Passive jamming is believed to have very good potential in countermeasure community.In this paper,a passive angular blinking jamming method based on electronically controlled corner reflectors is proposed.The amplitud...Passive jamming is believed to have very good potential in countermeasure community.In this paper,a passive angular blinking jamming method based on electronically controlled corner reflectors is proposed.The amplitude of the incident wave can be modulated by switching the corner reflector between the penetration state and the reflection state,and the ensemble of multiple corner reflectors with towing rope can result in complex angle decoying effects.Dependency of the decoying effect on corner reflectors’radar cross section and positions are analyzed and simulated.Results show that the angle measured by a monopulse radar can be significantly interfered by this method while the automatic tracking is employed.展开更多
The wet oxidation of AlGaAs with high Al content in a distributed Bragg reflectors （DBR） is studied by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. Some voids distribute along t...The wet oxidation of AlGaAs with high Al content in a distributed Bragg reflectors （DBR） is studied by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. Some voids distribute along the oxide/GaAs interfaces due to the stress induced by the wet oxidation of the AlGaAs layers. These voids decrease the shrinkage of the Al2O3 layers to 8% instead of the theoretical 20% when compared to the unoxidized AlGaAs layers. With the extension of oxidation time, the reactants are more completely transported to the front interface and the products are more completely transported out along the porous interfaces. As a result,the oxide quality is better.展开更多
Many mound-shaped reflectors with different features and shapes are evident in the Upper Member of the Meishan Formation from seismic profiles taken in the deep-water area of the Southern Qiongdongnan Basin.Based on t...Many mound-shaped reflectors with different features and shapes are evident in the Upper Member of the Meishan Formation from seismic profiles taken in the deep-water area of the Southern Qiongdongnan Basin.Based on the drilling,2 D and 3 D seismic data from the study area,descriptions of the seismic reflection characteristics as well as the geometric shape,wave impedance inversion,analogy and comparative analyses are carried out.Taken in conjunction with research on the paleo structure and paleo sedimentary background,we consider that the mound-shaped seismic reflectors are distributed in the Southern Slop belt and the Southern High-rise of the Qiongdongnan Basin,which can be subdivided into three types:reefs,contourite mounds and magmatic diapirs.The first type,reefs,includes patch reefs,platform marginal reefs and pinnacle reefs.Patch reefs present mound-shaped seismic facies with medium frequency and a moderately strong amplitude,being distributed at the uplift of the fault control platform on the Southern Slop belt.The platform marginal reefs have flat mound-shaped seismic facies with strong amplitude and medium frequency,developing at the margin of the carbonate platform in the Southern High-rise.The pinnacle reefs have mound-shaped seismic facies with strong amplitude and medium frequency and are developed on an isolated volcanic cone.The boundaries between individual reefs are clear on the seismic section,with reef ridge and reef ditch developed,the phenomenon of’front product’being visible within,two-way superelevation between wings is developed and they exist visibly as mounds in any viewed direction of the crosssection.They are slightly asymmetrical in the direction perpendicular to the paleodepth the reef body being steep near the deep-water side,while being gentle near the shallow water side.The wave impedance of a patch reef is about 7 kg/m^(3)×m/s,while the wave impedance of a platform marginal reef is about 7.5 kg/m^(3)×m/s.The second type-contourite moundsare mainly developed under the slope break of the southern slope fault control platform’s edge.They are subdivided into two types:conical and flat.The former has mound-shaped seismic facies with medium-strong amplitude and low frequency,the latter having mound-shaped seismic facies with medium amplitude and low frequency.The internal texture of the mounds is not clear on the seismic section,with the boundaries between contourite mounds being blurred.They are mound-shaped only in cross-section,being banded in the extending direction.The upper surface of a single contourite mound is relatively gentle near the deep-water side,while being steep near the shallow water area.The wave impedance of contourite mounds is about 5.8 kg/m^(3)×m/s,which is speculated to represent a marly to calcareous clastic deposit.The third type is the magmatic diapir,which has’roots’.They have a dome-shaped upper boundary,are bottomless,with a chaotic interior.They penetrated multiple formations,opening towards the base.There are two major accumulation assemblages of reefs,one is the platform margin reef accumulation assemblage with distant source rocks and long-distance migration through an unconformity surface in the Southern High-rise,the other is the patch reef accumulation assemblage with twin sources and short distance migration through faults in the Southern Slop belt near the Central Depression zone.The latter is the main exploration targets at present.There are contourite mound accumulation assemblages with nearby source rocks and short distance vertical migration through faults,which are potentially important targets.The magmatic diapirs pierce the overlying strata and form good hydrocarbon traps and migration pathways,thus representing potential prospecting targets.展开更多
Passive intermodulation（PIM） has gradually become a serious electromagnetic interference due to the development of high-power and high-sensitivity RF/microwave communication systems, especially large deployable mesh...Passive intermodulation（PIM） has gradually become a serious electromagnetic interference due to the development of high-power and high-sensitivity RF/microwave communication systems, especially large deployable mesh reflector antennas. This paper proposes a field-circuit coupling method to analyze the PIM level of mesh reflectors. With the existence of many metal–metal（MM） contacts in mesh reflectors, the contact nonlinearity becomes the main reason for PIM generation. To analyze these potential PIM sources, an equivalent circuit model including nonlinear components is constructed to model a single MM contact so that the transient current through the MM contact point induced by incident electromagnetic waves can be calculated. Taking the electric current as a new electromagnetic wave source, the far-field scattering can be obtained by the use of electromagnetic numerical methods or the communication link method. Finally, a comparison between simulation and experimental results is illustrated to verify the validity of the proposed method.展开更多
Seismic studies of the crustal structure beneath the Three Gorges Reservoir（TGR） region in Central China have been limited by the sparse and uneven distribution of seismic stations.To in-crease the station coverage,...Seismic studies of the crustal structure beneath the Three Gorges Reservoir（TGR） region in Central China have been limited by the sparse and uneven distribution of seismic stations.To in-crease the station coverage,we made three deployments of a mobile seismologic array in the TGR re-gion during the three summers from 2008 to 2010.Here we present interpretations along a west-east profile through the central TGR region based on new seismic waveform data and a velocity model con-strained by regional earthquake data.Two strong mid-crustal reflection interfaces at depths around 10 and 20 km are seen under the TGR.The shallow reflector defines the bottom of the Zigui（秭归） basin.The new waveform data show that the amplitude of the Moho reflection is quite weak,and beneath the Moho,there is a strong reflector around 54-km depth.It is likely that in the TGR region,the Moho is a gradient rather than a sharp boundary.We speculate that the gradient Moho and the 54-km-deep re-flector in the upper mantle in the TGR region may be by-products of the Qinling（秦岭）-Dabie（大别） orogen.展开更多
Thermal neutron albedo has been investigated for different thicknesses of mono-material and bi-material reflectors. An equation has been obtained for a bi-material reflector by considering the neutron diffusion equati...Thermal neutron albedo has been investigated for different thicknesses of mono-material and bi-material reflectors. An equation has been obtained for a bi-material reflector by considering the neutron diffusion equation. The bi-material reflector consists of binary combinations of water, graphite, lead, and polyethylene. An experimental measurement of thermal neutron albedo has also been conducted for mono-material and bi-material reflectors by using a^(241) Am–Be(5.2 Ci) neutron source and a BF3 detector. The maximum value of thermal neutron albedo was obtained for a polyethylene–water combination(0.95 ± 0.02).展开更多
As the signal reflected by the corner-cube reflector arrays is very weak and easily submerged during the full moon,we analyze the influence of the thermal effect of corner-cube reflector arrays on the intensity of lun...As the signal reflected by the corner-cube reflector arrays is very weak and easily submerged during the full moon,we analyze the influence of the thermal effect of corner-cube reflector arrays on the intensity of lunar laser ranging echo.Laser ranging measurements during the penumbra lunar eclipse verify suspected thermal deformation in the Lunakhod 2 reflectors.Signal levels vary over two orders of magnitude as the penumbra eclipse progresses.This can be explained by the change in the dihedral angle of the corner-cube reflectors caused by the temperature.The results show that when the dihedral angle errors reach 1,the energy is reduced by 100 times compared with the ideal corner-cube reflector.In the experiment,our findings suggest that when the corner-cube reflector arrays enter the penumbra of the earth,the effective echo signal level which reaches 0.18 photons/s far exceeds the historical level of the full moon.However,11 minutes after the penumbra lunar eclipse,the effective echo rate of Lunakhod 2 will drop two orders of magnitude.The mechanism can explain the acute signal deficit observed at full moon.展开更多
Metallic nanotextured reflectors have been widely used in light emitting diodes(LEDs) to enhance the light extraction efficiency. However, the light absorption loss for the metallic reflectors with nanotexture structu...Metallic nanotextured reflectors have been widely used in light emitting diodes(LEDs) to enhance the light extraction efficiency. However, the light absorption loss for the metallic reflectors with nanotexture structure is often neglected. Here, the influence of absorption loss of metallic nanotextured reflectors on the LED optoelectronic properties were studied. Two commonly used metal reflectors Ag and Al were applied to green GaN-based LEDs. By applying a Ag nanotextured reflector, the light output power of the LEDs was enhanced by 78% due to the improved light extraction. For an Al nanotextured reflector, however,only a 6% enhancement of the light output power was achieved. By analyzing the metal absorption using finite-difference timedomain(FDTD) and the metal reflectivity spectrum, it is shown that the surface plasmon(SP) intrinsic absorption of metallic reflectors with nanotexture structure play an important role. This finding will aid the design of the high-performance metal nanotextured reflectors and optoelectronics devices.展开更多
Different aluminum-doped ZnO （AZO）/metal composite thin films, including AZO/Ag/Al, AZO/Ag/nickelchromium alloy （NiCr）, and AZO/Ag/NiCr/Al, are utilized as the back reflectors of p-i-n amorphous silicon germanium ...Different aluminum-doped ZnO （AZO）/metal composite thin films, including AZO/Ag/Al, AZO/Ag/nickelchromium alloy （NiCr）, and AZO/Ag/NiCr/Al, are utilized as the back reflectors of p-i-n amorphous silicon germanium thin film solar cells. NiCr is used as diffusion barrier layer between Ag and Al to prevent mutual diffusion, which increases the short circuit current density of solar cell. NiCr and NiCr/AI layers are used as protective layers of Ag layer against oxidation and sulfurization, the higher efficiency of solar cell is achieved. The experimental results show that the performance of a-SiGe solar cell with AZO/Ag/NiCr/Al back reflector is best. The initial conversion efficiency is achieved to be 8.05%.展开更多
New types of Bragg reflectors, multilayered periodic structures, based on alternating left-handed transmission line (LHTL) and right-handed transmission line (RHTL) are proposed. These new structures based on ideal mi...New types of Bragg reflectors, multilayered periodic structures, based on alternating left-handed transmission line (LHTL) and right-handed transmission line (RHTL) are proposed. These new structures based on ideal microstrip TLs and L-C lumped elements, are designed and analyzed. We report on unusual narrow transmission bands in such kind of structures. In such multilayered structures both Bragg reflectance and the Fabry-Perot resonance exist and the phenomenon of unusual transmission is a result of competition between these two transmission effects, in which the Fabry-Perot resonance is dominant. According to our simulation results we find that this unusual transmission property exits no matter if the electrical length of the LHTL layer cancels the electrical length of the RHTL layer or not.展开更多
Tunable and switchable Ba 0.5 Sr 0.5 TiO 3 film bulk acoustic resonators（FBARs） based on SiO 2 /Mo Bragg reflectors are explored,which can withstand high temperature for the deposition of Ba x Sr 1 x TiO 3（BST） fi...Tunable and switchable Ba 0.5 Sr 0.5 TiO 3 film bulk acoustic resonators（FBARs） based on SiO 2 /Mo Bragg reflectors are explored,which can withstand high temperature for the deposition of Ba x Sr 1 x TiO 3（BST） films at 800 C.The dc bias-dependent resonance may be attributed to the piezoelectricity of the BST film induced by an electrostrictive effect.The series resonant frequency is strongly dc bias-dependent and shifts downwards with dc bias increasing,while the parallel resonant frequency is only weakly dc bias-dependent and slightly shifts upwards at low dc bias（ 45 V） while downwards at higher dc bias.The calculated relative tunability of shifts at series resonance frequency is around 2.3% and the electromechanical coupling coefficient is up to approximately 8.09% at 60-V dc bias,which can be comparable to AlN FBARs.This suggests that a high-quality tunable BST FBAR device can be achieved through the use of molybdenum（Mo） as the high acoustic impedance layer in a Bragg reflector,which not only provides excellent acoustic isolation from the substrate,but also improves the crystallinity of BST films withstanding higher deposition temperature.展开更多
In this study, a theoretical analysis of a solar field augmented by a fixed reflector placed in the front between the top of the preceding row and the bottom of the succeeding row is presented. An analytical model has...In this study, a theoretical analysis of a solar field augmented by a fixed reflector placed in the front between the top of the preceding row and the bottom of the succeeding row is presented. An analytical model has been developed and used to estimate the solar irradiation. The analytical model is based on the anisotropic sky model, assuming an infinite length of collector and reflector rows. A simulation has been carried out in order to figure out the behavior of the solar field and to find the optimum design parameters of the solar field leading to a maximum solar energy augmentation. The results obtained are depicted synoptically as a relationship between the solar field design parameters and the latitude angle, and this presentation enables us to determine the optimum design parameters in order to achieve the intended percentage improvement of solar radiation incident on the solar field rows at any location on the Northern hemisphere, which presents the novelty of this research. Also we have introduced a new parameter named “the effective height of the collector”, which presents the portion of the collector’s height illuminated by the reflector. This parameter is very important especially in case of PV solar fields, because it determines the domain of the concentrated solar energy over the surface of the PV panel.展开更多
The aim of this research is to find the best way to take advantage of solar radiation in the lighting of sites to reduce reliance on electric power So In this paper, design and implementation of a pipe lamps contain o...The aim of this research is to find the best way to take advantage of solar radiation in the lighting of sites to reduce reliance on electric power So In this paper, design and implementation of a pipe lamps contain optical reflectors where three types of adoption of the lamps are different diameters and lengths with reflectors visual reflect solar radiation by 84% and tested practicable ＂in the laboratory room dimensions using Lux Meter device and enter the data in the program （surfer） the fee distribution of the intensity of radiation in the room laboratory ratios has been found that the intensity distribution of light inside the room are adversely affected＂ with the decrease in diameter of lamp At less intensity in half at reducing the tube diameter by 25% and increases with tube diameter, and vice versa for the impact of length where the intensity is light distribution higher when the lamp is tubular Short at the intensity of the radiation increases by 20% when you reduce the length of the tube in half, as well as show that weather factors such as dust and clouds adversely affected to the efficient functioning of the lamps and the intensity distribution of light in the room.展开更多
Earth is inhomogeneous, which means its elastic characteristics change with depth. The seismic method employs the propagation of waves throughout the earth to locate different structures and stratigraphy. Understandin...Earth is inhomogeneous, which means its elastic characteristics change with depth. The seismic method employs the propagation of waves throughout the earth to locate different structures and stratigraphy. Understanding the wave propagation is an important matter in exploration seismology;therefore modeling of seismic wave is an important tool. To validate the interpreted earth model out of the seismic data, seismic synthetic seismograms should be generated in a process named “seismic forward modeling”. Finite difference method is used as one of the most common numerical modeling techniques. In this paper the accuracy of finite difference method in seismic section modeling is explored on different modeled data set of heterogeneous earth. It is shown that finite difference method completes with migration to reposition the events in their correct location. Two different migration methods are used and various velocities are also tested to determine an appropriate migration velocity. Finally the validly of finite difference modeling is examined using a 2D structural similarity index technique.展开更多
In this study,we investigate the impact of substrates with distributed Bragg reflectors(DBRs)on the proximity effect during the fabrication of superconducting nanowire single-photon detectors(SNSPDs)using electron bea...In this study,we investigate the impact of substrates with distributed Bragg reflectors(DBRs)on the proximity effect during the fabrication of superconducting nanowire single-photon detectors(SNSPDs)using electron beam lithography.We compare the linewidth compression and line edge roughness of nanowires prepared on three different DBRs substrates.Additionally,we characterize the variations in switching current(I_(sw))and intrinsic detection efficiency(IDE)at a 2.2-K temperature.The results show that when the substrates are composed of low atomic number materials,such as Si and SiO2,the proximity effect is significantly mitigated.As a consequence,the lithography quality of nanowires is effectively improved,thus enhancing the IDE of SNSPDs.This study is expected to provide new insights into the fabrication of SNSPDs and lay the foundation for the preparation of high-performance and high-uniformity large-area devices.展开更多
Reflectors are an essential component for on-chip integrated photonics. Here, we propose a new method for designing reflectors on the prevalent thin-film-on-insulator platform by using genetic-algorithm optimization.I...Reflectors are an essential component for on-chip integrated photonics. Here, we propose a new method for designing reflectors on the prevalent thin-film-on-insulator platform by using genetic-algorithm optimization.In simulation, the designed reflector with a footprint of only 2.16 μm× 2.16 μm can achieve ~97% reflectivity and 1 dB bandwidth as wide as 220 nm. The structure is composed of randomly distributed pixels and is highly robust against the inevitable corner rounding effect in device fabrication. In experiment, we fabricated on-chip Fabry–Perot(FP) cavities constructed from optimized reflectors. Those FP cavities have intrinsic quality factors of>2000 with the highest value beyond 4000 in a spectral width of 200 nm. The reflectivity fitted from the FP cavity resonances is >85% in the entire wavelength range of 1440–1640 nm and is beyond 95% at some wavelengths.The fabrication processes are CMOS compatible and require only one step of lithography and etch. The devices can be used as a standard module in integrated photonic circuitry for wide applications in on-chip semiconductorlaser structures and optical signal processing.展开更多
A novel Y-branch waveguide with two reflectors is proposed. The normalized transmitted power for the branching angle of 50?is greater than 70%, which is higher than conventional Y-branch with such wide angle.
Efficient, scalable, bufferless, and compact Ⅲ–V lasers directly grown on(001)-oriented silicon-on-insulators(SOIs) are preferred light sources in Si-photonics. In this article, we present the design and operation ...Efficient, scalable, bufferless, and compact Ⅲ–V lasers directly grown on(001)-oriented silicon-on-insulators(SOIs) are preferred light sources in Si-photonics. In this article, we present the design and operation of Ⅲ–V telecom nanolaser arrays with integrated distributed Bragg reflectors(DBRs) epitaxially grown on industry-standard(001) SOI wafers. We simulated the mirror reflectance of different guided modes under various mirror architectures, and accordingly devised nanoscale DBR gratings to support high reflectivity around1500 nm for the doughnut-shaped TE01 mode. Building from InP/InGaAs nanoridges grown on SOI, we fabricated subwavelength DBR mirrors at both ends of the nanoridge laser cavities and thus demonstrated room-temperature low-threshold InP/InGaAs nanolasers with a 0.28 μm^2 cross-section and a 20 μm effective cavity length. The direct growth of these bufferless nanoscale Ⅲ–V light emitters on Si-photonics standard(001) SOI wafers opens future options of fully integrated Si-based nanophotonic integrated circuits in the telecom wavelength regime.展开更多
The influence of nodule defects on the characteristics of femtosecond laser-induced damage has not been fully investigated.In this study,two types of 800 nm/1064 nm dual-band HfO_(2)=Si O_(2) high-reflection films wit...The influence of nodule defects on the characteristics of femtosecond laser-induced damage has not been fully investigated.In this study,two types of 800 nm/1064 nm dual-band HfO_(2)=Si O_(2) high-reflection films with different configurations were analyzed.Combined with finite-difference time-domain electric field simulation and focused ion beam analysis,the initial state and growth process of femtosecond laser damage of nodules were explored.In particular,the sequence of blister damage determined by the film design and the inner damage caused by nodules were clarified.The rule of the laser-induced damage threshold of different size nodules was obtained.The difference in the damage behavior of nodules in the two types of films was elucidated.展开更多
In this study,Differential Interferometric Synthetic Aperture Radar Interferometry(DInSAR)of artificial Corner Reflectors(CRs)were validated in the area of fast and nonlinear deformation gradient caused by active coal...In this study,Differential Interferometric Synthetic Aperture Radar Interferometry(DInSAR)of artificial Corner Reflectors(CRs)were validated in the area of fast and nonlinear deformation gradient caused by active coal longwall exploitation.Three Sentinel-1 datasets were processed using conventional DInSAR,Persistent Scatterer Interferometry(PSI),and Small BAseline Subset methods implemented in ENVI SARscape™.For evaluation,leveling and Global Navigation Satellite System(GNSS)measurements were used.Considering the challenge of snow cover,the removal of all winter images was not a successful strategy due to the long temporal baseline and strong movement,which cause phase unwrapping problems and underestimate the real deformation.The results indicate that only conventional DInSAR and SBAS with low network redundancy allow us to capture maximal deformation gradient and the root mean square error calculated between the CRs and the ground truth is on the level of 2–3 cm for the vertical and easting deformation component,respectively.For the small deformation gradient represented by the permanent GNSS station(4 cm/year),all SBAS techniques appeared to be more accurate than DInSAR,which corresponds to higher redundancy and better removal of the atmospheric signal.In contrast,DInSAR results allowed to capture information about two subsidence basins,which was not possible with SBAS and PSI approaches.展开更多
基金supported by the Equipment Pre-research Project(GK202002A020068)。
文摘Passive jamming is believed to have very good potential in countermeasure community.In this paper,a passive angular blinking jamming method based on electronically controlled corner reflectors is proposed.The amplitude of the incident wave can be modulated by switching the corner reflector between the penetration state and the reflection state,and the ensemble of multiple corner reflectors with towing rope can result in complex angle decoying effects.Dependency of the decoying effect on corner reflectors’radar cross section and positions are analyzed and simulated.Results show that the angle measured by a monopulse radar can be significantly interfered by this method while the automatic tracking is employed.
文摘The wet oxidation of AlGaAs with high Al content in a distributed Bragg reflectors （DBR） is studied by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. Some voids distribute along the oxide/GaAs interfaces due to the stress induced by the wet oxidation of the AlGaAs layers. These voids decrease the shrinkage of the Al2O3 layers to 8% instead of the theoretical 20% when compared to the unoxidized AlGaAs layers. With the extension of oxidation time, the reactants are more completely transported to the front interface and the products are more completely transported out along the porous interfaces. As a result,the oxide quality is better.
基金funded by the National Natural Science Foundation of China(41872172,42072188)Jiangxi Provincial Natural Science Foundation(20202BABL211019)Open Fund Project of the Key Laboratory of Sedimentary Mineralization and Sedimentary Mineral Resources in Shandong Province(DMSM 2019008)。
文摘Many mound-shaped reflectors with different features and shapes are evident in the Upper Member of the Meishan Formation from seismic profiles taken in the deep-water area of the Southern Qiongdongnan Basin.Based on the drilling,2 D and 3 D seismic data from the study area,descriptions of the seismic reflection characteristics as well as the geometric shape,wave impedance inversion,analogy and comparative analyses are carried out.Taken in conjunction with research on the paleo structure and paleo sedimentary background,we consider that the mound-shaped seismic reflectors are distributed in the Southern Slop belt and the Southern High-rise of the Qiongdongnan Basin,which can be subdivided into three types:reefs,contourite mounds and magmatic diapirs.The first type,reefs,includes patch reefs,platform marginal reefs and pinnacle reefs.Patch reefs present mound-shaped seismic facies with medium frequency and a moderately strong amplitude,being distributed at the uplift of the fault control platform on the Southern Slop belt.The platform marginal reefs have flat mound-shaped seismic facies with strong amplitude and medium frequency,developing at the margin of the carbonate platform in the Southern High-rise.The pinnacle reefs have mound-shaped seismic facies with strong amplitude and medium frequency and are developed on an isolated volcanic cone.The boundaries between individual reefs are clear on the seismic section,with reef ridge and reef ditch developed,the phenomenon of’front product’being visible within,two-way superelevation between wings is developed and they exist visibly as mounds in any viewed direction of the crosssection.They are slightly asymmetrical in the direction perpendicular to the paleodepth the reef body being steep near the deep-water side,while being gentle near the shallow water side.The wave impedance of a patch reef is about 7 kg/m^(3)×m/s,while the wave impedance of a platform marginal reef is about 7.5 kg/m^(3)×m/s.The second type-contourite moundsare mainly developed under the slope break of the southern slope fault control platform’s edge.They are subdivided into two types:conical and flat.The former has mound-shaped seismic facies with medium-strong amplitude and low frequency,the latter having mound-shaped seismic facies with medium amplitude and low frequency.The internal texture of the mounds is not clear on the seismic section,with the boundaries between contourite mounds being blurred.They are mound-shaped only in cross-section,being banded in the extending direction.The upper surface of a single contourite mound is relatively gentle near the deep-water side,while being steep near the shallow water area.The wave impedance of contourite mounds is about 5.8 kg/m^(3)×m/s,which is speculated to represent a marly to calcareous clastic deposit.The third type is the magmatic diapir,which has’roots’.They have a dome-shaped upper boundary,are bottomless,with a chaotic interior.They penetrated multiple formations,opening towards the base.There are two major accumulation assemblages of reefs,one is the platform margin reef accumulation assemblage with distant source rocks and long-distance migration through an unconformity surface in the Southern High-rise,the other is the patch reef accumulation assemblage with twin sources and short distance migration through faults in the Southern Slop belt near the Central Depression zone.The latter is the main exploration targets at present.There are contourite mound accumulation assemblages with nearby source rocks and short distance vertical migration through faults,which are potentially important targets.The magmatic diapirs pierce the overlying strata and form good hydrocarbon traps and migration pathways,thus representing potential prospecting targets.
文摘Passive intermodulation（PIM） has gradually become a serious electromagnetic interference due to the development of high-power and high-sensitivity RF/microwave communication systems, especially large deployable mesh reflector antennas. This paper proposes a field-circuit coupling method to analyze the PIM level of mesh reflectors. With the existence of many metal–metal（MM） contacts in mesh reflectors, the contact nonlinearity becomes the main reason for PIM generation. To analyze these potential PIM sources, an equivalent circuit model including nonlinear components is constructed to model a single MM contact so that the transient current through the MM contact point induced by incident electromagnetic waves can be calculated. Taking the electric current as a new electromagnetic wave source, the far-field scattering can be obtained by the use of electromagnetic numerical methods or the communication link method. Finally, a comparison between simulation and experimental results is illustrated to verify the validity of the proposed method.
基金supported by the National Natural Science Foundation of China (No. 40730317), and China Scholarship Council
文摘Seismic studies of the crustal structure beneath the Three Gorges Reservoir（TGR） region in Central China have been limited by the sparse and uneven distribution of seismic stations.To in-crease the station coverage,we made three deployments of a mobile seismologic array in the TGR re-gion during the three summers from 2008 to 2010.Here we present interpretations along a west-east profile through the central TGR region based on new seismic waveform data and a velocity model con-strained by regional earthquake data.Two strong mid-crustal reflection interfaces at depths around 10 and 20 km are seen under the TGR.The shallow reflector defines the bottom of the Zigui（秭归） basin.The new waveform data show that the amplitude of the Moho reflection is quite weak,and beneath the Moho,there is a strong reflector around 54-km depth.It is likely that in the TGR region,the Moho is a gradient rather than a sharp boundary.We speculate that the gradient Moho and the 54-km-deep re-flector in the upper mantle in the TGR region may be by-products of the Qinling（秦岭）-Dabie（大别） orogen.
文摘Thermal neutron albedo has been investigated for different thicknesses of mono-material and bi-material reflectors. An equation has been obtained for a bi-material reflector by considering the neutron diffusion equation. The bi-material reflector consists of binary combinations of water, graphite, lead, and polyethylene. An experimental measurement of thermal neutron albedo has also been conducted for mono-material and bi-material reflectors by using a^(241) Am–Be(5.2 Ci) neutron source and a BF3 detector. The maximum value of thermal neutron albedo was obtained for a polyethylene–water combination(0.95 ± 0.02).
基金Project supported by the National Natural Science Foundation of China(Grant No.12033009)。
文摘As the signal reflected by the corner-cube reflector arrays is very weak and easily submerged during the full moon,we analyze the influence of the thermal effect of corner-cube reflector arrays on the intensity of lunar laser ranging echo.Laser ranging measurements during the penumbra lunar eclipse verify suspected thermal deformation in the Lunakhod 2 reflectors.Signal levels vary over two orders of magnitude as the penumbra eclipse progresses.This can be explained by the change in the dihedral angle of the corner-cube reflectors caused by the temperature.The results show that when the dihedral angle errors reach 1,the energy is reduced by 100 times compared with the ideal corner-cube reflector.In the experiment,our findings suggest that when the corner-cube reflector arrays enter the penumbra of the earth,the effective echo signal level which reaches 0.18 photons/s far exceeds the historical level of the full moon.However,11 minutes after the penumbra lunar eclipse,the effective echo rate of Lunakhod 2 will drop two orders of magnitude.The mechanism can explain the acute signal deficit observed at full moon.
基金supported by the National Key Research and Development Program of China (No. 2017YFB0402900)the National Natural Science Foundation of China (No. 61504132, 61505197)
文摘Metallic nanotextured reflectors have been widely used in light emitting diodes(LEDs) to enhance the light extraction efficiency. However, the light absorption loss for the metallic reflectors with nanotexture structure is often neglected. Here, the influence of absorption loss of metallic nanotextured reflectors on the LED optoelectronic properties were studied. Two commonly used metal reflectors Ag and Al were applied to green GaN-based LEDs. By applying a Ag nanotextured reflector, the light output power of the LEDs was enhanced by 78% due to the improved light extraction. For an Al nanotextured reflector, however,only a 6% enhancement of the light output power was achieved. By analyzing the metal absorption using finite-difference timedomain(FDTD) and the metal reflectivity spectrum, it is shown that the surface plasmon(SP) intrinsic absorption of metallic reflectors with nanotexture structure play an important role. This finding will aid the design of the high-performance metal nanotextured reflectors and optoelectronics devices.
基金supported by the National Basic Research Program of China (Grant No. 2011CBA00705)the High Technology Research Program of China (GrantNo. 2011AA050502)
文摘Different aluminum-doped ZnO （AZO）/metal composite thin films, including AZO/Ag/Al, AZO/Ag/nickelchromium alloy （NiCr）, and AZO/Ag/NiCr/Al, are utilized as the back reflectors of p-i-n amorphous silicon germanium thin film solar cells. NiCr is used as diffusion barrier layer between Ag and Al to prevent mutual diffusion, which increases the short circuit current density of solar cell. NiCr and NiCr/AI layers are used as protective layers of Ag layer against oxidation and sulfurization, the higher efficiency of solar cell is achieved. The experimental results show that the performance of a-SiGe solar cell with AZO/Ag/NiCr/Al back reflector is best. The initial conversion efficiency is achieved to be 8.05%.
基金Project (No. 2004CB719802) supported by the National Basic Re-search Program (973) of China
文摘New types of Bragg reflectors, multilayered periodic structures, based on alternating left-handed transmission line (LHTL) and right-handed transmission line (RHTL) are proposed. These new structures based on ideal microstrip TLs and L-C lumped elements, are designed and analyzed. We report on unusual narrow transmission bands in such kind of structures. In such multilayered structures both Bragg reflectance and the Fabry-Perot resonance exist and the phenomenon of unusual transmission is a result of competition between these two transmission effects, in which the Fabry-Perot resonance is dominant. According to our simulation results we find that this unusual transmission property exits no matter if the electrical length of the LHTL layer cancels the electrical length of the RHTL layer or not.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60871049 and 50972024)
文摘Tunable and switchable Ba 0.5 Sr 0.5 TiO 3 film bulk acoustic resonators（FBARs） based on SiO 2 /Mo Bragg reflectors are explored,which can withstand high temperature for the deposition of Ba x Sr 1 x TiO 3（BST） films at 800 C.The dc bias-dependent resonance may be attributed to the piezoelectricity of the BST film induced by an electrostrictive effect.The series resonant frequency is strongly dc bias-dependent and shifts downwards with dc bias increasing,while the parallel resonant frequency is only weakly dc bias-dependent and slightly shifts upwards at low dc bias（ 45 V） while downwards at higher dc bias.The calculated relative tunability of shifts at series resonance frequency is around 2.3% and the electromechanical coupling coefficient is up to approximately 8.09% at 60-V dc bias,which can be comparable to AlN FBARs.This suggests that a high-quality tunable BST FBAR device can be achieved through the use of molybdenum（Mo） as the high acoustic impedance layer in a Bragg reflector,which not only provides excellent acoustic isolation from the substrate,but also improves the crystallinity of BST films withstanding higher deposition temperature.
文摘In this study, a theoretical analysis of a solar field augmented by a fixed reflector placed in the front between the top of the preceding row and the bottom of the succeeding row is presented. An analytical model has been developed and used to estimate the solar irradiation. The analytical model is based on the anisotropic sky model, assuming an infinite length of collector and reflector rows. A simulation has been carried out in order to figure out the behavior of the solar field and to find the optimum design parameters of the solar field leading to a maximum solar energy augmentation. The results obtained are depicted synoptically as a relationship between the solar field design parameters and the latitude angle, and this presentation enables us to determine the optimum design parameters in order to achieve the intended percentage improvement of solar radiation incident on the solar field rows at any location on the Northern hemisphere, which presents the novelty of this research. Also we have introduced a new parameter named “the effective height of the collector”, which presents the portion of the collector’s height illuminated by the reflector. This parameter is very important especially in case of PV solar fields, because it determines the domain of the concentrated solar energy over the surface of the PV panel.
文摘The aim of this research is to find the best way to take advantage of solar radiation in the lighting of sites to reduce reliance on electric power So In this paper, design and implementation of a pipe lamps contain optical reflectors where three types of adoption of the lamps are different diameters and lengths with reflectors visual reflect solar radiation by 84% and tested practicable ＂in the laboratory room dimensions using Lux Meter device and enter the data in the program （surfer） the fee distribution of the intensity of radiation in the room laboratory ratios has been found that the intensity distribution of light inside the room are adversely affected＂ with the decrease in diameter of lamp At less intensity in half at reducing the tube diameter by 25% and increases with tube diameter, and vice versa for the impact of length where the intensity is light distribution higher when the lamp is tubular Short at the intensity of the radiation increases by 20% when you reduce the length of the tube in half, as well as show that weather factors such as dust and clouds adversely affected to the efficient functioning of the lamps and the intensity distribution of light in the room.
文摘Earth is inhomogeneous, which means its elastic characteristics change with depth. The seismic method employs the propagation of waves throughout the earth to locate different structures and stratigraphy. Understanding the wave propagation is an important matter in exploration seismology;therefore modeling of seismic wave is an important tool. To validate the interpreted earth model out of the seismic data, seismic synthetic seismograms should be generated in a process named “seismic forward modeling”. Finite difference method is used as one of the most common numerical modeling techniques. In this paper the accuracy of finite difference method in seismic section modeling is explored on different modeled data set of heterogeneous earth. It is shown that finite difference method completes with migration to reposition the events in their correct location. Two different migration methods are used and various velocities are also tested to determine an appropriate migration velocity. Finally the validly of finite difference modeling is examined using a 2D structural similarity index technique.
基金Innovation Program for Quantum Science and Technology(No.2023ZD0300100)Shanghai Municipal Science and Technology Major Project(2019SHZDZX01)National Natural Science Foundation of China(U24A20320,and 12033007)for their financial support.
文摘In this study,we investigate the impact of substrates with distributed Bragg reflectors(DBRs)on the proximity effect during the fabrication of superconducting nanowire single-photon detectors(SNSPDs)using electron beam lithography.We compare the linewidth compression and line edge roughness of nanowires prepared on three different DBRs substrates.Additionally,we characterize the variations in switching current(I_(sw))and intrinsic detection efficiency(IDE)at a 2.2-K temperature.The results show that when the substrates are composed of low atomic number materials,such as Si and SiO2,the proximity effect is significantly mitigated.As a consequence,the lithography quality of nanowires is effectively improved,thus enhancing the IDE of SNSPDs.This study is expected to provide new insights into the fabrication of SNSPDs and lay the foundation for the preparation of high-performance and high-uniformity large-area devices.
基金Hong Kong Research Grants Council Early Career Scheme(24208915)Hong Kong Research Grants Council Joint Research Scheme(N_CUHK415/15)National Natural Science Foundation of China(NSFC)
文摘Reflectors are an essential component for on-chip integrated photonics. Here, we propose a new method for designing reflectors on the prevalent thin-film-on-insulator platform by using genetic-algorithm optimization.In simulation, the designed reflector with a footprint of only 2.16 μm× 2.16 μm can achieve ~97% reflectivity and 1 dB bandwidth as wide as 220 nm. The structure is composed of randomly distributed pixels and is highly robust against the inevitable corner rounding effect in device fabrication. In experiment, we fabricated on-chip Fabry–Perot(FP) cavities constructed from optimized reflectors. Those FP cavities have intrinsic quality factors of>2000 with the highest value beyond 4000 in a spectral width of 200 nm. The reflectivity fitted from the FP cavity resonances is >85% in the entire wavelength range of 1440–1640 nm and is beyond 95% at some wavelengths.The fabrication processes are CMOS compatible and require only one step of lithography and etch. The devices can be used as a standard module in integrated photonic circuitry for wide applications in on-chip semiconductorlaser structures and optical signal processing.
文摘A novel Y-branch waveguide with two reflectors is proposed. The normalized transmitted power for the branching angle of 50?is greater than 70%, which is higher than conventional Y-branch with such wide angle.
基金Research Grants Council,University Grants Committee(16212115,16245216,AoE/P02/12)Innovation and Technology Fund(ITS/273/16FP)William Mong Institute of Nano Science and Technology(WMINST19/SC04)
文摘Efficient, scalable, bufferless, and compact Ⅲ–V lasers directly grown on(001)-oriented silicon-on-insulators(SOIs) are preferred light sources in Si-photonics. In this article, we present the design and operation of Ⅲ–V telecom nanolaser arrays with integrated distributed Bragg reflectors(DBRs) epitaxially grown on industry-standard(001) SOI wafers. We simulated the mirror reflectance of different guided modes under various mirror architectures, and accordingly devised nanoscale DBR gratings to support high reflectivity around1500 nm for the doughnut-shaped TE01 mode. Building from InP/InGaAs nanoridges grown on SOI, we fabricated subwavelength DBR mirrors at both ends of the nanoridge laser cavities and thus demonstrated room-temperature low-threshold InP/InGaAs nanolasers with a 0.28 μm^2 cross-section and a 20 μm effective cavity length. The direct growth of these bufferless nanoscale Ⅲ–V light emitters on Si-photonics standard(001) SOI wafers opens future options of fully integrated Si-based nanophotonic integrated circuits in the telecom wavelength regime.
基金supported by the National Natural Science Foundation of China(Nos.61675156 and 61975153)。
文摘The influence of nodule defects on the characteristics of femtosecond laser-induced damage has not been fully investigated.In this study,two types of 800 nm/1064 nm dual-band HfO_(2)=Si O_(2) high-reflection films with different configurations were analyzed.Combined with finite-difference time-domain electric field simulation and focused ion beam analysis,the initial state and growth process of femtosecond laser damage of nodules were explored.In particular,the sequence of blister damage determined by the film design and the inner damage caused by nodules were clarified.The rule of the laser-induced damage threshold of different size nodules was obtained.The difference in the damage behavior of nodules in the two types of films was elucidated.
基金The research infrastructure that has been used for computation purposes was created within the project EPOS-PL(POIR.04.02.00-14-A003/16)EPOS-PL+(POIR.04.02.00-00-C005/19-00)European Plate Observing System,funded by the Operational Programme Smart Growth 2014-2020,Priority IV:Increasing the research potential,Action 4.2:Development of modern research infrastructure of the science sector and co-financed by the European Regional Development Fund.
文摘In this study,Differential Interferometric Synthetic Aperture Radar Interferometry(DInSAR)of artificial Corner Reflectors(CRs)were validated in the area of fast and nonlinear deformation gradient caused by active coal longwall exploitation.Three Sentinel-1 datasets were processed using conventional DInSAR,Persistent Scatterer Interferometry(PSI),and Small BAseline Subset methods implemented in ENVI SARscape™.For evaluation,leveling and Global Navigation Satellite System(GNSS)measurements were used.Considering the challenge of snow cover,the removal of all winter images was not a successful strategy due to the long temporal baseline and strong movement,which cause phase unwrapping problems and underestimate the real deformation.The results indicate that only conventional DInSAR and SBAS with low network redundancy allow us to capture maximal deformation gradient and the root mean square error calculated between the CRs and the ground truth is on the level of 2–3 cm for the vertical and easting deformation component,respectively.For the small deformation gradient represented by the permanent GNSS station(4 cm/year),all SBAS techniques appeared to be more accurate than DInSAR,which corresponds to higher redundancy and better removal of the atmospheric signal.In contrast,DInSAR results allowed to capture information about two subsidence basins,which was not possible with SBAS and PSI approaches.
