1,498 research outputs found
Complete asymptotic expansions for eigenvalues of Dirichlet Laplacian in thin three-dimensional rods
We consider Dirichlet Laplacian in a thin curved three-dimensional rod. The
rod is finite. Its cross-section is constant and small, and rotates along the
reference curve in an arbitrary way. We find a two-parametric set of the
eigenvalues of such operator and construct their complete asymptotic
expansions. We show that this two-parametric set contains any prescribed number
of the first eigenvalues of the considered operator. We obtain the complete
asymptotic expansions for the eigenfunctions associated with these first
eigenvalues
Simultaneous fNIRS and thermal infrared imaging during cognitive task reveal autonomic correlates of prefrontal cortex activity
Functional Near Infrared-Spectroscopy (fNIRS) represents a powerful tool to non-invasively study task-evoked brain activity. fNIRS assessment of cortical activity may suffer for contamination by physiological noises of different origin (e.g. heart beat, respiration, blood pressure, skin blood flow), both task-evoked and spontaneous. Spontaneous changes occur at different time scales and, even if they are not directly elicited by tasks, their amplitude may result task-modulated. In this study, concentration changes of hemoglobin were recorded over the prefrontal cortex while simultaneously recording the facial temperature variations of the participants through functional infrared thermal (fIR) imaging. fIR imaging provides touch-less estimation of the thermal expression of peripheral autonomic. Wavelet analysis revealed task-modulation of the very low frequency (VLF) components of both fNIRS and fIR signals and strong coherence between them. Our results indicate that subjective cognitive and autonomic activities are intimately linked and that the VLF component of the fNIRS signal is affected by the autonomic activity elicited by the cognitive task. Moreover, we showed that task-modulated changes in vascular tone occur both at a superficial and at larger depth in the brain. Combined use of fNIRS and fIR imaging can effectively quantify the impact of VLF autonomic activity on the fNIRS signals
Evaluating collapse fragility curves for existing buildings retrofitted using seismic isolation
Few studies have investigated so far the collapse capacity of buildings with base-isolation. In such studies, preliminary considerations have been drawn based on a number of assumptions regarding: (i) the methodology used for assessing the collapse capacity, (ii) the collapse conditions and failure modes assumed for both superstructure and isolation system, and (iii) the numerical modeling assumptions. The main results pointed out that the collapse conditions of base-isolated buildings may occur for intensity levels slightly higher than those associated with the design earthquake. In this paper, further developments are made through the use of enhanced models for the description of the behavior of a rubber-based isolation system and the assumption of more rational collapse conditions. Collapse fragility functions, in terms of mean and dispersion values, are proposed for two archetypes representative of existing buildings retrofitted using the seismic isolation technique. The collapse margin ratio (median collapse capacity Sa, C, namely the spectral acceleration associated to a probability of exceedance equal to 50%, divided by the design spectral acceleration at the collapse prevention limit state) has been evaluated for each examined case-study. Values ranging from 1.10 to 1.45 were found
Preliminary analysis of Skylab RADSCAT results over the ocean
Preliminary observations at 13.9 GHz of the radar backscatter and microwave emission from the sea were analyzed using data obtained by the radiometer scatterometer on Skylab. Results indicate approximately a square-law relationship between differential scattering coefficient and windspeed at angles of 40 deg to 50 deg, after correction for directional effect, over a range from about 4 up to about 25 meters/sec. The brightness temperature response was also observed, and considerable success was achieved in correcting it for atmospheric attenuation and emission. Measurements were made in June, 1973, over Hurricane Ava off the west coast of Mexico and over relatively calm conditions in the Gulf of Mexico and Caribbean Sea
Preliminary report on Skylab S-193 Radscat measurements of Hurricane Ava
The author has identified the following significant results. The Skylab RADSCAT instrument S-193 was operated on 6 June 1973 while the spacecraft flew past Hurricane Ava in the eastern Pacific Ocean. Scatterometer returns at all polarizations and radiometer measurements were obtained from a section through the storm with winds up to 48 knots at 52 deg incident angle and 35 knots at 45.5 deg incident angle. These first hurricane scatterometer measurements indicate reasonable correlation between wind speed and backscatter, with horizontal response much stronger than the vertical response at 52 deg. Each of the sections through the hurricane contains an as yet unexplained dip in cross section at a point 200 to 300 km prior to passing the eye. The response at a point where the radiometer signal's dramatic increase indicates strong rain is also accompanied by a strong increase in the backscattered signal. No attempt has been made to make a thorough correlation of radiometric response with wind speed, but the atmospheric contribution to the radiometer signal is quite apparent
The shadow of light: further experimental evidences
We report the results of a double-slit-like experiment in the infrared range,
which confirm those of a previous one by evidencing an anomalous behaviour of
photon systems under particular (energy and space) constraints. These outcomes
(independently confirmed by crossing photon beam experiments in both the
optical and the microwave range) apparently rule out the Copenhagen
interpretation of the quantum wave, i.e. the probability wave, by admitting an
interpretation in terms of the Einstein-de Broglie-Bohm hollow wave for
photons. Moreover, this second experiment further supports the interpretation
of the hollow wave as a deformation of the Minkowski space-time geometry
A simplified approach for the seismic loss assessment of rc buildings at urban scale: The case study of Potenza (Italy)
Comprehensive methodologies based on a fully probabilistic approach (i.e., the performance- based earthquake engineering approach, PBEE), represent a refined and accurate tool for the seismic performance assessment of structures. However, those procedures are suitable for building-specific evaluations, appearing extremely time-consuming if applied at the urban scale. In the proposed contribution, simplified loss assessment procedure will be applied at the urban scale with reference to the residential building stock of the center of Potenza. After the identification of the main reinforced concrete (RC) structural typologies and the definition of specific archetype building numerical models, the direct estimation of expected annual loss (DEAL) methodology will be applied to derive the EAL (i.e., expected annual loss) of RC buildings, deriving information on the effectively seismic quality (or seismic resilience) of the aforementioned built heritage at urban scale. Similarly, the monetary losses associated with downtime are evaluated. Preliminary considerations on the socio-economic effects of seismic scenarios on the territorial scale are also proposed
Monitoring the sprouting process of wheat by non-conventional approaches
Controlled wheat sprouting is a useful process to achieve the perfect balance between nutritional advantages and technological performance. This study aims at developing a methodology for evaluating wheat sprouting by using a portable NIR device directly on kernels. Wheat kernels were germinated up to 72\u202fh with wet kernels being collected after 24, 36, 48, 60 and 72\u202fh and analysed directly or after drying by a MicroNIR in the spectral range of 950\u20131650\u202fnm. Wholegrain and refined flours from sprouted kernels were investigated for chemical composition, enzymatic activities, starch pasting properties, and gluten aggregation kinetics. Principal Component Analysis (PCA) on the whole dataset derived from chemical composition and technological analyses revealed that the main changes occurred within the first 48\u202fh. PCAs on spectral data, both from wet and dried kernels, assessed the effect of sprouting time, both on starch and protein fractions, as observed by conventional analyses on flour.
Thus, a NIR portable device can be implemented directly on wet kernels to determine the stage of sprouting, skipping both the drying and refinement steps. Implementing this approach could help the food industry in standardizing and monitoring the sprouting process, delivering novel cereal-based products with guaranteed and consistent characteristics
Optical Guidance System /OGS/ for rendezvous and docking Final report
Optical guidance system for Apollo rendezvous and dockin
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