382 research outputs found
An Institutional Framework for Heterogeneous Formal Development in UML
We present a framework for formal software development with UML. In contrast
to previous approaches that equip UML with a formal semantics, we follow an
institution based heterogeneous approach. This can express suitable formal
semantics of the different UML diagram types directly, without the need to map
everything to one specific formalism (let it be first-order logic or graph
grammars). We show how different aspects of the formal development process can
be coherently formalised, ranging from requirements over design and Hoare-style
conditions on code to the implementation itself. The framework can be used to
verify consistency of different UML diagrams both horizontally (e.g.,
consistency among various requirements) as well as vertically (e.g.,
correctness of design or implementation w.r.t. the requirements)
Recommended from our members
Evaluating mechanical properties of thin layers using nanoindentation and finite-element modeling: Implanted metals and deposited layers
We present a methodology based on finite-element modeling of nanoindentation data to extract reliable and accurate mechanical properties from thin, hard films and surface-modified layers on softer substrates. The method deduces the yield stress, Young`s modulus, and hardness from indentations as deep as 50% of the layer thickness
Mass Composition of Cosmic Rays in the Range 2 x 10^17 - 3 x 10^18 Measured with Haverah Park Array
At the Haverah Park Array a number of air shower observables were measured
that are relevant to the determination of the mass composition of cosmic rays.
In this paper we discuss measurements of the risetime of signals in large area
water-Cherenkov detectors and of the lateral distribution function of the
water-Cherenkov signal. The former are used to demonstrate that the CORSIKA
code, using the QGSJET98 model, gives an adequate description of the data with
a low sensitivity, in this energy range, to assumptions about primary mass. By
contrast the lateral distribution is sufficiently well measured that there is
mass sensitivity. We argue that in the range 0.2-1.0 EeV the data are well
represented with a bi-modal composition of 34+-2 % protons and the rest iron.
We also discuss the systematic errors induced by the choice of hadronic model.Comment: 16 pages, 13 figures. Accepted for publication in Astroparticle
Physic
Statistical methods applied to composition studies of ultrahigh energy cosmic rays
The mass composition of high energy cosmic rays above eV is a
crucial issue to solve some open questions in astrophysics such as the
acceleration and propagation mechanisms. Unfortunately, the standard procedures
to identify the primary particle of a cosmic ray shower have low efficiency
mainly due to large fluctuations and limited experimental observables. We
present a statistical method for composition studies based on several
measurable features of the longitudinal development of the CR shower such as
, , asymmetry, skewness and kurtosis. Principal component
analysis (PCA) was used to evaluate the relevance of each parameter in the
representation of the overall shower features and a linear discriminant
analysis (LDA) was used to combine the different parameters to maximize the
discrimination between different particle showers. The new parameter from LDA
provides a separation between primary gammas, proton and iron nuclei better
than the procedures based on only. The method proposed here was
successfully tested in the energy range from to eV even
when limitations of shower track length were included in order to simulate the
field of view of fluorescence telescopes
Vaccination with an Inactivated Virulent Feline Immunodeficiency Virus Engineered to Express High Levels of Env
An inactivated virus vaccine was prepared from a pathogenic isolate of feline immunodeficiency virus containing a mutation that eliminated an endocytic sorting signal in the envelope glycoprotein, increasing its expression on virions. Cats immunized with inactivated preparations of this modified virus exhibited strong titers of antibody to Env by enzyme-linked immunosorbent assay. Evidence of protection following challenge demonstrated the potential of this approach to lentiviral vaccination
Recommended from our members
Measurements of To Temperatures of Supersaturated Si-As Alloys
Engineering and Applied Science
Growth and Mechanical and Tribological Characterization of Multi-Layer Hard Carbon Films
Vacuum-arc deposition is used to deposit multilayer C films by modulating the sample bias during deposition. Effect of varying the sublayer thickness in multilayer films consisting of alternating layers of ``hard`` (68.4 GPa, -100 V bias) and ``soft`` (27.5 GPa, - 200 V bias) was investigated. Films consisting of equal thickness layers of hard and soft material and an individual layer thickness varying from 10 to 35 nm were deposited. Mechanical property measurements were obtained by finite element modeling of nanoindentation load-displacement curves. The film hardness values were about 20% below the average of the component layers and relatively independent of the layer thickness. TEM revealed deterioration of the multilayer structure when the sublayer thickness was below 15 nm due to implantation damage of the hard layers caused by the energetic C{sup +} ions of the soft layers (-2000 V bias) deposited over them. Pin-on-disk wear tests show that the wear rate drops when sublayer thickness is decreased below 20 nm and remains constant with further decreases in the layer thickness
Recommended from our members
Growth and mechanical and tribological characterization of multi-layer hard carbon films
Vacuum-arc deposition is used to deposit multilayer C films by modulating the sample bias during deposition. Effect of varying the sublayer thickness in multilayer films consisting of alternating layers of ``hard`` (68.4 GPa, -100 V bias) and ``soft`` (27.5 GPa, - 200 V bias) was investigated. Films consisting of equal thickness layers of hard and soft material and an individual layer thickness varying from 10 to 35 nm were deposited. Mechanical property measurements were obtained by finite element modeling of nanoindentation load-displacement curves. The film hardness values were about 20% below the average of the component layers and relatively independent of the layer thickness. TEM revealed deterioration of the multilayer structure when the sublayer thickness was below 15 nm due to implantation damage of the hard layers caused by the energetic C{sup +} ions of the soft layers (-2000 V bias) deposited over them. Pin-on-disk wear tests show that the wear rate drops when sublayer thickness is decreased below 20 nm and remains constant with further decreases in the layer thickness
Production of Medical Radioisotopes with High Specific Activity in Photonuclear Reactions with Beams of High Intensity and Large Brilliance
We study the production of radioisotopes for nuclear medicine in
photonuclear reactions or ()
photoexcitation reactions with high flux [()/s], small
diameter m and small band width () beams produced by Compton back-scattering of laser
light from relativistic brilliant electron beams. We compare them to (ion,np) reactions with (ion=p,d,) from particle accelerators like
cyclotrons and (n,) or (n,f) reactions from nuclear reactors. For
photonuclear reactions with a narrow beam the energy deposition in the
target can be managed by using a stack of thin target foils or wires, hence
avoiding direct stopping of the Compton and pair electrons (positrons).
isomer production via specially selected cascades
allows to produce high specific activity in multiple excitations, where no
back-pumping of the isomer to the ground state occurs. We discuss in detail
many specific radioisotopes for diagnostics and therapy applications.
Photonuclear reactions with beams allow to produce certain
radioisotopes, e.g. Sc, Ti, Cu, Pd, Sn,
Er, Pt or Ac, with higher specific activity and/or
more economically than with classical methods. This will open the way for
completely new clinical applications of radioisotopes. For example Pt
could be used to verify the patient's response to chemotherapy with platinum
compounds before a complete treatment is performed. Also innovative isotopes
like Sc, Cu and Ac could be produced for the first time
in sufficient quantities for large-scale application in targeted radionuclide
therapy.Comment: submitted to Appl. Phys.
Quantum cellular automata quantum computing with endohedral fullerenes
We present a scheme to perform universal quantum computation using global
addressing techniques as applied to a physical system of endohedrally doped
fullerenes. The system consists of an ABAB linear array of Group V endohedrally
doped fullerenes. Each molecule spin site consists of a nuclear spin coupled
via a Hyperfine interaction to an electron spin. The electron spin of each
molecule is in a quartet ground state . Neighboring molecular electron
spins are coupled via a magnetic dipole interaction. We find that an
all-electron construction of a quantum cellular automata is frustrated due to
the degeneracy of the electronic transitions. However, we can construct a
quantum celluar automata quantum computing architecture using these molecules
by encoding the quantum information on the nuclear spins while using the
electron spins as a local bus. We deduce the NMR and ESR pulses required to
execute the basic cellular automata operation and obtain a rough figure of
merit for the the number of gate operations per decoherence time. We find that
this figure of merit compares well with other physical quantum computer
proposals. We argue that the proposed architecture meets well the first four
DiVincenzo criteria and we outline various routes towards meeting the fifth
criteria: qubit readout.Comment: 16 pages, Latex, 5 figures, See http://planck.thphys.may.ie/QIPDDF/
submitted to Phys. Rev.
- …