Cooperative Spectrum Sensing based on the Limiting Eigenvalue Ratio Distribution in Wishart Matrices

Recent advances in random matrix theory have spurred the adoption of eigenvalue-based detection techniques for cooperative spectrum sensing in cognitive radio. Most of such techniques use the ratio between the largest and the smallest eigenvalues of the received signal covariance matrix to infer the presence or absence of the primary signal. The results derived so far in this field are based on asymptotical assumptions, due to the difficulties in characterizing the exact distribution of the eigenvalues ratio. By exploiting a recent result on the limiting distribution of the smallest eigenvalue in complex Wishart matrices, in this paper we derive an expression for the limiting eigenvalue ratio distribution, which turns out to be much more accurate than the previous approximations also in the non-asymptotical region. This result is then straightforwardly applied to calculate the decision threshold as a function of a target probability of false alarm. Numerical simulations show that the proposed detection rule provides a substantial performance improvement compared to the other eigenvalue-based algorithms.Comment: 7 pages, 2 figures, submitted to IEEE Communications Letter

Topological properties of semigroup primes of a commutative ring

A semigroup prime of a commutative ring $R$ is a prime ideal of the semigroup $(R,\cdot)$. One of the purposes of this paper is to study, from a topological point of view, the space \scal(R) of prime semigroups of $R$. We show that, under a natural topology introduced by B. Olberding in 2010, \scal(R) is a spectral space (after Hochster), spectral extension of \Spec(R), and that the assignment R\mapsto\scal(R) induces a contravariant functor. We then relate -- in the case $R$ is an integral domain -- the topology on \scal(R) with the Zariski topology on the set of overrings of $R$. Furthermore, we investigate the relationship between \scal(R) and the space $\boldsymbol{\mathcal{X}}(R)$ consisting of all nonempty inverse-closed subspaces of \spec(R), which has been introduced and studied in C.A. Finocchiaro, M. Fontana and D. Spirito, "The space of inverse-closed subsets of a spectral space is spectral" (submitted). In this context, we show that \scal( R) is a spectral retract of $\boldsymbol{\mathcal{X}}(R)$ and we characterize when \scal( R) is canonically homeomorphic to $\boldsymbol{\mathcal{X}}(R)$, both in general and when \spec(R) is a Noetherian space. In particular, we obtain that, when $R$ is a B\'ezout domain, \scal( R) is canonically homeomorphic both to $\boldsymbol{\mathcal{X}}(R)$ and to the space \overr(R) of the overrings of $R$ (endowed with the Zariski topology). Finally, we compare the space $\boldsymbol{\mathcal{X}}(R)$ with the space \scal(R(T)) of semigroup primes of the Nagata ring $R(T)$, providing a canonical spectral embedding \xcal(R)\hookrightarrow\scal(R(T)) which makes \xcal(R) a spectral retract of \scal(R(T)).Comment: 21 page

A topological version of Hilbert's Nullstellensatz

We prove that the space of radical ideals of a ring $R$, endowed with the hull-kernel topology, is a spectral space, and that it is canonically homeomorphic to the space of the nonempty Zariski closed subspaces of Spec$(R)$, endowed with a Zariski-like topology.Comment: J. Algebra (to appear

Real-Time Forecasting of Air Pollution Episodes in the Venetian Region. Part I: The Advection-Diffusion Model. Part II: The Kalman Predictor

The object of this overall research, which has an expected duration of two years is to set up a scheme for predicting ground-level pollutant concentrations for real-time control purposes (i.e. the action to be taken at the emission sources in the presence of forthcoming high pollutant events). The forecasting scheme is described, together with its application to sulphur dioxide pollution in the Venetian lagoon area. The scheme is based on a complex mathematical model to be run on a computer and receiving at the beginning of each interval of time all the information (about the meteorological and emission situation) required for the prediction. The type of control action which should be taken on the basis of such a forecast is the object of this part of the research

TherMos3, a tool for 3D electrothermal simulation of Smart Power Mosfets

In this paper we report on a novel simulation tool designed for the 3D coupled electro-thermal simulation of Smart Power Mosfets, that is a tool capable of taking into account not only the electrical (and thermal) behaviour of the power device but also the different driving strategies as they are imposed by a control logic circuit which usually resides on the same chip. The simulator is fully developed under Matlab and solves, self consistently, the 3D heat equation with proper boundary conditions and heat sources. An adaptive meshing algorithm based on temperature gradients and an optimized time stepping strategy have also been developed to reduce computational load and speed up simulation time without loosing accuracy. To validate this approach, simulator results are finally compared to experimental data obtained on a commercial Smart Power device used in automotive applications.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

A Process Evaluation of Post-Secondary Programs for High Functioning Students on the Autism Spectrum

ABSTRACT The purpose of this study was to evaluate how the post-secondary programs in the Mid-Atlantic region of the United States are supporting the needs of students with autism spectrum disorder (ASD) and preparing them for future independence. According to the CDC (Centers for Disease Control and Prevention), the number of children diagnosed with autism spectrum disorder is on the rise. In 2000, one in 150 children were identified with autism spectrum disorder. That number rose to one in every 44 children in the United States that have been identified with autism spectrum disorder in 2010. As these students reach the age of 21, they are no longer entitled to a free appropriate public education under IDEA but must self-advocate and hope to be found eligible for services. Statistics also show that autistic students with higher levels of education have better long-term income and are provided a greater opportunity for financial independence. Unfortunately, out of approximately 660 colleges or universities in the Mid-Atlantic region of the United States, only 26 programs exist for high-functioning students on the autism spectrum. Also, due to the fact that these programs are in the early stages of implementation, they do not provide significant data to determine the effectiveness and efficacy of the programs. Therefore, as the numbers of children with ASD continue to grow, colleges and universities will need to ensure that quality post-secondary opportunities are available for these students and will provide a level of readiness to allow these students with autism to self-advocate, achieve financial stability, and interact socially in their communities

Closure of a gastrocutaneous fistula by a tulip-bundle technique

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Open fracture-dislocation of the knee associated with nonunion of the medial femoral condyle and chronic tendon pa-tellar rupture

Background and aim of work: The incidence of coronal fractures of the femoral condyle, Hoffa frac-tures, ranges from 8.7% to 13% of all fractures of the distal femur and are often observed in polytraumas. Hoffa fractures may be misdiagnosed and consequently not properly treated. Reduction and synthesis of this type of fracture should be achieved to avoid complications such as nonunion, pain, functional impairment. The authors present a case of a 5 year old nonunion of a Hoffa fracture of the medial condyle with chronic patellar tendon rupture. Methods: Revision surgery consisted of reduction and fixation of the Hoffa fracture with screws associated with bone grafting from the iliac crest. Distalization of the patella by Z-plasty and reconstruction of the patellar tendon with Achille’s allograft were also performed. Results: Clinical evaluation after 10 months following the end of the treatment showed a complete resolution of pain, almost complete range of motion, good strength and almost complete functionality of the operated limb. Conclusions: Mistakes in the diagnosis or treatment of Hoffa fracture can often result nonunion, functional impairment, and per-sistent pain. To avoid these, the senior authors of this text believe that the correct treatment of acute Hoffa fracture and its potential associated injuries are crucial, according to the concept of early damage control and later synthesis with soft tissue reconstruction. (www.actabiomedica.it)

Dimensions of treatment quality most valued by adolescent substance users and their caregivers.

Professional psychologists are increasingly encouraged to document and evaluate the quality of the treatment they provide. However, there is a significant gap in knowledge about the extent to which extant definitions of treatment quality converge with patient perceptions. The primary goal of this study was to examine how adolescent substance users (ASU) and their caregivers perceive treatment quality. The secondary goal was to determine how these perceptions align with expert-derived definitions of ASU treatment quality and dimensions of perceived quality used frequently in other service disciplines. Focus groups and individual interviews were conducted with 24 ASU and 29 caregivers to explore how participants conceptualize a quality treatment experience. Content analysis identified three major dimensions of perceived treatment quality, each of which contained three sub-dimensions: Therapeutic Relationship (i.e., Acceptance, Caring, Connection), Provider Characteristics (i.e., Experience, Communication Skills, Accessibility), and Treatment Approach (i.e., Integrated Care, Use of Structure, and Parent Involvement). Results revealed modest convergence between patient perceptions and existing definitions of quality, with several meaningful discrepancies. Most notably, the Therapeutic Relationship was the most important dimension to ASU and their caregivers, while expert-derived definitions emphasized the Treatment Approach. Implications for practicing psychologists to enhance training and supervision, quality improvement, and health education initiatives are discussed