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Neural network (NN) models were evaluated for the prediction of suspended particulates with aerodynamic diameter less than 10-μm (PM) concentrations. The model evaluation work considered the sequential hourly concentration time series of PM, which were measured at El Hamma station in Algiers. Artificial neural network models were developed using a combination of meteorological and time-scale as input variables. The results were rather satisfactory, with values of the coefficient of correlation ( R) for independent test sets ranging between 0.60 and 0.85 and values of the index of agreement (IA) between 0.87 and 0.96. In addition, the root mean square error (RMSE), the mean absolute error (MAE), the normalized mean squared error (NMSE), the absolute relative percentage error (ARPE), the fractional bias (FB), and the fractional variance (FS) were calculated to assess the performance of the model. It was seen that the overall performance of model 3 was better than models 1 and 2. [ABSTRACT FROM AUTHOR]

Altogether 19 alloys of an Al-Mn-Fe system with compositions near to the Taylor phase and/or the decagonal quasicrystal were characterised by the x-ray diffraction and the energy-dispersive x-ray spectroscopy coupled with the scanning electron microscopy, after annealing at 1000 °C for 330 h. The obtained experimental results were used to propose a partial isothermal section at 1000 °C of the Al-Mn-Fe phase diagram. The ternary T-phase area of an untypical saddle shape was found to touch the Al-Mn binary one. The γ-phase was found to be stable between 2 and 30 at.% of Fe at 1000 °C and boundaries between γ- and γ-areas are expected to be located very close to the Al-Mn binary. [ABSTRACT FROM AUTHOR]

Partial isothermal sections of the Al-Co-Cu phase diagram at 800, 1020, and 1050 °C were proposed based on both literature data and own experimental results. By means of x-ray diffraction, electron backscattered diffraction, electron diffraction, high-resolution scanning electron microscopy, transmission electron microscopy, and energy dispersive x-ray spectroscopy altogether five phases (AlCo, m-AlCo, D, B2, and rapidly solidified liquid) were identified in a number of investigated alloys falling within compositional ranges AlCoCu. The single-phase area corresponding in the isothermal sections to the decagonal quasicrystalline phase (D) was found to reduce in size, and to shift to lower Cu and higher Al bulk contents, both with increasing temperature. The single-phase m and AlCo areas showed only small temperature-dependent changes in size and location. Moreover, an increase in temperature caused both a slow decrease of the copper solubility in B2 and an increase of the liquid stability. [ABSTRACT FROM AUTHOR]

Four low alloy steels with different contents of molybdenum and vanadium were investigated. The steels were annealed at 773, 793, 853, 873, 933, 973, and 993 K for 500, 1000, 3000, and 10000 h. Techniques of transmission electron microscopy and thermodynamic calculations (ThermoCalc) were used to characterise influence of the steel bulk composition and the annealing conditions on evolution of carbides M3C, M2C, M7C3, M23C6, M6C, and MC (M=metallic element). Changes in structure types and metal compositions of the carbides were characterised in detail. The work was done with the intention to obtain more information about the secondary phase evolution in low alloy steels used in energy industries. [ABSTRACT FROM AUTHOR]

The influence of both bulk vanadium content and aging conditions on the evolution of secondary phases in Cr-V low-alloy steels was studied. Three 0.1C-0.9Cr-V steels with different vanadium contents (0, 0.258, and 0.512 wt pct) were aged for 100 to 5,000 hours at 773, 853, 953, and 993 K. In the investigation, a limited experimental program (transmission electron microscopy (TEM)) was combined with credible thermodynamic predictions (ThermoCalc). Going out from the good agreement between the predicted and experimental results, behavior of the iron-rich M7C3 carbide in time-temperature scale was characterized. The influence of bulk vanadium content was determined on appearance of the M[sub3]C carbide in equilibrium, temperature of the M[sub7]C[sub3] carbide precipitation, metal compositions of M[sub3]C or M[sub7]C[sub3] carbides, and vanadium portion in the metallic part of the MX phase. [ABSTRACT FROM AUTHOR]

The present work evaluates the influence of the bulk carbon content (0.1, 0.006, and 0.005 wt pct) and tempering temperature (823, 853, and 913 K) on stability, chemical composition, and size of carbide particles in 540 ks tempered states of 2.6Cr-0.7Mo-0.3V steel. The scanning transmission electron microscopy/energy-dispersive X-ray spectroscopy (STEM/EDXS) and electron diffraction methods were used to analyze the carbide particles. A characteristic energy-dispersive X-ray (EDX) spectrum can be attributed to each of the identified carbides. The MC carbide is stable in all experimental states. The phase stability of Fe-Cr-rich carbides increased in the order ε, FeC → MC → MC, with tempering temperature increasing. In steels with higher carbon content tempered at low temperature, MC carbide was also noted. The MoC and MC carbides were not observed. It was shown that the decrease of the bulk carbon content has the same influence on the carbide phases stability as the increase of the bulk vanadium content at the unchanged Cr, Mo, C bulk contents and tempering temperature. Similarly, the decrease of tempering temperature has the same influence on the carbide phases stability as the decrease of the bulk Cr content at the unchanged V, Mo, and C bulk contents. [ABSTRACT FROM AUTHOR]