Iskanje po katalogu digitalne knjižnice

Opis: This doctoral thesis investigates cell-size-graded metallic and non-metallic Triply Periodic Minimal Surface (TPMS) structures' behavior under varying loading rates. Using experimental tests, analytical calculations, and advanced computer simulations, the research explores the interplay between material properties, cell size grading, and deformation mechanisms under different strain rates. The study focuses on enhancing the Direct Impact Hopkinson Bar (DIHB) setup for accurate force and displacement measurements and pioneering a method for quantifying inertial forces, critical at high strain rates. Key findings show that cell-size grading significantly affects deformation patterns, with initial deformation occurring in regions with smaller and lower stiffness cells across different loading rates and TPMS geometries. The research also highlights topology's influence on mechanical response, with photopolymer-based diamond structures showing superior energy absorption and gas-atomized steel structures favoring gyroid configurations. This underscores the importance of considering both topology and base material selection during TPMS design. The study demonstrates the increasing prominence of inertial forces as deformation rates rise, impacting structural response and failure likelihood in TPMS structures. These insights inform the design of optimized cellular metamaterials for high-performance applications requiring superior energy absorption and structural integrity under high loading rates. The research advances material characterization techniques and computational modelling capabilities, contributing to the development of next-generation cellular metamaterials for broader engineering applications.
Ključne besede: Triply Periodic Minimal Surfaces, TPMS, Cell-size-grading, Impact, High-strainrate, Digital Image Correlation
Objavljeno v DKUM: 17.10.2024; Ogledov: 0; Prenosov: 16
Celotno besedilo (46,48 MB)

Opis: While extensive literature exists on the COVID-19 pandemic at regional and national levels, understanding its dynamics and consequences at the city level remains limited. This study investigates the pandemic in Maringá, a medium-sized city in Brazil’s South Region, using data obtained by actively monitoring the disease from March 2020 to June 2022. Despite prompt and robust interventions, COVID-19 cases increased exponentially during the early spread of COVID-19, with a reproduction number lower than that observed during the initial outbreak in Wuhan. Our research demonstrates the remarkable impact of non-pharmaceutical interventions on both mobility and pandemic indicators, particularly during the onset and the most severe phases of the emergency. However, our results suggest that the city’s measures were primarily reactive rather than proactive. Maringá faced six waves of cases, with the third and fourth waves being the deadliest, responsible for over two-thirds of all deaths and overwhelming the local healthcare system. Excess mortality during this period exceeded deaths attributed to COVID-19, indicating that the burdened healthcare system may have contributed to increased mortality from other causes. By the end of the fourth wave, nearly three-quarters of the city’s population had received two vaccine doses, signifcantly decreasing deaths despite the surge caused by the Omicron variant. Finally, we compare these fndings with the national context and other similarly sized cities, highlighting substantial heterogeneities in the spread and impact of the disease.
Ključne besede: complex system, correlation, epidemics, COVID-19
Objavljeno v DKUM: 17.07.2024; Ogledov: 117; Prenosov: 21
Celotno besedilo (1,79 MB)
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Opis: At the Orlica fault in the Krško basin, combined barasol detectors were buried in six boreholes, two along the fault itself and four on either side of it, to measure and record radon activity, temperature and pressure in soil gas every 60 minutes for four years. Data collected have been analysed in a manner aimed at distinguishing radon anomalies resulting from environmental parameters (air and soil temperature, barometric pressure, rainfall) from those caused solely by seismic events. The following approaches have been used to identify anomalies: (i) ± 2σ deviation of radon concentration from the seasonal average, (ii) correlation between time gradients of radon concentration and barometric pressure, and (iii) prediction with regression trees within a machine learning program. In this paper results obtained with regression trees are presented. A model has been built in which the program was taught to predict radon concentration from the data collected during the seismically inactive periods when radon is presumably influenced only by environmental parameters. A correlation coefficient of 0.83 between measured and predicted values was obtained. Then, the whole data time series was included and a significantly lowered correlation was observed during the seismically active periods. This reduced correlation is thus an indicator of seismic effect.
Ključne besede: radon in soil gas, environmental parameters, earthquakes, correlation, regression trees, forecasting
Objavljeno v DKUM: 15.05.2018; Ogledov: 1784; Prenosov: 88
Celotno besedilo (271,01 KB)
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Opis: The aim of the article is to answer the question if the level of intensity of `ex ante` regulation (also `regulation`) imposed by NRA (national regulatory Authority or regulators) influence on the development of incumbent DSL technology against other Access technologies. There are several approaches which support the basic idea of regulation, that Ćex anteĆ regulation promotes the competition. The approaches must be also based on the size of themarket. In the internet world there are different access technologies. OpenAccess is crucial for the development of competition. Regulators have to ensure, that also new entrants can reach end users through the facilities of the incumbent operator. Based on the approach of three criteria, European Commission defines two wholesale relevant access markets both based on DSL technology (`bitstream` access and unbundled local loop) susceptible to sector specific `ex ante` regulation. In the last stage also optical access isincluded on the relevant markets. Other technologies are still not equivalent to incumbent DSL technology according to the opinion of the commission. The intensity of regulation influences on the competition conditions. It influences on the level where and at which point of the investment ladder entrants will enter the market through wholesale inputs or through building its own infrastructure.
Ključne besede: regulation, market analyses, broadband, correlation, DSL technology
Objavljeno v DKUM: 22.01.2018; Ogledov: 1281; Prenosov: 396
Celotno besedilo (490,76 KB)
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Opis: A study of the high-pressure phase equilibria in the ternary system oleic acid/1- octanol/supercritical CO2 was performed to obtain information for optimization of enzymatic synthesis of n-octyl oleate. Equilibrium data were measured at temperatures of 308.15, 323.15 and 343.15 K over a pressure range from 1 to 25 MPa. Two different apparatuses: a Variable Volume View Cell and a Batch Stirred Tank were used employing synthetic and static-analytic measurement methods, respectively. The measured solubility of dense CO2 in the binary liquid mixture oleic acid/1-octanol covered the range from 0.0781 to 0.7686 of CO2 molar fraction. CO2 solubility increased with increasing pressure up to 10 MPa. At higher pressures, no significant increase was observed. The Soave-Redlich-Kwong equation-of-state (SRK-EoS) with quadratic mixing rules was successfully used for data correlation in the whole P-T-x region studied.
Ključne besede: data correlation, 1-octanol, oleic acid, supercritical carbon dioxide, Soave-Redlich-Kwong equation-of-state, vapor-liquid equilibria
Objavljeno v DKUM: 05.07.2017; Ogledov: 1558; Prenosov: 118
Celotno besedilo (3,35 MB)
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