A data driven equivariant approach to constrained Gaussian mixture modeling

Maximum likelihood estimation of Gaussian mixture models with different class-specific covariance matrices is known to be problematic. This is due to the unboundedness of the likelihood, together with the presence of spurious maximizers. Existing methods to bypass this obstacle are based on the fact that unboundedness is avoided if the eigenvalues of the covariance matrices are bounded away from zero. This can be done imposing some constraints on the covariance matrices, i.e. by incorporating a priori information on the covariance structure of the mixture components. The present work introduces a constrained equivariant approach, where the class conditional covariance matrices are shrunk towards a pre-specified matrix Psi. Data-driven choices of the matrix Psi, when a priori information is not available, and the optimal amount of shrinkage are investigated. The effectiveness of the proposal is evaluated on the basis of a simulation study and an empirical example

Microprocessor fault-tolerance via on-the-fly partial reconfiguration

This paper presents a novel approach to exploit FPGA dynamic partial reconfiguration to improve the fault tolerance of complex microprocessor-based systems, with no need to statically reserve area to host redundant components. The proposed method not only improves the survivability of the system by allowing the online replacement of defective key parts of the processor, but also provides performance graceful degradation by executing in software the tasks that were executed in hardware before a fault and the subsequent reconfiguration happened. The advantage of the proposed approach is that thanks to a hardware hypervisor, the CPU is totally unaware of the reconfiguration happening in real-time, and there's no dependency on the CPU to perform it. As proof of concept a design using this idea has been developed, using the LEON3 open-source processor, synthesized on a Virtex 4 FPG

Sekcijas "Latvijas uzņēmumu konkurētspēja ārējos tirgos (EKOSOC VPP 5.2.1)" Ekonomikas un vadības fakultātē (19. februāris, 2016): Referātu tēzes

A fundamental and computationally challenging optimization task in wireless networks is to maximize the number of simultaneous transmissions, subject to signal-to-noise-and-interference ratio (SINR) requirements at the receivers. The conventional approach guaranteeing global optimality is to solve an integer programming model with explicit SINR constraints. These constraints are however numerically very difficult. We develop a new integer programming algorithm based on a much more effective representation of the SINR constraints. Computational experiments demonstrate that the new approach performs significantly better in proving optimality.©2011 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Antonio Capone, Lei Chen, Stefano Gualandi and Di Yuan, A New Computational Approach for Maximum Link Activation in Wireless Networks under the SINR Model, 2011, IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, (10), 5, 1368-1372. http://dx.doi.org/10.1109/TWC.2011.030311.10077

Synchronous dynamics in the presence of short-term plasticity

We investigate the occurrence of quasisynchronous events in a random network of excitatory leaky integrate-and-fire neurons equipped with short-term plasticity. The dynamics is analyzed by monitoring both the evolution of global synaptic variables and, on a microscopic ground, the interspike intervals of the individual neurons. We find that quasisynchronous events are the result of a mixture of synchronized and unsynchronized motion, analogously to the emergence of synchronization in the Kuramoto model. In the present context, disorder is due to the random structure of the network and thereby vanishes for a diverging network size $N$ (i.e., in the thermodynamic limit), when statistical fluctuations become negligible. Remarkably, the fraction of asynchronous neurons remains strictly larger than zero for arbitrarily large $N$. This is due to the presence of a robust homoclinic cycle in the self-generated synchronous dynamics. The nontrivial large-$N$ behavior is confirmed by the anomalous scaling of the maximum Lyapunov exponent, which is strictly positive in a finite network and decreases as {N}^{\ensuremath{-}0.27}. Finally, we have checked the robustness of this dynamical phase with respect to the addition of noise, applied to either the reset potential or the leaky current

An FPGA-Based Software Defined Radio Platform for the 2.4GHz ISM Band

A prototype of a Software Defined Radio (SDR) platform has been successfully designed and tested implementing a reconfigurable IEEE 802.11 and ZigBee receiver. The system exploits the reconfiguration capability of an FPGA for implementing a number of receiver configurations that share the same RF front-end. Configurations can be switched at run time, or can share the available logic and radio resource

Multiple sclerosis-like neurological manifestations in a coeliac patient: nothing is as it seems

Cobalamin (vitamin B(12)) deficiency occurs with several disorders, involving different organs and systems, including blood, bowel, nervous system and eyes. Although the most important features are usually haematological ones, presence of neurological involvement, in the absence of blood count alterations, has just been described in the literature. Here we report the case of a 48-year-old man, suffering from coeliac disease for approximately 5 years, vegetarian, who was admitted to our department, referring dysaesthesia of the left lower limb, decreased libido and erectile dysfunction. Vitamin B(12) deficiency was proved, even in the absence of blood count alteration, and treated with a vitamin supplement, resulting in complete remission

A new test of resistance in the diagnosis of postero-superior rotator cuff tears.

The aim of this study was to assess the diagnostic accuracy of a new clinical test for the diagnosis of subacromial impingement and full thickness postero-superior rotator cuff tears. One hundred and twenty patients who underwent arthroscopic treatment for acromioplasty or cuff repair were previously submitted to a new test of resistance. The test is performed in the standing position with the involved arm in 90 degrees abduction, 20 degrees -30 degrees anteposition and in external rotation (as for full-can test). Thus, the patient was invited to follow the way of a spiral drawn on a drawing sheet for 20 turns; 1 turn = from the centre to the end of the spiral and vice versa (spiral width = 20 cm). The test was considered positive when the patient was not able to conclude it due to strength decrease or to shoulder pain. Sensitivity, specificity, positive and negative predictive values as well as diagnostic accuracy were calculated for our test of resistance. The test resulted scarcely reliable as detector of subacromial impingement and not very reliable as detector of small tear. When the test is positive there is a high probability that a subacromial disease exists; instead, when it is negative there is a high probability that the patient has not a large or massive cuff tear. The resistance test (Gum-Turn test) adds to our armamentarium of physical examination signs in patients with painful shoulder and furnishes further information on possible dimensions of tendinous tear