• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
• /
• 1991.11a
• /
• pp.105-133
• /
• 1991

본 논문에서는 임의의 이진 난수발생기의 source가 $BMS_{p}$ 이거나 M-memory를 갖는 마르코프연쇄로 모델화 되었을 경우에 비트당 entropy와 관련이 있는 새로운 randomness에 관한 통계적 검정법을 제안한다. 기존에 알려진 이진 난수발생기의 randomness검정법이 0또는 1의 분포의 편향성(bias)이나 연속된 비트간의 상관성(correlation)중의 한 종류만의 non-randomness를 추적해낼 수 있는 반면에 새로운 검정법은 위의 두가지 검정을 통과하였을 때 암호학적으로 중요한 측도인 비트당 entropy 를 측정하여 암호학적인 약점을 검정할 수 있다. 또한 대칭(비밀키) 암호시스템의 통계적 결점을 바탕으로 하여 키를 찾는 공격자의 최적 전략( optimal strategy)문제를 분석하여 이 최적 전략이 이진 수열의 비트당 entropy와 밀접한 관계가 있음을 보이고 이 비트당 entropy와 관련이 있는 새로운 통계량을 도입하여 이진 난수 발생기의 source의 이진수열이 다음 3가지 경우, 즉, i.i.d. symmetric인 경우, $BMS_{p}$ 인 경우, M-memory를 갖는 마르코프연쇄인 경우의 각각에 대하여 특성을 조사하고 새로운 통계량의 평균과 분산을 구한다. 이때 구한 새로운 통계량은 잘 알려진 중심 극한 정리에 의하여 근사적으로 정규분포를 따르므로 위의 평균과 분산을 이용하여 스트림 암호시스템에서 구성요소로 많이 사용되는 몇 몇 간단한 이진 난수 발생기에 적용하여 통계적 검정을 실시함으로써 entropy 관점의 검정법이 새로운 randomness 검정법으로 타당함을 보인다.

• Journal of the Korean Electrochemical Society
• /
• v.15 no.3
• /
• pp.198-205
• /
• 2012

Carbon-supported manganese oxide composite were fabricated as an air cathode material for Li-air batteries by hydrothermal method. The composite materials of carbon and manganese oxide were investigated by the implementation of X-ray diffraction, FE-SEM and BET surface area measurer. The manganese oxide synthesized at $170^{\circ}C$ for 12 h has a rod like shape morphology with 40-50 nm long in size. A Lithium-air battery with coin type, of which electrodes are composed of cathode composite materials synthesized $170^{\circ}C$-12 h and lithium metal anode, reveals its first discharge capacity of 3,852 mAh/g and four discharge-charge cycles.

• The Journal of the Korea Contents Association
• /
• v.6 no.4
• /
• pp.63-68
• /
• 2006

For the almost co티am convergent series $S_n$ of independent random variables, by investigating the limiting behavior of the tail series, $T_n=S-S_{n-1}=\sum_{i=n}^{\infty}X_i$, the rate of convergence of the series $S_n$ to a random variable S is studied in this paper. More specifically, the equivalence between the tail series weak law of large numbers and a limit law is established for a quasi-monotone decreasing sequence, thereby extending a result of Previous work to the wider class of the norming constants.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.672-672
• /
• 2013

본 연구에서는 수열합성법을 기반으로 한 3차원 ZnO 나노구조의 합성을 통해 효율적인 양자점 감응형 태양전지로의 응용을 하고 그 특성을 평가하였다. 기존의 1차원 ZnO 나노구조의 경우 높은 전자이동도와 구조적으로 얻을 수 있는 방향성 있는 전자의 효율적인 전달을 통해 효과적인 광전극으로 많은 관심을 받아왔다. 하지만 나노파티클 기반의 필름에 비해 표면적이 크게 떨어지기 때문에 효과적인 흡광이 어렵다는 단점이 존재하여 높은 효율특성을 내지는 못하였다. 본 연구에서는 이러한 단점을 극복하면서 기존 ZnO 나노선의 장점을 극대화 하기 위해 성장시킨 ZnO 나노선 위에 추가적으로 가지를 형성하여 표면적 향상과 효과적인 전자전달 특성을 얻고자 하였다. 3차원 ZnO 나노구조는citrate 계열의 capping agent의 첨가를 통한 수열 합성법을 통해 1차원의 ZnO 나노선 위에 nanosheet 형식의 가지를 형성하였고 이는 빛의 효과적인 산란특성 및 표면적 향상을 통한 CdS, CdSe의 양자점 증착량을 증가시키는 효과를 얻을 수 있었다. 이러한 태양전지의 소자 특성은 SEM, TEM을 통한 구조 특성평가 및 DRS, J-V curve 및 IPCE를 통한 광학적 특성평가를 통해 확인하였다.

• Journal of Educational Research in Mathematics
• /
• v.26 no.2
• /
• pp.159-172
• /
• 2016

This study examines the approach of introduction of the real numbers through the infinite decimal, which is suggested by Lee Ji-Hyun(2014; 2015) in the aspect of the overcoming the double discontinuity, and analyses Li(2011), which is the mathematical background of the foregoing Lee's. Also, this study compares these construction methods given by Lee and Li with the traditional method using the nested intervals. As a result of analysis, this study shows that Lee Ji-Hyun(2014; 2015) and Li(2011) face the risk of the circulation logic in making the infinite decimal corresponding each point on the geometrical line, and need the steps not using the 'limit to a real number' in order to compensate the mathematical and educational defect. Accordingly, this study raises the opinion that the traditional method of defining the infinite decimal as a sequence by using the geometrical nested intervals axiom would be a appropriate supplementation.

• Journal of the Korean Data and Information Science Society
• /
• v.20 no.5
• /
• pp.779-786
• /
• 2009

Lotto is one of the most popular lottery games in the world. In korea the lotto considers numbers 1, 2,..., 45 from which 6 numbers are drawn randomly, without replacement. The profits from the lotto supports social welfare. However, there has been a suspicion that the choice of the winning numbers might not be random. In this study, we applied the randomness test developed by Coronel-Brizio et al. (2008) to the historical korean lotto data to see if the drawing process is random. The result of our study shows that the process was random during two periods under the management of different business companies and of price changes, respectively.

• Fire Science and Engineering
• /
• v.33 no.4
• /
• pp.59-69
• /
• 2019

The present article relates to an experimental study on fire risks due to overcharge and external heat of ESS lithium battery. According to the experimental results of overcharge, ignition occurred as combustible gas and smoke was slowly increased after occurrence of venting, and an explosive combustion form accompanied by flame eruption and sparks was displayed as charged energy is rapidly discharged in an instant. On the other hand, according to the experimental results of external heat, as a tremendous amount of combustible gas and smoke was ignited following being discharged after occurrence of vent, the charged energy itself was rapidly reduced due to the discharged energy so that a passive combustion form was observed when compared with overcharge after occurrence of flames. According the analysis results of fire damage characteristics, differences between external heat (External flame) could be found through visual and X-ray inspections. Namely, while inside electrode plate was completely destroyed and perforation of the electrode plate was observed in the case of overcharge, fire damage of the electrode plate was not severe maintaining the form in the case of external heat.

• Proceedings of the IEEK Conference
• /
• 2007.07a
• /
• pp.71-72
• /
• 2007

대역 제한된 DS/SS 시스템의 상관 함수는 최고 값이 나타나는 시점과 함께 이른 또는 늦은 상관시간 옵셋 영역에서 극소 또는 극대로 나타나는 시점을 특징점으로 갖는다. 이 가운데 이른 상관시간옵셋 영역의 상관 함수는 다중경로 신호에 의해 덜 왜곡되기 때문에 이 영역의 상관 함수를 이용해 부호 동기를 추적하여 유지할 수 있다면 EL-DLL (delay lock loop with early minus late discriminator) 보다 추적편이를 줄일 수 있다. 본 논문에 이런 특성을 이용하는 추적편이 완화 기법을 제안하고, 모의실험을 통해 성능을 알아본다.

• Korean Chemical Engineering Research
• /
• v.48 no.3
• /
• pp.283-291
• /
• 2010

In this review, the studies on the electrochemical properties of $TiO_2$ nanotube as an anode material of lithium-ion battery, which was prepared by an alkaline hydrothermal reaction and anneling process, were investigated andanalyzed in terms of charge-dischage characteristics. Up to date, a maximum discharge capacity of $338mAh\;g^{-1}$(x=1.01) was achieved by the nanotube with $TiO_2(B)$ phase, whereas the theoretical capacity of $TiO_2$ anode was $335mAh\;g^{-1}$(x=1) in the basis of $Li_xTiO_2$ as a product of electrochemical reaction between $TiO_2$ and lithium. This was due to fast lithium transport by a shortened diffusion path provided by controlling the nanostructure of $TiO_2$, because the self-diffusion of lithium was slow in a basis of its activation energy as 0.48 eV. Due to an excellent ion storage capabilities in both the surface and the bulk phase, the $TiO_2$ nanotube could be a promising active material as both an anode of lithium-ion battery and an electrode of capacitor with high-rate performances.

• Korean Chemical Engineering Research
• /
• v.50 no.1
• /
• pp.25-29
• /
• 2012

$TiO_2$ nanotubes are prepared from rutile prticles via an alkaline hydrothermal synthesis and the consequent heat treatment at $300{\sim}500^{\circ}C$. The physical and electrochemical properties of the $TiO_2$ nanotubes are characterized for use as a anode material of rechargeable lithium battery. In particular, the microscale dusts as an impurity component occurred in the purification step after the hydrothermal reaction are completely removed to yield $TiO_2$ nanotube with a higher specific surface area and more obvious crystalline phases. As the annealing temperature increases, the specific surface area is slightly decreased due to some aggregation between the isotropically dispersed nanotubes. Highest initial discharge capacity of 250 mAh $g^{-1}$ is achieved for the $TiO_2$ nanotube annealed at $300^{\circ}C$, whereas the $400^{\circ}C$ $TiO_2$ nanotube shows the superior cycle performance and high-rate capability.