In this paper, a 3D phase-field model for brittle fracture is applied for analyzing the complex fracture patterns appearing during the Vickers indentation of fused silica. Although recent phase-field ...models for the fracture caused by the indentation loading have been verified by some simpler academic axis-symmetric examples, a proper validation of such models is still missing. In addition, heavy computational costs, and a complicated compression stress field under the indenter, which demands different energy decompositions, have been identified as the most important impediments for the successful application of the phase-field method for such problems. An adaptive strategy is utilized for reducing the computational costs, and some modifications are introduced, which enable an accurate simulation of the Vickers indentation fracture. Here, the fracture initiation ring outside the contact zone is detected by using different energy decompositions, and the dominant cone-crack formation under the Vickers indenter is observed. Different contact conditions are investigated. The proposed model is validated by experimental measurements, and a quantitative and qualitative comparison between experimental and numerical results is conducted.
Our aim was to determine the frequency and characteristics of neurological post-COVID-19 syndrome and the diagnostic and therapeutic measures that were used for the treatment of these patients. Data ...were collected for 243 patients examined during the period of 11 May 2021 to 22 June 2022. The inclusion criteria were COVID-19 illness and neurological symptoms associated with COVID-19. The exclusion criteria were non-neurological symptoms, patients who did not suffer from COVID-19, and symptoms that occurred after vaccination against the SARS-CoV-2 virus. Data for 227 patients with neurological post-COVID-19 symptoms were analyzed. Most patients presented with multiple symptoms, most often headache, cognitive impairment, loss of smell, paresthesia, fatigue, dizziness, and insomnia. Patients were most often referred for consultative examinations, neuroradiological imaging, and EEG. The therapy was mostly symptomatic. Most patients had no change in their symptoms on follow-up visits (53.21%), while positive outcome was found in 44.95% of patients. This study found that neurological post-COVID-19 syndrome appears to be more common in women, and generally, the most common symptoms are headache and cognitive impairment. The gender distribution of symptoms was clearly visible and should be further investigated. There is a need for longitudinal follow-up studies to better understand the disease dynamic.
The phase-field approach to fracture modelling has gained much attention in the field of computational fracture mechanics in the past decade. The phase-field approach eliminates the need for the ...numerical tracking of the sharp crack discontinuities by the smooth transition of a scalar damage field whose value differentiates between the broken and intact material states. Its variational based approach has been proven to be thermodynamically consistent and able to solve complex fracture processes. Consequently, many different phase-field fracture models have emerged. In this contribution, a few well-known phase-field models for brittle fracture modelling have been implemented within the staggered algorithm with stopping criterion based on the control of the residual norm, recently developed by the authors. The implementation has been conducted within the commercial finite element software Abaqus and expanded to the three-dimensional settings. The experimental validation of the numerical models is then conducted on the tensile, compact tension (CT) and single edge notched bend (SENB) specimens made of the thermoplastic polymer, polymethylmethacrylate (PMMA). It has been demonstrated that with a suitable choice of the length scale parameter, the developed staggered phase-field fracture models can provide valid prediction of the brittle crack initiation and propagation under quasi-static loading conditions.
The problem of distribution has been drawing the attention of researchers for years. In their research they analyze the uniformity of distribution using Pareto model of distribution, the Lorenz curve ...and the Gini coefficient. Also some authors are testing the applicability of models from statistical physics to the problem of distribution to better describe it. In addition to the analysis of distribution at the level of states and certain groups such as the Forbes list, the problem is spreading to the global level, where we analyze the distribution of GDP as a measure of the wealth of individual countries. In this paper we analyzed the distribution of GDP of countries applying the Pareto model, Lorenz curve, Gini coefficient and Boltzmann Gibbs distribution from statistical physics. The analysis was done for 2015, while the Gini coefficient analysis was done during the period from 1990 to 2015.
Stacking interactions in the crystal structures of square‐planar transition metal complexes from the Cambridge Structural Database with five‐ and six‐membered chelate rings fused with C6‐arom rings ...(arom = aromatic) were analyzed. The distribution of distances between the closest C6‐arom–C6‐arom and C6‐arom–chelate contacts shows that in a large fraction of the intermolecular interactions the C6‐arom ring of one molecule is closer to the chelate than to the C6‐arom ring of the other molecule. These results indicate a possible preference of the C6‐arom ring to form stacking contacts with the chelate rings. The preference is ubiquitous and does not depend on the metal type.
Inflation is a phenomenon which attracts the attention of many researchers. Inflation is not a recent date phenomenon, but it has existed ever since money emerged in world’s first economies. With the ...development of economy and market, inflation developed as well. Today, even though there is a considerable number of research papers on inflation, there is still not enough knowledge about all factors which might cause inflation, and influence its evolution and dynamics. Regression analysis is a powerful statistical tool which might help analyse a vast amount of data on inflation, and provide an answer to the question about the factors of inflation, as well as the way those factors influence it. In this article Newton’s Law of Cooling was applied to determine the long-term dynamics of monetary aggregates and inflation in Serbia and Croatia.
•Inflation is a phenomenon which attracts the attention of many researchers.•With the development of economy and market, inflation developed as well.•We will apply Newton’s Law on Cooling in this paper to determine the long-term dynamics of inflation in Serbia and Croatia.
The main objective of this study is to visualize the flood risk vulnerability of municipalities in the Republic of Serbia through mapping and spatial analysis of precipitation data and data related ...to the losses. GIS tools enable spatial analysis and visualization of historical data on losses combined with temporal and geo-spatial distribution of precipitation, and QGIS tool was used for visualization of precipitation data and data on damages caused by floods and flash floods. As a result of these analyses, areas with potential high risks of losses are detected, which enables undertaking appropriate steps and measures in order to minimize future losses.
Complex compounds of NiII, CoIII, CuII with bis(phthalazine-1-hydrazone)-2,6-diacetylpyridine (Hz2DAP) ligand were synthesised. The coordination sphere of the metals is different in spite of the same ...synthetic procedure and same degree of protonation of the ligand, Hz2DAP-H. With ZnII a neutral complex Zn(Hz2DAP-2H)·H2O is obtained with double deprotonated ligand molecule. Display omitted
Four new complex compounds of bis(phthalazine-1-hydrazone)-2,6-diacetylpyridine (Hz2DAP) ligand with NiII, CoIII, CuII and ZnII metal centres were synthesised and characterised by single-crystal X-ray diffraction and IR spectral data. The antimicrobial activity of Hz2DAP and the obtained complexes Co(Hz2DAP-H)Cl2·MeOH, Ni(Hz2DAP-H)Cl·MeOH, Cu(Hz2DAP-H)Cl and Zn(Hz2DAP-2H)·H2O were tested in vitro against selected Gram(−) and Gram(+) bacterial strains and fungi. The antimicrobial activity of the ligand is negligible, while its complexes with NiII, CoIII and CuII show considerable activity against Escherichia coli, Staphylococcus aureus and Micrococcus lysodeikticus. On the contrary, Zn(Hz2DAP-2H)·H2O promotes the growth of Candida albicans, while its antibacterial activity is negligible. On the basis of thermal data and those from coupled TG/MS measurements the decomposition mechanisms were determined and evaluated.
Stacking interactions in the crystal structures of square-planar transition metal complexes from the Cambridge Structural Database with five- and six-membered chelate rings fused with C
6-arom
rings ...(arom = aromatic) were analyzed. The distribution of distances between the closest C
6-arom
–C
6-arom
and C
6-arom
–chelate contacts shows that in a large fraction of the intermolecular interactions the C
6-arom
ring of one molecule is closer to the chelate than to the C
6-arom
ring of the other molecule. These results indicate a possible preference of the C
6-arom
ring to form stacking contacts with the chelate rings. The preference is ubiquitous and does not depend on the metal type.
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