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MgB<sub>2</sub> 초전도체의 임계특성에 대한 Fe 입자 크기의 영향
정현덕,이동건,류성수,박해웅,김찬중,전병혁,Jeong, Hyeondeok,Lee, Dong-Gun,Ryu, Sung-Soo,Park, Hai-Woong,Kim, Chan-Joong,Jun, Byung-Hyuk 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.5
This study demonstrates the effect of addition of Fe particles of different sizes on the critical properties of the superconductor $MgB_2$. Bulk $MgB_2$ is synthesized by ball milling Mg and B powders with Fe particles at $900^{\circ}C$. When Fe particles with size less than $10{\mu}m$ are added in $MgB_2$, they easily react with B and form the FeB phase, resulting in a reduction in the amount of the $MgB_2$ phase and deterioration of the crystallinity. Accordingly, both the critical temperature and the critical current density are significantly reduced. On the other hand, when larger Fe particles are added, the $Fe_2B$ phase forms instead of FeB due to the lower reactivity of Fe toward B. Accordingly, negligible loss of B occurs, and the critical properties are found to be similar to those of the intact $MgB_2$.
有機態 燐酸과 칼슘의 葉面撒布 및 灌注處里가 배(Pyrus pyrifolia N.) 樹體生育과 果實 品質에 미치는 影響
鄭賢德,李相炫,金月洙 전남대학교 농업과학기술연구소 2000 農業科學技術硏究 Vol.35 No.-
To establish the system of orchard fertilization the study was to carried out by foliar spray and fertigation with organic calcium and phosphate in the five year old 'Youngsan' pear trees (Pyrus pyrifolia) planted in Kochang, Chonbuk. The five hundred times diluted solutions of organic calcium and phosphate were sprayed on the surface of pear leaves at intervals of 7 to 10 days from June 1 to August 31. Also five hundred times diluted solutions of organic calcium and phosphate were fertigated under the canopy at intervals of 7 to 10 days from June 1 to August 31. The calciums treatments with foliar spray as well as feritgation increase leaf size on twigs and shoots. Meanwhile organic phosphate treatment showed smaller leaf size in shoots and large on twigs. Calcium content of leaves was higher by the treatment of foliar spray and fertigation. Phosphate content of leaves was much higher by the treatment of organic phosphate. In inorganic substance of fruit peel tissues, calcium content was high by the treatment of organic calcium + phosphate. On the other hand phosphate content in flesh of fruit was high by the treatment of organic phosphate. Fruit weight and firmness were increased by the treatment of organic calcium. Soluble solid was high by the treatment of organic phosphate.
MgB<sub>4</sub>와 Mg 분말을 원료로 사용하여 고상반응법으로 제조한 MgB<sub>2</sub> 초전도체의 상생성과 초전도 특성
정현덕,김찬중,전병혁,김설향,박해웅,Jeong, Hyeondeok,Kim, Chan-Joong,Jun, Byung-Hyuk,Kim, Seolhyang,Park, Hai-Woong 한국분말야금학회 2015 한국분말재료학회지 (KPMI) Vol.22 No.5
$MgB_2$ bulk superconductors are synthesized by the solid state reaction of ($MgB_4$+xMg) precursors with excessive Mg compositions (x=1.0, 1.4, 2.0 and 2.4). The $MgB_4$ precursors are synthesized using (Mg+B) powders. The secondary phases ($MgB_4$ and MgO) present in the synthesized $MgB_4$ are removed by $HNO_3$ leaching. It is found that the formation reaction of $MgB_2$ is accelerated when Mg excessive compositions are used. The magnetization curves of $Mg_1+_xB_2$ samples show that the transition from the normal state to the superconducting state of the Mg excessive samples with x=0.5 and x=0.7 are sharper than that of $MgB_2$. The highest $J_c-B$ curve at 5 K and 20 K is achieved for x=0.5. Further addition of Mg decreases the $J_c$ owing to the formation of more pores in the $MgB_2$ matrix and smaller volume fraction of $MgB_2$.
볼밀 공정 중 점도와 음향 데이터의 실시간 수집 및 상관관계 분석
정현덕,김영범,류성수,김세기,Jeong, Hyeondeok,Kim, Young-Beom,Ryu, Sung-Soo,Kim, Seiki 한국분말재료학회 (*구 분말야금학회) 2020 한국분말재료학회지 (KPMI) Vol.27 No.6
In this study, acoustic and viscosity data are collected in real time during the ball milling process and analyzed for correlation. After fast Fourier transformation (FFT) of the acoustic data, changes in the signals are observed as a function of the milling time. To analyze this quantitatively, the frequency band is divided into 1 kHz ranges to obtain an integral value. The integrated values in the 2-3 kHz range of the frequency band decrease linearly, confirming that they have a high correlation with changes in viscosity. The experiment is repeated four times to ensure the reproducibility of the data. The results of this study show that it is possible to estimate changes in slurry properties, such as viscosity and particle size, during the ball milling process using an acoustic signal.
Windows OS 기반 악성코드 탐지를 위한 Volatility 3 Plug-in 개발 연구
정현덕,김도현 한국디지털포렌식학회 2024 디지털 포렌식 연구 Vol.18 No.2
메모리 포렌식은 시스템 메모리에서 발생한 사건과 관련된 데이터를 수집, 분석하는 과정이다. 이는 특히 악성코드 탐지, 시스템 침해 분석, 루트킷과 같은 은닉된 악성 요소 탐지에 있어 매우 중요한 역할을 한다. 전통적인 디스크 기반 분석과는 달리, 메모리 포렌식은 휘발성 데이터를 포함한 시스템의 실시간 상태를 분석할 수 있어 더욱 정확한 침해 원인 분석 및 대응이 가능하다. 본 논문은 메모리 포렌식 도구인 Volatility 3을 활용해 윈도우 은닉 악성코드 탐지 연구를 수행했고 그 결과를 기반으로 하여 숨겨진 프로세스(루트킷) 등을 탐지할 수 있는 Volatility 3의 Plug-in인 hiddenprocess를 개발했다. 이것을 사용하여 권한 상승 취약점을 이용한 악성 프로세스와 Cronos-Rookit을 통해 은닉된 프로세스를 성공적으로 탐지하는 것을 테스트를 통해 확인하였다. hiddenprocess는 여러 가지 방법으로 조회된 PID를 서로 비교하여 탐지 여부를 True/false로 출력하고 실행된 각 프로세스가 가지고 있는 권한을 조회하는 기능을 가지고 있다. hiddenprocess를 이용하여 침해사고 시스템을 분석하면 더욱 직관적으로 의심 프로세스를 판별하는 데 도움을 줄 수 있을 것으로 기대한다. Memory forensics involves the collection and analysis of data related to incidents occurring within system memory. This is particularly important for detecting malware, analyzing system intrusions, and uncovering hidden malicious elements like rootkits. Unlike traditional disk-based analysis, memory forensics allows for the examination of the system's real-time state, including volatile data, leading to more accurate identification and response to security breaches. This paper explores the use of the memory forensics tool Volatility 3 to detect hidden malware on Windows systems. Based on the findings, we developed a plugin for Volatility 3 called "hiddenprocess," designed to detect hidden processes (rootkits). Through testing, we successfully identified malicious processes exploiting privilege escalation vulnerabilities and processes hidden by the Cronos-Rootkit using this plugin. The hiddenprocess plugin compares PIDs retrieved through various methods to output a True/False detection status and has a feature to check the privileges of each running process. Utilizing hiddenprocess to analyze compromised systems is expected to aid in more intuitively identifying suspicious processes.
구상 페놀수지 분말과 푸르프릴 알코올로부터 주형성형에 의한 매크로 다공성 카본 폼의 제조
정현덕,김세기,Jeong, Hyeondeok,Kim, Seiki 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.6
Macro-porous carbon foams are fabricated using cured spherical phenolic resin particles as a matrix and furfuryl alcohol as a binder through a simple casting molding. Different sizes of the phenolic resin particles from 100-450 ㎛ are used to control the pore size and structure. Ethylene glycol is additionally added as a pore-forming agent and oxalic acid is used as an initiator for polymerization of furfuryl alcohol. The polymerization is performed in two steps; at 80℃ and 200℃ in an ambient atmosphere. The carbonization of the cured body is performed under Nitrogen gas flow (0.8 L/min) at 800℃ for 1 h. Shrinkage rate and residual carbon content are measured by size and weight change after carbonization. The pore structures are observed by both electron and optical microscope and compared with the porosity results achieved by the Archimedes method. The porosity is similar regardless of the size of the phenolic resin particles. On the other hand, the pore size increases in proportion to the phenol resin size, which indicates that the pore structure can be controlled by changing the raw material particle size.