1,721,348 research outputs found
Be stupid for successful living
No full textIl libro presenta lo sviluppo della storia imprenditoriale di Renzo Rosso, il fondatore del gruppo Diesel e gli insegnamenti che possono essere tratti da tale storia. In particolare il libro si concentra sulla innovazione imprenditoriale e sulla diversificazione geografica e settoriale
Diffusion wave modeling of distributed catchment dynamics
No full textA diffusion wave model of distributed catchment dynamics is presented. The effects of catchment topography and river network structure on storm-flow response are incorporated by routing surface runoff in cascade throughout a digital elevation model (DEM) based conceptual transport network, where the Muskingum-Cunge scheme with variable parameters is used to describe surface runoff dynamics. Dynamic scaling of hydraulic geometry is also incorporated in the model by using the 1953 “at-a-station” and “downstream” relationships by Leopold and Maddock. Numerical experiments indicate that the model is more than 98% mass conservative for possible slope and roughness configurations, which may occur for hillslopes in a natural catchment. Fluctuations in the simulated discharge may occur in response to discontinuities in rainfall excess representation if Courant number Cu during the simulation exceeds a threshold of about 3. Catchment scale simulations with different temporal resolution show that the model response is independent of structural parameters (model consistency). Also, the overall accuracy is preserved for computationally inexpensive space-time discretizations (for which Cu > 3) because fluctuations that may occur at the local scale are dampened when propagating downstream. Comparison of model results with observed outlet hydrographs of the Rio Missiaga experimental catchment (Eastern Italian Alps) show this approach to be capable of describing both overland and channel phases of surface runoff in mountainous catchments
Stabilizing Role of a Curvature Correction to Line Tension
No full textWe study the effects that a curvature correction to the line tension has on the equilibrium and stability of liquid droplets laid upon a rigid substrate. In the simple case of cylindric liquid bridges we prove that even a tiny curvature correction prevents the onset of wildly oscillating perturbations that would make the contact line unstable if a negative line tension were present alone. However, if the curvature correction is not large enough, unstable modes that are not related to the classical Rayleigh instability can persist
Closure to discussion to "Diffusion wave modelling of distributed catchment dynamics" by V. M. Ponce
No full textThere is no abstract in this kind of contribution
Sull’onda di piena diffusiva nei reticoli di drenaggio naturali
No full textUn modello distribuito dell'onda di piena diffusiva viene applicato alla rete idrografica del bacino della Sieve (840~km) per analizzare gli effetti della descrizione dinamica del deflusso superficiale sulla risposta idrologica di piena. L'onda di piena viene propagata in cascata sulla rete idraulica identificata a partire dal modello digitale delle quote del bacino secondo il metodo Muskingum-Cunge a parametri variabili. La geometria idraulica del reticolo è rappresentata mediante sezioni rettangolari con base che varia dinamicamente, in accordo con le relazioni di autosomiglianza di Leopold e Maddock. Gli idrogrammi simulati mostrano come la descrizione dinamica del reticolo idrografico causi il rallentamento e l'attenuazione dell'onda di piena rispetto al caso di reticolo a geometria costante nel tempo, consentendo una migliore riproduzione della risposta del bacino. Le velocità ottenute dall'analisi "lagrangiana" del fenomeno di piena risultano in accordo con gli studi sperimentali riportati in letteratura per quanto riguarda la loro variabilità spaziale e rivelano una sensibile dinamica del campo di moto nelle diverse fasi dell'evento di piena
Parameterization of stream channel geometry in the distributed modeling of catchment dynamics
No full textA simple and efficient procedure for incorporating the effects of streamchannel geometry in the distributed modeling of catchment dynamics is developed. At-astationand downstream fluvial relationships are combined and the obtained laws ofvariability in space and time for water-surface width and wetted perimeter areincorporated into a diffusion wave routing model based on the Muskingum-Cunge methodwith variable parameters. The parameterization obtained is applied to the approximately840-km2 Sieve catchment (Central Italian Apennines) to test the possibility of estimatingchannel geometry parameters from cross-section surveys and to assess the impact ofdynamic variations in the channel geometry on catchment dynamics. The use of theestimated channel geometry in surface runoff routing produces a significant improvementin the flood hydrograph description at the catchment outlet with respect to less detailednetwork parameterizations. In addition, the results obtained from a “downstream” analysisof the velocity field indicate that the stream characteristics related to the locally varyingcross-section shape may have a strong control on flow velocities, and thus they should bemonitored and synthesized for a comprehensive description of the distributed catchmentdynamics
Hip axis length in an Italian osteoporotic population
No full textModels proposed so far for the pathogenesis of osteoporosis often do not take into account the factors underlying the different incidences of hip fracture in different populations. To address this issue, we identified 34 female patients with hip fracture (HF) and 16 women with at least four vertebral fractures (VF) in a population-based retrospective study. Each participant had a bone mineral density (BMD) measurement of the lumbar spine and hip using a Hologic QDR-2000 scantier, in single beam mode for the latter site. Hip axis length (HAL) was determined automatically (precision 1.5%). HAL derived from 149 normal subjects (age range 19-75 years) was 10.3+/-0.5 cm. BMD values found at the femoral neck were almost similar, but differed significantly at the spine between the two groups. Mean values of femur HAL in HF patients (10.55+/-0.5 cm) were significantly higher compared with VF patients (9.85+/-0.54 cm; p<0.001). Interestingly, both mean values differed significantly from the mean for normal subjects. Our results demonstrate that patients with multiple vertebral fractures have significantly lower vertebral BMD values but similar femoral neck values compared with patients who fracture at the hip; furthermore, hip axis length was more than 1 SD higher in these latter patients compared with that of VF patients. These results suggest that the size and shape of the hip can explain part of the observed aetiologic differences between these two types of osteoporotic fractures
A Flash-Flood Event-Based Spatially-Distributed Rainfall-Runoff Transformation (FEST98) Model
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