Publish in OALib Journal
APC: Only $99
This paper presents
a hierarchical Bayesian approach to the estimation of components’ reliability
(survival) using a Weibull model for each of them. The proposed method can be
used to estimation with general survival censored data, because the estimation
of a component’s reliability in a series (parallel) system is equivalent to the
estimation of its survival function with right- (left-) censored data. Besides
the Weibull parametric model for reliability data, independent gamma
distributions are considered at the first hierarchical level for the Weibull
parameters and independent uniform distributions over the real line as priors
for the parameters of the gammas. In order to evaluate the model, an example
and a simulation study are discussed.
The objective of this study was to develop an
experimental methodology for the extraction of polychlorinated biphenyls (PCBs)
from contaminated soil and wood material using the Soxhlet extraction method
and supercritical fluid technology. The sample PCB contents were quantified
using Gas Chromatography-Mass Spectrometry (GC/MS). Conventional
extractions of PCBs from soil samples showed higher extraction yields for
samples with the highest initial PCB levels and longest extraction times.
Specific PCBs yielded 74.0% - 78.3% removal using ethanol as the solvent. 91.0%
- 94.3% removal of the total PCB content was achieved using hexane as the solvent.
Supercritical fluid extraction of soil samples resulted in 50.0% - 70.5%
removal for specific PCBs and 57.3% removal of the total PCB content. For wood,
the use of Soxhlet extraction resulted in 87.0% - 94.0% removal for specific
PCBs and 95.0% - 96.3% removal of the total PCB content. Supercritical fluid
extraction of wood samples resulted in 91.1% - 95.0% removal of specific PCBs
and 95.1 % of the total PCB content.