Fracturing in concrete via lattice-particle model

Numerical simulation is used to explore the behavior of concrete beams of different sizes and different notch lengths, loaded in three-point bending. The entire range of notch depth is studied. One limit case is type 1 fracture, which occurs when the notch depth is zero and the crack initiates from a smooth surface (this is the case of the modulus of rupture test). Another limit is type 2 fracture, which occurs for deep enough notches. Both cases exhibit very different size effects. The fracture is simulated numerically with a robust mesolevel lattice-particle model. The results shed light on the transitional behavior in which the notch depth is non-zero but not deep enough for developing the the type 2 size effect dominated by energy release from the structure. In agreement with experimental observations and theoretical predictions, the numerical results show evidence of a decreasing macroscopic fracture energy as the ligament gets very short

Perseus as Alter Ego of Ferdinand I

The paper analyses three relief sculptures that decorate spandrels of the northern façade of the Prague Bel‑ vedere, which was built by Ferdinand I between 1538 and ca. 1550. Their uniqueness consists in that it is the first series inspired by the myth of Perseus in Renaissance architectural sculpture. We find here, from left to right: Perseus freeing Andromeda, Perseus turning Atlas into a rock by showing him the head of Medusa, and Pegasus creating a source of poetical inspiration. The monogram, FA (Ferdinand I and Anna, his wife) is the only inscription on this villa and it has a crucial role in the villa decoration. We may consider Perseus as alter ego of Ferdinand I

St. George at Prague Castle and Perseus: an Impossible Encounter?

St. George and Perseus crossed their paths for the first time in the 11th century when the myth of Greek hero inspired the legend of a Christian saint. In the 14th century, the pictorial types of St. George, Perseus and Bellerophon fighting the dragon started converging. The famous bronze statue of St. George at the Prague Castle, which was created in 1373, represents an advanced stage of this process

Creusa, Ascanius, and Aeneas in Renaissance Prague

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Characterization of concrete failure behavior: a comprehensive experimental database for the calibration and validation of concrete models

Concrete is undoubtedly the most important and widely used construction material of the late twentieth century. Yet, mathematical models that can accurately capture the particular material behavior under all loading conditions of significance are scarce at best. Although concepts and suitable models have existed for quite a while, their practical significance is low due to the limited attention to calibration and validation requirements and the scarcity of robust, transparent and comprehensive methods to perform such tasks. In addition, issues such as computational cost, difficulties associated with calculating the response of highly nonlinear systems, and, most importantly, lack of comprehensive experimental data sets have hampered progress in this area. This paper attempts to promote the use of advanced concrete models by (a) providing an overview of required tests and data preparation techniques; and (b) making a comprehensive set of concrete test data, cast from the same batch, available for model development, calibration, and validation. Data included in the database ‘http://www.baunat.boku.ac.at/cd-labor/downloads/versuchsdaten’ comprise flexure tests of four sizes, direct tension tests, confined and unconfined compression tests, Brazilian splitting tests of five sizes, and loading and unloading data. For all specimen sets the nominal stress–strain curves and crack patterns are provided.Austria. Ministry of Environment, Youth and FamilyAustria. National Foundation for Research, Technology and DevelopmentUnited States. Dept. of Transportation (Grant No. 20778

Fully inkjet-printed cuo sensor on flexible polymer substrate for alcohol vapours and humidity sensing at room temperature

This work focuses on an inkjet-fabricated sensor based on copper oxide nanostructured particles on polymer flexible substrate for the sensing of alcohol vapours and humidity at room temperature. Nanoparticles were prepared by a microwave-assisted solvothermal sealed vessel synthesis method. The ink composition was developed on the basis of viscosity and surface tension optimization by the addition of polymeric steric surfactant and dispersant. The printing process was optimized with the help of non-dimensional criteria. Silver nanoink was used for the printing of an interdigitated pattern on a PET substrate which was overprinted by the copper oxide ink, thus obtaining a flexible flat sensor. Material design and all fabrication steps of the sensor respected the temperature limitation given by the thermal stability of the polymer substrate. Printed layers and motifs were characterized microscopically and by resistance measurement. The effectiveness of the prepared sensor was demonstrated and studied by measuring the response to saturated vapours at room temperature. The sensing layer showed the opposite resistance response to stimuli than expected for the well-known p-type sensing mechanism of CuO sensors operated at high temperatures. In addition to vapour sorption, condensation and desorption influencing electron, proton and ionic conductivity, manifestation of another mechanism was observed and an explanation suggested in terms of the electrochemical mechanism. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.Ministry of Education, Youth and Sports of the Czech Republic-Program NPU I [LO1504]; Internal Grant Agency of Tomas Bata University in Zlin [IGA/CPS/2015/006, IGA/CPS/2016/007, IGA/CPS/2017/008

THE DYNAMICS OF HAEMOSTATIC PARAMETERS IN ACUTE PSYCHOTIC PATIENTS: A ONE-YEAR PROSPECTIVE STUDY

Background: The primary goal of the present study was to replicate our previous finding of increased coagulation and thrombocytes activity in drug-naïve psychotic patients in comparison with healthy controls and ascertain whether the blood levels of thrombogenesis markers further increase over the course of a consecutive one-year antipsychotic treatment. Subjects and methods: We investigated the plasma levels of markers indicating activation of coagulation (D-dimers and Factor VIII) and platelets (soluble P-selectin, sP-selectin) in an antipsychotic-naive group of nineteen men and seventeen women with acute psychosis (age 28.1±8.0 years, body mass index 22.6±4.2), and thirty-seven healthy volunteers matched for age, gender and body mass index. In the patient group, we repeated these assessments after three months and again after one year of antipsychotic treatment. Results: D-dimers (median 0.38 versus 0.19 mg/l; p=0.00008), factor VIII (median 141.5% versus 110%; p=0.02) and sPselectin (median 183.6 versus 112.4 ng/ml; p=0.00005) plasma levels were significantly increased in the group of patients with acute psychosis prior to treatment compared with healthy volunteers. The plasma levels of sP-selectin varied significantly (p=0.016) in the course of the one-year antipsychotic treatment, mainly between 3 and 6 months after start of therapy. The plasma levels of D-dimers and factor VIII did not change significantly, D-dimers remained elevated in contrast to the healthy controls. Conclusions: Patients with acute psychosis had increased levels of markers of thrombogenesis in comparison to the healthy volunteers. The haemostatic parameters also remained elevated during the one-year antipsychotic treatment

Non-local energetics of random heterogeneous lattices

In this paper, we study the mechanics of statistically non-uniform two-phase elastic discrete structures. In particular, following the methodology proposed in (Luciano and Willis, Journal of the Mechanics and Physics of Solids 53, 1505-1522, 2005), energetic bounds and estimates of the Hashin-Shtrikman-Willis type are developed for discrete systems with a heterogeneity distribution quantified by second-order spatial statistics. As illustrated by three numerical case studies, the resulting expressions for the ensemble average of the potential energy are fully explicit, computationally feasible and free of adjustable parameters. Moreover, the comparison with reference Monte-Carlo simulations confirms a notable improvement in accuracy with respect to approaches based solely on the first-order statistics.Comment: 32 pages, 8 figure