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Room temperature ethanol detection using carbon materials
Kočí, Michal
2023 - anglický
Allotropic forms of carbon, in particular graphene oxide (GO) or nanocrystalline diamond (NCD), attracted the attention of many research groups due to their unique electronic structures and extraordinary physical and chemical properties, preferable for many different applications, including sensor devices. This work focuses on responses of various sensing layers (NCD with hydrogen termination (H-NCD), graphene oxide (GO), reduced graphene oxide (rGO), thiol-functionalized graphene oxide (GO-SH) and their hybrid structures to ethanol vapor with concentrations up to 100 ppm in synthetic air at room temperature. The measured parameters of the tested sensors, especially stability, reproducibility and regeneration, are compared and critically evaluated. The high sensitivity of tested sensors achieved at room temperature makes them very promising for monitoring ethanol vapor as well as other volatile substances (e.g., isopropyl-alcohol or acetone).
Klíčová slova:
gas sensor; nanocrystalline diamond (NCD); graphene oxide (GO); reduced graphene oxide (rGO); thiol-functionalized graphene oxide (GO-SH)
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Room temperature ethanol detection using carbon materials
Allotropic forms of carbon, in particular graphene oxide (GO) or nanocrystalline diamond (NCD), attracted the attention of many research groups due to their unique electronic structures and ...
Dynamics of Machines and Mechanical Systems with Interactions, DYMAMESI 2023
Zolotarev, Igor; Pešek, Luděk; Kozień, M. S.
2023 - anglický
The aim of the DYMAMESI is to facilitate the exchange of up to date information and knowledge among specialists in structural and multibody dynamics, in coupled interacting systems as aero-elasticity, hydro-elasticity, biomechanics, systems with feedbacks and mechatronics. The colloquium DYMAMESI 2021 is cofunded by the Strategy AV21 initiative of the Czech Academy of Sciences of the Czech Republic, and in 2021 will be hosted by Cracow University of Technology, Institute of Applied Mechanics, Section of Dynamics of Systems.
Klíčová slova:
dynamics; vibrations of mechanical systems; vibrodiagnostics; energy transformations
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Dynamics of Machines and Mechanical Systems with Interactions, DYMAMESI 2023
The aim of the DYMAMESI is to facilitate the exchange of up to date information and knowledge among specialists in structural and multibody dynamics, in coupled interacting systems as aero-elasticity, ...
On the structure and values of betweenness centrality in dense betweenness-uniform graphs
Ghanbari, B.; Hartman, David; Jelínek, V.; Pokorná, Aneta; Šámal, R.; Valtr, P.
2023 - anglický
Betweenness centrality is a network centrality measure based on the amount of shortest paths passing through a given vertex. A graph is betweenness-uniform (BUG)if all vertices have an equal value of betweenness centrality. In this contribution, we focus on betweenness-uniform graphs with betweenness centrality below one. We disprove a conjecture about the existence of a BUG with betweenness value α for any rational numberαfrom the interval (3/4,∞) by showing that only very few betweenness centrality values below 6/7 are attained for at least one BUG. Furthermore, among graphs with diameter at least three, there are no betweenness-uniform graphs with a betweenness centrality smaller than one. In graphs of smaller diameter, the same can be shown under a uniformity condition on the components of the complement.
Klíčová slova:
betweenness; graphs
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
On the structure and values of betweenness centrality in dense betweenness-uniform graphs
Betweenness centrality is a network centrality measure based on the amount of shortest paths passing through a given vertex. A graph is betweenness-uniform (BUG)if all vertices have an equal value of ...
Adaptation of methods for cyclo-stationary processes for noisy structural health data
Fischer, Cyril; Bayer, Jan; Náprstek, Jiří; Urushadze, Shota
2023 - anglický
In structural health analysis, various techniques, including indirect measurement via monitoring vehicles, often yield data with significant randomness and insufficient frequency separation. Conversely, the desired attributes under scrutiny are periodic in nature. Thus, methodologies designed to identify cyclo-stationary properties within noisy data can be adapted for such scenarios, assuming an adequate length of the recorded data.
Klíčová slova:
data analysis; cyclo-stationary processes; structural health monitoring
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Adaptation of methods for cyclo-stationary processes for noisy structural health data
In structural health analysis, various techniques, including indirect measurement via monitoring vehicles, often yield data with significant randomness and insufficient frequency separation. ...
Consistency of mathematical and experimental model of the autoparametric system
Fischer, Cyril; Náprstek, Jiří
2023 - anglický
This paper presents a long-overdue comparison of data obtained from experimental investigation of a spherical vibration absorber with the results of two mathematical models of the motion of a heavy sphere in a spherical surface. It shows that the danger posed by the potentially unstable self-parametric nature of the mathematical system is not too great in the case of realistic configurations, and that the values of the parameters describing the realistic structures remain within intervals corresponding to the stable behaviour of the absorber.
Klíčová slova:
vibration absorber; rolling sphere; spherical surface; autoparametric system; structural health monitoring
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Consistency of mathematical and experimental model of the autoparametric system
This paper presents a long-overdue comparison of data obtained from experimental investigation of a spherical vibration absorber with the results of two mathematical models of the motion of a heavy ...
Professional survey forecasts and expectations in DSGE models
Rychalovska, Y.; Slobodyan, Sergey; Wouters, R.
2023 - anglický
In this paper, we demonstrate the usefulness of survey data for macroeconomic analysis and propose a strategy to integrate and efficiently utilize information from surveys in the DSGE setup. We extend the set of observable variables to include the data on consumption, investment, output, and inflation expectations, as measured by the Survey of Professional Forecasters (SPF). By doing so, we aim to discipline the dynamics of model-based expectations and evaluate alternative belief models. Our approach to exploit the timely information from surveys is based on re-specification of structural shocks into persistent and transitory components. Due to the SPF, we are able to improve identification of fundamental shocks and predictive power of the model by separating the sources of low and high frequency volatility. Furthermore, we show that models with an imperfectly-rational expectation formation mechanism based on Adaptive Learning (AL) can reduce important limitations implied by the Rational Expectation (RE) hypothesis. More specifically, our models based on belief updating can better capture macroeconomic trend shifts and, as a result, achieve superior long-term predictions. In addition, the AL mechanism can produce realistic time variation in the transmission of shocks and perceived macro-economic volatility, which allows the model to better explain the investment dynamics. Finally, AL models, which relax the RE constraint of internal consistency between the agents’ and model forecasts, can reproduce the main features of agents’ predictions in line with SPF evidence and, at the same time, can generate improved model forecasts, thus diminishing possible inefficiencies present in surveys.
Klíčová slova:
expectations; survey data; adaptive learning
Dokument je dostupný na externích webových stránkách.
Professional survey forecasts and expectations in DSGE models
In this paper, we demonstrate the usefulness of survey data for macroeconomic analysis and propose a strategy to integrate and efficiently utilize information from surveys in the DSGE setup. We extend ...
Gender gap in reported childcare preferences among parents
Pertold, Filip; Sinani, S.; Šoltés, M.
2023 - anglický
The child penalty explains the majority of gender employment and wage gaps, however, less is known about the factors driving the child penalty itself. In this paper, we study the gender gap in childcare preferences as a potential factor that contributes to the child penalty. We surveyed Czech parents and elicited the minimal compensation they would require to stay home to care for a child. Mothers require less compensation for childcare than fathers. The estimated gender gap in childcare preferences is CZK 2,500 monthly, 7.6% of the median female wage, and cannot be explained by differences in labor market opportunities or prosocial motives to care for a family member. We further document widespread misperception of fathers’ preferences, as respondents incorrectly expect fathers to require less to care for a child than to care for an elderly parent.\n
Klíčová slova:
childcare; gender wage gap; gender employment gap
Dokument je dostupný na externích webových stránkách.
Gender gap in reported childcare preferences among parents
The child penalty explains the majority of gender employment and wage gaps, however, less is known about the factors driving the child penalty itself. In this paper, we study the gender gap in ...
Comparison of finite element simulation of tungsten nanoindentation with Berkovich and conical indenter
Fiala, L.; Ballo, I.; Kovář, J.; Fuis, Vladimír
2023 - anglický
Finite Element Method (FEM) was used to study the difference between using Berkovich and conical indenters in nanoindentation test of tungsten specimen. The study was aimed to determine the\nmodulus of elasticity of a tested specimen and how it changes with different indenter. The FEM analysis also revealed that the modulus of elasticity was sensitive to the dimensions of both specimen and the indenter for which were made several numerical calculations with different dimensions.
Klíčová slova:
nanoindentation; FEM; Berkovich indenter; conical indenter; tungsten
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Comparison of finite element simulation of tungsten nanoindentation with Berkovich and conical indenter
Finite Element Method (FEM) was used to study the difference between using Berkovich and conical indenters in nanoindentation test of tungsten specimen. The study was aimed to determine the\nmodulus ...
Mechanical properties of basalt: a study on compressive loading at different strain rates using SHPB
Falta, J.; Krčmářová, N.; Fíla, T.; Vavro, Martin; Vavro, Leona
2023 - anglický
This article focuses on the mechanical properties of basalt in compressive loading at different strain-rates. The study employs advanced instrumentation for the evaluation of the results in dynamic conditions, while standard uni-axial loading device is used for evaluation in quasi-static conditions. Basalt specimens were subjected to four different loading-rates from 200–600 s−1 on which the stress-strain dependence was evaluated together with DIC analysis of crack initiation and disintegration process. Understanding the mechanical properties of basalt can provide insights for engineers and designers in creating structures that are durable and able to withstand different loading conditions. The findings of this study can have implications for a wide range of industries, including aerospace, automotive, and construction, among others.
Klíčová slova:
SHPB; basalt; compressive loading; dynamic loading
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Mechanical properties of basalt: a study on compressive loading at different strain rates using SHPB
This article focuses on the mechanical properties of basalt in compressive loading at different strain-rates. The study employs advanced instrumentation for the evaluation of the results in dynamic ...
Asynchronous time integration while achieving zero interface energy
Dvořák, Radim; Kolman, Radek; Falta, J.; Neühauserová, M.
2023 - anglický
This contribution deals with an asynchronous direct time integration of the finite-element model. The proposed method is applied to the phenomenon of wave propagation through an elastic linear continuum. The numerical model is partitioned into individual subdomains using the domain decomposition method by means of localized Lagrange multipliers. For each subdomain, different time discretizations are used. No restrictions for relation between subdomain’s time steps are imposed. The coupling of the subdomains is forced by an acceleration continuity condition. Additionally, we use the a posteriori technique to also provide the displacement and velocity continuity at the interfaces, and hence we obtain exact continuity of all three kinematic fields. The proposed method is experimentally validated using the modified SHPB (split Hopkinson pressure bar) setup.
Klíčová slova:
finite element method; direct time integration; asynchronous integration; domain decomposition; localized lagrange multipliers
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Asynchronous time integration while achieving zero interface energy
This contribution deals with an asynchronous direct time integration of the finite-element model. The proposed method is applied to the phenomenon of wave propagation through an elastic linear ...
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