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71.
An interpretation of Akeno giant air shower array (AGASA) data by comparing the experimental results with the simulated ones by cosmic ray simulation for KASCADE (CORSIKA) has been made. General features of the electromagnetic component and low energy muons observed by AGASA can be well reproduced by CORSIKA. The form of the lateral distribution of charged particles agrees well with the experimental one between a few hundred metres and 2000 m from the core, irrespective of the hadronic interaction model studied and the primary composition (proton or iron). It does not depend on the primary energy between 1017.5 and 1020 eV as the experiment shows. If we evaluate the particle density measured by scintillators of 5 cm thickness at 600 m from the core S0(600), suffix 0 denotes the vertically incident shower) by taking into account the similar conditions as in the experiment, the conversion relation from S0(600) to the primary energy is expressed as E (eV)=2.15×1017S0(600)1.015 within 10% uncertainty among the models and composition used, which suggests the present AGASA conversion factor is the lower limit. Although the form of the muon lateral distribution fits well to the experiment within 1000 m from the core, the absolute values change with hadronic interaction model and primary composition. The slope of the ρμ(600) (muon density above 1 GeV at 600 m from the core) vs. S0(600) relation in experiment is flatter than that in simulation of any hadronic model and primary composition. As the experimental slope is constant from 1015 to 1019 eV, we need to study this relation in a wide primary energy range to infer the rate of change of chemical composition with energy. 相似文献
72.
Anca Nemuc Iwona S. Stachlewska Jeni Vasilescu Anna Górska Doina Nicolae Camelia Talianu 《Acta Geophysica》2014,62(2):350-366
After Eyjafjallajökull volcano eruption on 14 April 2010, due to a complex air mass circulation, Romania was exposed to volcanic ash and its mixture with continental aerosols. Ash particles with an average Ångström (UV-VIS) exponent of 1.4 ± 0.2 and (VIS-IR) of 1.2 ± 0.3, a color ratio (VIS-UV) of 0.54 and (IR-VIS) of 0.49, an average particle depolarization value ~9.4%, and a lidar ratio of 50 sr were retrieved on 18 April from multiwavelength Raman lidar measurements in Bucharest. Mixed volcanic ash with mineral dust particles advected from Sahara, depolarization ~12%, Ångström (UV-VIS) exponent of 1.25 ± 0.25 and (VIS-IR) of 1.45 ± 0.25, an increased color ratio (VIS-UV) of 0.61, (IRVIS) of 0.39 and lidar ratio of 53 sr were identified on 28 April. From observations in Poland conducted by an elastic lidar at 532 nm and a ceilometer at 1064 nm we retrieved an average backscatter related Ångström (VIS-IR) exponent of 1.25 ± 0.35, and a color ratio (IR-VIS) of 0.53 in the layer at about 5.5 km during the night of 16/17 April, indicating fresh ash over Warsaw. 相似文献
73.
J Knapp 《Astronomy& Geophysics》2005,46(6):6.16-6.20
Johannes Knapp of the Pierre Auger Collaboration reports on the first promising results from the Pierre Auger Observatory. 相似文献
74.
The thermal expansion of gehlenite, Ca2Al[AlSiO7], (up to T=830 K), TbCaAl[Al2O7] (up to T=1100 K) and SmCaAl[Al2O7] (up to T=1024 K) has been determined. All compounds are of the melilite structure type with space group
Thermal expansion data were obtained from in situ X-ray powder diffraction experiments in-house and at HASYLAB at the Deutsches
Elektronen Synchrotron (DESY) in Hamburg (Germany). The thermal expansion coefficients for gehlenite were found to be: α1=7.2(4)×10−6×K−1+3.6(7)×10−9ΔT×K−2 and α3=15.0(1)×10−6×K−1. For TbCaAl[Al2O7] the respective values are: α1=7.0(2)×10−6×K−1+2.0(2)×10−9ΔT×K−2 and α3=8.5(2)×10−6×K−1+2.0(3)×10−9ΔT×K−2, and the thermal expansion coefficients for SmCaAl[Al2O7] are: α1=6.9(2)×10−6×K−1+1.7(2)×10−9ΔT×K−2 and α3=9.344(5)×10−6×K−1. The expansion mechanisms of the three compounds are explained in terms of structural trends obtained from Rietveld refinements
of the crystal structures of the compounds against the powder diffraction patterns. No structural phase transitions have been
observed. While gehlenite behaves like a ‘proper’ layer structure, the aluminates show increased framework structure behavior.
This is most probably explained by stronger coulombic interactions between the tetrahedral conformation and the layer-bridging
cations due to the coupled substitution (Ca2++Si4+)–(Ln
3++Al3+) in the melilite-type structure.
This article has been mistakenly published twice. The first and original version of it is available at . 相似文献
75.
David J. DeMaster Gary B. Knapp Charles A. Nittrouer 《Geochimica et cosmochimica acta》1983,47(10):1713-1723
Water column and seabed samples were obtained from 92 stations on the Amazon continental shelf during October of 1979. Uptake of silica near and southeast of the river mouth began at a salinity of 8%. and accounted for 17% of the riverine silica flux to this region. Uptake northwest of the river mouth began at a salinity of 20%. and resulted in 33% removal of the riverine silica flux. Examination of filtered suspended solids revealed abundant diatoms in the surface waters, including Coscinodiscus. Skeletonema, Synedra. and Thalassiosira. The biological uptake of silica appears to be dependent on three factors: turbidity, turbulence, and nutrient availability. There was no evidence of abiological removal of silica in the Amazon estuary. 75 to 88% of the silica removed from surface waters by diatoms dissolves prior to accumulation in the seabed. Based on the mean biogenic silica content of shelf sediment (0.25%) and estimates of rates of sediment accumulation, the biogenic silica accumulation rate on the shelf is 2 × 1012 g/yr, which represents only 4% of the dissolved silica supplied by the Amazon River. Biological uptake of silica in estuarine surface waters may not accurately reflect permanent removal of biogenic silica to the seabed because of dissolution which occurs in bottom waters and near the sediment-water interface. 相似文献
76.