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The article deals with the evaluation of the economic performance of domestic enterprises under foreign control, especially by subjects from Eastern European countries currently involved in the war conflict in Ukraine, through several key indicators monitored by Inward Foreign Affiliates Statistics (IFATS) and compiled by the Czech Statistical Office (CZSO). The war conflict in Ukraine raises, among other, questions about the effects of sanctions against aggressor countries. IFATS could serve as one possible source for evaluation of their impact with new data coming in the future. In the article, selected data from the IFATS database will be compared for the economy as a whole and according to the specific prevailing economic activities as well. Although the contribution of enterprises controlled by subjects from both aggressor countries and Ukraine to the Czech economy is quite marginal, the latter ones are among the most represented in terms of their number that is still growing. However, their economic importance grows much slower.

Abstract Wang tiles enable efficient pattern compression while avoiding the periodicity in tile distribution via programmable matching rules. However, most research in Wang tilings has considered tiling the infinite plane. Motivated by emerging applications in materials engineering, we consider the bounded version of the tiling problem and offer four integer programming formulations to construct valid or nearly-valid Wang tilings: a decision, maximum-rectangular tiling, maximum cover, and maximum adjacency constraint satisfaction formulations. To facilitate a finer control over the resulting tilings, we extend these programs with tile-based, color-based, packing, and variable-sized periodic constraints. Furthermore, we introduce an efficient heuristic algorithm for the maximum-cover variant based on the shortest path search in directed acyclic graphs and derive simple modifications to provide a 1/2 approximation guarantee for arbitrary tile sets, and a 2/3 guarantee for tile sets with cyclic transducers. Finally, we benchmark the performance of the integer programming formulations and of the heuristic algorithms showing that the heuristics provide very competitive outputs in a fraction of time. As a by-product, we reveal errors in two well-known aperiodic tile sets: the Knuth tile set contains a tile unusable in two-way infinite tilings, and the Lagae corner tile set is not aperiodic.

81-year-old female presented with subacute right lower extremity edema due to iliac vein compression by a markedly enlarged external iliac lymph node later identified as newly relapsed metastatic endometrial carcinoma. The patient underwent a full evaluation of the iliac vein lesion and cancer and had an intravenous stent placed with complete resolution of symptoms post-procedure.

The crochetage sign—a notch near the R-wave peak in the inferior leads—in conjunction with right axis deviation, complete or incomplete right bundle branch block, and right ventricular hypertrophy (R/S ratio >1 in lead V1) on 12-lead electrocardiogram are highly suggestive of atrial septal defect. (Level of Difficulty: Intermediate.)

We investigate the applicability of artificial neural networks (ANNs) in reconstructing a sample image of a sponge-like microstructure. We propose to reconstruct the image by predicting the phase of the current pixel based on its causal neighbourhood, and subsequently, use a non-causal ANN model to smooth out the reconstructed image as a form of post-processing. We also consider the impacts of different configurations of the ANN model (e.g., the number of densely connected layers, the number of neurons in each layer, the size of both the causal and non-causal neighbourhood) on the models’ predictive abilities quantified by the discrepancy between the spatial statistics of the reference and the reconstructed sample.

Peridynamics is a recently developed extension of continuum mechanics, which replaces the traditional concept of stress by force interactions between material points at a finite distance. The peridynamic continuum is thus intrinsically nonlocal. In this contribution, a bond-based peridynamic model with elastic-brittle interactions is considered and the critical strain is defined for each bond as a function of its length. Various forms of length functions are employed to achieve a variety of macroscopic responses. A detailed study of three different localization mechanisms is performed for a one-dimensional periodic unit cell. Furthermore, a convergence study of the adopted finite element discretization of the peridynamic model is provided and an effective event-driven numerical algorithm is described.

Malignant melanoma is commonly known for its high probability of metastasizing to distant organs. Metastases to gastrointestinal tract are well documented, but resulting jaundice is only scarcely seen. We present a case of histologically verified metastasis of amelanotic melanoma to the head of pancreas infiltrating the common bile duct and consequently causing obstructive jaundice which constituted its first clinical manifestation. Multidisciplinary approach is essential in patients with malignant melanoma since early detection of the melanoma or its metastases may improve patients’ clinical outcome, especially owing to the use of targeted biological treatment without any delay.

Laminated glass has been introduced to improve the mechanical performance, in particular impact resistance, of float glass while maintaining its transparency. However, its rate-dependent behaviour has not been sufficiently understood and various methods have been used to model it. This study compares the response of three material models commonly used to model glass cracking implemented in industry-standard LS-DYNA software: a smeared fixed crack model with the Rankine failure criterion, the nonlocal failure criterion by Pyttel et al., and the Johnson-Holmquist model. The input parameters are taken from several published studies, so each model was tested in multiple validated settings. The response of the models is compared with values measured during the earlier experimental campaign, the results of which were published in proceedings of the preceding conference. The reference experiments involved freely hanging full-scale samples, which eliminated the effect of structural supports and allowed more accurate validation of the numerical models. The response of two types of glass, i.e. annealed or heat-strengthened, and two types of interlayer, i.e., polyvinyl butyral or ethylene-vinyl acetate, was tested and is simulated herein. The time evolution of the contact force, specimen accelerations, and fracture patterns are discussed, demonstrating the main shortcomings of the three models in simulating destructive tests on laminated glass samples under low-velocity impact.

Abstract Exotic behaviour of mechanical metamaterials often relies on an internal transformation of the underlying microstructure triggered by its local instabilities, rearrangements, and rotations. Depending on the presence and magnitude of such a transformation, effective properties of a metamaterial may change significantly. To capture this phenomenon accurately and efficiently, homogenization schemes are required that reflect microstructural as well as macro-structural instabilities, large deformations, and non-local effects. To this end, a micromorphic computational homogenization scheme has recently been developed, which employs the particular microstructural transformation as a non-local mechanism, magnitude of which is governed by an additional coupled partial differential equation. Upon discretizing the resulting problem it turns out that the macroscopic stiffness matrix requires integration of macro-element basis functions as well as their derivatives, thus calling for higher-order integration rules. Because evaluation of a constitutive law in multiscale schemes involves an expensive solution of a non-linear boundary value problem, computational efficiency of the micromorphic scheme can be improved by reducing the number of integration points. Therefore, the goal of this paper is to investigate reduced-order schemes in computational homogenization, with emphasis on the stability of the resulting elements. In particular, arguments for lowering the order of integration from expensive mass-matrix to a cheaper stiffness-matrix equivalent are outlined first. An efficient one-point integration quadrilateral element is then introduced and a proper hourglass stabilization is discussed. Performance of the resulting set of elements is finally tested on a benchmark bending example, showing that we achieve accuracy comparable to the full quadrature rules, whereas computational cost decreases proportionally to the reduction in the number of quadrature points used.

Optimization of frame structures is formulated as a non-convex optimization problem, which is currently solved to local optimality. In this contribution, we investigate four optimization approaches: (i) general non-linear optimization, (ii) optimality criteria method, (iii) non-linear semidefinite programming, and (iv) polynomial optimization. We show that polynomial optimization solves the frame structure optimization to global optimality by building the (moment-sums-of-squares) hierarchy of convex linear semidefinite programming problems, and it also provides guaranteed lower and upper bounds on optimal design. Finally, we solve three sample optimization problems and conclude that the local optimization approaches may indeed converge to local optima, without any solution quality measure, or even to infeasible points. These issues are readily overcome by using polynomial optimization, which exhibits a finite convergence, at the prize of higher computational demands.

We critically assess the performance of several variants of dual and dual-primal domain decomposition strategies in problems with fixed subdomain partitioning and high heterogeneity in stiffness coefficients typically arising in topology optimization of modular structures. Our study considers Total FETI and FETI Dual-Primal methods along with three enhancements: k-scaling, full orthogonalization of the search directions, and considering multiple search-direction at once, which gives us twelve variants in total. We test these variants both on academic examples and snapshots of topology optimization iterations. Based on the results, we conclude that (i) the original methods exhibit very slow convergence in the presence of severe heterogeneity in stiffness coefficients, which makes them practically useless, (ii) the full orthogonalization enhancement helps only for mild heterogeneity, and (iii) the only robust method is FETI Dual-Primal with multiple search direction and k-scaling.

Background: COVID-19 pandemic has led to a loss of human life in millions and devastating socio-economic consequences worldwide. So far, vaccination is the most effective long-term strategy to control and prevent severe COVID-19 disease. The aim of the current study was to evaluate the humoral immune responses raised against the BNT162b2 vaccine in hospital healthcare workers. Methods: Total number of 173 healthcare workers enrolled in the study. Their blood samples were collected in three different time intervals after the second SARS-CoV-2 vaccination and evaluated by the ELISA method to detect anti-spike protein IgM and IgG antibodies. The baseline characteristics of all participants were collected using questionnaires and were evaluated for finding any significant data. Results: Our results demonstrated that the levels of antibodies were higher in the young group (21–30 years old) and also among male participants. Moreover, the highest levels of antibodies were detected from the group that received the third shot vaccination. Conclusions: Our results indicate that age, gender and third-dose vaccination can affect the levels of humoral immune responses against the BNT162b2 vaccine in healthcare workers.

This paper investigates a time-stepping procedure of the Newmark type for dynamic analyses of viscoelastic structures characterized by a generalized Maxwell model. We depart from a scheme developed for a three-parameter model by Hatada et al. [1], which we extend to a generic Maxwell chain and demonstrate that the resulting algorithm can be derived from a suitably discretized Hamilton variational principle. This variational structure manifests itself in an excellent stability and a low artificial damping of the integrator, as we confirm with a mass-spring-dashpot example. After a straightforward generalization to distributed systems, the integrator may find use in, e.g., fracture simulations of laminated glass units, once combined with variationally-based fracture models.

Laminated glass, consisting of glass layers connected with transparent foils, has found its applications in civil, automotive, or marine engineering. Due to a high contrast in layer properties, mechanical response of laminated glass structures cannot be predicted using classical laminate theories. On the other hand, engineering applications demand easy-to-use formulas of acceptable accuracy. This contribution addresses such simplified models for free vibrations of laminated glass beams, with the goal to determine their natural frequencies and modal damping properties. Our strategy is to approximate the complex behavior of a laminated structure with that of an equivalent monolithic beam. Its effective thickness is determined by the variational method proposed by Galuppi and Royer-Carfagni for static problems, which we extended for modal analysis. We show that this new approach overcomes inaccuracies of the currently used dynamic effective thickness model by López-Aenlle and Pelayo.

Wang tiles proved to be a convenient tool for the design of aperiodic tilings in computer graphics and in materials engineering. While there are several algorithms for generation of finite-sized tilings, they exploit the specific structure of individual tile sets, which prevents their general usage. In this contribution, we reformulate the NP-complete tiling generation problem as a binary linear program, together with its linear and semidefinite relaxations suitable for the branch and bound method. Finally, we assess the performance of the established formulations on generations of several aperiodic tilings reported in the literature, and conclude that the linear relaxation is better suited for the problem.

Inspired by the first order numerical homogenization, we present a method for extracting continuous fluctuation fields from the Wang tile based compression of a material microstructure. The fluctuation fields are then used as enrichment basis in Extended Finite Element Method (XFEM) to reduce number of unknowns in problems with fully resolved microstructural geometry synthesized by means of the tiling concept. In addition, the XFEM basis functions are taken as reduced modes of a detailed discretization in order to circumvent the need for non-standard numerical quadratures. The methodology is illustrated with a scalar steady-state problem.

Business and Consumer surveys are designed to signal turning points and provide in advance the informatik about potential changes in the economic cycle. The authors, using advanced methods of time series analysis, especially Granger causality and vector autoregressive models, deal with the question of to what extent the results of the surveys in the form of confidence indicators are able to outpace the development of the Czech economy represented by gross value added. In addition, the authors, experimenting with the structure of surveyed questions and used weights, propose some modifications in the construction of confidence indicators as stipulated by the European Commission with the aim to improve their forecasting abilities.

Regional price levels represent research topic that is currently under spotlight. Officially published data are focused on national price levels forming only one of the most important inputs for international comparison. Despite this, the national price levels are used to estimate regional indicators in Purchase Power Standard (PPS). Team of researchers from the University of Economics in Prague was dealing with the issue and estimated regional price levels for NUTS 3 regions in the Czech Republic for the year 2007. This estimate should be updated nevertheless the previously applied methodology cannot be used directly under current conditions but has to be adjusted because in the meantime several changes took place. The aim of the paper is to prepare a methodological background for further computations of renewed regional price levels in the Czech Republic and to introduce the main changes that have occurred since the previous results for the year 2007 were estimated. Impacts of these changes on the results are discussed as well.

Long time series of the main macroeconomic indicators are in demand by researches and economic experts. The Department of Economic Statistics from the University of Economics in Prague reconstructed the historici time series of GDP and its components in ESA 1995. Thus, we interpreted economic development of the Czech Rep. Between 1970 and 2013 based on ESA 1995. In 2014 the Czech Statistical Office recalculated national accounts since 1990 using the newly adapted European standard of accounts 2010. Introducing ESA 2010 brought the need to recalculate the historical time series into this new standard. The paper aims at describing the main adjustments in this recalculation and presenting the main results of expenditure and production approaches to GDP. Since the most important changes in the standards concern capitalisation the most significant changes affected gross capital formation.

Following publication of the original article [1], the authors reported the errors in the equations.

Laminated glass fulfills the demands on safety and security in transparent structural elements used in architecture and other fields of engineering. It can be constructed as forced-entry, bullet, or blast resistant. The basic three-layer configuration consists of two glass panes connected with a polymer or ionomer interlayer; the advanced products contain also other layers. The foil ensures shear coupling and provides post-breakage resistance and damping. For the design of laminated glass structures and their analysis, knowledge of mechanical properties of interlayers is essential. In numerical simulations, the interlayer is most typically described by the generalized Maxwell chain ‒ a classical viscoelastic model which can capture the time/temperature-dependent response of polymers under shear. Its parameters can be found for common interlayer types in the literature. However, they differ even for the same material, because of a slightly different content of additives, different test setups, and different data processing procedures. In this contribution, the dependence of the response of a laminated glass element on the material parameters of the polymer interlayer is studied by means of numerical modelling and experiments. Two examples are shown and discussed, i.e., quasi-static analysis of a simply-supported beam and modal analysis of a free-free beam. Numerical predictions are obtained by a layer-wise model based on the finite element method. These predictions are validated against the detailed experimental data. We demonstrate that using the Maxwell model parameters from the literature determined even for the same material type but not for the concrete foil may lead to unrealistic predictions.

Gross Domestic Product (GDP) represents the basic indicator of macroeconomic performance of the Czech economy and its importance is growing. The need to get the information on its development as quickly as possible for the necessary government acts is unquestionable. Nevertheless, the time taken to publish its first quarterly estimate of growth rate is significantly longer (45 days after the reference quarter) in comparison to some other countries such as the USA and the United Kingdom. The aim of this paper is to assess the relationship between composite leading indicator (CLI), composite koincidence indicator (CCI) and the development of GDP followed by verifi cation of a predictive ability of these composite indicators. The relationships between GDP and indicators available in this 30-day period which could enter to this CLI and CCI are analysed by the advanced methods of time series analysis.

Sustainable development has been the topic of expert debates since the 1970s and remains relevant until now. The issue is dealt with intensely by a lot of international institutions (e.g. Eurostat, UN, OECD). A common objective is to identify the domains of sets of sustainable development indicators, establish these sets, compile a smaller set of indicators suitable for international comparison and identify the sources of available data. Both the national and regional level of the issue is of extreme importance. This paper presents the outcome of an initial stage of our project. Its aim is to verify the set of sustainable development indicators for Czech regions (NUTS 3) that are used by the Czech Statistical Office. The principal task is to determine the availability and usability of the data for further statistical processing and tackle problems that may arise. The adjusted data set will then be used for further statistical analyses.

The purpose of this paper is to present a simple micromechanics-based model to estimate the effective thermal conductivity of macroscopically isotropic materials of matrix-inclusion type. The methodology is based on the well-established Mori-Tanaka method for composite media reinforced with ellipsoidal inclusions, extended to account for imperfect thermal contact at the matrix-inclusion interface, random orientation of particles and particle size distribution. Using simple ensemble averaging arguments, we show that the Mori-Tanaka relations are still applicable for these complex systems, provided that the inclusion conductivity is appropriately modified. Such conclusion is supported by the verification of the model against a detailed finite-element study as well as its validation against experimental data for a wide range of engineering material systems.

The purpose of this paper is to propose an inexpensive micromechanics-based scheme for stiffness homogenization and strength estimation of mortars containing crushed bricks, known as cocciopesto. The model utilizes the Mori-Tanaka method for determining the effective stiffness, combined with estimates of quadratic invariants of the deviatoric stresses inside phases to predict the compressive strength. Special attention is paid to the representation of the C-S-H gel layer around bricks and the interfacial transition zone around sand aggregates, which renders the predictions sensitive to particlesizes. Several parametric studies are performed to demonstrate that the method correctly reproduces the data and trends reported in the available literature. Moreover, the model is based exclusively on parameters with a clear physical or geometrical meaning, and as such it provides a convenient framework for its further experimental validation.

We have discovered a mistake in our original derivation related to the definition of the apparent conductivity due to orientation averaging.

AbstractLaminated glass units exhibit complex response as a result of different mechanical behavior and properties of glass and polymer foil. We aim to develop a finite element model for elastic laminated glass plates based on the refined plate theory by Mau. For a geometrically nonlinear description of the behavior of units, each layer behaves according to the Reissner-Mindlin kinematics, complemented with membrane effects and the von Kármán assumptions. Nodal Lagrange multipliers enforce the compatibility of independent layers in this approach. We have derived the discretized model by the energy-minimization arguments, assuming that the unknown fields are approximated by bi-linear functions at the element level, and solved the resulting system by the Newton method with consistent linearization. We have demonstrated through verification and validation examples that the proposed formulation is reliable and accurately reproduces the behavior of laminated glass units. This study represents a first step to the development of a comprehensive, mechanics-based model for laminated glass systems that is suitable for implementation in common engineering finite element solvers.