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Two Composition Operators for Belief Functions Revisited
Jiroušek, Radim; Kratochvíl, Václav; Shenoy, P. P.
2022 - anglický
In probability theory, compositional models are as powerful as Bayesian networks. However, the relation between belief-function graphical models and the corresponding compositional models is much more complicated due to several reasons. One of them is that there are two composition operators for belief functions. This paper deals with their main properties and presents sufficient conditions under which they yield the same results.
Klíčová slova:
probability theory; Bayesian networks; belief functions
Dokument je dostupný na externích webových stránkách.
Two Composition Operators for Belief Functions Revisited
In probability theory, compositional models are as powerful as Bayesian networks. However, the relation between belief-function graphical models and the corresponding compositional models is much more ...
Modeling COVID Pandemics: Strengths and Weaknesses of Epidemic Models
Šmíd, Martin
2022 - anglický
We generally discuss modeling the present COVID pandemics. We argue that useful models have to be simple in the first case, yet their uncertainty has to be handled properly. In order to study circumstances of the upcoming wave of infection,\nwe construct a simple stochastic model and present predictions it gives. We conclude that the autumn wave is most likely unavoidable and suggest concentrating to mitigation.
Klíčová slova:
COVID; Epidemic Models; stochastic model
Dokument je dostupný na externích webových stránkách.
Modeling COVID Pandemics: Strengths and Weaknesses of Epidemic Models
We generally discuss modeling the present COVID pandemics. We argue that useful models have to be simple in the first case, yet their uncertainty has to be handled properly. In order to study ...
Analysis of Impact of Covariates Entering Stochastic Optimization Problem
Volf, Petr
2022 - anglický
In the contribution we study consequences of imperfect information to precision of stochastic optimization solution. In particular, it is assumed that the characteristics of optimization problem are influenced by a set of covariates. This dependence is described via a regression model. Hence, the uncertainty is then caused by statistical estimation of regression parameters. The contribution will analyze several regression model cases, together with their application. Precision of results will be explored, both theoretically as well as with the aid of simulations.
Klíčová slova:
stochastic optimization; regression model; statistical estimation
Dokument je dostupný na externích webových stránkách.
Analysis of Impact of Covariates Entering Stochastic Optimization Problem
In the contribution we study consequences of imperfect information to precision of stochastic optimization solution. In particular, it is assumed that the characteristics of optimization problem are ...
Hybrid evaluation of the industrial global impact on Mexican aquifers under uncertain criteria evaluations
Flores Casamayor, H.; Carpitella, Silvia; Izquierdo, J.; Mora-Rodríguez, J.; Delgado-Galván, X.
2022 - anglický
The present paper proposes an integrated methodological approach to address the problem of managing five aquifers of Guanajuato state, Mexico, according to such relevant criteria as environmental, social, economic and hydrological aspects. The goal of this research consists in formalizing a structured framework to first evaluate the various degrees of importance of criteria and to secondly get a classification of aquifers by minimizing uncertainty of evaluations. To such an aim, the Analytic Hierarchy Process (AHP) is used for calculating the vector of criteria weights, while the Fuzzy Logic (FL) theory supports in deriving quantitative evaluations of aquifers under each selected criterion. The Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) is then proposed to formalize the final ranking of aquifers, something that will be helpful to understand which alternative matches all the differently weighted criteria in the most suitable way at a practical level. In such a way, getting a comprehensive and strategic overview about the problem of interest will be possible.
Klíčová slova:
Analytic Hierarchy Process (AHP); Fuzzy Logic (FL) theory; Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS)
Dokument je dostupný na externích webových stránkách.
Hybrid evaluation of the industrial global impact on Mexican aquifers under uncertain criteria evaluations
The present paper proposes an integrated methodological approach to address the problem of managing five aquifers of Guanajuato state, Mexico, according to such relevant criteria as environmental, ...
Wake Behind a Cylinder: An Overview of Spatio-Temporal Aspects
Uruba, Václav
2022 - anglický
A circular cylinder in crossflow is subjected to the overview study from the point of view spatial and temporal characteristics. It represents itself a typical engineering problem, appearing in practice frequently in various forms. In fluid mechanics, this case is considered to be a typical canonical case, with relatively simple and straightforward definition, but complex and dynamical flow topology. The typical dynamics is characterized by quasi-periodic behavior called von Kármán – Bénard vortex street with a typical frequency expressed in dimensionless number called Strouhal number. The wake flow structure is considered to be characterized by a single frequency and 2D topology, homogeneous along the cylinder axis, very often. The presented paper concentrates on differences between this commonly accepted model and physical reality. Both temporal and spatial aspects of the flow in the wake behind a cylinder are to be addressed. The turbulent subcritical wake characterized by Reynolds number about 5 thousand will be considered, as this situation is a typical case in mechanical engineering applications.
Klíčová slova:
circular cylinder; wake; vortex; dynamics; 3D structure
Dokument je dostupný na externích webových stránkách.
Wake Behind a Cylinder: An Overview of Spatio-Temporal Aspects
A circular cylinder in crossflow is subjected to the overview study from the point of view spatial and temporal characteristics. It represents itself a typical engineering problem, appearing in ...
On a class of biped underactuated robot models with upper body: Sensitivity analysis of the walking performance
Papáček, Štěpán; Polach, P.; Prokýšek, R.; Anderle, Milan
2022 - anglický
Biped underactuated robots with an upper body (being a torso) form a subclass of legged robots. This study deals with the walking performance of such class of legged robot models and has been motivated by the need to implement of the previously developed sensor and control algorithms for the real-time movement of the laboratory walking robot, designed and built at the Department of Control Theory of the Institute of Information Theory and Automation (UTIA) of the Czech Academy of Sciences, see Fig. 1 (left). A detailed description of this underactuated walking-like mechanical system (called further UTIA Walking Robot – UWR) is provided in [2] and [5]. The simplest underactuated walking robot hypothetically able to walk is the so-called Compass gait biped walker, alternatively called the Acrobot, see Fig. 1 (right). For a review of underactuated mechanical systems, i.e. systems with fewer actuators than degrees of freedom, which encounter many applications in different fields (e.g., in robotics, in aeronautical and spatial systems, in marine and underwater systems, and in-flexible and mobile systems), see [3]. As follows, we examine the walking performance of parametrized models for different walking regimes and different values of model parameters. More specifically, the sensitivity analysis (i.e., parameter study) of the walking performance with respect to certain design variables (model parameters) is carried out using the software package alaska/MultibodyDynamics. The main attention is attracted to the role of the upper body mass m3 and position lc3, see Fig. 1 (right). Last but not least, having surveyed the mechanics of planar biped robots, our subsequent goal is the analysis of a 3D biped model where lateral balance is either controlled, suppressed or compensated.
Klíčová slova:
Walking robot; ALASCA; Simulation
Dokument je dostupný na externích webových stránkách.
On a class of biped underactuated robot models with upper body: Sensitivity analysis of the walking performance
Biped underactuated robots with an upper body (being a torso) form a subclass of legged robots. This study deals with the walking performance of such class of legged robot models and has been ...
Development and measurement of gas sensors for room temperature applications
Kočí, Michal
2022 - anglický
Gas sensing properties of a nanocrystalline diamond with a hydrogen-terminated surface (H-terminated NCD) and a molybdenum disulphide (MoS2) are investigated as conductivity sensors with built-in interdigital metal electrode structures. The H-terminated NCD was prepared by plasma-enhanced chemical vapour deposition (PECVD), and the MoS2 by a carbide-free one-zone sulfurization method. The sensor's responses were measured for oxidizing (NO2) and reducing (NH3) gases by the same equipment and setup. The parameters of the tested sensors are compared and critically evaluated. Advantageously, the MoS2/H-terminated NCD heterostructure enhances the gas sensing response at room temperature compared to the H-terminated NCD and MoS2 layers.
Klíčová slova:
gas sensor; nanocrystalline diamond (NCD); transition metal dichalcogenide (TMD)
Dokument je dostupný na externích webových stránkách.
Development and measurement of gas sensors for room temperature applications
Gas sensing properties of a nanocrystalline diamond with a hydrogen-terminated surface (H-terminated NCD) and a molybdenum disulphide (MoS2) are investigated as conductivity sensors with built-in ...
Spectrometry of neutron field based on p(20)+Be source reaction
Kozic, Ján; Štefánik, Milan
2022 - anglický
The research deals with a spectrometry of neutron field based on the p(20)+Be source reaction. The p(20)+Be interaction stands for a nuclear reaction where protons accelerated to energy of 20 MeV bombard Be target. Produced neutron field has broad energy distribution up to 18 MeV. The research was carried out at the Nuclear Physics Institute of the Czech Academy of Sciences and was motivated by extension of experimental possibilities of the NG-2 target station. To determine the neutron spectrum, the activation foil technique was used. During the experiment, ten activation foils were irradiated. Activated foils were measured using the HPGe detector to determine the reaction rates of observed reactions. The neutron field was simulated in the MCNPX code, and the simulation served as a priori information for the unfolding of the neutron spectrum in the SAND-II code. A determined neutron spectrum is essential for various experiments, e.g., material research, measurements of nuclear data, etc.
Klíčová slova:
Accelerator-driven neutron source; activation foil technique; beryllium target station NG-2; neutron energy spectrum; SAND-II
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Spectrometry of neutron field based on p(20)+Be source reaction
The research deals with a spectrometry of neutron field based on the p(20)+Be source reaction. The p(20)+Be interaction stands for a nuclear reaction where protons accelerated to energy of 20 MeV ...
Aerodynamic interference forces acting on two square prisms in a model atmospheric boundary layer
Macháček, Michael; Lo, Y. L.; Máca, J.
2022 - anglický
The presented experimental analysis focuses on the definition of interference factors for aerodynamic forces acting on two square prisms depending on their relative position. Both prisms used had the same dimensions and a height to width ratio of 6 - this ratio is relatively common in high-rise buildings. The experiment was performed in a wind tunnel with a model atmospheric boundary layer, which represented a dense urban area. The forces acting at the base of one of the buildings were measured, and by moving the other building it was possible to measure 204 mutual configurations, i.e., 204 interference positions. In all positions, the windward facades of the small-area model were placed perpendicular to the direction of the incoming flow. This created a detailed map of the interference effect on a wind-loaded pair of buildings. The results show a significant effect of the relative position of buildings on wind loads. A significant increase in\nload occurred due to the proximity of buildings. Due to the interference effect, wind load fluctuations can increase by up to 28% and average values by up to 36%.
Klíčová slova:
interference effect; two square prisms; wind tunnel experiments; turbulent boundary layer
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Aerodynamic interference forces acting on two square prisms in a model atmospheric boundary layer
The presented experimental analysis focuses on the definition of interference factors for aerodynamic forces acting on two square prisms depending on their relative position. Both prisms used had the ...
Tomographic investigation of the sandstone fracture toughness
Vavřík, Daniel; Beneš, Pavel; Fíla, Tomáš; Koudelka_ml., Petr; Kumpová, Ivana; Vavro, Martin
2022 - anglický
It is well known that the measured values of the fracture toughness of quasi brittle materials are influenced by material heterogeneity, dimensions, boundary conditions, and unequal tension and compression properties. Standard testing methods supposing isotropic material, in contrary the quasi-brittle materials differ from this theoretical expectation, therefore this approach may fail. The authors present Local Fracture Toughness Testing (LFTT) method to overcome this obstacle. LFFT based on a complex methodology using a series of tomographic reconstructions recorded during specimen loading is calculated independently of the outside boundary conditions.
Klíčová slova:
fracture process zone; crack path; quasi-brittle material; X-Ray computed tomography; four-point bending test
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Tomographic investigation of the sandstone fracture toughness
It is well known that the measured values of the fracture toughness of quasi brittle materials are influenced by material heterogeneity, dimensions, boundary conditions, and unequal tension and ...
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