Results 1 - 10 of 33545
Results 1 - 10 of 33545. Search took: 0.078 seconds
|Sort by: date | relevance|
[en] Formulas of fractal dimensions of multidimensional objects have been obtained though the relation of their performances. Critical fractal dimensions of conversion form of self-affinity to a self-similarity on a scale of measuring are defined. Our offered formulas do not contain empirical stationary values as against the results of known theories and correctly describe scale invariance properties of self-affine fractals. (author)
[en] We study the renormalization of generally covariant operators in quantum gravity near two dimensions. We consider the Ricci curvature as an example. We show that this operator can be renormalized in such a way to preserve the manifest covariance with respect to the volume-preserving diffeomorphism. We find that the Ricci curvature scales with a definite scaling dimension at short distance. The anomalous dimension is computed to the leading order in ε. We argue that it is natural to find such a scaling behavior if the spacetime becomes scale invariant at short distance. The Ricci curvature singularity at the big bang can be viewed as such a scaling phenomenon. copyright 1997 The American Physical Society
[en] Scaling criteria for Tehran Research Reactor, a Material Testing Reactor, under natural as well as forced circulation is derived based on fluid-to-fluid modeling. Using these criteria, the basic characteristics of scale model are determined. The aforementioned criteria are such as power density, temperature rise, mass flux, and size of the model. In general, numbers of scaling laws are less than the basic unknown characteristics variables of the model and consequently, many scale models can be established for the system under consideration. The choice of model designer has significant effect on final model and its distortion. In Tehran Research Reactor (TRR), the thickness of fuel plates and the width of coolant flow rate are very thin, indeed. For increasing these two parameters that may lead to an efficient and a better model; two strategies are to be employed. Either using different clad materials from those that are used in the prototype or changing type of the coolant fluid. (Author)
[en] Most inflationary models predict that the power-law index of the spectrum of density perturbations is close to 1, though not precisely equal to 1, |n-1|∼O(0.1), implying that the spectrum of density perturbations is nearly, but not exactly, scale invariant. However, there are models where n is significantly less than 1 (n∼0.7); a spectral index significantly greater than 1 is more difficult to achieve. Without recourse to specific models, we show very generally and very explicitly that n≅1 is a consequence of the slow-roll conditions for inflation and ''naturalness,'' and thus, that near scale invariance is a generic prediction of inflation and a test of the inflationary framework. We derive the conditions needed to deviate significantly from scale invariance, and then show, by explicit construction, the existence of smooth potentials that satisfy all the conditions for successful inflation and give n as large as 2. (c) 2000 The American Physical Society
[en] Recently it has been demonstrated that the connectivity transition from microscopic connectivity to macroscopic connectedness, known as percolation, is generically announced by a cascade of microtransitions of the percolation order parameter (Chen et al 2014 Phys. Rev. Lett. 112 155701). Here we report the discovery of macrotransition cascades which follow percolation. The order parameter grows in discrete macroscopic steps with positions that can be randomly distributed even in the thermodynamic limit. These transition positions are, however, correlated and follow scaling laws which arise from discrete scale invariance (DSI) and non self-averaging, both traditionally unrelated to percolation. We reveal the DSI in ensemble measurements of these non self-averaging systems by rescaling of the individual realizations before averaging. (paper)
[en] We discuss the existence of finite size scaling in nuclear fragmentation. Analyzing experimental data on high energy proton induced reactions on targets of various sizes we show finite size scaling in the production of intermediate mass fragments and we determine the empirical value of a ''fractal dimension'' which may give information on the internal structure of the fragments during the fragmentation process
[en] We perform a comparative statistical analysis between the acoustic-emission time series from the ancient Greek Athena temple in Syracuse and the sequence of nearby earthquakes. We find an apparent association between acoustic-emission bursts and the earthquake occurrence. The waiting-time distributions for acoustic-emission and earthquake time series are described by a unique scaling law indicating self-similarity over a wide range of magnitude scales. This evidence suggests a correlation between the aging process of the temple and the local seismic activity.
[en] The choice of the scaling laws and particularly the extrapolation of data measured in experimental facilities for application to real plants remains an important unresolved issue in Nuclear Reactor Safety. One of such experimental facilities, named PIPER-ONE, is in construction at 'Dipartimento di Costruzioni Meccaniche e Nucleari' of Pisa University with the aim of simulating Small Break LOCAs in BWRs. This paper presents an in depth analysis of scaling principles adopted in similar apparatuses in the world. Besides it deals with the problem of the extrapolating of experimental data to real systems; in order to achieve this, a comparative analysis is carried out with reference to calculated or measured transients arising or assumed in ROSA-III, FIX-II, PIPER-ONE and BWR plants. (orig.)
[en] Numerical experiments are carried out systematically to determine the neon soft x-ray yield Ysxr for optimized neon plasma focus with storage energy E0 from 0.2 kJ to 1 MJ. The ratio c = b/a, of outer to inner electrode radii, and the operating voltage V0 are kept constant. E0 is varied by changing the capacitance C0. Parametric variation at each E0 follows the order operating pressure P0, anode length z0 and anode radius a until all realistic combinations of P0, z0 and a are investigated. At each E0, the optimum combination of P0, z0 and a is found that produces the biggest Ysxr. At low energies the soft x-ray yield scales as Ysxr∼E01.6 whilst towards 1 MJ it becomes Ysxr∼E00.8. The Ysxr scaling laws are found to be Ysxr∼Ipeak3.2 (0.1-2.4 MA) and Ysxr∼Ipinch3.6 (0.07-1.3 MA) throughout the range investigated. When numerical experimental points with other c values and mixed parameters are included, there is evidence that the Ysxr versus Ipinch scaling is more robust and universal, remaining unchanged whilst the Ysxr versus Ipeak scaling changes slightly, with more scatter becoming evident.