The photoelectron property is directly related to the light-energy conversion efficiency of solar cells. In this paper, the photoelectron dynamic of semiconductor was analyzed. The diffusion of electrons has influence...The photoelectron property is directly related to the light-energy conversion efficiency of solar cells. In this paper, the photoelectron dynamic of semiconductor was analyzed. The diffusion of electrons has influence on the dielectric function of the solar cell material. And the amplitude variance of the imaginary and real part of the dielectric function is in direct proportion to the dynamic process of free and shallow-trapped electrons. Based on the untouched detection technique, the method is present to detect the amplitude change of the microwave signal which is passing through the material whose dielectric function changes after exposure. A 35 GHz oscillator was used as a microwave source. The absorption and dispersion microwave signals, which contain the dynamic information of free and shallow-trapped electron signal, are split respectively with phase-sensitive instrument. The photoelectron character of n-type Si(100) thin film was investigated by the novel equipment, and the lifetime of different kinds of electrons with the resolution of 1 ns was obtained. The equipment can be directly used in the study of the optoelectronic conversion mechanism of solar cells.展开更多
The manganite perovskite polycrystal samples of (La1-xDyx)2/3Sr1/3MnO3 (x = 0, 0.1, 0.2, 0.35, and 0.5) doped with Dy were prepared by solid state reaction in atmosphere to measure their X-ray diffraction (XRD) ...The manganite perovskite polycrystal samples of (La1-xDyx)2/3Sr1/3MnO3 (x = 0, 0.1, 0.2, 0.35, and 0.5) doped with Dy were prepared by solid state reaction in atmosphere to measure their X-ray diffraction (XRD) patterns, scanning electric microscope (SEM) images, infrared absorption spectra, and microwave electromagnetic properties. The displacement of the XRD peaks of the samples was found, and the 2θ increases from 0.05o to 0.5o. The grains of undoped La2/3Sr1/3MnO3 not only have the greatest size, but also the most regular shape. The size of the grains decreases as the Dy doping content increases from 0 to 0.5. The infrared absorption spectra of all samples were measured at room temperature. An absorption peak corresponding to the stretching vibration mode of Mn-O bonds appears within the range of 591-629 cm-1. The absorption peak shifts from a higher frequency to a lower one with the decrease of the average ionic radius of A-site. The frequency de- pendence of microwave-absorbing properties, imaginary components of the complex magnetic permeability μ" and dielectric permeability ε" for all samples was measured at room temperature from 8 to 13 GHz. The results show that the loss of microwave absorption can be attrib- uted to both the magnetic and electric losses. The increase of Dy content not only enhances the microwave absorption but also causes the displacement of the absorption peaks.展开更多
In this study the effects of microwaves on the secondary structure of three typical proteins have been investigated. A set of samples of lysozyme, bovine serum albumin and myoglobin in D2O solutions were exposed for 8...In this study the effects of microwaves on the secondary structure of three typical proteins have been investigated. A set of samples of lysozyme, bovine serum albumin and myoglobin in D2O solutions were exposed for 8 hours to mobile phone microwaves at 900 MHz at a magnetic field intensity around 16 mA/m. The relative effects on the secondary structure of the proteins were studied by means of Fourier Transform Infrared Spectroscopy. An increase of the amide I band intensity in the secondary structure of the proteins was observed after the microwaves exposure. Furthermore, a weak shift of the amide I mode of bovine serum albumin and a heavier shift of the amide I of myoglobin occurred after the exposure. In addition, a clear increasing of the β-sheet components with respect to the α-helix content was observed in the spectra of bovine serum albumin and myoglobin after the exposure, suggesting the hypothesis of the formation of aggregates.展开更多
Effect of Ti(iso-C3H7O)4 treatment on the photoinduced charge carrier kinetics of nanocrystalline porous TiO2 films is studied by time-resolved microwave conductivity measurements. Analysis of the transient photocond...Effect of Ti(iso-C3H7O)4 treatment on the photoinduced charge carrier kinetics of nanocrystalline porous TiO2 films is studied by time-resolved microwave conductivity measurements. Analysis of the transient photoconductivity decays indicates that Ti(iso-C3H7O)4 treatment leads to an increased concentration of photogenerated charge carriers and a fast interfacial transfer rate of holes via the surface modification of the freshly growing TiO2 nanocrystallites.展开更多
This paper reports the content of a lecture presented at the 1995 International Conference and Exhibition on Electronic Measurement and Instrumentation, held in Shanghai, China in 1995. The paper presents(thanks to th...This paper reports the content of a lecture presented at the 1995 International Conference and Exhibition on Electronic Measurement and Instrumentation, held in Shanghai, China in 1995. The paper presents(thanks to the courtesy of several scientists) some of the most significant results recently obtained in the field of short range microwave imaging. The overview concerns the research activity carried out in Europe and is focused on microwave imaging for non destructive testing, civil engineering, and scientific and medical applications. This type of imaging is characterized by a relatively short distance between the object to be detected and the probes.展开更多
Simultaneous development of well impedance matching and strong loss capability has become a mainstream method for achieving outstanding electromagnetic microwave absorption(EMWA)performances over wide temperature rang...Simultaneous development of well impedance matching and strong loss capability has become a mainstream method for achieving outstanding electromagnetic microwave absorption(EMWA)performances over wide temperature range.However,it is difficult to pursue both due to the mutual restraint of relationship between impedance matching and loss capability about temperature.Here,we propose a flexible regulation engineering of titanium nitride(TiN)nanofibrous membranes(NMs,TNMs),which could be distributed uniformly in the polydimethylsiloxane(PDMS)matrix and contributed to the formation of abundant local conductive networks,generating the local conductive loss and enhancing the loss ability of EMWs.Moreover,when the TNMs are used as functional units and dispersed in the matrix,the corresponding composites exhibit an outstanding anti-reflection effect on microwaves.As hoped,under the precondition of good impedance matching,local conductive loss and polarization loss together improve the loss capacity at room temperature,and polarization loss can compensate the local conductive loss to acquire effective dielectric response at elevated temperature.Benefiting from the reasonably synergistic loss ability caused by flexible regulation engineering,the corresponding composites exhibit the perfect EMWA performances in a wide temperature range from 298 to 573 K.This work not only elaborates the ponderable insights of independent membrane in the composition-structure-function connection,but also provides a feasible tactic for resolving coexistence of well impedance matching and strong loss capability issues in wide temperature spectrum.展开更多
Radio frequency/microwave-directed energy sources using wide bandgap SiC photoconductive semiconductors have attracted much attention due to their unique advantages of high-power output and multi-parameter adjustable ...Radio frequency/microwave-directed energy sources using wide bandgap SiC photoconductive semiconductors have attracted much attention due to their unique advantages of high-power output and multi-parameter adjustable ability.Over the past several years,benefitting from the sustainable innovations in laser technology and the significant progress in materials technology,megawatt-class output power electrical pulses with a flexible frequency in the P and L microwave wavebands have been achieved by photoconductive semiconductor devices.Here,we mainly summarize and review the recent progress of the high-power photonic microwave generation based on the SiC photoconductive semiconductor devices in the linear modulation mode,including the mechanism,system architecture,critical technology,and experimental demonstration of the proposed high-power photonic microwave sources.The outlooks and challenges for the future of multi-channel power synthesis development of higher power photonic microwave using wide bandgap photoconductors are also discussed.展开更多
A new simple two-scale model on the polarimetric microwave emission of ocean surface is derived at first, which can be ex-pressed as an integral of weighting functions (M0 and M2) and ocean surface curvature spectrum ...A new simple two-scale model on the polarimetric microwave emission of ocean surface is derived at first, which can be ex-pressed as an integral of weighting functions (M0 and M2) and ocean surface curvature spectrum coefficients (C0 and C2). This provides a simple way to investigate the effect of curvature spectrum on ocean emission. It is found that ocean waves with wavelengths both comparable to and much greater than the electromagnetic wavelength can contribute to the harmonics of ocean surface microwave emission, depending on the magnitude of the ocean surface spectrum in these length scales. Bright-ness temperature predictions differ significantly due to present diverse spectrum models, and thus a study on wave spectrum obtained inversely from brightness temperature measurements is necessary. From the ocean surface radiation data measured by polarimetric microwave radiometer, we derived an ocean wave spectrum with a wider wave number range, using the proposed two-scale model and constrained linear least-squares method. The derived ocean wave spectrum is useful for comparing with present diverse models.展开更多
Microwave induced plasma torches find wide applications in material and chemical analysis.Investigation of a coaxial electrode microwave induced plasma(CE–MIP)torch is conducted in this study,making it available for ...Microwave induced plasma torches find wide applications in material and chemical analysis.Investigation of a coaxial electrode microwave induced plasma(CE–MIP)torch is conducted in this study,making it available for glass surface modification and polishing.A dedicated nozzle is designed to inject secondary gases into the main plasma jet.This study details the adaptation of a characterisation process for CE–MIP technology.Microwave spectrum analysis is used to create a polar plot of the microwave energy being emitted from the coaxial electrode,where the microwave energy couples with the gas to generate the plasma jet.Optical emission spectroscopy analysis is also employed to create spatial maps of the photonic intensity distribution within the plasma jet when different additional gases are injected into it.The CE–MIP torch is experimentally tested for surface energy modification on glass where it creates a super-hydrophilic surface.展开更多
Microwave-induced thermo-acoustic tomography (MITAT) is a promising technique with great potential in biomedical imaging. It has both the high contrast of the microwave imaging and the high resolution of the ultrasoun...Microwave-induced thermo-acoustic tomography (MITAT) is a promising technique with great potential in biomedical imaging. It has both the high contrast of the microwave imaging and the high resolution of the ultrasound imaging. In this paper, the proportional relationship between the absorbed microwave energy distribution and the induced ultrasound source distribution is derived. Further, the time reversal mirror (TRM) technique based on the pseudo-spectral time domain (PSTD) method is applied to MITAT system. The simulation results show that high contrast and resolution can be achieved by the TRM technique based on PSTD method even for the received signals with very low signal-to-noise ratio (SNR) and the model parameter with random fluctuation.展开更多
^(57)Fe Mssbauer spectroscopy was used to study the mechanism and regularity of coal desulfurization by microwave irradiation combined with magnetic-separation and with chemical acid-leaching. The results of phase ana...^(57)Fe Mssbauer spectroscopy was used to study the mechanism and regularity of coal desulfurization by microwave irradiation combined with magnetic-separation and with chemical acid-leaching. The results of phase analyses show that the decomposing reaction of pyrite intrinsic in coal, caused by the selective dielectric heating of microwave electromagnetic energy, FeS_2→Fe_(1-x)S→FeS, consecutively progresses towards the right-hand side with increased irradiation time. The whole process of microwave desulfurization of raw coal consists of the initiation, the promotion, and the saturation stages. The optimum desulfurization efficiency for microwave irradiation combined with magnetic-separation treatment and with chemical acid-leaching treatment can be attained by appropriately controlling the irradiation time to enable the corresponding microwave treatment to lie in the promotion stage and the saturation stage, respectively.展开更多
Based on Tian et al. 's theoretical model of microwave scattering, by using the wind wave spectrum suggested by Fung et al. , numerical results of polarized back-scattering were calculated. The quantitative relations...Based on Tian et al. 's theoretical model of microwave scattering, by using the wind wave spectrum suggested by Fung et al. , numerical results of polarized back-scattering were calculated. The quantitative relationships between the calculated backscattering cross section and the environmental parameters, such as wind speeds, azimuthal angles and incidence angles, were studied. Compared with the traditional two-scale scattering model, the results are much more coincident with the observations under the condition of moderate incidence angles, which is very useful to make up for the two-scale model. To make the new calculation model to be used conveniently in the practice, its simplified form was proposed.展开更多
Developing a comprehensive model of the early universe that describes events and conditions prior to recombination has proved difficult. Using a new approach, we express Heisenberg’s uncertainty principle in terms of...Developing a comprehensive model of the early universe that describes events and conditions prior to recombination has proved difficult. Using a new approach, we express Heisenberg’s uncertainty principle in terms of measures and counts of those measures to resolve an expression consisting entirely of counts. The description allows us to resolve explicit values for discrete measures. With these values, we present new expressions describing the earliest epoch and the transition event that initiates expansion. We determine the quantity, age, density, and temperature of the cosmic microwave background (CMB). Moreover, we approach the CMB power spectrum anew, describing each mass/energy distribution, its physical significance, its peak temperature, and the effects of relativity. We do not engage in fitting or modification of the existing laws of physics. The approach is classical and correlates both quantum and cosmological phenomena with descriptive expressions that are measurable, verifiable, and falsifiable.展开更多
The Ba_(12)ReNb_(9)O_(36)(Re=Yb,Ce,Tm,Er,Y,Ho,Dy,Gd)ceramics are synthesized by solid-phase reaction method.The phase composition,crystal structure,microstructure,and microwave dielectric properties of the ceramics ar...The Ba_(12)ReNb_(9)O_(36)(Re=Yb,Ce,Tm,Er,Y,Ho,Dy,Gd)ceramics are synthesized by solid-phase reaction method.The phase composition,crystal structure,microstructure,and microwave dielectric properties of the ceramics are investigated by X-ray diffraction,X-ray photoelectron spectroscopy,Scanning electron microscopy and Raman spectrum.The optimal microwave dielectric properties(ε_(r)=37.23,Q×f=36600 GHz,andτ_(f)=34 ppm/℃)are obtained for Ba_(12)YbNb_(9)O_(36) ceramic sintered at 1420℃for 6 h.In this system,the variation of dielectric constant is dominated by polarizability.The Q×f is mainly affected by internal strain/fluctuation of d-spacing.The variation of τ_(f) is related to the temperature coefficient of dielectric constant and the oxygen octahedron distortion.Furthermore,the reduction of Ce^(4+) ions,the relative density,linear thermal expansion coefficient,and the second phase are also important factors affecting microwave dielectric properties.展开更多
The experiment results of ultrawide band electromagnetic radiation with DC biased GaAs photoconductive semiconductor switch combining double ridge horn antenna triggered by high repeat frequency femto-second laser pul...The experiment results of ultrawide band electromagnetic radiation with DC biased GaAs photoconductive semiconductor switch combining double ridge horn antenna triggered by high repeat frequency femto-second laser pulse are reported.The GaAs switches are insulated by solid multi-layer transparent dielectrics and the distance of two electrodes is 3mm.The electrode material of the switch is ohmic contact through alloy technics with definite proportion of Au/Ge/Ni.This switch and double ridge horn antenna are integrated and the receive antenna is connected with the test instrument.From receiving antenna,ultra fast electrical pulse of 200ps rise time and 500ps pulse width is obtained,the repetition rate of the pulse is about 82MHz and the frequency spectrum is in the range of 4.7MHz~14GHz.The radiation characteristic of the ultrafast electrical pulse is analyzed.展开更多
基金This work was financially supported by the National Natural Science Foundation of China (No.10274017)the Natural Science Foundation of Hebei Province, China (No.103097, E2005000131)
文摘The photoelectron property is directly related to the light-energy conversion efficiency of solar cells. In this paper, the photoelectron dynamic of semiconductor was analyzed. The diffusion of electrons has influence on the dielectric function of the solar cell material. And the amplitude variance of the imaginary and real part of the dielectric function is in direct proportion to the dynamic process of free and shallow-trapped electrons. Based on the untouched detection technique, the method is present to detect the amplitude change of the microwave signal which is passing through the material whose dielectric function changes after exposure. A 35 GHz oscillator was used as a microwave source. The absorption and dispersion microwave signals, which contain the dynamic information of free and shallow-trapped electron signal, are split respectively with phase-sensitive instrument. The photoelectron character of n-type Si(100) thin film was investigated by the novel equipment, and the lifetime of different kinds of electrons with the resolution of 1 ns was obtained. The equipment can be directly used in the study of the optoelectronic conversion mechanism of solar cells.
基金supported by the National Natural Science Foundation of China (No. 60561001)the Natural Science Foundation of Inner Mongolia Autonomous Region, China (No. 200408020105)+1 种基金the Program for New Century Excellent Talents in Universities (No. NCET-05-0272)College Science and Technology Re-search Project of Inner Mongolia Autonomous Region, China (No. NJ04094)
文摘The manganite perovskite polycrystal samples of (La1-xDyx)2/3Sr1/3MnO3 (x = 0, 0.1, 0.2, 0.35, and 0.5) doped with Dy were prepared by solid state reaction in atmosphere to measure their X-ray diffraction (XRD) patterns, scanning electric microscope (SEM) images, infrared absorption spectra, and microwave electromagnetic properties. The displacement of the XRD peaks of the samples was found, and the 2θ increases from 0.05o to 0.5o. The grains of undoped La2/3Sr1/3MnO3 not only have the greatest size, but also the most regular shape. The size of the grains decreases as the Dy doping content increases from 0 to 0.5. The infrared absorption spectra of all samples were measured at room temperature. An absorption peak corresponding to the stretching vibration mode of Mn-O bonds appears within the range of 591-629 cm-1. The absorption peak shifts from a higher frequency to a lower one with the decrease of the average ionic radius of A-site. The frequency de- pendence of microwave-absorbing properties, imaginary components of the complex magnetic permeability μ" and dielectric permeability ε" for all samples was measured at room temperature from 8 to 13 GHz. The results show that the loss of microwave absorption can be attrib- uted to both the magnetic and electric losses. The increase of Dy content not only enhances the microwave absorption but also causes the displacement of the absorption peaks.
文摘In this study the effects of microwaves on the secondary structure of three typical proteins have been investigated. A set of samples of lysozyme, bovine serum albumin and myoglobin in D2O solutions were exposed for 8 hours to mobile phone microwaves at 900 MHz at a magnetic field intensity around 16 mA/m. The relative effects on the secondary structure of the proteins were studied by means of Fourier Transform Infrared Spectroscopy. An increase of the amide I band intensity in the secondary structure of the proteins was observed after the microwaves exposure. Furthermore, a weak shift of the amide I mode of bovine serum albumin and a heavier shift of the amide I of myoglobin occurred after the exposure. In addition, a clear increasing of the β-sheet components with respect to the α-helix content was observed in the spectra of bovine serum albumin and myoglobin after the exposure, suggesting the hypothesis of the formation of aggregates.
基金This work was supported by National Research Fund for Fundamental Key Project(G2000028205)Innovative Foundation of Chinese Academy of Sciences(KGCX2-303-02)the Project of the National Natural Science Foundation of China(29873057).
文摘Effect of Ti(iso-C3H7O)4 treatment on the photoinduced charge carrier kinetics of nanocrystalline porous TiO2 films is studied by time-resolved microwave conductivity measurements. Analysis of the transient photoconductivity decays indicates that Ti(iso-C3H7O)4 treatment leads to an increased concentration of photogenerated charge carriers and a fast interfacial transfer rate of holes via the surface modification of the freshly growing TiO2 nanocrystallites.
文摘This paper reports the content of a lecture presented at the 1995 International Conference and Exhibition on Electronic Measurement and Instrumentation, held in Shanghai, China in 1995. The paper presents(thanks to the courtesy of several scientists) some of the most significant results recently obtained in the field of short range microwave imaging. The overview concerns the research activity carried out in Europe and is focused on microwave imaging for non destructive testing, civil engineering, and scientific and medical applications. This type of imaging is characterized by a relatively short distance between the object to be detected and the probes.
基金support of the National Natural Science Foundation of China(Nos.22305066 and U1704253).
文摘Simultaneous development of well impedance matching and strong loss capability has become a mainstream method for achieving outstanding electromagnetic microwave absorption(EMWA)performances over wide temperature range.However,it is difficult to pursue both due to the mutual restraint of relationship between impedance matching and loss capability about temperature.Here,we propose a flexible regulation engineering of titanium nitride(TiN)nanofibrous membranes(NMs,TNMs),which could be distributed uniformly in the polydimethylsiloxane(PDMS)matrix and contributed to the formation of abundant local conductive networks,generating the local conductive loss and enhancing the loss ability of EMWs.Moreover,when the TNMs are used as functional units and dispersed in the matrix,the corresponding composites exhibit an outstanding anti-reflection effect on microwaves.As hoped,under the precondition of good impedance matching,local conductive loss and polarization loss together improve the loss capacity at room temperature,and polarization loss can compensate the local conductive loss to acquire effective dielectric response at elevated temperature.Benefiting from the reasonably synergistic loss ability caused by flexible regulation engineering,the corresponding composites exhibit the perfect EMWA performances in a wide temperature range from 298 to 573 K.This work not only elaborates the ponderable insights of independent membrane in the composition-structure-function connection,but also provides a feasible tactic for resolving coexistence of well impedance matching and strong loss capability issues in wide temperature spectrum.
基金supported in part by the National Natural Science Foundation of China(Nos.62071477 and 62101577)the Natural Science Foundation of Hunan Province(No.2021JJ40660)。
文摘Radio frequency/microwave-directed energy sources using wide bandgap SiC photoconductive semiconductors have attracted much attention due to their unique advantages of high-power output and multi-parameter adjustable ability.Over the past several years,benefitting from the sustainable innovations in laser technology and the significant progress in materials technology,megawatt-class output power electrical pulses with a flexible frequency in the P and L microwave wavebands have been achieved by photoconductive semiconductor devices.Here,we mainly summarize and review the recent progress of the high-power photonic microwave generation based on the SiC photoconductive semiconductor devices in the linear modulation mode,including the mechanism,system architecture,critical technology,and experimental demonstration of the proposed high-power photonic microwave sources.The outlooks and challenges for the future of multi-channel power synthesis development of higher power photonic microwave using wide bandgap photoconductors are also discussed.
基金supported by China Postdoctoral Science Foundation (Grant No. 20070420070)China Postdoctoral Science Foundation Spe-cially Funded Project and National Basic Research Program of China (Grant No. 973-2007CB411807)
文摘A new simple two-scale model on the polarimetric microwave emission of ocean surface is derived at first, which can be ex-pressed as an integral of weighting functions (M0 and M2) and ocean surface curvature spectrum coefficients (C0 and C2). This provides a simple way to investigate the effect of curvature spectrum on ocean emission. It is found that ocean waves with wavelengths both comparable to and much greater than the electromagnetic wavelength can contribute to the harmonics of ocean surface microwave emission, depending on the magnitude of the ocean surface spectrum in these length scales. Bright-ness temperature predictions differ significantly due to present diverse spectrum models, and thus a study on wave spectrum obtained inversely from brightness temperature measurements is necessary. From the ocean surface radiation data measured by polarimetric microwave radiometer, we derived an ocean wave spectrum with a wider wave number range, using the proposed two-scale model and constrained linear least-squares method. The derived ocean wave spectrum is useful for comparing with present diverse models.
基金funded by the Centre for Innovative Manufacturing in Ultra Precision of the Engineering and Physical Sciences Research Council,UK(Grant No.EP/I033491/1)the Centre for Doctoral Training in Ultra Precision Engineering of the Engineering and Physical Sciences Research Council,UK(Grant No.EP/K503241/1)+2 种基金the Science Foundation Ireland(SFI)(Grant No.15/RP/B3208)Irish Research Council(Grant No.CLNE/2018/1530)the National Natural Science Foundation of China(Grant No.51705462).
文摘Microwave induced plasma torches find wide applications in material and chemical analysis.Investigation of a coaxial electrode microwave induced plasma(CE–MIP)torch is conducted in this study,making it available for glass surface modification and polishing.A dedicated nozzle is designed to inject secondary gases into the main plasma jet.This study details the adaptation of a characterisation process for CE–MIP technology.Microwave spectrum analysis is used to create a polar plot of the microwave energy being emitted from the coaxial electrode,where the microwave energy couples with the gas to generate the plasma jet.Optical emission spectroscopy analysis is also employed to create spatial maps of the photonic intensity distribution within the plasma jet when different additional gases are injected into it.The CE–MIP torch is experimentally tested for surface energy modification on glass where it creates a super-hydrophilic surface.
基金Supported by the National Natural Science Foundation of China(Grant No.60771042)the National Hi-Tech Research and Development Program("863"Project)(Grant No.2007AA12Z159)+2 种基金111Project(Grant No.B07046)SiChuan Excellent Youth Foun-dation(Grant No.08ZQ026-039)Program for New Century Excellent Talents in University of China and Program for Changjiang Scholars
文摘Microwave-induced thermo-acoustic tomography (MITAT) is a promising technique with great potential in biomedical imaging. It has both the high contrast of the microwave imaging and the high resolution of the ultrasound imaging. In this paper, the proportional relationship between the absorbed microwave energy distribution and the induced ultrasound source distribution is derived. Further, the time reversal mirror (TRM) technique based on the pseudo-spectral time domain (PSTD) method is applied to MITAT system. The simulation results show that high contrast and resolution can be achieved by the TRM technique based on PSTD method even for the received signals with very low signal-to-noise ratio (SNR) and the model parameter with random fluctuation.
文摘^(57)Fe Mssbauer spectroscopy was used to study the mechanism and regularity of coal desulfurization by microwave irradiation combined with magnetic-separation and with chemical acid-leaching. The results of phase analyses show that the decomposing reaction of pyrite intrinsic in coal, caused by the selective dielectric heating of microwave electromagnetic energy, FeS_2→Fe_(1-x)S→FeS, consecutively progresses towards the right-hand side with increased irradiation time. The whole process of microwave desulfurization of raw coal consists of the initiation, the promotion, and the saturation stages. The optimum desulfurization efficiency for microwave irradiation combined with magnetic-separation treatment and with chemical acid-leaching treatment can be attained by appropriately controlling the irradiation time to enable the corresponding microwave treatment to lie in the promotion stage and the saturation stage, respectively.
文摘Based on Tian et al. 's theoretical model of microwave scattering, by using the wind wave spectrum suggested by Fung et al. , numerical results of polarized back-scattering were calculated. The quantitative relationships between the calculated backscattering cross section and the environmental parameters, such as wind speeds, azimuthal angles and incidence angles, were studied. Compared with the traditional two-scale scattering model, the results are much more coincident with the observations under the condition of moderate incidence angles, which is very useful to make up for the two-scale model. To make the new calculation model to be used conveniently in the practice, its simplified form was proposed.
文摘Developing a comprehensive model of the early universe that describes events and conditions prior to recombination has proved difficult. Using a new approach, we express Heisenberg’s uncertainty principle in terms of measures and counts of those measures to resolve an expression consisting entirely of counts. The description allows us to resolve explicit values for discrete measures. With these values, we present new expressions describing the earliest epoch and the transition event that initiates expansion. We determine the quantity, age, density, and temperature of the cosmic microwave background (CMB). Moreover, we approach the CMB power spectrum anew, describing each mass/energy distribution, its physical significance, its peak temperature, and the effects of relativity. We do not engage in fitting or modification of the existing laws of physics. The approach is classical and correlates both quantum and cosmological phenomena with descriptive expressions that are measurable, verifiable, and falsifiable.
文摘The Ba_(12)ReNb_(9)O_(36)(Re=Yb,Ce,Tm,Er,Y,Ho,Dy,Gd)ceramics are synthesized by solid-phase reaction method.The phase composition,crystal structure,microstructure,and microwave dielectric properties of the ceramics are investigated by X-ray diffraction,X-ray photoelectron spectroscopy,Scanning electron microscopy and Raman spectrum.The optimal microwave dielectric properties(ε_(r)=37.23,Q×f=36600 GHz,andτ_(f)=34 ppm/℃)are obtained for Ba_(12)YbNb_(9)O_(36) ceramic sintered at 1420℃for 6 h.In this system,the variation of dielectric constant is dominated by polarizability.The Q×f is mainly affected by internal strain/fluctuation of d-spacing.The variation of τ_(f) is related to the temperature coefficient of dielectric constant and the oxygen octahedron distortion.Furthermore,the reduction of Ce^(4+) ions,the relative density,linear thermal expansion coefficient,and the second phase are also important factors affecting microwave dielectric properties.
文摘The experiment results of ultrawide band electromagnetic radiation with DC biased GaAs photoconductive semiconductor switch combining double ridge horn antenna triggered by high repeat frequency femto-second laser pulse are reported.The GaAs switches are insulated by solid multi-layer transparent dielectrics and the distance of two electrodes is 3mm.The electrode material of the switch is ohmic contact through alloy technics with definite proportion of Au/Ge/Ni.This switch and double ridge horn antenna are integrated and the receive antenna is connected with the test instrument.From receiving antenna,ultra fast electrical pulse of 200ps rise time and 500ps pulse width is obtained,the repetition rate of the pulse is about 82MHz and the frequency spectrum is in the range of 4.7MHz~14GHz.The radiation characteristic of the ultrafast electrical pulse is analyzed.