Two interpretations of human evolution: Essentialism and Darwinism

Despite intensive studies of a large number of fossils discovered during the 20th century there is no consensus as to the interpretation of the process of hominin evolution. Some authors see as many as six genera and some 17 species, while others argue for a single lineage from Plio/Pleistocene until today. Such diversity of interpretations of the same facts indicates lack of a uniform theoretical basis underlying studies of human evolution. Debates can be resolved using basic principles of scientific inquiry - parsimony and falsification of null hypotheses. Hypothesis testing is now possible with respect to the evolution of basic hominin characteristics such as brain size, body size and the size of the dentition that have sample sizes of a few hundred individual data points each. These characters display a continuous change with time. Analyses of variance do not falsify the null hypothesis of the existence of only one species at any time - variances around regression lines on time do not differ from the variance observed in the single species of Homo sapiens - distributions of residuals are normal. Thus, splitting of the hominin lineage into coeval species can only be based on descriptive characteristics that are liable to errors of subjective judgment.Maciej Henneber

Analiza dynamiki procesu podnoszenia ładunku

Proposals of two models of a load lifted by cranes have been discussed. Special attention has been paid to the phenomena occuring before detachment of the load from the ground. Stick-slip motion of the load on the foundation has been observed. One of two models presented - the model in the form of a rigid body resting on an elastic foundation has turned out to be more advantageous for the analysis of the lifting process. The results of numerical computations have revealed a phenomenon of solution bifurcation that occurs at a slight change in values of parameters of the model.W pracy zostały omówione propozycje modeli przeznaczonych do wykorzystania w analizie dynamiki ładunku podwieszonego przez dźwignice. Szczególna uwaga została zwrócona na zjawiska zachodzące przed oderwaniem ładunku od podłoża. Spośród dwóch przedstawionych modeli ładunku bardziej przydatny do analizy procesu podnoszenia okazał się model w postaci sztywnej bryły i sprężystego podłoża. Wyniki otrzymane z przeprowadzonych obliczeń numerycznych ujawniły zjawisko bifurkacji rozwiazania przy niewielkiej zmianie wartości parametrów modelu

3D dynamic model of the unicycle – unicyclist system

The problem of motion of a unicycle – unicyclist system in 3D is studied. The equations of motion of the system were derived using the Boltzmann-Hamel equations. Automatic generation of the Hamel coefficients eliminates all the difficulties associated with the determination of these equations. Description of the unicycle – unicyclist system dynamical model and simulation results are presented in the paper

Doubly transient chaos : Generic form of chaos in autonomous dissipative systems

Chaos is an inherently dynamical phenomenon traditionally studied for trajectories that are either permanently erratic or transiently influenced by permanently erratic ones lying on a set of measure zero. The latter gives rise to the final state sensitivity observed in connection with fractal basin boundaries in conservative scattering systems and driven dissipative systems. Here we focus on the most prevalent case of undriven dissipative systems, whose transient dynamics fall outside the scope of previous studies since no time-dependent solutions can exist for asymptotically long times. We show that such systems can exhibit positive finite-time Lyapunov exponents and fractal-like basin boundaries which nevertheless have codimension one. In sharp contrast to its driven and conservative counterparts, the settling rate to the (fixed-point) attractors grows exponentially in time, meaning that the fraction of trajectories away from the attractors decays superexponentially. While no invariant chaotic sets exist in such cases, the irregular behavior is governed by transient interactions with transient chaotic saddles, which act as effective, time-varying chaotic sets