A5052550554- Gyrotron and Vacuum Electronics Research
- Pulsed Power Technology Applications
- Terahertz technology and applications
- Microwave Engineering and Waveguides
- Metamaterials and Metasurfaces Applications
- Particle accelerators and beam dynamics
- Particle Accelerators and Free-Electron Lasers
- Plasmonic and Surface Plasmon Research
- Photonic and Optical Devices
- Orbital Angular Momentum in Optics
- Quantum and electron transport phenomena
- Electrostatic Discharge in Electronics
- Superconducting and THz Device Technology
- Graphene research and applications
- Carbon Nanotubes in Composites
- Ammonia Synthesis and Nitrogen Reduction
- Superconducting Materials and Applications
- Microfluidic and Bio-sensing Technologies
- Photonic Crystals and Applications
- Microbial Inactivation Methods
- Molecular Junctions and Nanostructures
- Optical Coatings and Gratings
- Advanced Antenna and Metasurface Technologies
- GaN-based semiconductor devices and materials
- Acoustic Wave Resonator Technologies
Seoul National University
2015-2024
Advanced Institute of Convergence Technology
2017-2024
Tashkent Institute of Irrigation and Agricultural Mechanization Engineers
2020
Suwon Research Institute
2017-2019
Korea Institute of Radiological and Medical Sciences
2016
Institute for Basic Science
2016
Hanwha Solutions (South Korea)
2016
This paper provides a comprehensive overview of optimal methods and processes for recording, processing, classifying electromyography (EMG) signals in the context human movement rehabilitation. It begins by exploring advanced techniques accurate noise-free EMG signal acquisition, emphasizing importance electrode placement, amplification, filtering strategies. The then delves into modern processing methods, such as feature extraction dimensionality reduction, which enhance interpretability...
Fingerprints are unique to primates and koalas but what advantages do these features of our hands feet provide us compared with the smooth pads carnivorans, e.g., feline or ursine species? It has been argued that epidermal ridges on finger decrease friction when in contact surfaces, promote interlocking rough channel excess water, prevent blistering, enhance tactile sensitivity. Here, we found they were at origin a moisture-regulating mechanism, which ensures an optimal hydration keratin...
High-power microwave sources applied to a directed-energy weapon can lead permanent damage by radiating concentrated energy in specific direction disturb or overload electronic equipment. The effect analysis on the target, such as electronics exposed electromagnetic pulse, should be considered an important factor determining performance of high-power and conducting experimental evaluations. In this study, magnetically insulated transmission line oscillator, one representative based vacuum...
The electromagnetic response of a metallic metamaterial to fast-moving electrons is studied by numerical simulations. considered one-dimensional array slits perforated on film and found generate Cerenkov wakes when the electron beam travels near its surface. There no energy threshold for generation such wakes, which would be promising lower operation in compact free-electron-lasers. Moreover, analyzing spectral dependence light, it possible map dispersion relation guided modes supported metamaterial.
A multimode theory of the resonant backward-wave oscillator (BWO) with an electron beam inclined respect to surface a periodic structure—a clinotron—is presented. It is shown that mode interaction provides phase velocity variation in space. The beam–wave power increases at favorable profile along space, which manifests as peaks clinotron zone. In contrast, when it nonfavorable, there drop bandwidth. Developed results are satisfactory agreement BWO reflections and particle-in-cell simulations.
Abstract A high‐quality‐factor (high‐Q) metallic Fano metamaterial is demonstrated both experimentally and theoretically. This material suitable for highly efficient Cerenkov lasing in which subwavelength slits are arranged to form asymmetric unit cells. In contrast conventional dielectric or Smith–Purcell devices, the proposed device, convection electrons traverse high‐Q metamaterial. The interplay between an extremely low group velocity from infinite transverse permittivity of anisotropic...
Metallic metamaterials with positive dielectric responses are promising as an alternative to dielectrics for the generation of Cerenkov radiation [J.-K. So et al., Appl. Phys. Lett. 97(15), 151107 (2010)]. We propose here by theoretical analysis a mechanism couple out from slab surfaces in transverse direction. The proposed method based on Brillouin-zone folding is periodically modify thickness metamaterial axial Moreover, intensity surface-coupled this shows order-of-magnitude enhancement...
Researchers have investigated plasma-related phenomena and internal breakdowns in the gigawatt–terahertz relativistic backward wave oscillator (RBWO) caused by field emissions from surfaces of waveguide circuits these oscillators. In order to increase power-handling capability electron beam devices, an RBWO is proposed form oversized structure which diameter ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math...
An analysis of the effects electromagnetic pulses from a high-power microwave (HPM) radiation technique is conducted using relativistic backward-wave oscillator (RBWO) which uses electron beams in vacuum circuits. The application described here based on device and to generate radiation. RBWO was fabricated operate region with gamma factor (γ) 2 at an acceleration voltage 500 kV. A mode-converted back-wave antenna that converts TM01 TE11 designed because electric field center circuit null....
The possibility of the efficient operation a backward-wave oscillator (BWO) with an electron beam inclined respect to surface periodic structure-a clinotron-is analyzed here. inclination provides effective interaction by all particles thick slow evanescent harmonic cavity modes. problem electron-beam-wave is treated in self-consistent formulation. A theoretical analysis shows that grating decreases demand clinotron for magnetic field magnitude and velocity spread compared conventional BWO....
The field emission properties of the controlled edge a vertically aligned graphene-based thin film are presented. A current and density above 7 mA 200 A/cm2, respectively, with uniform electron emission, achieved. Uniform high emissions can be realized by pre-mechanical shaping post electrical conditioning reduced graphene oxide (rGO) owing to robustness, thinness (<1 μm), well-defined thickness. Field luminance demonstrates over entire area aspect ratio. Along rGO exhibits excellent...
Thermal analysis of an <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> -band 60-kW (continuous-wave) double-ring strapped magnetron for optimizing the design a cathode support structure and cooling system is presented. This consists oxygen-free copper anode with ten built-in channels directly heated tungsten cathode. The operating temperature greater than 2000°C; therefore, proper thermal essential reliable operation. heat convection...
The automodulation processes in backward-wave oscillator with an inclined electron beam (the clinotron) operating at low-focusing magnetic fields have been studied. behavior has analyzed the clinotron for different angles of inclination. It shown that low fields, RF transverse electric field may cause significant changes trajectories, and hence beam–wave interaction power leads to automodulation.
The 3-D particle-in-cell (PIC) simulations are performed to determine the origin of sideband and spurious noises generated in a cooker magnetron. A novel simulation technique is used, which introduces cathode emission current nonuniformities. These nonuniformities due nonuniform distributions electric field on thermionic surface, result from geometry. It shown that end-caps shape magnetic pole-piece geometries causes conventional microwave ovens. results satisfactory agreement with spectrum typical
A practical pillbox window design was performed using impedance matching approach for use in THz vacuum electron devices. The fabricated W-band miniature assembly showed broad frequency band ~ 8 GHz VWSR less than 1.22.
Controlling the line shape of Fano resonance has continued to attract significant research attention in recent years owing its practical applications such as lasing, biosensing, and slow-light devices. However, controllable resonances always require stringent alignment complex symmetry-breaking structures; therefore, manipulation can only be performed with limited degrees freedom a narrow tuning range. This work demonstrates dark-mode excitation independent bright mode for first time,...
This abstract describes the design, fabrication and testing of microfabricated 100 GHz coupled-cavity backward wave oscillator (CCBWO), which is operated in space harmonics -1 at 12 kV 50 mA with round-beam radius 0.18 mm. The RF performance has studied using 3-D electromagnetic field simulator particle-in-cell code. cold-test assembly been fabricated. complete device for hot-test under fabrication. Experimental results will be presented.
An experimental result of a gigawatt-class L-band magnetically insulated transmission line oscillator (MILO) shows the generation transient axial mode pertaining to an anode plasma effect in circuit MILO. The between desired π and 5π/6 causes output power become eccentric. When electrons impact onto metallic surface, exists on surface due electron-impact distortion process. As result, emitted current increase neutralization near cathode. induces faster stronger magnetic insulation, which...
The cell-type continuous electromagnetic radiation system is a demonstration device capable of generating high-power millimeter waves specific wavelength and observing their effects on living organisms. It irradiates biological sample placed in 30 × 50 cm3 cell with the 3.15-mm-wavelength region (with an output ≥1 W) analyzes temperature change sample. A vacuum electronic device-based coupled-cavity backward-wave oscillator converts electron energy beam into radiofrequency (RF) radiates it...
A multimode theory of resonant backward wave oscillator with inclined electron beam - Clinotron is introduced. The mechanism the efficiency enhancement due to mode interaction unveiled through numerical simulation. experimental setup for 0.1 THz being developed and details each part will be presented.
Characteristic x rays generated by a collision between tungsten target and relativistic electron beams from compact electrostatic accelerator based on Marx generator Blumlein pulse-forming line can induce transient ionizing radiation in electronics. While the decelerated beam is close to collector out of range an external magnetic field, Bremsstrahlung occur at same time. Compton scattering also occurs through secondary reaction interactions with quasi-stationary particles such as ejected...