The stability test for symmetric alpha-stable distributions

Symmetric alpha-stable distributions are a popular statistical model for heavy-tailed phenomena encountered in communications, radar, biomedicine, and econometrics. The use of the symmetric alpha stable model is often supported by empirical evidence, where qualitative criteria are used to judge the fit, leading to subjective decisions. Objective decisions can only be made through quantitative statistical tests. Here, a goodness-of-fit hypothesis test for symmetric alpha-stable distributions is developed based on their unique stability property. Critical values for the test are found using both asymptotic theory and from bootstrap estimates. Experiments show that the stability test, using bootstrap estimates of the critical values, is better able to discriminate between symmetric alpha stable distributions and other heavy-tailed distributions than classical tests such as the Kolmogorov-Smirnov test.     

Analysis of Multicomponent Polynomial Phase Signals

While the theory of estimation of monocomponent polynomial phase signals is well established, the theoretical and methodical treatment of multicomponent polynomial phase signals (mc-PPSs) is limited. In this paper, we investigate several aspects of parameter estimation for mc-PPSs and derive the Crameacuter-Rao bound. We show the limits of existing techniques and then propose a nonlinear least squares (NLS) approach. We also motivate the use the Nelder-Mead simplex algorithm for minimizing the nonlinear cost function. The slight increase in computational complexity is a tradeoff for improved mean square error performance, which is evidenced by simulation results     

Laboratory assessment of toxic activity of purified peptides extracted from chickpea seeds to two strains of the rice weevil Sitophilus oryzae (L.) (Coleoptera: Curculionidae)

Several peptides with entomotoxic properties were extracted from seeds of different chickpea varieties, by either aqueous or alcoholic phase extraction. The extracts were purified by anion-exchange chromatography followed by membrane dialysis. The toxicity of the purified extracts was tested on two different strains of the rice weevil, Sitophilus oryzae: a French strain feeding only on cereal grain and sensitive to pea phytotoxins (SS strain) and a Chinese strain naturally breeding on split pea (RS strain). The toxic activity of the different fractions isolated from the purified extracts was evaluated by the ‘artificial kernel method’, incorporating the fraction into a reconstituted (‘artificial’) kernel made from whole wheat flour. The toxicity of the fractions was assessed by determining the mortality of young adults of each S. oryzae strain after 7 and 14 d feeding. With the more toxic acidic fraction incorporated into the artificial kernel, the mortality rate of SS strain weevils was 83% and 100% after 7 and 14 d feeding, respectively. With all the alcoholic fractions, mortality of the SS strain remained very low. With RS strain weevils, mortality was negligible after 7 d or 14 d feeding on any peptide fraction of the extracts.     

Detection of sources using bootstrap techniques

Source detection in array processing can be viewed as a test for equality of eigenvalues. Such a test is proposed, based on a multiple test procedure that considers all pairwise comparisons between eigenvalues. Using the bootstrap to estimate the null distributions of the test statistics results in a procedure with minimal assumptions on the nature of the signal. Simulations show that the proposed test is superior to information theoretic criteria such as the MDL, which are based on Gaussian signals and large sample sizes. Performance in most cases exceeds the more powerful sphericity test     

Experimental study on the effects of big particles physical characteristics on the hydraulic transport inside a horizontal pipe

This paper presents an experimental study of the physical characteristic effects of large particles on hydraulic transport in a horizontal pipe. The particles are spherical and are large with respect to the diameter of the pipe (8%, 10%, 16%and 25%). Experiments were done to test the important parameters in solid transport (pressure, velocity, etc.). As a result, the relationship between the pressure gradient forces and the mixture velocity was sub-stantially different from the pure liquid flow. However, in a single-phase flow a monotonous behavior of the pres-sure drop curve is observed, and the curve of the solid particle flow attains its minimum at the critical velocity. The regimes are characterized with differential pressure measurements and visualizations.