Ano (2101)
Počet nalezených dokumentů:
2101
Publikováno od
do
Some Robust Approaches to Reducing the Complexity of Economic Data
Kalina, Jan
2023 - anglický
The recent advent of complex (and potentially big) data in economics requires modern and effective tools for their analysis including tools for reducing the dimensionality (complexity) of the given data. This paper starts with recalling the importance of Big Data in economics and with characterizing the main categories of dimension reduction techniques. While there have already been numerous techniques for dimensionality reduction available, this work is interested in methods that are robust to the presence of outlying measurements (outliers) in the economic data. Particularly, methods based on implicit weighting assigned to individual observations are developed in this paper. As the main contribution, this paper proposes three novel robust methods of dimension reduction. One method is a dimension reduction within a robust regularized linear regression, namely a sparse version of the least weighted squares estimator. The other two methods are robust versions of feature extraction methods popular in econometrics: robust principal component analysis and robust factor analysis.
Klíčová slova:
dimensionality reduction; Big Data; variable selection; robustness; sparsity
Dokument je dostupný na externích webových stránkách.
Some Robust Approaches to Reducing the Complexity of Economic Data
The recent advent of complex (and potentially big) data in economics requires modern and effective tools for their analysis including tools for reducing the dimensionality (complexity) of the given ...
The 2022 Election in the United States: Reliability of a Linear Regression Model
Kalina, Jan; Vidnerová, Petra; Večeř, M.
2023 - anglický
In this paper, the 2022 United States election to the House of Representatives is analyzed by means of a linear regression model. After the election process is explained, the popular vote is modeled as a response of 8 predictors (demographic characteristics) on the state-wide level. The main focus is paid to verifying the reliability of two obtained regression models, namely the full model with all predictors and the most relevant submodel found by hypothesis testing (with 4 relevant predictors). Individual topics related to assessing reliability that are used in this study include confidence intervals for predictions, multicollinearity, and also outlier detection. While the predictions in the submodel that includes only relevant predictors are very similar to those in the full model, it turns out that the submodel has better reliability properties compared to the full model, especially in terms of narrower confidence intervals for the values of the popular vote.
Klíčová slova:
elections results; electoral demography; linear regression; reliability; variability
Dokument je dostupný na externích webových stránkách.
The 2022 Election in the United States: Reliability of a Linear Regression Model
In this paper, the 2022 United States election to the House of Representatives is analyzed by means of a linear regression model. After the election process is explained, the popular vote is modeled ...
Growth of orbital resonances around a black hole surrounded by matter
Stratený, Michal; Lukes-Gerakopoulos, Georgios
2023 - anglický
This work studies the dynamics of geodesic motion within a curved spacetime around a Schwarzschild black hole, perturbed by a gravitational field of a far axisymmetric distribution of mass enclosing the system. This spacetime can serve as a versatile model for a diverse range of astrophysical scenarios and, in particular, for extreme mass ratio inspirals as in our work. We show that the system is non-integrable by employing Poincaré surface of section and rotation numbers. By utilising the rotation numbers, the widths of resonances are calculated, which are then used in establishing the relation between the underlying perturbation parameter driving the system from integrability and the quadrupole parameter characterising the perturbed metric. This relation allows us to estimate the phase shift caused by the resonance during an inspiral.
Klíčová slova:
geodesic motion; black holes; chaos
Dokument je dostupný na externích webových stránkách.
Growth of orbital resonances around a black hole surrounded by matter
This work studies the dynamics of geodesic motion within a curved spacetime around a Schwarzschild black hole, perturbed by a gravitational field of a far axisymmetric distribution of mass enclosing ...
Risk Assessment on Geodiversity Sites
Kubalíková, Lucie; Nováková, Eva; Kuda, František; Kirchner, Karel; Bajer, A.; Balková, M.
2023 - anglický
Geoconservation is an action of conserving and enhancing geological, geomorphological, hydrological and soil features and processes. Particular geoconservation measures are very often applied on the site-level to protect important geodiversity sites. Nevertheless, despite established legal protection and related geoconservation activities, threats to geodiversity sites related to the multiple use and human society demands can arise and reaching a compromise can be difficult. In this contribution, a two-level threat assessment is applied and discussed. The first level of threat assessment is based on the already used criteria within geosite/geomorphosite concept. The second level of threat assessment is represented by Risk Assessment Matrix, which may be considered a useful tool providing a complex view on the threats to geodiversity sites. The methods are applied on two different sites and their advantages and limits are discussed. Based on the assessment, specific management proposals may be implemented in order to balance conservation needs and demands resulting from human activities related to the sites.
Klíčová slova:
geoconservation; risk assessment matrix; degradation risk; geosites; geomorphosites
Dokument je dostupný na externích webových stránkách.
Risk Assessment on Geodiversity Sites
Geoconservation is an action of conserving and enhancing geological, geomorphological, hydrological and soil features and processes. Particular geoconservation measures are very often applied on the ...
Ceramic protection of anti-corrosion layers of 3-glycidyloxypropyl-triethoxysilane on steel
Pokorný, P.; Janata, Marek; Brožek, Vlastimil
2023 - anglický
There are various variations on the problem of steel reinforcement bond strength in concrete. Along with geometrical considerations, corrosion performance of steels with varying chemical compositions in interaction with variable chemical compositions of concrete are crucial. One approach is to cover steel surfaces with organosilane compounds, which increases the reinforcement resistance to corrosion in both acidic and alkaline conditions but, on the other hand, may weaken the reinforcement bond strength on concrete. The issue is resolved by intentionally forming a thin-walled, highly adhering corundum layer that is highly porous and impregnated with 3-glycidyloxypropyltriethoxysilane. This procedure also includes testing the adhesion properties between the ceramic and the metal and the cement prior to conducting a corrosion test in a chloride environment.
Klíčová slova:
ceramic protection; 3-glycidyloxypropyl-triethoxysilane; steel
Dokument je dostupný na externích webových stránkách.
Ceramic protection of anti-corrosion layers of 3-glycidyloxypropyl-triethoxysilane on steel
There are various variations on the problem of steel reinforcement bond strength in concrete. Along with geometrical considerations, corrosion performance of steels with varying chemical compositions ...
Determination of the initial stress tensor from deformation of underground opening-theoretical background and applications
Malík, Josef; Kolcun, Alexej
2023 - anglický
In this paper a method for the detection of initial stress tensor is proposed. The method is based on measuring distances between some pairs of points located on the wall of underground opening in the excavation process. This methods is based on the solution of eighteen auxiliary problems in the theory of elasticity with force boundary conditions. The optimal location of the pairs of points on the wall of underground work is studied. The pairs must be located so that the condition number of a certain matrix has the minimal value, which guarantees a reliable estimation of initial stress tensor.
Klíčová slova:
initial stress tensor; first boundary value problem of the theory of elasticity; condition number of matrices
Dokument je dostupný na externích webových stránkách.
Determination of the initial stress tensor from deformation of underground opening-theoretical background and applications
In this paper a method for the detection of initial stress tensor is proposed. The method is based on measuring distances between some pairs of points located on the wall of underground opening in the ...
Dynamics of a cantilever beam with piezoelectric sensor: Finite element modeling
Cimrman, Robert; Kolman, Radek; Musil, Ladislav; Kotek, Vojtěch; Kylar, Jaromír
2023 - anglický
An elastodynamical model of a cantilever beam coupled with a piezoelectric sensor is introduced and its discretization using the finite element method is presented. The mathematical model includes additional terms that enforce the floating potential boundary condition for keeping a constant charge on an electrode of the sensor. The behaviour of the model is illustrated using a numerical example corresponding to an experimental setup, where vibrations of the beam and the potential on the sensor are measured.
Klíčová slova:
finite element method; piezo-electricity; floating potential; dynamic simulation
Dokument je dostupný na externích webových stránkách.
Dynamics of a cantilever beam with piezoelectric sensor: Finite element modeling
An elastodynamical model of a cantilever beam coupled with a piezoelectric sensor is introduced and its discretization using the finite element method is presented. The mathematical model includes ...
Good vs. Bad Volatility in Major Cryptocurrencies: The Dichotomy and Drivers of Connectedness
Šíla, Jan; Kočenda, Evžen; Kukačka, Jiří; Krištoufek, Ladislav
2023 - anglický
Cryptocurrencies exhibit unique statistical and dynamic properties compared to those of traditional financial assets, making the study of their volatility crucial for portfolio managers and traders. We investigate the volatility connectedness dynamics of a representative set of eight major crypto assets. Methodologically, we decompose the measured volatility into positive and negative components and employ the time-varying parameters vector autoregression (TVP-VAR) framework to show distinct dynamics associated with market booms and downturns. The results suggest that crypto connectedness reflects important events and exhibits more variable and cyclical dynamics than those of traditional financial markets. Periods of extremely high or low connectedness are clearly linked to specific events in the crypto market and macroeconomic or monetary history. Furthermore, existing asymmetry from good and bad volatility indicates that information about market downturns spills over substantially faster than news about comparable market surges. Overall, the connectedness dynamics are predominantly driven by fundamental crypto factors, while the asymmetry measure also depends on macro factors such as the VIX index and the expected inflation.
Klíčová slova:
Volatility; Dynamic connectedness; Asymmetric effects; Cryptocurrency
Dokument je dostupný na externích webových stránkách.
Good vs. Bad Volatility in Major Cryptocurrencies: The Dichotomy and Drivers of Connectedness
Cryptocurrencies exhibit unique statistical and dynamic properties compared to those of traditional financial assets, making the study of their volatility crucial for portfolio managers and traders. ...
Hydrolgoie malého povodí 2023
Hnilicová, Soňa; Tesař, Miroslav
2023 - český
Sborník obsahuje plné texty vědeckých článků. Příspěvky neprošly jazykovou kontrolou a za obsah odpovídají autoři článků. Články byly připraveny jako příspěvky pro konferenci „Hydrologie malého povodí 2023“ s tématickými okruhy: 1. Globální vlivy a změny v režimu vodních zdrojů v malém povodí; 2. Komplexní monitoring a bilance zásob vody v malých povodích; 3. Hydrologické extrémy (přívalové povodně; sucho – typy a hodnocení); 4. Vliv vegatačního krytu a způsobu využití povodí na vodní režim; 5. Transportní procesy v půdě a vliv hydrofobie povrchové vrstvy na ně; 6. Hydrologické modelování; nejistoty v hydrologickém modelování; 7. Látkové toky v malém povodí a eutrofizace povrchových vod; 8. Malá povodí v horský oblastech (usazené srážky, akumulace a tání sněhu, atd.); 9. Nové metody, techniky a přístrojové vybavení v hydrologii a hydroekologii.\n The book is a collection of scientific contributions to the Conference "Hydrology of small basins". The conference topics were: 1. Changes in the regime of water resources in small basins; 2. Complex monitoring a and water storage balance in small basins; 3. Hydrological extremes (flash floods, drought); 4. Effect of land use and land cover on water balance; 5. Hydrophobicity and transportation processes in soil; 6. Hydrological modelling und uncertainties; 7. Biogeochemical fluxes in a small watershed and eutrophication of surface waters; 8. Mountainous experimental small basins (deposited precipitation, snow regime, …); 9. New methods, techniques and instrumentation in hydrology and hydroecology.\n
Klíčová slova:
experimental hydrology; hydrological monitoring; subsurface hydrology; small basin; water balance; hydrological modelling
Dokument je dostupný na externích webových stránkách.
Hydrolgoie malého povodí 2023
Sborník obsahuje plné texty vědeckých článků. Příspěvky neprošly jazykovou kontrolou a za obsah odpovídají autoři článků. Články byly připraveny jako příspěvky pro konferenci „Hydrologie malého povodí ...
Hidden symmetry in turbulence and analytic study of shell models
Caggio, Matteo
2023 - anglický
This short communication concerns symmetries in developed turbulence and analytic study of shell models. However scale-invariance is broken due to the intermittency phenomenon, is possible to established a hidden self-similarity in turbulent flows. Using a shell model, the author in [18] (see also [19]) addressed the problem deriving a scaling symmetry for the inviscid equations. Here, first we discuss the analysis presented in [18], then, from the mathematical perspective, we propose an analytic study for the shell model with the presence of the viscous terms. This brief paper should be understood as an introductory note to this new scaling symmetry with implications for mathematical analysis [5].
Klíčová slova:
turbulence; scale-invariance symmetry; intermittency; shell-models
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Hidden symmetry in turbulence and analytic study of shell models
This short communication concerns symmetries in developed turbulence and analytic study of shell models. However scale-invariance is broken due to the intermittency phenomenon, is possible to ...
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