With the 2008 Ms6.1 Panzhihua earthquake as a case study, we demonstrate that the focal depth of the main shock can be well constrained with two approaches： （1） using the depth phase sPL and （2） using full wavefo...With the 2008 Ms6.1 Panzhihua earthquake as a case study, we demonstrate that the focal depth of the main shock can be well constrained with two approaches： （1） using the depth phase sPL and （2） using full waveform inversion of local and teleseismic data. We also show that focal depths can be well constrained using the depth phase sPL with single broadband seismic station. Our study indicates that the main shock is located at a depth of ii kin, much shallower than those from other studies, confirming that the earthquake occurs in upper crust. Aftershocks are located in the depth range of 11 16 kin, which is consistent with a ruptured near vertical fault whose width is about 10 km, as expected for an Ms6.1 earthquake.展开更多
间接飞行时间(indirect time of flight,iTOF)相机在三维环境感知领域有着广泛的应用前景。根据iTOF相机成像原理,当曝光时间过大导致相机工作在非线性区时,解算的深度信息也会引入额外的偏差,从而影响测量准确度。为了进一步提高飞行...间接飞行时间(indirect time of flight,iTOF)相机在三维环境感知领域有着广泛的应用前景。根据iTOF相机成像原理,当曝光时间过大导致相机工作在非线性区时,解算的深度信息也会引入额外的偏差,从而影响测量准确度。为了进一步提高飞行时间相机的应用精度,根据飞行时间相机的光学成像机理,提出一种针对飞行时间相机的性能参数测量方法,通过实验和计算间接得到飞行时间深度相机的系统增益等性能参数,将其代入飞行时间相机的光学成像模型,即可得到距离与相机输出灰度值的对应曲线。建模与实验结果的相对误差可以达到20%以内,平均相对误差为0.16%。这些性能参数和仿真模型用于指导iTOF相机在不同场景使用时的积分时间选择,可以有效解决因使用不当引入非线性误差而降低距离测量精度的问题。展开更多
In the context of the global“Carbon Peaking and Carbon Neutrality”initiative,the injection of carbon dioxide(CO_(2))into depleted gas reservoirs represents a dual-purpose strategy—facilitating long-term carbon sequ...In the context of the global“Carbon Peaking and Carbon Neutrality”initiative,the injection of carbon dioxide(CO_(2))into depleted gas reservoirs represents a dual-purpose strategy—facilitating long-term carbon sequestration while enhancing hydrocarbon recovery.However,variations in injection parameters at the wellhead can exert pronounced effects on the temperature and pressure conditions at the bottomof the well.These variations,in turn,influence the geomechanical behavior of reservoir rocks and the displacement efficiency of CO_(2) within the formation.Precise prediction of downhole thermodynamic conditions is therefore essential for optimizing injection performance and ensuring reservoir stability.To address this need,the present study develops a robust coupled model to simulate the behavior of CO_(2) within the wellbore,incorporating momentum conservation,mass continuity,and steady-state heat transfer equations.Validation against field-measured data confirms the model’s reliability and applicability under realworld operating conditions.Parametric analysis reveals the complex influence of injection conditions on bottom-hole states.Injection pressure primarily affects downhole pressure,exerting minimal influence on temperature.In contrast,low injection temperatures and elevated flow rates lead to reduced bottom-hole temperatures and heightened pressures.Owing to the interplay of convective and conductive heat transfer mechanisms,the relationship between injection rate and bottom-hole temperature exhibits nonlinearity.Notably,injection scenarios characterized by low temperature,high pressure,and high velocity promote a deeper penetration of the CO_(2) critical phase transition point within the tubing.Among the parameters examined,injection temperature emerges as the dominant factor affecting the depth of CO_(2)’s phase transformation,followed by injection rate,with pressure exerting the least influence.A strong correlation is observed between injection rate and the depth of the critical phase transition,offering a practical framework for tailoring injection strategies to enhance both CO_(2) storage capacity and recovery efficiency.展开更多
Digital structured light （SL） profilometry is increasingly used in three-dimensional （3D） measurement technology. However, the nonlinearity of the off-the-shelf projectors and cameras seriously reduces the measure...Digital structured light （SL） profilometry is increasingly used in three-dimensional （3D） measurement technology. However, the nonlinearity of the off-the-shelf projectors and cameras seriously reduces the measurement accuracy. In this paper, first, we review the nonlinear effects of the projector-camera system in the phase-shifting structured light depth measurement method. We show that high order harmonic wave components lead to phase error in the phase-shifting method. Then a practical method based on frequency domain filtering is proposed for nonlinear error reduction. By using this method, the nonlinear calibration of the SL system is not required. Moreover, both the nonlinear effects of the projector and the camera can be effectively reduced. The simulations and experiments have verified our nonlinear correction method.展开更多
Locating an earthquakes focal depth is always a key project in seismology. Precise focal depth is of critical importance for evaluating seismic hazards, deciphering dynamic mechanisms of earthquake generating,estima...Locating an earthquakes focal depth is always a key project in seismology. Precise focal depth is of critical importance for evaluating seismic hazards, deciphering dynamic mechanisms of earthquake generating,estimating aftershock evolutions and risk,as well as monitoring nuclear tests. However,how we determine an accurate focal depth is always a challenge in seismological studies. Aiming to solve these problems, we analyzed and summarized the present status and the future development of earthquake focal depth locating. In this paper we first reviewed the present status of focal depth locating in the world,and summarized the frequently-used relocating methods and ideas at present,and introduced two types of focal depth relocating ideas: arrival time relocating and waveform modeling methods. For these ideas,we systematically described the S-P and the Pn-Pg methods that belong to arrival time method,and polarization focal depth locating and amplitude focal depth locating that belongs to waveform modeling,and further analyzed the advantages and limitations of these methods. Since the depth phase methods are highly sensitive to focal depth,and are relatively free from the uncertainties of crustal models,we mainly reviewed the depth phases of s Pm P,s PL,s Pn,and s Sn,and quantitatively evaluated their availabilities and characteristics. Second,we also discussed the effects of crustal velocity models on the reliability of focal depth locating,and reviewed the advancements of seismic tomography techniques over recent years. Finally,based on the present status of the progress on the focal depth locating,and studies of seismic velocity structures,we proposed an idea of combining multiple datasets and relocating methods,jointly utilizing seismologic and geodetic techniques to relocate focal depth,which should be the major research field in investigating focal depth and source parameters in the near future.展开更多
基金financial supported by Joint Seismological Science Foundation of China (No.200808078)National Natural Science Foundation of China (Nos.40821160549 and 41074032)
文摘With the 2008 Ms6.1 Panzhihua earthquake as a case study, we demonstrate that the focal depth of the main shock can be well constrained with two approaches： （1） using the depth phase sPL and （2） using full waveform inversion of local and teleseismic data. We also show that focal depths can be well constrained using the depth phase sPL with single broadband seismic station. Our study indicates that the main shock is located at a depth of ii kin, much shallower than those from other studies, confirming that the earthquake occurs in upper crust. Aftershocks are located in the depth range of 11 16 kin, which is consistent with a ruptured near vertical fault whose width is about 10 km, as expected for an Ms6.1 earthquake.
文摘间接飞行时间(indirect time of flight,iTOF)相机在三维环境感知领域有着广泛的应用前景。根据iTOF相机成像原理,当曝光时间过大导致相机工作在非线性区时,解算的深度信息也会引入额外的偏差,从而影响测量准确度。为了进一步提高飞行时间相机的应用精度,根据飞行时间相机的光学成像机理,提出一种针对飞行时间相机的性能参数测量方法,通过实验和计算间接得到飞行时间深度相机的系统增益等性能参数,将其代入飞行时间相机的光学成像模型,即可得到距离与相机输出灰度值的对应曲线。建模与实验结果的相对误差可以达到20%以内,平均相对误差为0.16%。这些性能参数和仿真模型用于指导iTOF相机在不同场景使用时的积分时间选择,可以有效解决因使用不当引入非线性误差而降低距离测量精度的问题。
基金supported by the National Natural Science Foundation of China(Nos.52304046,52204051,52174033 and U23B20156).
文摘In the context of the global“Carbon Peaking and Carbon Neutrality”initiative,the injection of carbon dioxide(CO_(2))into depleted gas reservoirs represents a dual-purpose strategy—facilitating long-term carbon sequestration while enhancing hydrocarbon recovery.However,variations in injection parameters at the wellhead can exert pronounced effects on the temperature and pressure conditions at the bottomof the well.These variations,in turn,influence the geomechanical behavior of reservoir rocks and the displacement efficiency of CO_(2) within the formation.Precise prediction of downhole thermodynamic conditions is therefore essential for optimizing injection performance and ensuring reservoir stability.To address this need,the present study develops a robust coupled model to simulate the behavior of CO_(2) within the wellbore,incorporating momentum conservation,mass continuity,and steady-state heat transfer equations.Validation against field-measured data confirms the model’s reliability and applicability under realworld operating conditions.Parametric analysis reveals the complex influence of injection conditions on bottom-hole states.Injection pressure primarily affects downhole pressure,exerting minimal influence on temperature.In contrast,low injection temperatures and elevated flow rates lead to reduced bottom-hole temperatures and heightened pressures.Owing to the interplay of convective and conductive heat transfer mechanisms,the relationship between injection rate and bottom-hole temperature exhibits nonlinearity.Notably,injection scenarios characterized by low temperature,high pressure,and high velocity promote a deeper penetration of the CO_(2) critical phase transition point within the tubing.Among the parameters examined,injection temperature emerges as the dominant factor affecting the depth of CO_(2)’s phase transformation,followed by injection rate,with pressure exerting the least influence.A strong correlation is observed between injection rate and the depth of the critical phase transition,offering a practical framework for tailoring injection strategies to enhance both CO_(2) storage capacity and recovery efficiency.
基金Project supported by the Science and Technology Major Projects of Zhejiang Province,China(Grant No.2013C03043-5)
文摘Digital structured light （SL） profilometry is increasingly used in three-dimensional （3D） measurement technology. However, the nonlinearity of the off-the-shelf projectors and cameras seriously reduces the measurement accuracy. In this paper, first, we review the nonlinear effects of the projector-camera system in the phase-shifting structured light depth measurement method. We show that high order harmonic wave components lead to phase error in the phase-shifting method. Then a practical method based on frequency domain filtering is proposed for nonlinear error reduction. By using this method, the nonlinear calibration of the SL system is not required. Moreover, both the nonlinear effects of the projector and the camera can be effectively reduced. The simulations and experiments have verified our nonlinear correction method.
基金supported by a grant from the National Earthquake Predicting Field in Sichuan and Yunnan(No.2016CESE0204).
文摘Locating an earthquakes focal depth is always a key project in seismology. Precise focal depth is of critical importance for evaluating seismic hazards, deciphering dynamic mechanisms of earthquake generating,estimating aftershock evolutions and risk,as well as monitoring nuclear tests. However,how we determine an accurate focal depth is always a challenge in seismological studies. Aiming to solve these problems, we analyzed and summarized the present status and the future development of earthquake focal depth locating. In this paper we first reviewed the present status of focal depth locating in the world,and summarized the frequently-used relocating methods and ideas at present,and introduced two types of focal depth relocating ideas: arrival time relocating and waveform modeling methods. For these ideas,we systematically described the S-P and the Pn-Pg methods that belong to arrival time method,and polarization focal depth locating and amplitude focal depth locating that belongs to waveform modeling,and further analyzed the advantages and limitations of these methods. Since the depth phase methods are highly sensitive to focal depth,and are relatively free from the uncertainties of crustal models,we mainly reviewed the depth phases of s Pm P,s PL,s Pn,and s Sn,and quantitatively evaluated their availabilities and characteristics. Second,we also discussed the effects of crustal velocity models on the reliability of focal depth locating,and reviewed the advancements of seismic tomography techniques over recent years. Finally,based on the present status of the progress on the focal depth locating,and studies of seismic velocity structures,we proposed an idea of combining multiple datasets and relocating methods,jointly utilizing seismologic and geodetic techniques to relocate focal depth,which should be the major research field in investigating focal depth and source parameters in the near future.
