Polyethylene (PE), is a polymer formed by carbon-carbon single bonds, is a very stable material with a very slow degradation rate. In this paper, polyethylene films bag type were exposed to UV-B radiation (320-280 nm) at different exposure times (2 to 12 days). The UV radiation effects on PE samples were characterized using infrared spectroscopy with attenuated total reflectance (ATR). The vinyl group formation indicates the PE degradation. These chemical groups have IR absorption in 900-1300 cm-1; additionally the degree of crystallinity increase with the increasing of the exposure time. The experiment showed significant changes in PE molecular structure.
Laser provides a high controllable and localized spot for soldering joint formation and this is a valuable tool in Sn/Pb
Soldering process on electronic industry, in recent years, laser beam welding has become an emerging welding
technique, the use of laser in welding area is a high efficiency method. A 60 Watts CO2 continuous laser was used on
this study, during welding experimental results indicated the laser could significantly improve speed and weld quality. In
this work, the welding interactions of CO2 laser with Sn/Pb wire have been investigated in details through varying the
energy ratios of laser. And at the same time, the effect of distance from laser spot to material.
We report the changes occurring in cement pastes irradiated by 10.6μm CO<sub>2</sub> laser at different stages
of hydration. Raman spectroscopy, X-rays and Scanning Electronic Microscopy (SEM) techniques
had been used to observe molecular structural changes. Intensity of cement paste Raman peaks after
laser irradiation was monitored in samples irradiated 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11 days after their
preparation. Applied laser power changed Raman peaks intensity at 187.5cm<sup>-1</sup>, 563cm<sup>-1</sup>, 695cm<sup>-1</sup>,
750cm<sup>-1</sup>, 897cm<sup>-1</sup>, 1042cm<sup>-1</sup> and 1159cm<sup>-1</sup> that corresponds to compounds already presents in
cement pastes. X ray diffraction and SEM images confirm the recrystalization of cement paste
compounds into new phases (alite and belite) after irradiation. The produced changes show a clear dependence on the applied laser power density and age of
In this work we quantified the effective UV radiation dose in orange and colorless polyethylene samples exposed to
weather in the city of Aguascalientes, Ags. Mexico. The spectral distribution of solar radiation was calculated using
SMART 2.9.5.; the samples absorption properties were measured using UV-Vis spectroscopy and the quantum yield was
calculated using samples reflectance properties. The determining factor in the effective UV dose is the spectral
distribution of solar radiation, although the chemical structure of materials is also important.
This work carries out a simulation of the absorption spectra on the IR of an untinted textile fiber manufactured with
polyacrylonitrile (PAN), obtained by calculating the Molecular Orbitals (MOs) and their associated energies based on the
semiempirical (AM1) Hartree-Fock (HF) model and compared with the experimental results obtained from a PAN textile
fiber with blue pigment by means of an IR FTIR Avatar Nicolete spectrophotometer.
This work presents an experimental study of the appearance of redness on the surface of the eye on PC users due to the
exposition to low frequency electromagnetic fields LF, VLF and ELF that VDTs with TRC monitors radiate, based on
the measurement of the level of pigmentation and temperature. The total of the samples was analyzed using digital
processing of images extracting the component of red color of the sclera.
We demonstrated that under the same ergonomics and operating conditions, TRC monitors cause a higher heating and
greater pigmentation in the users eyes as compared to LCD screens, due to the higher low frequency radiation.
The degradation of weather exposed linear low density polyethylene (LLDPE) specimens, with and without pigments, in
Aguascalientes City, Ags. Mexico, during 269 days, was studied. Spectroscopic methods, ultraviolet (UV) spectroscopy
and colorimetry, were used to determine the degradation of the specimens. The material used is not pure since they are
samples of finished product that contain additives such as anti-oxidants, stabilizers, catalysts. One of the samples
contains orange color pigment and the other sample is colorless. The plots describing the absorption bands attributable to
the polymeric material show a similar profile in both samples. The bands attributable to pigment do show a considerable
decrease in absorbance. The results suggest that the orange pigment has been degrading, as it can also be observed in the
color change, while the polymeric material doesn't show any degradation.
In this paper, we report preliminary results of molecular structural changes in cement and concrete caused by laser radiation at 10.6 μm. One of those structural changes is the generation of glazes. At low laser powers, the glazes are small and lined up while at high powers, the glazes are bigger and randomly distributed. In the not exposed to laser radiation concrete, the Raman spectrum presents weak peaks at 200 cm<sup>-1</sup>, 550 cm<sup>-1</sup>, 700 cm<sup>-1</sup>, 750 cm<sup>-1</sup> and 1 150 cm<sup>-1</sup>. However, these peaks are amplified by laser exposure and other peaks appear at 800 cm<sup>-1</sup> and 1050 cm<sup>-1</sup>. The intensity of all the peaks is dependent on laser radiation power.
In this work a numeric analysis is carried out to calculate the thermal lens effect in the stability of a barside-pumped-resonator at 808 nm. The active medium is a Nd:YVO<sub>4</sub> crystal. It is demonstrated that the thermal effects produced by the radiative process, in certain conditions can take one of the planes to a non consistency, having as a consequence an oscillator that will work in intermittent form.
We present an experimental arrangement based on a Michelson interferometer, which uses a He-Ne laser as a source of illumination to obtain a pattern of fringes starting from a beat of the heart simulated by a computer. Of the pattern of fringes the original sign is reconstructed and is compared with the simulation of the heart beat.