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  • 1
    Electronic Resource
    Electronic Resource
    Renormalized stress tensors on ellipses (1992)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 33 (1992), S. 2434-2439 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The stress-energy tensor of a conformally invariant field is calculated in a two-dimensional Euclidean space-time with elliptical boundary. The results are expressed in terms of elliptic functions and are displayed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.529613
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  • 2
    Electronic Resource
    Electronic Resource
    Classification of faults in gearboxes — pre-processing algorithms and neural networks (1997)
    Springer
    Neural computing & applications 5 (1997), S. 160-183 
    Details
    ISSN: 1433-3058
    Keywords: Fault detection ; Gearbox vibration ; Machinery diagnostics ; Neural networks ; Pattern recognition ; Pre-processing algorithms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Classical signal processing techniques when combined with pattern classification analysis can provide an automated fault detection procedure for machinery diagnostics. Artificial neural networks have recently been established as a powerful method of pattern recognition. The neural networkbased fault detection approach usually requires preprocessing algorithms which enhance the fault features, reducing their number at the same time. Various timeinvariant and timevariant signal preprocessing algorithms are studied here. These include spectral analysis, time domain averaging, envelope detection, Wigner-Ville distributions and wavelet transforms. A neural network pattern classifier with preprocessing algorithms is applied to experimental data in the form of vibration records taken from a controlled tooth fault in a pair of meshing spur gears. The results show that faults can be detected and classified without errors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01413861
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  • 3
    Electronic Resource
    Electronic Resource
    Pseudo-fault induction in engineering structures: Multi-input multi-output control (1995)
    Springer
    Nonlinear dynamics 8 (1995), S. 367-384 
    Details
    ISSN: 1573-269X
    Keywords: Nonlinear systems ; fault induction ; Volterra series
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In a previous paper, it was demonstrated that any linear system could be made to respond to harmonic excitation as if a static nonlinearity of specified type and position were present, this response being obtained at a single predetermined point on the structure. The method requires the excitation of the linear structure by an additional or auxiliary input. In the present paper, the theory is extended to allow the possibility of producing a specified nonlinear response at more than one point on a linear structure. It is shown that N responses can be obtained by specifying N or less auxiliary inputs. The theory is also extended to provide for polynomial damping in addition to stiffness nonlinearity. The theory is validated using numerical simulation of MDOF lumped-parameter systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00045622
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  • 4
    Electronic Resource
    Electronic Resource
    An improved nonlinear model for an automotive shock absorber (1992)
    Springer
    Nonlinear dynamics 3 (1992), S. 413-429 
    Details
    ISSN: 1573-269X
    Keywords: Restoring face surface ; shock absorber ; nonlinear damping ; extended model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A new physical model for a shock absorber is presented which provides a more realistic representation of the stiffness characteristics than previous simple models. The new model is validated on experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00045646
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  • 5
    Electronic Resource
    Electronic Resource
    Analysis of Wind Fluctuations Using the Orthogonal Wavelet Transform (1997)
    Springer
    Flow, turbulence and combustion 59 (1997), S. 205-218 
    Details
    ISSN: 1573-1987
    Keywords: atmospheric boundary layer ; coherent structures ; wavelets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper presents a study of velocity fluctuations occurring in the stably stratified atmospheric boundary layer over an Antarctic ice shelf. The approach is based on wavelet analysis which has advantages over conventional Fourier analysis. Two case studies are presented, comprising: ‘pure’ turbulent flow and a large amplitude solitary wave.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1001183421720
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  • 6
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    Corrigendum: Rapid increases in tropospheric ozone production and export from China (2016)
    Springer Nature
    Details
    Publication Date: 2016-07-30
    Description: Nature Geoscience 9, 643 (2016). doi:10.1038/ngeo2768 Author: Willem W. Verstraeten, Jessica L. Neu, Jason E. Williams, Kevin W. Bowman, John R. Worden & K. Folkert Boersma
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 7
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    Rapid increases in tropospheric ozone production and export from China (2015)
    Springer Nature
    Details
    Publication Date: 2015-08-28
    Description: Nature Geoscience 8, 690 (2015). doi:10.1038/ngeo2493 Authors: Willem W. Verstraeten, Jessica L. Neu, Jason E. Williams, Kevin W. Bowman, John R. Worden & K. Folkert Boersma Rapid population growth and industrialization have driven substantial increases in Asian ozone precursor emissions over the past decade, with highly uncertain impacts on regional and global tropospheric ozone levels. According to ozonesonde measurements, tropospheric ozone concentrations at two Asian sites have increased by 1 to 3% per year since 2000, an increase thought to contribute to positive trends in the ozone levels observed at North America’s West Coast. However, model estimates of the Asian contribution to North American ozone levels are not well-constrained by observations. Here we interpret Aura satellite measurements of tropospheric concentrations of ozone and its precursor NO2, along with its largest natural source, stratospheric ozone, using the TM5 global chemistry–transport model. We show that tropospheric ozone concentrations over China have increased by about 7% between 2005 and 2010 in response to two factors: a rise in Chinese emissions by about 21% and increased downward transport of stratospheric ozone. Furthermore, we find that transport from China of ozone and its precursors has offset about 43% of the 0.42 DU reduction in free-tropospheric ozone over the western United States that was expected between 2005 and 2010 as a result of emissions reductions associated with federal, state and local air quality policies. We conclude that global efforts may be required to address regional air quality and climate change.
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 8
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    Sensitivity of outgoing longwave radiative flux to the global vertical distribution of ozone characterized by instantaneous radiative kernels from Aura-TES (2011)
    Wiley
    Details
    Publication Date: 2011-07-28
    Description: We calculate the sensitivity of outgoing longwave radiation (OLR) to the global vertical distribution of tropospheric ozone using ozone profile estimates from Aura Tropospheric Emission Spectrometer (Aura-TES) along with the partial derivatives of spectral radiance with respect to ozone from the Aura-TES operational retrieval algorithm. Accounting for anisotropy, we calculate top of atmosphere instantaneous radiative kernels (IRKs), in W/m2/ppb, for infrared ozone absorption from 985 to 1080 cm−1. Zonal mean distributions for August 2006 show significant variations in the IRK between clear and cloudy sky, ocean and land, and day and night over land. For all sky (clear and cloudy conditions), OLR is significantly less sensitive to ozone in the middle and lower troposphere due to clouds, especially in the tropics. We also compute the longwave radiative effect (LWRE), i.e., the reduction in OLR due to absorption by tropospheric ozone, and find a global average LWRE of 0.33 ± 0.02−0.007+0.018 W/m2 (with uncertainty and bias) for tropospheric ozone with significant variability (σ = 0.23W/m2) under all sky conditions for August 2006. For clear sky, tropical conditions we examine the effect of water vapor in reducing the LWRE from tropospheric ozone.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
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    Impacts of midlatitude precursor emissions and local photochemistry on ozone abundances in the Arctic (2012)
    Wiley
    Details
    Publication Date: 2012-01-11
    Description: We assess the impact of transport of pollution from midlatitudes on the abundance of ozone in the Arctic in summer 2006 using the GEOS-Chem global chemical transport model and its adjoint. We find that although the impact of midlatitude emissions on ozone abundances in the Arctic is at a maximum in fall and winter, in July transport from North America, Asia, and Europe together contributed about 25% of surface ozone abundances in the Arctic. Throughout the summer, the dominant source of ozone in the Arctic troposphere was photochemical production within the Arctic, which accounted for more than 50% of the ozone in the Arctic boundary layer and as much as 30%–40% of the ozone in the middle troposphere. An adjoint sensitivity analysis of the impact of NOx emissions on ozone at Alert shows that on synoptic time scales in both the lower and middle troposphere, ozone abundances are more sensitive to emissions between 50°N and 70°N, with important influences from anthropogenic, biomass burning, soil, and lightning sources. Although local surface NOx emissions contribute to ozone formation, transport of NOx in the form of peroxyacetyl nitrate (PAN) from outside the Arctic and from the upper troposphere also contributed to ozone production in the lower troposphere. We find that in late May and June the release of NOx from PAN decomposition accounted for 93% and 55% of ozone production at the Arctic surface, respectively.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 10
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    Reflux dolomitization of the Upper Permian Changxing Formation and the Lower Triassic Feixianguan Formation, NE Sichuan Basin, China (2013)
    Wiley
    In: Geofluids
    Details
    Publication Date: 2013-04-14
    Description: Natural gas is found in Upper Permian and Lower Triassic dolomite reservoirs of the NE Sichuan Basin, China. Studying the mechanisms for porosity-modifying dolomitization and predicting its spatial distribution is of great importance for exploration and field appraisal. Subsurface core samples from the oolitic Lower Triassic Feixianguan Formation and outcrop samples reef carbonate Upper Permian Changxing Formation were studied using cathodoluminescence (CL), electron microprobe, fluid inclusion and isotope studies (δ 18 O, δ 13 C and 87 Sr/ 86 Sr), in an attempt to determine the origin of the dolomitizing fluids. Trace element and isotope data show that Lower Triassic seawater was most likely responsible for dolomitization of both the Permian and Triassic rocks. Sr/Ca molar ratios, calculated for the diagenetic fluid, suggest seawater was involved in dolomitization. Strontium isotope data suggest that seawater 87 Sr/ 86 Sr during the Jialingjiang (Lower Triassic) reached 0.7078; this ratio is recorded ubiquitously in both Lower Triassic oolitic dolomite and the underlying Lower Permian reef dolomite. In the Permian Changxing Formation, elevated Triassic 87 Sr/ 86 Sr values have overprinted the significantly lower 87 Sr/ 86 Sr ratio characteristic of Upper Permian seawater. Fluid inclusion analysis led to the conclusion that dolomitization must have commenced at a temperature lower than about 50°C. Integrating the sedimentology, petrology and geochemistry data, we conclude that coeval Lower Triassic (Feixianguan or slightly younger) seawater caused dolomitization by a reflux-seepage process for both the Lower Triassic and Upper Permian units. There is no evidence for deep burial or meteoric-marine mixing-zone dolomitization. It is likely that evaporating seawater initially flowed into the highly porous oolitic Feixianguan Formation in a sabkha/lagoonal setting and precipitated anhydrite nodules and beds. Concomitant dolomitization, in the underlying Permian reef carbonates, continued during seepage even after the supply of sulphate was exhausted, leading to an absence of anhydrite in Permian Changxing Formation.
    Print ISSN: 1468-8115
    Electronic ISSN: 1468-8123
    Topics: Geosciences
    Published by Wiley
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