Calibration and comparison of concrete models with respect to experimental data

At the beginning of the 21st century, civil engineers more than ever face the often-contradictory demands for designing larger, safer and more durable structures at a lower cost and in shorter time. Concrete has been used for many centuries as a safe and durable building material. Two of the main advantages of concrete are its high compressive strength and that it can be cast on the construction site into a variety of shapes and sizes. Many different constitutive models have been developed to fulfill the above mentioned requirements and describe/predict the behavior and failure of concrete. The never ending challenge for engineers is to choose and set up the appropriate material model for the modeling of structures or structural elements. Therefore, the primary objective of the present research is to calibrate, validate and compare different constitutive models with respect to an extensive set of experimental data. Depending on the application and availability of data, the expected prediction quality of the available models may vary significantly. The studied material models include the microplane models M4 and M7, the damage plasticity models available in commercial (ATENA) or open source (OOFEM) finite element codes, e.g. the Grassl-Jirasek material model. Moreover, the Lattice-Discrete-Particle- Model (LDPM), implemented in the solver MARS, is utilized. We present a comparison of these models with regard to the number of input parameters, their physical meaning, the ease of calibration and their predictive capabilities by utilizing a large set of experimental data derived from specimens, cast from the same batch. All models are calibrated using three mean value nominal stress-strain curves obtained from a notched three-point bending, uniaxial compression and compression under passive confinement test. The calibrated numerical models are then used to predict the results of the remaining experiments, i.e. 3-point bending tests of 4 sizes with various notch depths, splitting tests of 5 sizes, direct tensions tests and torsion tests. These data then serve to assess the prediction quality of the models

Comparison of 30 THz impulsive burst time development to microwaves, H-alpha, EUV, and GOES soft X-rays

The recent discovery of impulsive solar burst emission in the 30 THz band is raising new interpretation challenges. One event associated with a GOES M2 class flare has been observed simultaneously in microwaves, H-alpha, EUV, and soft X-ray bands. Although these new observations confirm some features found in the two prior known events, they exhibit time profile structure discrepancies between 30 THz, microwaves, and hard X-rays (as inferred from the Neupert effect). These results suggest a more complex relationship between 30 THz emission and radiation produced at other wavelength ranges. The multiple frequency emissions in the impulsive phase are likely to be produced at a common flaring site lower in the chromosphere. The 30 THz burst emission may be either part of a nonthermal radiation mechanism or due to the rapid thermal response to a beam of high-energy particles bombarding the dense solar atmosphere.Comment: accepted to Astronomy and Astrophysic

Eritrograma e bioquímica do plasma da arraia Paratrygon aiereba (Chondrichthyes: Potamotrygonidae) do Arquipélago Mariuá, médio Rio Negro, Amazonas.

Resumo simples

Morfologia das células sanguíneas do jacaré-tinga Caiman crocodilus crocodilus Linnaeus, 1758 (Crocodylia, Alligatoridae).

Resumo simples

Comparison of the effects of anticoagulants used in blood collection to determine blood parameters of free-living stingrays from the Potamotrygon genus (Elasmobranchii: Potamotrygonidae).

This study assessed the effectiveness of three anticoagulants in blood parameters of "cururu" stingrays Potamotrygon cf . histrix. Blood from ten individuals were collected and diluted with anticoagulants EDTA 5% and 10%, heparin 2500 and 5000 UI and sodium citrate 3.2%. A blood sample without anticoagulant was also evaluated. The blood of samples without anticoagulant and with sodium citrate 3.2% coagulated in 20% and 30% of the cases, respectively. Clumps of cells were observed during erythrocyte counting in 30% of samples with EDTA 10%, 40% of samples with heparin 2500 IU and 60% of samples with heparin 5000 IU. No alterations were observed on the erythrogram of "cururu" stingrays with different anticoagulants, the values of plasma glucose were similar in all groups and total protein levels were lower in the samples with EDTA 5% and 10%. The use of sodium citrate 3.2% is not recommended for blood sample conservation of Potamotrygon cf . histrix. stingrays, but anticoagulants did not affect the parameters analyzed in the determination of plasma glucose and erythrogram. Therefore , these results indicate that in order to blood coagulation the samples should be collected directly with any of these anticoagulants concentrations