الفهرس 
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Abstract
The present study is subdivided into two parts ~The first part deals with
the study of the effect of the laser pulse shape and multipulses on the
development of the temporal and spatial temperature distribution in a semiinfinite
target and a thin film coated on a semi-infinite substrate.
The second part is devoted to solve the problem of melting a thin
film coated on a semi-infinite substrate subjected to a given laser pulse
profile. In both parts it is assumed that the absorption coefficient of the
cooled irradiated surface of the target is temperature dependent. The obtained
results from the fitst part show, for an Ai-semi-infmite target and an Ai-thin
film coated on a semi-infinite glass substrate , that the dependence of the
surface absorption coefficient on the temperature changes the temporal and
spatial temperature distribution markedly , while the cooling plays a minor
role and can be neglected. The results also show that, for all laser temporal
pulse profiles except the square pulse , the surface temperature exhibits a
maximum. These maxima occur at different times after reaching the laser
pulse profile its maximum value. The penetration depth of the temperature
determined at the end of the laser pulse is found to be a ftmction of the laser
pulse duration and is practically independent of its temporal profile.
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In the second part of the study , the pulse duration of the laser is
subdivided into three parts :1) The first deals with the heating process up to
the melting point of the target. 2) The second part induces melting with a
constant temperature distribution in the molten layer and lasts up to the time
at which the film is completely molten. 3)The third part of the pulse is
responsible for heating the configuration up to the point of evaporation of the
liquidified film. For an A/-layer coated on a semi-infmite glass substrate and
subjected to a given laser pulse profile, the computations show that, the time
of meltine , full liquidification and that at which the evaporation occurs,
increases as the surface absorption becomes temperature independent and
cooling is considered. Also in this part it is found that the effect of the
dependence of the surface absorption coefficient on temperature is greater
than that of cooling. The thermal penetration depth measured from the front
surface of the configuration up to the point at which the temperature reaches
I II 00 from the front surface temperature is practically independent of the
absorption coefficient.