Most major oil zones in the Daqing Oilfield have reached a later,high water cut stage,but oil recovery is still only approximately 35%,and 50%of reserves remain to be recovered.The remaining oil is primarily distribut...Most major oil zones in the Daqing Oilfield have reached a later,high water cut stage,but oil recovery is still only approximately 35%,and 50%of reserves remain to be recovered.The remaining oil is primarily distributed at the edge of faults,in poor sand bodies,and in insufficiently injected and produced areas.Therefore,the edge of faults is a major target for remaining oil enrichment and potential tapping.Based on the dynamic change of production from development wells determined by the injection-recovery relationship at the edge of faults,we analyzed the control of structural features of faults on remaining oil enrichment at the edge.Our results show that the macroscopic structural features and their geometric relationship with sand bodies controlled remaining oil enrichment zones like the edges of NNE-striking faults,the footwalls of antithetic faults,the hard linkage segments（two faults had linked together with each other to form a bigger through-going fault）,the tips of faults,and the oblique anticlines of soft linkages.Fault edges formed two types of forward microamplitude structures：（1） the tilted uplift of footwalls controlled by inverse fault sections and（2） the hanging-wall horizontal anticlines controlled by synthetic fault points.The remaining oil distribution was controlled by microamplitude structures.Consequently,such zones as the tilted uplift of the footwall of the NNW-striking antithetic faults with a fault throw larger than 40 m,the hard linkage segments,the tips of faults,and the oblique anticlines of soft linkage were favorable for tapping the remaining oil potential.Multi-target directional drilling was used for remaining oil development at fault edges.Reasonable fault spacing was determined on the basis of fault combinations and width of the shattered zone.Well core and log data revealed that the width of the shattered zone on the side of the fault core was less than 15 m in general;therefore,the distance from a fault to the development target should be larger than 15 m.Vertic展开更多
In order to effectively control the working state of the gyroscope in drive mode, the drive characteristics of the micro electromechanical system （MEMS） gyroscope are analyzed in principle. A novel drive circuit for...In order to effectively control the working state of the gyroscope in drive mode, the drive characteristics of the micro electromechanical system （MEMS） gyroscope are analyzed in principle. A novel drive circuit for the MEMS gyroscope in digital closed-loop control is proposed, which utilizes a digital phase-locked loop （PLL） in frequency control and an automatic gain control （AGC） method in amplitude control. A digital processing circuit with a field programmable gate array （FPGA） is designed and the experiments are carried out. The results indicate that when the temperature changes, the drive frequency can automatically track the resonant frequency of gyroscope in drive mode and that of the oscillating amplitude holds at a set value. And at room temperature, the relative deviation of the drive frequency is 0.624 ×10^-6 and the oscillating amplitude is 8.0 ×10^-6, which are 0. 094% and 18. 39% of the analog control program, respectively. Therefore, the control solution of the digital PLL in frequency and the AGC in amplitude is feasible.展开更多
We propose a nonlinear ultrasonic technique by using the mixed-frequency signals excited Lamb waves to conduct micro-crack detection in thin plate structures.Simulation models of three-dimensional(3D)aluminum plates a...We propose a nonlinear ultrasonic technique by using the mixed-frequency signals excited Lamb waves to conduct micro-crack detection in thin plate structures.Simulation models of three-dimensional(3D)aluminum plates and composite laminates are established by ABAQUS software,where the aluminum plate contains buried crack and composite laminates comprises cohesive element whose thickness is zero to simulate delamination damage.The interactions between the S0 mode Lamb wave and the buried micro-cracks of various dimensions are simulated by using the finite element method.Fourier frequency spectrum analysis is applied to the received time domain signal and fundamental frequency amplitudes,and sum and difference frequencies are extracted and simulated.Simulation results indicate that nonlinear Lamb waves have different sensitivities to various crack sizes.There is a positive correlation among crack length,height,and sum and difference frequency amplitudes for an aluminum plate,with both amplitudes decreasing as crack thickness increased,i.e.,nonlinear effect weakens as the micro-crack becomes thicker.The amplitudes of sum and difference frequency are positively correlated with the length and width of the zero-thickness cohesive element in the composite laminates.Furthermore,amplitude ratio change is investigated and it can be used as an effective tool to detect inner defects in thin 3D plates.展开更多
Background:Optical coherence tomography angiography(OCTA)is a novel non-invasive angiography technology that has recently been extensively studied for its utility in anterior segment imaging.In this study,we compared ...Background:Optical coherence tomography angiography(OCTA)is a novel non-invasive angiography technology that has recently been extensively studied for its utility in anterior segment imaging.In this study,we compared a split-spectrum amplitude decorrelation angiography(SSADA)OCTA and an optical micro-angiography(OMAG SD)OCTA system to current angiographic technique,indocyanine green angiography(ICGA),to assess corneal vascularisation in an animal model.Methods:We imaged 16 rabbits,(one eye per animal)with corneal vascularisation using SSADA OCTA(AngioVue;Optovue Inc.,USA),OMAG OCTA(Angioscan;RS-3000 Nidek Co.Ltd.,Japan)and ICGA in the same region of interest of the cornea at successive time-points.We then analysed all scanned images for vessel density measurements and used paired t-tests and Bland-Altman plots to examine for significant differences.The en-face segmentation images from each of the OCTA scans were also extracted and were matched at every 50μm segmentation to be compared for vessel density at the respective depths.Results:Bland-Altman plots revealed a good agreement between all three imaging techniques(P>0.05)for all vessel density measurements computed,and the ranges of 95%limit of agreement were acceptable from a clinical perspective.No significant difference was reported,with ICGA(μ=16.52±8.94%)being more comparable to the OMAG OCTA(μ=16.23±9.51%;p=0.50)than the SSADA OCTA(μ=17.09±7.34%;p=0.33)system.Also,a good correlation value(r>0.9)was obtained when comparing the vessel density measurements of the en-face segmentations between the OCTA systems.Conclusions:Comparable vessel density quantification between the two OCTA systems,and with ICGA was obtained.Segmentation analysis of the vasculature at different depths showed varied performance in the two OCTA systems relative to each other.The implications of the study may help to aid in the development of better OCTA algorithms for the anterior segment and its use in clinical translational research.展开更多
基金financial support from the Natural Science Foundation of China (Grant No. 41272151, 41472126)the Natural Science Foundation for Distinguished Young Scholars of Heilongjiang Province, China (Grant No. JC201304)+1 种基金the Joint Funds of the National Natural Science Foundation of China (Grant No. U1562214)the Program for Huabei Oilfield (Grant No. HBYT-CY5-2015-JS-127)
文摘Most major oil zones in the Daqing Oilfield have reached a later,high water cut stage,but oil recovery is still only approximately 35%,and 50%of reserves remain to be recovered.The remaining oil is primarily distributed at the edge of faults,in poor sand bodies,and in insufficiently injected and produced areas.Therefore,the edge of faults is a major target for remaining oil enrichment and potential tapping.Based on the dynamic change of production from development wells determined by the injection-recovery relationship at the edge of faults,we analyzed the control of structural features of faults on remaining oil enrichment at the edge.Our results show that the macroscopic structural features and their geometric relationship with sand bodies controlled remaining oil enrichment zones like the edges of NNE-striking faults,the footwalls of antithetic faults,the hard linkage segments（two faults had linked together with each other to form a bigger through-going fault）,the tips of faults,and the oblique anticlines of soft linkages.Fault edges formed two types of forward microamplitude structures：（1） the tilted uplift of footwalls controlled by inverse fault sections and（2） the hanging-wall horizontal anticlines controlled by synthetic fault points.The remaining oil distribution was controlled by microamplitude structures.Consequently,such zones as the tilted uplift of the footwall of the NNW-striking antithetic faults with a fault throw larger than 40 m,the hard linkage segments,the tips of faults,and the oblique anticlines of soft linkage were favorable for tapping the remaining oil potential.Multi-target directional drilling was used for remaining oil development at fault edges.Reasonable fault spacing was determined on the basis of fault combinations and width of the shattered zone.Well core and log data revealed that the width of the shattered zone on the side of the fault core was less than 15 m in general;therefore,the distance from a fault to the development target should be larger than 15 m.Vertic
基金The National Natural Science Foundation of China(No. 60974116 )the Research Fund of Aeronautics Science (No.20090869007)Specialized Research Fund for the Doctoral Program of Higher Education (No. 200902861063)
文摘In order to effectively control the working state of the gyroscope in drive mode, the drive characteristics of the micro electromechanical system （MEMS） gyroscope are analyzed in principle. A novel drive circuit for the MEMS gyroscope in digital closed-loop control is proposed, which utilizes a digital phase-locked loop （PLL） in frequency control and an automatic gain control （AGC） method in amplitude control. A digital processing circuit with a field programmable gate array （FPGA） is designed and the experiments are carried out. The results indicate that when the temperature changes, the drive frequency can automatically track the resonant frequency of gyroscope in drive mode and that of the oscillating amplitude holds at a set value. And at room temperature, the relative deviation of the drive frequency is 0.624 ×10^-6 and the oscillating amplitude is 8.0 ×10^-6, which are 0. 094% and 18. 39% of the analog control program, respectively. Therefore, the control solution of the digital PLL in frequency and the AGC in amplitude is feasible.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61571222,61602235,and 11474160)the Six Talent Peaks Project of Jiangsu Province,China
文摘We propose a nonlinear ultrasonic technique by using the mixed-frequency signals excited Lamb waves to conduct micro-crack detection in thin plate structures.Simulation models of three-dimensional(3D)aluminum plates and composite laminates are established by ABAQUS software,where the aluminum plate contains buried crack and composite laminates comprises cohesive element whose thickness is zero to simulate delamination damage.The interactions between the S0 mode Lamb wave and the buried micro-cracks of various dimensions are simulated by using the finite element method.Fourier frequency spectrum analysis is applied to the received time domain signal and fundamental frequency amplitudes,and sum and difference frequencies are extracted and simulated.Simulation results indicate that nonlinear Lamb waves have different sensitivities to various crack sizes.There is a positive correlation among crack length,height,and sum and difference frequency amplitudes for an aluminum plate,with both amplitudes decreasing as crack thickness increased,i.e.,nonlinear effect weakens as the micro-crack becomes thicker.The amplitudes of sum and difference frequency are positively correlated with the length and width of the zero-thickness cohesive element in the composite laminates.Furthermore,amplitude ratio change is investigated and it can be used as an effective tool to detect inner defects in thin 3D plates.
文摘Background:Optical coherence tomography angiography(OCTA)is a novel non-invasive angiography technology that has recently been extensively studied for its utility in anterior segment imaging.In this study,we compared a split-spectrum amplitude decorrelation angiography(SSADA)OCTA and an optical micro-angiography(OMAG SD)OCTA system to current angiographic technique,indocyanine green angiography(ICGA),to assess corneal vascularisation in an animal model.Methods:We imaged 16 rabbits,(one eye per animal)with corneal vascularisation using SSADA OCTA(AngioVue;Optovue Inc.,USA),OMAG OCTA(Angioscan;RS-3000 Nidek Co.Ltd.,Japan)and ICGA in the same region of interest of the cornea at successive time-points.We then analysed all scanned images for vessel density measurements and used paired t-tests and Bland-Altman plots to examine for significant differences.The en-face segmentation images from each of the OCTA scans were also extracted and were matched at every 50μm segmentation to be compared for vessel density at the respective depths.Results:Bland-Altman plots revealed a good agreement between all three imaging techniques(P>0.05)for all vessel density measurements computed,and the ranges of 95%limit of agreement were acceptable from a clinical perspective.No significant difference was reported,with ICGA(μ=16.52±8.94%)being more comparable to the OMAG OCTA(μ=16.23±9.51%;p=0.50)than the SSADA OCTA(μ=17.09±7.34%;p=0.33)system.Also,a good correlation value(r>0.9)was obtained when comparing the vessel density measurements of the en-face segmentations between the OCTA systems.Conclusions:Comparable vessel density quantification between the two OCTA systems,and with ICGA was obtained.Segmentation analysis of the vasculature at different depths showed varied performance in the two OCTA systems relative to each other.The implications of the study may help to aid in the development of better OCTA algorithms for the anterior segment and its use in clinical translational research.
