1,398 research outputs found
CO2 isotope sensor using a broadband infrared source, a spectrally narrow 4.4 ÎŒm quantum cascade detector, and a Fourier spectrometer
We report a prototype CO2 gas sensor based on a simple blackbody infrared source and a spectrally narrow quantum cascade detector (QCD). The detector absorption spectrum is centered at 2260cmâ1 (4.4ÎŒm) and has a full width at half maximum of 200cmâ1 (25meV). It covers strong absorption bands of two spectrally overlapping CO2 isotopomers, namely the P-branch of 12CO2 and the R-branch of 13CO2. Acquisition of the spectral information and data treatment were performed in a Fourier transform infrared (FTIR) spectrometer. By flushing its sample compartment either with nitrogen, dry fresh air, ambient air, or human breath, we were able to determine CO2 concentrations corresponding to the different gas mixtures. Adetection limit of 500ppb was obtained in these experiment
Propositional update operators based on formula/literal dependence
International audienceWe present and study a general family of belief update operators in a propositional setting. Its operators are based on formula/literal dependence, which is more fine-grained than the notion of formula/variable dependence that was proposed in the literature: formula/variable dependence is a particular case of formula/literal dependence. Our update operators are defined according to the "forget-then-conjoin" scheme: updating a belief base by an input formula consists in first forgetting in the base every literal on which the input formula has a negative influence, and then conjoining the resulting base with the input formula. The operators of our family differ by the underlying notion of formula/literal dependence, which may be defined syntactically or semantically, and which may or may not exploit further information like known persistent literals and pre-set dependencies. We argue that this allows to handle the frame problem and the ramification problem in a more appropriate way. We evaluate the update operators of our family w.r.t. two important dimensions: the logical dimension, by checking the status of the Katsuno-Mendelzon postulates for update, and the computational dimension, by identifying the complexity of a number of decision problems (including model checking, consistency and inference), both in the general case and in some restricted cases, as well as by studying compactability issues. It follows that several operators of our family are interesting alternatives to previous belief update operators
Improvements in diffraction efficiency of gratings and microlenses with continuous relief structures
Limit of light coupling strength in solar cells
We introduce a limit for the strength of coupling light into the modes of
solar cells. This limit depends on both a cell's thickness and its modal
properties. For a cell with refractive index n and thickness d, we obtain a
maximal coupling rate of 2c*sqrt(n^2-1)/d where c is speed of light. Our method
can be used in the design of solar cells and in calculating their efficiency
limits; besides, it can be applied to a broad variety of resonant phenomena and
devices
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