400 research outputs found
Characterizing Safety: Minimal Control Barrier Functions from Scalar Comparison Systems
Verifying set invariance has classical solutions stemming from the seminal work by Nagumo, and defining sets via a smooth barrier function constraint inequality results in computable flow conditions for guaranteeing set invariance. While a majority of these historic results on set invariance consider flow conditions on the boundary, this letter fully characterizes set invariance through minimal barrier functions by directly appealing to a comparison result to define a flow condition over the entire domain of the system. A considerable benefit of this approach is the removal of regularity assumptions of the barrier function. This letter also outlines necessary and sufficient conditions for a valid differential inequality condition, giving the minimum conditions for this type of approach. We also show when minimal barrier functions are necessary and sufficient for set invariance
Optical signal to noise ratio improvement through unbalanced noise beating in phase-sensitive parametric amplifiers
We investigate the beating of signal and idler waves, which have imbalanced signal to noise ratios, in a phase-sensitive parametric amplifier. Imbalanced signal to noise ratios are achieved in two ways; first by imbalanced noise loading; second by varying idler to signal input power ratio. In the case of imbalanced noise loading the phase-sensitive amplifier improved the signal to noise ratio from 3 to 6 dB, and in the case of varying idler to signal input power ratio, the signal to noise ratio improved from 3 to in excess of 20 dB
Challenges and pitfalls of antipsychotic prescribing in people with learning disability
No abstract available
Studies of a Lacustrine-Volcanic Mars Analog Field Site with Mars-2020-like Instruments
On the upcoming Marsâ2020 rover two remote sensing instruments, MastcamâZ and SuperCam, and two microscopic proximity science instruments, SHERLOC and PIXL, will collect compositional (mineralogy, chemistry, and organics) data essential for paleoenvironmental reconstruction. The synergies between and limitations of these instruments were evaluated via study of a Mars analog field site in the Mojave Desert, using instruments approximating the data that will be returned by Marsâ2020. A ground truth dataset was generated for comparison to validate the results. The site consists of a succession of clayârich mudstones of lacustrine origin, interbedded tuffs, a carbonateâsilica travertine deposit, and gypsiferous mudstone strata. The major geological units were mapped successfully using simulated Marsâ2020 data. Simulated MastcamâZ data identified unit boundaries and Feâbearing weathering products. Simulated SuperCam passive shortwave infrared and green Raman data were essential in identifying major mineralogical composition and changes in lacustrine facies at distance; this was possible even with spectrally downsampled passive IR data. LIBS and simulated PIXL data discriminated and mapped major element chemistry. Simulated PIXL revealed mmâscale zones enriched in zirconium, of interest for age dating. SHERLOCâlike data mapped sulfate and carbonate at subâmm scale; silicates were identified with increased laser pulses/spot or by averaging of hundreds of spectra. Fluorescence scans detected and mapped varied classes of organics in all samples, characterized further with followâon spatially targeted deepâUV Raman spectra. Development of dedicated organics spectral libraries is needed to aid interpretation. Given these observations, the important units in the outcrop would be sampled and cached for sample return
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