Search results for "DEB"
showing 10 items of 1307 documents
Zvaigžņotā Debess: 2015, Vasara (228)
2015
Latvijas Universitāte
Optical calibration of a multispectral imaging system based on interference filters
2005
We present a new approach to optically calibrate a multispectral imaging system based on interference filters. Such a system typically suffers from some blurring of its channel images. Because the effectiveness of spectrum reconstruction depends heavily on the quality of the acquired channel images, and because this blurring negatively affects them, a method for deblurring and denoising them is required. The blur is modeled as a uniform intensity distribution within a circular disk. It allows us to characterize, quantitatively, the degradation for each channel image. In terms of global reduction of the blur, it consists of the choice of the best channel for the focus adjustment according to…
Quasi-Newton approach to nonnegative image restorations
2000
Abstract Image restoration, or deblurring, is the process of attempting to correct for degradation in a recorded image. Typically the blurring system is assumed to be linear and spatially invariant, and fast Fourier transform (FFT) based schemes result in efficient computational image restoration methods. However, real images have properties that cannot always be handled by linear methods. In particular, an image consists of positive light intensities, and thus a nonnegativity constraint should be enforced. This constraint and other ways of incorporating a priori information have been suggested in various applications, and can lead to substantial improvements in the reconstructions. Neverth…
Protoplanetary Disks, Solar System Minor Bodies and Origin of Life
2001
In the last decade, planetary science researchers have obtained significant advances on the origin and evolution of life on Earth. The increasing resolution and the development of new instruments (as space telescopes and adaptative optics) has provided first detailed images on protoplanetary disks and star formation regions. Moreover, in the last few years, doppler spectroscopic technique has confirmed the presence of extrasolar planets. These evidence shows planetary formation as a continuous and very common process in the Cosmos, indicating that our Solar System is not too special as was suggested in the past.
Regional debris flow susceptibility assessment using HRDEM: Example of the city area of Messina (Sicily, Italy)
2014
Shallow landslide and debris flows are among the most dangerous natural hazards triggered by extreme meteorological events. These phenomena have recently caused catastrophic scenarios in Italy (e.g. in Sarno-Quindici and Giampilieri) and, according to expected changes in the climate pattern, an increasing frequency of these phenomena is expected. The aim of this research is to assess the debris flow susceptibility in the Giampilieri area (Sicily) using a spatially-distributed debris flow runout model based on topographic information. The application of the model starts with the identification of the source areas from which debris flows are propagated on the basis of frictional laws and flow…
Estimation of velocity profile in a hyper-concentrated flow: a critical analysis of Bagnold equation
2018
Debris flow velocity is an important factor which influences the impact forces and runup. Due to the complexity of the phenomenon, it is difficult to define predictive methodologies. The present work reports some results of an experimental run conducted in order to investigate the velocity and sediment concentration distributions. A modified Bagnold’s approach to calculate the vertical distribution of flow velocity is presented.
Predicting storm triggered debris flow events: application to the 2009 Ionian-Peloritan disaster (Sicily, Italy)
2015
Debris flows are shallow landslides triggered by extreme meteorological events and propagating into the drainage lines of a slope as a fluid. A debris flow susceptibility map depicts the spatial probability for future phenomena to be triggered in a given area. Stochastic approaches are widely used in landslide studies for the assessment of the susceptibility. In fact, they allow to obtain a predictive function which relates a response variable (presence/absence of landslides) and a set of physical-environmental variables which are expected to control the slope failure phenomena. Future landslide occurrences are typically predicted by studying a past landslide inventory, under the basic assu…
Digital image-based technique for monitoring surface velocity: sensitivity analysis with processing parameters using data of a study case
2016
This paper describes the application of image-based technique for mapping surface velocity of hyper-concentrated flows. The analysis is conducted with the aid of data collected in a scale laboratory flume constructed at the Hydraulic laboratory of the Department of Civil, Environmental, Aerospatial and of Mate-rials Engineering (DICAM) – University of Palermo (Italy). A fully digital images-based technique has been applied to record a large amount of high resolution images identifying simultaneously the position of points in different time instants. The sensitivity analysis of the estimated flow velocity with the acquisition conditions and the number of processed frames is performed
Monitoring of surface velocity of hyper-concentrated flow in a laboratory flume by means of fully-digital PIV
2016
This paper investigates the utility and the efficiency of the digital image-technique for remote monitoring of surface velocity in hyper-concentrated flow by the aid of data collected during experiments conducted in the laboratory flume. In particular the present paper attention is focused on the estimation procedure of the velocity vectors and on their sensitivity with parameters (number of images, spatial resolution of interrogation area, ) of the images processing procedure.