Background The extubation time is critical during the intensive care unit stay in aneurysmal subarachnoid hemorrhage(aSAH)patients.The current conventional parameters for predicting extubation failure(EF)and extubatio...Background The extubation time is critical during the intensive care unit stay in aneurysmal subarachnoid hemorrhage(aSAH)patients.The current conventional parameters for predicting extubation failure(EF)and extubation time may not be suitable for this population.Here,we aimed to identify factors associated with EF in aSAH patients.Methods From a single-center observational study on aSAH patients with computed tomography angiography from 2019 to 2021,patients who received microsurgery were enrolled and divided into two groups according to whether EF occurred.Multivariable logistic regression was conducted to evaluate disease severity,medical history,and extubation time differences between patients with and without EF.Results Of 335 patients included,EF occurred with a rate of 0.14.Delayed cerebral ischemia(67.4%vs.13.5%)and acute hydrocephalus(6.5%vs.1.4%)were frequently observed in patients with EF.Also,patients who develop EF presented higher disability(65.9%vs.17.4%)and mortality(10.9%vs.0.7%)rates.Multivariable analysis demonstrated that age(OR 1.038;95%CI 1.004-1.073;P=0.028),onset to admission time(OR 0.731;95%CI 0.566-0.943;p=0.016),WFNS grade>3(OR 4.309;95%CI 1.639-11.330;p=0.003),and extubation time<24 h(OR 0.097;95%CI 0.024-0.396;p=0.001)were significantly associated with EF occurrence.Conclusions These data provide further evidence that older aSAH patients with onset to admission time<2 days and WFNS grade>3 have a high risk of developing EF,which is amplified by the ultra-early extubation.Moreover,in patients with two or more risk factors,a prolonged intubation recommendation requires consideration to avoid the EF.展开更多
在论文“各向异性介质界面模式转换波Ⅰ:理论分析”给出的VTI-TTI(Transverse Isotropy with a Vertical Axis of Symmetry-Transverse Isotropy with a Tilted Axis of Symmetry)介质界面上产生的模式转换波极化系数的解析表达式和该...在论文“各向异性介质界面模式转换波Ⅰ:理论分析”给出的VTI-TTI(Transverse Isotropy with a Vertical Axis of Symmetry-Transverse Isotropy with a Tilted Axis of Symmetry)介质界面上产生的模式转换波极化系数的解析表达式和该界面反射/折射系数的计算表达式的基础上,选择各向异性页岩-泰勒砂岩界面和各向异性页岩-油质页岩界面作为界面系统,利用MATLAB进行仿真,对各向异性介质界面反射和折射特性、产生的模式转换波的极化状态以及出现的一些物理现象进行了分析和解释。使用改进后的Daley-Hron各向异性介质界面模型,分析了地层各向异性和折射TTI介质倾斜角对界面第一临界角的影响。应用能量守恒定律和声学边界条件验证了推导出的在各向异性地层界面产生的模式转换波极化系数和该界面反射/折射系数的正确性。发现某些各向异性地层界面似乎存在一个对应折射SV(Shear Vertical)波的入射临界角(第二临界角),但是在实际中并不存在的物理现象。展开更多
It is known that rock anisotropy can significantly influence the phase and energy velocities of an elastic wave,as well as its reflection/transmission(R/T)coefficients.As a result,it can distort the velocity analysis ...It is known that rock anisotropy can significantly influence the phase and energy velocities of an elastic wave,as well as its reflection/transmission(R/T)coefficients.As a result,it can distort the velocity analysis of seismic-reflection data.In this work we present a velocity analysis for seismic-reflection data based on the available anisotropic rock parameters.We analyzed the created errors on time-depth relation of the seismic-reflection data in neglecting rock anisotropy and/or neglecting the difference between energy velocity and phase velocity,including the case of wide-angle reflection.The calculated results show that the effect of rock anisotropy on time-depth relation of seismic-reflection data is dependent not only on the values of anisotropic parameters,but also on the space arrangement of both source and receiver-array.For all studied cases(weak,moderate or strong anisotropy),we found that the effect of rock anisotropy on time-depth relation could not be neglected.Nevertheless,for the case of weak anisotropy,the energy velocity may be replaceable by the phase velocity to obtain a very good approximation on time-depth relation.Consequently,the seismic-reflection data processing algorithm for numerical computations can be simplified.展开更多
Based on an acoustic logging transmission network and the engineering pattern of a sliding wave in acoustic logging, analysis and calculations have been performed in a study of the effects of the electric-acoustic and...Based on an acoustic logging transmission network and the engineering pattern of a sliding wave in acoustic logging, analysis and calculations have been performed in a study of the effects of the electric-acoustic and acoustic-electric conversions of the transducers on the acoustic logging signal. The results show that acoustic-electric conversion through the transducer can cause not only a serious disturbance in the signal amplitude, but also an apparent transmission delay. For engineering applications, the amplitude variation and transmission delay must be accounted for in a practical analysis of the acoustic logging signal in rocks. The results also show that with enhanced understanding and proper justification, the error caused by the acoustic-electric conversion can be significantly reduced in evaluation of the cement bond quality of a cased well, and the accuracy of rock porosity calculated using the measured acoustic velocity can be increased.展开更多
Based on the reported physical parameters for hexagonal system solids,we have calculated the effects of anisotropy on polarization of plane P-wave propagation.Herein we report the results of calculations and the newly...Based on the reported physical parameters for hexagonal system solids,we have calculated the effects of anisotropy on polarization of plane P-wave propagation.Herein we report the results of calculations and the newly observed physical phenomena.It is found that,for a given propagation,if the polarization is parallel to the wave vector,so also to the Poynting vector.In such a case,the phase velocity is identical to the energy velocity;the quasi P-wave degenerates to a pure P-wave along the propagation.It is also noted that if the polarization is parallel to the Poynting vector but not to the wave vector,the propagating wave cannot be a pure P-wave.Furthermore,the polarization in a quasi P-wave may deviate from the wave vector for more than 45°,but the deviation from the Poynting vector is always less than 45°.The energy velocity of a quasi SV-wave can be larger than that of the quasi P-wave in some propagation directions,even though the phase velocity of a quasi SV-wave may never be larger than either the phase velocity or energy velocity of the quasi P-wave.Finally,in case of parameters ε=0 and δ*≠0,the polarization of a quasi P-wave has an observed symmetry at a 45°phase angle.The anisotropy of a hexagonal system solid determines if a pure P-wave can be created and what the propagation direction is for a plane wave propagating inside such a hexagonal system solid.展开更多
文摘Background The extubation time is critical during the intensive care unit stay in aneurysmal subarachnoid hemorrhage(aSAH)patients.The current conventional parameters for predicting extubation failure(EF)and extubation time may not be suitable for this population.Here,we aimed to identify factors associated with EF in aSAH patients.Methods From a single-center observational study on aSAH patients with computed tomography angiography from 2019 to 2021,patients who received microsurgery were enrolled and divided into two groups according to whether EF occurred.Multivariable logistic regression was conducted to evaluate disease severity,medical history,and extubation time differences between patients with and without EF.Results Of 335 patients included,EF occurred with a rate of 0.14.Delayed cerebral ischemia(67.4%vs.13.5%)and acute hydrocephalus(6.5%vs.1.4%)were frequently observed in patients with EF.Also,patients who develop EF presented higher disability(65.9%vs.17.4%)and mortality(10.9%vs.0.7%)rates.Multivariable analysis demonstrated that age(OR 1.038;95%CI 1.004-1.073;P=0.028),onset to admission time(OR 0.731;95%CI 0.566-0.943;p=0.016),WFNS grade>3(OR 4.309;95%CI 1.639-11.330;p=0.003),and extubation time<24 h(OR 0.097;95%CI 0.024-0.396;p=0.001)were significantly associated with EF occurrence.Conclusions These data provide further evidence that older aSAH patients with onset to admission time<2 days and WFNS grade>3 have a high risk of developing EF,which is amplified by the ultra-early extubation.Moreover,in patients with two or more risk factors,a prolonged intubation recommendation requires consideration to avoid the EF.
文摘在论文“各向异性介质界面模式转换波Ⅰ:理论分析”给出的VTI-TTI(Transverse Isotropy with a Vertical Axis of Symmetry-Transverse Isotropy with a Tilted Axis of Symmetry)介质界面上产生的模式转换波极化系数的解析表达式和该界面反射/折射系数的计算表达式的基础上,选择各向异性页岩-泰勒砂岩界面和各向异性页岩-油质页岩界面作为界面系统,利用MATLAB进行仿真,对各向异性介质界面反射和折射特性、产生的模式转换波的极化状态以及出现的一些物理现象进行了分析和解释。使用改进后的Daley-Hron各向异性介质界面模型,分析了地层各向异性和折射TTI介质倾斜角对界面第一临界角的影响。应用能量守恒定律和声学边界条件验证了推导出的在各向异性地层界面产生的模式转换波极化系数和该界面反射/折射系数的正确性。发现某些各向异性地层界面似乎存在一个对应折射SV(Shear Vertical)波的入射临界角(第二临界角),但是在实际中并不存在的物理现象。
基金supported by the National Natural Science Foundation of China(40974078)the US Department of Energy(DE-FC2608NT0 005643)+1 种基金the Natural Science Foundation of Shaanxi Province,China (2007D15)North Dakota Industrial Commission with five industrial companies:Encore Acquisition,Hess,Marathon Oil,St.Mary Land & Exploration,and Whiting Petroleum(NDIC-G015-031)
文摘It is known that rock anisotropy can significantly influence the phase and energy velocities of an elastic wave,as well as its reflection/transmission(R/T)coefficients.As a result,it can distort the velocity analysis of seismic-reflection data.In this work we present a velocity analysis for seismic-reflection data based on the available anisotropic rock parameters.We analyzed the created errors on time-depth relation of the seismic-reflection data in neglecting rock anisotropy and/or neglecting the difference between energy velocity and phase velocity,including the case of wide-angle reflection.The calculated results show that the effect of rock anisotropy on time-depth relation of seismic-reflection data is dependent not only on the values of anisotropic parameters,but also on the space arrangement of both source and receiver-array.For all studied cases(weak,moderate or strong anisotropy),we found that the effect of rock anisotropy on time-depth relation could not be neglected.Nevertheless,for the case of weak anisotropy,the energy velocity may be replaceable by the phase velocity to obtain a very good approximation on time-depth relation.Consequently,the seismic-reflection data processing algorithm for numerical computations can be simplified.
基金supported by the National Natural Science Foundation of China (40974078)
文摘Based on an acoustic logging transmission network and the engineering pattern of a sliding wave in acoustic logging, analysis and calculations have been performed in a study of the effects of the electric-acoustic and acoustic-electric conversions of the transducers on the acoustic logging signal. The results show that acoustic-electric conversion through the transducer can cause not only a serious disturbance in the signal amplitude, but also an apparent transmission delay. For engineering applications, the amplitude variation and transmission delay must be accounted for in a practical analysis of the acoustic logging signal in rocks. The results also show that with enhanced understanding and proper justification, the error caused by the acoustic-electric conversion can be significantly reduced in evaluation of the cement bond quality of a cased well, and the accuracy of rock porosity calculated using the measured acoustic velocity can be increased.
基金supported by the National Natural Science Foundation of China(Grant No.40974078)the Physical Sciences Division at University of Chicago
文摘Based on the reported physical parameters for hexagonal system solids,we have calculated the effects of anisotropy on polarization of plane P-wave propagation.Herein we report the results of calculations and the newly observed physical phenomena.It is found that,for a given propagation,if the polarization is parallel to the wave vector,so also to the Poynting vector.In such a case,the phase velocity is identical to the energy velocity;the quasi P-wave degenerates to a pure P-wave along the propagation.It is also noted that if the polarization is parallel to the Poynting vector but not to the wave vector,the propagating wave cannot be a pure P-wave.Furthermore,the polarization in a quasi P-wave may deviate from the wave vector for more than 45°,but the deviation from the Poynting vector is always less than 45°.The energy velocity of a quasi SV-wave can be larger than that of the quasi P-wave in some propagation directions,even though the phase velocity of a quasi SV-wave may never be larger than either the phase velocity or energy velocity of the quasi P-wave.Finally,in case of parameters ε=0 and δ*≠0,the polarization of a quasi P-wave has an observed symmetry at a 45°phase angle.The anisotropy of a hexagonal system solid determines if a pure P-wave can be created and what the propagation direction is for a plane wave propagating inside such a hexagonal system solid.
