• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.123-124
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• 2006

Usually, hydraulic cylinder is widely used as the actuator in the equipment of construction machines, airplane and military machines. In case of these devices, due to use under severe environment such as water, $SiO^2$ and dust, etc. seal which has high packing ability and long service life has been required. These characteristics are largely influenced by material and geometries of seal such as approach angle, withdrawal angle and interference. Recently, many a study about seal material has been performed so that many materials have been developed. But the concrete studies including the relationships between geometry of seal and sealing performance have hardly been performed yet. Therefore, in this study, we predicted the deformation behavior and contact normal distribution of dust seal with the variation of geometries of seal lip using finite element analysis. And based on the results of analyses, we discussed the effects of the design variables fur sealing performance of the dust seal.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.6
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• pp.91-100
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• 2016

Efficiency characteristics of centrifugal turbopumps for a liquid rocket engine were investigated. Predicting the performance of pumps for a turbopump assembly test, the variation on pump efficiency by working fluids was analyzed from pump component tests. Water and liquid nitrogen (LN2) were used for the component test, kerosene (Jet A-1) and liquid oxygen (LOX) were adapted for the turbopump assembly (TPU) test as working fluids. Overall performance of the pumps was investigated covering design/off-design operating points and the pump efficiency on the environment of real media (LOX/kerosene) could be modified from the pump component tests.

• Textile Coloration and Finishing
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• v.34 no.3
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• pp.173-184
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• 2022

In this study, the TPU film was laminated on an aramid fabric or circular knits in order to implement an air cushion material that can respond to high impact forces in case of a fall and is easy to expand. To increase the bonding strength between the fabric layer and the film layer, a primer layer was formed in two ways: one for thermally bonding and laminating PET film and two for coating and aging hot melt type PUR adhesive. The tensile strength of the aramid air cushion was 2.5 times higher than that of the circular knits, but the tensile elongation of the aramid air cushion was very low compared to that of the circular knits. The tear strength of the aramid air cushion was about twice or more superior to that of the circular knits, the primer treatment method was good at A, and the peel strength was excellent at method A. The aramid air cushion was the lightest in weight. Summarizing the above results, it was best to combine the air cushion material with aramid woven fabric and primer treatment method A to cope with the high impact force applied when falling.

• Textile Coloration and Finishing
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• v.33 no.4
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• pp.269-279
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• 2021

In this study, the laminating of TPU film after coating of primer adhesive on the fabrics was applied in order to secure the strength to withstand a fall from a higher altitude by increasing the adhesion between the fabric and the film layer. It seems that the fineness of the yarn and the weave construction have a greater effect than the type of the laminating films. The order of superiority of the laminated fabrics by film type and thickness was the same for 1000 denier and 210 denier fabrics, and the tendency was consistent with the order of superiority in the film properties and peel strength tests. The tear strength of laminating fabrics increased three to four times for 1000 denier fabrics compared to the fabric alone, but it decreased by 2 times for the 210 denier fabrics. Summarizing the above results, it is most appropriate to combine 1000d fabric with three types of laminating films(100~200㎛ thickness) of A(0.2T) or B(0.15T) or D(0.1T) considering the air pressure resistance, the impact resistance during the fall, and the durability against damage during use.

• Fashion & Textile Research Journal
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• v.24 no.6
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• pp.812-824
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• 2022

This study proposes to develop a 3D printed re-entrant(RE) strip by shape memory thermoplastic polyurethane that can be deformed and recovered by thermal stimulation. The most suitable 3D printing infill density condition and temperature condition during shape recovery for mechanical behavior were confirmed. As the poisson's ratio indicated, the higher the recovery temperature, the closer the poisson's ratio to zero and the better the auxetic properties. After recovery testing for five minutes, it appeared that the shape recovery ratio was the highest at 70℃. The temperature range when the shape recovery ratio appeared to be more than 90% was a recovery temperature of more than 50℃ and 60℃ when deformed under a constant load of 100 gf and 300 gf, respectively. This indicated that further deformation occurred after maximum recovery when recovered at a temperature of 80℃, which is above the glass transition temperature range. As for REstrip by infill density, a shape recovery properties of 100% was superior than 50%. Additionally, as the re-entrant structure exhibited a shape recovery ratio of more than 90%, and exhibited auxetic properties. It was confirmed that the infill density condition of 100% and the temperature condition of 70℃ are suitable for REstrips for applying the actuator.

• Proceedings of the Korea Information Processing Society Conference
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• 2020.11a
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• pp.870-872
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• 2020

본 시스템은 어린이보호구역에 발생하는 차량사고가 불법주정차된 차량으로 인한 사각지대에 의해 발생되는 것에 착안하여 보행자를 인식하여 운전자들에게 알려 안전운전을 유도하여 사고를 예방해 주는 시스템이다 본 시스템은 영상인식장치, 경광장치, 중계장치, 차량 내 경고장치, 원격 트래픽 경고 수신기로 구성되어 있으며 영상인식장치가 edge-TPU 장치를 활용하여 카메라로부터 입력받은 영상을 모바일넷 기반의 딥러닝으로 처리하여 보행자, 차량, 그밖의 물체를 인식한다. 보행자가 인식되면 외부에서 경광장치가 발광하여 신호를 보내고, 중계장치를 통해 차량 내 경고장치로 보행자 경고 신호를 보낸다. 실험 결과 영상인식을 통해 보행자와 차량을 분류 인식할 수 있음을 확인하였다. 이러한 시스템은 어린이 보호구역에서 발생할 수 있는 교통사고를 방지하기 위해 효과적임을 확인할 수 있었다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2020.07a
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• pp.13-14
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• 2020

본 논문에서는 엣지 컴퓨팅 환경에서 머신러닝을 활용해 에스컬레이터 이상 감지 및 결함 분류를 하는 연구를 진행하였다. 엣지 컴퓨팅 기반 머신러닝을 사용해 에스컬레이터의 이상 감지 및 결함 분류를 위한 OneM2M환경을 구축하였으며 에스컬레이터에서 발생하는 소음에서 고장 유형에 따라 나타나는 주파수를 이용한다. Edge TPU를 활용해 엣지 컴퓨팅 시스템의 처리량을 최대화하고, 각 작업의 수행시간을 최소화함으로써 엣지 컴퓨팅 환경에서 이상 감지와 결함 분류를 수행할 수 있다.

• The Research Journal of the Costume Culture
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• v.31 no.5
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• pp.692-704
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• 2023

This study analyzed 214 sports knee braces found on Chinese websites between October 2022 and November 2022 to assess product type (impact protection material, fastening method, and protection method), material composition, size, weight, and main characteristics. The product type was further categorized according to (1) use of hard guard and soft guard protection method; (2) cover type, strap type, and slip-on type fastening method; and (3) pressure type and support type protection method. It also noted the physical shock protection materials used, including foam (EVA or polyurethane) attached to joints as a buffer material and plastic (TPU or PP) that protects the user's knee from external impacts. The study found that the materials that primarily comprise sports knee braces are a combination of nylon, polyester, and neoprene. Additionally, it found that most sports knee braces available on the market are available in three sizes based on knee circumference: M (35-38cm), L (38-41cm), and XL (41-44cm), while some products are available in one size only. Furthermore, the majority of the 214 products studied weighed 200g, followed by 1,000g. Finally, in terms of product characteristics, many sports knee braces utilize ring-shaped silicone pads to distribute the load pressure on the knees or incorporate sturdy adhesive velcro to improve knee stability.

• Korean Journal of Optics and Photonics
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• v.25 no.6
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• pp.326-333
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• 2014

Phase-measuring deflectometry is a full-field gradient measuring technique that lends itself very well to testing specular optical surfaces. We have measured the deformation of the surface of a lens by transmission deflectometry with liquids. In this study, a method is proposed for measuring the refractive index distribution of a transparent object component. The proposed method combines transmission deflectometry with liquids. The deformed fringe patterns of a sample immersed in different fluids are recorded, and then the three-dimensional phase information of the sample is reconstructed numerically. We have used phase-shifting and temporal phase-unwrapping methods to retrieve the phase from the measured deformed fringe pattern, and we have used a least-squares method to find the height information of the specular surface from the calculated slope. In particular, we have proposed a theoretical model for determining the refractive index of sample and planar convex lens are demonstrated experimentally.

• Journal of Fashion Business
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• v.21 no.4
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• pp.116-126
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• 2017

This study applied a segmented hard shell design on knee protectors for children with the objective of increasing mobility. The prototype of the hard shell that does not correspond to movement of the body among components of the knee protector was developed. Surface modeling was conducted based on 3D knee data to enhance comfort through optimized fit on the knee joint where the hard shell would be worn. For this, previous studies on changes in skin near the knee joint during knee flexion were reviewed to establish basic segmental lines. The basic design included six segments, and the number of segments was used as the design variable by increasing or decreasing it to 0, 3, 6, 9, and 14 segments. A prototype was produced from 3D printing with TPU material, worn for wearing assessment. Results revealed fewer numbers of segments resulting in less fit with the body, while actual appearance was stable. Meanwhile, the number of proper segments improved better fit with the body during movement. The wearing assessment revealed the amount of gap reflects change in skin length depending on movement. Assessment results demonstrated basic segment design, S6 with 6 segments, had the best design and most optimized fit. Findings in this study can provide key data for designing knee protection products for children.