674 research outputs found
Applicability of Kinematic and Diffusive models for mud-flows: a steady state analysis
The paper investigates the applicability of Kinematic and Diffusive Wave models for mud-flows with a
power-law shear-thinning rheology. In analogy with a well-known approach for turbulent clear-water
flows, the study compares the steady flow depth profiles predicted by approximated models with those
of the Full Dynamic Wave one. For all the models and assuming an infinitely wide channel, the analytical
solution of the flow depth profiles, in terms of hypergeometric functions, is derived. The accuracy of the
approximated models is assessed by computing the average, along the channel length, of the errors, for
several values of the Froude and kinematic wave numbers. Assuming the threshold value of the error
equal to 5%, the applicability conditions of the two approximations have been individuated for several
values of the power-law exponent, showing a crucial role of the rheology. The comparison with the
clear-water results indicates that applicability criteria for clear-water flows do not apply to shearthinning
fluids, potentially leading to an incorrect use of approximated models if the rheology is not
properly accounted for
Impact dynamics of mud flows against rigid walls
Mud flows represent one of the major causes of natural hazards in mountain regions. Similarly to
debris flows, they consist of a hyper-concentrated mixture of water and sediments flowing down a
slope and may cause serious damages to people and structures. The present paper investigates the
force produced by a dam-break wave of mud impacting against a rigid wall. A power-law shearthinning
model is used to describe the rheology of the hyper-concentrated mixture. A onedimensional
shallow water model is adopted and a second-order Finite Volume scheme is employed
to numerically solve the governing equations. The results indicate that depending on the fluid
rheological parameters and on the bottom slope, there exists a minimum value of the wall distance
above which the peak force does not exceed the asymptotic value of the hydrostatic final condition.
For two different values of the channel slope, the dimensionless value of this lower bound is
individuated for several values of the power-law exponent and of a dimensionless Basal Drag
coefficient. An estimation of the maximum peak force for wall distance smaller than the minimum
value is also provided
Mechanical Systems: Symmetry and Reduction
Reduction theory is concerned with mechanical systems with symmetries. It constructs a
lower dimensional reduced space in which associated conservation laws are taken out and
symmetries are \factored out" and studies the relation between the dynamics of the given
system with the dynamics on the reduced space. This subject is important in many areas,
such as stability of relative equilibria, geometric phases and integrable systems
Real-time risk analysis for hybrid earthquake early warning systems
Earthquake Early Warning Systems (EEWS), based on real-time prediction of ground motion or structural response measures, may play a role in reducing vulnerability and/or exposition of buildings and lifelines. In fact, recently seismologists developed efficient methods for rapid estimation of event features by means of limited information of the P-waves. Then, when an event is occurring, probabilistic distributions of magnitude and source-to-site distance are available and the prediction of the ground motion at the site, conditioned to the seismic network measures, may be performed in analogy with the Probabilistic Seismic Hazard Analysis (PSHA). Consequently the structural performance may be obtained by the Probabilistic Seismic Demand Analysis (PSDA), and used for real-time risk management purposes. However, such prediction is performed in very uncertain conditions which have to be taken into proper account to limit false and missed alarms. In the present study, real-time risk analysis for early warning purposes is discussed. The magnitude estimation is performed via the Bayesian approach, while the earthquake localization is based on the Voronoi cells. To test the procedure it was applied, by simulation, to the EEWS under development in the Campanian region (southern Italy). The results lead to the conclusion that the PSHA, conditioned to the EEWS, correctly predicts the hazard at the site and that the false/missed alarm probabilities may be controlled by set up of an appropriate decisional rule and alarm threshold
REAL-TIME HAZARD ANALYSIS FOR EARTHQUAKE EARLY WARNING
Earthquake Early Warning Systems (EEWS), based on real-time prediction of ground motion or structural response measures, may play a role in reducing vulnerability and/or exposition of buildings and lifelines. In fact, recently seismologists developed efficient methods for rapid estimation of event features by means of limited information of the P-waves. Then, when an event is occurring, probabilistic distributions of magnitude and source-to-site distance are available and the prediction of the ground motion at the site, conditioned to the seismic network measures, may be performed in analogy with the Probabilistic Seismic Hazard Analysis (PSHA). Consequently
the structural performance may be obtained by the Probabilistic Seismic Demand Analysis
(PSDA), and used for real-time risk management purposes. However, such prediction is performed in very uncertain conditions which have to be taken into proper account to limit false and missed alarms. In the present study, real-time risk analysis for early warning purposes is discussed. The
magnitude estimation is performed via the Bayesian approach, while the earthquake localization is based on the Voronoi cells. To test the procedure it was applied, by simulation, to the EEWS under development in the Campanian region (southern Italy). The results lead to the conclusion that the PSHA, conditioned to the EEWS, correctly predicts the hazard at the site and that the
false/missed alarm probabilities may be controlled by set up of an appropriate decisional rule and alarm threshold
Real-time risk analysis for hybrid earthquake early warning systems
Earthquake Early Warning Systems (EEWS), based on real-time prediction of ground motion or
structural response measures, may play a role in reducing vulnerability and/or exposition of
buildings and lifelines. In fact, recently seismologists developed efficient methods for rapid
estimation of event features by means of limited information of the P-waves. Then, when an event is
occurring, probabilistic distributions of magnitude and source-to-site distance are available and the
prediction of the ground motion at the site, conditioned to the seismic network measures, may be
performed in analogy with the Probabilistic Seismic Hazard Analysis (PSHA). Consequently the
structural performance may be obtained by the Probabilistic Seismic Demand Analysis (PSDA), and
used for real-time risk management purposes. However, such prediction is performed in very
uncertain conditions which have to be taken into proper account to limit false and missed alarms. In
the present study, real-time risk analysis for early warning purposes is discussed. The magnitude
estimation is performed via the Bayesian approach, while the earthquake localization is based on the
Voronoi cells. To test the procedure it was applied, by simulation, to the EEWS under development
in the Campanian region (southern Italy). The results lead to the conclusion that the PSHA,
conditioned to the EEWS, correctly predicts the hazard at the site and that the false/missed alarm
probabilities may be controlled by set up of an appropriate decisional rule and alarm threshold
Aerosol Jet Printing of a Benzocyclobutene-Based Ink as Adhesive Material for Wafer Bonding Application
Aerosol jet printing (AJP) is an emerging additive manufacturing technology that is gaining increasing attention in the electronic field. Several studies have been carried out on the AJP of conductive, semiconductive, and dielectric polymers for electronic applications. However, wafer bonding is an application that is still uncovered by literature. Therefore, in this work, the AJP of benzocyclobutene (BCB) as a polymeric adhesive for wafer bonding is presented for the first time. A thorough characterization of the processing parameters is carried out to identify the most ideal conditions for printing at a relatively high speed. Then, square patterns are printed, proving the versatility of the AJP technology in terms of the reachable thickness of the deposited BCB patterns. Complex patterns with a resolution of approximate to 60 mu m are also printed. The bonding properties of the BCB are characterized from a morphological and mechanical point of view. In particular, the shear strength of the BCB coatings deposited with AJP is approximate to 39 MPa and it is comparable with the shear strength of BCB coating deposited by spin-coating. Consequently, AJP represents a valid alternative for the deposition of polymeric adhesive for wafer bonding
Melatonin in wake-sleep disorders in children, adolescents and young adults with mental retardation with or without epilepsy: a double-blind, cross-over, placebo-controlled trial
The aim of the present study was to verify the clinical efficacy of melatonin (MLT) in children, adolescents and young adults with wake–
sleep disorder and mental retardation, most of them on chronic anticonvulsant therapy for epileptic seizures, by means of a randomized,
double-blind, placebo-controlled cross-over trial. Twenty-five patients (16 males, nine females), aged from 3.6 to 26 years (mean 10.5 years),
all affected with mental retardation mostly with epileptic seizures, were randomized to oral synthetic fast-release MLT or placebo. Melatonin
was initiated at the daily dose of 3 mg, at nocturnal bedtime. In case of inefficacy, MLT dose could be titrated up to 9 mg the following
2 weeks at increments of 3 mg/week, unless the patient was unable to tolerate it. The analysis of all the sleep logs disclosed a significant
treatment effect of melatonin on sleep latency (P ¼ 0:019). Melatonin was well tolerated in all patients and no side effects were reported. In
conclusion, our study supports the efficacy of MLT in young patients with mental disabilities and epileptic seizures in improving the wake–
sleep disorders such as time to fall asleep. Overall, MLT appeared to influence the seizure frequency poorly, though there may be occasional
seizure worsening or improving. Such a dual effect requires further studies in young epileptic patients
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