Monitoring Oil Levels Of Journal Bearings Based On The Analysis Of Vibration Signals

This paper presents a study of monitoring the oil starvation of a journal bearing based on vibration analysis. A diagnostic model is established by includ-ing asperity ploughs and collisions. These excitations are more significant as the oil level is reduced due to less oil film effect. However, it has been found by modulation signal bispectrum analysis that the instable oil whirls can affect the measured responses in the middle frequency range (3.5kHz to 5.5kHz), leading to a good detection of the instability but an inconsistent diagnosis. However, the structural resonances in the high frequency range (5.5kHz to 11kHz) can better reflect the excitations and result in a more agreeable separation of different levels under wide operating conditions

PSR J1926-0652: A Pulsar with Interesting Emission Properties Discovered at FAST

We describe PSR J1926-0652, a pulsar recently discovered with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Using sensitive single-pulse detections from FAST and long-term timing observations from the Parkes 64-m radio telescope, we probed phenomena on both long and short time scales. The FAST observations covered a wide frequency range from 270 to 800 MHz, enabling individual pulses to be studied in detail. The pulsar exhibits at least four profile components, short-term nulling lasting from 4 to 450 pulses, complex subpulse drifting behaviours and intermittency on scales of tens of minutes. While the average band spacing P3 is relatively constant across different bursts and components, significant variations in the separation of adjacent bands are seen, especially near the beginning and end of a burst. Band shapes and slopes are quite variable, especially for the trailing components and for the shorter bursts. We show that for each burst the last detectable pulse prior to emission ceasing has different properties compared to other pulses. These complexities pose challenges for the classic carousel-type models.Comment: 13pages with 12 figure

A Sensitive Near-Infrared Fluorescent Probe for Detecting Heavy Metal Ag+ in Water Samples

Silver is a common catalyst in industrial production, and the frequent use of Ag+ can cause water pollution. Thus, the detection of Ag+ in the environment is necessary to determine the level of pollution from silver. In this work, we designed a new, highly selective near-infrared (NIR) fluorescent probe QCy to detect Ag+. The probe exhibits “turn-off” fluorescence quenching responses at 760 nm towards Ag+ over other relevant cations, with outstanding sensitivity and a low detection limit (0.03 µM), which is considerably lower than the standard of the World Health Organization (WHO) for drinking water (0.9 µM). Meanwhile, QCy showed a very good linearity at a low concentration of Ag+ with a ‘naked eye’ visible color change of solution from blue to red. The probe has been applied successfully for the detection of Ag+ in real water samples

Journal bearing condition monitoring based on the modulation signal bispectrum analysis of vibrations

Journal bearings usually wok under a wide range of operating conditions. However, adverse operating such as transient operations and oil degradation can lead to early defects to the bearings. In this paper, modulation signal bispectrum (MSB) is used to analyse vibration responses from a journal bearing lubricated with three different oils to differentiate abnormal lubrication conditions. MSB magnitude results represent the nonlinear vibration responses, which are due to instable hydrodynamics, asperity excitations and nonlinear transfer paths, with two distinctive bifrequency patterns corresponding to instable lubrication and asperity interactions respectively. Using entropy measures, these instable lubrications are classified to be the low loads cases. Furthermore, average MSB magnitudes are used to differentiate the asperity interactions between asperity collisions and the asperity churns. A higher magnitude in the lower frequency band can indicate the excessive asperity contacts due to lowering viscosities. Meanwhile a higher magnitude in the higher frequency band indicates the extreme fluid frictions

Alien, Naturalized and Invasive Plants in China

Invasive species are a subset of naturalized species, and naturalized species are a subset of alien species. Determining the relationship among these three assemblages would be helpful in predicting and preventing biological invasion. Here, we reviewed the families, lifeforms, origins, introduction pathways and phylogenetic diversity of alien, naturalized and invasive vascular plants in China. The results show that species in the Asteraceae, Fabaceae and Poaceae families had a high dominance among alien, naturalized and invasive species. Moreover, almost all alien species in the Amaranthaceae, Solanaceae, Convolvulaceae and Euphorbiaceae families became naturalized species, and about 26.7% of the naturalized species became invasive species. Perennial herbs comprised a higher proportion of alien species than did annual herbs, though annual herbs were more suited to becoming invasive than perennial herbs. A considerable proportion (57.8%) of invasive species were introduced from America. More than half (56.5%) of alien species were introduced for their ornamental value, and half of these have become naturalized in China. Moreover, about half (55.2%) of all invasive species were introduced for their economic value (including ornamental, foraging and medicinal purposes). Invasive species were phylogenetically clustered and phylogenetically distant from alien and naturalized species, which indicates that phylogenetic differences could be helpful in becoming invasive. There is no doubt that human activity plays a significant role in biological invasion. This study suggests that when introducing alien species to a region, decision-makers should certainly consider the species’ phylogeny, beyond just its fundamental characteristics

Alien, Naturalized and Invasive Plants in China

Invasive species are a subset of naturalized species, and naturalized species are a subset of alien species. Determining the relationship among these three assemblages would be helpful in predicting and preventing biological invasion. Here, we reviewed the families, lifeforms, origins, introduction pathways and phylogenetic diversity of alien, naturalized and invasive vascular plants in China. The results show that species in the Asteraceae, Fabaceae and Poaceae families had a high dominance among alien, naturalized and invasive species. Moreover, almost all alien species in the Amaranthaceae, Solanaceae, Convolvulaceae and Euphorbiaceae families became naturalized species, and about 26.7% of the naturalized species became invasive species. Perennial herbs comprised a higher proportion of alien species than did annual herbs, though annual herbs were more suited to becoming invasive than perennial herbs. A considerable proportion (57.8%) of invasive species were introduced from America. More than half (56.5%) of alien species were introduced for their ornamental value, and half of these have become naturalized in China. Moreover, about half (55.2%) of all invasive species were introduced for their economic value (including ornamental, foraging and medicinal purposes). Invasive species were phylogenetically clustered and phylogenetically distant from alien and naturalized species, which indicates that phylogenetic differences could be helpful in becoming invasive. There is no doubt that human activity plays a significant role in biological invasion. This study suggests that when introducing alien species to a region, decision-makers should certainly consider the species’ phylogeny, beyond just its fundamental characteristics