Results show that in the formation of the microkeratome flap, collagen fibers are severed and minimal biomechanical loading is distributed through the flap. Corneal biomechanical integrity is compromised after microkeratome incisions.
M onitoring of the particles formed during carbon dioxide laser cutting of thin (2 mm) mild steel plate was undertaken to investigate the effect of processing parameters and melt removal mechanisms on the cut quality. The airborne particles ( 40 mm) formed during cutting were captured and the particle diameter distribution was measured using a laser diffraction method and examined using scanning electron microscopy (SEM ) analysis. The particles formed were spherical and found to range from micrometres to millimetres in diameter with a monomodal distribution for the airborne fraction. It was found that the airborne micrometre particle diameter range had a mean particle diameter that was directly related to the process quality measurands of cut edge surface nish, cut width and heat-affected zone (H AZ) width.
This article examines the particles formed during optimized laser scabbling of concrete in order to help determine an effective filtration strategy for the process. The laser scabbling technique has been developed for noncontact removal of radioactive contaminated surface concrete layers. Surface layer removal is effected using a high power carbon dioxide laser beam to generate stresses in the substrate (caused by temperature gradients and dehydration) which break up the surface. The material removed will be contaminated with radionuclides and its efficient collection must be ensured to prevent the escape of radioactive contaminated particles. The filtration methods selected depend on the size of the particles produced and transport characteristics in an airflow. The particles removed were examined using a laser diffraction particle sizer (for particles below 80 μm physical diameter) and sieving (above 150 μm physical diameter) to determine the particle size distribution. Scanning electron microscope (SEM) analysis was used to identify the components present. The study found that particles removed were constituents of the parent concrete, there were no signs of melting and a small volume fraction (less than 1%) of sub-100 μm physical particle diameter. Particles with aerodynamic diameters under 100 μm are airborne and those between 1 and 30 μm are inhaled into the thoracic and bronchial tracts and lungs. Efficient filtration is required to capture these particles. However, filtration is difficult in the 0.1–1 μm aerodynamic diameter range, which comprises only 0.02% by volume of the removed material. It is considered that laser scabbling of concrete using this method will produce no additional risks than the use of other surface removal mechanisms.
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