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51.
A case study of the application of an iterative technique for determination of predictive accuracy is presented. The method uses Monte Carlo simulations and split sampling techniques to verify model accuracy. Examination of the ability of a linear parametric runoff loading model's ability to project total phosphorus loadings reveals the sensitivity of the model to calibration procedures. Predictive reliability was found to vary widely as the number of rainfall events considered in the calibration process changed. Predictive reliability was substantially increased by imposing calibration constraints which ensured that a wide distribution of values of the independent variable were presented in the calibration pool.Although the linear model is theoretically weak in its representation of the runoff loading phenomenon, it displays relatively stable predictive capabilities which warrant its consideration for use in management studies. The predictive errors associated with loading projections limit the linear model's value to applications insensitive to errors in the loading projections for individual storm events. This study provides further evidence of the need to consider uncertainties associated with the modelling of water quality phenomena. 相似文献
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B. Niczyporuk Z. Jakubowski T. Zełudziewicz G. Folger B. Lurz H. Vogel U. Volland H. Wegener J. K. Bienlein R. Graumann H. -J. Trost M. Schmitz F. H. Heimlich R. Nernst A. Schwarz U. Strohbusch P. Zschorsch K. W. Chen A. C. König D. J. Schotanus M. Coles A. Engler R. W. Kraemer D. Marlow F. Messing C. Rippich S. Youssef A. Fridman G. Alexander A. Av-Shalom G. Bella J. Grunhaus W. Langguth M. Scheer LENA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1983,17(3):197-202
A search for the decays γ→ρπ, γ→J/ψX and γ→γa (whereX is undetermined and a is an axion) has been completed using the LENA detector at the DORIS storage ring. No evidence for any of these processes was found. For these decay modes we set branching fraction upper limits (90% C.L.) of 2.1×10?3, 2.0×10?2 and 9.1×10?4, respectively. 相似文献
54.
M. Della Negra D. Drijard H.G. Fischer G. Fontaine H. Frehse P. Frenkiel G. Ghesquière R. Gokieli P. Hanke P.G. Innocenti W. Isenbeck E.E. Kluge V. Korbel S. Krzywdzinski D. Linglin A. Minten D.R.O. Morrison A. Putzer D. Wegener 《Physics letters. [Part B]》1975,59(4):401-404
Events with a positive particle of large transverse momentum emitted at medium angles have been studied using the split field magnet spectrometer at the CERN-ISR at a c.m. energy of √s = 52.5 GeV. Positive particles with large longitudinal momentum, |x| > 0.5, i.e., leading particles, associated to large pT events, are analysed. 相似文献
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The conductivity of alpha-polyvinylidene fluoride is obtained from dielectric measurements performed in the frequency domain at several temperatures. At temperatures above the glass-transition, the conductivity can be interpreted as an ionic conductivity, which confirms earlier results reported in the literature. Our investigation shows that the observed ionic conductivity is closely related to the amorphous phase of the polymer. 相似文献
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The Fe3+-spin in alums of type (Fe x , A11-x )NH4(SO4)2 · 12 H2O interacts (i) with the crystal lattice viaLS-coupling, and (ii) with the spins of the adjacent Fe3+-ions via magnetic dipole-dipole interaction. These interactions lead to a time fluctuation of the spin direction, characterized by correlation times τ c and τ′ c of increasing order. The times may be deduced from the57Fe-Mössbauer spectra of the alums, τ c from the width, and τ′ c ≈τ c from the position of the hyperfine structure lines. The theoretical interpretation of the Mössbauer spectra is relatively simple, when (i) the spin-lattice interaction gets frozen in, and (ii) a strong applied magnetic fieldH a decouples the spins of the Fe3+-ion and the57Fe-nucleus. The spectra were taken, therefore, at 4.2 °K and 8 kOe≦H a ≦ 54 kOe. According to the 1/r 3-dependence of the magnetic dipole-dipole interaction τ c should be related tox, the Fe-concentration, τ c ·x≈τ0=const. Forx≧0.5 our experimental results are in agreement with this rule when τ0=(1.5±0.5) · 10?9 s. For an alum withx=0.26, however, the observed spectra cannot be explained in terms of temporal spin fluctuations, at least not in the framework of the models which are available now. Here, presumedly, the electron spins of adjacent Fe3+-ions are coupled to more or less isolated and, consequently, relatively stationary spin clusters of various sizes, leading to many time independent internal magnetic fields. A treatment of this proposal is in preparation. 相似文献
60.
Some phonon dispersion curves in ZnO have been determined by inelastic neutron scattering. Shell model calculations with 10 parameters were fitted to the neutron data, to optical frequencies and to dielectric constants. Good agreement was obtained including some elastic constants which were calculated from the model. 相似文献