2,238 research outputs found
Prediction and Study of Air Thermal Parameters in Unexploited Mine Regions Based on Temperature Prediction Model in Whole Ventilation Network
AbstractMines with heat disaster danger have been increased year by year, in order to provide basic data for mine air- conditioning design, prediction of air thermal parameters in the mine unexploited region becomes particularly important. But at present, prediction of air thermal parameters is realized mainly by empirical formula and forecast method of single-line(main trunk road method), existing many disadvantages such as strong individual subjectivity, bad theoretical property and low forecasting precision. Therefore, a kind of air temperature prediction model in whole ventilation network based on wind enthalpy equation is put forward. By the model, air temperature prediction software in whole ventilation network which can make reasonable forecast of thermal parameters for different high temperature mines is programmed by determining air thermal parameters through wind energy equation and considering the influence of natural wind pressure. Through the prediction of the air thermal parameters of the wind route in the fifth mining area in east wing of Dongtan colliery, it can be seen that air temperature prediction model in whole ventilation network is scientific, reasonable and with strong operating nature, which can meet the requirements of the prediction of air thermal parameters in unexploited region of high temperature mines
Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. III. Detection of Fe II Reverberation in Nine Narrow-Line Seyfert 1 Galaxies
This is the third in a series of papers reporting on a large
reverberation-mapping campaign aimed to study the properties of active galactic
nuclei (AGNs) with high accretion rates. We present new results on the
variability of the optical Fe II emission lines in 10 AGNs observed by the
Yunnan Observatory 2.4m telescope during 2012--2013. We detect statistically
significant time lags, relative to the AGN continuum, in nine of the sources.
This accurate measurement is achieved by using a sophisticated spectral fitting
scheme that allows for apparent flux variations of the host galaxy, and several
narrow lines, due to the changing observing conditions. Six of the newly
detected lags are indistinguishable from the Hbeta lags measured in the same
sources. Two are significantly longer and one is slightly shorter. Combining
with Fe II lags reported in previous studies, we find a Fe II
radius--luminosity relationship similar to the one for Hbeta, although our
sample by itself shows no clear correlation. The results support the idea that
Fe II emission lines originate in photoionized gas which, for the majority of
the newly reported objects, is indistinguishable from the Hbeta-emitting gas.
We also present a tentative correlation between the lag and intensity of Fe II
and Hbeta and comment on its possible origin.Comment: 14 pages, 10 figures, accepted for publication in The Astrophysical
Journa
Factors related to children’s caries: a structural equation modeling approach
BACKGROUND: Dental caries among preschool children is highly prevalent in many less-developed countries. METHODS: A model which explored the factors related to children’s dental caries was tested in this study using structural equation modeling. Caregivers of children aged 5 years were surveyed on their socioeconomic status, and their oral health knowledge, attitudes and practices. In addition, information on their children’s oral health practices, dental insurance and dental service utilization were collected. Examination of caries was conducted on all children who returned fully completed questionnaires. RESULTS: The results showed that socioeconomic factors influenced children’s oral health practices through the impact of caregivers’ oral health knowledge and practices; that caregivers’ oral health knowledge affected children’s oral health practices through the influence of caregivers’ oral health attitudes and practices; and finally, that children’s oral health practices were linked directly to their caries. CONCLUSION: The findings have important applications for promoting policies aimed at advancing children’s oral health
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