A large equilateral triangular prism shows the effect. Position the detector out of the direct beam. Rotate the prism so that it refracts the beam onto the detector.
We start with an aluminum sheet which readily reflects microwaves. Z 0 cloth. The microwaves that pass through the cloth reflect off the metal sheet and pass through the cloth again. The result is no reflection. To perform the demonstration, have the detector off to the side, out of the microwave beam.
Show how a sheet of aluminum positioned in the beam reflects microwaves onto the detector. Next show how the sheet of space cloth reflects microwaves onto the detector. Show how a sheet of Styrofoam does not reflect and therefore only acts as a passive support for the space cloth.
Finally, make a "sandwich" of the three and show how the combination does not reflect. An understanding of Fresnel zone plates helps understand holographic plates, making this demonstration relevant to that subject.
The photo shows an aluminum sheet with rings cut out of it. These rings can be removed. If a plane wave is incident on this sheet, annular wave fronts emanate from the opposite side. One can ask how the intensity varies along the "optical axis. The distance from this point to each annular opening increases with increasing ring radius.
If the ring radii are cunningly chosen so that these distances increase by integral numbers of wavelengths, then one will have constructiive interference at that point. We may speak of the illuminated point as its focus, and the distance of the point to the sheet as the focal length. As one moves further away from the sheet along the axis, one encounters other points for which the condition of constructive interference is satisfied.
The ring radii measured to the outer edge are 11, As is the case with lenses, if the source is closer, the image is further from the plate. When the prisms are well separated, microwaves undergo total internal reflection in the first prism and exit out the side, as is evidenced by the glowing light bulb. This is evidenced by the glowing of the second light bulb while the first one is no longer lit. The general layout is as shown in the photograph. Vertically polarized microwaves from the transmitting horn antenna at the right are intercepted by a second horn antenna which, in turn, directs them into the space between the parallel plates:.
The spacing between the two plates can be varied from 0 to 23 cm. If the spacing between the two plates is less than 6 cm, the cm wavelength microwaves will not propagate between the plates and the light bulb will not light. The plate separation can be increased this is easily done as one of the plates rides on two guide rails to show that there are larger separations that meet the boundary conditions for transmission.
A video camera trained on the light bulb enables a large class to see the light bulb glow. A disadvantage of the light bulb detector is that it is not sensitive enough to show maximum and minimum transmission for the larger plate separations. The audio detector described above is ideal for that: it is completely silent for plate separations less that 6 cm; slowly sliding the plates apart, the audio detector will squeal loudly every time the plate separation meets the boundary conditions for transmission.
Obviously one doesn't need a video camera when using the audio detector. As to understanding what's going on, Feynman presents a nice as usual qualitative explanation which he calls "another way of looking at the guided waves" R.
The potato pellets with the addition of the baking soda were prepared with a single screw extruder TS The snacks were obtained by pellets expansion in a conventional microwave oven. The expansion index and the hardness of the pellets and the snacks, as well as, the texture properties of the snacks were evaluated during this study. The results showed that baking soda addition reduced the potato pellet expansion during their extrusion.
This was an effect of a smaller thickness of the obtained pellets. The addition of baking soda had positive influence on potato snacks expansion in microwave radiation. The higher content of the soda additive resulted in lower hardness of pellets during cutting tests.
The opposite effect was observed during texture measurements of the snacks. The addition of baking soda increased hardness of the expanded snacks.
Soda addition lowers crispness and fragilityof the potato snacks expanded in the microwave radiation. It is typically synthesized in a polar aprotic solvent from the reaction of an aromatic anhydride and a combination of diamines and endcapped with phenylethynylphthalic anhydride. Microwave synthesis of PETI was investigated as a means to eliminate solvent and decrease reaction time. The monomers were manually mixed and placed in a microwave oven for various times to determine optimum reaction conditions.
The synthetic process was subsequently scaled-up to g. Three batches were synthesized and combined to give 1 kg of material that was characterized for thermal and rheological properties and compared to PETI prepared by the classic solution based synthetic method.
The composite panels were analyzed and mechanical properties determined and compared with those fabricated from PETI prepared by the classic solution method. The microwave synthesis process and characterization of neat resin and carbon fiber reinforced composites fabricated by RTM will be presented. Microwave properties of Ni-based ferromagnetic inverse opals.
Kostylev, M. Investigations of microwave properties of Ni-based inverse ferromagnetic opal-like film with the [] axis of the fcc structure along the normal direction to the film have been carried out in the GHz frequency band. We observed multiple spin wave resonances for the magnetic field applied perpendicular to the film, i. For the field applied in the film plane, a broad band of microwave absorption is observed, which does not contain a fine structure.
The field ranges of the responses observed are quite different for these two magnetization directions. This suggests a collective magnetic ground state or shape anisotropy and collective microwave dynamics for this foam-like material. Two different models for this collective behavior are suggested that satisfactorily explain the major experimental results. Hosseini, Seyed Hossein, E-mail: shhosseini iiau. The results showed that the Sr. Microwave heating denitration device.
Purpose: To suppress energy consumption due to a reflection of microwaves. Constitution: Microwaves are irradiated to the nitrate solution containing nuclear fuel materials, to cause denitrating reaction under heating and obtain oxides of the nuclear fuel materials.
A microwave heating and evaporation can for reserving the nitrate solution is disposed slantwise relative to the horizontal plane and a microwave heating device is connected to the evaporation can, and inert gases for agitation are supplied to the solution within the can. Since the evaporation can is slanted, wasteful energy consumption due to the reflection of the microwaves can be suppressed. Moriyama, K. The polarization study indicates that the amplitude of the magnetoresistance oscillations is remarkably responsive to the relative orientation between the linearly polarized microwaves and the current-axis in the specimen.
At low microwave power, P, experiments indicate a strong sinusoidal variation in the diagonal resistance R xx vs. The reflection study indicates strong correlations between the microwave induced magnetoresistance oscillations and oscillatory features in the microwave reflection in a concurrent measurement of the magnetoresistance and the microwave magnetoreflection from the 2DES.
The correlations are followed as a function of the microwave frequency and the microwave power, and the results are reported. Ramanayaka, A. Improvement of microwave -absorbing materials MAMs is the most important research area in various applications, such as in communication, radiation medical exposure, electronic warfare, air defense, and different civilian applications.
The composite material CFP3 showed a wider absorption frequency range and maximum reflection loss of - Microwave and thermal curing of an epoxy resin for microelectronic applications. Johnston, K. Here we present a detailed study of a commercially available epoxy resin, EO Samples that are thermally cured are compared to curing using a recently developed modular microwave processing system.
For commercial purposes it is crucial to demonstrate that microwave curing does not adversely affect the thermal and chemical properties of the material. Therefore, the kinetics of cure and various post cure properties of the resin are investigated. Differential scanning calorimetry DSC is used to monitor the kinetics of the curing reaction, as well as determine the thermal and ageing properties of the material. As expected, the rate of curing is higher when using microwave energy and we attempt to quantify differences compared to conventional thermal curing.
No change in glass transition temperature T g is observed. For the first time, enthalpy relaxation measurements performed on conventional and microwave cured samples are reported and these indicate similar ageing properties at any given temperature under T g. Sintering behaviour and microwave dielectric properties of a new Additionally, optimized microwave dielectric properties can be achieved for the speci- mens using Microwave -assisted hydrothermal synthesis of CePO4 nanostructures: Correlation between the structural and optical properties.
Thereafter, two experimental conditions were selected to assess changes in the properties of CePO 4 nanopowders with pH 1, 5, 9 and The crystal structure and morphology of the nanostructures were characterized by X-ray diffraction XRD , transmission electron microscopy TEM and scanning electron microscopy SEM , respectively.
Diffuse reflectance properties of CePO 4 with different microstructures were studied. The results demonstrated that by using the microwave -assisted hydrothermal method, the shape, size and structural phase of CePO 4 can be modulated by using relatively low synthesis temperatures and short reaction times, and depending on pH, a sintering process is not needed to obtain either a desired phase or size.
Under the selected experimental conditions, the materials underwent an evolution from nanorods to semispherical nanoparticles, accompanied by a phase transition from hexagonal to monoclinic. Process characteristics for microwave assisted hydrothermal carbonization of cellulose. The process characteristics of microwave assisted hydrothermal carbonization of cellulose was investigated and a first order kinetics model based on carbon concentration was developed.
Chemical properties analysis showed that comparing to conventional hydrothermal carbonization, hydrochar with comparable energy properties can be obtained with times decrease in reaction time with assistance of microwave heating.
Results from kinetics study was in great agreement with experimental analysis, that they both illustrated the predominant mechanism of the reaction depend on variations in the reaction rates of two co-existent pathways. Particularly, the pyrolysis-like intramolecular dehydration reaction was proved to be the predominant mechanism for hydrochar generation under high temperatures.
Finally, the enhancement effects of microwave heating were reflected under both soluble and solid pathways in this research, suggesting microwave -assisted hydrothermal carbonization as a more attracting method for carbon-enriched hydrochar recovery. Comparative study on microwave and conventional hydrothermal pretreatment of bamboo sawdust: Hydrochar properties and its pyrolysis behaviors.
Microwave and conventional hydrothermal pretreatment both improved the hydrochar properties and its pyrolysis behaviors. Microwave hydrothermal pretreatment removes more acetyl groups in hemicellulose compared to conventional hydrothermal pretreatment, which may be attributed to the hot spot effect of microwave irradiation.
The peaks of thermogravimetric and derivative thermogravimetric curves of pretreated samples always shifted to higher temperature region. Also, the conventional hydrothermal pretreated samples are more thermally stable than those by microwave heating. In this regard, microwave hydrothermal pretreatment is more suitable for upgrading the pyrolysis oil quality than conventional hydrothermal pretreatment. Effects of postpolymerization microwave irradiation on provisional dental acrylics: physical and mechanical properties.
This study aimed to evaluate the effects of microwave irradiation on the physical and mechanical properties of poly methyl methacrylate PMMA provisional resins. Twenty bars and 20 disc-shaped specimens were fabricated for each selected provisional restorative material Dencor and Duralay.
Test groups were subjected to microwave irradiation 3 minutes at W after polymerization. Bar specimens were subjected to a flexural strength test. Disc-shaped specimens were used to evaluate microhardness.
Glass transition temperature was determined using a differential scanning calorimeter. Microwave irradiation of both tested autopolymerizing PMMA provisional materials resulted in a statistically significant increase in microhardness, degree of conversion and glass transition temperature values.
Also, the results demonstrated a significant increase in flexural strength after postpolymerization microwave irradiation for the Dencor specimens. It is concluded that mechanical and physical properties are positively influenced by microwave irradiation. Single-scattering properties of ice particles in the microwave regime: Temperature effect on the ice refractive index with implications in remote sensing.
For each habit, four temperatures , , , and K are selected to account for temperature dependence of the ice refractive index. The microphysical and scattering properties include projected area, volume, extinction efficiency, single-scattering albedo, asymmetry factor, and six independent nonzero phase matrix elements i.
The computation results show that the temperature dependence of the ice single-scattering properties in the microwave region is significant, particularly at high frequencies. Potential active and passive remote sensing applications of the database are illustrated through radar reflectivity and radiative transfer calculations. For cloud radar applications, ignoring temperature dependence has little effect on ice water content measurements.
For passive microwave remote sensing, ignoring temperature dependence may lead to brightness temperature biases up to 5 K in the case of a large ice water path. Preparation and microwave absorbing property of Ni—Zn ferrite-coated hollow glass microspheres with polythiophene.
This paper also analyzes the relationship between the reflection loss of the absorber and its thickness. Magnetic, dielectric and microwave absorption properties of rare earth doped Ni—Co and Ni—Co—Zn spinel ferrites.
In this article we analyze the electromagnetic properties of rare earth substituted Ni—Co and Ni—Co—Zn cubic ferrites in the microwave band, along with their performance as microwave absorbing materials. Key parameters for this effect are the reduced magnetocrystalline anisotropy and the created crystal inhomogeneities.
Moreover, permittivity is increased with the Y and La content, due to the enhancement of the dielectric orientation polarization.
Regarding the electromagnetic wave attenuation, the prepared ferrites exhibit narrowband return losses RL by virtue of the cancellation of multiple reflections , when their thickness equals an odd multiple of quarter-wavelength. Interestingly, the zero- reflection conditions are satisfied in the vicinity of the ferromagnetic resonance. The presented experimental findings underline the potential of cubic ferrites with high Co concentration in the suppression of electromagnetic reflections well above the 1 GHz region.
This study investigates the sensitivity of multispectral reflectivity to changing snow correlation lengths. Matzler's ice-lamellae radiative transfer model was implemented and tested to evaluate the reflectivity of snow correlation lengths at multiple frequencies from the ultraviolet UV to the microwave bands.
The model reveals that, in the UV to infrared IR frequency range, the reflectivity and correlation length are inversely related, whereas reflectivity increases with snow correlation length in the microwave frequency range. The model further shows that the reflectivity behavior can be mainly attributed to scattering rather than absorption for shallow snowpacks.
The largest scattering coefficients and reflectivity occur at very small correlation lengths approximately 10 exp -5 m for frequencies higher than the IR band. In the microwave range, the largest scattering coefficients are found at millimeter wavelengths.
For validation purposes, the ice-lamella model is coupled with a multilayer snow physics model to characterize the reflectivity response of realistic snow hydrological processes. The evolution of the coupled model simulated reflectivities in both the visible and the microwave bands is consistent with satellite-based reflectivity observations in the same frequencies.
The model results are also compared with colocated in situ snow correlation length measurements Cold Land Processes Field Experiment The analysis and evaluation of model results indicate that the coupled multifrequency radiative transfer and snow hydrology modeling system can be used as a forward operator in a data-assimilation framework to predict the status of snow physical properties , including snow correlation length. In order to improve the quality of ion beams extracted from ECR ion sources it is mandatory to better understand the relations between the plasma conditions and the beam properties.
The present investigations concentrate on the analysis of different beam properties under the influence of various applications of frequency tuning and of multiple frequency heating. The changes in the microwave frequency feeding the plasma affect the electromagnetic field distribution and the dimension and position of the ECR surface inside the plasma chamber.
This in turn has an influence on the generation of the extracted ion beam in terms of intensity, shape and emittance. This arrangement provides a precise determination of the frequencies and of the reflection coefficient along with the beam properties and it confirms again how the frequency and the corresponding electromagnetic field feeding the plasma affects the ECRIS performances.
A sequence of viewing targets positioned inside the beam line monitors the beam shape evolution. The paper is followed by the associated poster. Microwave conductance properties of aligned multiwall carbon nanotube textile sheets. Brown, Brian L. Understanding the conductance properties of multi-walled carbon nanotube MWNT textile sheets in the microwave regime is essential for their potential use in high-speed and high-frequency applications.
To expand current knowledge, complex high-frequency conductance measurements from 0. For all samples, the microwave conductance can be modeled approximately by a shunt capacitance in parallel with a frequency-independent conductance, but with no inductive contribution.
Finally, this is consistent with diffusive Drude conduction as the primary transport mechanism up to 50 GHz. Further, it is found that the microwave conductance is essentially independent of both temperature and magnetic field. The aim of this work is a comparative study of several typical radar-dark parabolas, the neighboring plains and some other geologic units seen in the study areas which include craters Adivar, Bassi, Bathsheba, du Chatelet and Sitwell, at two depths scales: the upper several meters of the study object available through the Magellan-based microwave at Genova-Santos, R.
The flux integrated in a 1 Degree-Sign radius around R. When we deduct the contribution from these two components at The spectral energy distribution from 10 to 60 GHz can be accurately fitted with a model of electric dipole emission from small spinning dust grains distributed in two separated phases of molecular and atomic gas, respectively.
The dust emissivity, calculated by correlating the This fact. This fact, together with the broad knowledge of the stellar content of this region. Microwave -assisted sintering of non-stoichiometric strontium bismuth niobate ceramic: Structural and dielectric properties. In recent years the microwave sintering has been utilized for the synthesis of materials in enhancement of the properties.
A relative density of The microstructure was found to be more uniform in case of SBN sintered by microwave sintering. Both the samples synthesized by two different processes were found to follow Curie—Weiss law above the transition temperature. The Curie temperature was found to be higher for microwave sintered SBN. The dielectric constant and the transition temperature were observed to be higher for SBN ceramic synthesized by microwave sintering technique.
The ac and dc activation energy values were also found to be higher for microwave sintered SBN as compared to conventional sintering technique. Analysis of microwave heating of materials with temperature-dependent properties.
In this paper transient temperature profiles in multilayer slabs are predicted, by simultaneously solving Maxwell's equations with the heat conduction equation, using Galerkin-finite elements. It is assumed that the medium is homogeneous and has temperature-dependent dielectric and thermal properties.
The method is illustrated with applications involving the heating of food and polymers with microwaves. The temperature dependence of dielectric properties affects the heating appreciably, as is shown by comparison with a constant property model. Remote sensing indicates the presence of hydrogen rich regions associated with the lunar poles.
The logical hypothesis is that there is cryogenically trapped water ice located in craters at the lunar poles. Some of the craters have been in permanent darkness for a billion years. The presence of water at the poles as well as other scientific advantages of a polar base, have influenced NASA plans for the lunar outpost. The lunar outpost has water and oxygen requirements on the order of 1 ton per year scaling up to as much as 10 tons per year.
Microwave heating of the frozen permafrost has unique advantages for water extraction. Proof of principle experiments have successfully demonstrated that microwaves will couple to the cryogenic soil in a vacuum and the sublimed water vapor can be successfully captured on a cold trap.
The dielectric properties of lunar soil will determine the hardware requirements for extraction processes. Microwave frequency dielectric property measurements of lunar soil simulant have been measured. The experimental study of the effect of microwave on the physical properties of multi-walled carbon nanotubes.
Haque, A. Temperature profile, morphological analysis by field emission scanning electron microscopy FESEM , defect analysis by Raman spectroscopy, thermal conductivity, thermal diffusivity as well as heat transfer coefficient enhancement ratio were studied which expose some strong witnesses of the effect of microwave on the both purification and dispersion properties of MWCNTs in base fluid distilled water. The highest thermal conductivity enhancement 6. Full Text Available Conductive polypyrrole PPy-manganese ferrite MnFe2O4 nanocomposites with core-shell structure were synthesized by in situ polymerization in the presence of dodecyl benzene sulfonic acid DBSA as the surfactant and dopant and iron chloride FeCl3 as the oxidant.
The structure and magnetic properties of manganese ferrite nanoparticles were measured by using powder X-ray diffraction XRD and vibrating sample magnetometer VSM, respectively. Its morphology, microstructure, and DC conductivity of the nanocomposite were characterized by scanning electron microscopy SEM, Fourier transform infrared spectroscopy FTIR, and four-wire technique, respectively.
The microwave -absorbing properties of the nanocomposite powders dispersing in resin acrylic coating with the coating thickness of 1. In this experiment dual-polarized microwave 37 and 89 GHz observations were accompanied by detailed synchronous observations of meteorology and snowpack physical properties.
The objective of this long-term field experiment was to improve understanding of the effect of changing snow characteristics grain size, density, temperature under various meteorological conditions on the microwave emission of snow and hence to improve retrievals of snow cover properties from satellite observations.
In this paper we present an overview of the field experiment and comparative preliminary analysis of the continuous microwave and snowpack observations and simulations. The observations revealed a large difference between the brightness temperature of fresh and aged snowpack even when the snow depth was the same. This is indicative of a substantial impact of evolution of snowpack properties such as snow grain size, density and wetness on microwave observations.
In the early spring we frequently observed a large diurnal variation in the 37 and 89 GHz brightness temperature with small depolarization corresponding to daytime snowmelt and nighttime refreeze events. Similarly, simulated microwave brightness temperatures using the HUT model were compared with the observed brightness temperatures under different snow conditions to identify different states of the snowpack that developed during the winter season.
The fabrication of microporous metal materials with many potential applications is challenging due to their high chemical activities and the difficulty in controlling the pore size. By adjusting the reaction condition and the composition of the Ni—Al nanoparticle precursor, we have successfully produced the microporous Ni nanoparticles NPs of 22 nm by chemical dealloying method.
During the passivation process, the microporous Ni NPs covered with NiO shell are generated as the result of surface oxidation.
The micropores range from 0. Due to the elimination of Al atoms during dealloying process, the crystalline size of the microporous Ni NPs is sharply decreased to 2—5 nm. Liu, Tong, E-mail: tongliu buaa. Microwave absorbing composites with thin thickness and wideband absorption were successfully prepared by a spraying method using carbonyl iron particles CIPs as absorbers and silicone resin as the matrix. The temperature dependence of electromagnetic properties and RL of the composites were investigated.
Microwave measurement and modeling of the dielectric properties of vegetation. Some of the important applications of microwaves in the industrial, scientific and medical sectors include processing and treatment of various materials, and determining their physical properties.
The dielectric properties of the materials of interest are paramount irrespective of the applications, hence, a wide range of materials covering food products, building materials, ores and fuels, and biological materials have been investigated for their dielectric properties. However, very few studies have been conducted towards the measurement of dielectric properties of green vegetations, including commercially important plant crops such as alfalfa.
Because of its high nutritional value, there is a huge demand for this plant and its processed products in national and international markets, and an investigation into the possibility of applying microwaves to improve both the net yield and quality of the crop can be beneficial. Dielectric properties of chopped alfalfa were measured with this system over frequency range of MHz to 18 GHz, moisture content from The empirical models fitted the measured dielectric data extremely well.
The root mean square error RMSE and the coefficient of determination r2 for dielectric constant and loss factor of leaves. A potential absorption mechanism was proposed for enhancement of the impedance-matching condition and electromagnetic wave-attenuation characteristic of materials.
Specifically, the impedance-matching condition was improved by the combination of conductive polymers and magnetic nanoparticles with CNFs. The electromagnetic wave attenuation characteristic was enhanced by multiple reflections , due to the increased propagation paths. Properties of plasma flames sustained by microwaves and burning hydrocarbon fuels.
Plasma flames made of atmospheric microwave plasma and a fuel-burning flame were presented and their properties were investigated experimentally. The plasma flame generator consists of a fuel injector and a plasma flame exit connected in series to a microwave plasma torch. The plasma flames are sustained by injecting hydrocarbon fuels into a microwave plasma torch in air discharge.
The microwave plasma torch in the plasma flame system can burn a hydrocarbon fuel by high-temperature plasma and high atomic oxygen density, decomposing the hydrogen and carbon containing fuel. We present the visual observations of the sustained plasma flames and measure the gas temperature using a thermocouple device in terms of the gas-fuel mixture and flow rate. The plasma flame volume of the hydrocarbon fuel burners was more than approximately times that of the torch plasma.
While the temperature of the torch plasma flame was only K at a measurement point, that of the diesel microwave plasma flame with the addition of 0. Preliminary experiments for methane plasma flame were also carried out, measuring the temperature profiles of flames along the radial and axial directions.
Finally, we investigated the influence of the microwave plasma on combustion flame by observing and comparing OH molecular spectra for the methane plasma flame and methane flame only. Microwave processed NiMg ferrite: Studies on structural and magnetic properties. Ferrites are magnetic semiconductors realizing an important role in electrical and electronic circuits where electrical and magnetic property coupling is required.
Though ferrite materials are known for a long time, there is a large scope in the improvement of their properties vice sintering and frequency dependence of electrical and magnetic properties with the current technological trends.
Forth coming technology is aimed at miniaturization and smart gadgets, electrical components like inductors and transformers cannot be included in integrated circuits. These components are incorporated into the circuit as surface mount devices whose fabrication involves low temperature co-firing of ceramics and microwave monolithic integrated circuits technologies.
These technologies demand low temperature sinter-ability of ferrites. The series of ferrites are characterized using X-ray diffractometer, scanning electron microscopy, Fourier transform infrared and vibrating sample magnetometer for investigating structural, morphological and magnetic properties respectively.
The initial permeability is studied with magnesium content, temperature and frequency in the temperature range of K— K and 42 Hz—5 MHz. A microwave powered sensor assembly for microwave ovens.
The present invention relates to a microwave powered sensor assembly for micro- wave ovens. The microwave powered sensor assembly comprises a microwave antenna for generating an RF antenna signal in response to microwave radiation at a predetermined excitation frequency.
A dc power supply circuit A sensor is connected to the power supply voltage and configured to measure a physical or chemical property of a food item under heating With different discharge parameters, plasma sheets can vary and influence microwave strength.
Microwave reflection decreases when the discharge current rises, and the opposite occurs in transmission. The C-band microwave is absorbed when it is propagated through large plasma sheets at higher pressure. When plasma density and collision frequency are fitted with incident microwave frequency, a large amount of microwave energy is consumed.
Reflection , transmission and absorption all exist simultaneously. Plasma sheets are an attractive alternative to microwave steering at low pressure, and the microwave reflection used in receiving radar can be altered by changing the discharge parameters.
The influence of microwave irradiation on thermal properties of main rock-forming minerals. Microwave -assisted rock fragmentation has been illustrated to be potentially beneficial for mineral processing, mining and geotechnical engineering. In order to have a comprehensive understanding on the influence of microwave on thermo-mechanical properties of rocks, it is necessary to investigate the interaction effect between microwaves and the main rock-forming minerals.
In this work, eleven rock-forming minerals were tested in a multimode cavity at 2. It was observed that different rock-forming minerals present very different susceptibility induced by microwave treatment.
Enstatite presents the strongest microwave absorption capacity by a large margin and most of the rock-forming minerals are weak microwave absorbers. It is significant that the results can be used to predict the heating behaviors of rocks subjected to microwave energy.
Furthermore, the SEM-EDX elemental analysis demonstrates that the microwave absorption capacity of rock-forming minerals could link to the contribution of the ferrum, which may influence the interacting mechanisms between microwaves and the rock-forming minerals. Bidirectional reflectance distribution function modeling of one-dimensional rough surface in the microwave band. In this study, the bidirectional reflectance distribution function BRDF of a one-dimensional conducting rough surface and a dielectric rough surface are calculated with different frequencies and roughness values in the microwave band by using the method of moments, and the relationship between the bistatic scattering coefficient and the BRDF of a rough surface is expressed.
The BRDF of a rough surface is calculated using the obtained parameter values. Further, the fitting values and theoretical calculations of the BRDF are compared, and the optimization results are in agreement with the theoretical calculation results.
Finally, a reference for BRDF modeling of a Gaussian rough surface in the microwave band is provided by the proposed method. Microwave absorbing properties of rare-earth elements substituted W-type barium ferrite. W-type barium ferrites Ba MnZn 0. Effects of rare-earth elements RE substitution on microstructural and electromagnetic properties were analyzed.
An obvious increase in natural resonance frequency and high frequency relaxation, and a sharp decrease for complex permittivity have been observed. Furthermore, the matching thickness and the reflection loss RL of one-layer ferrite absorber were calculated. It reveals that thin and broad-band can be obtained by RE-substitution. Dy-substituted ferrite composite has excellent microwave absorption properties.
The frequency with respect to dB RL begins from 9. The peak value is Awad, A. The effect of microwave MW irradiation on the hydrogen sorption properties of magnesium powder is explored in the present work. The change of magnetic properties of minerals and rocks after their microwave heating. Full Text Available The possibility of microwaves utilisation in drying processes of different materials e. The presented paper describes the influence of microwave radiation on on the change of magnetic properties of minerals and ores.
The modification of magnetic properties of valuable components of irradiated ores increases the efficiency of process of their magnetic separation.
Changes of magnetic properties of samples were evaluated by measuring the magnetic susceptibility and by X-ray diffraction analysis before and after their microwave heating. The influence of microwave on a rate of change of iron spathic ore to magnetite depending on the time of heating was observed for a grain size of 0.
The weight of tested samples was g. After 10 min. This fact testifies about an intensive decomposition of siderite. The achieved values of magnetic susceptibility, results of chemical analyses as well as the X-ray diffraction records of irradiated samples confirmed the formation of new strongly magnetic mineral phases. Best regards, Mike Gottlieb mg feynmanlectures. The subject of this chapter is the reflection and refraction of light—or electromagnetic waves in general—at surfaces.
We have already discussed the laws of reflection and refraction in Chapters 26 and 33 of Volume I. Our earlier discussion is really about as far as anyone would normally need to go with the subject, but we are going to do it all over again a different way.
One reason is that we assumed before that the indexes were real no absorption in the materials. We want to emphasize that the amplitude of a surface reflection is not a property of the material , as is the index of refraction. There are all kinds of possibilities of interference here—like the colors of oil films.
The formulas we will derive are correct only if the change of index is sudden—within a distance very small compared with one wavelength.
Our equations will work for light for highly polished surfaces. In general, if the index changes gradually over a distance of several wavelengths, there is very little reflection at all. First, we remind you about the convenient way of describing a sinusoidal plane wave we used in Chapter 34 of Volume I. See Fig. So Eq. So the phase of a wave is an invariant, and Eq. You can see why it is very convenient to use the form in Eq.
You can remember the sign in Eq. Then you will understand the optics of an anisotropic crystal. Then you will know whether you are up to the level of a graduate student of In this chapter, however, we will consider only isotropic substances.
We know from experience that when a plane wave arrives at the boundary between two different materials—say, air and glass, or water and oil—there is a wave reflected and a wave transmitted. Suppose we assume no more than that and see what we can work out. We will let it come out of the mathematical machinery. All we have done so far is to describe the three waves; our problem now is to work out the parameters of the reflected and transmitted waves in terms of those of the incident wave.
How can we do that? So we must now look at what happens right at the boundary. Equation This gives us one relation among the fields of the three waves. Although that is a perfectly good way of proceeding, it gives the impression that the problem of dealing with a boundary is different for every different physical problem.
For example, in a problem of heat flow across a boundary, how are the temperatures on the two sides related? Well, you could argue, for one thing, that the heat flow to the boundary from one side would have to equal the flow away from the other side. It is usually possible, and generally quite useful, to work out the boundary conditions by making such physical arguments.
There may be times, however, when in working on some problem you have only some equations, and you may not see right away what physical arguments to use. So although we are at the moment interested only in an electromagnetic problem, where we can make the physical arguments, we want to show you a method that can be used for any problem—a general way of finding what happens at a boundary directly from the differential equations.
Although we usually think of the boundary as being sharply discontinuous, in reality it is not. The physical properties change very rapidly but not infinitely fast. Between the vacuum and the glass there is a smooth, but rapid, transition. Suppose now we take the first of our equations, Eq. If we imagine squashing the boundary to an even thinner layer, the spike would get much higher. Now how can Eq. Only if there is an equally whopping big spike on the other side.
Something on the left-hand side must also be big. We can rewrite Eq. We have, in this way, one of our boundary conditions.
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