Limits on Sparse Data Acquisition: RIC Analysis of Finite Gaussian Matrices

One of the key issues in the acquisition of sparse data by means of compressed sensing (CS) is the design of the measurement matrix. Gaussian matrices have been proven to be information-theoretically optimal in terms of minimizing the required number of measurements for sparse recovery. In this paper we provide a new approach for the analysis of the restricted isometry constant (RIC) of finite dimensional Gaussian measurement matrices. The proposed method relies on the exact distributions of the extreme eigenvalues for Wishart matrices. First, we derive the probability that the restricted isometry property is satisfied for a given sufficient recovery condition on the RIC, and propose a probabilistic framework to study both the symmetric and asymmetric RICs. Then, we analyze the recovery of compressible signals in noise through the statistical characterization of stability and robustness. The presented framework determines limits on various sparse recovery algorithms for finite size problems. In particular, it provides a tight lower bound on the maximum sparsity order of the acquired data allowing signal recovery with a given target probability. Also, we derive simple approximations for the RICs based on the Tracy-Widom distribution.Comment: 11 pages, 6 figures, accepted for publication in IEEE transactions on information theor

Cross-Layer Design of an Energy-Efficient Cluster Formation Algorithm with Carrier-Sensing Multiple Access for Wireless Sensor Networks

A new energy-efficient scheme for data transmission in a wireless sensor network (WSN) is proposed, having in mind a typical application including a sink, which periodically triggers the WSN, and nodes uniformly distributed over a specified area. Routing, multiple access control (MAC), physical, energy, and propagation aspects are jointly taken into account through simulation; however, the protocol design is based on some analytical considerations reported in the appendix. Information routing is based on a clustered self-organized structure; a carrier-sensing multiple access (CSMA) protocol is chosen at MAC layer. Two different scenarios are examined, characterized by different channel fading rates. Four versions of our protocol are presented, suitably oriented to the two different scenarios; two of them implement a cross-layer (CL) approach, where MAC parameters influence both the network and physical layers. Performance is measured in terms of network lifetime (related to energy efficiency) and packet loss rate (related to network availability). The paper discusses the rationale behind the selection of MAC protocols for WSNs and provides a complete model characterization spanning from the network layer to the propagation channel. The advantages of the CL approach, with respect to an algorithm which belongs to the well-known class of low-energy adaptive clustering hierarchy (LEACH) protocols, are shown

Syndrome-Based Encoding of Compressible Sources for M2M Communication

Data originating from many devices and sensors can be modeled as sparse signals. Hence, efficient compression techniques of such data are essential to reduce bandwidth and transmission power, especially for energy constrained devices within machine to machine communication scenarios. This paper provides accurate analysis of the operational distortion-rate function (ODR) for syndrome-based source encoders of noisy sparse sources. We derive the probability density function of error due to both quantization and pre- quantization noise for a type of mixed distributed source comprising Bernoulli and an arbitrary continuous distribution, e.g., Bernoulli- uniform sources. Then, we derive the ODR for two encoding schemes based on the syndromes of Reed-Solomon (RS) and Bose, Chaudhuri, and Hocquenghem (BCH) codes. The presented analysis allows designing a quantizer such that a target average distortion is achieved. As confirmed by numerical results, the closed-form expression for ODR perfectly coincides with the simulation. Also, the performance loss compared to an entropy based encoder is tolerable

The impact of sensing parameters on data management and anomaly detection in structural health monitoring

The massive and autonomous structural health monitoring (SHM) of bridges is a problem that is of growing interest due to its importance and topicality. However, a considerable amount of data must be elaborated and managed in such an application. This paper proposes a set of machine learning (ML) tools to detect anomalies in a bridge from vibrational measurements using the minimum amount of data. The proposed framework starts from the fundamental frequencies extracted through operational modal analysis (OMA) and clustering, followed by a density-based time-domain tracking algorithm. The funda- mental frequencies extracted are then fed to one-class classification (OCC) algorithms that perform anomaly detection. Then, to reduce the amount of data, we analyze the effect of the number of sensors, the number of bits per sample, the observation time, and the measurement noise on damage detection performance. As a case study, the Z-24 bridge is considered because of the extensive database of accelerometric measurements in both standard and damaged conditions. A comparison of OCC algorithms, such as principal component analysis (PCA), kernel principal component analysis (KPCA), Gaussian mixture model (GMM) and one-class classifier neural network (OCCNN)2 is performed, and their robustness to data shrinking is evaluated. In many cases, OCCNN2 increases the performance with respect to classical anomaly detection techniques in terms of accuracy

Il trattamento endovascolare degli aneurismi del circolo cerebrale

La rottura spontanea di un aneurisma di un'arteria del circolo cerebrale rappresenta sempre un evento drammatico in termini di mortalità e morbilità.Essa determina una emorragia nello spazio subaracnoideo (ESA).L'indagine angiografica effettuata per diagnosticare le cause dell'esa spesso individua la presenza di aneurisma del circolo cerebrale. Gli aneurismi sono estroflessioni sacciformi della parete arteriosa conseguenti a malformazione congenita dello strato muscolare.Il fondo dell'aneurisma costituito soltanto da intima ed avventizia può andare incontro a rottura con conseguente esa. La frequenza con cui attualmente individui vengono sottoposti ad indagini neuroradiologiche di imaging consente spesso di individuare la presenza di aneurisma cerebrale prima che la sua rottura abbia portato al quadro di esa. L'individuazione della presenza di aneurismi ,sia fissurati sia innocenti, pone un importante problema di trattamento terapeutico al fine di prevenire una nuova e più devastante rottura dell'aneurisma e, come nel caso di aneurismi innocenti, di impedirne la loro rottura. Due sono ad oggi le tecniche utilizzate allo scopo di escludere l'aneurisma rotto: il clipping della sacca mediante approccio chirurgico e il coiling endovascolare; scopo di questo lavoro è affrontare la tecnica endovascolare e confrontarla con la tradizionale ed efficace tecnica microneurochirurgica, affrontandone i vantaggi e gli svantaggi

Fattening system influences fatty acids composition in organic Maremmana bullocks

Organic UE Regulation No 889/2008 states that, in the choice of breeds or strains, account shall be taken of the capacity of animals to adapt to local conditions, their vitality and their resistance to disease. Preference is to be given to indigenous breeds and strains. Maremmana is a very rustic and long-lived Italian cattle breed, which seems to be the direct descendant of Italian aurochs (Bos primigenius) (Giorgetti et al., 2009). Selection has always been directed towards disease resistance and adaptation to the harsh environment, where Maremmana cattle live, and generally these cattle never are treated against parasites (Martini, 2001). Maremmana cattle can graze all the year, utilizing, in the summer and winter periods, the Mediterranean scrub as source of food and refuge. Rearing system, quality of the pasture and possible concentrate integrations can influence the quality of meat and its fatty acid composition. The aim of this research is to compare the fatty acid muscle composition of Maremmana bullocks reared in different fattening systems