Numerical simulation and experimental research of flow-induced noise for centrifugal pumps

The experimental system of exterior performances for centrifugal pumps is built in this paper to verify the reliability of the numerical simulation. Then, the pressure fluctuation inside centrifugal pumps is computed numerically. The computational results indicate that higher peaks of pressure fluctuation are mainly at the rotation frequency, blade frequency and double blade frequency. Comparing the computational results between the coupled and uncoupled boundary element methods, the influence of the coupling on the distribution of sound pressure level cannot be ignored. Finally, the coupling acoustic boundary element method is adopted to compute the sound field of centrifugal pumps, and its result is also verified by experiment. The pressure fluctuation of the volute plays a greater influence on the sound pressure at the outlet of centrifugal pumps. The sound pressure has shown peaks in both the blade frequency and double blade frequency. It thus indicates that interferences between the impeller and tongue are the main reasons for the flow-induced noise of centrifugal pumps

康复专科护士的发展现状与展望

Through access to a lot of relevant information on the role of the rehabilitation nurse specialist functions, explore how rehabilitation specialist nurse qualifications provides a basis for our rehabilitation specialist nurse cultivating and development.本文通过查阅大量相关资料，对康复专科护士的角色、功能等进行综述，探索康复专科护士的资格认证方式为我国康复专科护士的培养及使用提供依据

Analysis of the children's dynamic and static stereopsis of intermittent exotropia

AIM: To compare and analyze the stereopsis of intermittent exotropia children under the different backgrounds of dynamic stimuli and static stimuli.<p>METHODS: We collected 56 children(male 26, female 30 with intermittent exotropia at the age from 5y to 12y and examined their stereopsis under the different backgrounds of dynamic stimuli and static stimuli using a multidimensional sense perception training software. The differences between the dynamic stereopsis and static stereopsis were compared.<p>RESULTS: Totally 17 cases(30%)had both dynamicstereopsis and static stereopsis, 39 cases(70%)had either dynamic or static stereopsis deficit, only 10 cases(26%)had dynamic stereopsis, 25 cases(64%)static stereopsis left and 4 cases(10%)were without any form of stereopsis. The positive rate of dynamic stereopsis was better than the positive rate of static stereopsis, with statistical significance(<i>P</i><0.05).<p>CONCLUSION: Dynamicstereopsis is better than the static stereopsis to intermittent exotropia children

Numerical simulation and experimental research of flow-induced noise for centrifugal pumps

The experimental system of exterior performances for centrifugal pumps is built in this paper to verify the reliability of the numerical simulation. Then, the pressure fluctuation inside centrifugal pumps is computed numerically. The computational results indicate that higher peaks of pressure fluctuation are mainly at the rotation frequency, blade frequency and double blade frequency. Comparing the computational results between the coupled and uncoupled boundary element methods, the influence of the coupling on the distribution of sound pressure level cannot be ignored. Finally, the coupling acoustic boundary element method is adopted to compute the sound field of centrifugal pumps, and its result is also verified by experiment. The pressure fluctuation of the volute plays a greater influence on the sound pressure at the outlet of centrifugal pumps. The sound pressure has shown peaks in both the blade frequency and double blade frequency. It thus indicates that interferences between the impeller and tongue are the main reasons for the flow-induced noise of centrifugal pumps

Numerical simulation and experimental research of flow-induced noise for centrifugal pumps

The experimental system of exterior performances for centrifugal pumps is built in this paper to verify the reliability of the numerical simulation. Then, the pressure fluctuation inside centrifugal pumps is computed numerically. The computational results indicate that higher peaks of pressure fluctuation are mainly at the rotation frequency, blade frequency and double blade frequency. Comparing the computational results between the coupled and uncoupled boundary element methods, the influence of the coupling on the distribution of sound pressure level cannot be ignored. Finally, the coupling acoustic boundary element method is adopted to compute the sound field of centrifugal pumps, and its result is also verified by experiment. The pressure fluctuation of the volute plays a greater influence on the sound pressure at the outlet of centrifugal pumps. The sound pressure has shown peaks in both the blade frequency and double blade frequency. It thus indicates that interferences between the impeller and tongue are the main reasons for the flow-induced noise of centrifugal pumps

Two halosesquiterpenes from Laurencia composita

Two new chamigrane sesquiterpenes, yicterpenes A (1) and B (2) each with an unprecedented halogenation at C-9 and a hemiketal unit at C-10, were isolated from the marine red algaLaurencia composita. The structures and absolute configurations of them were identified by NMR, ECD, and mass spectrometric methods as well as quantum chemical calculations. Compound&nbsp;1&nbsp;with a chlorination at C-9 was more active against some tested marine-derived organisms than&nbsp;2&nbsp;with a bromination at C-9. &nbsp;Two new chamigrane sesquiterpenes, yicterpenes A (1) and B (2) each with an unprecedented halogenation at C-9 and a hemiketal unit at C-10, were isolated from the marine red alga Laurencia composita. The structures and absolute configurations of them were identified by NMR, ECD, and mass spectrometric methods as well as quantum chemical calculations. Compound 1 with a chlorination at C-9 was more active against some tested marine-derived organisms than 2 with a bromination at C-9

(E)-2-[(1-Benzyl­piperidin-4-yl)imino­meth­yl]phenol

There are two mol­ecules in the asymmetric unit of the title compound, C19H22N2O. Both mol­ecules have an E conformation about their C=N bonds and both piperdine rings adopt chair conformations with their N atoms adopting pyramidal geometries [bond angle sums = 329.8 (4) and 330.2 (4)°]. Both mol­ecules feature an intra­molecular O—H⋯N hydrogen bond, which generates an S(6) ring. The dihedral angles between the phenyl and benzene ring planes are 45.97 (18) and 66.0 (2)°. Short O—H⋯O contacts occur in the crystal