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급속 소결에 의한 인공관절용 나노구조 2/3 Cr-ZrO<sub>2</sub> 복합재료 제조 및 특성
강현수,강보람,손인진,Kang, Hyun-Su,Kang, Bo-Ram,Shon, In-Jin 한국재료학회 2014 한국재료학회지 Vol.24 No.9
Despite having many attractive properties, $ZrO_2$ ceramic has a low fracture toughness which limits its wide application. One of the most obvious tactics to improve its mechanical properties has been to add a reinforcing agent to formulate a nanostructured composite material. Nanopowders of $ZrO_2$ and Cr were synthesized from $CrO_3$ and Zr powder by high energy ball milling for 10 h. Dense nanocrystalline $2/3Cr-ZrO_2$ composite was consolidated by a high-frequency induction heated sintering method within 5 min at $600^{\circ}C$ from mechanically synthesized powder. The method was found to enable not only rapid densification but also the inhibition of grain growth, preserving the nano-scale microstructure. Highly dense $2/3Cr-ZrO_2$ composite with relative density of up to 99.5% was produced under simultaneous application of a 1 GPa pressure and the induced current. The hardness and fracture toughness of the composite were 534 kg/mm2 and $7MPa{\cdot}m1/2$, respectively. The composite was determined to have good biocompatibility.
강현수,김미진,신용호,전용철,Hyun Su Kang,Mi-Jin Kim,Yong Ho Shin,Yong Chull Jeun 한국식물병리학회 2023 식물병연구 Vol.29 No.4
당근 세균잎마름병을 일으키는 Xanthomonas hortorum pv. carotae는 당근 생산량에 큰 피해를 주는 병 중 하나로 국내에서 아직 방제에 대한 연구가 미흡한 실정이다. 본 연구에서는 당근 세균잎마름병균에 효과적인 농약을 선발하기 위하여 3종의 항생제 streptomycin, oxolinic acid, kasugamycin, 2종의 구리제 copper hydroxide, copper sulfate basic 그리고 길항근권세균 Burkholderia gladioli MRL408-3, Pseudomonas fluorescens TRH415-2, Bacillus cereus KRY505-3을 선정하여 인공배지를 이용하여 이들의 직접적인 항균효과를 조사하였다. 이 중 항생제 streptomycin, oxolinic acid와 길항미생물 MRL408-3을 처리한 배지에서 억제환이 형성되었다. 당근 잎에 농약과 항균효과를 보였던 길항미생물 MRL408-3을 전처리한 후 당근 세균잎마름병균을 접종하였더니 streptomycin과 oxolinic acid을 전처리한 당근 잎에 높은 방제효과를 보였다. 이들 당근 잎 표면의 장방출주사현미경 이미지에서 streptomycin과 oxolinic acid를 전처리한 잎에서는 세균 수가 무처리한 잎과 비교하여 급격히 감소하였다. 이들 결과를 통해 streptomycin과 oxolinic acid와 같은 항생제가 다른 약제에 비해 방제 효과가 뛰어나다는 것을 알 수 있었다. 본 연구는 당근 세균잎마름병에 대한 이상적인 방제 시스템을 구축하는 데 도움이 되는 자료로서 가치가 있을 것으로 생각된다. Bacterial blight of carrot caused by Xanthomonas hortorum pv. carotae (Xhc) is one of the serious diseases of carrot, of which control measures has not been still established in the domestic farm. In this study, in order to select effective sterilizer for bacterial blight of carrots, three antibiotics such as streptomycin, oxolinic acid, kasugamycin, two copper compounds like copper hydroxide and copper sulfate basic and three rhizobacteria Burkholderia gladioli MRL408-3, Pseudomonas fluorescens TRH415-2 and Bacillus cereus KRY505-3 were selected to investigate their direct antibacterial effects using artificial media, aiming to identify effective pesticides against Xhc. Among them, treated medium with antibiotics such as streptomycin, oxolinic acid, and the antagonistic rhizobacteria MRL408-3 were formed inhibition zone. The agrochemicals and the rhizobacteria MRL408-3, which showed antibacterial effects on carrot leaves, pre-treated on the carrot leaves and then inoculated with Xhc. High control effects were shown on the carrot leaves pre-treated with both streptomycin and oxolinic acid. Scanning electron microscopy images of the carrot leaf surfaces showed that the population of bacteria decreased significantly on leaves pre-treated with streptomycin and oxolinic acid. From these results, it can be inferred that antibiotics like streptomycin and oxolinic acid exhibit superior control effects compared to other agents. This study provides valuable insights towards establishing an effective control system for bacterial blight of carrot.
고주파 유도 가열에 의한 나노구조 Mg<sub>4</sub>Al<sub>2</sub>Ti<sub>9</sub>O<sub>25</sub> 합성 및 소결과 기계적 성질
강현수,도정만,윤진국,손인진,Kang, Hyun-Su,Doh, Jung-Mann,Yoon, Jin-Kook,Shon, In-Jin 한국재료학회 2014 한국재료학회지 Vol.24 No.2
Nanocrystalline materials have received much attention as advanced engineering materials with improved physical and mechanical properties, including high strength, high hardness, excellent ductility and toughness. In this study, nanopowders of $Al_2O_3$, MgO and $TiO_2$ were prepared as starting materials by high energy ball milling for the simultaneous synthesis and sintering of the nanostructured compound $Mg_4Al_2Ti_9O_{25}$ by high-frequency induction heating process. The highly dense nanostructured $Mg_4Al_2Ti_9O_{25}$ compound was produced within one minute by the simultaneous application of 80MPa pressure and induced current. The sintering behavior, grain size and mechanical properties of the $Mg_4Al_2Ti_9O_{25}$ compound were evaluated.
다목적 최적화 기법을 이용한 고출력 원심압축기 형상 최적설계
강현수(Hyun Su Kang),이정민(Jeong Min Lee),김윤제(Youn Jea Kim) 대한기계학회 2015 大韓機械學會論文集B Vol.39 No.5
본 연구에서는 원심압축기 임펠러와 디퓨져 블레이드 형상을 반응표면법과 다목적 유전알고리즘 기법을 사용하여 최적설계 연구를 수행하였다. 임펠러와 디퓨져의 블레이드 선단과 후단의 각도와 두께를 3 구간으로 나누어 설계변수로 적용하였으며 수치해석은 상용코드인 ANSYS CFX 를 사용하였다. 실험계획법 중 많이 사용되는 중심합성계획을 이용하여 총 45 개의 설계점에 대한 값을 계산하였다. 계산된 결과를 바탕으로 반응표면을 생성하였으며 반응표면은 최적형상의 임펠러와 디퓨져를 선정하는데 이용하였다. 최적설계의 전 과정은 ANSYS DX 를 사용하였으며, 최적화의 결과로 원심압축기의 주요 성능변수인 등엔트로피 효율과 압력회복계수가 각각 0.3%, 5% 향상된 임펠러와 디퓨져 블레이드 형상을 제시하였다. In this study, a method for optimal design of impeller and diffuser blades in the centrifugal compressor using response surface method (RSM) and multi-objective genetic algorithm (MOGA) was evaluated. A numerical simulation was conducted using ANSYS CFX with various values of impeller and diffuser parameters, which consist of leading edge (LE) angle, trailing edge (TE) angle, and blade thickness. Each of the parameters was divided into three levels. A total of 45 design points were planned using central composite design (CCD), which is one of the design of experiment (DOE) techniques. Response surfaces that were generated on the basis of the results of DOE were used to determine the optimal shape of impeller and diffuser blade. The entire process of optimization was conducted using ANSYS Design Xplorer (DX). Through the optimization, isentropic efficiency and pressure recovery coefficient, which are the main performance parameters of the centrifugal compressor, were increased by 0.3 and 5, respectively.