Macro aerodynamic devices controlled by micro systems

Micro-ElectroMechanical-Systems (MEMS) have emerged as a major enabling technology across the engineering disciplines. In this study, the possibility of applying MEMS to the aerodynamic field was explored. We have demonstrated that microtransducers can be used to control the motion of a delta wing in a wind tunnel and can even maneuver a scaled aircraft in flight tests. The main advantage of using micro actuators to replace the traditional control surface is the significant reduction of radar cross-sections. At a high angle of attack, a large portion of the suction loading on a delta wing is contributed by the leading edge separation vortices which originate from thin boundary layers at the leading edge. We used microactuators with a thickness comparable to that of the boundary layer in order to alter the separation process and thus achieved control of the global motion by minute perturbations

A nonlinear Schr\"odinger equation for water waves on finite depth with constant vorticity

A nonlinear Schr\"odinger equation for the envelope of two dimensional surface water waves on finite depth with non zero constant vorticity is derived, and the influence of this constant vorticity on the well known stability properties of weakly nonlinear wave packets is studied. It is demonstrated that vorticity modifies significantly the modulational instability properties of weakly nonlinear plane waves, namely the growth rate and bandwidth. At third order we have shown the importance of the coupling between the mean flow induced by the modulation and the vorticity. Furthermore, it is shown that these plane wave solutions may be linearly stable to modulational instability for an opposite shear current independently of the dimensionless parameter kh, where k and h are the carrier wavenumber and depth respectively

What computational model provides the best explanation of face representations in the primate brain?

Understanding how the brain represents the identity of complex objects is a central challenge of visual neuroscience. The principles governing object processing have been extensively studied in the macaque face patch system, a sub-network of inferotemporal (IT) cortex specialized for face processing (Tsao et al., 2006). A previous study reported that single face patch neurons encode axes of a generative model called the “active appearance” model (Chang and Tsao, 2017), which transforms 50-d feature vectors separately representing facial shape and facial texture into facial images (Cootes et al., 2001; Edwards et al., 1998). However, it remains unclear whether this model constitutes the best model for explaining face cell responses. Here, we recorded responses of cells in the most anterior face patch AM to a large set of real face images, and compared a large number of models for explaining neural responses. We found that the active appearance model better explained responses than any other model except CORnet-Z, a feedforward deep neural network trained on general object classification to classify non-face images, whose performance it tied on some face image sets and exceeded on others. Surprisingly, deep neural networks trained specifically on facial identification did not explain neural responses well. A major reason is that units in the network, unlike neurons, are less modulated by face-related factors unrelated to facial identification such as illumination

A Micromachined Permalloy Magnetic Actuator Array for Micro Robotics Assembly Systems

Arrays of permalloy magnetic actuators have been studied for the use as precision micro robotics assembly systems. The actuator arrays have been tested for lifting and moving silicon and glass chips. The actuator unit consists of a permalloy plate 1 mm x 1 mm X 5µm in size together with polysilicon bending supports. Experimentally, it can lift a 87 µN (or 8.88 mg) force under a magnetic field of approximately 2 x 10^4 A/m. A proposed synchronous driving mode has been observed, and both translation and rotation of a silicon chip has been demonstrated

Cladding mode coupling in highly localized fiber Bragg gratings: modal properties and transmission spectra

The spectral characteristics of a fiber Bragg grating (FBG) with a transversely inhomogeneous refractive index profile, differs con- siderably from that of a transversely uniform one. Transmission spectra of inhomogeneous and asymmetric FBGs that have been inscribed with focused ultrashort pulses with the so-called point-by-point technique are investigated. The cladding mode resonances of such FBGs can span a full octave in the spectrum and are very pronounced (deeper than 20dB). Using a coupled-mode approach, we compute the strength of resonant coupling and find that coupling into cladding modes of higher azimuthal order is very sensitive to the position of the modification in the core. Exploiting these properties allows precise control of such reflections and may lead to many new sensing applications.Comment: Submission to OE, 16 pages, 6 figure

Expression of the neuroprotective slow Wallerian degeneration (WldS) gene in non-neuronal tissues

<p>Abstract</p> <p>Background</p> <p>The slow Wallerian Degeneration (<it>Wld</it>^<it>S</it>) gene specifically protects axonal and synaptic compartments of neurons from a wide variety of degeneration-inducing stimuli, including; traumatic injury, Parkinson's disease, demyelinating neuropathies, some forms of motor neuron disease and global cerebral ischemia. The <it>Wld</it>^{<it>S </it>}gene encodes a novel Ube4b-Nmnat1 chimeric protein (Wld^Sprotein) that is responsible for conferring the neuroprotective phenotype. How the chimeric Wld^Sprotein confers neuroprotection remains controversial, but several studies have shown that expression in neurons <it>in vivo </it>and <it>in vitro </it>modifies key cellular pathways, including; NAD biosynthesis, ubiquitination, the mitochondrial proteome, cell cycle status and cell stress. Whether similar changes are induced in non-neuronal tissue and organs at a basal level <it>in vivo </it>remains to be determined. This may be of particular importance for the development and application of neuroprotective therapeutic strategies based around <it>Wld</it>^<it>S</it>-mediated pathways designed for use in human patients.</p> <p>Results</p> <p>We have undertaken a detailed analysis of non-neuronal <it>Wld</it>^{<it>S </it>}expression in <it>Wld</it>^{<it>S </it>}mice, alongside gravimetric and histological analyses, to examine the influence of <it>Wld</it>^{<it>S </it>}expression in non-neuronal tissues. We show that expression of <it>Wld</it>^{<it>S </it>}RNA and protein are not restricted to neuronal tissue, but that the relative RNA and protein expression levels rarely correlate in these non-neuronal tissues. We show that <it>Wld</it>^{<it>S </it>}mice have normal body weight and growth characteristics as well as gravimetrically and histologically normal organs, regardless of Wld^Sprotein levels. Finally, we demonstrate that previously reported <it>Wld</it>^<it>S</it>-induced changes in cell cycle and cell stress status are neuronal-specific, not recapitulated in non-neuronal tissues at a basal level.</p> <p>Conclusions</p> <p>We conclude that expression of Wld^Sprotein has no adverse effects on non-neuronal tissue at a basal level <it>in vivo</it>, supporting the possibility of its safe use in future therapeutic strategies targeting axonal and/or synaptic compartments in patients with neurodegenerative disease. Future experiments determining whether Wld^Sprotein can modify responses to injury in non-neuronal tissue are now required.</p

Ice-Crystal Icing Accretion Studies at the NASA Propulsion Systems Laboratory

This paper describes an ice-crystal icing experiment conducted at the NASA Propulsion System Laboratory during June 2018. This test produced ice shape data on an airfoil for different test conditions similar to those inside the compressor region of a turbo-fan jet engine. Mixed-phase icing conditions were generated by partially freezing out a water spray using the relative humidity of flow as the primary parameter to control freeze-out. The paper presents the ice shape data and associated conditions which include pressure, velocity, temperature, humidity, total water content, melt ratio, and particle size distribution. The test featured a new instrument traversing system which allowed surveys of the flow and cloud. The purpose of this work was to provide experimental ice shape data and associated conditions to help develop and validate ice-crystal icing accretion models. The results support previous experimental observations of a minimum melt-ratio threshold for accretion to occur as well as the existence of a plateau region where the icing severity is high for a range of melt ratios. However, a maximum limit for melt ratio, which is suggested in the ice crystal icing literature, was not observed perhaps complicated by the potential for some supercooling of the water at these conditions