The statistical impact of experimental result scatter of asphalt mixtures on their numerical modelling

The paper presents selected test results of asphalt mixture conducted in low temperatures. The obtained parameters are highly diverse. It concerns ultimate breaking loads, stiffness parameters related to Young's modulus but also the fracture course. Statistical analysis upon the results makes it possible to relevantly estimate the material-defining parameter values. Such a random approach leads to the mean values of breaking and fracture-triggering loads, dealing with their dispersion too. The estimated parameters allow to form appropriate numerical models of asphalt mixture specimens. This type of analysis supports the laboratory tests. The paper presents the authors' simplified model considering non-uniform material features. The results reflect the scatter of real laboratory test outcomes. In order to do so an algorithm to calibrate the numerical model parameters was created

Monte Carlo simulations of the fracture resistance degradation of asphalt concrete subjected to environmental factors

The paper presents the results of laboratory tests of SCB (semi-circular beam) samples of asphalt concrete, subjected to the destructive effect of water and frost as well as the aging processes. The determined values of material parameters show significant dispersions, which makes the design of mixtures difficult. Statistical analysis of the test results supplemented by computer simulations made with the use of the proprietary FEM model was carried out. The main distinguishing feature of the model is the assignment of material parameters of coarse aggregate and bituminous mortar to randomly selected finite elements. The parameters of the mortar are selected by trial and error to match the numerical results to the experimental ones. The stiffness modulus of the bituminous mortar is, therefore, a substitute parameter, taking into account the influence of many factors, including material degradation resulting from the aging and changing environmental conditions, the influence of voids, and contact between the aggregate and the bituminous mortar. The use of the Monte Carlo method allows to reflect the scattering of the results obtained based on laboratory tests. The computational algorithm created in the ABAQUS was limited only to the analysis of the global mechanical bending response of the SCB sample, without mapping the failure process in detail. The combination of the results of laboratory tests usually carried out on a limited number of samples and numerical simulations provide a sufficiently large population of data to carry out a reliable statistical analysis, and to estimate the reliability of the material designed

The study of damping control in semi-active car suspension

Paper discusses apparently opposing goal functions in terms of car’s comfort and handling. Short descriptions of passive, semi-active and active suspensions with their features are included. Thereafter, employing a two-mass quarter car model, an idea of damping control strategy in semi-active car suspension is presented. The results of performed simulation tests for various inputs are depicted and thoroughly discussed with comparison to classical passive suspension’s response. On the grounds of obtained results, conclusions are formulated. What is more, a layout of further work is outlined, with the aim of system’s response optimization in terms of comfort and handling features, as well as reliable validation of efficiency of proposed damping control strategy

Paediatric echocardiography in clinical practice. 2012 Recommendations of the Echocardiography Working Group of the Polish Cardiac Society

Echocardiography has become the primary imaging tool in the diagnosis and assessment of cardiological disorders in children. The purposes of this paper are to describe indications for paediatric echocardiography, define optimal instrumentation and laboratory setup for paediatric echocardiographic examinations and establish a baseline list of recommended measurements to be performed in a complete pediatric echocardiogram

Mechanical thrombectomy in acute stroke – Five years of experience in Poland

Objectives Mechanical thrombectomy (MT) is not reimbursed by the Polish public health system. We present a description of 5 years of experience with MT in acute stroke in Comprehensive Stroke Centers (CSCs) in Poland. Methods and results We retrospectively analyzed the results of a structured questionnaire from 23 out of 25 identified CSCs and 22 data sets that include 61 clinical, radiological and outcome measures. Results Most of the CSCs (74%) were founded at University Hospitals and most (65.2%) work round the clock. In 78.3% of them, the working teams are composed of neurologists and neuro-radiologists. All CSCs perform CT and angio-CT before MT. In total 586 patients were subjected to MT and data from 531 of them were analyzed. Mean time laps from stroke onset to groin puncture was 250±99min. 90.3% of the studied patients had MT within 6h from stroke onset; 59.3% of them were treated with IV rt-PA prior to MT; 15.1% had IA rt-PA during MT and 4.7% – emergent stenting of a large vessel. M1 of MCA was occluded in 47.8% of cases. The Solitaire device was used in 53% of cases. Successful recanalization (TICI2b–TICI3) was achieved in 64.6% of cases and 53.4% of patients did not experience hemorrhagic transformation. Clinical improvement on discharge was noticed in 53.7% of cases, futile recanalization – in 30.7%, mRS of 0–2 – in 31.4% and mRS of 6 in 22% of cases. Conclusion Our results can help harmonize standards for MT in Poland according to international guidelines

Fractals: construction or emergence? : part II. Fractals' emergence in quasi-empirical approach

Celem, jaki stawiamy sobie w drugiej części naszego filozoficznego dyptychu, jest próba podjęcia dyskusji nad usytuowaniem refleksji o charakterze metaprzedmiotowym dotyczącej struktur fraktalnych w klasycznej problematyce filozofii matematyki. Pokażemy, że struktury fraktalne prowadzą do istotnego poszerzenia wskazanej problematyki poza tradycyjne ramy wyznaczane przez pytania o naturę obiektów matematycznych (ontologia matematyki) czy status wiedzy matematycznej ( epistemologia matematyczna). Interesują nas specjalnie dwie kwestie: (1) czy, i w jakim sensie, proces generowania struktur fraktalnych świadczy o quasi-empirycznym charakterze tzw. nowej matematyki; (2) czy rozwijana w filozofii koncepcja emergencji nadaje się jako narzędzie badawcze do charakterystyki własności wspomnianych struktu

Fractals: construction or emergence? : part I. Fractal units of emergence in classical conceptual scheme

W projekcie badawczym, który w zamyśle będzie składał się z dwóch merytorycznie i logicznie powiązanych artykułów, formułujemy taki schemat pojęciowy, w którym adekwatna staje się charakterystyka struktur fraktalnych w kategoriach filozoficznej koncepcji emergencji. W pracy pierwszej przedstawiamy główne idee filozofii emergencji oraz dokonujemy prób uchwycenia w procesie generowania fraktali jednostek emergentnych. Pozostajemy jednak w obrębie klasycznego rozumienia badanej relacji. W pracy drugiej, na podstawie zademonstrowanych słabości ujęć klasycznych, jako niewystarczających w specyficznym kontekście badanych struktur matematycznych, pokazujemy, że dyskurs nad emergencją w matematyce staje się sensowny i uprawniony w ugruntowanym w filozofii nauk formalnych quasi-empirycznym podejściu do niektórych zagadnień w matematyc