Showing papers by "Polytechnic University of Valencia published in 1984"

Effect of the cooling rate in the formation of glass on the α and β relaxations of some amorphous polymers

Abstract: It has been observed in dynamic mechanical measures that the range of temperatures in which relaxation properties are affected by the diminishing of the free volume has, as a lower limit the temperature at which the maximum of G″ or tgδ, corresponding to the β relaxation, occurs. In dielectric measures on polymers in which the β relaxation is not predominant over the α relaxation, this temperature range is scarcely affected by changes in frequency, whereas the peak shifts according to its activation energy. This fact leads to the conclusion that the decrease in free volume due to a slow cooling from a temperature above Tg mainly affects mobility of the main chains under Tg, without disturbing the groups that give rise to the secondary relaxations.

Reduction of Pumping Losses By the Use of a Variable Valve Timing System

Abstract: In this paper, the advantages of using variable valve timing systems in order to decrease pumping losses are outlined. In the first part of the paper, the reduction of pumping losses through regulation of the engine load rate, by varying the time that the intake valve remains open, is justified by reasoning on ideal diagrams. In the second part, a proposed system to vary the valve timing diagram is described. This system consists mainly of a four-bar mechanism. Finally, the advantages and disadvantages of the proposed system are considered in the real engine by means of a calculation model. The conclusion is that with this system it is possible to obtain important improvements in the effective efficiency of the engine running at partial load.

Fertilization of orange trees with sulfur-coated urea. Nitrogen levels in leaves and fruits

Abstract: The effect of one application of the slow-release fertilizer, sulfur-coated urea, on the nitrogen level in leaves, fruit and bark of Washington Navel orange trees was studied during the different periods of the annual vegetative cycle, in comparison with two annual applications of the fertilizer ammonium nitrosulphate.

The multiplicity-generating function of hadron-nucleus interactions at high energies

Abstract: Some facts of QCD and dual topologicla unitarization have been used together with standard nuclear-optics techniques and the Chapman-Kolgomorov methodology, to build a model which allows us to know the multiplicity-generating function of high-energy hadron-nucleus collisions. The model has been applied to compute the average multiplicity and the variance for several high-energy interactions. The agreement with the experimental results can be considered as excellent. Some interesting conclusions are obtained about the space-time development of hadron-nucleus interactions.