Quality of several vitrified radwastes specimens was demonstrated on their hydrolytic resistance. The type of water corrosion mechanism and structural features were also elucidated. The time dependence of the corrosion process proved two subsequent mechanisms of water attack. The first stage is controlled by diffusion. Later the silicate matrix is damaged and its surface layer dissolved. Ultimately, the quality of glass is evaluated from the point of view of possible radioactivity releases.
Motion of particles with air resistance (e.g. horizontal and inclined throwing) plays an important role in many technological processes in agriculture, wood industry and several other fields. Although, the basic equation of motion of this problem is well known, however, the solutions for practical applications are not sufficient. In this article working diagrams were developed for quick estimation of the throwing distance and the terminal velocity. Approximate solution procedures are presented in closed form with acceptable error. The working diagrams provide with arbitrary initial conditions in dimensionless form of general validity.
Authors:S. M. A. El-Gamal, F. S. Hashem and M. S. Amin
environmental factors. Properties of aggregate, cement paste and aggregate–cement paste bond, and their thermal compatibility between each other greatly influence the resistance of concrete. On the other hand, environmental factors such as heating rate, duration
Authors:D. Chaliampalias, G. Vourlias, E. Pavlidou and K. Chrissafis
The wide application of tool steels is attributed to their special mechanical properties that are required in many mechanical devices. Moreover, the oxidation resistance at high temperatures is also required in
Authors:A. Swiderski, A. Wojtal, P. Muras, A. Mikulko, S. Wrobel and H. Koloczek
method was used to study phase transitions in Rhododendron
L. leaf tissues caused by temperatures below the freezing point of water.
The curves show several stages of water crystallisation, demonstrating that
these processes do not occur simultaneously in various types of cell organelles.
Temperatures and enthalpies of the phase transitions were determined and significant
changes were found in the DSC curves when the sample was repeatedly subjected
to sub-zero temperature cooling and heating. Also, frost resistance of the
same rhododendron taxons was studied by conductometric analysis and the DSC
results were compared with the data from other laboratory studies.
Results of theoretical and experimental investigations of the thermal behaviour of InGa-AsP/InP laser diodes with a ridge-waveguide structure are presented. It is shown that, in contrast to GaAlAs/GaAs laser diodes, most of the heat flux is carried through the InP-substrate, less than 1/4 through the ridge. The temperature rise in the active region was determined and the thermal resistance calculated for various structure and bond parameters. The theoretical and experimental results fit very well. The change of the thermal resistance compared to a norm value of 67 K/W with variation of structure parameters is discussed. It is strongly affected by the device length, the ridge width and the bonding parameters.
processes, especially the oxidation resistance [ 12 , 13 ]. The simulation procedure to enable precise evaluation of lubricant viscosity was developed by Konno et al. [ 14 ]. The authors used computational chemistry to accelerate the design of lubricants
Authors:A. Varesano, C. Tonin, F. Ferrero and Marinella Stringhetta
Electro-conducting doped polypyrrole was deposited by in situ oxidative polymerisation on PET non-wovens. Thermal properties were evaluated by means of DSC and TG in nitrogen and air.
Flame resistance tests reveal that coated PET fibres resist to direct contact with fire. By thermal analysis, it was found
that PPy reduces the temperature at which thermo-oxidative degradation of PET occurs. Polypyrrole-coated PET non-wovens were
heated above the melting point of PET for 30 min. After the heating the fibres become brittle and frail, but SEM observations
revealed that they maintained their fibrous shape. A loss of chlorine was found because of intense heating.
One of the principal uses of supersulfated cement has been for structures exposed to sea water and sulfate bearing ground
waters. The resistance to such environments has been related to the absence of calcium hydroxide and the combination of much
of the free alumina into ettringite during hydration. This paper reports the resistance of SSC to sulfate solutions in which
ettringite has been decomposed. Prism samples were subjected to initial water storage at 25°C for both 28 days and 6 months.
Samples were also cured for 6 months at 95°C and at both 11% and 100% R.H. The control samples of 28 days were compared with
the 6 months samples of a more mature undecomposed SSC paste. After curing the prisms were measured and all the samples were
immersed in three sulfate solutions (0.7M Na2SO4 , 0.7M MgSO4 and saturated CaSO4), and water at the same time. Measurements of linear expansion over 6 months were carried out. Core and surface material
following immersion was examined by DTG and XRD. The study indicated that SSC is resistant to sodium and calcium sulfate solutions.
Strong magnesium sulfate solutions decomposed the samples under all conditions. A possible mechanism for this attack is suggested.