Dehydrating large amounts of sludge produced by sewage treatment plants is difficult.Microwave pretreatment can effectively and significantly improve the dewaterability and hydrogen production of sludge subjected to a...Dehydrating large amounts of sludge produced by sewage treatment plants is difficult.Microwave pretreatment can effectively and significantly improve the dewaterability and hydrogen production of sludge subjected to anaerobic digestion. The aim of this study was to investigate the effects of different microwave conditions on hydrogen production from anaerobic digestion and dewaterability of sludge. Based on an analysis of the electric field distribution, a spiral reactor was designed and a continuous microwave system was built to conduct intermittent and continuous experiments under different conditions. Settling Volume, Capillary Suction Time, particle size, and moisture content of the sludge were measured. The results show that sludge pretreatment in continuous experiments has equally remarkable dehydration performance as in intermittent experiments; the minimum moisture content was 77.29% in the intermittent experiment under a microwave power of 300 W and an exposure time of 60 sec, and that in the continuous experiment was 77.56% under a microwave power of 400 W and an exposure time of 60 sec.The peak measured by Differential Scanning Calorimeter appeared earliest under a microwave power of 600 W and an exposure time of 180 sec. The heat flux at the peak was 4.343 W/g, which is relatively small. This indicates that microwave pretreatment induced desirable effects. The maximum yield of hydrogen production was 7.967% under the conditions of microwave power of 500 W, exposure time of 120 sec, and water bath at 55℃. This research provides a theoretical and experimental basis for the development of a continuous microwave sludge-conditioning system.展开更多
1.Introduction:High power microwave technology background and critical applications High power microwave(HPM)is defined as electromagnetic radia-tion exceeding 1 GW peak power or 1 MW average power within the frequenc...1.Introduction:High power microwave technology background and critical applications High power microwave(HPM)is defined as electromagnetic radia-tion exceeding 1 GW peak power or 1 MW average power within the frequency range of 300 MHz to 300 GHz.This perspective focuses on vacuum electronic device-based HPM sources,which rely on controlled magnetic fields for beam confinement and wave-beam interactions.The fundamental operating principle involves the conversion of kinetic energy from high-energy electron beams into electromagnetic energy through beam-wave interactions.展开更多
In the last decade,space solar power satellites(SSPSs)have been conceived to support net-zero carbon emissions and have attracted considerable attention.Electric energy is transmitted to the ground via a microwave pow...In the last decade,space solar power satellites(SSPSs)have been conceived to support net-zero carbon emissions and have attracted considerable attention.Electric energy is transmitted to the ground via a microwave power beam,a technology known as microwave power transmission(MPT).Due to the vast transmission distance of tens of thousands of kilometers,the power transmitting antenna array must span up to 1 kilometer in diameter.At the same time,the size of the rectifying array on the ground should extend over a few kilometers.This makes the MPT system of SSPSs significantly larger than the existing aerospace engineering system.To design and operate a rational MPT system,comprehensive optimization is required.Taking the space MPT system engineering into consideration,a novel multi-objective optimization function is proposed and further analyzed.The multi-objective optimization problem is modeled mathematically.Beam collection efficiency(BCE)is the primary factor,followed by the thermal management capability.Some tapers,designed to solve the conflict between BCE and the thermal problem,are reviewed.In addition to these two factors,rectenna design complexity is included as a functional factor in the optimization objective.Weight coefficients are assigned to these factors to prioritize them.Radiating planar arrays with different aperture illumination fields are studied,and their performances are compared using the multi-objective optimization function.Transmitting array size,rectifying array size,transmission distance,and transmitted power remaine constant in various cases,ensuring fair comparisons.The analysis results show that the proposed optimization function is effective in optimizing and selecting the MPT system architecture.It is also noted that the multi-objective optimization function can be expanded to include other factors in the future.展开更多
The development of materials with excellent microwave absorption(MWA)and electromagnetic interference(EMI)shielding performances has currently received attention.Herein,mesophase pitch-based carbon foam(MPCF)with 3D i...The development of materials with excellent microwave absorption(MWA)and electromagnetic interference(EMI)shielding performances has currently received attention.Herein,mesophase pitch-based carbon foam(MPCF)with 3D interconnected pore structure was prepared through the high pressure pyrolysis of mesophase coal tar pitch.It is found that the 3D interconnected cellular pores of MPCF facilitate multiple reflections of electromagnetic waves,which results in the minimum reflection loss(RLmin)value of MPCF reaches-37.84 dB with the effective absorption bandwidth(EAB)of 5.44 GHz at a thickness of 2.70 mm,and the total average electromagnetic shielding effectiveness(SE_(T))under 3.00 mm thickness achieves 26.52 dB in X-band.Subsequently,MPCF is activated by KOH to obtain activated carbon foam(A-MPCF).The average SE_(T)of A-MPCF achieves 103.00 dB for abundant nanopores on the pore cell walls,which leads to a transition from the multiple reflections of electromagnetic waves on the walls to diffuse reflection.Unfortunately,the reflection coefficient(R)of A-MPCF increases from 0.78 to 0.90.To reduce the R value,Fe_(3)O_(4)/A-MPCF was fabricated via the in situ growth of nano Fe_(3)O_(4)on A-MPCF.Consequently,the R value of Fe_(3)O_(4)/A-MPCF was reduced from 0.90 to 0.74,whereas the MWA performance was only slightly decreased.This work proposes a simple strategy for simultaneously adjusting MWA and EMI shielding performances of materials.展开更多
BACKGROUND Data comparing the outcomes of hepatocellular carcinoma(HCC)ablation by multibipolar radiofrequency ablation(mbp-RFA)and microwave ablation(MWA)are lacking.This study compares safety and efficacy of the two...BACKGROUND Data comparing the outcomes of hepatocellular carcinoma(HCC)ablation by multibipolar radiofrequency ablation(mbp-RFA)and microwave ablation(MWA)are lacking.This study compares safety and efficacy of the two techniques in treatment-naive HCC.AIM To compare the risk of local tumor progression(LTP)according to the technique;secondary endpoints included technique efficacy rate at one-month,overall survival and major complication rate.METHODS A bi-institutional retrospective analysis of patients undergoing treatment-naive HCC ablation by either technique was performed.Inverse probability of treatment weighting was used to compare the two groups.Mixed effects multivariate Cox regression was applied to identify risk factors for LTP.RESULTS A total of 362 patients(mean age,66.1±6.2 years,308 men)were included,of which 242(323 tumors)treated by mbp-RFA and 120(168 tumors)by MWA.After a median follow-up of 27 months,cumulative LTP was 11.4%after mbp-RFA and 25.2%after MWA.Independent risk factors for LTP at multivariate analysis were MWA(hazard ratio=2.85,P<0.001)and tumor size(hazard ratio=1.08,P<0.001).Two-year LTP-free survival was higher after mbp-RFA than MWA regardless of size(<3 cm:96%vs 87.1%,P<0.01;≥3 cm:87.5%vs 74%,P=0.04).Technique efficacy rate was higher after mbp-RFA(94.1%vs 87.5%,P=0.01).No difference was observed in major complication rate(9.5%vs 7.5%,P=0.59),nor 5-year overall survival(63.6%vs 58.3%,P=0.33).CONCLUSION Mbp-RFA leads to better local tumor control of treatment-naïve HCC than MWA regardless of tumor size and has better primary efficacy,while maintaining a comparable safety profile.展开更多
Designing materials with both structural load-bearing capacity and broadband electromagnetic(EM)wave absorption properties remains a significant challenge.In this work,SiOC/SiC/SiO_(2)composite with gyroid structures ...Designing materials with both structural load-bearing capacity and broadband electromagnetic(EM)wave absorption properties remains a significant challenge.In this work,SiOC/SiC/SiO_(2)composite with gyroid structures were prepared through digital light processing(DLP)3D printing,polymer-derived ceramics(PDCs),chemical vapor infiltration(CVI),and oxidation technologies.The incorporation of the CVISiC phase effectively increases the dissipation capability,while the synergistic interaction between the gyroid structure and SiO_(2)phase significantly improves impedance matching performance.The SiOC/SiC/SiO_(2)composite achieved a minimum reflection loss(RL min)of-62.2 d B at 4.3 mm,and the effective absorption bandwidth(EAB)covered the X-band,with a thickness range of 4.1 mm-4.65 mm.The CST simulation results explain the broadband and low-frequency absorption characteristics,with an EAB of 8.4 GHz(9.6-18 GHz)and an RL min of-21.5 dB at 5 GHz.The excellent EM wave attenuation performance is associated primarily with polarization loss,conduction loss,the gyroid structure's enhancement of multiple reflections and scattering of EM waves,and the resonance effect between the structural units.The SiOC/SiC/SiO_(2)composite also demonstrated strong mechanical properties,with a maximum compressive failure strength of 31.6 MPa in the height direction.This work opens novel prospects for the development of multifunctional structural wave-absorbing materials suitable for broadband microwave absorption and load-bearing properties.展开更多
The emerging new concepts and technologies based on microwave photonics have led to an ever-increasing interest in developing innovative radar systems with a net gain in functionality,bandwidth /resolution,size,mass,c...The emerging new concepts and technologies based on microwave photonics have led to an ever-increasing interest in developing innovative radar systems with a net gain in functionality,bandwidth /resolution,size,mass,complexity and cost when compared with the traditional implementations. This paper describes the techniques developed in the last few years in microwave photonics that might revolutionize the way to design multifunction radar systems,with an emphasis on the recent advances in optoelectronic oscillators( OEOs),arbitrary waveform generation,photonic mixing,phase coding,filtering,beamforming,analog-to-digital conversion,and stable radio-frequency signal transfer. Challenges in implementation of these components and subsystems for meeting the technique requirements of the multifunction radar applications are discussed.展开更多
The kinetics of thedegradation of trace nitrobenzene （NB） by a granular activated carbon （GAC） enhanced microwave （MW）/hydrogen peroxide （H202 ） systemwas studied. Effects of pH, NB initial concentration and t...The kinetics of thedegradation of trace nitrobenzene （NB） by a granular activated carbon （GAC） enhanced microwave （MW）/hydrogen peroxide （H202 ） systemwas studied. Effects of pH, NB initial concentration and tert-butyl alcohol on the removal efficiencywere examined. Itwas found that the reaction rate fitswell to first-order reaction kinetics in the MW/GAC/H202 process. Moreover, GAC greatly enhanced thedegradation rate of NB inwater. Under a given condition （MW power300 W, H202dosage 10 mg/L, pH 6.85 and temperature （60 ± 5）°C）, thedegradation rate of NBwas 0.05214 min 1when4 g/L GACwas added. In general, alkaline pHwas better for NBdegradation; however, the optimum pHwas 8.0 in the tested pH value range of4.0-12.0. At H202dosage of 10 mg/L and GACdosage of4 g/L, the removal of NBwasdecreasedwith increasing initial concentrations of NB, indicating that a low initial concentrationwas beneficial for thedegradation of NB. These results indicated that the MW/GAC/H202 processwas effective for trace NBdegradation inwater. Gas chromatography-mass spectrometry analysis indicated that a hydroxyl radical addition reaction anddehydrogenation reaction enhanced NBdegradation.展开更多
Background: Gold standard for colorectal liver metastases(CRLM) remains hepatic resection(HR). However, patients with severe comorbidities, unresectable or deep-situated resectable CRLM are candidates for ablation. Th...Background: Gold standard for colorectal liver metastases(CRLM) remains hepatic resection(HR). However, patients with severe comorbidities, unresectable or deep-situated resectable CRLM are candidates for ablation. The aim of the study was to compare recurrence rate and survival benefit of the microwave ablation(MWA), radiofrequency ablation(RFA) and HR by conducting the first network meta-analysis. Data sources: Systematic search of the literature was conducted in the electronic databases. Both updated traditional and network meta-analyses were conducted and the results were compared between them. Results: HR cohort demonstrated significantly less local recurrence rate and better 3-and 5-year diseasefree(DFS) and overall survival(OS) compared to MWA and RFA cohorts. HR cohort included significantly younger patients and with significantly lower preoperative carcinoembryonic antigen(CEA) by 10.28 ng/m L compared to RFA cohort. Subgroup analysis of local recurrence and OS of solitary and ≤3 cm CRLMs did not demonstrate any discrepancies when compared with the whole sample. Conclusions: For resectable CRLM the treatment of choice still remains HR. MWA and RFA can be used as a single or adjunct treatment in patients with unresectable CRLM and/or prohibitive comorbidities.展开更多
Double self-adaptive fuzzy PID algorithm-based control strategy was proposed to construct quasi-cascade control system to control the speed of the acid-pickling process of titanium plates and strips. It is very useful...Double self-adaptive fuzzy PID algorithm-based control strategy was proposed to construct quasi-cascade control system to control the speed of the acid-pickling process of titanium plates and strips. It is very useful in overcoming non-linear dynamic behavior, uncertain and time-varying parameters, un-modeled dynamics, and couples between the automatic turbulence control (ATC) and the automatic acid temperature control (AATC) with varying parameters during the operation process. The quasi-cascade control system of inner and outer loop self-adaptive fuzzy PID controller was built, which could effectively control the pickling speed of plates and strips. The simulated results and real application indicate that the plates and strips acid pickling speed control system has good performances of adaptively tracking the parameter variations and anti-disturbances, which ensures the match of acid pickling temperature and turbulence of flowing with acid pickling speed, improving the surface quality of plates and strips acid pickling, and energy efficiency.展开更多
This paper evaluates the microwave instruments onboard the latest Chinese polar-orbiting satellite, Fengyun 3D (FY- 3D). Comparing three months of observations from the Microwave Temperature Sounder 2 (MWTS-2), the Mi...This paper evaluates the microwave instruments onboard the latest Chinese polar-orbiting satellite, Fengyun 3D (FY- 3D). Comparing three months of observations from the Microwave Temperature Sounder 2 (MWTS-2), the Microwave Humidity Sounder 2 (MWHS-2), and the Microwave Radiation Imager (MWRI) to Met Office short-range forecasts, we characterize the instrumental biases, show how those biases have changed with respect to their predecessors onboard FY- 3C, and how they compare to the Advanced Technology Microwave Sounder (ATMS) onboard NOAA-20 and the Global Precipitation Measurement Microwave Imager (GMI). The MWTS-2 global bias is much reduced with respect to its predecessor and compares well to ATMS at equivalent channel frequencies, differing only by 0.36 ± 0.28 K (1σ) on average. A suboptimal averaging of raw digital counts is found to cause an increase in striping noise and an ascending- descending bias. MWHS-2 benefits from a new calibration method improving the 183-GHz humidity channels with respect to its predecessor and biases for these channels are within ± 1.9 K to ATMS. MWRI presents the largest improvements, with reduced global bias and standard deviation with respect to FY-3C;although, spurious, seemingly transient, brightness temperatures have been detected in the observations at 36.5 GHz (vertical polarization). The strong solar-dependent bias that affects the instrument on FY-3C has been reduced to less than 0.2 K on average for FY-3D MWRI. Experiments where radiances from these instruments were assimilated on top of a full global system demonstrated a neutral to positive impact on the forecasts, as well as on the fit to the background of independent instruments.展开更多
Microwave-induced thermoacoustic imaging(TAI)is a noninvasive modality based on the differences in microwave absorption of various biological tissues.TAI has been extensively researched in recent years,and several stu...Microwave-induced thermoacoustic imaging(TAI)is a noninvasive modality based on the differences in microwave absorption of various biological tissues.TAI has been extensively researched in recent years,and several studies have revealed that TAI possesses advantages such as high resolution,high contrast,high imaging depth and fast imaging speed.In this paper,we reviewed the development of the TAI technique,its excitation source,data acquisition system and biomedical applications.It is believed that TAI has great potential applications in biomedical research and clinical study.展开更多
The 6 MW/4.6 GHz lower hybrid current drive （LHCD） system will be set up on the experimental advanced superconducting tokamak （EAST） for achieving a steady-state op- eration. The high power and continuous wave （C...The 6 MW/4.6 GHz lower hybrid current drive （LHCD） system will be set up on the experimental advanced superconducting tokamak （EAST） for achieving a steady-state op- eration. The high power and continuous wave （CW） mode microwave test bench operating at 250 kW/4.6 GHz has already been finished, which can be used to simulate different kinds of high power microwave environments to test microwave components and units for the new LHCD sys- tem. The power control and data acquisition system on the test bench composed of power control, high reflected power protection and data acquisition function is described here in detail. Long- term operation of the test bench showed that the power control and data acquisition system is very stable and reliable.展开更多
MetCoOp is a Nordic collaboration on operational Numerical Weather Prediction based on a common limited-area km-scale ensemble system. The initial states are produced using a 3-dimensional variational data assimilatio...MetCoOp is a Nordic collaboration on operational Numerical Weather Prediction based on a common limited-area km-scale ensemble system. The initial states are produced using a 3-dimensional variational data assimilation scheme utilizing a large amount of observations from conventional in-situ measurements, weather radars, global navigation satellite system, advanced scatterometer data and satellite radiances from various satellite platforms. A version of the forecasting system which is aimed for future operations has been prepared for an enhanced assimilation of microwave radiances. This enhanced data assimilation system will use radiances from the Microwave Humidity Sounder, the Advanced Microwave Sounding Unit-A and the Micro-Wave Humidity Sounder-2 instruments on-board the Metop-C and Fengyun-3 C/D polar orbiting satellites. The implementation process includes channel selection, set-up of an adaptive bias correction procedure, and careful monitoring of data usage and quality control of observations. The benefit of the additional microwave observations in terms of data coverage and impact on analyses, as derived using the degree of freedom of signal approach, is demonstrated. A positive impact on forecast quality is shown, and the effect on the precipitation for a case study is examined. Finally, the role of enhanced data assimilation techniques and adaptions towards nowcasting are discussed.展开更多
Microwave pre-treatment is considered as a promising technique for alleviating cutter wear. This paper introduces a high-power microwave-induced fracturing system for hard rock. The test system consists of a high-powe...Microwave pre-treatment is considered as a promising technique for alleviating cutter wear. This paper introduces a high-power microwave-induced fracturing system for hard rock. The test system consists of a high-power microwave subsystem (100 kW), a true triaxial testing machine, a dynamic monitoring subsystem, and an electromagnetic shielding subsystem. It can realize rapid microwave-induced fracturing, intelligent tuning of impedance, dynamic feedback under strong microwave fields, and active control of microwave parameters by addressing the following issues: the instability and insecurity of the system, the discharge breakdown between coaxial lines during high-power microwave output, and a lack of feedback of rock-microwave response. In this study, microwave-induced surface and borehole fracturing tests under true triaxial stress were carried out. Experimental comparisons imply that high-power microwave irradiation can reduce the fracturing time of hard rock and that the fracture range (160 mm) of a 915-MHz microwave source is about three times that of 2.45 GHz. After microwave-induced borehole fracturing, many tensile cracks occur on the rock surface and in the borehole: the maximum reduction of the P-wave velocity is 12.8%. The test results show that a high-power microwave source of 915 MHz is more conducive to assisting mechanical rock breaking and destressing. The system can promote the development of microwave-assisted rock breaking equipment.展开更多
The study of trace metals in the atmosphere and lake water is important due to their critical effects on humans, aquatic animals and the geochemical balance of ecosystems. The objective of this study was to investigat...The study of trace metals in the atmosphere and lake water is important due to their critical effects on humans, aquatic animals and the geochemical balance of ecosystems. The objective of this study was to investigate the concentration of trace metals in atmospheric and lake water samples during the rainy season （before and after precipitation） between November and December 2015. Typical methods of sample preparation for trace metal determination such as cloud point extraction, solid phase extraction and dispersive liquid- liquid micro-extraction are time-consuming and difficult to perform; therefore, there is a crucial need for development of more effective sample preparation procedure. A convection microwave assisted digestion procedure for extraction of trace metals was developed for use prior to inductively couple plasma-mass spectrometric determination. The result showed that metals like zinc （133.50-419.30 μg/m3） and aluminum （53.58-378.93 μg/m3） had higher concentrations in atmospheric samples as compared to lake samples before precipitation. On the other hand, the concentrations of zinc, aluminum, chromium and arsenic were significantly higher in lake samples after precipitation and lower in atmospheric samples. The relationship between physicochemical parameters （pH and turbidity） and heavy metal concentrations was investigated as well. Furthermore, enrichment factor analysis indicated that anthropogenic sources such as soil dust, biomass burning and fuel combustion influenced the metal concentrations in the atmosphere.展开更多
4-Aryl/alkyl-3,4-dihydro-2(1H)-pyrimidone esters and 5-acetyl-4-aryl/or alkyl-6-methyl- 3, 4-dihydropyrimidin-2(l)-ones were synthesised efficientiy using montmorillonite clay- SmCl3 6H2O system promoted by microwave ...4-Aryl/alkyl-3,4-dihydro-2(1H)-pyrimidone esters and 5-acetyl-4-aryl/or alkyl-6-methyl- 3, 4-dihydropyrimidin-2(l)-ones were synthesised efficientiy using montmorillonite clay- SmCl3 6H2O system promoted by microwave irradiation in solvenfless condition.展开更多
In lower hybrid current drive （LHCD） experiments in HT-7, LH wave coupled to the plasma from 12 klystrons is launched by a phased multi-junction grill. High power microwave reflection or arc, which threatens the kly...In lower hybrid current drive （LHCD） experiments in HT-7, LH wave coupled to the plasma from 12 klystrons is launched by a phased multi-junction grill. High power microwave reflection or arc, which threatens the klystrons, the wave-guide ceramic windows and the vacuum of the tokamak, occur sometimes during the experiments. For the sake of safety, a high power microwave test system to perform simulations was developed. In the test experiments, the klystron and window can be well protected with an optimized microwave monitor and a PIN switch. The layout of the test system and the simulated experiments for HT-7 are described in this paper.展开更多
The impact of assimilating radiance data from the advanced satellite sensor GMI(GPM microwave imager)for typhoon analyses and forecasts was investigated using both a three-dimensional variational(3DVAR)and a hybrid en...The impact of assimilating radiance data from the advanced satellite sensor GMI(GPM microwave imager)for typhoon analyses and forecasts was investigated using both a three-dimensional variational(3DVAR)and a hybrid ensemble-3DVAR method.The interface of assimilating the radiance for the sensor GMI was established in the Weather Research and Forecasting(WRF)model.The GMI radiance data are assimilated for Typhoon Matmo(2014),Typhoon Chan-hom(2015),Typhoon Meranti(2016),and Typhoon Mangkhut(2018)in the Pacific before their landing.The results show that after assimilating the GMI radiance data under clear sky condition with the 3DVAR method,the wind,temperature,and humidity fields are effectively adjusted,leading to improved forecast skills of the typhoon track with GMI radiance assimilation.The hybrid DA method is able to further adjust the location of the typhoon systematically.The improvement of the track forecast is even more obvious for later forecast periods.In addition,water vapor and hydrometeors are enhanced to some extent,especially with the hybrid method.展开更多
In this paper,a coherent transient effect-optical nutation in Bloch form is studied semiclassically in the three-level atomic system driven by a coherent microwave field.The amplitude of the optical nutation signal fi...In this paper,a coherent transient effect-optical nutation in Bloch form is studied semiclassically in the three-level atomic system driven by a coherent microwave field.The amplitude of the optical nutation signal field is obtained.It is found that the signal field,related to the microwave,is the overlap of two slow oscillations instead of one.展开更多
基金supported by a National Natural Science Fund project(No.51104022)teacher team construction Top-notch Youth Project(municipal)(No.PXM2016 014222 000043)
文摘Dehydrating large amounts of sludge produced by sewage treatment plants is difficult.Microwave pretreatment can effectively and significantly improve the dewaterability and hydrogen production of sludge subjected to anaerobic digestion. The aim of this study was to investigate the effects of different microwave conditions on hydrogen production from anaerobic digestion and dewaterability of sludge. Based on an analysis of the electric field distribution, a spiral reactor was designed and a continuous microwave system was built to conduct intermittent and continuous experiments under different conditions. Settling Volume, Capillary Suction Time, particle size, and moisture content of the sludge were measured. The results show that sludge pretreatment in continuous experiments has equally remarkable dehydration performance as in intermittent experiments; the minimum moisture content was 77.29% in the intermittent experiment under a microwave power of 300 W and an exposure time of 60 sec, and that in the continuous experiment was 77.56% under a microwave power of 400 W and an exposure time of 60 sec.The peak measured by Differential Scanning Calorimeter appeared earliest under a microwave power of 600 W and an exposure time of 180 sec. The heat flux at the peak was 4.343 W/g, which is relatively small. This indicates that microwave pretreatment induced desirable effects. The maximum yield of hydrogen production was 7.967% under the conditions of microwave power of 500 W, exposure time of 120 sec, and water bath at 55℃. This research provides a theoretical and experimental basis for the development of a continuous microwave sludge-conditioning system.
文摘1.Introduction:High power microwave technology background and critical applications High power microwave(HPM)is defined as electromagnetic radia-tion exceeding 1 GW peak power or 1 MW average power within the frequency range of 300 MHz to 300 GHz.This perspective focuses on vacuum electronic device-based HPM sources,which rely on controlled magnetic fields for beam confinement and wave-beam interactions.The fundamental operating principle involves the conversion of kinetic energy from high-energy electron beams into electromagnetic energy through beam-wave interactions.
文摘In the last decade,space solar power satellites(SSPSs)have been conceived to support net-zero carbon emissions and have attracted considerable attention.Electric energy is transmitted to the ground via a microwave power beam,a technology known as microwave power transmission(MPT).Due to the vast transmission distance of tens of thousands of kilometers,the power transmitting antenna array must span up to 1 kilometer in diameter.At the same time,the size of the rectifying array on the ground should extend over a few kilometers.This makes the MPT system of SSPSs significantly larger than the existing aerospace engineering system.To design and operate a rational MPT system,comprehensive optimization is required.Taking the space MPT system engineering into consideration,a novel multi-objective optimization function is proposed and further analyzed.The multi-objective optimization problem is modeled mathematically.Beam collection efficiency(BCE)is the primary factor,followed by the thermal management capability.Some tapers,designed to solve the conflict between BCE and the thermal problem,are reviewed.In addition to these two factors,rectenna design complexity is included as a functional factor in the optimization objective.Weight coefficients are assigned to these factors to prioritize them.Radiating planar arrays with different aperture illumination fields are studied,and their performances are compared using the multi-objective optimization function.Transmitting array size,rectifying array size,transmission distance,and transmitted power remaine constant in various cases,ensuring fair comparisons.The analysis results show that the proposed optimization function is effective in optimizing and selecting the MPT system architecture.It is also noted that the multi-objective optimization function can be expanded to include other factors in the future.
基金Supported by the National Natural Science Foundation of China(22378181).
文摘The development of materials with excellent microwave absorption(MWA)and electromagnetic interference(EMI)shielding performances has currently received attention.Herein,mesophase pitch-based carbon foam(MPCF)with 3D interconnected pore structure was prepared through the high pressure pyrolysis of mesophase coal tar pitch.It is found that the 3D interconnected cellular pores of MPCF facilitate multiple reflections of electromagnetic waves,which results in the minimum reflection loss(RLmin)value of MPCF reaches-37.84 dB with the effective absorption bandwidth(EAB)of 5.44 GHz at a thickness of 2.70 mm,and the total average electromagnetic shielding effectiveness(SE_(T))under 3.00 mm thickness achieves 26.52 dB in X-band.Subsequently,MPCF is activated by KOH to obtain activated carbon foam(A-MPCF).The average SE_(T)of A-MPCF achieves 103.00 dB for abundant nanopores on the pore cell walls,which leads to a transition from the multiple reflections of electromagnetic waves on the walls to diffuse reflection.Unfortunately,the reflection coefficient(R)of A-MPCF increases from 0.78 to 0.90.To reduce the R value,Fe_(3)O_(4)/A-MPCF was fabricated via the in situ growth of nano Fe_(3)O_(4)on A-MPCF.Consequently,the R value of Fe_(3)O_(4)/A-MPCF was reduced from 0.90 to 0.74,whereas the MWA performance was only slightly decreased.This work proposes a simple strategy for simultaneously adjusting MWA and EMI shielding performances of materials.
文摘BACKGROUND Data comparing the outcomes of hepatocellular carcinoma(HCC)ablation by multibipolar radiofrequency ablation(mbp-RFA)and microwave ablation(MWA)are lacking.This study compares safety and efficacy of the two techniques in treatment-naive HCC.AIM To compare the risk of local tumor progression(LTP)according to the technique;secondary endpoints included technique efficacy rate at one-month,overall survival and major complication rate.METHODS A bi-institutional retrospective analysis of patients undergoing treatment-naive HCC ablation by either technique was performed.Inverse probability of treatment weighting was used to compare the two groups.Mixed effects multivariate Cox regression was applied to identify risk factors for LTP.RESULTS A total of 362 patients(mean age,66.1±6.2 years,308 men)were included,of which 242(323 tumors)treated by mbp-RFA and 120(168 tumors)by MWA.After a median follow-up of 27 months,cumulative LTP was 11.4%after mbp-RFA and 25.2%after MWA.Independent risk factors for LTP at multivariate analysis were MWA(hazard ratio=2.85,P<0.001)and tumor size(hazard ratio=1.08,P<0.001).Two-year LTP-free survival was higher after mbp-RFA than MWA regardless of size(<3 cm:96%vs 87.1%,P<0.01;≥3 cm:87.5%vs 74%,P=0.04).Technique efficacy rate was higher after mbp-RFA(94.1%vs 87.5%,P=0.01).No difference was observed in major complication rate(9.5%vs 7.5%,P=0.59),nor 5-year overall survival(63.6%vs 58.3%,P=0.33).CONCLUSION Mbp-RFA leads to better local tumor control of treatment-naïve HCC than MWA regardless of tumor size and has better primary efficacy,while maintaining a comparable safety profile.
基金financially supported by National Natural Science Foundation of China(Grant Nos.12141203,52202083,W2421013)the Natural Science Foundation Project of Shaanxi Province(Grant No.2024JC-YBMS-450)+1 种基金the Sichuan Science and Technology Program(Grant No.2024YFHZ0265)the Open Project of High-end Equipment Advanced Materials and Manufacturing Technology Laboratory(Grant No.2023KFKT0005)。
文摘Designing materials with both structural load-bearing capacity and broadband electromagnetic(EM)wave absorption properties remains a significant challenge.In this work,SiOC/SiC/SiO_(2)composite with gyroid structures were prepared through digital light processing(DLP)3D printing,polymer-derived ceramics(PDCs),chemical vapor infiltration(CVI),and oxidation technologies.The incorporation of the CVISiC phase effectively increases the dissipation capability,while the synergistic interaction between the gyroid structure and SiO_(2)phase significantly improves impedance matching performance.The SiOC/SiC/SiO_(2)composite achieved a minimum reflection loss(RL min)of-62.2 d B at 4.3 mm,and the effective absorption bandwidth(EAB)covered the X-band,with a thickness range of 4.1 mm-4.65 mm.The CST simulation results explain the broadband and low-frequency absorption characteristics,with an EAB of 8.4 GHz(9.6-18 GHz)and an RL min of-21.5 dB at 5 GHz.The excellent EM wave attenuation performance is associated primarily with polarization loss,conduction loss,the gyroid structure's enhancement of multiple reflections and scattering of EM waves,and the resonance effect between the structural units.The SiOC/SiC/SiO_(2)composite also demonstrated strong mechanical properties,with a maximum compressive failure strength of 31.6 MPa in the height direction.This work opens novel prospects for the development of multifunctional structural wave-absorbing materials suitable for broadband microwave absorption and load-bearing properties.
基金Supported in part by the National Basic Research Program of China(2012CB315705)the Natural Science Foundation of Jiangsu Province(BK2012031,BK2012381)+1 种基金the National Natural Science Foundation of China(61201048,61107063)the Fundamental Research Funds for the Central Universities
文摘The emerging new concepts and technologies based on microwave photonics have led to an ever-increasing interest in developing innovative radar systems with a net gain in functionality,bandwidth /resolution,size,mass,complexity and cost when compared with the traditional implementations. This paper describes the techniques developed in the last few years in microwave photonics that might revolutionize the way to design multifunction radar systems,with an emphasis on the recent advances in optoelectronic oscillators( OEOs),arbitrary waveform generation,photonic mixing,phase coding,filtering,beamforming,analog-to-digital conversion,and stable radio-frequency signal transfer. Challenges in implementation of these components and subsystems for meeting the technique requirements of the multifunction radar applications are discussed.
基金supported by the National Natural Science Foundation of China(No.51268008,21207024)the Key Project of Chinese Ministry of Education(No.210170,JiaoJiSi[2010]114)+1 种基金the Program for Excellent Talentsin the Guangxi Higher Education Institutions(No.Gui-JiaoRen[2010]65)the Guangxi Scientific Research and Technological Development Plan(No.GuiKeZhuan1298009-17)
文摘The kinetics of thedegradation of trace nitrobenzene （NB） by a granular activated carbon （GAC） enhanced microwave （MW）/hydrogen peroxide （H202 ） systemwas studied. Effects of pH, NB initial concentration and tert-butyl alcohol on the removal efficiencywere examined. Itwas found that the reaction rate fitswell to first-order reaction kinetics in the MW/GAC/H202 process. Moreover, GAC greatly enhanced thedegradation rate of NB inwater. Under a given condition （MW power300 W, H202dosage 10 mg/L, pH 6.85 and temperature （60 ± 5）°C）, thedegradation rate of NBwas 0.05214 min 1when4 g/L GACwas added. In general, alkaline pHwas better for NBdegradation; however, the optimum pHwas 8.0 in the tested pH value range of4.0-12.0. At H202dosage of 10 mg/L and GACdosage of4 g/L, the removal of NBwasdecreasedwith increasing initial concentrations of NB, indicating that a low initial concentrationwas beneficial for thedegradation of NB. These results indicated that the MW/GAC/H202 processwas effective for trace NBdegradation inwater. Gas chromatography-mass spectrometry analysis indicated that a hydroxyl radical addition reaction anddehydrogenation reaction enhanced NBdegradation.
文摘Background: Gold standard for colorectal liver metastases(CRLM) remains hepatic resection(HR). However, patients with severe comorbidities, unresectable or deep-situated resectable CRLM are candidates for ablation. The aim of the study was to compare recurrence rate and survival benefit of the microwave ablation(MWA), radiofrequency ablation(RFA) and HR by conducting the first network meta-analysis. Data sources: Systematic search of the literature was conducted in the electronic databases. Both updated traditional and network meta-analyses were conducted and the results were compared between them. Results: HR cohort demonstrated significantly less local recurrence rate and better 3-and 5-year diseasefree(DFS) and overall survival(OS) compared to MWA and RFA cohorts. HR cohort included significantly younger patients and with significantly lower preoperative carcinoembryonic antigen(CEA) by 10.28 ng/m L compared to RFA cohort. Subgroup analysis of local recurrence and OS of solitary and ≤3 cm CRLMs did not demonstrate any discrepancies when compared with the whole sample. Conclusions: For resectable CRLM the treatment of choice still remains HR. MWA and RFA can be used as a single or adjunct treatment in patients with unresectable CRLM and/or prohibitive comorbidities.
基金Project(51090385) supported by the National Natural Science Foundation of ChinaProject(2001IB001) supported by Yunnan Provincial Science and Technology Fund, China
文摘Double self-adaptive fuzzy PID algorithm-based control strategy was proposed to construct quasi-cascade control system to control the speed of the acid-pickling process of titanium plates and strips. It is very useful in overcoming non-linear dynamic behavior, uncertain and time-varying parameters, un-modeled dynamics, and couples between the automatic turbulence control (ATC) and the automatic acid temperature control (AATC) with varying parameters during the operation process. The quasi-cascade control system of inner and outer loop self-adaptive fuzzy PID controller was built, which could effectively control the pickling speed of plates and strips. The simulated results and real application indicate that the plates and strips acid pickling speed control system has good performances of adaptively tracking the parameter variations and anti-disturbances, which ensures the match of acid pickling temperature and turbulence of flowing with acid pickling speed, improving the surface quality of plates and strips acid pickling, and energy efficiency.
基金This work was supported by the UK-China Research&Innovation Partnership Fund through the Met Office Climate Science for Service Partnership(CSSP)China as part of the Newton Fund.
文摘This paper evaluates the microwave instruments onboard the latest Chinese polar-orbiting satellite, Fengyun 3D (FY- 3D). Comparing three months of observations from the Microwave Temperature Sounder 2 (MWTS-2), the Microwave Humidity Sounder 2 (MWHS-2), and the Microwave Radiation Imager (MWRI) to Met Office short-range forecasts, we characterize the instrumental biases, show how those biases have changed with respect to their predecessors onboard FY- 3C, and how they compare to the Advanced Technology Microwave Sounder (ATMS) onboard NOAA-20 and the Global Precipitation Measurement Microwave Imager (GMI). The MWTS-2 global bias is much reduced with respect to its predecessor and compares well to ATMS at equivalent channel frequencies, differing only by 0.36 ± 0.28 K (1σ) on average. A suboptimal averaging of raw digital counts is found to cause an increase in striping noise and an ascending- descending bias. MWHS-2 benefits from a new calibration method improving the 183-GHz humidity channels with respect to its predecessor and biases for these channels are within ± 1.9 K to ATMS. MWRI presents the largest improvements, with reduced global bias and standard deviation with respect to FY-3C;although, spurious, seemingly transient, brightness temperatures have been detected in the observations at 36.5 GHz (vertical polarization). The strong solar-dependent bias that affects the instrument on FY-3C has been reduced to less than 0.2 K on average for FY-3D MWRI. Experiments where radiances from these instruments were assimilated on top of a full global system demonstrated a neutral to positive impact on the forecasts, as well as on the fit to the background of independent instruments.
基金the National Natural Science Foundation of China(61627827,61331001,81630046,91539127)the Science and Technology Planning Project of Guangdong Province,China(2015B020233016,2014B020215003,2014A020215031,2017A020215135)+3 种基金the Distinguished Young Teacher Project in Higher Education of Guangdong,China(YQ2015049)the Science and Technology Youth Talent for Special Project of Guangdong,China(2015TQ01X882)Young Teachers Scienti¯c Research Cultivating Fund of South China Normal University(16KJ05)China Postdoctoral Science Foundation(2017M610533).
文摘Microwave-induced thermoacoustic imaging(TAI)is a noninvasive modality based on the differences in microwave absorption of various biological tissues.TAI has been extensively researched in recent years,and several studies have revealed that TAI possesses advantages such as high resolution,high contrast,high imaging depth and fast imaging speed.In this paper,we reviewed the development of the TAI technique,its excitation source,data acquisition system and biomedical applications.It is believed that TAI has great potential applications in biomedical research and clinical study.
基金supported by National Magnetic Confinement Fusion Science Program of China(No.2010GB105001)
文摘The 6 MW/4.6 GHz lower hybrid current drive （LHCD） system will be set up on the experimental advanced superconducting tokamak （EAST） for achieving a steady-state op- eration. The high power and continuous wave （CW） mode microwave test bench operating at 250 kW/4.6 GHz has already been finished, which can be used to simulate different kinds of high power microwave environments to test microwave components and units for the new LHCD sys- tem. The power control and data acquisition system on the test bench composed of power control, high reflected power protection and data acquisition function is described here in detail. Long- term operation of the test bench showed that the power control and data acquisition system is very stable and reliable.
文摘MetCoOp is a Nordic collaboration on operational Numerical Weather Prediction based on a common limited-area km-scale ensemble system. The initial states are produced using a 3-dimensional variational data assimilation scheme utilizing a large amount of observations from conventional in-situ measurements, weather radars, global navigation satellite system, advanced scatterometer data and satellite radiances from various satellite platforms. A version of the forecasting system which is aimed for future operations has been prepared for an enhanced assimilation of microwave radiances. This enhanced data assimilation system will use radiances from the Microwave Humidity Sounder, the Advanced Microwave Sounding Unit-A and the Micro-Wave Humidity Sounder-2 instruments on-board the Metop-C and Fengyun-3 C/D polar orbiting satellites. The implementation process includes channel selection, set-up of an adaptive bias correction procedure, and careful monitoring of data usage and quality control of observations. The benefit of the additional microwave observations in terms of data coverage and impact on analyses, as derived using the degree of freedom of signal approach, is demonstrated. A positive impact on forecast quality is shown, and the effect on the precipitation for a case study is examined. Finally, the role of enhanced data assimilation techniques and adaptions towards nowcasting are discussed.
基金support from the Na-tional Natural Science Foundation of China(Grant No.41827806)the liaoning Revitalization Talent Program of China(Grant No.XLYCYSZX1902).
文摘Microwave pre-treatment is considered as a promising technique for alleviating cutter wear. This paper introduces a high-power microwave-induced fracturing system for hard rock. The test system consists of a high-power microwave subsystem (100 kW), a true triaxial testing machine, a dynamic monitoring subsystem, and an electromagnetic shielding subsystem. It can realize rapid microwave-induced fracturing, intelligent tuning of impedance, dynamic feedback under strong microwave fields, and active control of microwave parameters by addressing the following issues: the instability and insecurity of the system, the discharge breakdown between coaxial lines during high-power microwave output, and a lack of feedback of rock-microwave response. In this study, microwave-induced surface and borehole fracturing tests under true triaxial stress were carried out. Experimental comparisons imply that high-power microwave irradiation can reduce the fracturing time of hard rock and that the fracture range (160 mm) of a 915-MHz microwave source is about three times that of 2.45 GHz. After microwave-induced borehole fracturing, many tensile cracks occur on the rock surface and in the borehole: the maximum reduction of the P-wave velocity is 12.8%. The test results show that a high-power microwave source of 915 MHz is more conducive to assisting mechanical rock breaking and destressing. The system can promote the development of microwave-assisted rock breaking equipment.
基金supported by the Universiti Tunku Abdul Rahman under Universiti Research Grant(No.IPSR/RMC/UTARRF/C1-13/G03)
文摘The study of trace metals in the atmosphere and lake water is important due to their critical effects on humans, aquatic animals and the geochemical balance of ecosystems. The objective of this study was to investigate the concentration of trace metals in atmospheric and lake water samples during the rainy season （before and after precipitation） between November and December 2015. Typical methods of sample preparation for trace metal determination such as cloud point extraction, solid phase extraction and dispersive liquid- liquid micro-extraction are time-consuming and difficult to perform; therefore, there is a crucial need for development of more effective sample preparation procedure. A convection microwave assisted digestion procedure for extraction of trace metals was developed for use prior to inductively couple plasma-mass spectrometric determination. The result showed that metals like zinc （133.50-419.30 μg/m3） and aluminum （53.58-378.93 μg/m3） had higher concentrations in atmospheric samples as compared to lake samples before precipitation. On the other hand, the concentrations of zinc, aluminum, chromium and arsenic were significantly higher in lake samples after precipitation and lower in atmospheric samples. The relationship between physicochemical parameters （pH and turbidity） and heavy metal concentrations was investigated as well. Furthermore, enrichment factor analysis indicated that anthropogenic sources such as soil dust, biomass burning and fuel combustion influenced the metal concentrations in the atmosphere.
文摘4-Aryl/alkyl-3,4-dihydro-2(1H)-pyrimidone esters and 5-acetyl-4-aryl/or alkyl-6-methyl- 3, 4-dihydropyrimidin-2(l)-ones were synthesised efficientiy using montmorillonite clay- SmCl3 6H2O system promoted by microwave irradiation in solvenfless condition.
文摘In lower hybrid current drive （LHCD） experiments in HT-7, LH wave coupled to the plasma from 12 klystrons is launched by a phased multi-junction grill. High power microwave reflection or arc, which threatens the klystrons, the wave-guide ceramic windows and the vacuum of the tokamak, occur sometimes during the experiments. For the sake of safety, a high power microwave test system to perform simulations was developed. In the test experiments, the klystron and window can be well protected with an optimized microwave monitor and a PIN switch. The layout of the test system and the simulated experiments for HT-7 are described in this paper.
基金the Chinese National Natural Science Foundation of China(G41805016)the Chinese National Key R&D Program of China(2018YFC1506404)+3 种基金the Chinese National Natural Science Founda-tion of China(G41805070)the Chinese National Key R&D Program of China(2018YFC1506603)the research project of Heavy Rain and Drought-Flood Disasters in Plateau and Basin Key Laboratory of Sichuan Province in China(SZKT201901,SZKT201904)the research project of the Institute of Atmospheric Environment,China Meteorological Administration,Shenyang in China(2020SYIAE07,2020SYIAE02)。
文摘The impact of assimilating radiance data from the advanced satellite sensor GMI(GPM microwave imager)for typhoon analyses and forecasts was investigated using both a three-dimensional variational(3DVAR)and a hybrid ensemble-3DVAR method.The interface of assimilating the radiance for the sensor GMI was established in the Weather Research and Forecasting(WRF)model.The GMI radiance data are assimilated for Typhoon Matmo(2014),Typhoon Chan-hom(2015),Typhoon Meranti(2016),and Typhoon Mangkhut(2018)in the Pacific before their landing.The results show that after assimilating the GMI radiance data under clear sky condition with the 3DVAR method,the wind,temperature,and humidity fields are effectively adjusted,leading to improved forecast skills of the typhoon track with GMI radiance assimilation.The hybrid DA method is able to further adjust the location of the typhoon systematically.The improvement of the track forecast is even more obvious for later forecast periods.In addition,water vapor and hydrometeors are enhanced to some extent,especially with the hybrid method.
文摘In this paper,a coherent transient effect-optical nutation in Bloch form is studied semiclassically in the three-level atomic system driven by a coherent microwave field.The amplitude of the optical nutation signal field is obtained.It is found that the signal field,related to the microwave,is the overlap of two slow oscillations instead of one.
