RESUMEN
A laboratory cement quality analysis apparatus based on laser-induced breakdown spectroscopy (LIBS) has been developed for rapid analysis of cement composition and ratio values. In this paper, the overall structure, the optical system, the sample preparation process, as well as the spectral data analysis methods are introduced. The calibration model is established with internal standard method. A comparison as to the measurement results between LIBS and X-ray fluorescence spectrometry (XRF) has been made and being analyzed. It shows that by using the LIBS apparatus, the mean absolute error of CaO, SiO2, Al2O3, and Fe2O3 in cement raw materials is 0.46%, 0.25%, 0.13%, and 0.05%, respectively, while the mean absolute error of the ratio value such as KH, SM, and IM in cement clinker is 0.02, 0.05, and 0.04, respectively. The generated cement plasmas are verified to be in the local thermal equilibrium (LTE) condition by calculating both the plasma temperature and the electron density.
RESUMEN
Laser-induced breakdown spectroscopy (LIBS) as a rapid spectral analysis technology shows the outstanding application foreground and research value in coal quality on-line monitoring. In the practical application of this technology, the pulsed laser power fluctuation leads to the worse performance of long term stability, so a closed-loop feedback pulsed laser power locking device is set up, using laser power feedback signal to control and lock Nd:YAG laser output power. The laser power locking experiments are investigated in the same pre-set value with different splitting ratios, the different laser output power with the same proportion and the long time running modes. The results show that the beam split ration has little impact to the stability of the laser power, and the smaller split ration leads to the faster stabilization. This device can keep the output power of the pulsed laser being locked in the pre-set range for a long-term running, RSD values decrease from 2.4% of free-running to 1.1%.
RESUMEN
Because of the poor accuracy of the commonly used Boltzmann plot method and double-line method, the Boltzmann-Maxwell distribution combined with the Saha-Eggert formula is proposed to improve the measurement accuracy of the plasma temperature; the simple algorithm for determining the linewidth of the emission line was established according to the relationship between the area and the peak value of the Gaussian formula, and the plasma electron density was calculated through the Stark broadening of the spectral lines; the method for identifying the plasma local thermal equilibrium (LTE) condition was established based on the McWhirter criterion. The experimental results show that with the increase in laser energy, the plasma temperature and electron density increase linearly; when the laser energy changes within 127~510 mJ, the plasma electron density changes in the range of 1.30532X10(17)~1.87322X10(17) cm(-3), the plasma temperature changes in the range of 12586~12957 K, and all the plasma generated in this experiment meets the LTE condition threshold according to the McWhirter criterion. For element Al, there exist relatively few observable lines at the same ionization state in the spectral region of the spectrometer, thus it is unable to use the Boltzmann plane method to calculate temperature. One hundred sets of Al plasma spectra were used for temperature measurement by employing the Saha-Boltzmann method and the relative standard deviation (RSD) value is 0.4%, and compared with 1.3% of the double line method, the accuracy has been substantially increased. The methods proposed can be used for rapid plasma temperature and electron density calculation, the LTE condition identification, and are valuable in studies such as free calibration, spectral effectiveness analysis, spectral temperature correction, the best collection location determination, LTE condition distribution in plasma, and so on.
RESUMEN
In this article, the authors revisit a controversial issue in the bereavement field: Does one violent cause of death of a child influence parents' outcomes more than another? To address this question, we observed 173 parents prospectively 4, 12, 24, and 60 months after their children's deaths by accident, suicide, or homicide. Quantitative and qualitative research methods were used to examine the influence of three types of a child's violent death and time since death upon 4 parent outcomes (mental distress, post-traumatic stress disorder [PTSD], acceptance of the child's death, and marital satisfaction). The results showed a significant interaction for the bereavement Group x Time effect for acceptance of death, a significant main effect for time for all four outcomes, and a significant main effect for group (homicide) for PTSD. Nearly 70% of the parents reported that it took either 3 or 4 years to put their children's death into perspective and continue with their own lives; however the child's cause of death did not significantly influence parents' sense of timing in this regard. Clinical and research implications of the findings are discussed.
