406 research outputs found
Statistical analyses on multi-scale features of monitoring data from health monitoring system in long cable supported bridges
AbstractStrain-time histories and other data acquired from a structural health monitoring system (SHMS) installed on a bridge reflect the real-time structural response of the bridge under actual service and environmental loading. It is necessary to understand the inherent features of the data if we want to have confidence in using them to assess the health state or detect potential damage in the structure. This paper aims at exploring the inherent features of strain-time histories data from SHMS in order to find out their behavior in multiple temporal scales and to obtain reliable, clean and normalized data at the dominant scale of stresses inducing fatigue. Firstly, the strain history data from SHMS installed on Runyang Yangtze Bridges (RYB) were analyzed within three typical temporal scales to explore their different characteristics and their own cut-off frequency which span different orders of magnitude. Then, based on the description of the multi-scale features of the monitored data, a further investigation of the dominant scale controlling fatigue failures was carried out. The result shows that, the strain data corresponding to the typical temporal scales of 106, 103 and 100 sec are caused by temperature change, with cut-off frequency fc,1 in the 10−2 Hz range, by train load, with fc,2 in the 10−1 Hz range and by truck load, with fc,3 in the 100 Hz range. Noise shows significant coupling effect when coarse scale strain data are used for the evaluation, which may lead to significant error even it is in small level acceptable in engineering analyses
Assessment and Spatiotemporal Variation Analysis of Water Quality in the Zhangweinan River Basin, China
AbstractSpatiotemporal variation analysis of water quality and identification of water pollution sources in river basins is very important for water resources protection and sustainable utilization. In this study, fuzzy comprehensive analysis and two statistical methods including cluster analysis and seasonal Kendall test method were used to evaluate the spatiotemporal variation of water quality in the Zhangweinan River basin. The results for spatial cluster analysis and assessment on water quality at 19 monitoring sites indicated that water quality in the Zhangweinan River basin could be classified into two regions according to pollution levels. One is the Zhang River basin located in northwest of the Zhangweinan River basin where water quality is good. Another one includes the Wei River and eastern plain of the Zhangweinan River basin, and the water pollution in this region is serious, where the pollutants from point sources flow into the river and the water quality changes greatly. The results of temporal cluster analysis and seasonal Kendall test indicated that the sampling periods may be classified into three periods during 2002-2009 according to water quality. Results of temporal cluster analysis and seasonal Kendall test indicated that the study periods may be classified into three periods and two different trends was detected during the period of 2002-2009. The first period was the year of 2002-2003, during which water quality had deteriorated and serious pollution was observed in the Wei River basin and eastern plain of the Zhangweinan River basin. The second period was the year of 2004-2006, during which water quality became better. The year of 2007-2009 is the third period, during which water quality had been improved greatly. Despite that water quality in the Zhangweinan River basin had been improved during the period of 2004-2009, water quality in the Wei River (southwestern part of the basin), the Wei Canal River and the Zhangweixin River (eastern plain of the basin) is still poor. These results provide may useful information for better pollution control strategies in the Zhangweinan River basin
Characteristics and Sensing Properties of the La1-xNdxCo0.3Fe0.7O3 System for CO Gas Sensors
A series of nanostructured La1-xNdxCo0.3Fe0.7O3 perovskite-type (x ranging from 0 to 1) were prepared using the co-precipitation method. CO gas sensing properties of La1-xNdxCo0.3Fe0.7O3 sensors were performed. La0.7Nd0.3Co0.3Fe0.7O3 sensor showed the highest response at 250 °C (S=52.8)
Kir5.1 regulates Nedd4-2-mediated ubiquitination of Kir4.1 in distal nephron.
Kir4.1/5.1 heterotetramer participates in generating the negative cell membrane potential in distal convoluted tubule (DCT) and plays a critical role in determining the activity of Na-Cl cotransporter (NCC). Kir5.1 contains a phosphothreonine motif at its COOH terminus (AA249-252). Coimmunoprecipitation showed that Nedd4-2 was associated with Kir5.1 in HEK293 cells cotransfected with Kir5.1 or Kir4.1/Kir5.1. GST pull-down further confirmed the association between Nedd4-2 and Kir5.1. Ubiquitination assay showed that Nedd4-2 increased the ubiquitination of Kir4.1/Kir5.1 heterotetramer in the cells cotransfected with Kir4.1/Kir5.1, but it has no effect on Kir4.1 or Kir5.1 alone. Patch-clamp and Western blot also demonstrated that coexpression of Nedd4-2 but not Nedd4-1 decreased K currents and Kir4.1 expression in the cells cotransfected with Kir4.1 and Kir5.1. In contrast, Nedd4-2 fails to inhibit Kir4.1 in the absence of Kir5.1 or in the cells transfected with the inactivated form of Nedd4-2 (Nedd4-2C821A). Moreover, the mutation of TPVT motif in the COOH terminus of Kir5.1 largely abolished the association of Nedd4-2 with Kir5.1 and abolished the inhibitory effect of Nedd4-2 on K currents in HEK293 cells transfected with Kir4.1 and Kir5.1 mutant (Kir5.1T249A). Finally, the basolateral K conductance in the DCT and Kir4.1 expression is significantly increased in the kidney-specific Nedd4-2 knockout or in Kir5.1 knockout mice in comparison to their corresponding wild-type littermates. We conclude that Nedd4-2 binds to Kir5.1 at the phosphothreonine motif of the COOH terminus, and the association of Nedd4-2 with Kir5.1 facilitates the ubiquitination of Kir4.1, thereby regulating its plasma expression in the DCT
Acoustic phonon transport through a double-bend quantum waveguide
In this work, using the scattering matrix method, we have investigated the
transmission coefficients and the thermal conductivity in a double-bend
waveguide structure. The transmission coefficients show strong resonances due
to the scattering in the midsection of a double-bend structure; the positions
and the widths of the resonance peaks are determined by the dimensions of the
midsection of the structure. And the scattering in the double-bend structure
makes the thermal conductivity decreases with the increasing of the temperature
first, then increases after reaches a minimum. Furthermore, the investigations
of the multiple double-bend structures indicate that the first additional
double-bend structure suppresses the transmission coefficient and the frequency
gap formed; and the additional double-bend structures determine the numbers of
the resonance peaks at the frequency just above the gap region. These results
could be useful for the design of phonon devices.Comment: 13 pages, 6 figures, elsart.cls is use
Unraveling the Rich Fragmentation Dynamics Associated with S-H Bond Fission Following Photoexcitation of H <sub>2</sub>S at Wavelengths ∼129.1 nm
H2S is being detected in the atmospheres of ever more interstellar bodies, and photolysis is an important mechanism by which it is processed. Here, we report H Rydberg atom time-of-flight measurements following the excitation of H2S molecules to selected rotational (JKaKc′) levels of the 1B1 Rydberg state associated with the strong absorption feature at wavelengths of λ ∼ 129.1 nm. Analysis of the total kinetic energy release spectra derived from these data reveals that all levels predissociate to yield H atoms in conjunction with both SH(A) and SH(X) partners and that the primary SH(A)/SH(X) product branching ratio increases steeply with ⟨Jb2⟩, the square of the rotational angular momentum about the b-inertial axis in the excited state. These products arise via competing homogeneous (vibronic) and heterogeneous (Coriolis-induced) predissociation pathways that involve coupling to dissociative potential energy surfaces (PES(s)) of, respectively, 1A″ and 1A′ symmetries. The present data also show H + SH(A) product formation when exciting the JKaKc′ = 000 and 111 levels, for which ⟨Jb2⟩ = 0 and Coriolis coupling to the 1A′ PES(s) is symmetry forbidden, implying the operation of another, hitherto unrecognized, route to forming H + SH(A) products following excitation of H2S at energies above ∼9 eV. These data can be expected to stimulate future ab initio molecular dynamic studies that test, refine, and define the currently inferred predissociation pathways available to photoexcited H2S molecules
Kinetic energy driven superconductivity in doped cuprates
Within the t-J model, the mechanism of superconductivity in doped cuprates is
studied based on the partial charge-spin separation fermion-spin theory. It is
shown that dressed holons interact occurring directly through the kinetic
energy by exchanging dressed spinon excitations, leading to a net attractive
force between dressed holons, then the electron Cooper pairs originating from
the dressed holon pairing state are due to the charge-spin recombination, and
their condensation reveals the superconducting ground-state. The electron
superconducting transition temperature is determined by the dressed holon pair
transition temperature, and is proportional to the concentration of doped holes
in the underdoped regime. With the common form of the electron Cooper pair, we
also show that there is a coexistence of the electron Cooper pair and
antiferromagnetic short-range correlation, and hence the antiferromagnetic
short-range fluctuation can persist into the superconducting state. Our results
are qualitatively consistent with experiments.Comment: 6 pages, Revtex, two figures are included, corrected typo
Coupling between planes and chains in YBa2Cu3O7 : a possible solution for the order parameter controversy
We propose to explain the contradictory experimental evidence about the
symmetry of the order parameter in by taking into account
the coupling between planes and chains. This leads to an anticrossing of the
plane and chain band. We include an attractive pairing interaction within the
planes and a repulsive one between planes and chains, leading to opposite signs
for the order parameter on planes and chains, and to nodes of the gap because
of the anticrossing. Our model blends s-wave and d-wave features, and provides
a natural explanation for all the contradictory experimentsComment: 13 pages, revtex, 2 uucoded figure
Negatively Charged Excitons and Photoluminescence in Asymmetric Quantum Well
We study photoluminescence (PL) of charged excitons () in narrow
asymmetric quantum wells in high magnetic fields B. The binding of all
states strongly depends on the separation of electron and hole layers.
The most sensitive is the ``bright'' singlet, whose binding energy decreases
quickly with increasing even at relatively small B. As a result, the
value of B at which the singlet--triplet crossing occurs in the spectrum
also depends on and decreases from 35 T in a symmetric 10 nm GaAs well
to 16 T for nm. Since the critical values of at which
different states unbind are surprisingly small compared to the well
width, the observation of strongly bound states in an experimental PL
spectrum implies virtually no layer displacement in the sample. This casts
doubt on the interpretation of PL spectra of heterojunctions in terms of
recombination
Combined constraints on modified Chaplygin gas model from cosmological observed data: Markov Chain Monte Carlo approach
We use the Markov Chain Monte Carlo method to investigate a global
constraints on the modified Chaplygin gas (MCG) model as the unification of
dark matter and dark energy from the latest observational data: the Union2
dataset of type supernovae Ia (SNIa), the observational Hubble data (OHD), the
cluster X-ray gas mass fraction, the baryon acoustic oscillation (BAO), and the
cosmic microwave background (CMB) data. In a flat universe, the constraint
results for MCG model are,
()
,
()
,
()
,
()
, and ()
.Comment: 12 pages, 1figur
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