2,522 research outputs found
A class of well-posed parabolic final value problems
This paper focuses on parabolic final value problems, and well-posedness is
proved for a large class of these. The clarification is obtained from Hilbert
spaces that characterise data that give existence, uniqueness and stability of
the solutions. The data space is the graph normed domain of an unbounded
operator that maps final states to the corresponding initial states. It induces
a new compatibility condition, depending crucially on the fact that analytic
semigroups always are invertible in the class of closed operators. Lax--Milgram
operators in vector distribution spaces constitute the main framework. The
final value heat conduction problem on a smooth open set is also proved to be
well posed, and non-zero Dirichlet data are shown to require an extended
compatibility condition obtained by adding an improper Bochner integral.Comment: 16 pages. To appear in "Applied and numerical harmonic analysis"; a
reference update. Conference contribution, based on arXiv:1707.02136, with
some further development
Toughening mechanisms in novel nano-silica epoxy polymers
A crosslinked epoxy polymer has been modified by the addition of nano-silica particles. The particles were introduced via a sol-gel technique which gave a very well dispersed phase of nanosilica particles which were about 20 nm in diameter. The glass transition temperature was unchanged by the addition of the nano-particles, but both the modulus and toughness were increased. The fracture energy increased from 100 J/m2 for the unmodified epoxy to 460 J/m2 for the epoxy with 13 vol% of nano-silica. The microscopy studies showed evidence of debonding of the nano-particles and subsequent plastic void growth of the epoxy polymer. A theoretical model of plastic void growth was used to confirm this mechanism
An intra ruminal heat exchanger for use in large concious animals
A method is described whereby it is possible to alter total body core temperature independently of environmetal temperature and/or exercise in conscious reindeer. The method employs the use of a simple heat exchanger introduced through a permanent rumen fistula. The heat exchanger consists of a 7 m long coil of flexible plastic tubing (OD, 10.0 mm, ID, 8.0 mm). By perfusing the tubing with thermostatically controlled water, heat can be added to or subtracted from the body core at rates equalling several times resting heat production. It is suggested that the method could be used in any large ruminant species.En intra-rumenal varmeveksler til bruk i større, uanesteserte dyr.Abstract in Norwegian / Sammendrag: Vi har i denne undersøkelsen beskrevet en metode for hvordan kroppstemperatur hos uanesteserte reinsdyr kan endres uavhengig av omgivelsestemperatur og om dyret løper eller ikke. Metoden innebærer bruk av en enkel varmeveksler som plasseres i dyrets vom gjennom en permanent vom-fistel. Varmeveksleren består av en 7 m lang kveil av fleksibel plastslange (ytre diameter 10.0 mm, indre diameter 8.0 mm). Ved å perfundere slangen med vann av en bestemt temperatur er det mulig å fjerne eller tilføre kroppen en varmemengde som tilsvarer flere ganger dyrets varmeproduksjon. Vi mener at denne metoden kan tilpasses alle store drøvtyggere.Potsiin asetettavan låmpotilan muuttajan kåytto suurilla nukkumattomilla elåimillå.Abstract in Finnish / Yhteenveto: Tutkimuksessa olemme kuvanneet menetelman, jolla voidaan muuttaa nukuttamattoman poron ruumiinlåmpotilaa riippumatta ulkolampotilasta tai siita juokseeko elåin vai ei. Menetelmassa kåytaan yksinkertaista låmpotilan muuttajaa, joka asetetaan elaimeen pysyyan potsifistulan kautta. Låmpotilan muuttaja kasittåa 7 m pitkan muoviletkurullan (letkun halkaisija 10.6 mm, reian halkaisija" 8.0 mmJTTayttåmålla letku tietyn lampoisellå vedella on mahdollista joko laskea tai nostaa ruumiin lampomååråa niin, etta se vastaa moninkertaisesti elaimen omaa låmmontuottoa. Oletamme, etta menetelmåa voidaan kayttaå kaikille suurille mårehtijoille
Implementing Goal Setting Activities with LD Adolescents
This research was published by the KU Center for Research on Learning, formerly known as the University of Kansas Institute for Research in Learning Disabilities.In this study, LD adolescents were taught to set realistic goals, to expend effort to achieve the goals, and to accept responsibility for achieving or failing to achieve their goals. The intervention produced a significant increase in the number of students exhibiting realistic goal setting strategies. During training, LD students produced a significantly greater number of effort attributions than ability, task difficulty, or luck attributions. The treatment group also increased internal attributions
Spin-dynamic field coupling in strongly THz driven semiconductors : local inversion symmetry breaking
We study theoretically the optics in undoped direct gap semiconductors which
are strongly driven in the THz regime. We calculate the optical sideband
generation due to nonlinear mixing of the THz field and the near infrared
probe. Starting with an inversion symmetric microscopic Hamiltonian we include
the THz field nonperturbatively using non-equilibrium Green function
techniques. We find that a self induced relativistic spin-THz field coupling
locally breaks the inversion symmetry, resulting in the formation of odd
sidebands which otherwise are absent.Comment: 8 pages, 6 figure
An Application of Attribution Theory to Developing Self-Esteem in Learning Disabled Adolescents
This research was published by the KU Center for Research on Learning, formerly known as the University of Kansas Institute for Research in Learning Disabilities.The study found that LD adolescents did not differ significantly from non-LD adolescents in their esponses to general self esteem and attribution questionnaires. Effort attribution training brought no significant increase in effort attributions for the experimental group of LD students. LD students reported the effort was a factor that explained success or failure in achievement tasks, but also reported that factors other than effort explained their personal success or failure on a specific spelling task
Multiplication and Composition in Weighted Modulation Spaces
We study the existence of the product of two weighted modulation spaces. For
this purpose we discuss two different strategies. The more simple one allows
transparent proofs in various situations. However, our second method allows a
closer look onto associated norm inequalities under restrictions in the Fourier
image. This will give us the opportunity to treat the boundedness of
composition operators.Comment: 49 page
A Graph-Based Semantics Workbench for Concurrent Asynchronous Programs
A number of novel programming languages and libraries have been proposed that
offer simpler-to-use models of concurrency than threads. It is challenging,
however, to devise execution models that successfully realise their
abstractions without forfeiting performance or introducing unintended
behaviours. This is exemplified by SCOOP---a concurrent object-oriented
message-passing language---which has seen multiple semantics proposed and
implemented over its evolution. We propose a "semantics workbench" with fully
and semi-automatic tools for SCOOP, that can be used to analyse and compare
programs with respect to different execution models. We demonstrate its use in
checking the consistency of semantics by applying it to a set of representative
programs, and highlighting a deadlock-related discrepancy between the principal
execution models of the language. Our workbench is based on a modular and
parameterisable graph transformation semantics implemented in the GROOVE tool.
We discuss how graph transformations are leveraged to atomically model
intricate language abstractions, and how the visual yet algebraic nature of the
model can be used to ascertain soundness.Comment: Accepted for publication in the proceedings of FASE 2016 (to appear
Density Matrix Functional Calculations for Matter in Strong Magnetic Fields: I. Atomic Properties
We report on a numerical study of the density matrix functional introduced by
Lieb, Solovej and Yngvason for the investigation of heavy atoms in high
magnetic fields. This functional describes {\em exactly} the quantum mechanical
ground state of atoms and ions in the limit when the nuclear charge and the
electron number tend to infinity with fixed, and the magnetic field
tends to infinity in such a way that . We have
calculated electronic density profiles and ground state energies for values of
the parameters that prevail on neutron star surfaces and compared them with
results obtained by other methods. For iron at G the ground state
energy differs by less than 2 \% from the Hartree-Fock value. We have also
studied the maximal negative ionization of heavy atoms in this model at various
field strengths. In contrast to Thomas-Fermi type theories atoms can bind
excess negative charge in the density matrix model. For iron at G
the maximal excess charge in this model corresponds to about one electron.Comment: Revtex, 13 pages with 6 eps figures include
Locally rigid, vessel-based registration for laparoscopic liver surgery
Purpose: Laparoscopic liver resection has significant advantages over open surgery due to less patient trauma and faster recovery times, yet is difficult for most lesions due to the restricted field of view and lack of haptic feedback. Image guidance provides a potential solution but is challenging in a soft deforming organ such as the liver. In this paper, we therefore propose a laparoscopic ultrasound (LUS) image guidance system and study the feasibility of a locally rigid registration for laparoscopic liver surgery.
Methods: We developed a real-time segmentation method to extract vessel centre points from calibrated, freehand, electromagnetically tracked, 2D LUS images. Using landmark-based initial registration and an optional iterative closest point (ICP) point-to-line registration, a vessel centre-line model extracted from preoperative computed tomography (CT) is registered to the ultrasound data during surgery.
Results: Using the locally rigid ICP method, the RMS residual error when registering to a phantom was 0.7 mm, and the mean target registration error (TRE) for two in vivo porcine studies was 3.58 and 2.99 mm, respectively. Using the locally rigid landmark-based registration method gave a mean TRE of 4.23 mm using vessel centre lines derived from CT scans taken with pneumoperitoneum and 6.57 mm without pneumoperitoneum.
Conclusion: In this paper we propose a practical image-guided surgery system based on locally rigid registration of a CT-derived model to vascular structures located with LUS. In a physical phantom and during porcine laparoscopic liver resection, we demonstrate accuracy of target location commensurate with surgical requirements. We conclude that locally rigid registration could be sufficient for practically useful image guidance in the near future
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