Three degrees of freedom (3-DOF) Helmholtz resonator which consists of three cylindrical necks and cavities connected in series (neck-cavity-neck-cavity-neck-cavity) is suitable to reduce flow pulsation in hydraulic s...Three degrees of freedom (3-DOF) Helmholtz resonator which consists of three cylindrical necks and cavities connected in series (neck-cavity-neck-cavity-neck-cavity) is suitable to reduce flow pulsation in hydraulic system. A novel lumped parameter model (LPM) of 3-DOF Helmholtz resonator in hydraulic system is developed which considers the viscous friction loss of hy- draulic fluid in the necks. Applying the Newton's second law of motion to the equivalent mechanical model of the resonator, closed-form expression of transmission loss and resonance frequency is presented. Based on the LPM, an optimal design method which employs rotate vector optimization method (RVOM) is proposed. The purpose of the optimal design is to search the reso- nator's unknown parameters so that its resonance frequencies can coincide with the pump-induced flow pulsation harmonics respectively. The optimal design method is realized to design 3-DOF Helmholtz resonator for a certain type of aviation piston pump hydraulic system. The optimization result shows the feasibility of this method, and the simulation under optimum parame- ters reveals that the LPM can get the same precision as transfer matrix method (TMM).展开更多
Objective:Integrated congenital heart disease(CHD)services were implemented in Beijing in 2022.This study analyzed prenatal diagnosis patterns and neonatal mortality data for duct-dependent CHDs before and after imple...Objective:Integrated congenital heart disease(CHD)services were implemented in Beijing in 2022.This study analyzed prenatal diagnosis patterns and neonatal mortality data for duct-dependent CHDs before and after implementation to provide insights for service optimization.Methods:We conducted a retrospective analysis of 487 cases of duct-dependent CHDs identified through the Beijing Birth Defects Monitoring System from January 2021 to December 2022.The study population included fetuses and infants from 13 weeks gestation to one year after birth.Cases underwent descriptive analysis focusing on disease occurrence,diagnostic timing,and mortality outcomes.Results:The prenatal diagnosis rate for ductdependent CHDs increased from 93.39%in 2021 to 93.91%in 2022,while delayed diagnosis rates decreased from 4.28%to 3.91%.Genetic diagnosis rates improved from 27.92%to 31.94%.Live birth rates following prenatal diagnosis increased substantially from 28.75%to 40.28%.Outcomes varied significantly by CHD subtypes,with complete transposition of the great arteries with intact ventricular septum achieving an 82.14%live birth rate,while hypoplastic left heart syndrome cases resulted in no live births.Notably,neonatal mortality decreased markedly from 7.23%to 3.03%.Conclusions:Beijing’s integrated service model for CHDs has effectively strengthened the connection between secondary and tertiary prevention strategies,reduced unnecessary pregnancy terminations,and improved neonatal survival outcomes.展开更多
基金National Science Fund for Distinguished Young Scholars (50825502)
文摘Three degrees of freedom (3-DOF) Helmholtz resonator which consists of three cylindrical necks and cavities connected in series (neck-cavity-neck-cavity-neck-cavity) is suitable to reduce flow pulsation in hydraulic system. A novel lumped parameter model (LPM) of 3-DOF Helmholtz resonator in hydraulic system is developed which considers the viscous friction loss of hy- draulic fluid in the necks. Applying the Newton's second law of motion to the equivalent mechanical model of the resonator, closed-form expression of transmission loss and resonance frequency is presented. Based on the LPM, an optimal design method which employs rotate vector optimization method (RVOM) is proposed. The purpose of the optimal design is to search the reso- nator's unknown parameters so that its resonance frequencies can coincide with the pump-induced flow pulsation harmonics respectively. The optimal design method is realized to design 3-DOF Helmholtz resonator for a certain type of aviation piston pump hydraulic system. The optimization result shows the feasibility of this method, and the simulation under optimum parame- ters reveals that the LPM can get the same precision as transfer matrix method (TMM).
基金Supported by the National Key Research and Development Program of China(grant number 2018YFC1002304).
文摘Objective:Integrated congenital heart disease(CHD)services were implemented in Beijing in 2022.This study analyzed prenatal diagnosis patterns and neonatal mortality data for duct-dependent CHDs before and after implementation to provide insights for service optimization.Methods:We conducted a retrospective analysis of 487 cases of duct-dependent CHDs identified through the Beijing Birth Defects Monitoring System from January 2021 to December 2022.The study population included fetuses and infants from 13 weeks gestation to one year after birth.Cases underwent descriptive analysis focusing on disease occurrence,diagnostic timing,and mortality outcomes.Results:The prenatal diagnosis rate for ductdependent CHDs increased from 93.39%in 2021 to 93.91%in 2022,while delayed diagnosis rates decreased from 4.28%to 3.91%.Genetic diagnosis rates improved from 27.92%to 31.94%.Live birth rates following prenatal diagnosis increased substantially from 28.75%to 40.28%.Outcomes varied significantly by CHD subtypes,with complete transposition of the great arteries with intact ventricular septum achieving an 82.14%live birth rate,while hypoplastic left heart syndrome cases resulted in no live births.Notably,neonatal mortality decreased markedly from 7.23%to 3.03%.Conclusions:Beijing’s integrated service model for CHDs has effectively strengthened the connection between secondary and tertiary prevention strategies,reduced unnecessary pregnancy terminations,and improved neonatal survival outcomes.
