scholarly journals Experimental Observations of Thermal Spikes in Microwave Processing of Ceramic Oxide Fibers

1994 ◽  
Vol 347 ◽  
Author(s):  
Gerald J. Vogt ◽  
Wesley P. Unruh ◽  
J. R. Thomas
Keyword(s):  
Microwave Heating ◽  
Hot Spots ◽  
Hot Spot ◽  
Single Mode ◽  
Microwave Cavity ◽  
X Ray Diffraction ◽  
Thermal Spike ◽  
X Ray ◽  
Heating Behavior ◽  
Fiber Processing

ABSTRACTMicrowave heating of alumina/silica fiber tows in a single-mode microwave cavity at 2.45 GHz has produced a surprising thermal spike behavior on the fiber bundles. During a thermal spike, a “hot spot” on the tow brightens rapidly, persists for a few seconds, and then rapidly extinguishes. A hot spot can encompass the entire tow in the cavity or just a localized portion of the tow. Some local hot spots propagate along the fiber. Thermal spikes are triggered by relatively small (<15%) increases in power, thus having obvious implications for the development of practical microwave fiber processing systems. A tow can be heated through several successive thermal spikes, after which the tow is left substantially cooler than it was originally, although the applied microwave electric field is much larger. X-ray diffraction studies show that after each temperature spike there is a partial phase transformation of the tow material into mullite. After several excursions the tow has been largely transformed to the new, less lossy phase and is more difficult to heat. Heating experiments with Nextel 550 tows are examined for a plausible explanation of this microwave heating behavior.

Cavity Effects and Hot Spot Formulation Inmicrowave Heated Ceramic Fibers

1996 ◽  
Vol 430 ◽  
Author(s):  
G. A. Kriegsmann
Keyword(s):  
Electric Field ◽  
Hot Spots ◽  
Hot Spot ◽  
Single Mode ◽  
Uniform Electric Field ◽  
Ceramic Fibers ◽  
Entire Sample ◽  
Mathematical Equations ◽  
Cavity Effects ◽  
Ceramic Cylinder

AbstractRecently the heating of a thin ceramic cylinder in a single mode applicator was modeled and analyzed assuming a small Biot number and a known uniform electric field through out the sample. The resulting simplified mathematical equations explained the mechanism for the generation and growth of localized regions of high temperature. The results predicted that a hot-spot, once formed, will grow until it consumes the entire sample. Most experimental observations show that the hot-spot stabilizes and moves no further.A new model is proposed which incorporates the effect of the cavity and the nlonuiniform character of the electric field along the axis of the sample. The resulting simplified mathematical equations indicate that these effects stabilize the growth of hot-spots.

scholarly journals Microwave-induced heating behavior of Y-TZP ceramics under multiphysics system

2020 ◽  
Vol 9 (1) ◽  
pp. 119-130
Author(s):  
Kaihui Cui ◽  
Tianqi Liao ◽  
Chen Qiu ◽  
Hua Chen ◽  
Junwen Zhou
Keyword(s):  
Numerical Model ◽  
Microwave Heating ◽  
Three Dimensional ◽  
Heating System ◽  
Dielectric Materials ◽  
Microwave Cavity ◽  
Heating Process ◽  
Highly Sensitive ◽  
Dimensional Distribution ◽  
Heating Behavior

AbstractThis paper aims to investigate the heating behaviors of Y-TZP arrays under microwave irradiation. In this study, a three-dimensional numerical model of the microwave heating system was developed by COMSOL Multiphysics software. The numerical model was verified by microwave heating experiment, and the average root means square errors (RMSE) between the simulation and experimental data also confirmed the reliability of the model. The varying position and arrays of materials were applied to predict and visualize the three-dimensional distribution of the electromagnetic field and temperature during the microwave heating process. The results show that the temperature field distribution in microwave cavity was highly sensitive to the dielectric materials, the arrangement of the Y-TZP array interfered with the distribution of standing waves. The results can serve as references for the study to design and optimize the ceramic’s application in terms of microwave heating.

Synthesis of Alpha Alumina Using Microwave Energy

2014 ◽  
Vol 805 ◽  
pp. 504-507
Author(s):  
Juliana Melo Cartaxo ◽  
M.N. Galdino ◽  
Liszandra Fernanda Araújo Campos ◽  
H.S. Ferreira ◽  
R.H.G.A. Kiminami ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Thermal Analysis ◽  
Acid Solution ◽  
Microwave Heating ◽  
Microwave Energy ◽  
Aluminum Nitrate ◽  
X Ray Diffraction ◽  
Treatment Results ◽  
X Ray ◽  
Alpha Alumina

This work investigated the synthesis of α-alumina using dissolution and re-precipitation of aluminum nitrate and microwave heating. The synthesized powders were characterized by X-ray diffraction, thermal analysis (TGA and DTA) and surface are by BET. The dissolution process was carried out using acid solution and heat treatment. Results depicted the efficiency of the process to accelerating the synthesis of alpha alumina. The results showed that the powders have the microwave structure of α-alumina with specific areas ranging between 3 and 15m2/g and pore diameters between 190 to 485nm.

Superconducting Compound Hg0.8Sb0.2Ba2Ca2Cu3O8+δ Compared with Hg0.8Sb0.2Ba2Ca1Cu2O6+δ to Evaluate Transition Temperature

2020 ◽  
Vol 18 (11) ◽  
pp. 14-18
Author(s):  
Abbas K. Saadon ◽  
Kareem A. Jasim ◽  
Auday H. Shaban
Keyword(s):  
High Temperature ◽  
Transition Temperature ◽  
Solid State ◽  
Solid State Reaction ◽  
Hot Spot ◽  
Solid State Reaction Method ◽  
X Ray Diffraction ◽  
Reaction Method ◽  
X Ray ◽  
Superconducting Compound

The high temperature superconductor’s compounds are one of the hot spot field of science, due to their applications in industries. Hg0.8Sb0.2Ba2Ca2Cu3O8+δ and Hg0.8Sb0.2Ba2Ca1Cu2O6+δ, were manufactured using a doable-step of solid state reaction method. The samples were sintered at 800 ° C. The transition temperatures Tc are found from electrically resistively by using four probe techniques. The resistivity become zero when the transition temperature Tc(offset) have 131 and 119 K, and the onset temperature Tc(onset) have 139 K for Hg0.8Sb0.2Ba2Ca2Cu3O8+δ and 132 K for Hg0.8Sb0.2Ba2Ca1Cu2O6+δ. Analysis of X-ray diffraction showed a tetragonal structure with lattice parameters changes for all samples.

Preparation of Perovskite Type SrNiO3 Photocatalyst Material by Microwave Heating Method

2013 ◽  
Vol 826 ◽  
pp. 211-214 ◽  
Author(s):  
Xin Wang
Keyword(s):  
Microwave Heating ◽  
Heating Time ◽  
X Ray Diffraction ◽  
Calcination Time ◽  
Heating Method ◽  
X Ray ◽  
Preparation Conditions ◽  
Simulated Fuel ◽  
Photocatalytic Material ◽  
Perovskite Type

A new microwave heating method for reparation of SrNiO3 photocatalyst material was described. The optimum preparation conditions are that the microwave power is 560W, the microwave heating time is 30min, the calcination temperature is 700°C and the calcination time is 5h.The compound was measured by X-ray diffraction. In visible light and under the conditions of simulated fuel waste water, the photocatalytic properties of the catalyst material have been studied. The results showed the photocatalytic material prepared by that microwave heating have a high photocatalytic performance of degradation, and the degeneration rate of the dye may reach 98%.

Single-mode dynamic X-ray diffraction for Si and Si nanowires on Si

2014 ◽  
Vol 47 (1) ◽  
pp. 285-290
Author(s):  
Hsin-Yi Chen ◽  
Pei-Tzi Chu ◽  
Shih-Lin Chang
Keyword(s):  
Azimuthal Angle ◽  
Single Mode ◽  
Total Reflection ◽  
Wide Angle ◽  
Si Nanowires ◽  
X Ray Diffraction ◽  
Si Substrate ◽  
X Ray ◽  
Optical Reflection ◽  
Mode Excitation

A method is reported of realizing single-mode diffraction using singly polarized X-ray wide-angle incidence and grazing-emergence diffraction from a bare Si substrate and from Si nanowires on an Si substrate. For a bare Si substrate, the surface-diffracted and specularly reflected beams of single-mode excitation are separated owing to the extremely asymmetric diffraction at grazing emergence. For Si wires on Si, single-mode diffraction is achieved by tuning the X-ray energy or the azimuthal angle under the conditions of total reflection. This finding opens up new opportunities for using crystal diffraction, in addition to optical reflection or refraction, for the design of coherent X-ray optics.

Growth and Stabilization of Hot Spots in Microwave Heated Ceramic Fibers

1994 ◽  
Vol 347 ◽  
Author(s):  
Gregory A. Kriegsmann
Keyword(s):  
Electric Field ◽  
Hot Spots ◽  
Hot Spot ◽  
Single Mode ◽  
Uniform Electric Field ◽  
Fiber Axis ◽  
Ceramic Fibers ◽  
Mathematical Equations ◽  
Effective Heat Transfer Coefficient ◽  
Ceramic Cylinder

ABSTRACTRecently the heating of a thin ceramic cylinder in a single mode applicator was modeled and analyzed assuming a small Biot number and a known uniform electric field through out the sample. The resulting simplified mathematical equations explained the mechanism for the generation and growth of localized regions of high temperature. The results predicted that a hot-spot, once formed, will grow until it consumes the entire sample. Although this phenomenon is seen in some experiments, others show that the hot-spot stabilizes and moves no further.A new model is proposed which incorporates the dependence of the thermal conductivity and the effective heat transfer coefficient upon temperature, and the nonuniformity of the electric field along the fiber axis. The resulting simplified mathematical equations indicate that these effects may stabilize the growth of hot-spots.

Deep learning model can predict water binding sites on the surface of proteins using limited-resolution data

2020 ◽  
Author(s):  
Jan Zaucha ◽  
Charlotte A. Softley ◽  
Michael Sattler ◽  
Grzegorz M. Popowicz
Keyword(s):  
Deep Learning ◽  
High Resolution ◽  
Electron Density ◽  
Binding Sites ◽  
Hot Spots ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
Water Binding ◽  
X Ray ◽  
Deep Learning Model

ABSTRACTThe surfaces of proteins are generally hydrophilic but there have been reports of sites that exhibit an exceptionally high affinity for individual water molecules. Not only do such molecules often fulfil critical biological functions, but also, they may alter the binding of newly designed drugs. In crystal structures, sites consistently occupied in each unit cell yield electron density clouds that represent water molecule presence. These are recorded in virtually all high-resolution structures obtained through X-ray diffraction. In this work, we utilized the wealth of data from the RCSB Protein Data Bank to train a residual deep learning model named ‘hotWater’ to identify sites on the surface of proteins that are most likely to bind water, the so-called water hot spots. The model can be used to score existing water molecules from a PDB file to provide their ranking according to the predicted binding strength or to scan the surface of a protein to determine the most likely water hot-spots de novo. This is computationally much more efficient than currently used molecular dynamics simulations. Based on testing the model on three example proteins, which have been resolved using both high-resolution X-ray crystallography (providing accurate positions of trapped waters) as well as low-resolution X-ray diffraction, NMR or CryoEM (where structure refinement does not yield water positions), we were able to show that the hotWater method is able to recover in the “water-free” structures many water binding sites known from the high-resolution structures. A blind test on a newly solved protein structure with waters removed from the PDB also showed good prediction of the crystal water positions. This was compared to two known algorithms that use electron density and was shown to have higher recall at resolutions >2.6 Å. We also show that the algorithm can be applied to novel proteins such as the RNA polymerase complex from SARS-CoV-2, which could be of use in drug discovery. The hotWater model is freely available at (https://pypi.org/project/hotWater/).

scholarly journals Measuring the density structure of an accretion hot spot

Nature ◽  
2021 ◽  
Vol 597 (7874) ◽  
pp. 41-44
Author(s):  
C. C. Espaillat ◽  
C. E. Robinson ◽  
M. M. Romanova ◽  
T. Thanathibodee ◽  
J. Wendeborn ◽  
...  
Keyword(s):  
Hot Spots ◽  
Hot Spot ◽  
Time Lag ◽  
Optical Emission ◽  
Stellar Surface ◽  
Radial Density ◽  
Coronal Emission ◽  
X Ray ◽  
Emit Radiation ◽  
Magnetospheric Accretion

AbstractMagnetospheric accretion models predict that matter from protoplanetary disks accretes onto stars via funnel flows, which follow stellar magnetic field lines and shock on the stellar surfaces1–3, leaving hot spots with density gradients4–6. Previous work has provided observational evidence of varying density in hot spots7, but these observations were not sensitive to the radial density distribution. Attempts have been made to measure this distribution using X-ray observations8–10; however, X-ray emission traces only a fraction of the hot spot11,12 and also coronal emission13,14. Here we report periodic ultraviolet and optical light curves of the accreting star GM Aurigae, which have a time lag of about one day between their peaks. The periodicity arises because the source of the ultraviolet and optical emission moves into and out of view as it rotates along with the star. The time lag indicates a difference in the spatial distribution of ultraviolet and optical brightness over the stellar surface. Within the framework of a magnetospheric accretion model, this finding indicates the presence of a radial density gradient in a hot spot on the stellar surface, because regions of the hot spot with different densities have different temperatures and therefore emit radiation at different wavelengths.

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