4,227 research outputs found
Boundary regularity for the Poisson equation in reifenberg-flat domains
This paper is devoted to the investigation of the boundary regularity for the
Poisson equation {{cc} -\Delta u = f & \text{in} \Omega u= 0 & \text{on}
\partial \Omega where belongs to some and is a
Reifenberg-flat domain of More precisely, we prove that given an
exponent , there exists an such that the
solution to the previous system is locally H\"older continuous provided
that is -Reifenberg-flat. The proof is based on
Alt-Caffarelli-Friedman's monotonicity formula and Morrey-Campanato theorem
A Generalization of Connes-Kreimer Hopf Algebra
``Bonsai'' Hopf algebras, introduced here, are generalizations of
Connes-Kreimer Hopf algebras, which are motivated by Feynman diagrams and
renormalization. We show that we can find operad structure on the set of
bonsais. We introduce a new differential on these bonsai Hopf algebras, which
is inspired by the tree differential. The cohomologies of these are computed
here, and the relationship of this differential with the appending operation
of Connes-Kreimer Hopf algebras is investigated
A flow disturbance estimation and rejection strategy for multirotors with round-trip trajectories
This paper presents a round-trip strategy of multirotors subject to unknown
flow disturbances. During the outbound flight, the vehicle immediately utilizes
the wind disturbance estimations in feedback control, as an attempt to reduce
the tracking error. During this phase, the disturbance estimations with respect
to the position are also recorded for future use. For the return flight, the
disturbances previously collected are then routed through a feedforward
controller. The major assumption here is that the disturbances may vary over
space, but not over time during the same mission. We demonstrate the
effectiveness of this feedforward strategy via experiments with two different
types of wind flows; a simple jet flow and a more complex flow. To use as a
baseline case, a cascaded PD controller with an additional feedback loop for
disturbance estimation was employed for outbound flights. To display our
contributions regarding the additional feedforward approach, an additional
feedforward correction term obtained via prerecorded data was integrated for
the return flight. Compared to the baseline controller, the feedforward
controller was observed to produce 43% less RMSE position error at a vehicle
ground velocity of 1 m/s with 6 m/s of environmental wind velocity. This
feedforward approach also produced 14% less RMSE position error for the complex
flows as well
Effect of fibronectin on the binding of antithrombin III to immobilized heparin
An objective of this research is to verify the mechanism of anticoagulant activity of surface-immobilized heparin in the presence of plasma proteins. The competition and binding interaction between immobilized heparin and antithrombin III (ATIII)/thrombin have been described in vitro. However, the strong ionic character of heparin leads to its specific and nonspecific binding with many other plasma proteins. Most notably, fibronectin contains six active binding sites for heparin which may interfere with the subsequent binding of heparin with ATIII or thrombin. \ud
Heparin was covalently immobilized through polyethylene oxide (PEO) hydrophilic spacer groups onto a model surface synthesized by random copolymerization of styrene and p-aminostyrene. The binding interaction of immobilized heparin with ATIII was then determined in the presence of different fibronectin concentrations. The binding interaction was studied by first binding immobilized heparin with ATIII, followed by the introduction of fibronectin; heparin binding with fibronectin, followed by incubation with ATIII, and simultaneous incubation of surface immobilized heparin with ATIII and fibronectin. The extent of ATIII binding to heparin in each experiment was assayed using a chromogenic substrate for ATIII, S-2238. \ud
The results of this study demonstrate that the displacement of ATIII from immobilized heparin was proportional to the fibronectin concentration, and was reversible. Furthermore, the binding sequence did not play a role in the final concentration of ATIII bound to immobilized heparin
Modeling, system identification, and control of ASTREX
The modeling, system identification and controller design aspects of the ASTREX precision space structure are presented in this work. Modeling of ASTREX is performed using NASTRAN, TREETOPS and I-DEAS. The models generated range from simple linear time-invariant models to nonlinear models used for large angle simulations. Identification in both the time and frequency domains are presented. The experimental set up and the results from the identification experiments are included. Finally, controller design for ASTREX is presented. Simulation results using this optimal controller demonstrate the controller performance. Finally the future directions and plans for the facility are addressed
The EPOCH Project: I. Periodic variable stars in the EROS-2 LMC database
The EPOCH (EROS-2 periodic variable star classification using machine
learning) project aims to detect periodic variable stars in the EROS-2 light
curve database. In this paper, we present the first result of the
classification of periodic variable stars in the EROS-2 LMC database. To
classify these variables, we first built a training set by compiling known
variables in the Large Magellanic Cloud area from the OGLE and MACHO surveys.
We crossmatched these variables with the EROS-2 sources and extracted 22
variability features from 28 392 light curves of the corresponding EROS-2
sources. We then used the random forest method to classify the EROS-2 sources
in the training set. We designed the model to separate not only Scuti
stars, RR Lyraes, Cepheids, eclipsing binaries, and long-period variables, the
superclasses, but also their subclasses, such as RRab, RRc, RRd, and RRe for RR
Lyraes, and similarly for the other variable types. The model trained using
only the superclasses shows 99% recall and precision, while the model trained
on all subclasses shows 87% recall and precision. We applied the trained model
to the entire EROS-2 LMC database, which contains about 29 million sources, and
found 117 234 periodic variable candidates. Out of these 117 234 periodic
variables, 55 285 have not been discovered by either OGLE or MACHO variability
studies. This set comprises 1 906 Scuti stars, 6 607 RR Lyraes, 638
Cepheids, 178 Type II Cepheids, 34 562 eclipsing binaries, and 11 394
long-period variables. A catalog of these EROS-2 LMC periodic variable stars
will be available online at http://stardb.yonsei.ac.kr and at the CDS website
(http://vizier.u-strasbg.fr/viz-bin/VizieR).Comment: 18 pages, 20 figures, suggseted language-editing by the A&A editorial
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