2,110 research outputs found
Linear motor motion control using a learning feedforward controller
The design and realization of an online learning motion controller for a linear motor is presented, and its usefulness is evaluated. The controller consists of two components: (1) a model-based feedback component, and (2) a learning feedforward component. The feedback component is designed on the basis of a simple second-order linear model, which is known to have structural errors. In the design, an emphasis is placed on robustness. The learning feedforward component is a neural-network-based controller, comprised of a one-hidden-layer structure with second-order B-spline basis functions. Simulations and experimental evaluations show that, with little effort, a high-performance motion system can be obtained with this approach
BITE Cookbook and Business Cards
This project aims to create a visually appealing and functional cookbook along with an accompanying business card design. The cookbook will serve as a comprehensive guide for culinary enthusiasts, featuring a diverse range of recipes from various cuisines, while the business card design will effectively represent the chef or the business behind the cookbook
Ultrasensitive 3He magnetometer for measurements of high magnetic fields
We describe a 3He magnetometer capable to measure high magnetic fields (B >
0.1 Tesla) with a relative accuracy of better than 10^-12. Our approach is
based on the measurement of the free induction decay of gaseous, nuclear spin
polarized 3He following a resonant radio frequency pulse excitation. The
measurement sensitivity can be attributed to the long coherent spin precession
time T2* being of order minutes which is achieved for spherical sample cells in
the regime of motional narrowing where the disturbing influence of field
inhomogeneities is strongly suppressed. The 3He gas is spin polarized in-situ
using a new, non-standard variant of the metastability exchange optical
pumping. We show that miniaturization helps to increase T2* further and that
the measurement sensitivity is not significantly affected by temporal field
fluctuations of order 10^-4.Comment: 27 pages, 7 figure
Determination of the parameters of a Skyrme type effective interaction using the simulated annealing approach
We implement for the first time the simulated annealing method (SAM) to the
problem of searching for the global minimum in the hyper-surface of the
chi-square function which depends on the values of the parameters of a Skyrme
type effective nucleon-nucleon interaction. We undertake a realistic case of
fitting the values of the Skyrme parameters to an extensive set of experimental
data on the ground state properties of many nuclei ranging from normal to
exotic ones. The set of experimental data used in our fitting procedure
includes the radii for the valence and neutron orbits in
the O and Ca nuclei, respectively, and the breathing mode
energies for several nuclei, in addition to the typically used data on binding
energy, charge radii and spin-orbit splitting. We also include in the fit the
critical density and further constrain the values of the Skyrme
parameters by requiring that (i) the quantity ,
directly related to the slope of the symmetry energy , must be positive for
densities up to (ii) the enhancement factor , associated with
the isovector giant dipole resonance, should lie in the range of
and (iii) the Landau parameter is positive at . We
provide simple but consistent schemes to account for the center of mass
corrections to the binding energy and charge radii.Comment: 33 pages, 4 figures, Phys. Rev. C (in press
Exploring the extended density-dependent Skyrme effective forces for normal and isospin-rich nuclei to neutron stars
We parameterize the recently proposed generalized Skyrme effective force
(GSEF) containing extended density dependence. The parameters of the GSEF are
determined by the fit to several properties of the normal and isospin-rich
nuclei. We also include in our fit a realistic equation of state for the pure
neutron matter up to high densities so that the resulting Skyrme parameters can
be suitably used to model the neutron star with the "canonical" mass (). For the appropriate comparison we generate a parameter set for the
standard Skyrme effective force (SSEF) using exactly the same set of the data
as employed to determine the parameters of the GSEF. We find that the GSEF
yields larger values for the neutron skin thickness which are closer to the
recent predictions based on the isospin diffusion data. The Skyrme parameters
so obtained are employed to compute the strength function for the isoscalar
giant monopole, dipole and quadrupole resonances. It is found that in the case
of GSEF, due to the the larger value of the nucleon effective mass the values
of centroid energies for the isoscalar giant resonances are in better agreement
with the corresponding experimental data in comparison to those obtained using
the SSEF. We also present results for some of the key properties associated
with the neutron star of "canonical" mass and for the one with the maximum
mass.Comment: 45pages, 16 figure
Electromechanical tuning of vertically-coupled photonic crystal nanobeams
We present the design, the fabrication and the characterization of a tunable
one-dimensional (1D) photonic crystal cavity (PCC) etched on two
vertically-coupled GaAs nanobeams. A novel fabrication method which prevents
their adhesion under capillary forces is introduced. We discuss a design to
increase the flexibility of the structure and we demonstrate a large reversible
and controllable electromechanical wavelength tuning (> 15 nm) of the cavity
modes.Comment: 11 pages, 4 figure
New State Record and Notable Range Extension for \u3ci\u3eLibellula Semifasciata\u3c/i\u3e (Odonata: Libellulidae)
The painted skimmer, Libellula semifasciata Burmeister (Odonata: Libellulidae), is an eastern species of dragonfly that has never been documented in Iowa. In this note we report two observations and the collection of a voucher for this species in southeast Iowa in the last three years. Based on other records of this species, including those from neighboring states and more northerly latitudes, we propose that these observations are evidence of a range extension
Moving towards adaptive management of cyanotoxin-impaired water bodies
The cyanobacteria are a phylum of bacteria that have played a key role in shaping the Earth's biosphere due to their pioneering ability to perform oxygenic photosynthesis. Throughout their history, cyanobacteria have experienced major biogeochemical changes accompanying Earth's geochemical evolution over the past 2.5+ billion years, including periods of extreme climatic change, hydrologic, nutrient and radiation stress. Today, they remain remarkably successful, exploiting human nutrient over-enrichment as nuisance "blooms." Cyanobacteria produce an array of unique metabolites, the functions and biotic ramifications of which are the subject of diverse ecophysiological studies. These metabolites are relevant from organismal and ecosystem function perspectives because some can be toxic and fatal to diverse biota, including zooplankton and fish consumers of algal biomass, and high-level consumers of aquatic food sources and drinking water, including humans. Given the long history of environmental extremes and selection pressures that cyanobacteria have experienced, it is likely that that these toxins serve ecophysiological functions aimed at optimizing growth and fitness during periods of environmental stress. Here, we explore the molecular and ecophysiological mechanisms underlying cyanotoxin production, with emphasis on key environmental conditions potentially controlling toxin production. Based on this information, we offer potential management strategies for reducing cyanotoxin potentials in natural waters; for cyanotoxins with no clear drivers yet elucidated, we highlight the data gaps and research questions that are still lacking. We focus on the four major classes of toxins (anatoxins, cylindrospermopsins, microcystins and saxitoxins) that have thus far been identified as relevant from environmental health perspectives, but caution there may be other harmful metabolites waiting to be elucidated
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