Displacement-imbibition coupling production is a pivotal technology for enhancing oil recovery(EOR)in waterflooded tight/shale oil reservoirs.However,the microscopic fluid transport mechanisms across different pore sc...Displacement-imbibition coupling production is a pivotal technology for enhancing oil recovery(EOR)in waterflooded tight/shale oil reservoirs.However,the microscopic fluid transport mechanisms across different pore scales remain inadequately understood.This study presents an innovative real-time nuclear magnetic resonance(NMR)experimental system integrated with MRI-based image processing to dynamically monitor oil-water distribution and quantify local oil saturation during injection-shut-in-production.This approach enables quantitative evaluation of pore utilization across different pore size ranges and reveals the impacts of various driving forces on oil displacement efficiency.The results show that displacement-imbibition coupling production employs multiple mechanisms to achieve balanced contributions from pores of all size scales.The displacement-imbibition oil production mainly consists of three stages:displacement-dominated injection,capillary-driven imbibition during shut-in,and displacement-imbibition coupling effects during production.Pressure oscillations significantly enhance matrix-fracture exchange by lowering pore-throat entry thresholds and redistributing pressure fields.Quantitative analysis shows that large pore dominate early displacement,while small pore contribute more during imbibition.Lithology and pore-throat connectivity critically influence displacement efficiency;vitric tuff outperforms argillaceous siltstone by up to 11.8%.Notably,greater fracture complexity increases the oil-water contact area,enhancing capillary imbibition,reducing reliance on displacement forces,and increasing the contribution of displacement-imbibition coupling effects to oil displacement efficiency by 15.35%.Artificially modifying the pressure field to induce pressure oscillations,effectively utilizing the high conductivity of fractures,and fully leveraging the displacement-imbibition coupling effects within matrix pores are crucial for achieving optimal EOR.Lastly,a new concept of nonlinear flow zoning is introduced to describe spatial variations in flow behavior under complex coupling conditions.These experimentally validated insights into matrix-fracture interactions provide theoretical support for designing improved waterflooding strategies and optimizing oil recovery in tight and shale reservoirs.展开更多
The spatial-temporal relationship between high-quality source rocks and reservoirs is a key factor when evaluating the formation,occurrence,and prospectivity of tight oil and gas reservoirs.In this study,we analyze th...The spatial-temporal relationship between high-quality source rocks and reservoirs is a key factor when evaluating the formation,occurrence,and prospectivity of tight oil and gas reservoirs.In this study,we analyze the fundamental oil and gas accumulation processes occurring in the Songliao Basin,contrasting tight oil sand reservoirs in the south with tight gas sand reservoirs in the north.This is done using geochemical data,constant-rate and conventional mercury injection experiments,and fluid inclusion analyses.Our results demonstrate that as far as fluid mobility is concerned,the expulsion center coincides with the overpressure zone,and its boundary limits the occurrence of tight oil and gas accumulations.In addition,the lower permeability limit of high-quality reservoirs,controlled by pore-throat structures,is 0.1×10^-3μm^2 in the fourth member of the Lower Cretaceous Quantou Formation(K1q^4)in the southern Songliao Basin,and 0.05×10^-3μm^2 in the Lower Cretaceous Shahezi Formation(K1sh)in the northern Songliao Basin.Furthermore,the results indicate that the formation of tight oil and gas reservoirs requires the densification of reservoirs prior to the main phase of hydrocarbon expulsion from the source rocks.Reservoir“sweet spots”develop at the intersection of high-quality source rocks(with high pore pressure)and reservoirs(with high permeability).展开更多
The indoor positioning system is now an important technique as part of the Internet-of-Things(IoT)ecosystem.Among indoor positioning techniques,multiple Wi-Fi Access Points(APs)-based positioning systems have been res...The indoor positioning system is now an important technique as part of the Internet-of-Things(IoT)ecosystem.Among indoor positioning techniques,multiple Wi-Fi Access Points(APs)-based positioning systems have been researched a lot.There is a lack of research focusing on the scene where only one Wi-Fi AP is available.This work proposes a hybrid indoor positioning system that takes advantage of the Fine-Timing Measurements(FTM)technique that is part of the IEEE 802.11mc standard,introduced back in 2016.The system uses one single Wi-Fi FTM AP and takes advantage of the built-in inertial sensors of the smartphone to estimate the device’s position.We explore both Loosely Coupled(LC)and Tightly Coupled(TC)integration schemes for the sensors’data fusion.Experimental results show that the proposed methods can achieve an average positioning accuracy of about 1 m without knowing the initial position.Compared with the LC integration method,the median error accuracy of the proposed TC fusion algorithm has improved by more than 52%and 67%,respectively,in the two experiments we set up.展开更多
Deep learning-based wind turbine blade fault diagnosis has been widely applied due to its advantages in end-to-end feature extraction.However,several challenges remain.First,signal noise collected during blade operati...Deep learning-based wind turbine blade fault diagnosis has been widely applied due to its advantages in end-to-end feature extraction.However,several challenges remain.First,signal noise collected during blade operation masks fault features,severely impairing the fault diagnosis performance of deep learning models.Second,current blade fault diagnosis often relies on single-sensor data,resulting in limited monitoring dimensions and ability to comprehensively capture complex fault states.To address these issues,a multi-sensor fusion-based wind turbine blade fault diagnosis method is proposed.Specifically,a CNN-Transformer Coupled Feature Learning Architecture is constructed to enhance the ability to learn complex features under noisy conditions,while a Weight-Aligned Data Fusion Module is designed to comprehensively and effectively utilize multi-sensor fault information.Experimental results of wind turbine blade fault diagnosis under different noise interferences show that higher accuracy is achieved by the proposed method compared to models with single-source data input,enabling comprehensive and effective fault diagnosis.展开更多
An Extended Kalman Filter（EKF） is commonly used to fuse raw Global Navigation Satellite System（GNSS） measurements and Inertial Navigation System（INS） derived measurements. However, the Conventional EKF（CEKF） s...An Extended Kalman Filter（EKF） is commonly used to fuse raw Global Navigation Satellite System（GNSS） measurements and Inertial Navigation System（INS） derived measurements. However, the Conventional EKF（CEKF） suffers the problem for which the uncertainty of the statistical properties to dynamic and measurement models will degrade the performance.In this research, an Adaptive Interacting Multiple Model（AIMM） filter is developed to enhance performance. The soft-switching property of Interacting Multiple Model（IMM） algorithm allows the adaptation between two levels of process noise, namely lower and upper bounds of the process noise. In particular, the Sage adaptive filtering is applied to adapt the measurement covariance on line. In addition, a classified measurement update strategy is utilized, which updates the pseudorange and Doppler observations sequentially. A field experiment was conducted to validate the proposed algorithm, the pseudorange and Doppler observations from Global Positioning System（GPS） and Bei Dou Navigation Satellite System（BDS） were post-processed in differential mode.The results indicate that decimeter-level positioning accuracy is achievable with AIMM for GPS/INS and GPS/BDS/INS configurations, and the position accuracy is improved by 35.8%, 34.3% and 33.9% for north, east and height components, respectively, compared to the CEKF counterpartfor GPS/BDS/INS. Degraded performance for BDS/INS is obtained due to the lower precision of BDS pseudorange observations.展开更多
We develop a new integrated navigation system, which integrates multi-constellations GNSS precise point positioning (PPP), including GPS, GLONASS and Galileo, with low-cost micro-electro-mechanical sensor (MEMS) inert...We develop a new integrated navigation system, which integrates multi-constellations GNSS precise point positioning (PPP), including GPS, GLONASS and Galileo, with low-cost micro-electro-mechanical sensor (MEMS) inertial system, for precise positioning applications. To integrate GNSS and the MEMS-based inertial system, the process and measurement models are developed. Tightly coupled mechanism is adopted, which is carried out in the GNSS raw measurements domain. Both un-differenced and between-satellite single-difference (BSSD) ionosphere-free linear combinations of pseudorange and carrier phase GNSS measurements are processed. Rigorous models are employed to correct GNSS errors and biases. The GNSS inter-system biases are considered as additional unknowns in the integrated error state vector. The developed stochastic model for inertial sensors errors and biases are defined based on first order Gaussian Markov process. Extended Kalman filter is developed to integrate GNSS and inertial measurements and estimate inertial measurements biases and errors. Two field experiments are executed, which represent different real-world scenarios in land-based navigation. The data are processed by using our developed Ryerson PPP GNSS/MEMS software. The results indicate that the proposed integrated system achieves decimeter to centimeter level positioning accuracy when the measurement updates from GNSS are available. During complete GNSS outages the developed integrated system continues to achieve decimeter level accuracy for up to 30 seconds while it achieves meter-level accuracy when a 60-second outage is introduced.展开更多
A mathematical model, fully coupling multiple porous media deformation and fluid flow, was established based on the elastic theory of porous media and fluid-solid coupling mechanism in tight oil reservoirs. The finite...A mathematical model, fully coupling multiple porous media deformation and fluid flow, was established based on the elastic theory of porous media and fluid-solid coupling mechanism in tight oil reservoirs. The finite element method was used to determine the numerical solution and the accuracy of the model was verified. On this basis, the model was used to simulate productivity of multistage fractured horizontal wells in tight oil reservoirs. The results show that during the production of tight oil wells, the reservoir region close to artificial fractures deteriorated in physical properties significantly, e.g. the aperture and conductivity of artificial fractures dropped by 52.12% and 89.02% respectively. The simulations of 3000-day production of a horizontal well in tight oil reservoir showed that the predicted productivity by the uncoupled model had an error of 38.30% from that by the fully-coupled model. Apparently, ignoring the influence of fluid-solid interaction effect led to serious deviations of the productivity prediction results. The productivity of horizontal well in tight oil reservoir was most sensitive to the start-up pressure gradient, and second most sensitive to the opening of artificial fractures. Enhancing the initial conductivity of artificial fractures was helpful to improve the productivity of tight oil wells. The influence of conductivity, spacing, number and length of artificial fractures should be considered comprehensively in fracturing design. Increasing the number of artificial fractures unilaterally could not achieve the expected increase in production.展开更多
The Chang-63 reservoir in the Huaqing area has widely developed tight sandstone ＂thick sand layers, but not reservoirs characterized by rich in oil＂, and it is thus necessary to further study its oil and gas enrichm...The Chang-63 reservoir in the Huaqing area has widely developed tight sandstone ＂thick sand layers, but not reservoirs characterized by rich in oil＂, and it is thus necessary to further study its oil and gas enrichment law. This study builds porosity and fracture development and evolution models in different deposition environments, through core observation, casting thin section, SEM, porosity and permeability analysis, burial history analysis, and ＂four-property-relationships＂ analysis.展开更多
A tightly coupled GPS （ global positioning system ）/SINS （ strap down inertial navigation system） based on a GMDH （ group method of data handling） neural network was presented to solve the problem of degraded ac...A tightly coupled GPS （ global positioning system ）/SINS （ strap down inertial navigation system） based on a GMDH （ group method of data handling） neural network was presented to solve the problem of degraded accuracy for less than four visible GPS satellites with poor signal quality. Positions and velocities of the satellites were predicted by a GMDH neural network, and the pseudo ranges and pseudo range rates received by the GPS receiver were simulated to ensure the regular op eration of the GPS/SINS Kalman filter during outages. In the mathematical simulation a tightly cou pled navigation system with a proposed approach has better navigation accuracy during GPS outages, and the anti jamming ability is strengthened for the tightly coupled navigation system.展开更多
Against the backdrop of electromagnetic space integration,the radio system of equipment platforms,such as next-generation aircraft,must possess multifunctional integration and electromagnetic stealth performance.Meanw...Against the backdrop of electromagnetic space integration,the radio system of equipment platforms,such as next-generation aircraft,must possess multifunctional integration and electromagnetic stealth performance.Meanwhile,the equipment platforms need to evolve towards flat structures.These requirements pose significant technical challenges for antenna system design.The antenna must possess ultra-wideband to facilitate multi-function integration through the use of continuous radio frequency synthetic aperture.In order to ensure good aerodynamics of the flat airborne platform,it is required to implement conformal design,while the ultra-low profile is the greatest challenge in conformal design.Against this background,this work proposes a novel airborne tightly coupled antenna with ultra-low profile,ultra-wideband,and vertical-polarized omnidirectional radiation.The antenna unit utilizes a long slot structure and implements circular conformal design,where the resistive frequency selection surface is used to expand the operating bandwidth.This antenna has a profile height of only 0.047 times the low-frequency wavelength.Simulation and measurement results show that it achieves an impedance bandwidth of nearly 12∶1 with omnidirectional beam coverage,which meets the requirements of multifunctional future airborne antennas.展开更多
Two types of tightly coupled Selective Catalytic Reduction(SCR)mixers were designed in this study,namely Mixer 1 integrated with an SCR catalyst and Mixer 2 arranged separately.Computational Fluid Dynamics(CFD)softwar...Two types of tightly coupled Selective Catalytic Reduction(SCR)mixers were designed in this study,namely Mixer 1 integrated with an SCR catalyst and Mixer 2 arranged separately.Computational Fluid Dynamics(CFD)software was utilized to model the gas flow,spraying,and pyrolysis reaction of the aqueous urea solution in the tightly coupled SCR system.The parameters of gas flow velocity uniformity and ammonia distribution uniformity were simulated and calculated for both Mixer 1 and Mixer 2 in the tightly coupled SCR system to compare their advantages and disadvantages.The simulation results indicated that Mixer 1 exhibited a gas velocity uniformity of 0.972 and an ammonia distribution uniformity of 0.817,whereas Mixer 2 demonstrated a gas velocity uniformity of 0.988 and an ammonia distribution uniformity of 0.964.Mixer 2 performed better in the simulation analysis.Furthermore,a 3D-printed prototype of Mixer 2 was manufactured and installed on an engine test bench to investigate ammonia distribution uniformity and NOX conversion efficiency.The experimental investigations yielded the following findings:1)The ammonia distribution uniformity of Mixer 2 was measured as 0.976,which closely aligned with the simulation result of 0.964,with a deviation of 1.2%from the model calculations;2)As exhaust temperature increased,the ammonia distribution uniformity gradually improved,while an increase in exhaust flow rate resulted in a decrease in ammonia distribution uniformity;3)When utilizing Mixer 2,the NOX conversion efficiency reached 84.7%at an exhaust temperature of 200°C and 97.4%at 250°C.Within the exhaust temperature range of 300°C to 450°C,the NOX conversion efficiency remained above 98%.This study proposed two innovative mixer structures,conducted simulation analysis,and performed performance testing.The research outcomes indicated that the separately arranged Mixer 2 exhibited superior performance.The tightly coupled SCR systemequippedwith Mixer 2 achieved excellent levels of gas velocity uniformity,ammonia distribution uniformity,and NOX conversion efficiency.These findings can serve as valuable references for the design and development of ultra-low emission after-treatment systems for diesel engines in the field of diesel engine aftertreatment.展开更多
The seepage characteristics of shale reservoirs are influenced not only by multi-field coupling effects such as stress field,temperature field,and seepage field but also exhibit evident creep characteristics during oi...The seepage characteristics of shale reservoirs are influenced not only by multi-field coupling effects such as stress field,temperature field,and seepage field but also exhibit evident creep characteristics during oil and gas exploitation.The complex fluid flow in such reservoirs is analyzed using a combination of theoretical modeling and numerical simulation.This study develops a comprehensive mathematical model that integrates the impact of creep on the seepage process,with consideration of factors including stress,strain,and time-dependent deformation.The model is validated through a series of numerical experiments,which demonstrate the significant influence of creep on the seepage behavior.The results indicate that the rock mechanical parameters and creep constitutive model were determined through triaxial compression tests and uniaxial creep tests.A creep-seepage coupling control equation for shale was established based on the Burgers creep model.The absolute value of the volumetric strain of shale increases rapidly in the initial creep stage,and the increase in vertical stress accelerates the rock’s creep deformation.During the deceleration creep stage,the volumetric strain of the reservoir increases rapidly,leading to a significant decrease in permeability.In the stable creep stage,the pores and fractures in the rock are further compressed,causing a gradual reduction in permeability,which eventually stabilizes.展开更多
针对现代化鹅养殖场景中饲料投喂移动小车受动态鹅群干扰,致使同时定位与地图构建(Simultaneous Localization And Mapping,SLAM)算法的定位精度、建图质量下降的问题,提出基于多传感融合目标检测的动态SLAM算法。该算法以LIO-SAM框架...针对现代化鹅养殖场景中饲料投喂移动小车受动态鹅群干扰,致使同时定位与地图构建(Simultaneous Localization And Mapping,SLAM)算法的定位精度、建图质量下降的问题,提出基于多传感融合目标检测的动态SLAM算法。该算法以LIO-SAM框架为基础,融合激光雷达与惯性测量单元搭建SLAM系统,采用前后端架构优化定位与建图性能;运用匈牙利算法实时追踪鹅群运动状态,结合多传感融合目标检测算法,精准识别并剔除动态鹅群产生的特征点,有效降低定位与建图误差。经KITTI、UrbanNav等公共数据集与实际养殖场景数据测试,在KITTI07序列中,较LeGO-LOAM、LIO-SAM和LVI-SAM等经典算法,均方根误差(RMSE)降低33.18%;在实际鹅养殖环境中,可以快速滤除动态鹅群干扰,提升建图质量与导航可靠性。本研究为智能化鹅养殖饲料投喂提供了新的技术方案,推动了畜牧业自动化发展。展开更多
To investigate the 4D stress change during injection and production in tight sandstone reservoirs, a multi-physical fields modeling method is proposed considering the reservoir heterogeneity, hydraulic fracture and co...To investigate the 4D stress change during injection and production in tight sandstone reservoirs, a multi-physical fields modeling method is proposed considering the reservoir heterogeneity, hydraulic fracture and complex injection-production system. The 4D stress evolution of tight sandstone reservoir in Yuan 284 block of Huaqing oilfield, Ordos Basin,during injection-production in horizontal well network is investigated by modeling coupled flow and geomechanics. Results show:(1) Induced by injection and production, the 3D stress increases near the injectors but decreases near the producers, and the horizontal stresses are distributed in obvious strips along their respective stress directions.(2) The horizontal stress difference is the highest at the horizontal wellbore beside injectors during injection and production, while it is the lowest in undeveloped zone between the injectors, and the orientation of maximum horizontal principal stress changes the most near the injectors, which is distributed radially.(3) The hydraulic fracture in re-fracturing well was observed to be asymmetrical in geometry and deflected as the stress changed. The results provide theoretical guidance for horizantal well network modification and re-fracturing optimization design in tight sandstone reservoir.展开更多
基金supported by the National Natural Science Foundation of China(No.52174038)the Science Foundation of China University of Petroleum,Beijing(No.2462018YJRC015)In addition,the support of the Department of Chemical and Petroleum Engineering of University of Calgary and the China Scholarship Council(No.202406440057)is highly appreciated.
文摘Displacement-imbibition coupling production is a pivotal technology for enhancing oil recovery(EOR)in waterflooded tight/shale oil reservoirs.However,the microscopic fluid transport mechanisms across different pore scales remain inadequately understood.This study presents an innovative real-time nuclear magnetic resonance(NMR)experimental system integrated with MRI-based image processing to dynamically monitor oil-water distribution and quantify local oil saturation during injection-shut-in-production.This approach enables quantitative evaluation of pore utilization across different pore size ranges and reveals the impacts of various driving forces on oil displacement efficiency.The results show that displacement-imbibition coupling production employs multiple mechanisms to achieve balanced contributions from pores of all size scales.The displacement-imbibition oil production mainly consists of three stages:displacement-dominated injection,capillary-driven imbibition during shut-in,and displacement-imbibition coupling effects during production.Pressure oscillations significantly enhance matrix-fracture exchange by lowering pore-throat entry thresholds and redistributing pressure fields.Quantitative analysis shows that large pore dominate early displacement,while small pore contribute more during imbibition.Lithology and pore-throat connectivity critically influence displacement efficiency;vitric tuff outperforms argillaceous siltstone by up to 11.8%.Notably,greater fracture complexity increases the oil-water contact area,enhancing capillary imbibition,reducing reliance on displacement forces,and increasing the contribution of displacement-imbibition coupling effects to oil displacement efficiency by 15.35%.Artificially modifying the pressure field to induce pressure oscillations,effectively utilizing the high conductivity of fractures,and fully leveraging the displacement-imbibition coupling effects within matrix pores are crucial for achieving optimal EOR.Lastly,a new concept of nonlinear flow zoning is introduced to describe spatial variations in flow behavior under complex coupling conditions.These experimentally validated insights into matrix-fracture interactions provide theoretical support for designing improved waterflooding strategies and optimizing oil recovery in tight and shale reservoirs.
基金supported by the National Natural Science Foundation of China(Nos.41210005 and 41776081)the National Oil and Gas Major Project of China(No.2011ZX05007-001)the Applied Basic Research Program of Qingdao(No.2016239)
文摘The spatial-temporal relationship between high-quality source rocks and reservoirs is a key factor when evaluating the formation,occurrence,and prospectivity of tight oil and gas reservoirs.In this study,we analyze the fundamental oil and gas accumulation processes occurring in the Songliao Basin,contrasting tight oil sand reservoirs in the south with tight gas sand reservoirs in the north.This is done using geochemical data,constant-rate and conventional mercury injection experiments,and fluid inclusion analyses.Our results demonstrate that as far as fluid mobility is concerned,the expulsion center coincides with the overpressure zone,and its boundary limits the occurrence of tight oil and gas accumulations.In addition,the lower permeability limit of high-quality reservoirs,controlled by pore-throat structures,is 0.1×10^-3μm^2 in the fourth member of the Lower Cretaceous Quantou Formation(K1q^4)in the southern Songliao Basin,and 0.05×10^-3μm^2 in the Lower Cretaceous Shahezi Formation(K1sh)in the northern Songliao Basin.Furthermore,the results indicate that the formation of tight oil and gas reservoirs requires the densification of reservoirs prior to the main phase of hydrocarbon expulsion from the source rocks.Reservoir“sweet spots”develop at the intersection of high-quality source rocks(with high pore pressure)and reservoirs(with high permeability).
基金supported by the National Key Research and Development Program of China[grant numbers 2016YFB0502200,2016YFB0502201]the NSFC[grant number 91638203]。
文摘The indoor positioning system is now an important technique as part of the Internet-of-Things(IoT)ecosystem.Among indoor positioning techniques,multiple Wi-Fi Access Points(APs)-based positioning systems have been researched a lot.There is a lack of research focusing on the scene where only one Wi-Fi AP is available.This work proposes a hybrid indoor positioning system that takes advantage of the Fine-Timing Measurements(FTM)technique that is part of the IEEE 802.11mc standard,introduced back in 2016.The system uses one single Wi-Fi FTM AP and takes advantage of the built-in inertial sensors of the smartphone to estimate the device’s position.We explore both Loosely Coupled(LC)and Tightly Coupled(TC)integration schemes for the sensors’data fusion.Experimental results show that the proposed methods can achieve an average positioning accuracy of about 1 m without knowing the initial position.Compared with the LC integration method,the median error accuracy of the proposed TC fusion algorithm has improved by more than 52%and 67%,respectively,in the two experiments we set up.
基金supported by the China Three Gorges Corporation(No.NBZZ202300860)the National Natural Science Foundation of China(No.52275104)the Science and Technology Innovation Program of Hunan Province(No.2023RC3097).
文摘Deep learning-based wind turbine blade fault diagnosis has been widely applied due to its advantages in end-to-end feature extraction.However,several challenges remain.First,signal noise collected during blade operation masks fault features,severely impairing the fault diagnosis performance of deep learning models.Second,current blade fault diagnosis often relies on single-sensor data,resulting in limited monitoring dimensions and ability to comprehensively capture complex fault states.To address these issues,a multi-sensor fusion-based wind turbine blade fault diagnosis method is proposed.Specifically,a CNN-Transformer Coupled Feature Learning Architecture is constructed to enhance the ability to learn complex features under noisy conditions,while a Weight-Aligned Data Fusion Module is designed to comprehensively and effectively utilize multi-sensor fault information.Experimental results of wind turbine blade fault diagnosis under different noise interferences show that higher accuracy is achieved by the proposed method compared to models with single-source data input,enabling comprehensive and effective fault diagnosis.
基金co-supported by the National Key Research and Development Program of China(No.2016YFC0803103)Beijing Advanced Innovation Center for Future Urban Design(No.UDC2016050100)Beijing Postdoctoral Research Foundation
文摘An Extended Kalman Filter（EKF） is commonly used to fuse raw Global Navigation Satellite System（GNSS） measurements and Inertial Navigation System（INS） derived measurements. However, the Conventional EKF（CEKF） suffers the problem for which the uncertainty of the statistical properties to dynamic and measurement models will degrade the performance.In this research, an Adaptive Interacting Multiple Model（AIMM） filter is developed to enhance performance. The soft-switching property of Interacting Multiple Model（IMM） algorithm allows the adaptation between two levels of process noise, namely lower and upper bounds of the process noise. In particular, the Sage adaptive filtering is applied to adapt the measurement covariance on line. In addition, a classified measurement update strategy is utilized, which updates the pseudorange and Doppler observations sequentially. A field experiment was conducted to validate the proposed algorithm, the pseudorange and Doppler observations from Global Positioning System（GPS） and Bei Dou Navigation Satellite System（BDS） were post-processed in differential mode.The results indicate that decimeter-level positioning accuracy is achievable with AIMM for GPS/INS and GPS/BDS/INS configurations, and the position accuracy is improved by 35.8%, 34.3% and 33.9% for north, east and height components, respectively, compared to the CEKF counterpartfor GPS/BDS/INS. Degraded performance for BDS/INS is obtained due to the lower precision of BDS pseudorange observations.
文摘We develop a new integrated navigation system, which integrates multi-constellations GNSS precise point positioning (PPP), including GPS, GLONASS and Galileo, with low-cost micro-electro-mechanical sensor (MEMS) inertial system, for precise positioning applications. To integrate GNSS and the MEMS-based inertial system, the process and measurement models are developed. Tightly coupled mechanism is adopted, which is carried out in the GNSS raw measurements domain. Both un-differenced and between-satellite single-difference (BSSD) ionosphere-free linear combinations of pseudorange and carrier phase GNSS measurements are processed. Rigorous models are employed to correct GNSS errors and biases. The GNSS inter-system biases are considered as additional unknowns in the integrated error state vector. The developed stochastic model for inertial sensors errors and biases are defined based on first order Gaussian Markov process. Extended Kalman filter is developed to integrate GNSS and inertial measurements and estimate inertial measurements biases and errors. Two field experiments are executed, which represent different real-world scenarios in land-based navigation. The data are processed by using our developed Ryerson PPP GNSS/MEMS software. The results indicate that the proposed integrated system achieves decimeter to centimeter level positioning accuracy when the measurement updates from GNSS are available. During complete GNSS outages the developed integrated system continues to achieve decimeter level accuracy for up to 30 seconds while it achieves meter-level accuracy when a 60-second outage is introduced.
基金Supported by the National Science and Technology Major Project (2017ZX05013-005)。
文摘A mathematical model, fully coupling multiple porous media deformation and fluid flow, was established based on the elastic theory of porous media and fluid-solid coupling mechanism in tight oil reservoirs. The finite element method was used to determine the numerical solution and the accuracy of the model was verified. On this basis, the model was used to simulate productivity of multistage fractured horizontal wells in tight oil reservoirs. The results show that during the production of tight oil wells, the reservoir region close to artificial fractures deteriorated in physical properties significantly, e.g. the aperture and conductivity of artificial fractures dropped by 52.12% and 89.02% respectively. The simulations of 3000-day production of a horizontal well in tight oil reservoir showed that the predicted productivity by the uncoupled model had an error of 38.30% from that by the fully-coupled model. Apparently, ignoring the influence of fluid-solid interaction effect led to serious deviations of the productivity prediction results. The productivity of horizontal well in tight oil reservoir was most sensitive to the start-up pressure gradient, and second most sensitive to the opening of artificial fractures. Enhancing the initial conductivity of artificial fractures was helpful to improve the productivity of tight oil wells. The influence of conductivity, spacing, number and length of artificial fractures should be considered comprehensively in fracturing design. Increasing the number of artificial fractures unilaterally could not achieve the expected increase in production.
文摘The Chang-63 reservoir in the Huaqing area has widely developed tight sandstone ＂thick sand layers, but not reservoirs characterized by rich in oil＂, and it is thus necessary to further study its oil and gas enrichment law. This study builds porosity and fracture development and evolution models in different deposition environments, through core observation, casting thin section, SEM, porosity and permeability analysis, burial history analysis, and ＂four-property-relationships＂ analysis.
文摘A tightly coupled GPS （ global positioning system ）/SINS （ strap down inertial navigation system） based on a GMDH （ group method of data handling） neural network was presented to solve the problem of degraded accuracy for less than four visible GPS satellites with poor signal quality. Positions and velocities of the satellites were predicted by a GMDH neural network, and the pseudo ranges and pseudo range rates received by the GPS receiver were simulated to ensure the regular op eration of the GPS/SINS Kalman filter during outages. In the mathematical simulation a tightly cou pled navigation system with a proposed approach has better navigation accuracy during GPS outages, and the anti jamming ability is strengthened for the tightly coupled navigation system.
基金supported by the National Natural Science Foundation of China under Grant No.62101103.
文摘Against the backdrop of electromagnetic space integration,the radio system of equipment platforms,such as next-generation aircraft,must possess multifunctional integration and electromagnetic stealth performance.Meanwhile,the equipment platforms need to evolve towards flat structures.These requirements pose significant technical challenges for antenna system design.The antenna must possess ultra-wideband to facilitate multi-function integration through the use of continuous radio frequency synthetic aperture.In order to ensure good aerodynamics of the flat airborne platform,it is required to implement conformal design,while the ultra-low profile is the greatest challenge in conformal design.Against this background,this work proposes a novel airborne tightly coupled antenna with ultra-low profile,ultra-wideband,and vertical-polarized omnidirectional radiation.The antenna unit utilizes a long slot structure and implements circular conformal design,where the resistive frequency selection surface is used to expand the operating bandwidth.This antenna has a profile height of only 0.047 times the low-frequency wavelength.Simulation and measurement results show that it achieves an impedance bandwidth of nearly 12∶1 with omnidirectional beam coverage,which meets the requirements of multifunctional future airborne antennas.
文摘Two types of tightly coupled Selective Catalytic Reduction(SCR)mixers were designed in this study,namely Mixer 1 integrated with an SCR catalyst and Mixer 2 arranged separately.Computational Fluid Dynamics(CFD)software was utilized to model the gas flow,spraying,and pyrolysis reaction of the aqueous urea solution in the tightly coupled SCR system.The parameters of gas flow velocity uniformity and ammonia distribution uniformity were simulated and calculated for both Mixer 1 and Mixer 2 in the tightly coupled SCR system to compare their advantages and disadvantages.The simulation results indicated that Mixer 1 exhibited a gas velocity uniformity of 0.972 and an ammonia distribution uniformity of 0.817,whereas Mixer 2 demonstrated a gas velocity uniformity of 0.988 and an ammonia distribution uniformity of 0.964.Mixer 2 performed better in the simulation analysis.Furthermore,a 3D-printed prototype of Mixer 2 was manufactured and installed on an engine test bench to investigate ammonia distribution uniformity and NOX conversion efficiency.The experimental investigations yielded the following findings:1)The ammonia distribution uniformity of Mixer 2 was measured as 0.976,which closely aligned with the simulation result of 0.964,with a deviation of 1.2%from the model calculations;2)As exhaust temperature increased,the ammonia distribution uniformity gradually improved,while an increase in exhaust flow rate resulted in a decrease in ammonia distribution uniformity;3)When utilizing Mixer 2,the NOX conversion efficiency reached 84.7%at an exhaust temperature of 200°C and 97.4%at 250°C.Within the exhaust temperature range of 300°C to 450°C,the NOX conversion efficiency remained above 98%.This study proposed two innovative mixer structures,conducted simulation analysis,and performed performance testing.The research outcomes indicated that the separately arranged Mixer 2 exhibited superior performance.The tightly coupled SCR systemequippedwith Mixer 2 achieved excellent levels of gas velocity uniformity,ammonia distribution uniformity,and NOX conversion efficiency.These findings can serve as valuable references for the design and development of ultra-low emission after-treatment systems for diesel engines in the field of diesel engine aftertreatment.
基金supported by the National Natural Science Foundation of China(Grant Nos.42472195 and 42272153)the Research Fund of PetroChina Tarim Oilfield Company(Grant No.671023060003)Technology Projects of China National Petroleum Corporation(Grant No.2023ZZ16YJ02).
文摘The seepage characteristics of shale reservoirs are influenced not only by multi-field coupling effects such as stress field,temperature field,and seepage field but also exhibit evident creep characteristics during oil and gas exploitation.The complex fluid flow in such reservoirs is analyzed using a combination of theoretical modeling and numerical simulation.This study develops a comprehensive mathematical model that integrates the impact of creep on the seepage process,with consideration of factors including stress,strain,and time-dependent deformation.The model is validated through a series of numerical experiments,which demonstrate the significant influence of creep on the seepage behavior.The results indicate that the rock mechanical parameters and creep constitutive model were determined through triaxial compression tests and uniaxial creep tests.A creep-seepage coupling control equation for shale was established based on the Burgers creep model.The absolute value of the volumetric strain of shale increases rapidly in the initial creep stage,and the increase in vertical stress accelerates the rock’s creep deformation.During the deceleration creep stage,the volumetric strain of the reservoir increases rapidly,leading to a significant decrease in permeability.In the stable creep stage,the pores and fractures in the rock are further compressed,causing a gradual reduction in permeability,which eventually stabilizes.
文摘针对现代化鹅养殖场景中饲料投喂移动小车受动态鹅群干扰,致使同时定位与地图构建(Simultaneous Localization And Mapping,SLAM)算法的定位精度、建图质量下降的问题,提出基于多传感融合目标检测的动态SLAM算法。该算法以LIO-SAM框架为基础,融合激光雷达与惯性测量单元搭建SLAM系统,采用前后端架构优化定位与建图性能;运用匈牙利算法实时追踪鹅群运动状态,结合多传感融合目标检测算法,精准识别并剔除动态鹅群产生的特征点,有效降低定位与建图误差。经KITTI、UrbanNav等公共数据集与实际养殖场景数据测试,在KITTI07序列中,较LeGO-LOAM、LIO-SAM和LVI-SAM等经典算法,均方根误差(RMSE)降低33.18%;在实际鹅养殖环境中,可以快速滤除动态鹅群干扰,提升建图质量与导航可靠性。本研究为智能化鹅养殖饲料投喂提供了新的技术方案,推动了畜牧业自动化发展。
基金Supported by the National Natural Science Foundation of China(51874253)Key Project of Joint Fund of the National Natural Science Foundation and Sichuan Province(U20A20265)。
文摘To investigate the 4D stress change during injection and production in tight sandstone reservoirs, a multi-physical fields modeling method is proposed considering the reservoir heterogeneity, hydraulic fracture and complex injection-production system. The 4D stress evolution of tight sandstone reservoir in Yuan 284 block of Huaqing oilfield, Ordos Basin,during injection-production in horizontal well network is investigated by modeling coupled flow and geomechanics. Results show:(1) Induced by injection and production, the 3D stress increases near the injectors but decreases near the producers, and the horizontal stresses are distributed in obvious strips along their respective stress directions.(2) The horizontal stress difference is the highest at the horizontal wellbore beside injectors during injection and production, while it is the lowest in undeveloped zone between the injectors, and the orientation of maximum horizontal principal stress changes the most near the injectors, which is distributed radially.(3) The hydraulic fracture in re-fracturing well was observed to be asymmetrical in geometry and deflected as the stress changed. The results provide theoretical guidance for horizantal well network modification and re-fracturing optimization design in tight sandstone reservoir.
