This work presents the “Second-Order Comprehensive Adjoint Sensitivity Analysis Methodology (2<sup>nd</sup>-CASAM)” for the efficient and exact computation of 1<sup>st</sup>- and 2<sup>...This work presents the “Second-Order Comprehensive Adjoint Sensitivity Analysis Methodology (2<sup>nd</sup>-CASAM)” for the efficient and exact computation of 1<sup>st</sup>- and 2<sup>nd</sup>-order response sensitivities to uncertain parameters and domain boundaries of linear systems. The model’s response (<em>i.e.</em>, model result of interest) is a generic nonlinear function of the model’s forward and adjoint state functions, and also depends on the imprecisely known boundaries and model parameters. In the practically important particular case when the response is a scalar-valued functional of the forward and adjoint state functions characterizing a model comprising N parameters, the 2<sup>nd</sup>-CASAM requires a single large-scale computation using the First-Level Adjoint Sensitivity System (1<sup>st</sup>-LASS) for obtaining all of the first-order response sensitivities, and at most N large-scale computations using the Second-Level Adjoint Sensitivity System (2<sup>nd</sup>-LASS) for obtaining exactly all of the second-order response sensitivities. In contradistinction, forward other methods would require (<em>N</em>2/2 + 3 <em>N</em>/2) large-scale computations for obtaining all of the first- and second-order sensitivities. This work also shows that constructing and solving the 2<sup>nd</sup>-LASS requires very little additional effort beyond the construction of the 1<sup>st</sup>-LASS needed for computing the first-order sensitivities. Solving the equations underlying the 1<sup>st</sup>-LASS and 2<sup>nd</sup>-LASS requires the same computational solvers as needed for solving (<em>i.e.</em>, “inverting”) either the forward or the adjoint linear operators underlying the initial model. Therefore, the same computer software and “solvers” used for solving the original system of equations can also be used for solving the 1<sup>st</sup>-LASS and the 2<sup>nd</sup>-LASS. Since neither the 1<sup>st</sup>-LASS nor the 2<sup>nd</sup>-LASS involves any differentials of the operators underlying the展开更多
Based on the acoustic mapping, a prediction model for the ground noise radiated from an in-flight helicopter is established. For the enhancement of calculation efficiency, a high-efficiency second-level acoustic radia...Based on the acoustic mapping, a prediction model for the ground noise radiated from an in-flight helicopter is established. For the enhancement of calculation efficiency, a high-efficiency second-level acoustic radiation model capable of taking the influence of atmosphere absorption on noise into account is first developed by the combination of the point-source idea and the rotor noise radiation characteristics. The comparison between the present model and the direct computation method of noise is done and the high efficiency of the model is validated. Rotor free-wake analysis method and Ffowcs Williams-Hawkings（FW-H） equation are applied to the aerodynamics and noise prediction in the present model. Secondly, a database of noise spheres with the characteristic parameters of advance ratio and tip-path-plane angle is established by the helicopter trim model together with a parametric modeling approach. Furthermore, based on acoustic mapping, a method of rapid simulation for the ground noise radiated from an in-flight helicopter is developed. The noise footprint for AH-1 rotor is then calculated and the influence of some parameters including advance ratio and flight path angle on ground noise is deeply analyzed using the developed model.The results suggest that with the increase of advance ratio and flight path angle, the peak noise levels on the ground first increase and then decrease, in the meantime, the maximum Sound Exposure Level（SEL） noise on the ground shifts toward the advancing side of rotor. Besides, through the analysis of the effects of longitudinal forces on miss-distance and rotor Blade-Vortex Interaction（BVI） noise in descent flight, some meaningful results for reducing the BVI noise on the ground are obtained.展开更多
Action-potential encoded optical second harmonic generation(SHG)has been recently proposedfor use in det ecting the axonal damage in patients with demnyelinat ing diseases.In this study,thecharact erization of signal ...Action-potential encoded optical second harmonic generation(SHG)has been recently proposedfor use in det ecting the axonal damage in patients with demnyelinat ing diseases.In this study,thecharact erization of signal conduction along axons of two different levels of denyelination wasstudied via a modified Hodgkin Huxley model,because some types of demyelinating disease,i.e.primary progressive and secondary progesive multiple scleross,are dificult to be distinguishedby magnetic resonance imaging(MRI),we focused on the diferences in signal conduction between two diferent demyelinated axons,such as the first-level demyelination and the second.level demyelination.The spatio-temporal distribution of action potentials along denyelinatedaxons and conduction properties including the refractory period and frequency encoding in theset wo patterns were investigated.The results showed that denyelination could induce the decreaseboth in the amplitude of action potentials and the ability of frequency coding,Furthermore,t hesignal conduction velocity in the second-level dernyelination was about 21%slower than that inthe first-level demyelination.The refractory period in the second-level demyelination was about32%longer t han the first-level.Thus,detecting the signal conduction in demnyelinat ed axons byaction-potential encoded optical SHG could greatly improve the assessment of demyelinatingdisorders to classify the patients.This technique also offers a potential fast and noninvasiveoptical approach for monitoring membrane potential.展开更多
文摘This work presents the “Second-Order Comprehensive Adjoint Sensitivity Analysis Methodology (2<sup>nd</sup>-CASAM)” for the efficient and exact computation of 1<sup>st</sup>- and 2<sup>nd</sup>-order response sensitivities to uncertain parameters and domain boundaries of linear systems. The model’s response (<em>i.e.</em>, model result of interest) is a generic nonlinear function of the model’s forward and adjoint state functions, and also depends on the imprecisely known boundaries and model parameters. In the practically important particular case when the response is a scalar-valued functional of the forward and adjoint state functions characterizing a model comprising N parameters, the 2<sup>nd</sup>-CASAM requires a single large-scale computation using the First-Level Adjoint Sensitivity System (1<sup>st</sup>-LASS) for obtaining all of the first-order response sensitivities, and at most N large-scale computations using the Second-Level Adjoint Sensitivity System (2<sup>nd</sup>-LASS) for obtaining exactly all of the second-order response sensitivities. In contradistinction, forward other methods would require (<em>N</em>2/2 + 3 <em>N</em>/2) large-scale computations for obtaining all of the first- and second-order sensitivities. This work also shows that constructing and solving the 2<sup>nd</sup>-LASS requires very little additional effort beyond the construction of the 1<sup>st</sup>-LASS needed for computing the first-order sensitivities. Solving the equations underlying the 1<sup>st</sup>-LASS and 2<sup>nd</sup>-LASS requires the same computational solvers as needed for solving (<em>i.e.</em>, “inverting”) either the forward or the adjoint linear operators underlying the initial model. Therefore, the same computer software and “solvers” used for solving the original system of equations can also be used for solving the 1<sup>st</sup>-LASS and the 2<sup>nd</sup>-LASS. Since neither the 1<sup>st</sup>-LASS nor the 2<sup>nd</sup>-LASS involves any differentials of the operators underlying the
基金supported by the Funding of Jiangsu Innovation Program for Graduate Education (No. KYLX16_0390)
文摘Based on the acoustic mapping, a prediction model for the ground noise radiated from an in-flight helicopter is established. For the enhancement of calculation efficiency, a high-efficiency second-level acoustic radiation model capable of taking the influence of atmosphere absorption on noise into account is first developed by the combination of the point-source idea and the rotor noise radiation characteristics. The comparison between the present model and the direct computation method of noise is done and the high efficiency of the model is validated. Rotor free-wake analysis method and Ffowcs Williams-Hawkings（FW-H） equation are applied to the aerodynamics and noise prediction in the present model. Secondly, a database of noise spheres with the characteristic parameters of advance ratio and tip-path-plane angle is established by the helicopter trim model together with a parametric modeling approach. Furthermore, based on acoustic mapping, a method of rapid simulation for the ground noise radiated from an in-flight helicopter is developed. The noise footprint for AH-1 rotor is then calculated and the influence of some parameters including advance ratio and flight path angle on ground noise is deeply analyzed using the developed model.The results suggest that with the increase of advance ratio and flight path angle, the peak noise levels on the ground first increase and then decrease, in the meantime, the maximum Sound Exposure Level（SEL） noise on the ground shifts toward the advancing side of rotor. Besides, through the analysis of the effects of longitudinal forces on miss-distance and rotor Blade-Vortex Interaction（BVI） noise in descent flight, some meaningful results for reducing the BVI noise on the ground are obtained.
基金supported by the National Nature Science Foundation of China under Grant No.61335011Program for Changjiang,Scholars and Innovative Research Team in University under Grant No.IRT1115the Fund from Fujian Normal University under Grant No.2008100218.
文摘Action-potential encoded optical second harmonic generation(SHG)has been recently proposedfor use in det ecting the axonal damage in patients with demnyelinat ing diseases.In this study,thecharact erization of signal conduction along axons of two different levels of denyelination wasstudied via a modified Hodgkin Huxley model,because some types of demyelinating disease,i.e.primary progressive and secondary progesive multiple scleross,are dificult to be distinguishedby magnetic resonance imaging(MRI),we focused on the diferences in signal conduction between two diferent demyelinated axons,such as the first-level demyelination and the second.level demyelination.The spatio-temporal distribution of action potentials along denyelinatedaxons and conduction properties including the refractory period and frequency encoding in theset wo patterns were investigated.The results showed that denyelination could induce the decreaseboth in the amplitude of action potentials and the ability of frequency coding,Furthermore,t hesignal conduction velocity in the second-level dernyelination was about 21%slower than that inthe first-level demyelination.The refractory period in the second-level demyelination was about32%longer t han the first-level.Thus,detecting the signal conduction in demnyelinat ed axons byaction-potential encoded optical SHG could greatly improve the assessment of demyelinatingdisorders to classify the patients.This technique also offers a potential fast and noninvasiveoptical approach for monitoring membrane potential.
