Analysis of the Influence of Different Bionic Structures on the Noise Reduction Performance of the Centrifugal Pump.

The strong noise generated during the operation of the centrifugal pump harms the pump group and people. In order to decrease the noise of the centrifugal pump, a specific speed of 117.3 of the centrifugal pump is chosen as a research object. The bionic modification of centrifugal pump blades is carried out to explore the influence of different bionic structures on the noise reduction performance of centrifugal pumps. The internal flow field and internal sound field of bionic blades are studied by numerical calculation and test methods. The test is carried out on a closed pump test platform which includes external characteristics and a flow noise test system. The effects of two different bionic structures on the external characteristics, acoustic amplitude-frequency characteristics and flow field structure of a centrifugal pump, are analyzed. The results show that the pit structure has little influence on the external characteristic parameters, while the sawtooth structure has a relatively great influence. The noise reduction effect of the pit structure is aimed at the wide-band noise, while the sawtooth structure is aimed at the discrete noise of the blade-passing frequency (BPF) and its frequency doubling. The noise reduction ability of the sawtooth structure is not suitable for high-frequency bands.

Multicondition Optimization and Experimental Measurements of a Double-Blade Centrifugal Pump Impeller.

In order to improve internal unsteady flow in a double-blade centrifugal pump (DBCP), this study used major geometric parameters of the original design as the initial values, heads at three conditions (i.e., 80% design flow rate, 100% design flow rate, and 120% design flow rate) as the constraints conditions, and the maximum of weighted average efficiency at the three conditions as the objective function. An adaptive simulated annealing algorithm was selected to solve the energy performance calculation model and the supertransitive approximation method was applied to fix optimal weight factors of individual objectives. On the basis of hydraulic performance optimization, three-condition automatic computational fluid dynamics (CFD) optimization of impeller meridional plane for the DBCP was realized by means of Isight software integrated Pro/E, Gambit, and Fluent software. The shroud arc radii R0 and R1, shroud angle T1, hub arc radius R2, and hub angle T2 on the meridional plane were selected as the design variables and the maximum of weighted average hydraulic efficiency at the three conditions was chosen as the objective function. Performance characteristic test and particle image velocimetry (PIV) measurements of internal flow in the DBCP were conducted. Performance characteristic test results show that the weighted average efficiency of the impeller after the three-condition optimization has increased by 1.46% than that of original design. PIV measurements results show that vortex or recirculation phenomena in the impeller are distinctly improved under the three conditions.

Noise spectrum characteristics of marine pump units induced by different excitation sources.

To study the noise spectrum characteristics of marine pump units induced by different excitation sources, a computational aeroacoustic (CAA) model of the internal and external field noise of a marine pump was established. The coupled acoustic-vibration method was used to obtain the spectrum characteristics of internal and external field noise. The accuracy and feasibility of the simulation method for noise prediction were confirmed through a noise test. Due to the different mediums in the internal and external fields of the marine pump, an external field acoustic model was established based on the automatically matched layer (AML) technology. The spectral characteristics of different excitation sources and the spatial distribution of the radiated sound field were analyzed, and the contribution of different sound source excitations to the internal and external sound field was revealed. The results show that the main frequency of the internal field noise generated by different excitations is at the blade passing frequency, and the internal field noise induced by the dipole acoustic excitations dominates at 180.6 dB. For the external field noise, the main frequency is still located at the blade passing frequency. The radiation noise induced by the fluid excitation (139.2 dB) is higher than that induced by the dipole excitations (surface dipole, 136.3 dB; rotating dipole, 137.3 dB).

The Length and Distribution of Plasma Cell-Free DNA Fragments in Stroke Patients.

A number of studies have shown that plasma cell-free DNA is closely related to the risk of stroke, but the fragmentation status of plasma cell-free DNA and its clinical application value in ischemic stroke are still unclear. In this study, 48 patients with new ischemic stroke and 20 healthy subjects were enrolled. The second-generation high-throughput sequencing technique was used to study the plasma cell-free fragment length and regional distribution of the subjects. As noted in our results, the ratio of plasma cell-free DNA fragments in the disease group was significantly greater than that of the healthy group in the 300-400 bp range; conversely for fragments at the 75-250 bp range, the ratio of plasma cell-free DNA fragments in the patient group was apparently lower than that of the healthy group. In-depth analysis of the proportion of fragments distributed on each component of the genome was carried out. Our results recorded that the plasma cell-free DNA fragments in the disease group were inclined to the EXON, CpG islands, and ALU regions in contrast to that of the healthy group. In particular, fragments within the 300-400 bp range of the disease group were enrichment in the regions of EXON, INTRON, INTERGENIC, LINE, Fragile, ALU, and CpG islands. In summary, our findings suggested that the intracellular DNA degradation profiles could be applied to distinguish the stroke group and the healthy group, which provided a theoretical basis for the clinical diagnosis and prognosis of stroke by profiling the characteristic of plasma cell-free DNA fragments.

Time-Series Expression Analysis of Epidermal Stem Cells from High Fat Diet Mice.

We aimed to identify differentially expressed genes (DEGs) in epidermal stem cells (epiSCs) in response to high fat diet (HFD). DEGs were identified by time-series analysis of the gene expression profile (GSE84510) in Gene Expression Omnibus (GEO) database. Functions and pathways affected by HFD were identified by functional annotation of DEGs. Key factors responding to HFD was identified by protein-protein interaction (PPI) network analysis. Two groups of genes with the same tendency in response to HFD were identified. ECM-related processes and PI3K pathway were altered in the early stage of obesity. A PPI network was constructed to delineate the interactions among proteins encoded by DEGs and ICAM1 and RELA were key epiSC factors respond to HFD. Our studies may provide valuable insights into the molecular mechanisms underlying how obesity affects the functions of epiSC.

Correlation of ascending aorta elasticity and the severity of coronary artery stenosis in hypertensive patients with coronary heart disease assessed by M-mode and tissue Doppler echocardiography.

The main objective of this study is to investigate the relationship between ascending aorta elasticity and the severity of coronary artery stenosis in essential hypertensive patients with coronary heart disease (CHD) using M-mode and tissue Doppler echocardiography. A total of 184 hypertensive patients with CHD were enrolled. Patients were divided into three groups based on the severity of coronary stenosis measured by coronary arteriography (CAG): slight stenosis (group 1), moderate stenosis (group 2) and serious stenosis (group 3). M-mode and tissue Doppler echocardiography were performed, and elasticity indexes of ascending aorta including stiffness index, distensibility index, and S wave speed of anterior wall were calculated and correlated with the severity of coronary stenosis. Ascending aorta stiffness index was increased, whereas distensibility index and S wave speed of anterior wall were decreased in moderate and severe stenosis groups compared with slight stenosis group (P < 0.01). Elasticity indexes change in a stepwise pattern with the narrowness of coronary artery, and there was a significant correlation between aortic elasticity and severity of coronary artery by Pearson correlation analysis (P < 0.01). Elasticity indexes of ascending aorta correlate well with severity of coronary stenosis. Elasticity indexes of ascending aorta can serve as predictors for coronary arterial lesion in hypertensive patients.