• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.3
• /
• pp.29-34
• /
• 2019

Silicon carbide is considered to be a potentially useful material for high-temperature electronic devices, as its large energy band gap and the p-type and/or n-type conduction can be controlled by impurity doping. Particularly, electric conductivity of porous n-type SiC semiconductors fabricated from ${\beta}-SiC$ powder at $2000^{\circ}C$ in $N_2$ atmosphere was comparable to or even larger than the reported values of SiC single crystals in the temperature region of $800^{\circ}C$ to $1000^{\circ}C$, while thermal conductivity was kept as low as 1/10 to 1/30 of that for a dense SiC ceramics. In this work, for the purpose of decreasing sintering temperature, it was attempted to fabricate porous reaction-sintered bodies at low temperatures ($1400-1600^{\circ}C$) by thermal decomposition of polycarbosilane (PCS) impregnated in n-type ${\beta}-SiC$ powder. The repetition of the impregnation and sintering process ($N_2$ atmosphere, $1600^{\circ}C$, 3h) resulted in only a slight increase in the relative density but in a great improvement in the Seebeck coefficient and electrical conductivity. However the power factor which reflects the thermoelectric conversion efficiency of the present work is 1 to 2 orders of magnitude lower than that of the porous SiC semiconductors fabricated by conventional sintering at high temperature, it can be stated that thermoelectric properties of SiC semiconductors fabricated by the present reaction-sintering process could be further improved by precise control of microstructure and carrier density.

• Journal of the Institute of Convergence Signal Processing
• /
• v.21 no.1
• /
• pp.13-20
• /
• 2020

In shipyards, internal materials are assembled after designing and manufacturing each ship's block. Internal material assembly means the installation of parts and equipment except ship's body. In this process, if the assembly of pipes and equipment existing in the block is not done correctly during the assembly between blocks, this causes a lot of costs. In addition, even if the assembly of the internal materials already completed, the production efficiency of the ship is reduced due to rework when problems such as space arrangement of the internal materials occurs. Therefore, this study introduces space arrangement and inspection system before and after hull outfitting work based on coexistence reality technology using 3D design drawing to solve these problems. The various coexistence reality algorithms and inspection systems developed and introduced in this study are based on AR service, which has never been introduced in Korea. So it will be widely applicable to various manufacturing industries using design drawings such as automobiles and architectures as well as ship building process.

• Journal of the Microelectronics and Packaging Society
• /
• v.31 no.3
• /
• pp.18-23
• /
• 2024

Nanoimprint lithography (NIL) is widely used to form structures ranging from micro to nanoscale due to its advantage of generating high-resolution patterns at a low process cost. However, most NIL processes require the use of imprint resists and external elements such as ultraviolet light or heat, necessitating additional post-processes like etching or metal deposition to pattern the target material. Furthermore, patterning on flexible and/or non-planar films presents significant challenges. This study introduces an extreme pressure imprint lithography (EPIL) process that can form micro-/nano-scale patterns on the surface of a flexible rubber magnet composite (RMC) film at room temperature without an etching process. The EPIL technique can form ultrafine structures over large areas through the plastic deformation of various materials, including metals, polymers, and ceramics. In this study, we demonstrate the process and outcomes of creating a variety of periodic structures with diverse pattern sizes and shapes on the surface of a flexible RMC composed of strontium ferrite and chlorinated polyethylene. The EPIL process, which allows for the precise patterning on the surface of RMC materials, is expected to find broad applications in the production of advanced electromagnetic device components that require fine control and changes in magnetic orientation.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.9
• /
• pp.418-424
• /
• 2017

Magnesium has a higher specific strength than other metals and is widely used industry wide due to its excellent vibration absorption ability and electromagnetic wave shielding property.For example, it is used for automobile parts such as car seat frames and cylinder heads, and is widely used in electronic products such as notebook cases and mobile phone cases. In addition, it is in the spotlight as a bone-implant material used to assist in the treatment of damaged bones when the bones are cracked or broken. Currently, Ti alloy, stainless steel and Co-Cr-Mo alloy are used as the implant material, and the Mg alloy remains in research stage. The current problem with bone implant implants is that the patients must undergo reoperation to remove the implants after joint surgery. Magnesium, however, can achieve sufficient strength compared to current materials. In addition, since it is self-decomposed after the recovery, reoperation is not necessary. In this paper, Mg alloys were designed by adding harmless Ca and Zn to the human body. In order to improve the strength and corrosion resistance, the final alloy was designed by adding a small amount of Sr as a grain refiner. The radioactive elements of Sr are harmful to the human body, but other naturally occurring Sr elements are harmless. Microstructure analysis of the alloys was performed by optical microscopy and scanning electron microscopy. The mechanical properties and corrosion characteristics were evaluated by tensile test, potentiodynamic test and immersion test.

• Composites Research
• /
• v.24 no.4
• /
• pp.23-28
• /
• 2011

Recently CFRP laminate joints process by bolts and nets are developed rapidly in aircraft industries. However, there are serious drawback during jointing process. Many hole processes are needed for the manufacturing and structural applications using composite materials. Generally, very durable polycrystalline crystalline diamond (PCD) drill has been used for the CFRP hole process. However, due to the expensive price and slow process speed, chemical vapor deposition (CVD) diamond drill has been used increasingly which are relatively-low durability but easily-adjustable process speed via drill shape change and price is much lower. In this study, the comparison of hole process between PCD and CVD diamond coated drills was done. First of all, CFRP hole processbility was evaluated using the equations of hole processing conditions (feed amount per blade, feed speed). The comparison on thermal damage occurring from the CFRP specimen was also studied during drilling process. Empirical equation was made from the temperature photo profile being taken during hole process by infrared thermal camera. In addition, hole processability was compared by checking hole inside condition upon chip exhausting state for two drills. Generally, although the PCD can exhibit better hole processability, hole processing speed of CVD diamond drill exhibited faster than PCD case.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.16 no.2
• /
• pp.261-270
• /
• 2018

In this study, to replace the 'J-slot joint', a joint device between a disposal canister and an emplacement jig in Deep Borehole Disposal process, a novel joint device was designed and tested. The novel joint device was composed of a wedge on top of a disposal canister and a hook box at the end of a winch system. The designed joint device had merits in that it can recombine an emplaced canister freely without the replacement of the joint component. Moreover, it can be applied to various emplacement jigs such as drill pipes, wire-lines, and coiled tubing. To demonstrate the designed joint device, the joint device (${\Phi}110mm$, H 148 mm), a twin canister string (${\Phi}140mm$, H 1,105 mm), and a water tube (${\Phi}150mm$, H 1,500 mm) as a borehole model were manufactured at 1/3 scale. As deployment muds, Na-type bentonite (MX-80) and Ca-type (GJ II) bentonite muds were prepared at solid contents of 7wt% and 28wt%, respectively. The manufactured joint device showed good performance in pure water and viscous muds, with an operation speed of $10m{\cdot}min^{-1}$. It was concluded that the newly developed joint device can be used for the emplacement and retrieval of a deep disposal canister, below 3~5 km, in the future.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.49 no.2
• /
• pp.1-8
• /
• 2012

This paper presents the accelerometer which is a key component of TPMS(Tire Pressure Monitoring System). Generally a piezoresistive accelerometer has characteristics of lower cost, better linearity and better immunity about the environmnet noise than a capacitive one. Three types of piezoresistive accelerometers are degined and simulated using ANSYS program. The best one is a piezoresistive sensor which is supported by four beams located at the center of the edge of the mass after comparing the characteristics of resonant frequency of the three types. Considering the sensor size and a simulated maximum stress and maximum displacement, the length of beams is set as $200{\mu}m$. The size of a piezoresistive accelerometer is $3.0mm{\times}3.0mm{\times}0.4mm$. The sensor output is characterized by measuring the output characteristic depending on angle. As a result the offset voltage of the accelerometer is 43.2 mV and its sensitivity is $42.5{\mu}V/V/g$. The temperature bias drift is measured. The shock durability of the sensor is 1500g and the measuring range is 0 ~ 60 g.

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

• Polymer(Korea)
• /
• v.32 no.3
• /
• pp.251-255
• /
• 2008

This study suggested antistatic material which can increase anti-static properties and mechanical strength by mixing polystyrene for conveying electronic stuffs with metal salt and ester compound as a anti-static agent. We studied about mechanical, thermal and electrical characteristics by changing the contents of MAH of poly(styrene-co-maleic anhydride), compatibilizer. As the result of measuring residue space charge of the blends of HIPS(75)/TPU(25)/poly(styrene-co-maleic anhydride)(MAH weight ratio : 25, 32, 43.5 wt%), we could find small residue charge in the blend which MAH(25 wt%) was added and it showed the highest values in tensile strength. Additionally we found out the material to which compatibilizer was added kept better anti-static properties than one to which compatibilizer was not added. In the event we could confirm that the adding of PS-co-MAH enables two polymers were mixed well when HIPS/TPU was blended and anti-static agent made easier dissipative in the blend.