2,028 research outputs found
Rheological and Mechanical Gradient Properties of Polyurethane Elastomers for 3D-Printing with Reactive Additives
Polyurethane (PU) elastomers with their broad range of strength and elasticity are ideal materials for additive manufacturing of shapes with gradients of mechanical properties. By adjusting the mixing ratio of different polyurethane reactants during 3D-printing it is possible to change the mechanical properties. However, to guarantee intra- and inter-layer adhesion, it is essential to know the reaction kinetics of the polyurethane reaction, and to be able to influence the reaction speed in a wide range. In this study, the effect of adding three different catalysts and two inhibitors to the reaction of polyurethane elastomers were studied by comparing the time of crossover points between storage and loss modulus GâČ and GâČâČ from time sweep tests of small amplitude oscillatory shear at 30°C. The time of crossover points is reduced with the increasing amount of catalysts, but only the reaction time with one inhibitor is significantly delayed. The reaction time of 90% NCO group conversion calculated from the FTIR-spectrum also demonstrates the kinetics of samples with different catalysts. In addition, the relation between the conversion as determined from FTIR spectroscopy and the mechanical properties of the materials was established. Based on these results, it is possible to select optimized catalysts and inhibitors for polyurethane 3D-printing of materials with gradients of mechanical properties.DFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische UniversitĂ€t Berli
A simple operational interpretation of the fidelity
This note presents a corollary to Uhlmann's theorem which provides a simple
operational interpretation for the fidelity of mixed states.Comment: 1 pag
Probability distributions consistent with a mixed state
A density matrix may be represented in many different ways as a
mixture of pure states, \rho = \sum_i p_i |\psi_i\ra \la \psi_i|. This paper
characterizes the class of probability distributions that may appear in
such a decomposition, for a fixed density matrix . Several illustrative
applications of this result to quantum mechanics and quantum information theory
are given.Comment: 6 pages, submitted to Physical Review
Complex Numbers, Quantum Mechanics and the Beginning of Time
A basic problem in quantizing a field in curved space is the decomposition of
the classical modes in positive and negative frequency. The decomposition is
equivalent to a choice of a complex structure in the space of classical
solutions. In our construction the real tunneling geometries provide the link
between the this complex structure and analytic properties of the classical
solutions in a Riemannian section of space. This is related to the Osterwalder-
Schrader approach to Euclidean field theory.Comment: 27 pages LATEX, UCSBTH-93-0
Innovation and Efficiency
Innovation is a complex phenomenon that involves all spheres of technological, economic, and social activity, from research and development to investment, production, and application. In the management of innovation the relationship between innovation and efficiency is the key issue. In this report, therefore, we elaborate on a method for measuring efficiency in the innovation process. The core of our concept of efficiency is the link between the efficiency of the production unit that has adopted an innovation (dynamic efficiency) and the efficiency of the entire production field within which production units must act (average efficiency). The development of relative efficiency is connected to differences between basic, improvement-related, and pseudo innovations and to the decision-making environment for managers.
Factors influencing innovative activities follow a continuum of efficacy ranging from inhibiting to strongly promoting innovative activities. Looking at the innovation process from the standpoint of the innovating system, we distinguish major determinants of performance and them compare the performance of industrial organizations through a profile showing these determinants in research and development, production, and marketing and in management at all stages
Process Design for Electromagnetic Forming of Magnesium Alloy AZ31 Using FE Simulation
Magnesium wrought alloys are outstanding lightweight materials due to their low density
and high specific strength. The low formability of magnesium wrought alloy AZ31 at room
temperature is increased by electromagnetic forming in comparison to quasi-static
forming. For a detailed study of electro-magnetic process a coupled FE simulation must be
performed. In this paper the process design for electromagnetic forming of magnesium
wrought alloy AZ1 using FE simulation is presented.
The complexity of an electromagnetic forming process requires the illustration of
magnetic, thermal and structural dynamic domains. Moreover, it is also necessary to
illustrate the electromagnetic resonant circuit RLC. Short processing time and the strong
dependence of the physical domains to each other requires a coupled FE simulation.
The illustration of resonant circuit and the resulting formation of magnetic field is
carried out in two-dimensional rotationally symmetric model in ANSYS MAPDL using a
suitable material model. As a result time-dependent and location-dependent eddy currents
and Lorentz forces are estimated.
Subsequently, the transmission of the estimated Lorentz forces and joule heat
generation rates to ANSYS LS-DYNA is done. Due to the rotational symmetry of 2D ANSYS
MAPDL model a transformation of the loads on 3D structures can be realized. The
formation of an optimum deformation of a work piece in dependence of a defined die has
been carried out. Here, the influence of different coil designs, die materials and geometries
and RLC parameters was investigated
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Lens Rigidity for a Particle in a YangâMills Field
We consider the motion of a classical colored spinless particle under the
influence of an external Yang-Mills potential on a compact manifold with
boundary of dimension . We show that under suitable convexity
assumptions, we can recover the potential , up to gauge transformations,
from the lens data of the system, namely, scattering data plus travel times
between boundary points
Fidelity and Concurrence of conjugated states
We prove some new properties of fidelity (transition probability) and
concurrence, the latter defined by straightforward extension of Wootters
notation. Choose a conjugation and consider the dependence of fidelity or of
concurrence on conjugated pairs of density operators. These functions turn out
to be concave or convex roofs. Optimal decompositions are constructed. Some
applications to two- and tripartite systems illustrate the general theorem.Comment: 10 pages, RevTex, Correction: Enlarged, reorganized version. More
explanation
Renyi generalizations of the conditional quantum mutual information
The conditional quantum mutual information of a tripartite state
is an information quantity which lies at the center of many
problems in quantum information theory. Three of its main properties are that
it is non-negative for any tripartite state, that it decreases under local
operations applied to systems and , and that it obeys the duality
relation for a four-party pure state on systems . The
conditional mutual information also underlies the squashed entanglement, an
entanglement measure that satisfies all of the axioms desired for an
entanglement measure. As such, it has been an open question to find R\'enyi
generalizations of the conditional mutual information, that would allow for a
deeper understanding of the original quantity and find applications beyond the
traditional memoryless setting of quantum information theory. The present paper
addresses this question, by defining different -R\'enyi generalizations
of the conditional mutual information, some of which we can
prove converge to the conditional mutual information in the limit
. Furthermore, we prove that many of these generalizations
satisfy non-negativity, duality, and monotonicity with respect to local
operations on one of the systems or (with it being left as an open
question to prove that monotoniticity holds with respect to local operations on
both systems). The quantities defined here should find applications in quantum
information theory and perhaps even in other areas of physics, but we leave
this for future work. We also state a conjecture regarding the monotonicity of
the R\'enyi conditional mutual informations defined here with respect to the
R\'enyi parameter . We prove that this conjecture is true in some
special cases and when is in a neighborhood of one.Comment: v6: 53 pages, final published versio
Inverse Diffusion Theory of Photoacoustics
This paper analyzes the reconstruction of diffusion and absorption parameters
in an elliptic equation from knowledge of internal data. In the application of
photo-acoustics, the internal data are the amount of thermal energy deposited
by high frequency radiation propagating inside a domain of interest. These data
are obtained by solving an inverse wave equation, which is well-studied in the
literature. We show that knowledge of two internal data based on well-chosen
boundary conditions uniquely determines two constitutive parameters in
diffusion and Schroedinger equations. Stability of the reconstruction is
guaranteed under additional geometric constraints of strict convexity. No
geometric constraints are necessary when internal data for well-chosen
boundary conditions are available, where is spatial dimension. The set of
well-chosen boundary conditions is characterized in terms of appropriate
complex geometrical optics (CGO) solutions.Comment: 24 page
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