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The financing of church life in the Slovak Republic is still a topical theme. Cofinancing church activities from the national budget has not always garnered a positive response among the laity. The current scheme of financing Slovak churches developed out of the cooperative model of a relationship with the state. Its roots are found in the reformation period of Emperor Joseph II (1780–1790). The traditional church financing scheme was cleverly used by the communist regime that came to power in Czechoslovakia after the end of the Second World War. The author demonstrates, using specific documentation from archived materials, the limitations to religious freedom that resulted from the scheme of the state taking on the financing of church life.

Purpose Some recent effort showed that usage of Krueger flaps helps to maintain laminar flow in cruise flight. Such flaps are positioned higher relative to the chord to shield the leading edge from the insect contamination during take-off. The flap passes several through critical intermediate position during the deployment to its design position. The purpose of this paper is to analyse the aerodynamics. Design/methodology/approach To better understand such flow phenomena, the combined approach of computational fluid dynamics and experimental methods were used. Flow simulation was performed with in-house finite volume Navier–Stokes solver in fully turbulent unsteady RANS regime. The experimental data were obtained by means of force and pressure measurements and some areas of the flow field were examined with 2 C particle image velocimetry. Findings The airfoil with flap in critical position has a very limited maximum lift coefficient. The maximum achievable lift coefficient during the deployment is significantly affected by the vertical position of the trailing edge of the flap. The most unfavourable position during the deployment is not the flap perpendicular to the chord, but the flap inclined closer to it is the retracted position. Research limitations/implications The flap movement was not simulated either in the simulation or in the experiment. Only intermediate static positions were examined. Practical implications A better understanding of aerodynamic phenomena connected with the deployment of a Krueger flap can contribute to the simpler and lighter of kinematics and also to decrease time-to-market. Originality/value Limited experimental and computational results of Krueger flap in critical positions during the deployment are published in the literature.

The paper deals with the impact of explosion on the damage development in the structure that forms a boundary of closed or semi-closed space – tunnel - the explosion in which is initiated. In the previous publications of the author the penalty formulation of the problem was used; now Uzawa’s algorithm is applied, which appears to be more promising algorithm accelerating the iterative process of damage development in the structure. Shock waves propagating in the airspace can be described by non-linear conservation equations starting with Euler’s equations which are used to be solved by forward differences of the system of pseudo-linear equations, using Arbitrary Lagrangian-Euler Method (ALE). Conservation equations are formulated for two phases: air and solid. In the solid phase, concrete lining, the time-dependent elasticity of free rectangular elements undergoing the damage, is solved by uniformly distributed boundary elements. The paper is focused on damage to the concrete lining due to impact of the explosion in the tunnel.

Flow in a branched channel is studied experimentally using the PIV technique. The presented study is concentrated on clarifying the dynamical behaviour in individual branches. The 11 branches issuing from the main channel perpendicularly, all channels are of rectangular cross-section. First, the time-mean flow-field is shown, then the flow dynamics is investigated using the OPD method. Flow patterns and frequencies are evaluated in three selected branches. The separated flow in branches exhibits highly dynamical behaviour, which differs substantially in the branches close to the inflow, in the main channel middle and close to its end. The typical topologies and frequencies of the detected quasi-periodical structures in the channel braches are shown in the study. Mostly, the flow-fields are populated by trains of vortices with alternating orientation and saddle-like structures. The flow-field close to the channel walls affects heat transfer process between the wall and fluid.

The ongoing energy transition challenges the stability of the electrical power system. Stable operation of the electrical power grid requires both the voltage (amplitude) and the frequency to stay within operational bounds. While much research has focused on frequency dynamics and stability, the voltage dynamics has been neglected. Here, we study frequency and voltage stability in the case of simple networks via linear stability and bulk analysis. In particular, our linear stability analysis of the network shows that the frequency secondary control guarantees the stability of a particular electric network. Even more interesting, while we only consider secondary frequency control, we observe a stabilising effect on the voltage dynamics, especially in our numerical bulk analysis.

An experimental study on the flow pattern dynamics in a standard mixing vessel with radial baffles filled with water and induced by a pitched blade impeller pumping downward is presented. Investigation is mainly focused on detection and analysis of quasi-periodical or periodical low-frequency phenomenon connected with time- and length-scales considerably exceeding the Blade Passage Frequency (hereinafter BPF) and common turbulent eddies. This phenomenon, which is expressed as large-scale mean-flow variations, is generally known as flow Macro-Instability (hereinafter MI). It could break-down just below the liquid surface, or it crashes to the liquid surface and causes its Macro-Swelling (hereinafter MS). Our investigation was based on classical two-dimensional (2D) Particle Image Velocimetry (hereinafter PIV) measurement within 3 selected vertical planes in the vessel and subsequent analysis of the velocity field. The dominant frequencies evaluated in the selected points and overall analysis of the quasi-periodical macro-flow pattern behavior is to be shown. Identification of the quasi-periodical substructures appeared within the flow pattern was performed using the Oscillation Pattern Decomposition (hereinafter OPD) method. Observation of the macro-flow patterns confirmed presence of the macro-flow structures detected within flow pattern at the identical mixing pilot plant setup by previous investigations of the MIs phenomenon, i.e., the primary circulation loop and strong impeller discharge jet located in the lower vessel segment and the strong ascending wall current at the baffle, which break-down below the surface very often. A further important contribution of the presented work is the investigation of both flow pattern within the baffles vicinity and in the middle of the sector far from the baffle, showing a significant difference. Low-frequency periodical (or quasi-periodical) behavior of the investigated macro-structures was qualitatively confirmed by the presented results and it was quantified using the velocity dominant frequencies evaluation, as noted below. This frequency analysis brings insight into the supposed and detected interconnections between dynamics of the adjacent flow structures. Detected different flow patterns within the main plane near the baffles and in the inclined plane reveal a strong influence of the baffle presence to the local vertical flow, especially within the upper part of the vessel. Quite a different flow pattern appears tangentially in front of and behind the baffle, where a wake is revealed, indicating significant influence of the baffle on the local tangential flow. The new findings represent a contribution to better understanding the physical phenomena behind the standard mixing process.

The article presents the way how the existing small vacuum aerodynamic tunnel IT (Institute of Thermomechanics) has been adapted for the measurement of the aeroelastic properties of the NACA 0015 airfoil and of the blade cascades composed of various types of blades with two degrees of freedom, pitch and common plunge. Attention was focused on the possibility of studying self-excited vibration at lower subsonic speeds. The modification of the test section is based on the knowledge gained during the study of self-excited airfoil oscillation.

The realization of complex long-range ordered structures in a Euclidean plane presents a significant challenge en route to the utilization of their unique physical and chemical properties. Recent progress in on-surface supramolecular chemistry has enabled the engineering of regular and semi-regular tilings, expressing translation symmetric, quasicrystalline, and fractal geometries. However, the k -uniform tilings possessing several distinct vertices remain largely unexplored. Here, we show that these complex geometries can be prepared from a simple bitopic molecular precursor – 4,4’-biphenyl dicarboxylic acid (BDA) – by its controlled chemical transformation on the Ag(001) surface. The realization of 2- and 3-uniform tilings is enabled by partially carboxylated BDA mediating the seamless connection of two distinct binding motifs in a single long-range ordered molecular phase. These results define the basic self-assembly criteria, opening way to the utilization of complex supramolecular tilings. Division of a Euclidean plane into regular polygons may result in intriguing physical and chemical properties. Here the authors present a way to synthesize complex k -uniform tilings at surfaces by a partial chemical transformation of a precursor molecule.

This contribution introduces a newly proposed thermal based method for measurements of drift for in-field applications on real cooling towers up to an eliminator efficiency of approximately 0.0001% of circulating water flow. This method should thus become the main alternative to the methods used nowadays. The main advantage of this newly proposed measurement procedure should be its easy preparation and implementation and quick analysis of measurement results. The article summarizes the development of an innovative probe, and why this new probe and the entire method is needed for the industry. The design of this new probe consists of two main directions of development pathways: the electronic part and the aerodynamic part. The first one lies in the development of a sensor (and the accompanying electronics) and sums up the theoretical principle of the method (the calculation of droplet sizes scatter based on statistics, and the calculation of power needed for the sensor). The aerodynamics part derives from the desired efficiency and accuracy of the measurement and is based on precedent modelling and calculations of flow, containing droplets of various sizes through various uniquely shaped channels. The contribution also demonstrates an experiment made thus far, showing quantity measured and the drift evaluation process.

The aim of this paper is to study the physics related to lift generation on an airfoil. A new hypothesis [1] of physical mechanism of flight relies on existence of streamwise vortical structures above the wing and inside the wake. The vortices origin as a consequence of flow instability inside the boundary layer developed under adverse pressure gradient. These structures are highly dynamical in nature, they change position and size very rapidly. A simple airfoil in the form of a flat plate with moderate angle of attack is considered in the presented research that generates suitable flow at rather low Reynolds number. Stereo PIV time resolved measurement technique is used to capture high-dynamic data in several planes which are located in the wake and are perpendicular to freestream or parallel to the airfoil. The overall image of the flow field dynamics will be created using POD decomposition. Distinct flow patterns with associated kinetic energy are to be described as well as their role in the studied case. Existence of streamwise vorticity is proved, topology and other parameters are estimated in the paper; however related pressures and forces are not evaluated.