• Title/Summary/Keyword: KAIST

Search Result 6,998, Processing Time 0.039 seconds

A Carbon Nanotubes-Silicon Nanoparticles Network for High Performance Lithium Rechargeable Battery Anodes

  • Kim, Byung Gon;Shin, Weon Ho;Lim, Soo Yeon;Kong, Byung Seon;Choi, Jang Wook
    • Journal of Electrochemical Science and Technology
    • /
    • v.3 no.3
    • /
    • pp.116-122
    • /
    • 2012
  • As an effort to address the chronic capacity fading of Si anodes and thus achieve their robust cycling performance, herein, we develop a unique electrode in which silicon nanoparticles are embedded in the carbon nanotubes network. Utilizing robust contacts between silicon nanoparticles and carbon nanotubes, the composite electrodes exhibit excellent electrochemical performance : 95.5% capacity retention after 140 cycles as well as rate capability such that at the C-rate increase from 0.1C to 1C to 10C, the specific capacities of 850, 698, and 312 mAh/g are obtained, respectively. The present investigation suggests a useful design principle for silicon as well as other high capacity alloying electrodes that undergo large volume expansions during battery operations.

Molecular Design for the Formation of Two-dimensional Molecular Networks: STM Study of ${\gamma}$-phenylalanine on Au(111)

  • Jeon, A-Ram;Youn, Young-Sang;Lee, Hee-Seung;Kim, Se-Hun
    • Proceedings of the Korean Vacuum Society Conference
    • /
    • 2011.08a
    • /
    • pp.205-205
    • /
    • 2011
  • The self-assembly of ${\gamma}$-phenylalanine on Au(111) at 150 K was investigated using scanning tunneling microscopy (STM). Phenylalanine can potentially form two-dimensional (2D) molecular networks through hydrogen bonding (through the carboxyl and amino groups) and ${\pi}-{\pi}$ stacking interactions (via aromatic rings). We found that ${\gamma}$-phenylalanine molecules self-assembled on Au(111) surfaces into well-ordered structures such as ring-shaped clusters (at low and intermediate coverages) and 2D molecular domains (intermediate and monolayer coverages), whereas ${\alpha}$-phenylalanine molecules formed less-ordered structure on Au(111). The self-assembly of ${\gamma}$- but not ${\alpha}$-phenylalanine may be related to the flexibility of the carboxyl and amino groups in the molecule. Moreover, as expected, the 2D molecular network of ${\gamma}$-phenylalanine on Au(111) was mediated by a combination of hydrogen bonding and ${\pi}-{\pi}$ stacking interactions.

  • PDF

Water-Repellent Macroporous Carbon Nanotube/Elastomer Nanocomposites by Self-Organized Aqueous Droplets

  • Lim, Bo-Kyung;Lee, Sun-Hwa;Park, Ji-Sun;Kim, Sang-Ouk
    • Macromolecular Research
    • /
    • v.17 no.9
    • /
    • pp.666-671
    • /
    • 2009
  • Water repellent elastomeric surfaces were fabricated successfully on SBS/MWNT nanocomposites films using the breath figure method and subsequent thermal treatment. The uniformly dispersed CNTs were found to play significant roles in tuning the size and ordering of the macroporous morphology at the nanocomposite surface as well as enhancing the mechanical properties of nanocomposites. In particular, the CNTs dispersed in a nanocomposite solution retarded the coarsening process of aqueous droplets during the breath figure process and decreased the pore size in the finally fabricated film. The water contact angle measurement showed that the double-scale structure comprised of self-organized macropores and surface the roughness induced by a thermal treatment produced a highly water-repellent nanocomposite surface.

Discovery of C2 Swan Band and CN emission in Spark Discharge Experiment

  • Song, In-Ok;Mo, Younghoon;Ryu, Jein;Chang, Hoyon;Hwang, Ki-Wook;Chun, Man-Seog;Oh, Jinho;Hahn, Sangjoon
    • The Bulletin of The Korean Astronomical Society
    • /
    • v.46 no.2
    • /
    • pp.74.1-74.1
    • /
    • 2021
  • 밀러-유리 실험으로 알려진 전기방전 실험은 지구초기대기를 모사하여 아미노산을 합성하여, 지구에서 생명의 기원을 연구하는 실험중의 하나이다. 메탄(CH4), 암모니아(NH3), 질소(N2) 가스를 주입하고 전기방전으로 에너지를 가했다. 그 결과 용액에서는 아미노산인 글라이신(C2H5NO2), 알라닌(C3H7NO2), 히스티딘(C6H9N3O2), 프롤린(C5H9NO2), 발린(C5H11NO2)이 검출되었고, 기존 Miller 1953과 Parker et al. 2014의 결과와 비교하였다. 전기방전에서는 C2 Swan Band 와 CN emission을 발견하였다. 이 두 방출선들은 혜성에서도 일반적으로 보여지는 방출선들이다.

  • PDF

Energy Spectrum Analysis between Single and Dual Energy Source X-ray Imaging for PCB Non-destructive Test (PCB 비파괴 검사에 있어서 단일 에너지 소스와 이중 에너지 소스의 영상비교를 위한 엑스선 스펙트럼 분석)

  • Kim, Myungsoo;Kim, Giyoon;Lee, Minju;Kang, Dong-uk;Lee, Daehee;Park, Kyeongjin;Kim, Yewon;Kim, Chankyu;Kim, Hyoungtaek;Cho, Gyuseong
    • Journal of Radiation Industry
    • /
    • v.9 no.3
    • /
    • pp.153-159
    • /
    • 2015
  • Reliability of printed circuit board (PCB), which is based on high integrated circuit technology, is having been important because of development of electric and self-driving car. In order to answer these demand, automated X-ray inspection (AXI) is best solution for PCB non-destructive test. PCB is consist of plastic, copper, and, lead, which have low to high Z-number materials. By using dual energy X-ray imaging, these materials can be inspected accurately and efficiently. Dual energy X-ray imaging, that have the advantage of separating materials, however, need some solution such as energy separation method and enhancing efficiency because PCB has materials that has wide range of Z-number. In this work, we found out several things by analysis of X-ray energy spectrum. Separating between lead and combination of plastic and copper is only possible with energy range not dose. On the other hand, separating between plastic and copper is only with dose not energy range. Moreover the copper filter of high energy part of dual X-ray imaging and 50 kVp of low energy part of dual X-ray imaging is best for efficiency.

A Web application vulnerability scoring framework by categorizing vulnerabilities according to privilege acquisition (취약점의 권한 획득 정도에 따른 웹 애플리케이션 취약성 수치화 프레임워크)

  • Cho, Sung-Young;Yoo, Su-Yeon;Jeon, Sang-Hun;Lim, Chae-Ho;Kim, Se-Hun
    • Journal of the Korea Institute of Information Security & Cryptology
    • /
    • v.22 no.3
    • /
    • pp.601-613
    • /
    • 2012
  • It is required to design and implement secure web applications to provide safe web services. For this reason, there are several scoring frameworks to measure vulnerabilities in web applications. However, these frameworks do not classify according to seriousness of vulnerability because these frameworks simply accumulate score of individual factors in a vulnerability. We rate and score vulnerabilities according to probability of privilege acquisition so that we can prioritize vulnerabilities found in web applications. Also, our proposed framework provides a method to score all web applications provided by an organization so that which web applications is the worst secure and should be treated first. Our scoring framework is applied to the data which lists vulnerabilities in web applications found by a web scanner based on crawling, and we show the importance of categorizing vulnerabilities according to privilege acquisition.

A Study on Establishment of Evaluation Criteria for Anti-Virus Performance Test (Anti-Virus 성능 시험을 위한 평가 기준 수립 연구)

  • Jeongho Lee;Kangsik Shin;Youngrak Ryu;Dong-Jae Jung;Ho-Mook Cho
    • Journal of the Korea Institute of Information Security & Cryptology
    • /
    • v.33 no.5
    • /
    • pp.847-859
    • /
    • 2023
  • With the recent increase in damage caused by malcious codes using software vulnerabilities in Korea, it is essential to install anti-virus to prevent malicious codes, However, it is not easy for general users to know which anti-virus product has good performance or whether it is suitable for their environment. There are many institutions that provide information on anti-virus performance outside of korea, and these institutions have established their own test environments and test evaluation items, but they do not disclose detailed test environment information, detailed test evaluation items, and results. In addition, existing quality evaluation studies are not suitable for the evaluating the latest anti-virus products because there are many evaluation criteria that do not meet anti-virus product evaluation. Therefore, this paper establishes detailed anti-virus evaluation metrics suitable for the latest anti-virus evaluation and applies them to 9 domestic and foreign anti-virus products to verify the functions and performance of anti-viruses.