14,520 research outputs found
Multi-field modelling and simulation of large deformation ductile fracture
In the present contribution we focus on a phase-field approach to ductile fracture applied to large deformation contact problems. Phase-field approaches to fracture allow for an efficient numerical investigation of complex three-dimensional fracture problems, as they arise in contact and impact situations. To account for large deformations the underlying formulation is based on a multiplicative decomposition of the deformation gradient into an elastic and plastic part. Moreover, we make use of a fourth-order crack regularization combined with gradient plasticity. Eventually, a demonstrative example shows the capability of the proposed framework
Lepton Mass Effects in Single Pion Production by Neutrinos
We reconsider the Feynman-Kislinger-Ravndal model applied to
neutrino-excitation of baryon resonances. The effects of lepton mass are
included, using the formalism of Kuzmin, Lyubushkin and Naumov. In addition we
take account of the pion-pole contribution to the hadronic axial vector
current. Application of this new formalism to the reaction nu(mu) + p --> mu +
Delta at E(nu) approx 1 GeV gives a suppressed cross section at small angles,
in agreement with the screening correction in Adler's forward scattering
theorem. Application to the process nu(tau) + p --> tau + Delta at E(nu) approx
7 GeV leads to the prediction of right-handed tau polarization for
forward-going leptons, in line with a calculation based on an isobar model. Our
formalism represents an improved version of the Rein-Sehgal model,
incorporating lepton mass effects in a manner consistent with PCAC.Comment: 14 pages, 5 figures. Typos in eq. 9 and 27 corrected. Numbers in
table I for coherent cross sections (RSA and RSC) corrected (normalization
error). Figs 3 and 4 changed accordingly. These corrections also apply to the
published version PRD 76, 113004 (2007
Regular Incidence Complexes, Polytopes, and C-Groups
Regular incidence complexes are combinatorial incidence structures
generalizing regular convex polytopes, regular complex polytopes, various types
of incidence geometries, and many other highly symmetric objects. The special
case of abstract regular polytopes has been well-studied. The paper describes
the combinatorial structure of a regular incidence complex in terms of a system
of distinguished generating subgroups of its automorphism group or a
flag-transitive subgroup. Then the groups admitting a flag-transitive action on
an incidence complex are characterized as generalized string C-groups. Further,
extensions of regular incidence complexes are studied, and certain incidence
complexes particularly close to abstract polytopes, called abstract polytope
complexes, are investigated.Comment: 24 pages; to appear in "Discrete Geometry and Symmetry", M. Conder,
A. Deza, and A. Ivic Weiss (eds), Springe
Optimal control of a qubit coupled to a non-Markovian environment
A central challenge for implementing quantum computing in the solid state is
decoupling the qubits from the intrinsic noise of the material. We investigate
the implementation of quantum gates for a paradigmatic, non-Markovian model: A
single qubit coupled to a two-level system that is exposed to a heat bath. We
systematically search for optimal pulses using a generalization of the novel
open systems Gradient Ascent Pulse Engineering (GRAPE) algorithm. We show and
explain that next to the known optimal bias point of this model, there are
optimal shapes which refocus unwanted terms in the Hamiltonian. We study the
limitations of controls set by the decoherence properties. This can lead to a
significant improvement of quantum operations in hostile environments.Comment: 5 pages, 3 figures, improved pulse shape
Biotic indicators of carabid species richness on organically and conventionally managed arable fields
Carabids, a species rich arthropod family, potentially contribute much to biodiversity in agroecosystems, but assessing and monitoring carabid diversity is costly and time consuming. Therefore, this study aimed at finding more easily measurable parameters indicating high carabid diversity within organic and conventional management systems. Cover and number of weed species as well as activity density of single carabid species and of total carabids were investigated as potential indicators of carabid species richness. The study was carried out near Reckenfeld in Westphalia on sandy Plaggenesch soils. Three organically and four conventionally managed fields (cereals and corn) were investigated at the field margins and in the field centres from April to August 1999. Additionally, data of carabid catches and weed flora in winter cereals from an extended study in Düren (Northrhine-Westphalia) were reanalysed to validate the results. However, neither of the potential indicators showed consistently significant positive correlation with carabid diversity. This is partly attributed to the low variability of management conditions within the management systems in the studies presented
Conversion efficiency and luminosity for gamma-proton colliders based on the LHC-CLIC or LHC-ILC QCD Explorer scheme
Gamma-proton collisions allow unprecedented investigations of the low x and
high regions in quantum chromodynamics. In this paper, we investigate
the luminosity for "ILC"LHC ( TeV) and
"CLIC"LHC ( TeV) based colliders. Also
we determine the laser properties required for high conversion efficiency.Comment: 16, 6 figure
Homes for Life & Other Stories The Use and Evaluation of Design Fiction as a Means to Understand Sensitive Settings: a Case Study of Exploring Technologies for Dementia Care
Design fictions are used in HCI to position emerging technologies in fictional future worlds, through which the complexities of our relationships with technologies can be represented, explored and experienced. They promise to stimulate discussions about sensitive topics, such as the future of technology-enabled care, a complex area with contrasting emotional, social and practical views and wishes. However, the term design fiction is currently associated with a wide range of uses, and artefacts. It is also linked to contrasting philosophies and frameworks, which are often not made explicit, as I show in an initial survey with practitioners. This makes it difficult to identify what makes a design fiction good or effective for different purposes. This thesis aims to answer the research question: How can design fiction be used and evaluated in understanding sensitive settings? I turn to the Constructive Design Research framework and adapt it to classify how design fiction is used in HCI. I outline how design fiction can be used in the showroom approach, where it is most commonly placed, but also how it can be used as a lab and field approach to gather insights into the responses to design fictions. I developed design fictions and explored how they can be used to further discussions around the use of monitoring technologies in dementia care: an area challenging to research because of ethical issues associated with deployment studies of prototype technologies. The contribution of this thesis is threefold: first, a methodological contribution into the use of design fiction in HCI and an evaluation of the Constructive Design Research framework as a means to classify research through design fiction. Second, insights into participants’ views and wishes about technology-led care in regards to dementia. Third, a design contribution of artefacts that can be used to stimulate further debate around the topic
An approach to metal fatigue
Cumulative fatigue damage based on investigation of fatigue limit associated with crack, crack propagation rate, and stress interaction cycle in metal
- …