Cement saving by revision of the standard conversion factor in the compression testing of concrete

1971 ◽  
Vol 5 (4) ◽  
pp. 369-374
Author(s):  
K. V. Alekseev
Author(s):  
W. M. Sherman ◽  
K. M. Vedula

The strength to weight ratio and oxidation resistance of NiAl make this ordered intermetallic, with some modifications, an attractive candidate to compete with many superalloys for high temperature applications. Recent studies have shown that the inherent brittleness of many polycrystalline intermetallics can be overcome by micro and macroalloying. It has also been found that the high temperature mechanical properties of NiAl can be enhanced through the addition of Nb by powder metallurgical techniques forming a dispersed second phase through interdiffusion in a polycrystalline matrix. A drop in the flow stress is observed however in a NiAl-2 at.% Nb alloy after 0.2 % strain during constant strain rate hot compression testing at 1025°C. The object of this investigation was to identify the second phase and to determine the cause of the flow stress drop.


2011 ◽  
Vol 131 (3) ◽  
pp. 329-334
Author(s):  
Masakazu Higashiyama ◽  
Ken-ichi Akiyama ◽  
Teruhiko Maeda ◽  
Shuhei Nakamura ◽  
Hiro Umemura ◽  
...  

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2165
Author(s):  
Sam Hamels

The European Union strives for sharp reductions in both CO2 emissions as well as primary energy use. Electricity consuming technologies are becoming increasingly important in this context, due to the ongoing electrification of transport and heating services. To correctly evaluate these technologies, conversion factors are needed—namely CO2 intensities and primary energy factors (PEFs). However, this evaluation is hindered by the unavailability of a high-quality database of conversion factor values. Ideally, such a database has a broad geographical scope, a high temporal resolution and considers cross-country exchanges of electricity as well as future evolutions in the electricity mix. In this paper, a state-of-the-art unit commitment economic dispatch model of the European electricity system is developed and a flow-tracing technique is innovatively applied to future scenarios (2025–2040)—to generate such a database and make it publicly available. Important dynamics are revealed, including an overall decrease in conversion factor values as well as considerable temporal variability at both the seasonal and hourly level. Furthermore, the importance of taking into account imports and carefully considering the calculation methodology for PEFs are both confirmed. Future estimates of the CO2 emissions and primary energy use associated with individual electrical loads can be meaningfully improved by taking into account these dynamics.


2021 ◽  
Vol 11 (7) ◽  
pp. 2984
Author(s):  
Pietro Croce ◽  
Paolo Formichi ◽  
Filippo Landi

In modern structural codes, the reference value of the snow load on roofs is commonly given as the product of the characteristic value of the ground snow load at the construction site multiplied by the shape coefficient. The shape coefficient is a conversion factor which depends on the roof geometry, its wind exposure, and its thermal properties. In the Eurocodes, the characteristic roof snow load is either defined as the value corresponding to an annual probability of exceedance of 0.02 or as a nominal value. In this paper, an improved methodology to evaluate the roof snow load characterized by a given probability of exceedance (e.g., p=0.02 in one year) is presented based on appropriate probability density functions for ground snow loads and shape coefficients, duly taking into account the influence of the roof’s geometry and its exposure to wind. In that context, the curves for the design values of the shape coefficients are provided as a function of the coefficient of variation (COVg) of the yearly maxima of the snow load on the ground expected at a given site, considering three relevant wind exposure conditions: sheltered or non-exposed, semi-sheltered or normal, and windswept or exposed. The design shape coefficients for flat and pitched roofs, obtained considering roof snow load measurements collected in Europe during the European Snow Load Research Project (ESLRP) and in Norway, are finally compared with the roof snow load provisions given in the relevant existing Eurocode EN1991-1-3:2003 and in the new version being developed (prEN1991-1-3:2020) for the “second generation” of the Eurocodes.


Author(s):  
Laurentiu Slatineanu ◽  
Andrei Mihalache ◽  
Liviu Andrusca ◽  
Adelina Hrituc ◽  
Margareta Coteata ◽  
...  
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