A simple geometrical model for analysing the spectral response of a citrus canopy using satellite images †

Abstract

A simple geometrical model has been proposed for a citrus canopy. We assume the citrus orchard to be a lattice structure, with the trees positioned at its points and where the composite-scene reflectance is the sum of the reflectance of its individual components as weighted by their respective surfaces within a unit area. The model has been used to analyse the citrus spectral response obtained from Landsat-5 TM images for winter and summer, where the status of the orchard is different. The correlations between spectral and geometrical data show the influence of per cent crop cover, shadows and background in the composite scene reflectance. We conclude that the summer images could be more useful than the winter ones for parcel classification according to per cent crop cover.     

To the understanding of the formation of the III–V based droplet epitxial nanorings

The paper deals with the kinetics of the droplet epitaxial GaAs quantum ring formation grown on AlGaAs (0 0 1) surface. The observation is, that the aspect ratio of these nano structures is depends not only on the technological parameters but on the size of the initial droplet. Under appropriate growth conditions, the depressions, in the middle of the rings are deeper than the surface level of the substrate. A large number of tests show, that the depressions in the middle of the small rings are often deeper than that of the larger ones. The number is larger, than just statistical fluctuation. An explanation for this phenomenon and its kinetics are given in the paper, based on the size dependence of the material properties, like for instance solubility. The plausible explanation assumes is that the probability of the crystal seed formation in the larger droplets is higher.     

Evidence of Oxygen Ferromagnetism in ZnO Based Materials

Discoveries of room‐temperature ferromagnetism (RTFM) in semiconductors hold great promise in future spintronics technologies. Unfortunately, this ferromagnetism remains poorly understood and the debate concerning the nature, carrier‐mediated versus defect‐mediated, of this ferromagnetism in semiconducting oxides is still open. Here, by using X‐ray absorption (XAS) and X‐ray magnetic circular dichroism (XMCD), it is demonstrated that the oxygen ions have a ferromagnetic response in different ZnO‐based compounds showing RTFM behavior: ZnO nanoparticles capped with organic molecules and ZnO/ZnS heterostructures. These results demonstrate the intrinsic occurrence of RTFM in these systems, and point out that it is not related to the metallic cation but it relays on the conduction band of the semiconductor.     

Chaotic synchronization using monolithic Chua oscillators†

This paper presents experimental evidence of the synchronization between two monolithic chaotic oscillators. These oscillators have been fabricated using g_m — C design techniques in a 2-4 μm double-poly n-well CMOS technology. The circuit realizes an oscillator from Chua's circuit family and features electrical control of the parameters in the piecewise-linear function and on-chip tuning of the oscillator natural frequencies. The area of the circuit including pads is 5 mm² and the power dissipation is less than l-8mW for a symmetrical biasing of ±2.5V.     

Parallel Algorithms Based on the Temporal-Window Method for Non-Alternating 3D-WT over Angiographies Using a Multicomputer

In this paper, we introduce and evaluate the parallel implementations of two video sequences decorrelation algorithms having been developed based on the non-alternating three-dimensional wavelet transform (3D-WT) and the temporal-window method. The proposed algorithms have been proven to outperform the classic 3D-WT algorithm in terms of a better coding efficiency and lower computational requirements while enabling a lossless coding and a top-quality reconstruction: the two most highly relevant features to medical imaging applications. The parallel implementations of the algorithms are developed and tested on a shared memory system, a SGI Origin 3800 supercomputer, making use of a message-passing paradigm. We evaluate and analyze the performance of the implementations in terms of the response time and speed-up factor by varying the number of processors and various video coding parameters. The key point enabling the development of highly efficient implementations rely on a workload distribution strategy supplemented by the use of parallel I/O primitives, for better exploiting the inherent features of the application and computing platform. Two sets of I/O primitives are tested and evaluated: the ones provided by the C compiler and the ones belonging to the MPI/IO library.     

New Approach to Inter‐domain Multicast Protocols

IPTV broadcast channels and video content distribution are increasingly saturating network paths. New solutions based on inter‐domain multicast protocols could contribute to the enhancement of multimedia content distribution over the Internet. The aim of this paper is to propose new capabilities for an existing inter‐domain multicast protocol, the Protocol Independent Multicast‐Sparse Mode. We describe the modified protocol and analyze its behavior using newly developed tools based on an open‐source software simulator. The resulting protocol does not require topology information, which is advantageous for easier deployment. In addition, the adopted solution avoids inherent problems with inter‐domain multicast routing, such as multiple paths and path asymmetries.     

An anisotropic microsphere-based approach for fiber orientation adaptation in soft tissue

Evolutionary processes in biological tissue, such as adaptation or remodeling, represent an enterprising area of research. In this paper, we present a multiscale model for the remodeling of fibered structures, such as bundles of collagen fibrils. With this aim, we introduce a von Mises statistical distribution function to account for the directional dispersion of the fibrils, and we remodel the underlying fibrils by changing their orientation. To numerically compute this process, we make use of the microsphere approach, which provides a useful multiscale tool for homogenizing the microstructure behavior, related to the fibrils of the bundle, in the macroscale of the problem. The results show how the fibrils respond to the stimulus by reorientation of their structure. This process leads to a stiffer material eventually reaching a stationary state. These results are in agreement with those reported in the literature, and they characterize the adaptation of biological tissue to external stimuli.