Evaluation of the mechanical properties of fluvial coarsegrained soils from dynamic penetration test

Soil and rock properties are essential inputs for the design of geotechnical structures. But unlike man-made materials, the determination of the characteristic value is not simple, mostly because of the large space variability of the soils and rocks. In many cases, the large spatial variability makes it difficult to collect sufficient ground samples for further laboratory testing so that many tests are performed directly in the field. In Slovakia, the dynamic penetration test (DP) is, among others, a quite popular field test for soil investigation. From the measured data, it is possible to derive relative density (ID) shear (φ ef) and deformation (E def) parameters of coarse-grained soils. There are many available correlations between the DP results and geotechnical parameters. Therefore, it is necessary to choose the most appropriate one as it considerably affects the final evaluation. This paper shows the assessment of geotechnical parameters of coarse-grained fluvial soil from the DP results and presents the statistical determination of its characteristic values, which are furthermore compared with the nominal values used in Slovakia.

The Case against “Indirect” Statistical Inference

How to infer from uncontrolled data the numerical values of the parameters of an econometric model? In interwar econometrics, this problem of statistical induction was tackled in various ways. Wassily Leontief’s inter-industry method offers a case study of a nonprobabilistic approach to this problem of the statistical determination of a model’s parameter. Leontief was an outspoken critic of the probabilistic approach to econometrics and presented his interindustry device as an alternative. Focusing on his book published in 1941, The Structure of American Economy, 1929–1929, which gathered a decade of works since 1932, I show how it offered an original answer to the inferential problem of the parameters’ statistical determination. Between what Jan Tinbergen called, in the same period, the “historical method,” based on regression techniques applied to time series, and the “structural method,” relying on direct measures from cross-sectional data and controlled experiments, Leontief engaged in the latter in an ambitious project of “expansion of the field of direct observation.” This laid the statistical foundations of what he called the “direct induction” approach to empirical modeling.

Experimental indoor validation of weak intensity fluctuations over free-space optical communication link

In this paper, we present experimental results for characterizing turbulence phenomena in free-space optical (FSO) communication under laboratory controlled conditions. Collected data is used for statistical determination of the probability density function (PDF) of irradiance signal fluctuations. In literature, there are a number of empirical models for variety of turbulence regimes. Thus, obtained PDF is compared with selected models from the bibliography in order to describe properly statistical properties of real turbulent channel and help improving of FSO system performance calculation. In overall, analysis has shown that the results obtained under given constraints fit well with the exponentiated Weibull turbulence model.