Number of found documents: 11532
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Excessive extrapolations of Einstein's equations
Křížek, Michal; Somer, L.
2020 - English
The standard cosmological model is surprisingly quite thoroughly investigated even though it possesses many paradoxes. We present several arguments indicating why excessive extrapolations of Einstein's equations to cosmological distances are questionable. First, we show how to express explicitly the first of Einstein's 10 partial differential equations to demonstrate their extremely large complexity. Therefore, it would be very difficult to find their solution for two or more bodies to model, e.g., the evolution of the Solar system. Further, we present some unexpected failures of the Schwarzschild and Friedmann solution of these equations. Then we explain why application of Einstein's equations to the whole universe represents incorrect extrapolations that lead to dark matter, dark energy, and several unrealistic situations. Finally, we give 10 further arguments showing why celebrated Einstein's equations do not describe reality well. Keywords: Einstein's equations; Schwarzschild solution; Friedmann equation Available in digital repository of the ASCR
Excessive extrapolations of Einstein's equations

The standard cosmological model is surprisingly quite thoroughly investigated even though it possesses many paradoxes. We present several arguments indicating why excessive extrapolations of ...

Křížek, Michal; Somer, L.
Matematický ústav, 2020

Slovo geologa.
Žák, Karel
2020 - Czech
Available at various institutes of the ASCR
Slovo geologa.

Žák, Karel
Geologický ústav, 2020

On the 3D Dynamics of the Wake Behind a Circular Cylinder
Uruba, Václav; Procházka, Pavel P.; Skála, Vladislav
2020 - English
Flow in the wake of a circular cylinder is studied experimentally using time-resolved stereo PIV method. Special attention is paid to 3D topology of dynamical structures. While the distribution of statistic quantities along the cylinder is uniform, and i.e. 2D, the instantaneous flow structure is fully 3D. Within the velocity fluctuating flow field the structures containing streamwise vorticity and velocity components are dominant. The POD modes connected with von Kármán vortex street are identified. Keywords: circular cylinder; wake; 3D structure; POD Fulltext is available at external website.
On the 3D Dynamics of the Wake Behind a Circular Cylinder

Flow in the wake of a circular cylinder is studied experimentally using time-resolved stereo PIV method. Special attention is paid to 3D topology of dynamical structures. While the distribution of ...

Uruba, Václav; Procházka, Pavel P.; Skála, Vladislav
Ústav termomechaniky, 2020

Charakterizace Božanského pískovce: pilotní lomové testy
Kumpová, I.; Rozsypalová, I.; Vavro, Leona; Vavro, Martin; Keršner, Z.
2020 - Czech
Cíl příspěvku představuje charakterizacipískovce zlomu Božanov u Broumova,Česká republika,pomocí pilotních lomových testů. Pět zkušebních těles z jádrových vývrtůnominálního průměru 50mm a délek 100 a125mm bylo před testy opatřeno koncentrátorem napětí ve tvaru šípového vrubu a zatěžováno spožadavkem konstantního přírůstku posunu vkonfiguraci tříbodového ohybu lisemLabTest 6.250 vlaboratoři Ústavu stavebního zkušebnictví FAST VUT vBrně. Snímaných diagramů síla–posun bylo po jejich korekci využito kvyčíslení základních lomově-mechanických parametrůstudovaného pískovce: statického modulu pružnosti, lomové houževnatosti, houževnatostia specifické lomové energie. The aim of this paper is a characterization ofsandstone from Božanov quarry near Broumov, Czech Republic,by means of the pilot fracture tests. Five drill-core test specimens withnominal diameter of 50mm and lengths of 100 and 125mmwere provided by an initial chevron type notch. Specimens were loaded in the configuration of the three-point bending as a displacement driven experimentusing LabTest 6.250 equipment in the laboratory of the Institute of Building Testing, Faculty of Civil Engineering, Brno University of Technology. The load versus displacement diagrams were used to quantify the basic mechanical fracture parameters of the studied sandstone: modulus of elasticity, fracture toughness, toughness, and specific fracture energy. Keywords: Božanov sandstone; drill-core specimen; chevron notch; fracture test; load–displacement diagram Fulltext is available at external website.
Charakterizace Božanského pískovce: pilotní lomové testy

Cíl příspěvku představuje charakterizacipískovce zlomu Božanov u Broumova,Česká republika,pomocí pilotních lomových testů. Pět zkušebních těles z jádrových vývrtůnominálního průměru ...

Kumpová, I.; Rozsypalová, I.; Vavro, Leona; Vavro, Martin; Keršner, Z.
Ústav geoniky, 2020

Shaanxi 2019 - do nitra masivu
Motyčka, Z.; Filippi, Michal
2020 - Czech
Keywords: caves; exploration; Xioananhai; Hanzhong; China Available at various institutes of the ASCR
Shaanxi 2019 - do nitra masivu

Motyčka, Z.; Filippi, Michal
Geologický ústav, 2020

An experimental investigation of yield surfaces anisotropies
Štefan, Jan; Parma, Slavomír; Marek, René; Plešek, Jiří; Feigenbaum, H. P.; Ciocanel, C.
2020 - English
This contribution is dedicated to a rigorous experimental procedure for evaluation of yield surfaces of common metallic materials. This yield surface tracing procedure employs thin-walled tubular specimens to identify individual yield points of the material under arbitrary combinations of axial load and torque. A yield point is identified on the basis of a prescribed threshold for the effective plastic strain that is being continuously and fully automatically evaluated throughout the test. The experimental results generated with this tracing method are promising, leading to shapes of the yield surfaces conform with the von Mises criterion. The proposed methodology can effectively capture the YS shape. Keywords: experimental mechanics; yield surface; directional distortional hardening; metallic materials Available at various institutes of the ASCR
An experimental investigation of yield surfaces anisotropies

This contribution is dedicated to a rigorous experimental procedure for evaluation of yield surfaces of common metallic materials. This yield surface tracing procedure employs thin-walled tubular ...

Štefan, Jan; Parma, Slavomír; Marek, René; Plešek, Jiří; Feigenbaum, H. P.; Ciocanel, C.
Ústav termomechaniky, 2020

Random response of a dynamic system under polynomial of a white noise
Náprstek, Jiří; Fischer, Cyril
2020 - English
Many types of external additive random excitation of dynamic systems admit to be modelled as a combination of powers of a Gaussian noise. Such a type of excitation produces a non-Gaussian response even if the dynamic system is linear and the excitation is additive only. Although the excitation as a whole is non-Gaussian, the problem can be transformed into the form of a linear system with an additive and multiplicative white noise excitation which _nally produces a non-Gaussian response. The general method of transformation, the respective FPK equation, basic stochastic moments of the response, and a demonstrative example are discussed. Keywords: non-Gaussian excitation; nonlinear filtering; Kronecker algebra Available at various institutes of the ASCR
Random response of a dynamic system under polynomial of a white noise

Many types of external additive random excitation of dynamic systems admit to be modelled as a combination of powers of a Gaussian noise. Such a type of excitation produces a non-Gaussian response ...

Náprstek, Jiří; Fischer, Cyril
Ústav teoretické a aplikované mechaniky, 2020

Rukopis lokátorů - rozdíly v triangulaci
Loits, André; Drdácký, Tomáš; Buzek, Jaroslav; Zadražil, Tomáš
2020 - Czech
Převážná většina současných evropských měst má svůj počátek v období středověku. Na našem území většina měst vznikla od počátku 12. století do poloviny 14. století za doby vlády posledních Přemyslovců. Městské půdorysy jsou originální, a přestože je složité je vizuálně na první pohled porovnat, vykazuje jejich zdánlivá různorodost určitá pravidla a systém. Toto zjištění bylo ověřeno analýzou 29 českých a moravských měst. Příspěvek představuje výsledky rozboru vybraných měst. Při zakládání měst hrál zásadní roli lokátor, pověřený tehdejším investorem zorganizovat osídlení nové lokace. Vzhledem k počtu a těsnému sledu zakládaných měst je pravděpodobné, že města byla vyměřována zkušenými geometry, s teoretickými i praktickými znalostmi geometrie. Složitost úkolu a zároveň doložený fakt, že v rozmezí několika desetiletí vzniklo velké množství měst vede k závěru, že existoval prověřený, do jisté míry rutinní přístup k lokaci, který znamenal jistotu úspěšného vyměření a zrod fungujícího města. Příspěvek představuje rozdílné postupy vyměření půdorysné osnovy měst ve dvou režimech triangulace a jim odpovídajícím čtyřem systémům výchozích základních stanovisek, ze kterých mohlo být město a jeho ohrazení vytyčeno. Práce volně navazuje na text Triangulated medieval cities, publikovaný na konferenci Architektura v perspektivě v roce 2017 a shrnuje výsledky čtyřletého výzkumu. The vast majority of contemporary European cities have their origins in the Middle Ages. ln our territory, most towns were founded from the beginning of the 12th century to the middle of the 14th century during the reign of the last Přemyslids. Urban city layouts are original, and although it is difficult to visually compare them at first glance, their apparent diversity shows certain rules and systems. This finding was verified by an analysis of 29 Czech and Moravian cities. The paper presents the results of the analysis of selected cities. The locator, commissioned by the then investor to organize the settlement of the new location, played a crucial role in the founding of the towns. Due to the number and close sequence of founded cities, it is probable that the cities were measured by experienced surveyors, with theoretical and practical knowledge of geometry. The complexity of the task, as well as the proven fact that a large number of cities have emerged over several decades, leads to the conclusion that there was a proven, somewhat routine approach to the site, which ensured certainty in the survey and the birth of a functioning city. The paper presents identified types of procedures for surveying the city layout in two modes of triangulation and corresponding four systems of initial base stations, from which the city and its boarder was delineated. The work loosely follows the text Triangulated medieval cities, published at the conference Architecture in Perspective in 2017 and summarizes the results of four years of research work. Keywords: historical cities; location; medieval triangulation; urban type; groma Available at various institutes of the ASCR
Rukopis lokátorů - rozdíly v triangulaci

Převážná většina současných evropských měst má svůj počátek v období středověku. Na našem území většina měst vznikla od počátku 12. století do poloviny 14. století za doby vlády posledních ...

Loits, André; Drdácký, Tomáš; Buzek, Jaroslav; Zadražil, Tomáš
Ústav teoretické a aplikované mechaniky, 2020

Bivariate Geometric Distribution and Competing Risks: Statistical Analysis and Application
Volf, Petr
2020 - English
The contribution studies the statistical model for discrete time two-variate duration (time-to-event) data. The analysis is complicated by partial data observation caused either by the right-side censoring or by the presence of dependent competing events. The case is modeled and analyzed with the aid of a two-variate geometric distribution. The model identifiability is discussed and it is shown that the model is not identifiable without proper additional assumptions. The method of analysis is illustrated both on artificially generated\nexample and on real unemployment data. Keywords: bivariate geometric distribution; competing risks; unemployment data Fulltext is available at external website.
Bivariate Geometric Distribution and Competing Risks: Statistical Analysis and Application

The contribution studies the statistical model for discrete time two-variate duration (time-to-event) data. The analysis is complicated by partial data observation caused either by the right-side ...

Volf, Petr
Ústav teorie informace a automatizace, 2020

Modification of the Algebraic Transition Model for Wall Roughness Effect Including a Rough Strip
Straka, P.; Příhoda, Jaromír
2020 - English
The contribution deals with the simulation of the laminar/turbulent transition on a rough wall. The algebraic transition model taking into account wall roughness according to Straka and Příhoda [8] was further extended for the effect of short rough strip near the leading edge. The proposed correlation was tested by means of incompressible flow over a flat plate covered by sand paper and around the NACA 0012 airfoil with a rough strip near the leading edge. The agreement with experiments is appropriate nevertheless the applicability of the correlation is limited due to the lack of relevant experimental results. Keywords: bypass-transition; wall roughness; rough strip Fulltext is available at external website.
Modification of the Algebraic Transition Model for Wall Roughness Effect Including a Rough Strip

The contribution deals with the simulation of the laminar/turbulent transition on a rough wall. The algebraic transition model taking into account wall roughness according to Straka and Příhoda [8] ...

Straka, P.; Příhoda, Jaromír
Ústav termomechaniky, 2020

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