A5044610827- Gyrotron and Vacuum Electronics Research
- Pulsed Power Technology Applications
- Terahertz technology and applications
- Metamaterials and Metasurfaces Applications
- Microwave Engineering and Waveguides
- Plasmonic and Surface Plasmon Research
- Electrostatic Discharge in Electronics
- Graphene research and applications
- Orbital Angular Momentum in Optics
- Carbon Nanotubes in Composites
- Quantum and electron transport phenomena
- Heat Transfer and Boiling Studies
- Particle accelerators and beam dynamics
- Microfluidic and Bio-sensing Technologies
- Advanced Antenna and Metasurface Technologies
- Diamond and Carbon-based Materials Research
- Nanofluid Flow and Heat Transfer
- Microbial Inactivation Methods
- Planetary Science and Exploration
- Extraction and Separation Processes
- Heat Transfer and Optimization
- Astro and Planetary Science
- Advancements in Battery Materials
- Isotope Analysis in Ecology
- Biometric Identification and Security
Handong Global University
2024
Seoul National University
2012-2022
Dong-A University
2022
Advanced Institute of Convergence Technology
2020-2021
Korea Institute of Radiological and Medical Sciences
2016
Institute for Basic Science
2016
Hanwha Solutions (South Korea)
2016
Kyungpook National University
2013-2015
Pohang University of Science and Technology
2008-2009
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...
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 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...
Carbon nanotubes (CNTs) have great potential in the development of high-power electron beam sources. However, for such a high-performance electronic device, electric and thermal contact problem between metal CNTs must be improved. Here, we report graphene as an interfacial layer to improve contact. The results dramatic decrease electrical resistance by order 2 increase conductivity 16%. Such high improvement interface leads superior field emission performance with very low turn-on 1.49 V...
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.
Many pool boiling experiments to enhance the nucleate condition have been conducted and could get brilliant challengeable results. A consensus was that CHF heat transfer were affected by a modified heating surface. One of efforts nanofluids experiments, they exhibited an incredible enhancement when used as working fluid in boiling. The results also showed clearly such large came from deposition nanoparticles on surface changing condition. covered oxidized metal has high wettability, so it...
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
This paper reports on a broadband transmission filter that employs the guided mode resonances pertaining to terahertz metasurface composed of metallic gold disks with quartz slab. Unlike structures involving conventional metasurfaces, two identical metasurfaces are placed upper and lower sides thick structure can excite both even odd resonances. The interaction at similar frequencies produces peak. sharp spectral feature each resonance leads abrupt degradation edge, which enable development...
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,...
Nanofluids, which contain uniformly and stably dispersed nanoparticles, exhibit an abnormal enhancement of the critical heat flux (CHF) when used as a working fluid in pool boiling. It has recently been demonstrated that optimal CHF nanofluids is attained by significant deposition nanoparticles on heater surface during The oxidized metal significantly enhances wettability, fractal micro/nanostructures formed nanoparticle induce liquid suction due to capillary wicking. supposed superior...
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...
Objectives: Leukocyte NADPH oxidase, which is active in neutrophils, a membrane-bound enzyme that catalyzes the reduction of oxygen to O2− by using as an electron donor. Previously, we reported casein kinase 2 (CK2), ubiquitous and highly conserved Ser/Thr kinase, responsible for p47phox phosphorylation CK2 regulates deactivation oxidase.
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...
A klystron is an important vacuum device which useful in medical linear accelerators because it amplifies the radio-frequency (RF) signals required to produce high-energy particle beams. The properties of nonlinear input and output dynamics circuit arouse distortion various types parameters pertaining beam voltage, current, RF power, operating frequency from unpredictable external factors. Therefore, low-level (LLRF) control systems can facilitate regulation a desired level. Low-level system...
A highly efficient terahertz (THz) radiation mechanism is studied with the use of strong interaction between convection electrons and a half-period phase-shifted grating resonator. The large fraction fundamental TE mode longitudinally polarized, it excites intense plasma–terahertz wave coupling at shallow grating, which enables RF generation relatively low operating voltage. particle-in-cell (PIC) simulation predicts that phase-staggered resonator generates 0.22 THz output power exceeding...