1,837 research outputs found
Simulating radiometric observations of cylindrically-shaped precipitation along Earth-satellite microwave links
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Simulation of radiometric and attenuation measurements along earth-satellite links in the 10- to 50- GHz band through horizontally-finite convective raincells
No full textAn iterative solution is illustrated of the three-dimensional radiative transfer
equation for a horizontally finite and vertically inhomogeneous precipitating cloud. The
method is applied to modeling a convective rain cell of cylindrical shape, characterized by
spherical raindrops having a negative-exponential drop size distribution. The realistic
model also takes into account the presence of a cloud and an ice layer above the rain cell
itself. The simulated brightness temperature, the mean radiative temperature, and the
path attenuation are evaluated in a three-dimensional geometry from a surface
observation point in order to simulate a ground-based station with a beacon receiver and
a multichannel radiometer. Numerical results are shown to illustrate the potential of the
proposed model for different sets of frequency channels, observation geometries, cloud
sizes and types, and precipitation intensities. After generating a large data set by varying
the relevant rain cell parameters, regression analysis is applied to derive a statistical
estimation of the total path attenuation from surface rain rate and ground-based
radiometric measurements together with the frequency scaling factors for cumuliform
clouds in the 10- to 50-GHz band
On the use of ground-based multi-frequency microwave radiometer for precipitation and radio-propagation parameter retrieval
No full textNeural-network approach to ground-based passive microwave estimation of precipitation intensity and extinction
No full textA physically-based passive microwave technique is proposed to estimate precipitation intensity and extinction from ground. Multi-frequency radiometric measurements are inverted to retrieve surface rain rate, columnar precipitation contents and rainfall microwave extinction. A new inversion methodology, based on an artificial neurat-network feed-forward algorithm, is evaluated and compared against a previously developed regression technique. Both retrieval techniques are trained by numerical simulations of a radiative transfer model applied to microphysically-consistent precipitating cloud structures. Cloud microphysics is characterized by using parameterized hydrometeor drop size distribution, spherical particle shape and dielectric composition. The radiative transfer equation is solved for plane-parallel seven-layer structures, including liquid, melted, and ice spherical hydrometeors. The proposed neural-network inversion technique is tested and compared with the regression algorithm on synthetic data in order to understand their potential and to select the best frequency set for rainfall rate, columnar contents and extinction estimation. Available ground-based radiometric measurements at 13.0, 23.8, and 31.6 GHz are used for experimentally testing and comparing the neural-network retrieval algorithm. Comparison with rain gauge data and rain extinction measurements, derived from three satellite beacon channels at 18.7, 39.6, and 49.5 GHz acquired at Pomezia (Rome, Italy), are performed and discussed for a selected case of light-to-moderate rainfall. (c) 2005 Elsevier B.V. All rights reserved
Lo sciopero contro le guerre come forma di accoglienza. Riflessioni introduttive a un’inchiesta sulla solidarietà operaia.
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Carotid endarterectomy (CEA) risk stratification for adverse events at one year follow-up: the role of preoperative functional capacity scores, age, BNP and hemoglobin
No full textThe aim of the study was to evaluate combination of functional status tools (American Society of Anesthesiologists Physical Status Classification System (ASA PS)) status, Metabolic Equivalent of Task (METs), Revised Cardiac Risk Index for Pre-Operative Risk (RCRI) largely used in preoperative risk assessment with humoral variables in building powerful predictive models of Major Adverse Cardiac Cerebrovascular Events (MACCE) in a one-year follow-up after carotid endoarterectomy (CEA). All consecutive patients undergoing CEA during a 12-month period, were enrolled in this prospective observational study. Demographic data, functional capacity (FC) measured by risk stratification scores RCRI, ASA physical status, METs and preoperative levels of hemoglobin and Brain Natriuretic Peptide (Pro-BNP), coexisting comorbidities, have been collected. 201 consecutive patients undergoing CEA under local anesthesia (men 137 (68.16%), women 64 (31.84%)) with a median age of 75 years (Interquartile range (IQR) 67–80 years), Body mass index (BMI) median of 26.23 (IQR 24.4–28.89) were enrolled. Combination of all variables studied leave at a good one-year prognostic tool with AUC of 0.93 (Sensitivity (SEN) 46.6, Specificity (SPEC) 95.7). Preoperative hemoglobin correlate with Major Adverse Cardiac Cerebrovascular Events (MACCE) at 3 months (p = 0.018), while the preoperative BNP at 12 months shows correlation with adverse events (p = 0.004). Age has a significant correlation with adverse events at 12 months between demographic and anthropometric factors (p = 0.002). MACCE may adversely affect short- and long-term outcomes after CEA. Evaluation of preoperative functional capacity by RCRI, ASA physical status and METs combined with age and biomarkers such as pro-BNP and hemoglobin, may improve risk stratification in patients undergoing carotid surgery
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