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Hui‑Jun Yi,Jin‑Woo Kim,Young‑Lak Kim,Sangyong Shin 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.8
Wire-arc additive manufacturing has emerged as a technology that could replace the conventional manufacturing processof titanium alloys. However, it produces a coarse β grain, which can accumulate via several deposited materials, resulting isstrong texture and anisotropy. To investigate potential solutions, the effects of the cooling rate on the resulting microstructureand tensile properties were studied. The cooling rate of the deposited materials was adjusted by interpass temperaturecontrol. Under rapid cooling, fine α + α′ grain with a low aspect ratio were observed and tensile and hardness propertieswere also improved.
신재범,이상영,김재수,박성희,임준석 韓國海洋大學校 附設 海洋科學技術硏究所 1992 硏究論文集 Vol.1 No.1
In the active sonar development, the reverberation is one of the major factors to be overcome like the clutter in the rader development. Unfortunately real reverberation data in various cases cannot be achieved so easily as real clutter data can be and there is a trend to build a simulator before a complex sonar system is developed. In the sonar simulator, the synthesized reverberation signal is necessary. In this paper we propose an algorithm to simulate the reverberation for the moving active sonar to use it in a simulator, and show some simulated results.
이종현,신장규,이상룡,천희곤,조찬섭,심준환,류인식,박석홍,허정준,박기열 경북대학교 센서기술연구소 1994 연차보고서 Vol.1994 No.-
자동차의 air-bag 장치에 실용될 수 있는 압저항형 단결정 실리콘 가속도센서 칩을 개발하기 위하여 결정 실리콘 미세구조의 제조방법을 확립하고, 단위공정의 검증을 통하여 일괄공정에 의한 PROTO-TYPE 칩을 만드는 기술을 연구하였다. 단결정 실리콘 미세구조는 선택확산법을 이용하여 정확히 선택된 영역에만 air-gap을 형성하여 미세구조의 측면식각을 방지하는 선택확산법에 의한 실리콘 마이크로머시닝 기술로 제조하였다. 일괄공정을 위한 단위공정확립을 위하여 PROTY-TYPE 8빔 브릿지형 가속도 센서를 제조하였다. 제조된 칩의 가속도에 따른 출력전압은 선형성을 나타내고 있으며, 감도는 약 50 ㎶/V·g로 나타났다. 이 감도는 50G용 가속도센서의 사양을 만족하지 못했다. 이는 공정에 의한 문제라기 보다는 가속도센서의 시뮬레이션에 의해 설계한 구조가 이미 원하는 감도에 못 미친다는 것으로 생각된다. 따라서 2차 공정으로 제조될 가속도센서의 파라미터를 SuperSAP 유한요소 패키지를 이용하여 실리콘 미세구조부의 파라미터에 따른 특성을 시뮬레이션하였다. 설계된 50G용 가속도센서의 mass Pad의 반경 및 빔 길이, 빔 폭, 빔 두께, 그리고 mass의 각 파라미터 값은 700 ㎛, 120 ㎛, 5 ㎛, 1.0 ㎎ 이었다. 반도체 공정기술, 관성질량 제조법 및 선택확산을 이용한 마이크로머시닝을 사용하여 일괄공정으로 8빔 브린지형 가속도센서를 제조하였다. We researched the establishment of the silicon microstructure fabrication technique to develop a piezoresistive type silicon acceleration sensor chip and the technique to make a proto-type chip by the verification of the unit-process. Silicon microstructure is fabricated silicon micro-machining by selective diffusion method. This method prevent a side-etching of microstructure because selective diffused region is only formed an air-gap. We fabricated a proto-type 8-beam bridge-type acceleration sensor to establish the unit-process for the batch-process. The output voltage of the chip represented linearity with acceleration, and the sensitivity was about 50 ㎶/V·g. But this sensitivity dosen't satisfy the requirements of a practical acceleration sensor. The cause of this result is assumed not process problem, but the structure designed by simulation isn't suitable already. Threfore, the characteristics of parameters of the acceleration sensor that will be fabricated by 2nd-process is simulated by SuperSAP finite-element package. The determined parameter values of beam length, beam width, beam thickness, mass, and mass radius are 120 ㎛, 5 ㎛, 1.0 ㎎, and 700 ㎛, respectively. We fabricated 8-beam bridge-type acceleration sensor by batch-process using a semiconductor process technique, proof-mass fabrication method, and micromachinig using selective diffusion.
수화발열량차 및 단열양생 공법을 활용한 매스콘크리트의 현장적용
한준희 ( Han Jun-hui ),임군수 ( Lim Gun-su ),신세준 ( Shin Se-jun ),전충근 ( Jeon Choung-keun ),김종 ( Kim Jong ),한민철 ( Han Min-cheol ) 한국건축시공학회 2023 한국건축시공학회 학술발표대회 논문집 Vol.23 No.1
This study is tocompare and analyze the results of hydration heat analysis and on-field measurements using the method with hydration heat difference and insulation curing method for controlling hydration heat in mass concrete. As a result of the analysis, the temperature difference between the center and the surface was predicted very similarly, and the mass concrete surface was controlled to a safe level when evaluating with a temperature crack index, and after being finished, it was confirmed that there was no hydration crack.
매스콘크리트의 수화열 해석 및 현장 계측을 통한 수화발열량차 공법의 현장적용성
한준희 ( Han Jun-hui ),임군수 ( Lim Gun-su ),신세준 ( Shin Se-jun ),전충근 ( Jeon Choung-keun ),김종 ( Kim Jong ),한민철 ( Han Min-cheol ) 한국건축시공학회 2023 한국건축시공학회 학술발표대회 논문집 Vol.23 No.1
In this study, the hydration heat differential method was applied to mass concrete structures, and the hydration heat analysis was compared and analyzed with on-site measurement results. The results showed that the temperature history measurements of mass concrete were managed at a difference of 8.4°C, and although there was some deviation in thermal stress, a similar trend was observed. Consequently, it was determined that the thermal stress on the surface of mass concrete is less than its tensile strength, which would prevent the occurrence of thermal cracks.
Hui-Jun Yi,Jin-Woo Kim,Young-Lak Kim,Sangyong Shin 한국재료학회 2021 한국재료학회지 Vol.31 No.5
Wire arc additive manufacturing (WAAM) is being considered as a technology to replace the conventional manufacturing process of titanium alloys. However, coarse β grains, which can extend through several deposited materials, result in strong textures and anisotropy. As a solution, we study the plastic deformation effects of ultrasonic needle peening (UNP) on the microstructure. UNP treated materials deform plastically and the dislocation density increases. Fine α+α' grains with low aspect ratio are observed in the UNP treated specimens. UNP treated WAAM Ti-6Al-4V alloys have higher strength and lower elongation than those characteristics of WAAM Ti-6Al-4V alloys. Due to UNP treatment, the z-axis directional specimens exhibit a greater effect of reducing elongation than do the x-axis directional specimens. The UNP treatment produces fine grains in proportion to the number of times UNP is performed, thereby increasing strength. UNP processes produce a large number of dislocations in the WAAM Ti-6Al-4V alloys, with the most dislocations being formed at the surface.
Shin, Jae Hui,Baek, Seung Ki,Cho, Sung Woon,Kang, Se Hwang,Bang, Jun Sik,Cho, Hyung Koun The Electrochemical Society 2015 Journal of the Electrochemical Society Vol.162 No.8
<P>We investigated the influence of antimony (Sb) dopants (6 ∼ 11 at%) with multivalent metal ions (Sb<SUP>3+</SUP>/Sb<SUP>5+</SUP>) on the electrical properties of ZnO nanorods for application in photoelectronic devices. More vertically aligned and more conductive <I>n-</I>type ZnO nanorods were effectively prepared via the electrochemical deposition process. The addition of a small amount of Sb in the ZnO nanorods induced a faster growth rate and high aspect ratio. The remarkable enhancement of electrical conductivity resulting from Sb doping was confirmed by photoelectrochemical performance and current-voltage measurements in all oxide <I>n-</I>type ZnO/<I>p-</I>type Cu<SUB>2</SUB>O heterojunctions, which was ascribed to the substitution of Sb for Zn sites without defect complexes. These results demonstrate the feasibility of using Sb as an <I>n-</I>type dopant in ZnO nanorods in a wet-based electrodeposition process.</P>
Shin, Young Min,Park, Jong-Seok,Jeong, Sung In,An, Sung-Jun,Gwon, Hui-Jeong,Lim, Youn-Mook,Nho, Young-Chang,Kim, Chong-Yeal 한국생물공학회 2014 Biotechnology and Bioprocess Engineering Vol.19 No.2
An artificial construct mimicking the intrinsic properties of the natural extracellular matrix in bones has been considered an ideal platform for bone tissue engineering, as it can present an appropriate microenvironment and regulate cell behaviours. In this report, we introduce biodegradable composite scaffolds consisting of polycaprolactone (PCL) and biphasic calcium phosphate (BCP). The scaffolds were fabricated by a salt-leaching process, and the ability of the scaffolds to facilitate osteogenic differentiation was investigated using human mesenchymal stem cells (hMSCs). The scaffolds had an inter-connected porous structure with quadrilateral pores of approximately $200{\sim}500{\mu}m$ in width. The mechanical properties of the scaffolds changed as the BCP content was increased in the starting mixture. In the hMSC experiment, although we found that hMSCs adhered to the surface, as well as the inside, of the scaffolds, the incorporated BCP did not increase the proliferation of the hMSCs over 7 days in culture. Interestingly, the alkaline phosphatase (ALP) activity was 4 times higher on the PCL/BCP composite scaffold ($0.12{\pm}0.03nmol/min/{\mu}g$ protein) thanon the PCL scaffold ($0.03{\pm}0.01nmol/min/{\mu}g$ protein), suggesting that BCP can aid in generating a local environment that promotes bone regeneration. Therefore, a strategy combining polymers and ceramics can be considered a useful platform for bone tissue engineering.