462 research outputs found
Photoacoustics Modelling using Amplitude Mode Expansion Method in a Multiscale T-cell Resonator
The photoacoustic (PA) effect consisting of the generation of an acoustic
signal based on the absorption of light has already demonstrated its potential
for various spectroscopic applications for both gaseous and solid samples. The
signal produced during photoacoustic spectroscopy (PAS) measurement is,
however, usually weak and needs to be amplified. This is achieved by using a
photoacoustic cell resonator where acoustic resonances are utilized to
significantly boost the signal. Therefore, a PA resonator has a significant
role in PAS measurement set-ups. When designing or optimizing a new PA
resonator, numerical methods are generally used to simulate the photoacoustic
signal generation. In this paper, the amplitude mode expansion (AME) method is
presented as a quick and accurate simulation tool. The method is used to
simulate the photoacoustic signal in a multi-scale T-cell resonator over a wide
frequency range. The AME method is based on eigenmode expansion and
introduction of losses by quality factors. The AME simulation results are
compared and analyzed against the results from the viscothermal method.
Reasonably good agreement is obtained between the two methods. However, small
frequency shifts in the resonances of the AME method are noted. The shifts are
attributed to the location of the dominant mode within the T-cell. The
viscothermal method is considered the most accurate method for simulating the
photoacoustic signal in small resonators. However, it is computationally very
demanding. The AME method provides a much faster simulation alternative. This
is particularly useful in the design and optimization of photoacoustic
resonators where numerical methods are preferred over experimental measurements
due to their speed and low cost.Comment: Comsol Conference 201
Evidence for Miocene subduction beneath the Alboran Sea (Western Mediterranean) from 40Ar/39Ar age dating and the geochemistry of volcanic rocks from holes 977A and 978A
Volcanic pebbles in gravels from Sites 977 and 978 in the Alboran Sea (western Mediterranean) were dated (using the 40Ar/
39Ar single-crystal laser technique) and analyzed for their major- and trace-element compositions (determined by X-ray fluorescence
and inductively coupled plasma-mass spectrometry). The samples range from basalts to rhyolites, and belong to the
tholeiitic, calc-alkaline, and shoshonitic series. Single-crystal and step-heating laser 40Ar/39Ar analyses of plagioclase, sanidine,
biotite, and amphibole phenocrysts from basaltic to rhyolitic samples indicate that eruptions occurred between 6.1 and 12.1 Ma.
The age data conform to the stratigraphy and agree with microfossil ages, when available. The major-element and compatible
trace-element data of samples with H2O < 4 wt% show systematic variations, consistent with fractionation of the observed phenocryst
phases (plagioclase, olivine, clinopyroxene, magnetite, hornblende, quartz, and biotite). The incompatible-element patterns
formed by normalizing to primitive mantle for all samples show spiked patterns with peaks generally at mobile elements
and troughs at immobile elements, in particular Nb and Ta. The calc-alkaline affinities and the incompatible-element systematics
are characteristic of subduction zone volcanism, which indicates that subduction occurred beneath the eastern Alboran from
6 to at least 12 Ma. We propose that the change in chemistry from calc-alkaline and potassic to sodic compositions between 5–
6 Ma reflects detachment of the subducting slab. Uplift of the Strait of Gibraltar, associated with this detachment, could have
caused the Messinian Salinity Crises
Blumenau e o ItajaĂ-Açu: requalificação da relação da cidade com o Rio
TCC (graduação) - Universidade Federal de Santa Catarina. Centro Tecnológico. Arquiteturasem resumo
A cidade de Blumenau e o rio ItajaĂ-Açú: uma proposta de requalificação da relação da cidade com o rio
TCC (graduação) - Universidade Federal de Santa Catarina. Centro Tecnológico. ArquiteturaTCC sem resumo
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