Effects of nonlocal feedback on traveling fronts in neural fields subject to transmission delay

The work introduces a model for reciprocal connections in neural fields by a nonlocal feedback mechanism, while the neural field exhibits nonlocal interactions and intra-areal transmission delays. We study the speed of traveling fronts with respect to the transmission delay, the spatial feedback range and the feedback delay for general axonal and feedback connectivity kernels. In addition, we find a novel shape of traveling fronts due to the applied feedback and criteria for its occurence are derived

External stimulation induces switches between neural oscillations: an illustrative feedback model

International audienc

Detecting event-related recurrences by symbolic analysis: Applications to human language processing

Quasistationarity is ubiquitous in complex dynamical systems. In brain dynamics there is ample evidence that event-related potentials reflect such quasistationary states. In order to detect them from time series, several segmentation techniques have been proposed. In this study we elaborate a recent approach for detecting quasistationary states as recurrence domains by means of recurrence analysis and subsequent symbolisation methods. As a result, recurrence domains are obtained as partition cells that can be further aligned and unified for different realisations. We address two pertinent problems of contemporary recurrence analysis and present possible solutions for them.Comment: 24 pages, 6 figures. Draft version to appear in Proc Royal Soc

Detection of fixed points in spatiotemporal signals by clustering method

We present a method to determine fixed points in spatiotemporal signals. A 144-dimensioanl simulated signal, similar to a Kueppers-Lortz instability, is analyzed and its fixed points are reconstructed.Comment: 3 pages, 3 figure

Generation of acoustic emission from the running-in and subsequent micropitting of a mixed-elastohydrodynamic contact

This paper presents the use of Acoustic Emission to study the running-in and subsequent micropitting of a pair of hardened steel surfaces under mixed lubrication conditions. These surfaces were loaded together under rolling/sliding conditions typical of heavily loaded gearing. Relocation profilometry was used to measure the rapid running-in process and the development of micropits. Acoustic emission (AE) was found to be highly sensitive to both the initial changes in surface topography during the running-in process, and to subsequent changes caused by micropit formation. However, AE appears to be sensitive to changes in asperity interaction rather than the underlying mechanisms of plastic deformation, crack growth and fracture. It is concluded that AE can provide considerable insight into conditions in mixed-elastohydrodynamic contacts

Finding in Commercial-Engineer Controversy

Finding concerning a controversy between the commercial and engineer departments at Utah Agricultural College

Stimulus statistics shape oscillations in nonlinear recurrent neural networks.

Rhythmic activity plays a central role in neural computations and brain functions ranging from homeostasis to attention, as well as in neurological and neuropsychiatric disorders. Despite this pervasiveness, little is known about the mechanisms whereby the frequency and power of oscillatory activity are modulated, and how they reflect the inputs received by neurons. Numerous studies have reported input-dependent fluctuations in peak frequency and power (as well as couplings across these features). However, it remains unresolved what mediates these spectral shifts among neural populations. Extending previous findings regarding stochastic nonlinear systems and experimental observations, we provide analytical insights regarding oscillatory responses of neural populations to stimulation from either endogenous or exogenous origins. Using a deceptively simple yet sparse and randomly connected network of neurons, we show how spiking inputs can reliably modulate the peak frequency and power expressed by synchronous neural populations without any changes in circuitry. Our results reveal that a generic, non-nonlinear and input-induced mechanism can robustly mediate these spectral fluctuations, and thus provide a framework in which inputs to the neurons bidirectionally regulate both the frequency and power expressed by synchronous populations. Theoretical and computational analysis of the ensuing spectral fluctuations was found to reflect the underlying dynamics of the input stimuli driving the neurons. Our results provide insights regarding a generic mechanism supporting spectral transitions observed across cortical networks and spanning multiple frequency bands

Modeling of the Power Cycling Performance of a Si on Si Flip Chip Assembly

Flip Chip (FC) technology offers many advantages over conventional surface mount technology, including a smaller device footprint and higher interconnection density. Low power but complex consumer items, such as mobile telecommunications devices, utilise this packaging technology and it is likely to spread to other electronics sectors where components have higher power dissipations and/or they have to operate in a hostile environment. As the scope for FC packaging broadens, a reliable means of establishing the long term performance of a particular package is necessary. Traditionally thermal cycling has been a primary reliability test for electronic assemblies including FC, however this fails to capture the behaviour of assemblies where the component thermal expansion is well matched to that of the substrate due to the isothermal heating and cooling of the assembly. In this situation power cycling offers an alternative means of determining the module performance. This paper describes the use of Finite Element Modeling (FEM) to explore the effects of power cycling on a silicon on silicon Multi-Chip Module (MCM) constructed with a low solder joint standoff height of 30-35µm. Particular attention was given to the boundary conditions that are inevitably atypical of those used in traditional thermal cycling. The paper presents results of the temperature distributions throughout the assembly, which were found to depend upon the substrate base material (FR4 or copper) that the MCM was attached to. The results of the FEM analysis were verified by assembling test devices and measuring their temperature distribution under steady state and power cycling conditions. The predicted temperatures may then be used as boundary conditions in FEM of thermal stresses and fatigue in the assembly

AXISYMMETRIC, THROTTLEABLE NON-GIMBALLED ROCKET ENGINE

A rocket engine assembly is provided for a vertically launched rocket vehicle. A rocket engine housing of the assembly includes two or more combustion chambers each including an outlet end defining a sonic throat area. A propellant supply for the combustion chambers includes a throttling injector, associated with each of the combustion chambers and located opposite to sonic throat area, which injects the propellant into the associated combustion chamber. A modulator, which may form part of the injector, and which is controlled by a controller, modulates the flow rate of the propellant to the combustion chambers so that the chambers provide a vectorable net thrust. An expansion nozzle or body located downstream of the throat area provides expansion of the combustion gases produced by the combustion chambers so as to increase the net thrust