Significant Reduction of Resonant Frequency by Multi-Layered Dielectric Material-Loaded Coaxial Cavity for Microwave Heating

한태규,서유민,최은미 한국전자파학회 2022 Journal of Electromagnetic Engineering and Science Vol.22 No.1

This paper presents a microwave heating method using a cavity whose size is much smaller than the free-space wavelength. The resonant frequency was reduced by inserting multi-layer dielectrics into the cavity, and an appropriate mode was generated in the cavity to heat a specific area inside it. High-permittivity dielectrics were used to make the cavity resonate in the frequency range of a few gigahertz. A formula for the resonant frequency of the multi-layer dielectric material-loaded cylindrical cavity was analytically derived. The frequency reduction by using a dielectric-loaded cylindrical cavity geometry was predicted from the derived formula, from 12.2 GHz to 4.6 GHz, whereas the experiment results showed a reduction from 10.8 GHz to 4.5 GHz. The analytical and the experiment results were compared and analyzed with simulations, which showed good agreement. The heating efficiency at the target in the multi-layered dielectric geometry was analyzed. The electric field inside the target material was measured to prove the temperature response of the microwave heating and was compared with the simulation result. This paper confirms a technical possibility of microwave heating of a smaller-sized cavity with an insertion of low-loss dielectric material in the vicinity of a heating target.

유전발열체를 이용한 마이크로파 가열로의 승온 특성에 관한 연구

전원표(W. P. Chun),김성일(S. I. Kim),박기호(K. H. Park),오상현(S. H. Oh),유병혁(B. H. You),이현구(H. G. Lee) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11

Microwave heating is a process in which the materials couple with microwave, absorb the electromagnetic energy volumetrically, and transform it into heat. This heating mechanism is advantageous to rapid heating rates, uniform heating, selective energy absorption, high efficiency and reduced costs. This paper presents a review of microwave heating application furnace Based on the results of this experiment, we plan to use it as design data for a 75㎾ microwave furnace. The abstract should be written Since the abstract is a shortened version of the paper, it should include the introduction, the main body, and the conclusion with the important ideas or contributions emphasized.

Improving the quality of vegetable foodstuffs by microwave inactivation

조원일,정명수 한국식품과학회 2020 Food Science and Biotechnology Vol.29 No.1

With the aim of improving the loss of quality in retorted vegetables, experiments on pretreatment inactivation using microwaves were carried out to allow the heating intensity to be reduced during retorting. Microwave heating reduced the bacteria level by 103 CFU/g, and was a more effective method considering the short processing time of 3 min and the required energy being 70–80% of that when using steam. The inactivation effect was due to dielectric heat generation by the high-frequency microwaves. The inactivation effect for heat-resistant Bacillus amyloliquefaciens was indicated by a reduction of 102 CFU/g after 3 min of microwave heating. The total bacteria counts for peeled potato and spicy sauce with vegetables decreased by 3–4 log CFU/g after 3 min using microwaves, and heat-resistant microorganisms were reduced by 2 log CFU/g. Combining microwave heating and mild retorting is expected to produce higher quality vegetable foodstuffs compared to conventional retorting.

Effects of self-heating in a dielectric barrier discharge reactor on CHF₃ decomposition

Nguyen, Duc Ba,Lee, Won Gyu Elsevier 2016 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.294 No.-

<P><B>Abstract</B></P> <P>A dielectric barrier discharge reactor, either exposed to atmosphere or immersed in an oil bath, was used to investigate the effects of self-heating on CHF<SUB>3</SUB> decomposition. In the ambient air condition, considerable amounts of energy were delivered to the plasma system in conjunction with high temperatures of the reactor wall, which were due to self-heating. In addition, a great deal of power was used for heating. A comparison of these two ambient conditions on plasma reactions demonstrated that the reactor in oil showed a stable discharge and yielded a greater energy efficiency, suggesting that the immersion of the plasma reactor in electrically insulating oil improved the performance of CHF<SUB>3</SUB> decomposition.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Immersing a reactor in oil bath prevents rapid heating during plasma reaction. </LI> <LI> Self-heating in plasma reactor gave some effects on degree of CHF<SUB>3</SUB> decomposition. </LI> <LI> Plasma reaction in oil ambient showed greater energy efficiency and stable operation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Fabrication and applications of ultraflexible nanostructures using dielectric heating-assisted nanoimprint on PVC films

Tsung-Yeh Wu,Po-Cheng Tsai,Shu-Cheng Lo,Yi-Ru Li,Kuang-Li Lee,Sen-Yeu Yang,Pei-Kuen Wei 한국물리학회 2018 Current Applied Physics Vol.18 No.1

We developed dielectric heating-assisted nanoimprint method for rapid fabrication of ultraflexible nanostructures. Using spin-coating polyvinyl-chloride (PVC) film on the glass slide, the dielectric heating on PVC film helped the pattern transfer from the mold to PVC film in few seconds. Various kinds of nanostructures were successfully made on PVC films with about 20-mm thickness. We demonstrated the applications of ultraflexible metallic nanostructures for bending measurement using surface plasmon resonance (SPR) and surface enhanced Raman scattering (SERS) on the curved surfaces. For measuring bending angles using SPR on capped nanowire arrays, the minimum detection angle was 2.4 103 degree under 0.02 nm wavelength resolution. For SERS measurement, the nanorod arrays on a curved substrate can increase SERS signals for two times as compared to planar SERS substrate.

Functional Design of Dielectric–Metal–Dielectric-Based Thin-Film Encapsulation with Heat Transfer and Flexibility for Flexible Displays

Kwon, Jeong Hyun,Choi, Seungyeop,Jeon, Yongmin,Kim, Hyuncheol,Chang, Ki Soo,Choi, Kyung Cheol American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.32

<P>In this study, a new and efficient dielectric-metal-dielectric-based thin-film encapsulation (DMD-TFE) with an inserted Ag thin film is proposed to guarantee the reliability of flexible displays by improving the barrier properties, mechanical flexibility, and heat dissipation, which are considered to be essential requirements for organic light-emitting diode (OLED) encapsulation. The DMD-TFE, which is composed of Al2O3, Ag, and a silica nanoparticle-embedded sol-gel hybrid nanocomposite, shows a water vapor transmission rate of 8.70 X 10(-6) g/m(2)/day and good mechanical reliability at a bending radius of 30 mm, corresponding to 0.41% strain for 1000 bending cycles. The electrical performance of a thin-film encapsulated phosphorescent organic light-emitting diode (PHOLED) was identical to that of a glass-lid encapsulated PHOLED. The operational lifetimes of the thin-film encapsulated and glass-lid encapsulated PHOLEDs are 832 and 754 h, respectively. After 80 days, the thin-film encapsulated PHOLED did not show performance degradation or dark spots on the cell image in a shelf-lifetime test. Finally, the difference in lifetime of the OLED devices in relation to the presence and thickness of a Ag film was analyzed by applying various TFE structures to fluorescent organic light-emitting diodes (FOLEDs) that could generate high amounts of heat. To demonstrate the difference in heat dissipation effect among the TFE structures, the saturated temperatures of the encapsulated FOLEDs were measured from the back side surface of the glass substrate, and were found to be 67.78, 65.12, 60.44, and 39.67 degrees C after all encapsulated FOLEDs were operated at an initial luminance of 10 000 cd/m(2) for sufficient heat generation. Furthermore, the operational lifetime tests of the encapsulated FOLED devices showed results that were consistent with the measurements of real-time temperature profiles taken with an infrared camera. A multifunctional hybrid thin-film encapsulation based on a dielectric-metal-dielectric structure was thus effectively designed considering the transmittance, gas-permeation barrier properties, flexibility, and heat dissipation effect by exploiting the advantages of each separate layer.</P>

Effects of Crystallization Behavior on Microwave Dielectric Properties of CaMgSi₂O₆ Glass-Ceramics

Choi, Bo Kyeong,Kim, Eung Soo The Korean Ceramic Society 2013 한국세라믹학회지 Vol.50 No.1

Dependence of microwave dielectric properties on the crystallization behaviors of $CaMgSi_2O_6$ (diopside) glass-ceramics was investigated with different heat treatment methods (one and/or two-step). The crystallization behaviors of the specimens, crystallite size and degree of crystallization, were evaluated by differential thermal analysis (DTA), scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis by combined Rietveld and reference intensity ratio (RIR) methods. With an increase in heattreatment temperature, the dielectric constant (K) and the quality factor (Qf) increased due to the increase of the crystallite size and degree of crystallization. The specimens heat-treated by the two-step method had a higher degree of crystallization than the specimens heat-treated by the one-step method, which induced improvement in the quality factor (Qf) of the specimens.

Effects of Crystallization Behavior on Microwave Dielectric Properties of CaMgSi2O6 Glass-Ceramics

최보경,김응수 한국세라믹학회 2013 한국세라믹학회지 Vol.50 No.1

Dependence of microwave dielectric properties on the crystallization behaviors of CaMgSi2O6 (diopside) glass-ceramics was investigated with different heat treatment methods (one and/or two-step). The crystallization behaviors of the specimens, crystallite size and degree of crystallization, were evaluated by differential thermal analysis (DTA), scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis by combined Rietveld and reference intensity ratio (RIR) methods. With an increase in heattreatment temperature, the dielectric constant (K) and the quality factor (Qf) increased due to the increase of the crystallite size and degree of crystallization. The specimens heat-treated by the two-step method had a higher degree of crystallization than the specimens heat-treated by the one-step method, which induced improvement in the quality factor (Qf) of the specimens.

Microwave and RF Heating for Medical Application under Noninvasive Temperature Measurement Using Magnetic Resonance

Yoshio Nikawa,Akira Ishikawa 한국전자파학회JEES 2010 Journal of Electromagnetic Engineering and Science Vol.10 No.4

Recent development of magnetic resonance imaging (MRI) equipment enables interventional radiology (IVR) as diagnosis and treatment under MRI usage. In this paper, a new methodology for magnetic resonance (MR) scanner to apply not only diagnostic equipment but for treatment one is discussed. The temperature measuring procedure under MR is to measure phase shift of T₁, which is the longitudinal relaxation time of proton, for the position inside a sample material with the application of pulsed RF for heating inside the sample as artificial dielectrics. The result shows the possibility to apply MR as temperature measuring equipment and as a heating equipment for applying such as hyperthermia heating modality.

Electric field-driven structural changes in cholesteric shells for optical applications

Buchaiah Gollapelli,Jayalakshmi Vallamkondu 한국물리학회 2019 Current Applied Physics Vol.19 No.12

Cholesteric liquid crystal (CLC) shells with planar anchoring condition were prepared by using a capillary microfluidic technology. Under the influence of an electric field, shells were studied by filling them in glass cells coated with transparent ITO working as an electrode. CLC shells with a planar texture having dark brushes at 0 V under crossed polarizers transformed into a focal conic domain, a fingerprint texture, and finally to an isotropic phase with an increase of electric field that was confirmed by inserting the Bertrand lens in the polarized light path. In addition, our studies also show that the electric-field-driven isotropic phase was due to dielectric heating and local heating effects. The calculated magnitude of the local heating result from the model was in agreement with the experimental observation together with the chiral nematic to isotropic transition due to conventional heating.