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초고속 우주먼지 충돌 모사를 위한 레이저 유도 추진 시스템에 대한 연구
유현주,백원계,Vitalij Fedotov,여재익 한국항공우주학회 2012 한국항공우주학회 학술발표회 논문집 Vol.2012 No.11
오늘날 인공위성 및 우주선 발사가 과거에 비해 많아짐에 따라 우주 먼지와의 충돌이 기하급수적으로 늘어나고 있다. 그 결과 오늘날 약 1조 개가 넘는 우주먼지가 지구 주위를 움직이며 인공위성과 우주선에 큰 위협 및 손상을 입히고 있다. 따라서 본 연구에서는 우주먼지 충돌 실험을 모사하기 위한 토대로서 레이저를 이용한 입자 가속 기술의 개발을 목표로 하였다. 기존에 사용된 복잡한 다중코팅 대신 단순한 검정 페인트 코팅을 사용하여 순수한 물질일 때 보다 약 1.5~2배 정도의 속도 향상을 유도하였다. 그리고 금속박을 파편화하여 더 미세하고 빠른 속도를 내는 우주먼지를 재현하였다. 그 결과 1 J의 Nd:YAG 레이저 빔을 이용하여 최대 2.2 ㎞/s의 우주먼지를 모사하였고 이는 정지궤도에서 인공위성과 우주 먼지간의 충돌 속도에 근접한 속도이다. Nowadays, space debris are increasing at astronomical rates due to the impact caused by frequent launching of satellites and spacecraft, following the development of space technology. In consequence, more than trillion space debris are circling around the earth presenting potential threat to satellites and spacecrafts. In this research, we try to develop laser particle acceleration technology to simulate space debris impact. The complex multi-coating suggested in the existing studies is replaced with simple black paint coating, which enhances velocity from 1.5 to 2 times, compared with the case of pure material. Also, simulating space debris is accomplished through employing thinner metal foils which can be broken into smaller pieces. Nd:YAG laser beam with 1 J energy is proved to be capable of simulating space debris at velocity of 2.2 ㎞/s. This is approximately the same as the case of the impact between satellites in the geostationary orbit and space debris.
Evaluation of the true-strength characteristics for isotropic materials using ring tensile test
Frolov, A.S.,Fedotov, I.V.,Gurovich, B.A. Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.7
The paper proposes a technique for reconstructing the true hardening curve of isotropic materials from ring tensile tests. Neutron irradiated 42XNM alloy tensile properties were investigated. The calculation of the true hardening curve for tensile and compression tests of standard cylindrical samples was performed at the first step. After that, the FEM-model was developed and validated using the ring tension and compression tests (with the hardening curve defined in step 1). Finally, the true hardening curve was calculated by selecting the FEM-model parameters and its validation by ring sample tests in different states using an iterative method. For these samples, experimental and calculated gauge length values were obtained, and the corresponding material's constants were estimated.
Gurovich, B.A.,Frolov, A.S.,Fedotov, I.V. Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.6
Chromium-nickel alloy 42XNM (XHM-1, Bochvalloy) is considered as a promising material for future generations of nuclear reactors, primarily as a material for the fuel elements shells in the development of accident tolerant fuel. However, as with most nickel-based alloys, 42ХNМ is characterized by a sharp decrease in plastic properties in the temperature range of (500-900)℃. This effect is enhanced by neutron irradiation. Preliminary tests of ring samples of 42XNM alloy (after irradiation as a part of the VVER-1000 control system) in the temperature range of ductility failure showed that the standard technique for processing tensile diagrams does not allow to evaluate the plastic properties correctly at low strains. Therefore, in this work, the alternative method for testing ring samples from materials with low plastic characteristics was developed. It was shown that the minimum value of the permanent strain of the irradiated 42XNM alloy in the temperature range of (500-1100)℃, determined by the alternative method, was ~1.6% at 750 ℃.
레민후이,황란미,드미트리 페도토프,Le, Minhhuy,Hwang, Lan-mi,Fedotov, Dmitry 한국정보통신학회 2019 한국정보통신학회논문지 Vol.23 No.1
UWB(Ultra-wideband)는 송신 안테나에서 UWB 대역을 송신한 신호를 수신 안테나를 통해 받은 신호를 가지고 목표물을 판단하는 고해상도 근거리 초광대역 레이더로 비접촉으로 사람의 호흡 및 심박을 감지할 수 있고, 환경에 영향을 받지 않아 최근 활용도가 높아지고 있다. 본 논문에서는 UWB 레이더 신호를 이용하여 사람의 호흡과 심박수를 감지하는 알고리즘을 구현한다. 인체에서부터 반사되어 들어온 레이더 신호를 메디안 필터, 칼만 필터, 밴드 패스필터 등을 이용하여 처리한다. 또한 호흡수와 심박수를 추출하기 위하여 CZT를 이용한다. 비교하는 심박 데이터로는 ECG(Electrocardiogram)를 사용하였으며, 약 98% 이상 일치함을 확인하였다. Ultra Wideband (UWB) Radar is a high-resolution radar for short distance detection which uses signals transmitted and received by each antennas in order to detect a target. It is possible to detect the respiration and heartbeat of a person without contact It is getting more and more often utilized since it is not affected by physical environment. In this paper, we implement an algorithm to detect human respiration and heartbeat rate using UWB radar signal. We process radar signals reflected from human body using Median filter, Kalman filter, Band Pass filter and so on. We also use CZT to extract breathing and heart rate. ECG (Electrocardiogram) was used for comparison of heartbeat data and we confirm that each data of ECG and UWB Radar were more than 98% identical each other.
He, Maoshuai,Wang, Xiao,Zhang, Lili,Wu, Qianru,Song, Xiaojie,Chernov, Alexander I.,Fedotov, Pavel V.,Obraztsova, Elena D.,Sainio, Jani,Jiang, Hua,Cui, Hongzhi,Ding, Feng,Kauppinen, Esko Elsevier 2018 Carbon Vol.128 No.-
<P><B>Abstract</B></P> <P>The suitability of the NiMgO catalyst as a catalyst in chiral-selective growth of single-walled carbon nanotubes (SWNTs) by chemical vapor deposition has been assessed. It reveals that catalyst calcination temperature plays an important role in affecting the catalyst performances. Using CO as the carbon precursor and a chemical vapor deposition reaction temperature of 600 °C, NiMgO pre-calcined at 600 °C demonstrates the best performances in catalyzing the growth of SWNTs with predominant (6, 5) species. Systematic characterizations on catalysts calcinated at different temperatures indicate that Ni<SUP>2+</SUP> ions diffuse towards the interior of MgO matrix upon annealing. DFT-based calculations reveal that the binding energy between Ni<SUP>2+</SUP> and adjacent Ni(0) is larger than that between Mg<SUP>2+</SUP> and Ni (0), while Ni<SUP>2+</SUP> situated deep inside MgO has weak interactions with surface Ni atoms. This work highlights the importance of subsurface Ni<SUP>2+</SUP> in anchoring reduced surface Ni atom, which inhibits the aggregation of Ni particles and therefore, facilitates the growth of SWNTs with a narrow chirality distribution.</P> <P><B>Graphical abstract</B></P> <P>A Ni-incorporated MgO catalyst was developed for predominant synthesis of (6, 5) single walled carbon nanotubes. Density functional theory-based calculations revealed that the unreduced subsurface Ni stabilized reduced Ni atoms on the surface, facilitating the growth of carbon nanotubes with a narrow chirality distribution.</P> <P>[DISPLAY OMISSION]</P>
A storage ring experiment to detect a proton electric dipole moment
Anastassopoulos, V.,Andrianov, S.,Baartman, R.,Baessler, S.,Bai, M.,Benante, J.,Berz, M.,Blaskiewicz, M.,Bowcock, T.,Brown, K.,Casey, B.,Conte, M.,Crnkovic, J. D.,D’Imperio, N.,Fanourakis, G.,Fedotov, American Institute of Physics 2016 Review of scientific instruments Vol.87 No.11