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Neural Network Image Reconstruction for Magnetic Particle Imaging
채병규 한국전자통신연구원 2017 ETRI Journal Vol.39 No.6
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.
Sparse-View CT Image Recovery Using Two-Step Iterative Shrinkage-Thresholding Algorithm
채병규,이수열 한국전자통신연구원 2015 ETRI Journal Vol.37 No.6
We investigate an image recovery method for sparse-view computed tomography (CT) using an iterative shrinkage algorithm based on a second-order approach. The two-step iterative shrinkage-thresholding (TwIST) algorithm including a total variation regularization technique is elucidated to be more robust than other first-order methods; it enables a perfect restoration of an original image even if given only a few projection views of a parallel-beam geometry. We find that the incoherency of a projection system matrix in CT geometry sufficiently satisfies the exact reconstruction principle even when the matrix itself has a large condition number. Image reconstruction from fan-beam CT can be well carried out, but the retrieval performance is very low when compared to a parallel-beam geometry. This is considered to be due to the matrix complexity of the projection geometry. We also evaluate the image retrieval performance of the TwIST algorithm using measured projection data.
박민식,채병규,김현의,한준구,김휘,박정희,문경애,김진웅 한국전자통신연구원 2014 ETRI Journal Vol.36 No.2
A holographic display system with a 22-inch LCD panelis developed to provide a wide viewing angle and largeholographic 3D image. It is realized by steering a narrowviewing window resulting from a very large pixel pitchcompared to the wave length of the laser light. Point lightsources and a lens array make it possible to arbitrarilycontrol the position of the viewing window for a movingobserver. The holographic display provides both eyes ofthe observer with a holographic 3D image using twovertically placed LCD panels and a beam splitter tosupport the holographic stereogram.
이지현,채병규,김중정,이선영,박찬경 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.1
Dopant control becomes more difficult and critical as silicon devices becomesmaller. We observed the dopant distribution in a thermally annealed polysilicongate using Transmission Electron Microscopy (TEM) and Atom probe tomography(APT). Phosphorus was doped at the silicon-nitride-diffusion-barrier-layer-coveredpolycrystalline silicon gate. Carbon also incorporated at the gate for the enhancementof operation uniformity. The impurity distribution was observed using atom probetomography. The carbon atoms had segregated at grain boundaries and suppressedsilicon grain growth. Phosphorus atoms, on the other hand, tended to pile-up at theinterface. A 1-nm-thick diffusion barrier effectively blocked P atom out-diffusion.
High Temperature Pulsed Plasma Flux 응용 금속 표면경화 공정기술
권식철,채병규,이건환,백운승 대한용접접합학회 2001 대한용접·접합학회지 Vol.19 No.4
The new development of the surface hardening technology has been attracted to machine designer and materials scientist in the view point of improvement in the lifetime and performance of the machine. The heat-treatment process has been a well-known technology to make harden the metal surface despite of its inefficiency in productivity and its inherent environmental pollution problem. Therefore, the plasma technology has been applied to the conventional process to improve the above issues and become successful in diminishing the ecological harmfulness. However, the drastic short processing time has been sought to increase the productivity by means of new plasma technology so-called, high temperature pulsed plasma flux (HTPPF). The basic principle and features of this HTPPF will be introduced and the present status of this technology will be described in this paper.
Amorphous Tin Oxide Nanohelix Structures as an Anode for Highly Efficient Na-ion Batteries
최일용,조창신,임원광,채병규,박찬경,최원용,이진우,김종규 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0
Amorphous tin oxide (a-SnOx) nanohelix (NH) structures as an anode for Na-ion batteries are fabricated on copper foil by oblique angle deposition method using electron beam evaporation without any additives. With freely controlling the degree of crystallinity, three-dimensional NH structures have high porosity, high aspect ratio and large surface area to result in remarkable reversible specific capacity and stability for volume expansion. The reaction mechanism issues as well as more fundamental advantages of a-SnOx NH structures as an anode for efficient Na-ion batteries will be discussed in detail.