Most sedimentary formations with fine layers can be characterized as transversely isotropic media.The evaluation of shear-wave anisotropy is critical in logging-while-drilling(LWD)applications.We developed a joint met...Most sedimentary formations with fine layers can be characterized as transversely isotropic media.The evaluation of shear-wave anisotropy is critical in logging-while-drilling(LWD)applications.We developed a joint method to simultaneously invert formation shear-wave anisotropy and vertical shear velocity using LWD monopole and dipole dispersion data.Theoretical analysis demonstrates that formation shear-wave anisotropy significantly aff ects the dispersion characteristics of Stoneley and formation flexural waves.The inversion objective function was constructed based on the change in dispersion characteristics and was weighted by the spectra of multipole waves.Numerical results using synthetic examples demonstrate that the joint inversion method can not only alleviate the non-uniqueness problem but also help improve the accuracy of the inversion results.The comparison of diff erent signal-to-noise ratio inversion results proved that the weighted inversion method is more accurate and stable.展开更多
Surface and borehole gravity data contain complementary information.Thus,the joint inversion of these two data types can help retrieve the real spatial distributions of density bodies.When a sharp boundary exists betw...Surface and borehole gravity data contain complementary information.Thus,the joint inversion of these two data types can help retrieve the real spatial distributions of density bodies.When a sharp boundary exists between an anomalous density body and its surrounding rock,the interface recovered by smooth inversion with Tikhonov regularization is not clear,leading to difficulties in the subsequent geological interpretation.In this work,we develop a joint inversion of surface and borehole gravity data using zeroth-order minimum entropy regularization.The method takes advantage of the complementary information from surface and borehole gravity data to enhance the imaging resolution of density bodies.It also produces a focused imaging of bodies through the zeroth-order minimum entropy regularization without requiring a preselection of a proper focusing parameter.We apply the developed joint inversion approach to three diff erent synthetic data sets.Inversion results show that the focusing inversion with the zeroth-order minimum entropy regularization provides a good description of the true spatial extent of anomalous density bodies.Meanwhile,the joint focusing inversion reconstructs a more reliable density model with a relatively high resolution when a density body is passed through by one or more boreholes.展开更多
This research investigated the outputting circulation current inhibition characteristic which are controlled by the instantaneous feedback voltage in inverter parallel driving of the mine hoist. We established a trans...This research investigated the outputting circulation current inhibition characteristic which are controlled by the instantaneous feedback voltage in inverter parallel driving of the mine hoist. We established a transfer function of the parallel inverters controlled by the close-loop adjustment of instantaneous voltage feedback. The influence of the parameters of the close-loop feedback circuit to the inhibition effects to the outputting circulation current is observed. After analyzing the circulating current inhibition characteristics, the proportion integration （PI） controller is introduced into the close-loop adjustment by instantaneous voltage feedback. The characteristics equation is gained to determine the PI parameters by drawing the Bode plots. The inhibition effects of the proposed controller are examined by the established simulation model of parallel inverter system. The harmonic distortion rate at the outputting voltage frequency value of 4, 10, 20, 41 and 50 Hz, are all lower than 2.32 % by the instantaneous outputting voltage feedback.展开更多
Atrazine, one of the most commonly used herbicides in the United States, has been found to contaminate groundwater. Atrazine is an endocrine disrupter in animals, and could possibly have carcinogenic effects in humans...Atrazine, one of the most commonly used herbicides in the United States, has been found to contaminate groundwater. Atrazine is an endocrine disrupter in animals, and could possibly have carcinogenic effects in humans. A study involving farm families in four Kentucky Counties has been designed to assess exposure to atrazine through drinking water by a quick, reliable, and effective assay that could be performed in non-specialized laboratories. Data were obtained on farming practices and pesticide applications; and drinking water samples were collected from each household. Water consumption for the participants showed that 72% of the households consumed municipal water, 24% had private wells, and 4% used spring water as their source of drinking water. The analytical method used was based on Enzyme Linked Immuno Sorbent Assay. The results were obtained using a magnetic-particle-based analysis with spectrophotometric reading and showed presence of atrazine in more than 90% of the samples. Results showed that community drinking water sources had significantly higher atrazine concentrations compared to non-community sources （p-value 〈 0.01）. The results of this study may be used to conduct further exposure assessments for drinking water protection from pesticide contamination.展开更多
基金supported by the National Natural Science Foundation of China (Grant No.12174421)the Hubei Key Laboratory of Advanced Aerospace Propulsion Technology (Grant No.KFJJ2020-02).
文摘Most sedimentary formations with fine layers can be characterized as transversely isotropic media.The evaluation of shear-wave anisotropy is critical in logging-while-drilling(LWD)applications.We developed a joint method to simultaneously invert formation shear-wave anisotropy and vertical shear velocity using LWD monopole and dipole dispersion data.Theoretical analysis demonstrates that formation shear-wave anisotropy significantly aff ects the dispersion characteristics of Stoneley and formation flexural waves.The inversion objective function was constructed based on the change in dispersion characteristics and was weighted by the spectra of multipole waves.Numerical results using synthetic examples demonstrate that the joint inversion method can not only alleviate the non-uniqueness problem but also help improve the accuracy of the inversion results.The comparison of diff erent signal-to-noise ratio inversion results proved that the weighted inversion method is more accurate and stable.
基金financially supported by the National Key Research and Development Program of China(no.2018YFC0603300)the National Natural Science Foundation of China(no.42004054)。
文摘Surface and borehole gravity data contain complementary information.Thus,the joint inversion of these two data types can help retrieve the real spatial distributions of density bodies.When a sharp boundary exists between an anomalous density body and its surrounding rock,the interface recovered by smooth inversion with Tikhonov regularization is not clear,leading to difficulties in the subsequent geological interpretation.In this work,we develop a joint inversion of surface and borehole gravity data using zeroth-order minimum entropy regularization.The method takes advantage of the complementary information from surface and borehole gravity data to enhance the imaging resolution of density bodies.It also produces a focused imaging of bodies through the zeroth-order minimum entropy regularization without requiring a preselection of a proper focusing parameter.We apply the developed joint inversion approach to three diff erent synthetic data sets.Inversion results show that the focusing inversion with the zeroth-order minimum entropy regularization provides a good description of the true spatial extent of anomalous density bodies.Meanwhile,the joint focusing inversion reconstructs a more reliable density model with a relatively high resolution when a density body is passed through by one or more boreholes.
文摘This research investigated the outputting circulation current inhibition characteristic which are controlled by the instantaneous feedback voltage in inverter parallel driving of the mine hoist. We established a transfer function of the parallel inverters controlled by the close-loop adjustment of instantaneous voltage feedback. The influence of the parameters of the close-loop feedback circuit to the inhibition effects to the outputting circulation current is observed. After analyzing the circulating current inhibition characteristics, the proportion integration （PI） controller is introduced into the close-loop adjustment by instantaneous voltage feedback. The characteristics equation is gained to determine the PI parameters by drawing the Bode plots. The inhibition effects of the proposed controller are examined by the established simulation model of parallel inverter system. The harmonic distortion rate at the outputting voltage frequency value of 4, 10, 20, 41 and 50 Hz, are all lower than 2.32 % by the instantaneous outputting voltage feedback.
文摘Atrazine, one of the most commonly used herbicides in the United States, has been found to contaminate groundwater. Atrazine is an endocrine disrupter in animals, and could possibly have carcinogenic effects in humans. A study involving farm families in four Kentucky Counties has been designed to assess exposure to atrazine through drinking water by a quick, reliable, and effective assay that could be performed in non-specialized laboratories. Data were obtained on farming practices and pesticide applications; and drinking water samples were collected from each household. Water consumption for the participants showed that 72% of the households consumed municipal water, 24% had private wells, and 4% used spring water as their source of drinking water. The analytical method used was based on Enzyme Linked Immuno Sorbent Assay. The results were obtained using a magnetic-particle-based analysis with spectrophotometric reading and showed presence of atrazine in more than 90% of the samples. Results showed that community drinking water sources had significantly higher atrazine concentrations compared to non-community sources （p-value 〈 0.01）. The results of this study may be used to conduct further exposure assessments for drinking water protection from pesticide contamination.
