• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.99-100
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• 2006

Cellular metals based on Iron have been intensively investigated during the last two decades. Because of the significant decreasing of the structural density of Iron based cellular structures, numerous technologies have been developed for their manufacturing. Besides the tremendous weight reduction a combination with other properties like energy and noise absorption, heat insulation and mechanical damping can be achieved. This contribution will give an overview about the latest state in Iron based cellular materials, including technologies in manufacturing, properties and potential applications.

• 한국환경과학회지
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• 제11권10호
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• pp.1069-1074
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• 2002

The growth and heavy metal experiments revealed oppositive interactions between toxic metals(Zn and Cd) and Mn when the coastal diatom T. pseudonana were used. Cd and Zn inhibited the algal growth rate only at low Mn ion concentrations and this effect could be accounted for an inhibition of cellular Mn take by the toxic metals. Mn and Zn inhibited cellular Cd take and this indicated a reciprocal effects among the metals with respect to metal take. Saturation kinetics modeling of the take data was consistent with two metals competing with each other for binding to the Mn take system and with both Cd and Mn being transported into the cell by that system. Mathematical modeling of Mn and Cd take data revealed evidence fur a Cd efflux system.

• 대한기계학회논문집A
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• 제31권11호
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• pp.1124-1130
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• 2007

This paper presents a new way for fabricating sandwich plates with tetrahedral truss cores. The tetrahedral truss cores are manufactured through metal expanding and bending process and then brazed with solid face sheets. The properties of sandwich plates with the tetrahedral truss cores composed of a wrought steel SS41 under compression and shear loading have been investigated. Good agreement is observed between the measured and predicted peak strengths. Comparisons with normalized compressive strength for other cellular metals have indicated that the tetrahedral truss structures outperform aluminum open cell forms and woven core sandwich plates.

• 대한금속재료학회지
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• 제50권9호
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• pp.691-695
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• 2012

Calcium phosphate ceramic composites, consisting of hydroxyapatite(HA) and tricalcium phosphate (TCP), were fabricated by solid state sintering in order to investigate the effect of their initial compositions on microstructural evolutions and biocompatibility. All the sintered calcium phosphate ceramics exhibited almost full densification, while the grain growth of the composites increased with an increasing TCP content in the green body. The TCP phase transformed into a Ca-deficient HA phase during sintering via the diffusion of calcium ions from the HA phase into the TCP phase. The phases formed in the composites significantly affected the biocompatibility of the composites. The HA-matrix ceramic composites with TCP had a better cellular response than the pure HA ceramics, presumably due to the newly formed Ca-deficient HA.

• 대한기계학회논문집A
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• 제31권6호
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• pp.694-700
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• 2007

Recently, a new cellular metal, WBK(Wire woven Bulk Kagome) has been introduced. WBK is fabricated by assembling metal wires in six directions into a Kagome-like truss structure and by brazing it at all the crossings. Wires as the raw material are easy to handle and to attain high strength with minimum defect. And the strength and energy absorption are superior to previous cellular metals. Therefore, WBK seems to be promising once the fabrication process for mass production is developed. In this paper, an upper bound solution for the mechanical properties of the bulk WBK under compression is presented. In order to simulate uniform behavior of WBK consisted of perfectly uniform cells, a unit cell of WBK with periodic boundary conditions is analyzed by the finite element method. In comparison with experimental test results, it is found that the solution provides a good approximation of the mechanical properties of bulk WBK cellular metals except for Young's modulus. And also, the brazing joint size does not have any significant effect on the properties with an exception of an idealized thin joint.

• 한국화재소방학회논문지
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• 제25권6호
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• pp.21-26
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• 2011

본 논문에서는 에너지원에 따른 이동전화기(SCH_W830) 배터리의 소손 패턴을 제시함으로써 소비자분쟁 해결의 자료로 활용하고자 한다. 실험이 진행될 때의 주위 온도는 $22{\pm}2^{\circ}C$, 습도는 40~60 %를 유지함으로써 신뢰성을 확보하였다. 실험에 사용된 이동전화기의 배터리 전압은 양극(+)과 음극 (1)(-) 사이의 전압은 4.19 V이며, 양극(+)과 음극 (2)(-) 사이의 전압은 4.18 V로 측정되었다. 일반화염 인가에 의한 이동 전화기의 난연성 시험은 한국산업규격(KS)을 적용하였으며, 일반화염이 30 sec 동안 외함에 인가되어도 내장된 배터리의 소손은 없는 것으로 확인되었다. 생리 식염수(NaCl, 0.9%)에 이동전화기를 180 sec 침수시킨 결과 배터리 단자 사이에 누설전류에 의한 발열로 탄화 및 용융이 발생한 흔적을 확인할 수 있었다. 전자레인지(MWO)를 이용하여 70 sec 동안 이동전화기를 가열하면 금속홀더, 충전용 커넥터, 안테나 등이 내장된 부분에서 용융 및 변색이 확인되며, 그 밖의 부분은 특이사항이 없는 것을 알 수 있다. 즉, 인가된 에너지원의 종류에 따라 이동전화기 외형의 탄화, 내장된 금속 및 유전체, 배터리 단자대의 손상 및 변형 등이 다르게 발생하지만 전압은 비교적 일정한 특성을 보이는 것으로 보아 연소의 확산 패턴, 금속의 용융 및 변형 부분의 특성을 종합적으로 고려하여 해석하면 소손 원인 판정이 가능하다.

• 대한의생명과학회지
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• 제10권3호
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• pp.293-298
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• 2004

This study was performed to compare the growth rates, cellular fatty acid compositions and morphology by using electron microscope of Escherichia coli (E. coli) grown in various conditions including different concentrations of phenol, CdCl₂ and HgCl₂. Ninety eight E. coli strains were isolated from Naktong river and human feces. The content of unsaturated fatty acids, especially 16:1ω7c and 18:1ωc increased as the concentration of phenol and CdCl₂ increased. The content of unsaturated fatty acid increased up to 50 ppb of HgCl₂, but decreased at 75 ppb of HgCl₂. There were more unsaturated fatty acids than saturated fatty acid in the presence of toxic substances. However, the ration was reversed when the affected E. coli was transferred to toxic substance free fresh trypticase soy broth medium. Also, by using transmission electron microscope these cells were observed to various morphological deformation by heavy metals and their deposition on the surface. From these results, we suggested that the changes of major fatty acids composition and morphology of E. coli may be considered to indicate contaminated levels of heavy metals or organic solvents. The information presented here may be useful in predicting effects of heavy-metal and organic solvent contamination in streams and provides a basis for further studies of metal or organic solvent effects on microbial communities.

• Toxicological Research
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• 제23권1호
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• pp.1-9
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• 2007

Transporters are membrane proteins that mediate the transfer of substrate across the cellular membrane. In this overview, the characteristics and the toxicological relevance were discussed for various types of transporters. For drug transporters, the overview focused on ATP-binding cassette transporters and solute carrier family 21A/22A member transporters. Except for OCTN transporters and OATP transporters, drug transporters tend to have broad substrate specificity, suggesting drug-drug interaction at the level of transport processes (e.g., interaction between methotrexate and non-steroidal anti-inflammatory agents) is likely. For metal transporters, transporters for zinc, copper and multiple metals were discussed in this overview. These metal transporters have comparatively narrow substrate specificity, except for multiple metal transporters, suggesting that inter-substrate interaction at the level of transport is less likely. In contrast, the expressions of the transporters are often regulated by their substrates, suggesting cellular adaptation mechanism exists for these transporters. The drug-drug interactions in drug transporters and the cellular adaptation mechanisms for metal transporters are likely to lead to alterations in pharmacokinetics and cellular metal homeostasis, which may be linked to the development of toxicity. Therefore, the transporter-mediated alterations may have toxicological relevance.

• Journal of Welding and Joining
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• 제33권4호
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• pp.37-43
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• 2015

Characteristics of dissimilar metal welds between STS 316L and carbon steel ASTM A516 Gr.70 made with GTAW have been evaluated in terms of microstructure, ferrite content, chemical analysis, hardness and corrosion resistance. Three heat inputs of 9.00, 11.25, 13.00kJ/cm were employed to make joints of dissimilar metals with ER309 wire. Based on microstructural examination, the amount of vermicular type of ${\delta}$-ferrite was increased with increasing heat input due to the increase of Creq/Nieq in the second layer of welds. Based on the EDX analysis of weld metals, Cr and Ni content in the 2nd layer increased while those content in the first layer of welds decreased with heat inputs. Cellular solidification mode in the 1st layer and dendritic solidification mode in the 2nd layer due to different cooling rates were prevailed, respectively. Heat affected zone which formed hard microstructure showed higher hardness than the weld metal. The salt spray test of dissimilar metals weld joints showed that the carbon steel surfaces only corroded. The weight loss rate due to corrosion increased up to 100hours but it decreased above 100 hours. There was little difference in the weight loss caused by corrosion regardless of heat inputs.

• Journal of Magnetics
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• 제21권1호
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• pp.12-19
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• 2016

The <100> oriented $Fe_{83}Ga_{17}$ alloys with various contents of NbC or B were prepared by directionally solidification method at the growth rate of $720mm{\cdot}h^{-1}$. With a small amount of precipitates, the columnar grains grew with cellular mode during directional solidification process, while like-dendrite mode of grains growth was observed in the alloys with higher contents of 0.5 at% due to the dragging effect of precipitates on the boundaries. The NbC precipitates disperse both inside grains and along the boundaries of $Fe_{83}Ga_{17}$ alloys with NbC addition, and the Fe2B secondary phase particles preferentially distribute along the grain boundaries in B-doped alloys. Precipitates could affect grain growth and improved the <100> orientation during directional solidification process. Small amount of precipitate element addition slightly increased the magnetostrictive strain, and a high value of 335 ppm under pre-stress of 15 MPa was achieved in the alloys with 0.1 at% NbC. Despite the fact that the effect on magnetic induction density of small amount of precipitates could be negligible, the coercivity markedly increased with addition of precipitate element for $Fe_{83}Ga_{17}$ alloy due to the retarded domain motion resulted by precipitates.