film for future applications in small and wearable electronics.

• Journal of Advanced Navigation Technology
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• v.21 no.4
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• pp.413-421
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• 2017

In this paper, we designed and fabricated a compact UHF receive module for efficient operation such as tactical and operation situation, target location information confirmation, target reset using Link-K(Korean joint tactical data link system). And the effect of target reset was analyzed by simulation. The designed module consists of UHF(ultra high frequency) receiver section, control section, and power distribution section. The UHF receiver section performs frequency down conversion, filtering and automatic gain control, etc. The control section demodulates frequency down-converted signals, extracts information, and performs external interworking. The power distribution section supplies external power, generates and supplies the power required by each section. The fabricated module was dimension of $105{\times}105{\times}80mm$ and weighed 1.10 kg and The receiving distance is more than 50 km.

• Nuclear Engineering and Technology
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• v.47 no.6
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• pp.678-699
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• 2015

Although the harsh space environment imposes many severe challenges to space pioneers, space exploration is a realistic and profitable goal for long-term humanity survival. One of the viable and promising options to overcome the harsh environment of space is nuclear propulsion. Particularly, the Nuclear Thermal Rocket (NTR) is a leading candidate for nearterm human missions to Mars and beyond due to its relatively high thrust and efficiency. Traditional NTR designs use typically high power reactors with fast or epithermal neutron spectrums to simplify core design and to maximize thrust. In parallel there are a series of new NTR designs with lower thrust and higher efficiency, designed to enhance mission versatility and safety through the use of redundant engines (when used in a clustered engine arrangement) for future commercialization. This paper proposes a new NTR design of the second design philosophy, Korea Advanced NUclear Thermal Engine Rocket (KANUTER), for future space applications. The KANUTER consists of an Extremely High Temperature Gas cooled Reactor (EHTGR) utilizing hydrogen propellant, a propulsion system, and an optional electricity generation system to provide propulsion as well as electricity generation. The innovatively small engine has the characteristics of high efficiency, being compact and lightweight, and bimodal capability. The notable characteristics result from the moderated EHTGR design, uniquely utilizing the integrated fuel element with an ultra heat-resistant carbide fuel, an efficient metal hydride moderator, protectively cooling channels and an individual pressure tube in an all-in-one package. The EHTGR can be bimodally operated in a propulsion mode of $100MW_{th}$ and an electricity generation mode of $100MW_{th}$, equipped with a dynamic energy conversion system. To investigate the design features of the new reactor and to estimate referential engine performance, a preliminary design study in terms of neutronics and thermohydraulics was carried out. The result indicates that the innovative design has great potential for high propellant efficiency and thrust-to-weight of engine ratio, compared with the existing NTR designs. However, the build-up of fission products in fuel has a significant impact on the bimodal operation of the moderated reactor such as xenon-induced dead time. This issue can be overcome by building in excess reactivity and control margin for the reactor design.

• Composites Research
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• v.33 no.5
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• pp.262-267
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• 2020

With increasing demands for high-speed machining and lightweight design of machine tools, increasing likeliness of generation of machine tool spindle vibrations has become an important issue. Spindle vibration has a significant impact on the surface finish of the workpiece in ultra-precision machining. It is necessary to resolve the machine tool spindle vibration in various machining processes to improve machining accuracy. In this paper, a TiC-SKH51 metal-matrix composite was used to suppress the vibration of the machine tool spindle. To confirm the dynamic characteristic of the TiC-SKH51 composite, impact hammer tests were conducted. After verifying the reliability of a finite element analysis (FEA) by comparing the results of the impact hammer test with the modal analysis using FEA, the analysis of the machine tool spindle model was performed. The FEA results show that the TiC-SKH51 composite applied machine tool spindle can be utilized to suppress the vibration generation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.4
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• pp.2276-2291
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• 2017

Data protection of removable storage devices is an important issue in information security. Unfortunately, most existing data protection mechanisms are aimed at protecting computer platform which is not suitable for ultra-low-power devices. To protect the flash disk appropriately and efficiently, we propose a trust based USB flash disk, named UTrustDisk. The data protection technologies in UTrustDisk include data authentication protocol, data confidentiality protection and data leakage prevention. Usually, the data integrity protection scheme is the bottleneck in the whole system and we accelerate it by WH universal hash function and speculative caching. The speculative caching will cache the potential hot chunks for reducing the memory bandwidth pollution. We adopt the symmetric encryption algorithm to protect data confidentiality. Before mounting the UTrustDisk, we will run a trusted virtual domain based lightweight virtual machine for preventing information leakage. Besides, we prove formally that UTrustDisk can prevent sensitive data from leaking out. Experimental results show that our scheme's average writing throughput is 44.8% higher than that of NH scheme, and 316% higher than that of SHA-1 scheme. And the success rate of speculative caching mechanism is up to 94.5% since the access pattern is usually sequential.

• Composites Research
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• v.29 no.4
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• pp.161-166
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• 2016

Carbon nanotube buckypaper (CNTs-BP)/thermoplastic polyurethane (PU) elastomer composites were successfully fabricated. The CNTs-BP/PU nanocomposites exhibited simultaneous improvements in both tensile modulus and strength by 1360 and 430%, respectively, as compared to pure PU. Possible reinforcing mechanisms were evidenced by SEM analyses and tensile tests. The CNTs-BP/PU nanocomposites can be potentially used as an inter-reinforcing agent in ultra-lightweight, high-strength aircraft, carbon-fiber-reinforced plastics, etc.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.5
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• pp.869-876
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• 2001

In modern wireless communication, it has been regarded as a important problem for the spectrum efficiency to utilize the limited frequency-resource efficiently. In addition, the system architecture has been designed for low cost, low power consumption and ultra-lightweight. In this paper, we directly modulated the BCPFSK with a superior spectrum efficiency using the DDS and applied the direct conversion to the system architecture. Finally, we designed a transceiver which has the 433 MHz BCPFSK output and evaluated the system performance. In the measured result, we know that as for spectrum and the power efficiency, BCPFSK method is better than conventional one. Also, the results of the designed system is 433.92 MHz in center frequency and about 33 dBc in carrier suppression ratio. And we get the better results in local oscillator leakage and the spurious of the ISM out-band the same as -69dBc and under 60dBc.

• Design & Manufacturing
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• v.14 no.4
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• pp.65-70
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• 2020

Partial reinforcement of sheet metal parts with CFRP patch is a technology that can realize ultra-lightweight body parts while overcoming the high material cost of carbon fiber. Performing these patchworks with highly productive press equipment solves another issue of CFRP: high process costs. The A-pillar is the main body part and has an undercut shape for fastening with other parts such as roof panels and doors. Therefore, it is difficult to bond CFRP patches to the A-pillar with a general press forming tool. In this paper, a flexible system that applies uniform pressure to complex shapes using ceramic particles and silicone rubber is proposed. By benchmarking various A-pillars, a reference model with an undercut shape was designed, and the system was configured to realize a uniform pressure distribution in the model. The ceramic spherical particles failed to realize the uniform distribution of high pressure due to their high hardness and point contact characteristics, which caused damage to the CFRP patch. Compression equipment made of silicone rubber was able to achieve the required pressure level for curing the epoxy. Non-adhesion defects between the metal and the CFRP patch were confirmed in the area where the bending deformation occurred. This defect could be eliminated by optimizing the process conditions suitable for the newly developed flexible system.

• Journal of Industrial Convergence
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• v.20 no.6
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• pp.37-45
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• 2022

With the development of the Internet of Things (IoT), related network infrastructures require new technologies to protect against threats such as external hacking. This study proposes an L-PBFT consensus algorithm that can protect IoT networks based on a blockchain consensus algorithm. We designed a blockchain (private) model suitable for small networks, tested processing performance for ultra-small/low-power IoT devices, and verified stability. As a result of performance analysis, L-PBFT proved that at least the number of nodes complies with the operation of the consensus algorithm(minimum 14%, maximum 29%) and establishes a trust network(separation of secure channels) different from existing security protocols. This study is a 4th industry convergence research and will be a foundation technology that will help develop IoT device security products in the future.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.707-714
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• 2023

The Internet of Things, which is the key factor of the 4th industrial revolution, are apt to apply to many systems. The existing security mechanism cannot be realized with limited resources such as low capacity of devices and sensors. In order to apply IoT system, a new structure and ultra-lightweight encryption is required. In this paper, we analyzed security issues that can operate in Internet-based smart home networks, and to solve the critical issues against these attacks, technologies for device protection between heterogeneous devices. Security requirements are required to protect from attacks. Therefore, we analyzed the demands and requirements for its application by analyzing the security architecture and features in smart home network.