Currently, the deghosting of towed streamer seismic data assumes a flat sea level and a sea-surface reflection coefficient of-1; this decreases the precision of deghosting. A new method that considers the rough sea su...Currently, the deghosting of towed streamer seismic data assumes a flat sea level and a sea-surface reflection coefficient of-1; this decreases the precision of deghosting. A new method that considers the rough sea surface is proposed to suppress ghost reflections. The proposed deghosting method obtains the rough sea surface reflection coefficient using Gaussian statistics, and calculates the optimized deghosting operator in the r/p domain. The proposed method is closer to the actual sea conditions, offers an improved deghosting operator, removes the ghost reflections from marine towed seismic data, widens the bandwidth and restores the low-frequency information, and finally improves the signal-to- noise ratio and resolution of the seismic data.展开更多
A novel high reflectivity type of semiconductor saturable absorption mirror grown by metal organic chemical vapor deposition is presented.Using the mirror as well as an end mirror,passively mode locked Yb∶YAB laser i...A novel high reflectivity type of semiconductor saturable absorption mirror grown by metal organic chemical vapor deposition is presented.Using the mirror as well as an end mirror,passively mode locked Yb∶YAB laser is realized,which produces a pulse as short as 3 05ps at 1 044μm.The pulse frequency is 375MHz;the output power is 45mW.展开更多
One method based on the end-face reflection as a reference was used to measure weak grating reflectivity of 0.01%-1%. For measuring ultra-weak grating reflectivity, the grating group with an identical wavelength was u...One method based on the end-face reflection as a reference was used to measure weak grating reflectivity of 0.01%-1%. For measuring ultra-weak grating reflectivity, the grating group with an identical wavelength was used. By using anhydrous alcohol and deionized water as the reflecting medium, the single- pulse FBG reflectivity of a highly doped-Ge photosensitive fiber was calculated to be about 0.747% and 0.739%, respectively; and the single-pulse FBG reflectivity of ordinary SMF fiber was about 0.016% and 0.015%, respectively. The consistent results by the two different reflecting media showed that the end-face reflection method on the grating group was feasible.展开更多
The influence of dispersion of carbon fibers in carbon-fiber-reinforced cement-based composites (CFRC) on the mechanical properties of the composites was discussed. The microstructure of the fracture surface of the ...The influence of dispersion of carbon fibers in carbon-fiber-reinforced cement-based composites (CFRC) on the mechanical properties of the composites was discussed. The microstructure of the fracture surface of the CFRC samples was observed with a scanning electron microscope (SEM). The electromagnetic interference (EMI) was evaluated indirectly by reflectivity in the Naval Research Laboratory (NRL) testing system. The reflectivity of the electromagnetic radiation by the composites was measured in the frequency range of 8.0- 18.2 GHz for different carbon fiber contents of 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% (in wt pct), respectively. The results showed that the reflectivity decreased with the growing fiber content till the percentage of 0.6%. The minimum reflectivity was -23 dB, far less than -10 dB, and the composites were strong wave absorbers. After this percentage, the curve increased abruptly as the fiber content proceeded. The electromagnetic waves were gradually reflected. When the fiber content reached 1.0% finally, the maximum reflectivity -7.5 dB appeared and there was stronger reflection. The shielding mechanism includes mainly reflection, absorption, and multiple reflections.展开更多
Cloud properties were investigated based on aircraft and cloud radar co-observation conducted at Yitong, Jilin, Northeast China. The aircraft provided in situ measurements of cloud droplet size distribution, while the...Cloud properties were investigated based on aircraft and cloud radar co-observation conducted at Yitong, Jilin, Northeast China. The aircraft provided in situ measurements of cloud droplet size distribution, while the millimeter-wavelength cloud radar vertically scanned the same cloud that the aircraft penetrated. The reflectivity factor calculated from aircraft measurements was compared in detail with sinmltaneous radar observations. The results showed that the two reflectivities were comparable in warm clouds, but in ice cloud there were more differences, which were probably associated with the occurrence of liquid water. The acceptable agreement between reflectivities obtained in water cloud confirmed that it is feasible to derive cloud properties by using aircraft data, and hence for cloud radar to remotely sense cloud properties. Based on the dataset collected in warm clouds, the threshold of reflectivity to diagnose drizzle and cloud particles was studied by analyses of the probability distribution function of reflectivity from cloud particles and drizzle drops. The relationship between refiectivity factor (Z) and cloud liquid water content (LWC) was also derived from data on both cloud particles and drizzle. In comparison with cloud droplets, the relationship for drizzle was blurred by many scatter points and thus was less evident. However, these scatters could be partly removed by filtering out the drop size distribution with a large ratio of reflectivity and large extinction coefficient but small effective radius. Empirical relationships of Z-LWC for both cloud particles and drizzle could then be derived.展开更多
We applied the reflectivity method and the constrained sparse spike inverse modeling(CSSI) method to the interpretation of coal field lithologic seismic data.After introducing the principles of these two methods we di...We applied the reflectivity method and the constrained sparse spike inverse modeling(CSSI) method to the interpretation of coal field lithologic seismic data.After introducing the principles of these two methods we discuss some parameters of a geological model involving possible gas enriched areas or intruded igneous rock.The geological model was constructed and a 60 Hz seismic response profile was obtained looking for igneous rock intrusion and coked areas of the coal seam using the reflectivity method.Starting from synthesized logging data from two wells and a synthesized seismic wavelet we calibrated the model to show accurate strata.Finally,we predicted the lithology within a 10 m igneous rock area,a 3 m coal seam area,and a coked area using the CSSI technique.The results show that the CSSI technique can identify hard to recognize lithologic features that normal profil-ing methods might miss.It can quantitatively analyze and evaluate the intrusive area,the coked area,and the gas-enriched area.展开更多
The inner surface roughness of a capillary is investigated by the reflectivity of x-rays penetrating through the capillary. The results are consistent with the data from atomic force microscope (AFM). The roughness ...The inner surface roughness of a capillary is investigated by the reflectivity of x-rays penetrating through the capillary. The results are consistent with the data from atomic force microscope (AFM). The roughness measured by this new method can reach the order of angstroms with high quality capillaries.展开更多
As a kind of mineral admixture, silica fume has low permittivity, which will affect the electromagnetic properties of cement-based materials. To study the effect of silica fume on the properties of cement-based materi...As a kind of mineral admixture, silica fume has low permittivity, which will affect the electromagnetic properties of cement-based materials. To study the effect of silica fume on the properties of cement-based materials, the reflectivity, transmission efficiency and pore structure were analyzed by using the vector network analyzer and mercury injection apparatus. Results show that silica fume can make the mortar more compact and the porosity of sample with 9% silica fume is only 17.8%, which is far lower than the control sample;With the increase of the silica fume content, the peak of reflectivity curve increases from -23.2 dB to -16.0 dB, and then decreases from -16.04 dB to -28.7 dB in the frequency range of 6 – 18 GHz. Reflectivity of sample with 3% content of silica fume is lower than other samples within 26.5 - 40 GHz;Transmission efficiency of samples shows the trend of increase with silica fume content increases from 0% to 6% within 8.2 - 12.4 GHz, 12 - 18 GHz and 26.5 - 40 GHz, but when the content increases from 6% to 9%, the transmission efficiency of samples reduces.展开更多
Most current prestack AVA joint inversion methods are based on the exact Zoeppritz equation and its various approximations. However, these equations only reflect the relation between reflection coefficients, incidence...Most current prestack AVA joint inversion methods are based on the exact Zoeppritz equation and its various approximations. However, these equations only reflect the relation between reflection coefficients, incidence angles, and elastic parameters on either side of the interface, which means that wave-propagation effects, such as spherical spreading, attenuation, transmission loss, multiples, and event mismatching of P-and S-waves, are not considered and cannot accurately describe the true propagation characteristics of seismic waves. Conventional AVA inversion methods require that these wave-propagation effects have been fully corrected or attenuated before inversion but these requirements can hardly be satisfied in practice. Using a one-dimensional(1 D) earth model, the reflectivity method can simulate the full wavefield response of seismic waves. Therefore, we propose a nonlinear multicomponent prestack AVA joint inversion method based on the vectorized reflectivity method, which uses a fast nondominated sorting genetic algorithm(NSGA II) to optimize the nonlinear multiobjective function to estimate multiple parameters, such as P-wave velocity, S-wave velocity, and density. This approach is robust because it can simultaneously cope with more than one objective function without introducing weight coefficients. Model tests prove the effectiveness of the proposed inversion method. Based on the inversion results, we find that the nonlinear prestack AVA joint inversion using the reflectivity method yields more accurate inversion results than the inversion by using the exact Zoeppritz equation when the wave-propagation effects of transmission loss and internal multiples are not completely corrected.展开更多
Relation between the volume reflectivity and frequency in view of the polar mesosphere summer echoes (PMSE) is studied using the small-scale structure of electron density caused by charged dust particles. A theoreti...Relation between the volume reflectivity and frequency in view of the polar mesosphere summer echoes (PMSE) is studied using the small-scale structure of electron density caused by charged dust particles. A theoretical expression for the radar volume reflectivity is derived, which agrees with the statistical result. Both the theoretical and statistical results are confirmed with the data obtained from simultaneous observations at three frequencies. Hence the small-scale structure caused by charged dust particles may be a useful tool for the study on the generation mechanism of PMSE.展开更多
From first principles, we find that the radar threshold reflectivity between nonprecipitating clouds and precipitating clouds is strongly related to not only the cloud droplet number concentration but also the spectra...From first principles, we find that the radar threshold reflectivity between nonprecipitating clouds and precipitating clouds is strongly related to not only the cloud droplet number concentration but also the spectral dispersion of cloud droplet size distributions. The further investigation indicates that the threshold value is an increasing function of spectral dispersion and cloud droplet number concentration. These results may improve our understanding of the cloud-precipitation interaction and the aerosol indirect effect.展开更多
In this work, the wafer bowing during growth can be in-situ measured by a reflectivity mapping method in the 3×2 Thomas Swan close coupled showerhead metal organic chemical vapor deposition(MOCVD) system. The r...In this work, the wafer bowing during growth can be in-situ measured by a reflectivity mapping method in the 3×2 Thomas Swan close coupled showerhead metal organic chemical vapor deposition(MOCVD) system. The reflectivity mapping method is usually used to measure the film thickness and growth rate. The wafer bowing caused by stresses(tensile and compressive) during the epitaxial growth leads to a temperature variation at different positions on the wafer, and the lower growth temperature leads to a faster growth rate and vice versa. Therefore, the wafer bowing can be measured by analyzing the discrepancy of growth rates at different positions on the wafer. Furthermore, the wafer bowings were confirmed by the ex-situ wafer bowing measurement. High-resistivity and low-resistivity Si substrates were used for epitaxial growth. In comparison with low-resistivity Si substrate, Ga N grown on high-resistivity substrate shows a larger wafer bowing caused by the highly compressive stress introduced by compositionally graded Al Ga N buffer layer. This transition of wafer bowing can be clearly in-situ measured by using the reflectivity mapping method.展开更多
AIM: To evaluate the use of short-duration transient visual evoked potentials(VEP) and color reflectivity discretization analysis(CORDA) in glaucomatous eyes,eyes suspected of having glaucoma,and healthy eyes.MET...AIM: To evaluate the use of short-duration transient visual evoked potentials(VEP) and color reflectivity discretization analysis(CORDA) in glaucomatous eyes,eyes suspected of having glaucoma,and healthy eyes.METHODS: The study included 136 eyes from 136 subjects: 49 eyes with glaucoma,45 glaucoma suspect eyes,and 42 healthy eyes.Subjects underwent Humphrey visual field(VF) testing,VEP testing,as well as peripapillary retinal nerve fiber layer optical coherence tomography imaging studies with post-acquisition CORDA applied.Statistical analysis was performed using means and ranges,ANOVA,post-hoc comparisons using Turkey's adjustment,Fisher's Exact test,area under the curve,and Spearman correlation coefficients.RESULTS: Parameters from VEP and CORDA correlated significantly with VF mean deviation(MD)(P〈0.05).In distinguishing glaucomatous eyes from controls,VEP demonstrated area under the curve(AUC) values of 0.64-0.75 for amplitude and 0.67-0.81 for latency.The CORDA HR1 parameter was highly discriminative for glaucomatous eyes vs controls(AUC=0.94).CONCLUSION: Significant correlations are found between MD and parameters of short-duration transient VEP and CORDA,diagnostic modalities which warrant further consideration in identifying glaucoma characteristics.展开更多
基金supported by the 12th Five Year Plan National Science and Technology Major Projects(No.20011ZX05023-003-002)Research projects of CNOOC(No.C/KJF JDCJF 006-2009)
文摘Currently, the deghosting of towed streamer seismic data assumes a flat sea level and a sea-surface reflection coefficient of-1; this decreases the precision of deghosting. A new method that considers the rough sea surface is proposed to suppress ghost reflections. The proposed deghosting method obtains the rough sea surface reflection coefficient using Gaussian statistics, and calculates the optimized deghosting operator in the r/p domain. The proposed method is closer to the actual sea conditions, offers an improved deghosting operator, removes the ghost reflections from marine towed seismic data, widens the bandwidth and restores the low-frequency information, and finally improves the signal-to- noise ratio and resolution of the seismic data.
文摘A novel high reflectivity type of semiconductor saturable absorption mirror grown by metal organic chemical vapor deposition is presented.Using the mirror as well as an end mirror,passively mode locked Yb∶YAB laser is realized,which produces a pulse as short as 3 05ps at 1 044μm.The pulse frequency is 375MHz;the output power is 45mW.
基金Funded by the National Natural Science Foundation of China (Nos.61205070 and 61290311)
文摘One method based on the end-face reflection as a reference was used to measure weak grating reflectivity of 0.01%-1%. For measuring ultra-weak grating reflectivity, the grating group with an identical wavelength was used. By using anhydrous alcohol and deionized water as the reflecting medium, the single- pulse FBG reflectivity of a highly doped-Ge photosensitive fiber was calculated to be about 0.747% and 0.739%, respectively; and the single-pulse FBG reflectivity of ordinary SMF fiber was about 0.016% and 0.015%, respectively. The consistent results by the two different reflecting media showed that the end-face reflection method on the grating group was feasible.
基金supported by the National Natural Science Foundation of China under grant No.50172039.
文摘The influence of dispersion of carbon fibers in carbon-fiber-reinforced cement-based composites (CFRC) on the mechanical properties of the composites was discussed. The microstructure of the fracture surface of the CFRC samples was observed with a scanning electron microscope (SEM). The electromagnetic interference (EMI) was evaluated indirectly by reflectivity in the Naval Research Laboratory (NRL) testing system. The reflectivity of the electromagnetic radiation by the composites was measured in the frequency range of 8.0- 18.2 GHz for different carbon fiber contents of 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% (in wt pct), respectively. The results showed that the reflectivity decreased with the growing fiber content till the percentage of 0.6%. The minimum reflectivity was -23 dB, far less than -10 dB, and the composites were strong wave absorbers. After this percentage, the curve increased abruptly as the fiber content proceeded. The electromagnetic waves were gradually reflected. When the fiber content reached 1.0% finally, the maximum reflectivity -7.5 dB appeared and there was stronger reflection. The shielding mechanism includes mainly reflection, absorption, and multiple reflections.
基金supported by the National Key Program for Developing Basic Sciences under Grant 2012CB417202the National Natural Science Foundation of China under Grant Nos. 40975014, 41030962 and 41175038sponsored by the Program for Postgraduates Research Innovation of Jiangsu Higher Education Institutions (Grant No. CXZZ11-0615)
文摘Cloud properties were investigated based on aircraft and cloud radar co-observation conducted at Yitong, Jilin, Northeast China. The aircraft provided in situ measurements of cloud droplet size distribution, while the millimeter-wavelength cloud radar vertically scanned the same cloud that the aircraft penetrated. The reflectivity factor calculated from aircraft measurements was compared in detail with sinmltaneous radar observations. The results showed that the two reflectivities were comparable in warm clouds, but in ice cloud there were more differences, which were probably associated with the occurrence of liquid water. The acceptable agreement between reflectivities obtained in water cloud confirmed that it is feasible to derive cloud properties by using aircraft data, and hence for cloud radar to remotely sense cloud properties. Based on the dataset collected in warm clouds, the threshold of reflectivity to diagnose drizzle and cloud particles was studied by analyses of the probability distribution function of reflectivity from cloud particles and drizzle drops. The relationship between refiectivity factor (Z) and cloud liquid water content (LWC) was also derived from data on both cloud particles and drizzle. In comparison with cloud droplets, the relationship for drizzle was blurred by many scatter points and thus was less evident. However, these scatters could be partly removed by filtering out the drop size distribution with a large ratio of reflectivity and large extinction coefficient but small effective radius. Empirical relationships of Z-LWC for both cloud particles and drizzle could then be derived.
基金Projects 40874054 and 40804026 supported by the National Natural Science Foundation of Chinathe National Basic Research Program of China (2007CB209400 and 2009CB219603)the National Key Scientific and Technological Project (2008ZX05035)
文摘We applied the reflectivity method and the constrained sparse spike inverse modeling(CSSI) method to the interpretation of coal field lithologic seismic data.After introducing the principles of these two methods we discuss some parameters of a geological model involving possible gas enriched areas or intruded igneous rock.The geological model was constructed and a 60 Hz seismic response profile was obtained looking for igneous rock intrusion and coked areas of the coal seam using the reflectivity method.Starting from synthesized logging data from two wells and a synthesized seismic wavelet we calibrated the model to show accurate strata.Finally,we predicted the lithology within a 10 m igneous rock area,a 3 m coal seam area,and a coked area using the CSSI technique.The results show that the CSSI technique can identify hard to recognize lithologic features that normal profil-ing methods might miss.It can quantitatively analyze and evaluate the intrusive area,the coked area,and the gas-enriched area.
基金supported by the Natural Science Foundation of Beijing,China (Grant No. 1102019)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20100003120010)
文摘The inner surface roughness of a capillary is investigated by the reflectivity of x-rays penetrating through the capillary. The results are consistent with the data from atomic force microscope (AFM). The roughness measured by this new method can reach the order of angstroms with high quality capillaries.
文摘As a kind of mineral admixture, silica fume has low permittivity, which will affect the electromagnetic properties of cement-based materials. To study the effect of silica fume on the properties of cement-based materials, the reflectivity, transmission efficiency and pore structure were analyzed by using the vector network analyzer and mercury injection apparatus. Results show that silica fume can make the mortar more compact and the porosity of sample with 9% silica fume is only 17.8%, which is far lower than the control sample;With the increase of the silica fume content, the peak of reflectivity curve increases from -23.2 dB to -16.0 dB, and then decreases from -16.04 dB to -28.7 dB in the frequency range of 6 – 18 GHz. Reflectivity of sample with 3% content of silica fume is lower than other samples within 26.5 - 40 GHz;Transmission efficiency of samples shows the trend of increase with silica fume content increases from 0% to 6% within 8.2 - 12.4 GHz, 12 - 18 GHz and 26.5 - 40 GHz, but when the content increases from 6% to 9%, the transmission efficiency of samples reduces.
基金supported by the National Science and Technology Major Project(No.2016ZX05003-003)
文摘Most current prestack AVA joint inversion methods are based on the exact Zoeppritz equation and its various approximations. However, these equations only reflect the relation between reflection coefficients, incidence angles, and elastic parameters on either side of the interface, which means that wave-propagation effects, such as spherical spreading, attenuation, transmission loss, multiples, and event mismatching of P-and S-waves, are not considered and cannot accurately describe the true propagation characteristics of seismic waves. Conventional AVA inversion methods require that these wave-propagation effects have been fully corrected or attenuated before inversion but these requirements can hardly be satisfied in practice. Using a one-dimensional(1 D) earth model, the reflectivity method can simulate the full wavefield response of seismic waves. Therefore, we propose a nonlinear multicomponent prestack AVA joint inversion method based on the vectorized reflectivity method, which uses a fast nondominated sorting genetic algorithm(NSGA II) to optimize the nonlinear multiobjective function to estimate multiple parameters, such as P-wave velocity, S-wave velocity, and density. This approach is robust because it can simultaneously cope with more than one objective function without introducing weight coefficients. Model tests prove the effectiveness of the proposed inversion method. Based on the inversion results, we find that the nonlinear prestack AVA joint inversion using the reflectivity method yields more accurate inversion results than the inversion by using the exact Zoeppritz equation when the wave-propagation effects of transmission loss and internal multiples are not completely corrected.
基金supported by National Natural Science Foundation of China (No.40831062)the Foundation of the National Key Laboratory of Electromagnetic Environment of China (No.9140C08060367ZCZJ16)
文摘Relation between the volume reflectivity and frequency in view of the polar mesosphere summer echoes (PMSE) is studied using the small-scale structure of electron density caused by charged dust particles. A theoretical expression for the radar volume reflectivity is derived, which agrees with the statistical result. Both the theoretical and statistical results are confirmed with the data obtained from simultaneous observations at three frequencies. Hence the small-scale structure caused by charged dust particles may be a useful tool for the study on the generation mechanism of PMSE.
基金Project supported by the Special Foundation for China Nonprofit Industry (Grant No. GYHY200706036)the National Excellent Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 40825008)the National Basic Research Program of China (Grant No. 2010CB833406)
文摘From first principles, we find that the radar threshold reflectivity between nonprecipitating clouds and precipitating clouds is strongly related to not only the cloud droplet number concentration but also the spectral dispersion of cloud droplet size distributions. The further investigation indicates that the threshold value is an increasing function of spectral dispersion and cloud droplet number concentration. These results may improve our understanding of the cloud-precipitation interaction and the aerosol indirect effect.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61274039 and 51177175)the National Basic Research Program of China(Grant No.2011CB301903)+5 种基金the Ph.D.Programs Foundation of Ministry of Education of China(Grant No.20110171110021)the International Science and Technology Collaboration Program of China(Grant No.2012DFG52260)the International Science and Technology Collaboration Program of Guangdong Province,China(Grant No.2013B051000041)the Science and Technology Plan of Guangdong Province,China(Grant No.2013B010401013)the National High Technology Research and Development Program of China(Grant No.2014AA032606)the Opened Fund of the State Key Laboratory on Integrated Optoelectronics,China(Grant No.IOSKL2014KF17)
文摘In this work, the wafer bowing during growth can be in-situ measured by a reflectivity mapping method in the 3×2 Thomas Swan close coupled showerhead metal organic chemical vapor deposition(MOCVD) system. The reflectivity mapping method is usually used to measure the film thickness and growth rate. The wafer bowing caused by stresses(tensile and compressive) during the epitaxial growth leads to a temperature variation at different positions on the wafer, and the lower growth temperature leads to a faster growth rate and vice versa. Therefore, the wafer bowing can be measured by analyzing the discrepancy of growth rates at different positions on the wafer. Furthermore, the wafer bowings were confirmed by the ex-situ wafer bowing measurement. High-resistivity and low-resistivity Si substrates were used for epitaxial growth. In comparison with low-resistivity Si substrate, Ga N grown on high-resistivity substrate shows a larger wafer bowing caused by the highly compressive stress introduced by compositionally graded Al Ga N buffer layer. This transition of wafer bowing can be clearly in-situ measured by using the reflectivity mapping method.
文摘AIM: To evaluate the use of short-duration transient visual evoked potentials(VEP) and color reflectivity discretization analysis(CORDA) in glaucomatous eyes,eyes suspected of having glaucoma,and healthy eyes.METHODS: The study included 136 eyes from 136 subjects: 49 eyes with glaucoma,45 glaucoma suspect eyes,and 42 healthy eyes.Subjects underwent Humphrey visual field(VF) testing,VEP testing,as well as peripapillary retinal nerve fiber layer optical coherence tomography imaging studies with post-acquisition CORDA applied.Statistical analysis was performed using means and ranges,ANOVA,post-hoc comparisons using Turkey's adjustment,Fisher's Exact test,area under the curve,and Spearman correlation coefficients.RESULTS: Parameters from VEP and CORDA correlated significantly with VF mean deviation(MD)(P〈0.05).In distinguishing glaucomatous eyes from controls,VEP demonstrated area under the curve(AUC) values of 0.64-0.75 for amplitude and 0.67-0.81 for latency.The CORDA HR1 parameter was highly discriminative for glaucomatous eyes vs controls(AUC=0.94).CONCLUSION: Significant correlations are found between MD and parameters of short-duration transient VEP and CORDA,diagnostic modalities which warrant further consideration in identifying glaucoma characteristics.