880 research outputs found
Neural Models of Normal and Abnormal Behavior: What Do Schizophrenia, Parkinsonism, Attention Deficit Disorder, and Depression Have in Common?
Defense Advanced Research Projects Agency and Office of Naval Research (N00014-95-1-0409); National Science Foundation (IRI-97-20333
Optimal Wideband LPDA Design for Efficient Multimedia Content Delivery over Emerging Mobile Computing Systems
An optimal synthesis of a wideband Log-Periodic
Dipole Array (LPDA) is introduced in the present study. The LPDA optimization is performed under several requirements concerning the standing wave ratio, the forward gain, the gain flatness, the front-to-back ratio and the side lobe level, over a
wide frequency range. The LPDA geometry that complies with the above requirements is suitable for efficient multimedia content delivery. The optimization process is accomplished by applying a recently introduced method called Invasive Weed Optimization (IWO). The method has already been compared to other evolutionary methods and has shown superiority in solving complex non-linear problems in telecommunications and electromagnetics. In the present study, the IWO method has been chosen to optimize an LPDA for operation in the frequency range
800-3300 MHz. Due to its excellent performance, the LPDA can effectively be used for multimedia content reception over future mobile computing systems
Neural Dynamics of Autistic Behaviors: Cognitive, Emotional, and Timing Substrates
What brain mechanisms underlie autism and how do they give rise to autistic behavioral symptoms? This article describes a neural model, called the iSTART model, which proposes how cognitive, emotional, timing, and motor processes may interact together to create and perpetuate autistic symptoms. These model processes were originally developed to explain data concerning how the brain controls normal behaviors. The iSTART model shows how autistic behavioral symptoms may arise from prescribed breakdowns in these brain processes.Air Force Office of Scientific Research (F49620-01-1-0397); Office of Naval Research (N00014-01-1-0624
Describing synchronization and topological excitations in arrays of magnetic spin torque oscillators through the Kuramoto model
The collective dynamics in populations of magnetic spin torque oscillators
(STO) is an intensely studied topic in modern magnetism. Here, we show that
arrays of STO coupled via dipolar fields can be modeled using a variant of the
Kuramoto model, a well-known mathematical model in non-linear dynamics. By
investigating the collective dynamics in arrays of STO we find that the
synchronization in such systems is a finite size effect and show that the
critical coupling-for a complete synchronized state-scales with the number of
oscillators. Using realistic values of the dipolar coupling strength between
STO we show that this imposes an upper limit for the maximum number of
oscillators that can be synchronized. Further, we show that the lack of long
range order is associated with the formation of topological defects in the
phase field similar to the two-dimensional XY model of ferromagnetism. Our
results shed new light on the synchronization of STO, where controlling the
mutual synchronization of several oscillators is considered crucial for
applications.Comment: Accepted for publication in Scientific Reports. Corrected typo in
Eq.(9) from previous versio
A novel mechanical analogy based battery model for SoC estimation using a multi-cell EKF
The future evolution of technological systems dedicated to improve energy
efficiency will strongly depend on effective and reliable Energy Storage
Systems, as key components for Smart Grids, microgrids and electric mobility.
Besides possible improvements in chemical materials and cells design, the
Battery Management System is the most important electronic device that improves
the reliability of a battery pack. In fact, a precise State of Charge (SoC)
estimation allows the energy flows controller to exploit better the full
capacity of each cell. In this paper, we propose an alternative definition for
the SoC, explaining the rationales by a mechanical analogy. We introduce a
novel cell model, conceived as a series of three electric dipoles, together
with a procedure for parameters estimation relying only on voltage measures and
a given current profile. The three dipoles represent the quasi-stationary, the
dynamics and the istantaneous components of voltage measures. An Extended
Kalman Filer (EKF) is adopted as a nonlinear state estimator. Moreover, we
propose a multi-cell EKF system based on a round-robin approach to allow the
same processing block to keep track of many cells at the same time. Performance
tests with a prototype battery pack composed by 18 A123 cells connected in
series show encouraging results.Comment: 8 page, 12 figures, 1 tabl
How Is a Moving Target Continuously Tracked Behind Occluding Cover?
Office of Naval Research (N00014-95-1-0657, N00014-95-1-0409
Automatic Activation of Phonological Templates for Native but Not Nonnative Phonemes: An Investigation of the Temporal Dynamics of Mu Activation
Models of speech perception suggest a dorsal stream connecting the temporal and inferior parietal lobe with the inferior frontal gyrus. This stream is thought to involve an auditory-motor loop that translates acoustic information into motor/articulatory commands and is further influenced by decision making processes that involve maintenance of working memory or attention. Parsing out dorsal stream’s speech specific mechanisms from memory related ones in speech perception poses a complex problem. Here I argue that these processes may be disentangled from the viewpoint of the temporal dynamics of sensorimotor neural activation around a speech perception related event.
Methods: Alpha (~10Hz) and beta (~20Hz) spectral components of the mu () rhythm, localized to sensorimotor regions, have been shown to index somatosensory and motor activity, respectively. In the present work, event related spectral perturbations (ERSP) of the EEG -rhythm were analyzed, while manipulating two factors: active/passive listening, and perception of native/nonnative phonemes. Active and passive speech perception tasks were used as indexes of memory load employed, while native and. nonnative perception were used as indexes of automatic top-down coding for sensory analysis.
Results: Statistically significant differences were found in the oscillatory patterns of components between active and passive speech perception conditions with greater alpha and beta event related desynchronization (ERD) after stimuli offset in active speech perception. When compared to listening to noise, passive speech perception presented significantly (pFDR
Conclusion: These findings suggest that neural processes within the dorsal auditory stream are functionally and automatically involved in speech perception mechanisms. While its early activity (shortly after stimuli onset) seems to be importantly involved with the instantiation of predictive motor/articulatory internal models that help constraining speech discrimination, its later activity (post-stimulus offset) seems essential in the maintenance of working memory processes
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