We effectively solve the class number one problem for a certain family Q(D)${\bf Q}(\sqrt D)$ (D∈F$(D\in {\cal F}$) of real quadratic fields, where F$ {\cal F}$ is an infinite subset of the set of ...odd positive fundamental discriminants. The set F${\cal F}$ contains the Yokoi discriminants n2+4$n^2+4$, so our result is a generalization of the solution of Yokoi's Conjecture. But this family may contain also infinitely many fields with comparatively larger fundamental units than the fields in the Yokoi family (it may be as large as log2D$\log ^2D$ instead of logD$\log D$). The proof is also a generalization of the proof of Yokoi's Conjecture.
The durability of fire-retardant materials used for wooden structures and wood-based products can be evaluated on small cut-out samples with the so-called Lindner test, which is a standard procedure ...in Hungary where 1 g of hexamethylene-tetramine is burnt under the wooden specimen and the mass loss is measured. For further spatial information about the burnt part of the samples, the specimens were CT scanned after the Lindner test. The goal was to evaluate if the charred part can be properly segmented in a CT image set and if the two measurements combined are precise enough to provide charring rate data. With the segmentation of the CT image sets, the burnt volumes could be separated properly in each case even when knots were present. Spruce sample provided the most consistent results regarding the mass loss/burnt volume. This is probably due to the uneven ring spacing and other inhomogeneities in the density of oak and ash.
Uncertainty in finite planes Biró, András; Lev, Vsevolod F.
Journal of functional analysis,
08/2021, Letnik:
281, Številka:
3
Journal Article
Recenzirano
We establish a number of uncertainty inequalities for the additive group of a finite affine plane, showing that for p prime, a nonzero function f:Fp2→C and its Fourier transform fˆ:Fp2ˆ→C cannot have ...small supports simultaneously. The “baseline” of our investigation is the well-known Meshulam's bound, which we sharpen, for the particular groups under consideration, taking into account not only the sizes of the support sets supp f and suppfˆ, but also their structure.
Our results imply in particular that, with some explicitly classified exceptions, one has |suppf||suppfˆ|≥3p(p−2); in comparison, the classical uncertainty inequality gives |suppf||suppfˆ|≥p2.
•Suggested new classification method for concrete aggregates based on fire resistance.•The classification system is based on Hummel test results evaluated with calculating fineness modulus ...changes.•This classification system could be a more economic solution in some cases, instead of testing concrete elements.
The quality of the natural stone aggregates change with each shipment and it greatly influences the fire-performance of the concrete. For this reason, it would be advantageous if there would be a classification system for aggregates for fire or fire-related temperatures. The classification of the aggregate itself instead of the concrete could be faster and more economical solution in the long run, it could prevent the need to deconstruct concrete based on 28-day test results in case of an insufficient aggregate. This study aims to provide preliminary measurements and conclusions for such a system based on the Hummel-tests after heat loading with supplementary tests such as scanning electron microscope and derivatograph to better understand the changes of the inner structure. For this study quartz, crushed andesite and crushed limestone were tested. The Hummel tests were evaluated based the changes of the grain size distribution and showed promising results, but further testing is required with more samples to calibrate and to confirm the usability of the method.
Let
$\unicodeSTIX{x1D6E4}\subseteq \operatorname{PSL}(2,\mathbf{R})$
be a finite-volume Fuchsian group. The hyperbolic circle problem is the estimation of the number of elements of the
...$\unicodeSTIX{x1D6E4}$
-orbit of
$z$
in a hyperbolic circle around
$w$
of radius
$R$
, where
$z$
and
$w$
are given points of the upper half plane and
$R$
is a large number. An estimate with error term
$\text{e}^{(2/3)R}$
is known, and this has not been improved for any group. Recently, Risager and Petridis proved that in the special case
$\unicodeSTIX{x1D6E4}=\operatorname{PSL}(2,\mathbf{Z})$
taking
$z=w$
and averaging over
$z$
in a certain way the error term can be improved to
$\text{e}^{(7/12+\unicodeSTIX{x1D716})R}$
. Here we show such an improvement for a general
$\unicodeSTIX{x1D6E4}$
; our error term is
$\text{e}^{(5/8+\unicodeSTIX{x1D716})R}$
(which is better than
$\text{e}^{(2/3)R}$
but weaker than the estimate of Risager and Petridis in the case
$\unicodeSTIX{x1D6E4}=\operatorname{PSL}(2,\mathbf{Z})$
). Our main tool is our generalization of the Selberg trace formula proved earlier.
Fire behaviour of hollow core slabs Hlavička, Viktor; Biró, András; Tóth, Brigitta ...
Construction & building materials,
01/2024, Letnik:
411
Journal Article
Recenzirano
Odprti dostop
The objective of our research was to develop an optimum concrete mix for fire resistance, that is usable for hollow core slab prefabrication. Small-scale and full-scale tests were done, and the ...results were used to calibrate a numerical model that can be used to determine the temperature and load capacity reduction of steel reinforcement. With the help of the calibrated model, the effects of geometric variables were examined. The thickness of the ridge between the cavities has no effect on the change in the maximum temperature of the protected side in the examined 30-minute range, but the minimum temperature decreased.
•The objective of our research was to develop an optimum concrete mix for fire resistance, that is usable for hollow core slab prefabrication.•We performed two tests. In the first test, the fire resistance of the slab is REI 60 for operational loads and REI 90 for industrial loads (max. 5 kN/m2). In the second test, the slab fire resistance at service load was REI 15.•During the research, we created a method with a spatial numerical thermal model (VEM analysis). We performed the numerical modelling of a 200 mm high hollow core slab.•We determined the excess heat input into the cavities and the temperature variation of the steel inserts with iteration method.•We are of the opinion that the fire resistance limit of this support cannot be solved by changing the concrete composition alone, therefore we propose to modify the geometry.
•Recommend using travertine as tiles and load bearing compressed structural elements.•Recommend using labradorite as load bearing compressed structural element.•Recommend using marble and granite if ...there is little chance of a fire.
In our research, stones were tested after exposing them to temperature load to get information about the changes in their properties and about the limits of applicability. The tested stones are types that are widely used as tiles in Hungary (granite, marble, travertine, labradorite).
Beside flexural strength, among our laboratory tests uniaxial compressive strength and tensile strength tests were carried out. The stone material was also examined with optical microscope and derivatograph as well.
Based on the experimental results the travertine is recommended for tiles and for load bearing compressed structural elements and the labradorite is recommended for load bearing compressed structural elements.
While studies of the formal adaptation of parliaments to the European Union (EU) have dominated legislative scholarship in the last two decades, there is a growing interest in the substantive impact ...of the EU on legislative production and parliamentary behaviour. We contribute to this research agenda by exploring the effects of Europeanisation on the national parliament of one democratically backsliding EU member state, Hungary. Comparing periods marked by Europhile and Eurosceptic parliamentary majorities between 2004 and 2018 shows that governmental attitudes towards the EU are not reflected in parliamentary law-making and that parliamentary attention is mainly influenced by the level of Europeanisation of the policy field. This shows that backsliding governments do not generally oppose greater integration and underscores the necessity to distinguish between rhetorical Euroscepticism and Eurosceptic legislative action.
We strengthen the recent result of Cherubini and Guerreiro on the square mean of the error term in the prime geodesic theorem for PSL2(Z). We also develop a short interval version of this result.
In this study the behaviour of double sheared doweled connections was analysed, regarding the temporal changes in fire performance. Based on literature of special features of fire performance of ...timber and timber connections, a timber-steel-timber connection was used with dowels and bolts in the analysis.
A natural fire model was created with the OZone V2.0 software based on a real fire case and the relevant factors of the fire were defined. The thermal changes in the properties of the materials were also considered with the formulas and given parameters from the Eurocode.
The initial parameters of the connection were designed with calculation methods and detailing rules given in the Eurocodes and the performance was checked under tension and fire loads. With these parameters, a finite element model (FEM) was built with the Ansys software and the manually calculated results were compared with the FEM results.
As a last phase some input parameters were modified and their influence on the results was checked. Based on the analysis the effect of the applied fire curve, the width of the timber cross-section and the diameter of the fasteners were evaluated.
•Finite element modelling (FEM) a double sheared doweled timber connection in fire.•Natural fire curve with OZone V2.0 software.•Compared the effect of the fire curve on fire performance.•Compared the effect of the timber and fastener geometry on fire performance.•Compared the results with calculations based on standards.
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