File formats for long-term preservation of electronic publications in the e-deposit system in the Czech Republic

This bachelor's thesis focuses on selection of archival formats for the purposes of long term preservation of electronic pulications within the Czech e-deposit system. It analyzes the current situation in the Czech Republic and, on the basis of a sample of seven foreign institutions, compares it with foreign approaches and experiences. The first part of the thesis deals with the electronic formats of electronic books on the theoretical side. Based on the market analysis, the formats relevant to the Czech market for electronic publications are identified and the risks of the individual formats are described with regard to the possibilities of their long-term preservation. The second part is devoted to case studies in which the format policies of foreign libraries dealing with long-term archiving of electronic publications are documented. An analysis of electronic publications, voluntarily deposited by the publisher to the NL CR during the pilot operation of the e-deposit system, is also performed. The conclusion of the thesis summarizes the findings in the form of recommendations for archival formats for the further development of the Czech e-deposit system.Bakalářská práce se zabývá výběrem archivačních formátů pro potřeby dlouhodobého uchovávání elektronických publikací v rámci českého systému pro e-deposit. Analyzuje současný stav v ČR a na základě vzorku sedmi zahraničních institucí jej porovnává se zahraničními přístupy a zkušenostmi. První část práce se zabývá elektronickými formáty elektronických knih po teoretické stránce. Na základě analýzy trhu jsou určeny formáty relevantní pro český trh s elektronickými publikacemi a jsou popsána rizika jednotlivých formátů s ohledem na možnosti jejich dlouhodobého uchování. Druhá část práce je věnována případovým studiím, ve kterých jsou zdokumentovány formátové politiky zahraničních knihoven, zabývajících se dlouhodobou archivací elektronických publikací. Je také provedena analýza dat elektronických publikací, dobrovolně odevzdaných vydavateli do NK ČR v rámci pilotního provozu systému pro e-deposit. Závěr práce shrnuje zjištěné poznatky formou doporučení archivačních formátů pro další rozvoj českého systému pro e-deposit.Institute of Information Studies and LibrarianshipÚstav informačních studií a knihovnictvíFilozofická fakultaFaculty of Art

Computing the decomposable entropy of belief-function graphical models

In 2018, Jiroušek and Shenoy proposed a definition of entropy for Dempster-Shafer (D-S) belief functions called decomposable entropy (d-entropy). This paper provides an algorithm for computing the d-entropy of directed graphical D-S belief function models. We illustrate the algorithm using Almond's Captain's Problem example. For belief function undirected graphical models, assuming that the set of belief functions in the model is non-informative, the belief functions are distinct. We illustrate this using Haenni-Lehmann's Communication Network problem. As the joint belief function for this model is quasi-consonant, it follows from a property of d-entropy that the d-entropy of this model is zero, and no algorithm is required. For a class of undirected graphical models, we provide an algorithm for computing the d-entropy of such models. Finally, the d-entropy coincides with Shannon's entropy for the probability mass function of a single random variable and for a large multi-dimensional probability distribution expressed as a directed acyclic graph model called a Bayesian network. We illustrate this using Lauritzen-Spiegelhalter's Chest Clinic example represented as a belief-function directed graphical model

On conditional belief functions in directed graphical models in the Dempster-Shafer theory

The primary goal is to define conditional belief functions in the Dempster-Shafer theory. We do so similarly to probability theory's notion of conditional probability tables. Conditional belief functions are necessary for constructing directed graphical belief function models in the same sense as conditional probability tables are necessary for constructing Bayesian networks. We provide examples of conditional belief functions, including those obtained by Smets' conditional embedding. Besides defining conditional belief functions, we state and prove a few basic properties of conditionals. In the belief-function literature, conditionals are defined starting from a joint belief function. Conditionals are then defined using the removal operator, an inverse of Dempster's combination operator. When such conditionals are well-defined belief functions, we show that our definition is equivalent to these definitions

Dynamic impact testing of cellular solids and lattice structures : Application of two-sided direct impact Hopkinson bar

Direct impact testing with a Hopkinson bar is, nowadays, a very popular experimental technique for investigating the behavior of cellular materials, e.g., lattice metamaterials, at high strain-rates as it overcomes several limitations of the conventional Split Hopkinson Pressure Bar (SHPB). However, standard direct impact Hopkinson bars (DIHB) have only single-sided instrumentation complicating the analysis. In this paper, a DIHB apparatus instrumented with conventional strain-gauges on both bars (a so called Open Hopkinson Pressure Bar - OHPB) is used for dynamic impact experiments of cellular materials. Digital image correlation (DIC) is used as a tool for investigating the displacements and velocities at the faces of the bars. A straight-forward wave separation technique combining the data from the strain-gauges with the DIC is adopted to increase the experiment time window multiple times. The experimental method is successfully tested at impact velocities in a range of 5 − 30 m⋅s− 1 with both linear elastic and visco-elastic bars of a medium diameter. It is shown that, under certain circumstances, a simple linear elastic model is sufficient for the evaluation of the measurements with the viscoelastic bars, while no additional attenuation and phase-shift corrections are necessary. The applicability of the experimental method is demonstrated on various experiments with conventional metal foams, hybrid foams, and additively manufactured auxetic lattices subjected to dynamic compression

File formats for long-term preservation of electronic publications in the e-deposit system in the Czech Republic

This bachelor's thesis focuses on selection of archival formats for the purposes of long term preservation of electronic pulications within the Czech e-deposit system. It analyzes the current situation in the Czech Republic and, on the basis of a sample of seven foreign institutions, compares it with foreign approaches and experiences. The first part of the thesis deals with the electronic formats of electronic books on the theoretical side. Based on the market analysis, the formats relevant to the Czech market for electronic publications are identified and the risks of the individual formats are described with regard to the possibilities of their long-term preservation. The second part is devoted to case studies in which the format policies of foreign libraries dealing with long-term archiving of electronic publications are documented. An analysis of electronic publications, voluntarily deposited by the publisher to the NL CR during the pilot operation of the e-deposit system, is also performed. The conclusion of the thesis summarizes the findings in the form of recommendations for archival formats for the further development of the Czech e-deposit system

Compressive Behaviour of Additively Manufactured Periodical Re-Entrant Tetrakaidecahedral Lattices at Low and High Strain-Rates

Compressive deformation behaviour of additively manufactured lattice structures based on re-entrant tetrakaidecahedral unit-cell geometry were experimentally investigated under quasi-static and dynamic loading conditions. Specimens of four different structures formed by three-dimensional periodical assembly of selected unit-cells were produced by a laser powder bed fusion technique from a powdered austenitic stainless steel SS316L. Quasi-static compression as well as dynamic tests using split Hopkinson pressure bar (SHPB) apparatus at two strain-rates were conducted to evaluate the expected strain-rate sensitivity of the fundamental mechanical response of the structures. To evaluate the experiments, particularly the displacement fields of the deforming lattices, optical observation of the specimens using a high-resolution camera (quasi-static loading) and two synchronised high-speed cameras (SHPB experiments) was employed. An in-house digital image correlation algorithm was used in order to evaluate the anticipated auxetic nature of the investigated lattices. It was found that neither of the investigated structures exhibited auxetic behaviour although strain-rate sensitivity of the stress–strain characteristics was clearly identified for the majority of structures

Dynamic Deformation Behaviour of Chiral Auxetic Lattices at Low and High Strain-Rates

The mechanical behaviour of three different auxetic cellular structures, hexa-chiral 2D, tetra-chiral 2D and tetra-chiral 3D, was experimentally investigated in this study. The structures were produced with the powder bed fusion method (PBF) from an austenitic stainless steel alloy. The fundamental material mechanical properties of the sample structures were determined with classic quasi-static compressive tests, where the deformation process was captured by a high-resolution digital camera. The Split Hopkinson Pressure Bar (SHPB) apparatus was used for dynamic impact testing at two impact velocities to study the strain-rate dependency of the structures. Two synchronised high-speed cameras were used to observe the impact tests. The captured images from both quasi-static and dynamic experiments were processed using a custom digital image correlation (DIC) algorithm to evaluate the displacement/strain fields and the Poisson’s ratio. Predominant auxetic behaviour was observed in all three structures throughout most of the deformation process both under quasi-static and impact loading regimes. The tetra-chiral 2D structure showed the most significant auxetic behaviour. Significant stress enhancement in all tested structures was observed in dynamic testing. The Poisson’s ratio strain-rate dependency was confirmed for all three auxetic structures

Strain Rate-Dependent Compressive Properties of Bulk Cylindrical 3D-Printed Samples from 316L Stainless Steel

The main aim of the study was to analyse the strain rate sensitivity of the compressive deformation response in bulk 3D-printed samples from 316L stainless steel according to the printing orientation. The laser powder bed fusion (LPBF) method of metal additive manufacturing was utilised for the production of the samples with three different printing orientations: 0∘, 45∘, and 90∘. The specimens were experimentally investigated during uni-axial quasi-static and dynamic loading. A split Hopkinson pressure bar (SHPB) apparatus was used for the dynamic experiments. The experiments were observed using a high-resolution (quasi-static loading) or a high-speed visible-light camera and a high-speed thermographic camera (dynamic loading) to allow for the quantitative and qualitative analysis of the deformation processes. Digital image correlation (DIC) software was used for the evaluation of displacement fields. To assess the deformation behaviour of the 3D-printed bulk samples and strain rate related properties, an analysis of the true stress–true strain diagrams from quasi-static and dynamic experiments as well as the thermograms captured during the dynamic loading was performed. The results revealed a strong strain rate effect on the mechanical response of the investigated material. Furthermore, a dependency of the strain-rate sensitivity on the printing orientation was identified

components

An evaluation of string similarity measures on pricelists of compute

Energy-conserving interface dynamics with asynchronous direct time integration employing arbitrary time steps

The derivation and implementation of an asynchronous direct time integration scheme for domain-decomposed finite element models is presented. To maximize clarity in the description of the proposed asynchronous integration, the scheme is restricted to the linear-elastic stress wave propagation case. The proposed method allows the integration of individual subdomains with independent time steps. There is no requirement for an integer time steps ratio of the interacting domains while maintaining zero interface energy. The subdomains are connected by the condition of the continuity of the acceleration field at the interface. In addition, the a posteriori technique is applied to satisfy the continuity of the displacement and velocity fields. Another important contribution of this paper lies in the description of the implementation - we offer the reader a general description of the implementation of the case of any number of subdomains with any number of constraints between them, while the basics of the algorithm are explained on a single domain pair. The functionality of the asynchronous integrator is verified by solving selected problems and comparing with analytical solutions and experimental measurements obtained using a Split Hopkinson pressure bar setup