The careful observation and evaluation of the squamocolumnar junction(SCJ)are essential requirements in colposcopy procedures.While traditional colposcopes with visible light offer high resolution and sensitivity,the ...The careful observation and evaluation of the squamocolumnar junction(SCJ)are essential requirements in colposcopy procedures.While traditional colposcopes with visible light offer high resolution and sensitivity,the presence of glare patterns on the cervix limits the visualization of deeper tissue features.Cross-polarization imaging,on the other hand,overcomes this limitation by effectively removing glare and providing greater optical penetration depth to noninvasively examine subsurface tissue structures.In this study,we present the potential of polarized light in enhancing diagnostics through cross-polarization imaging for the identification and contrast enhancement of squamous and columnar epithelium(CE)in cases of cervical ectropion.Our results demonstrate that polarized light colposcopy offers valuable diagnostic information that complements traditional colposcopy.By effectively reducing glare and improving visibility during cervical examinations,polarized light colposcopy proves to be a useful tool.Furthermore,we introduce a novel method that practically enhances the contrast ratio(CR)between columnar and squamous epithelium(SE)in colposcopic images.This method significantly increases the contrast between these tissue types,facilitating clearer differentiation and improving diagnostic accuracy.Notably,the combination of the cross-polarization imaging technique with our proposed algorithm enables the clear observation of the SCJ boundary.These findings emphasize the potential of our approach in enhancing the accuracy and effectiveness of polarized colposcopy for evaluating cervical tissue.展开更多
A compact broadband cross-polarization conversion metasurface functioning in the microwave regime is realized and experimentally demonstrated. The metasurface consists of a two-dimensional periodic arrangement of anis...A compact broadband cross-polarization conversion metasurface functioning in the microwave regime is realized and experimentally demonstrated. The metasurface consists of a two-dimensional periodic arrangement of anisotropic double- slit split-ring-resonator-based unit cells printed on top of a dielectric substrate, backed by metallic cladding. The proposed metasurface converts an x- or y-polarized wave into its orthogonal polarization over a fractional bandwidth of 100% from 5- 15 GHz, both for normal as well as oblique incidence. Moreover, the sub-wavelength unit-cell size, thin dielectric substrate, and unique unit-cell design collectively make the response of the metasurface same for both polarizations and insensitive to the incidence angle. The designed structure is fabricated and tested. The measurement and simulation results are found to be consistent with each other.展开更多
We present a polarization converter composed of bi-layered metal films perforated with rectangle hole pairs in each film. The proposed converter can convert the polarization of an incident linearly-polarized electroma...We present a polarization converter composed of bi-layered metal films perforated with rectangle hole pairs in each film. The proposed converter can convert the polarization of an incident linearly-polarized electromagnetic wave to its orthogonal direction with high efficiency and large bandwidth in the infrared or microwave regions.To make sure of the mechanism of polarization conversion, the current and electric-field distributions at different resonant frequencies are analyzed. It is found that the cross-polarized transmission is due to the near-field coupling between hole pairs in neighboring metal films. Finally, a prototype of the proposed converter is fabricated and measured in the microwave region. Good agreement between the experimental and simulated results is obtained.展开更多
The paper presents the results of a study of the female urethra in cases of urethral pain syndrome(UPS)and inflammatory diseases of the lower urinary tract using cross-polarization optical coherence tomography(CP OCT)...The paper presents the results of a study of the female urethra in cases of urethral pain syndrome(UPS)and inflammatory diseases of the lower urinary tract using cross-polarization optical coherence tomography(CP OCT).Urethral wall structure was studied in 86 patients;233 CP OCT images were collected.A comparative qualitative analysis of three groups of CP OCT images—"norm","Inflammation"and"UPS"—identified that despite the absence of a clear inflammatory factor in the patient's examination,the urethral tissues in UPS were in an altered state.The changes in the urethral wall with UPS and in cases of inflammation were similar.Using a point scale,three experts independently performed visual scoring of the CP OCT images.Three parameters:epithelial contrast,cavities and the minimum signal depth in the co-channel were evaluated.It was found that,individually,the parameters correlate only weakly with the diag-nosis.Area under the receiver operating characteristic(ROC)curve was from 0.51 to 0.78.The joint use of a number of visual signs has a greater diagnostic value than the use of the criteria individually.Area under the ROC curve using the developed cumulative criterion reached up to 0.87-0.89.This study could form the basis of a scoring system for assessing the state of the urethral tract using CP OCT images in real time.The CP OCT method provides information on the state of urethral tissues that cannot be obtained with traditional cystoscopy.展开更多
We propose and experimentally demonstrate a wideband linear polarization converter in a reflection mode operating from 2.4 to 4.2 THz with conversion efficiency of more than 80%. Our device can expand the applications...We propose and experimentally demonstrate a wideband linear polarization converter in a reflection mode operating from 2.4 to 4.2 THz with conversion efficiency of more than 80%. Our device can expand the applications to a higher frequency band. A numerical simulation is performed for this metamaterial converter, which shows a good agreement with experimental results. Importantly, a concise and intuitive calculating model is proposed for the Fabry–Pérot cavity. The theoretical results indicate that the underlying reason for the enhanced polarization conversion is the additional phase difference induced by the resonance of the meta-structure and multiple reflections within the Fabry–Pérot cavity.展开更多
An anisotropic dielectric realized by layered ceramic structures was adopted to design a low cross-polarization C-shaped patch antenna.The anisotropic dielectric performs as a substrate and can cause additional cross-...An anisotropic dielectric realized by layered ceramic structures was adopted to design a low cross-polarization C-shaped patch antenna.The anisotropic dielectric performs as a substrate and can cause additional cross-polarized fields which are able to cancel the cross-polarized fields generated by the C-shaped patch itself,and then reduce the cross-polarization level.Compared to the C-shaped patch antenna with an isotropic substrate,the cross-polarization of the proposed antenna is suppressed by more than 15 dB with a little gain enhancement at 2.4 GHz.The anisotropic dielectric has a little impact on the direction of the C-shaped patch antenna.The gain of the proposed C-shaped patch antenna is 6.8 dB with a cross-polarization of28 dB.展开更多
Ground penetrating radar（GPR） can be used to image fractures and monitor fluid flow in the subsurface. Conventional GPR imaging uses single-polarization, co-polarized acquisition. We examine the use of cross-polariz...Ground penetrating radar（GPR） can be used to image fractures and monitor fluid flow in the subsurface. Conventional GPR imaging uses single-polarization, co-polarized acquisition. We examine the use of cross-polarized GPR signals for imaging flow channeling in a discrete horizontal fracture. Numerical modeling（FDTD） demonstrates that when the fracture channel is oriented at an oblique angle to the survey line, depolarization of the GPR signal results in scattered energy along the cross-polarized components. When the channel is oriented parallel or orthogonal to the survey line, all scattered energy is captured by the co-polarized components and no signal is present in the cross-polarized orientation. Multipolarization, time-lapse 3D GPR field data were acquired at the Altona Flat Rock test site in New York State. The GPR surveys were conducted during background fresh fracture water conditions and during a natural gradient saline tracer test which was used to highlight flow channels along a sub-horizontal fracture. Amplitude analysis of the cross-polarized data reveals flow channeling that is in agreement with the co-polarized GPR images and with independent hydraulic tests. This investigation demonstrates that cross-polarized components of GPR signals can be used to enhance imaging of flow channels in fractured media.展开更多
The statistic properties of photon emissions from single semiconductor quantum dots with V-type leveldriven by pulses are investigated theoretically.Based on quantum regression theorem and master equations,the dynamic...The statistic properties of photon emissions from single semiconductor quantum dots with V-type leveldriven by pulses are investigated theoretically.Based on quantum regression theorem and master equations,the dynamicequations of the second-order correlation function of the photon emissions are deduced.The calculated results reveal thatthe efficiency of single photon emissions from two orthogonal polarization eigenstates(|x〉and |y〉)reaches the maximumwhen the input pulses area is about π,and the probability of the cross-polarized single photon emission from |x〉and |y〉decreases with increasing of pulse width.展开更多
The underlying mechanism of the spectral cleaning effect of the cross-polarized wave（XPW） generation process was theoretically investigated. This study shows that the spectral noise of an input spectrum can be remov...The underlying mechanism of the spectral cleaning effect of the cross-polarized wave（XPW） generation process was theoretically investigated. This study shows that the spectral noise of an input spectrum can be removed in the XPW generation process and that the spectral cleaning effect depends on the characteristics of the input pulses, such as the chirp and Fourier-transform-limited duration of the initial pulse, and the modulation amplitude and frequency of the spectral noise. Though these factors codetermine the output spectrum of the XPW generation process, the spectral cleaning effect is mainly affected by the initial pulse chirp. The smoothing of the spectrum in the XPW generation process leads to a significant enhancement of the coherent contrast.展开更多
We demonstrate a high-quality cross-polarized-wave filter based on spectral phase modulation. Driven by Well- eompressed spectral-phase fully-compensated fundamental laser lmlses, the filter stretches the pulse bandwi...We demonstrate a high-quality cross-polarized-wave filter based on spectral phase modulation. Driven by Well- eompressed spectral-phase fully-compensated fundamental laser lmlses, the filter stretches the pulse bandwidth from 35 nm to 7Ohm with a conversion efficeiency of 20%.展开更多
This paper presents a novel method for polarized antenna transmission utilizing a differential technique. The method uses a linear cross-polarized antenna, for example, a vertical and horizontal polarized antenna, imp...This paper presents a novel method for polarized antenna transmission utilizing a differential technique. The method uses a linear cross-polarized antenna, for example, a vertical and horizontal polarized antenna, improving performance and power efficiency of wireless communications. Hence a linear relationship between the capacity of the systems and the number of cross-polarized antennas exists. The result shows the fact that this method enhances the SNR comparing to other systems. This solution is simple, compact and does not require any bandwidth expansion.展开更多
A wideband dual-polarized slot-coupled stacked microstrip antenna with very high isolation and low cross-polarization is presented. To improve isolation between two poiarization ports, the stacked patches are excited ...A wideband dual-polarized slot-coupled stacked microstrip antenna with very high isolation and low cross-polarization is presented. To improve isolation between two poiarization ports, the stacked patches are excited by an open-ended and a T-shaped microstrip lines both via two H-shaped slots placed in a ＂T＂ configuration. The measured isolation is better than 40.5 dB over the bandwidth from 8.8 to 9.8 GHz with cross-polarization level less than - 28.5 dB. The measured VSWR ≤ 2 bandwidths reach 20.7 96 and 19.196 at the verrical and horizontal polarization ports, respectively. This antenna is suitable to be used as array elements in spacebome synthetic aperture radars （SAR） and active phased array radars.展开更多
Synthetic aperture radar(SAR)is a suitable tool to obtain reliable wind retrievals with high spatial resolution.The geophysical model function(GMF),which is widely employed for wind speed retrieval from SAR data,descr...Synthetic aperture radar(SAR)is a suitable tool to obtain reliable wind retrievals with high spatial resolution.The geophysical model function(GMF),which is widely employed for wind speed retrieval from SAR data,describes the relationship between the SAR normalized radar cross-section(NRCS)at the copolarization channel(vertical-vertical and horizontal-horizontal)and a wind vector.SAR-measured NRCS at cross-polarization channels(horizontal-vertical and vertical-horizontal)correlates with wind speed.In this study,a semi-empirical algorithm is presented to retrieve wind speed from the noisy Chinese Gaofen-3(GF-3)SAR data with noise-equivalent sigma zero correction using an empirical function.GF-3 SAR can acquire data in a quad-polarization strip mode,which includes cross-polarization channels.The semi-empirical algorithm is tuned using acquisitions collocated with winds from the European Center for Medium-Range Weather Forecasts.In particular,the proposed algorithm includes the dependences of wind speed and incidence angle on cross-polarized NRCS.The accuracy of SAR-derived wind speed is around 2.10ms−1 root mean square error,which is validated against measurements from the Advanced Scatterometer onboard the Metop-A/B and the buoys from the National Data Buoy Center of the National Oceanic and Atmospheric Administration.The results obtained by the proposed algorithm considering the incidence angle in a GMF are relatively more accurate than those achieved by other algorithms.This work provides an alternative method to generate operational wind products for GF-3 SAR without relying on ancillary data for wind direction.展开更多
A feasible method for synthesizing millimeter-wave conical array and optimizing low cross-polarization is proposed.Starting from the far-field superposition principle,an efficient approach including element mutual cou...A feasible method for synthesizing millimeter-wave conical array and optimizing low cross-polarization is proposed.Starting from the far-field superposition principle,an efficient approach including element mutual coupling and mounted platform effects is used to calculate the far-field patterns.A coordinate transform is applied to create polarization quantities,and a general process for the element polarized pattern transformation is performed.Corresponding numerical example is given and the desired sidelobe level and low cross-polarization are optimized.The numerical results indicate the proposed method is valid.展开更多
Gaofen-3-02(GF3-02)is the first C-band synthetic aperture radar(SAR)satellite with terrain observation with progressive scans of SAR(TOPSAR)imaging mode in China,which plays an essential role in marine environment mon...Gaofen-3-02(GF3-02)is the first C-band synthetic aperture radar(SAR)satellite with terrain observation with progressive scans of SAR(TOPSAR)imaging mode in China,which plays an essential role in marine environment monitoring.Given the weak scattering characteristics of the ocean,the system thermal noise superimposed on SAR images has significant interference,especially in cross-polarization channels.Noise-Equivalent Sigma-Zero(NESZ)is a measure of the sensitivity of the radar to areas of low backscatter.The NESZ is defined to be the scattering cross-section coefficient of an area which contributes a mean level in the image equal to the signal-independent additive noise level.For TOPSAR,NESZ exhibits the shape of the SAR scanning gain curve in the azimuth and the shape of the antenna pattern in the range.Therefore,the accurate measurement of NESZ plays a vital role in the application of spaceborne SAR sea surface cross-polarization data.This paper proposes a theoretical calculation method for the NESZ curve in GF3-02 TOPSAR mode based on SAR noise inner calibration data and the imaging algorithm.A method for correcting the error existing in the theoretical curve of NESZ is also proposed according to the relationship between sea surface backscattering and wind speed and the same characteristics of target scattering in the overlapping area of adjacent sub-swaths.According to assessment with wide-swath TOPSAR cross-polarization data,the GF3-02 TOPSAR mode has a very low thermal noise level,which is better than−33 dB at the edge of each beam,and controlled below−38 dB at the center of the beam.The two-dimensional reference curves of the NESZ of each beam are provided to the GF3-02 TOPSAR users.After discussing the relationship between normalized radar cross section(NRCS)and wind speed,we provide a formula for NRCS related to wind speed and radar incidence angle.Compared with the NRCS derived from this formula and the NESZ-subtracted NRCS of SAR images,the bias is−0.0048 dB,the Root Mean Square Error is 1.671 dB and the correlation coefficient is 0.939.展开更多
This paper presents a new blind XPIC and a new adaptive blind deconvolutional algorithm based on HOS processing, which separates and equalizes the signals in real time. The simulation results demonstrate that the perf...This paper presents a new blind XPIC and a new adaptive blind deconvolutional algorithm based on HOS processing, which separates and equalizes the signals in real time. The simulation results demonstrate that the performance of the proposed adaptive blind algorithm,compared with the conventional algorithms, is outstanding with the feature of feasibility, stability and fast convergence rate.展开更多
Above Ground Biomass is one of the six pools identified in the inventory of forest resources and estimation of greenhouse gas emissions and sinks from the forestry sector. The pool varies by management practices in di...Above Ground Biomass is one of the six pools identified in the inventory of forest resources and estimation of greenhouse gas emissions and sinks from the forestry sector. The pool varies by management practices in different agro-ecological or agro-climatic zones in forests. The quantification of above ground biomass (AGB) hence carbon sequestration in forests has been very difficult due to the immense costs required. This research was done to estimate AGB using ALOS PALSAR L band data (HH, HV polarisation) acquired in 2009 in relation with ground measurements data in Kericho and Aberdares ranges in Kenya. Tree data information was obtained from ground measurement of DBH and tree heights in 100 circular plots of 15 m radius, by use of random sampling technique. ALOS PALSAR image is advantageous for its active microwave sensor using L-band frequency to achieve cloud free imageries, and the ability of long wavelength cross-polarization to estimate AGB accurately for tropical forests. The variations result between Natural and plantation forest for measured and estimated biomass in Kericho HV band regression value was 0.880 and HH band was 0.520. In Aberdare ranges HV regression value of 0.708 and HH band regression value of 0.511 for measured and estimated biomass respectively. The variations can be explained by the influence of different management regimes induced human disturbances, forest stand age, density, species composition, and trees diameter distribution. However, further research is required to investigate how strong these factors affect relationship between AGB and Alos Palsar backscatters.展开更多
Collagen provides tissue strength and structural integrity.Quanti fication of the orientated dispersion of collagen fibers is an important factor when studying the mechanical properties of the cervix.In this study,for...Collagen provides tissue strength and structural integrity.Quanti fication of the orientated dispersion of collagen fibers is an important factor when studying the mechanical properties of the cervix.In this study,for the first time,a new method for rapid characterization of the collagen fiber orientations of the cervix using linearly polarized light colposcopy is presented.A total of 24 colposcopic images were captured using a cross-polarized imaging system with white LED light sources.In the preprocessing stage,the Red channel of the RGB image was chosen,which contains no information of the blood vessels because of the low-absorption of blood cells in the red region.OrientationJ,which is an ImageJ plug-in,was used to estimate the local orientation of the collagen fibers.The result shows that in the nonpregnant cervix,the middle zone(Zone 2)has circumferentially aligned collagen fibers while the inner zone(Zone 1)has randomly arranged.The collagen fiber dispersion in Zone 2 is much smaller than that in Zone 1 at all four quadrants region(anterior,posterior,left,and right quadrant).This new analysis technique could potentially combine with diagnostic tools to provide a quantitative platform of collagen fibers in the clinic.展开更多
Ⅰ. INTRODUCTIONOrganometallic complexes containing phosphorous ligands are used to catalyze various organic transformations. It is interesting that these homogeneous catalysts on polymer can facilitate the separation...Ⅰ. INTRODUCTIONOrganometallic complexes containing phosphorous ligands are used to catalyze various organic transformations. It is interesting that these homogeneous catalysts on polymer can facilitate the separation of the reaction products. It is more important to explore the展开更多
A geometry-based stochastic scattering model （GBSSM） based on geometrical multiple rings and ellipses is proposed for wideband multiple-input multiple-output （MIMO） mobile-to-mobile （M2M） fading channels. The pr...A geometry-based stochastic scattering model （GBSSM） based on geometrical multiple rings and ellipses is proposed for wideband multiple-input multiple-output （MIMO） mobile-to-mobile （M2M） fading channels. The proposed GBSSM is deployed with cross-polarized antennas and can be applied for the line-of-sight （LOS） and non- LOS （NLOS） scenarios by considering the single-bounced （SB） and double-bounced （DB） components. The channel realization is much more straightforward and concise to study the channel characteristics compared with the too complicated analytical solutions available so far. Based on the proposed GBSSM and realized channel, the channel characteristics and parameters at 2 GHz and 5 GHz with 100 MHz bandwidth are further investigated. The results can be used in the link and system level simulations in M2M radio systems.展开更多
文摘The careful observation and evaluation of the squamocolumnar junction(SCJ)are essential requirements in colposcopy procedures.While traditional colposcopes with visible light offer high resolution and sensitivity,the presence of glare patterns on the cervix limits the visualization of deeper tissue features.Cross-polarization imaging,on the other hand,overcomes this limitation by effectively removing glare and providing greater optical penetration depth to noninvasively examine subsurface tissue structures.In this study,we present the potential of polarized light in enhancing diagnostics through cross-polarization imaging for the identification and contrast enhancement of squamous and columnar epithelium(CE)in cases of cervical ectropion.Our results demonstrate that polarized light colposcopy offers valuable diagnostic information that complements traditional colposcopy.By effectively reducing glare and improving visibility during cervical examinations,polarized light colposcopy proves to be a useful tool.Furthermore,we introduce a novel method that practically enhances the contrast ratio(CR)between columnar and squamous epithelium(SE)in colposcopic images.This method significantly increases the contrast between these tissue types,facilitating clearer differentiation and improving diagnostic accuracy.Notably,the combination of the cross-polarization imaging technique with our proposed algorithm enables the clear observation of the SCJ boundary.These findings emphasize the potential of our approach in enhancing the accuracy and effectiveness of polarized colposcopy for evaluating cervical tissue.
文摘A compact broadband cross-polarization conversion metasurface functioning in the microwave regime is realized and experimentally demonstrated. The metasurface consists of a two-dimensional periodic arrangement of anisotropic double- slit split-ring-resonator-based unit cells printed on top of a dielectric substrate, backed by metallic cladding. The proposed metasurface converts an x- or y-polarized wave into its orthogonal polarization over a fractional bandwidth of 100% from 5- 15 GHz, both for normal as well as oblique incidence. Moreover, the sub-wavelength unit-cell size, thin dielectric substrate, and unique unit-cell design collectively make the response of the metasurface same for both polarizations and insensitive to the incidence angle. The designed structure is fabricated and tested. The measurement and simulation results are found to be consistent with each other.
文摘We present a polarization converter composed of bi-layered metal films perforated with rectangle hole pairs in each film. The proposed converter can convert the polarization of an incident linearly-polarized electromagnetic wave to its orthogonal direction with high efficiency and large bandwidth in the infrared or microwave regions.To make sure of the mechanism of polarization conversion, the current and electric-field distributions at different resonant frequencies are analyzed. It is found that the cross-polarized transmission is due to the near-field coupling between hole pairs in neighboring metal films. Finally, a prototype of the proposed converter is fabricated and measured in the microwave region. Good agreement between the experimental and simulated results is obtained.
基金financially supported by the the R.FBR grant,project No.19-07-00395
文摘The paper presents the results of a study of the female urethra in cases of urethral pain syndrome(UPS)and inflammatory diseases of the lower urinary tract using cross-polarization optical coherence tomography(CP OCT).Urethral wall structure was studied in 86 patients;233 CP OCT images were collected.A comparative qualitative analysis of three groups of CP OCT images—"norm","Inflammation"and"UPS"—identified that despite the absence of a clear inflammatory factor in the patient's examination,the urethral tissues in UPS were in an altered state.The changes in the urethral wall with UPS and in cases of inflammation were similar.Using a point scale,three experts independently performed visual scoring of the CP OCT images.Three parameters:epithelial contrast,cavities and the minimum signal depth in the co-channel were evaluated.It was found that,individually,the parameters correlate only weakly with the diag-nosis.Area under the receiver operating characteristic(ROC)curve was from 0.51 to 0.78.The joint use of a number of visual signs has a greater diagnostic value than the use of the criteria individually.Area under the ROC curve using the developed cumulative criterion reached up to 0.87-0.89.This study could form the basis of a scoring system for assessing the state of the urethral tract using CP OCT images in real time.The CP OCT method provides information on the state of urethral tissues that cannot be obtained with traditional cystoscopy.
基金supported by the National Key R&D Program of China(Nos.2017YFF0106302 and2017YFA0701005)the National Natural Science Foundation of China(Nos.61775229 and 61604161)+1 种基金the Natural Science Foundation of Shanghai(No.17ZR1448300)the Shanghai International Cooperation Project(No.18590780100)
文摘We propose and experimentally demonstrate a wideband linear polarization converter in a reflection mode operating from 2.4 to 4.2 THz with conversion efficiency of more than 80%. Our device can expand the applications to a higher frequency band. A numerical simulation is performed for this metamaterial converter, which shows a good agreement with experimental results. Importantly, a concise and intuitive calculating model is proposed for the Fabry–Pérot cavity. The theoretical results indicate that the underlying reason for the enhanced polarization conversion is the additional phase difference induced by the resonance of the meta-structure and multiple reflections within the Fabry–Pérot cavity.
基金supported in part by the National Natural Science Foundation of China under Grant 61501365,61601360,61471292,61331005the China Postdoctoral Science Foundation under Grant 2015M580849.
文摘An anisotropic dielectric realized by layered ceramic structures was adopted to design a low cross-polarization C-shaped patch antenna.The anisotropic dielectric performs as a substrate and can cause additional cross-polarized fields which are able to cancel the cross-polarized fields generated by the C-shaped patch itself,and then reduce the cross-polarization level.Compared to the C-shaped patch antenna with an isotropic substrate,the cross-polarization of the proposed antenna is suppressed by more than 15 dB with a little gain enhancement at 2.4 GHz.The anisotropic dielectric has a little impact on the direction of the C-shaped patch antenna.The gain of the proposed C-shaped patch antenna is 6.8 dB with a cross-polarization of28 dB.
基金supported by the US Department of Energy Environmental Remediation Sciences Program (No. 07-358509)the US Department of Energy Geothermal Technologies Program (No. DE-EE0002767)GPR instrumentation was funded by the National Science Foundation (No. EAR/IF-0345445)
文摘Ground penetrating radar（GPR） can be used to image fractures and monitor fluid flow in the subsurface. Conventional GPR imaging uses single-polarization, co-polarized acquisition. We examine the use of cross-polarized GPR signals for imaging flow channeling in a discrete horizontal fracture. Numerical modeling（FDTD） demonstrates that when the fracture channel is oriented at an oblique angle to the survey line, depolarization of the GPR signal results in scattered energy along the cross-polarized components. When the channel is oriented parallel or orthogonal to the survey line, all scattered energy is captured by the co-polarized components and no signal is present in the cross-polarized orientation. Multipolarization, time-lapse 3D GPR field data were acquired at the Altona Flat Rock test site in New York State. The GPR surveys were conducted during background fresh fracture water conditions and during a natural gradient saline tracer test which was used to highlight flow channels along a sub-horizontal fracture. Amplitude analysis of the cross-polarized data reveals flow channeling that is in agreement with the co-polarized GPR images and with independent hydraulic tests. This investigation demonstrates that cross-polarized components of GPR signals can be used to enhance imaging of flow channels in fractured media.
基金National Natural Science Foundation of China under Grant Nos.10534030 and CAST200729
文摘The statistic properties of photon emissions from single semiconductor quantum dots with V-type leveldriven by pulses are investigated theoretically.Based on quantum regression theorem and master equations,the dynamicequations of the second-order correlation function of the photon emissions are deduced.The calculated results reveal thatthe efficiency of single photon emissions from two orthogonal polarization eigenstates(|x〉and |y〉)reaches the maximumwhen the input pulses area is about π,and the probability of the cross-polarized single photon emission from |x〉and |y〉decreases with increasing of pulse width.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11127901,61521093,and 61505234)the International S&T Cooperation of Program of China(Grant No.2016YFE0119300)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB160301)the Youth Innovation Promotion Association,Chinese Academy of Sciences
文摘The underlying mechanism of the spectral cleaning effect of the cross-polarized wave（XPW） generation process was theoretically investigated. This study shows that the spectral noise of an input spectrum can be removed in the XPW generation process and that the spectral cleaning effect depends on the characteristics of the input pulses, such as the chirp and Fourier-transform-limited duration of the initial pulse, and the modulation amplitude and frequency of the spectral noise. Though these factors codetermine the output spectrum of the XPW generation process, the spectral cleaning effect is mainly affected by the initial pulse chirp. The smoothing of the spectrum in the XPW generation process leads to a significant enhancement of the coherent contrast.
基金Supported by the National Key Basic Research Program of China under Grant No 2013CB922402the National Natural Science Foundation of China under Grant Nos 61575217 and 11434016+1 种基金the Key Research Program of Frontier Sciences of Chinese Academy of Sciences under Grant Nos KJZD-EW-L11-03 and QYZDJ-SSW-JSC006the Strategic Priority Research Program of Chinese Academy of Sciences under Grant No XDB16030200
文摘We demonstrate a high-quality cross-polarized-wave filter based on spectral phase modulation. Driven by Well- eompressed spectral-phase fully-compensated fundamental laser lmlses, the filter stretches the pulse bandwidth from 35 nm to 7Ohm with a conversion efficeiency of 20%.
文摘This paper presents a novel method for polarized antenna transmission utilizing a differential technique. The method uses a linear cross-polarized antenna, for example, a vertical and horizontal polarized antenna, improving performance and power efficiency of wireless communications. Hence a linear relationship between the capacity of the systems and the number of cross-polarized antennas exists. The result shows the fact that this method enhances the SNR comparing to other systems. This solution is simple, compact and does not require any bandwidth expansion.
文摘A wideband dual-polarized slot-coupled stacked microstrip antenna with very high isolation and low cross-polarization is presented. To improve isolation between two poiarization ports, the stacked patches are excited by an open-ended and a T-shaped microstrip lines both via two H-shaped slots placed in a ＂T＂ configuration. The measured isolation is better than 40.5 dB over the bandwidth from 8.8 to 9.8 GHz with cross-polarization level less than - 28.5 dB. The measured VSWR ≤ 2 bandwidths reach 20.7 96 and 19.196 at the verrical and horizontal polarization ports, respectively. This antenna is suitable to be used as array elements in spacebome synthetic aperture radars （SAR） and active phased array radars.
基金supported by the Fundamental Research Funds for Zhejiang Provincial Universities and Research Institutes (No. 2019J00010)the National Key Research and Development Program of China (No. 2017YFA0604901)+3 种基金the National Natural Science Foundation of China (Nos. 41806005 and 41776183) the Public Welfare Technical Applied Research Project of Zhejiang Province of China (No. LGF19D060003) the New- Shoot Talented Man Plan Project of Zhejiang Province (No. 2018R411065) the Science and Technology Project of Zhou- shan City (No. 2019C21008)
文摘Synthetic aperture radar(SAR)is a suitable tool to obtain reliable wind retrievals with high spatial resolution.The geophysical model function(GMF),which is widely employed for wind speed retrieval from SAR data,describes the relationship between the SAR normalized radar cross-section(NRCS)at the copolarization channel(vertical-vertical and horizontal-horizontal)and a wind vector.SAR-measured NRCS at cross-polarization channels(horizontal-vertical and vertical-horizontal)correlates with wind speed.In this study,a semi-empirical algorithm is presented to retrieve wind speed from the noisy Chinese Gaofen-3(GF-3)SAR data with noise-equivalent sigma zero correction using an empirical function.GF-3 SAR can acquire data in a quad-polarization strip mode,which includes cross-polarization channels.The semi-empirical algorithm is tuned using acquisitions collocated with winds from the European Center for Medium-Range Weather Forecasts.In particular,the proposed algorithm includes the dependences of wind speed and incidence angle on cross-polarized NRCS.The accuracy of SAR-derived wind speed is around 2.10ms−1 root mean square error,which is validated against measurements from the Advanced Scatterometer onboard the Metop-A/B and the buoys from the National Data Buoy Center of the National Oceanic and Atmospheric Administration.The results obtained by the proposed algorithm considering the incidence angle in a GMF are relatively more accurate than those achieved by other algorithms.This work provides an alternative method to generate operational wind products for GF-3 SAR without relying on ancillary data for wind direction.
基金supported by the Emphases Foundation of Southwest China Institute of Electronic Technology under Grant No. H090024
文摘A feasible method for synthesizing millimeter-wave conical array and optimizing low cross-polarization is proposed.Starting from the far-field superposition principle,an efficient approach including element mutual coupling and mounted platform effects is used to calculate the far-field patterns.A coordinate transform is applied to create polarization quantities,and a general process for the element polarized pattern transformation is performed.Corresponding numerical example is given and the desired sidelobe level and low cross-polarization are optimized.The numerical results indicate the proposed method is valid.
基金The National Natural Science Foundation of China under contract No.41976169.
文摘Gaofen-3-02(GF3-02)is the first C-band synthetic aperture radar(SAR)satellite with terrain observation with progressive scans of SAR(TOPSAR)imaging mode in China,which plays an essential role in marine environment monitoring.Given the weak scattering characteristics of the ocean,the system thermal noise superimposed on SAR images has significant interference,especially in cross-polarization channels.Noise-Equivalent Sigma-Zero(NESZ)is a measure of the sensitivity of the radar to areas of low backscatter.The NESZ is defined to be the scattering cross-section coefficient of an area which contributes a mean level in the image equal to the signal-independent additive noise level.For TOPSAR,NESZ exhibits the shape of the SAR scanning gain curve in the azimuth and the shape of the antenna pattern in the range.Therefore,the accurate measurement of NESZ plays a vital role in the application of spaceborne SAR sea surface cross-polarization data.This paper proposes a theoretical calculation method for the NESZ curve in GF3-02 TOPSAR mode based on SAR noise inner calibration data and the imaging algorithm.A method for correcting the error existing in the theoretical curve of NESZ is also proposed according to the relationship between sea surface backscattering and wind speed and the same characteristics of target scattering in the overlapping area of adjacent sub-swaths.According to assessment with wide-swath TOPSAR cross-polarization data,the GF3-02 TOPSAR mode has a very low thermal noise level,which is better than−33 dB at the edge of each beam,and controlled below−38 dB at the center of the beam.The two-dimensional reference curves of the NESZ of each beam are provided to the GF3-02 TOPSAR users.After discussing the relationship between normalized radar cross section(NRCS)and wind speed,we provide a formula for NRCS related to wind speed and radar incidence angle.Compared with the NRCS derived from this formula and the NESZ-subtracted NRCS of SAR images,the bias is−0.0048 dB,the Root Mean Square Error is 1.671 dB and the correlation coefficient is 0.939.
文摘This paper presents a new blind XPIC and a new adaptive blind deconvolutional algorithm based on HOS processing, which separates and equalizes the signals in real time. The simulation results demonstrate that the performance of the proposed adaptive blind algorithm,compared with the conventional algorithms, is outstanding with the feature of feasibility, stability and fast convergence rate.
文摘Above Ground Biomass is one of the six pools identified in the inventory of forest resources and estimation of greenhouse gas emissions and sinks from the forestry sector. The pool varies by management practices in different agro-ecological or agro-climatic zones in forests. The quantification of above ground biomass (AGB) hence carbon sequestration in forests has been very difficult due to the immense costs required. This research was done to estimate AGB using ALOS PALSAR L band data (HH, HV polarisation) acquired in 2009 in relation with ground measurements data in Kericho and Aberdares ranges in Kenya. Tree data information was obtained from ground measurement of DBH and tree heights in 100 circular plots of 15 m radius, by use of random sampling technique. ALOS PALSAR image is advantageous for its active microwave sensor using L-band frequency to achieve cloud free imageries, and the ability of long wavelength cross-polarization to estimate AGB accurately for tropical forests. The variations result between Natural and plantation forest for measured and estimated biomass in Kericho HV band regression value was 0.880 and HH band was 0.520. In Aberdare ranges HV regression value of 0.708 and HH band regression value of 0.511 for measured and estimated biomass respectively. The variations can be explained by the influence of different management regimes induced human disturbances, forest stand age, density, species composition, and trees diameter distribution. However, further research is required to investigate how strong these factors affect relationship between AGB and Alos Palsar backscatters.
基金supported by the Ho Chi Minh City Department of Science and Technology of Vietnam,under grant number 116/2020/HDQPTKHCN.
文摘Collagen provides tissue strength and structural integrity.Quanti fication of the orientated dispersion of collagen fibers is an important factor when studying the mechanical properties of the cervix.In this study,for the first time,a new method for rapid characterization of the collagen fiber orientations of the cervix using linearly polarized light colposcopy is presented.A total of 24 colposcopic images were captured using a cross-polarized imaging system with white LED light sources.In the preprocessing stage,the Red channel of the RGB image was chosen,which contains no information of the blood vessels because of the low-absorption of blood cells in the red region.OrientationJ,which is an ImageJ plug-in,was used to estimate the local orientation of the collagen fibers.The result shows that in the nonpregnant cervix,the middle zone(Zone 2)has circumferentially aligned collagen fibers while the inner zone(Zone 1)has randomly arranged.The collagen fiber dispersion in Zone 2 is much smaller than that in Zone 1 at all four quadrants region(anterior,posterior,left,and right quadrant).This new analysis technique could potentially combine with diagnostic tools to provide a quantitative platform of collagen fibers in the clinic.
文摘Ⅰ. INTRODUCTIONOrganometallic complexes containing phosphorous ligands are used to catalyze various organic transformations. It is interesting that these homogeneous catalysts on polymer can facilitate the separation of the reaction products. It is more important to explore the
基金supported by the Hebei University ‘One Province One University’ Special Fundthe Opening Foundation of Machine Vision Engineering Research Center of Hebei Province ( 2018HBMV05 )the Fundamental Research Funds for the Central Universities ( 2018MS096)
文摘A geometry-based stochastic scattering model （GBSSM） based on geometrical multiple rings and ellipses is proposed for wideband multiple-input multiple-output （MIMO） mobile-to-mobile （M2M） fading channels. The proposed GBSSM is deployed with cross-polarized antennas and can be applied for the line-of-sight （LOS） and non- LOS （NLOS） scenarios by considering the single-bounced （SB） and double-bounced （DB） components. The channel realization is much more straightforward and concise to study the channel characteristics compared with the too complicated analytical solutions available so far. Based on the proposed GBSSM and realized channel, the channel characteristics and parameters at 2 GHz and 5 GHz with 100 MHz bandwidth are further investigated. The results can be used in the link and system level simulations in M2M radio systems.
