基于智能状态监测系统的管线压缩机轴位移故障预警分析

基于状态监测系统针对离心压缩机轴位移故障进行故障机理研究,对轴向力理论计算公式和推力轴承性能影响因素进行分析,结合实际生产过程中引起轴位移的故障原因进一步进行统计,分析故障特征并且给出治理措施。最后,结合某天然气长输管线增压站中PCL型离心压缩机,运用CQ6 000智能状态监测系统进行轴位移故障进行案例分析。

Measuring the anisotropies in astrophysical and cosmological gravitational-wave backgrounds with Taiji and LISA networks

We investigate the capabilities of space-based gravitational-wave detector networks,specifically Taiji and LISA,to measure the anisotropies in stochastic gravitational-wave background(SGWB),which are characterized by the angular power spectrum.We find that a detector network can improve the measurement precision of anisotropies by at most fourteen orders of magnitude,depending on the angular multipoles.By doing so,we can enhance our understanding of the physical origins of SGWB,both in astrophysical and cosmological contexts.We assess the prospects of the detector networks for measuring the parameters of angular power spectrum.We further find an inevitable effect of cosmic variance,which can be suppressed by a better angular resolution,strengthening the importance of configuring detector networks.Our findings also suggest a potential detection of the kinematic dipole due to Doppler boosting of SGWB.

Propagation effect of gravitational wave on detector response

Dear Editors,The detection of gravitational waves（GW）in the event GW150914 by the two advanced detectors of the Laser Interferometer Gravitational-wave Observatory（LIGO）[1]opens a new era for the direct detection of GW[2],searching black hole coalescence[3]and‘heavy’black holes with more than25 solar mass[4],test of general relativity[5],understanding the astrophysical environment of black hole formation[6],etc.In one words,

The prospects of using gravitational waves for constraining the anisotropy of the Universe

The observation of GW150914 gave a new independent measurement of the luminosity distance of a gravitational wave event. In this paper, we constrain the anisotropy of the Universe by using gravitational wave events.We simulate hundreds of events of binary neutron star merger that may be observed by the Einstein Telescope. Full simulation of the production process of gravitational wave data is employed. We find that 200 binary neutron star merging events with the redshift in (0,1) observed by the Einstein Telescope may constrain the anisotropy with an accuracy comparable to that from the Union2.1 supernovae. This result shows that gravitational waves can be a powerful tool for investigating cosmological anisotropy.

Retrofitting low-performance units to abate sewer overflow pollution based on mathematical model and Sobol algorithm

Optimal retrofit of low-performance units(LPUs)is promising to abate overflow pollutant mass loading of sewer systems during wet-weathers.This study presents a combination of mathematical model and Sobol algorithm to help identify LPUs of sewer systems and design retrofitting strategies.Therefore,the solution to minimize the overflow pollutant mass loading from sewers systems can be efficiently obtained.The developed method was demonstrated at a catchment served by one wastewater treatment plant in the Chaohu City,Anhui Province of China,with five pumping stations and a total sewer length of 58.3 km.Within the catchment,there are three rivers and a small lake to receive overflows from the sewer system.Among them,one river that was mostly polluted was selected as the object of overflow pollution abatement during wet weather period.After identifying the LPUs of the sewer system and developing retrofitting strategies using Sobol sequence,the mitigation of overflow pollution during wet weather period was analyzed.Results show that the mass loading of chemical oxygen demand(COD)discharged into the target river could be reduced by 40.6%,by implementing optimal retrofit strategy of LPUs,i.e.,increasing the conveyance capacities of two pumping stations by 2.5–3.2 times and augmenting the diameters of 12 sewers by 1.25–1.29 times.To further coordinate the abatement of overflow pollution and retrofit investment,Sobol sensitivity analysis was conducted to screen the dominant LPUs to update the optimal retrofit strategy.By applying the updated strategy,the overflow COD mass loading per overflow event was close to that of non-updated strategy,while the retrofitting length of sewers was reduced by 40%.Therefore,on the basis of the presented method,decision-makers can flexibly develop retrofitting strategies of sewer system to abate overflow pollution during wet weathers in a cost-effective way.

Searching for a possible dipole anisotropy in acceleration scale with 147 rotationally supported galaxies

We report a possible dipole anisotropy in acceleration scale g↑ with 147 rotationally supported galaxies in the local Universe. It is found that a monopole and dipole correction for the radial acceleration relation can better describe the SPARC data set. The monopole term is negligible but the dipole magnitude is significant. It is also found that the dipole correction is mostly induced by anisotropy in the acceleration scale. The magnitude of the g↑-dipole reaches 0.25±0.04, and its direction is aligned to （l,b）=（171.30°±7.18°,-15.41°±4.87°）, which is very close to the maximum anisotropy direction from the hemisphere comparison method. Furthermore, a robust check shows that the dipole anisotropy could not be reproduced by an isotropic mock data set. However, it is still premature to claim that the Universe is anisotropic, due to the small data samples and uncertainty in the current observations.

Stochastic gravitational wave background due to gravitational wave memory

Gravitational wave memory is an important prediction of general relativity, which has not been detected yet. Amounts of memory events can form a stochastic gravitational wave memory background. Here we find that memory background can be described as a Brownian motion in the condition that the observation time is longer than the averaged time interval between two successive memory events. We investigate, for the first time, the memory background of binary black hole coalescences. We only consider the spectrum of the memory background for a relatively low frequency range. So we can use the step function to approximate the waveform for each memory event. Then we find that the spectrum is a power law with index –2. And the amplitude of the power law spectrum depends on and only on the merger rate of the binary black holes. Consequently, the memory background not only provides a brand new means to detect gravitational wave memory but also opens a new window to explore the event rate of binary black hole mergers and the gravity theory. Space-based detectors are ideal to detect the gravitational wave memory background which corresponds to supermassive binary black holes. Since gravitational wave memory is only sensitive to the merger stage of binary black hole coalescence, the memory background will be an ideal probe of the famous final parsec problem.

Unraveling the early universe’s equation of state and primordial black hole production with PTA,BBN,and CMB observations

Pulsar timing array(PTA)data releases show strong evidence for a stochastic gravitational-wave background in the nanohertz band.When the signal is interpreted by a scenario of scalar-induced gravitational waves(SIGWs),we encounter overproduction of primordial black holes(PBHs).We wonder if varying the equation of state(EoS)of the early Universe can resolve this issue and thereby lead to a consistent interpretation of the PTA data.Analyzing a data combination of PTA,big-bang nucleosynthesis,and cosmic microwave background,we find that an epoch with EoS w~O(10^(-2))between the end of inflation and the onset of radiation domination can significantly suppress the production of PBHs,leading to alleviation of the PBH-overproduction issue.With the inferred interval w=0.44_(-0.40)^(+0.52)at 95%confidence level,our scenario can interpret the PTA data just as well as the conventional scenario of SIGWs produced during the radiation domination.