• Journal of the Korean Magnetic Resonance Society
• /
• v.6 no.1
• /
• pp.38-44
• /
• 2002

60% Pt on Vulcan XC-72 with similar Pt sizes to fuel cell grade Pt black was investigated by $\^$13/C nuclear magnetic resonance spectroscopy (NMR), cyclic voltammery (CV), transmission electron microscopy (TEM). Experiments were carried out on electrochemically cleaned samples as well as as-received. The TEM and CV results showed that the average particle sizes were changed by cleaning. However, the chemical shift （$\delta$$\_$G/） of $\^$13/C of $\^$13/CO absorbed on Pt surfaces did not show any appreciable variation with particle size change as did in Pt black. These results indicate that a combination of different analytic techniques is essential to understand the properties of the metal particle catalysts and that the presence of carbon black support strongly influences the NMR data, probably through metal-support interaction.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.1
• /
• pp.67.1-67.1
• /
• 2012

Shocks are evolved when the relativistic jets in active galactic nuclei (AGNs), black hole binaries, supernova remnants (SNR) and gamma-ray bursts (GRBs) interact with the surrounding medium. The high energy particles are believed to be accelerated by the diffusive shock acceleration and the strong magnetic field is generated by Weibel instability in the shock. When ultrarelativistic electrons with strong magnetic field cool by the synchrotron emission, the radiation is observed in gamma-ray burst and the near-equipartitioned magnetic field in the external shock delays the afterglow emission. In this paper, we performed the 3D particle-in-cell (PIC) simulations to understand the characteristics of these relativistic shock and particle acceleration. Forward and reverse shocks are shaped while the unmagnetized injecting jet interacts with the unmagnetized ambient medium. Both upstream and downstream become thermalized and the particle accelerations are shown in each transition region of the shock structures.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.792-793
• /
• 2006

In the paper, the influence of different particle size $D:D>125{\mu}m$, $D<50{\mu}m$ and between on magnetic properties of a standardized dielectromagnetic is presented. The tests were taken at frequencies of between 50Hz, and 500Hz. Presented in the paper results provide important materials property data to allow the selection of the most appropriate dielectromagnetic particle size for different applications.

• ETRI Journal
• /
• v.39 no.6
• /
• pp.841-850
• /
• 2017

We investigate neural network image reconstruction for magnetic particle imaging. The network performance strongly depends on the convolution effects of the spectrum input data. The larger convolution effect appearing at a relatively smaller nanoparticle size obstructs the network training. The trained single-layer network reveals the weighting matrix consisting of a basis vector in the form of Chebyshev polynomials of the second kind. The weighting matrix corresponds to an inverse system matrix, where an incoherency of basis vectors due to low convolution effects, as well as a nonlinear activation function, plays a key role in retrieving the matrix elements. Test images are well reconstructed through trained networks having an inverse kernel matrix. We also confirm that a multi-layer network with one hidden layer improves the performance. Based on the results, a neural network architecture overcoming the low incoherence of the inverse kernel through the classification property is expected to become a better tool for image reconstruction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.07a
• /
• pp.426-427
• /
• 2005

This research describes a new constructing method of multifunctional biosensor using many kinds of biomaterials. A metal particle and an array was fabricated by photolithographic. Biomaterials were immobilized on the metal particle. The array and the particles were mixed in a buffer solution, and were arranged by magnetic force interaction and self-assembly. A quarter of total Ni dots were covered by the particles. The binding direction of the particles was controllable, and condition of particles was almost with Au surface on top. The particles were successfully arranged on the array. The biomaterial activities were detected by chemiluminescence and electrochemical methods.

• Progress in Superconductivity and Cryogenics
• /
• v.23 no.3
• /
• pp.26-31
• /
• 2021

Advanced classification of Cs contaminated soil by using a magnetic force-assisted selection pipe was investigated. A selection pipe is a device that sort particles depending on their particle size, based on the relationship between buoyancy, drag, and gravity force acting on the particles. Radioactive cesium is concentrated in small-particle size soil components with a large specific surface area. Hence, the volume of the Cs contaminated soil can be reduced by recycling the large-particle size soil components with low radioactive concentration. One of the problems of the selection pipe was that the radioactive concentration of the stayed soil in the selection pipe exceeds 8000 Bq/kg, which is the standard value of recycling of Cs contaminated soil, due to low classification accuracy. In this study, magnetic fields were applied to the lab-scale selection pipe from upper side to improve the classification accuracy and to reduce the radioactive concentration of the stayed soil.

• 한국초전도학회:학술대회논문집
• /
• v.16
• /
• pp.12-12
• /
• 2006

• Resources Recycling
• /
• v.11 no.5
• /
• pp.7-10
• /
• 2002

Iron nitride magnetic fluid was oxidized by exposing it to the air under normal atmospheric conditions. After exposure of 3.2 hours, the relative saturation magnetization of the iron nitride magnetic fluid is less than 0.4 compared to the value of the unexposed sample, and it is nearly zero after exposure for 1008 hours. The structure of the oxidized iron nitride is considered to be a non-magnetic hematites. The thickness of the oxidation layers of the iron-nitride particles are nearly the same, about 3 nm, regardless of the different particle sizes.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.49 no.6
• /
• pp.87-92
• /
• 2007

Strain-stress behavior of soil is of importance in dealing with geo-techniques which relate to bearing capacity, slope stability, earth pressure and many geo-technical problems. So understanding mechanism of the behavior and reinforcing soil to the required state has been an issue for many years. This paper presents the possibility of magnetic force in enhancing shear strength. To analyze the reinforcing effect, triaxial compression tests were performed on two sets of steel-sand mixtures, one of which is influenced by permanent magnet, NdFeB. With magnetic force under 50 kPa confining pressure, maximum shear strengths increased according to steel percentages but under 100 kPa, no significant changes in maximum shear strengths occurred. Therefore the analysis by Mohr's circles indicates that magnetic force converts the shearing characteristics of sand into those of clay.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.791-794
• /
• 2008

MRE(Magneto-rheological Elastomer) is a material which shows reversible and various modulus in magnetic field. Comparing to conventional rubber vibration isolator, MREs are able to absorb broader frequency range of vibration. These characteristic phenomena result from the orientation of magnetic particle (i.e., chain-like formation) in rubber matrix. In this study, NR was used as a matrix in order to manufacture MREs. Magnetic reactive powder(MRP), having rapid magnetic reaction, was selected as a magnetic particle to give magnetic field reactive modulus. The mechanical properties of manufactured MREs were measured without the application of magnetic field. The results showed that the tensile property and resilience were decreased while the hardness was increased with the addition of CIP. The analysis of MR effect was carried out by FFT analyzer with various magnetic flux. As the addition of MRP and magnetic flux increased, increment of MR effect was observed.