Strictly Order-Preserving Maps into Z, II. A 1979 Problem of Erné

A lattice L is constructed with the property that every interval has finite height, but there exists no strictly order-preserving map from L to Z. A 1979 problem of Erné (posed at the 1981 Banff Conference on Ordered Sets) is thus solved. It is also shown that if a poset P has no uncountable antichains, then it admits a strictly order-preserving map into Z if and only if every interval has finite height.     

A fixed point theorem with applications to truncated lattices

We prove a fixed point theorem related to the set P2 of [17]. The result gives access to nontrivial infinite ordered sets with the fixed point property. We also show how the result can be used to provide an elementary proof of part of Baclawski and Björner’s results on truncated lattices.Dedicated to the memory of Ivan RivalReceived December 1, 2002; accepted in final form June 18, 2004.This revised version was published online in August 2005 with a corrected cover date.     

Tailored Porous Transport Layers for Optimal Oxygen Transport in Water Electrolyzers: Combined Stochastic Reconstruction and Lattice Boltzmann Method

The porous transport layer (PTL) plays an integral role for the mass transport in polymer electrolyte membrane (PEM) electrolyzers. In this work, a stochastic reconstruction method of titanium felt-based PTLs is applied and combined with the Lattice Boltzmann method (LBM). The aim is to parametrically investigate the impact of different PTL structures on the transport of oxygen. The structural characteristics of a reconstructed PTL agree well with experimental investigations. Moreover, the impact of PTL porosity, fiber radius, and anisotropy parameter on the structural characteristics of PTLs are analyzed, and their impact on oxygen transport are elucidated by LBM. Eventually, a customized graded PTL is reconstructed, exhibiting almost optimal mass transport performance for the removal of oxygen. The results show that a higher porosity, larger fiber radius, and smaller anisotropy parameter facilitate the formation of oxygen propagation pathways. By tailoring the fiber characteristics and thus optimizing the PTLs, guidelines for the optimal design and manufacturing can be obtained for large-scale PTLs for electrolyzers.     

Determination of new electroweak parameters at the ILC – sensitivity to new physics

We present a study of the sensitivity of the International Linear Collider (ILC) to electroweak parameters in the absence of a light Higgs boson. In particular, we consider those parameters that have been inaccessible at previous colliders, quartic gauge couplings. Within a generic effective-field theory context we analyze all processes that contain quasi-elastic weak-boson scattering, using complete six-fermion matrix elements in unweighted event samples, fast simulation of the ILC detector, and a multi-dimensional parameter fit of the set of anomalous couplings. The analysis does not rely on simplifying assumptions such as custodial symmetry or approximations such as the equivalence theorem. We supplement this by a similar new study of triple weak-boson production, which is sensitive to the same set of anomalous couplings. Including the known results on triple gauge couplings and oblique corrections, we thus quantitatively determine the indirect sensitivity of the ILC to new physics in the electroweak symmetry-breaking sector, conveniently parameterized by real or fictitious resonances in each accessible spin/isospin channel. PACS 11.30.Qc; 12.39.Fe; 12.60.Fr; 13.66.Jn     

Computational characterization of ferroelectric solids with a 3D Preisach model based on an orientation distribution function

Ferroelectric or ferromagnetic materials show an interaction between mechanical deformations and polarization or magnetization. A few multiferroic materials possess both ferroic properties and exhibit a magneto-electric (ME) coupling. These ME properties can be achieved in two-phase composites, which combine ferroelectric and ferromagnetic characteristics. To predict a realistic material behavior and a more precise ME coefficient, the application of suitable material models which describe the nonlinear hysteretic behavior is of particular importance. In the present contribution we focus on the characterization of a nonlinear ferroelectric material behavior, in terms of a 3D Preisach model based on an orientation distribution function. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Modeling of Extrinsic and Autonomous Self-Healing phenomena within the Framework of the Theory of Porous Media

In this work a multiphase model is presented to describe the damage and healing behavior of a self-healing microstructure. In this academic example a single microcapsule is enclosed in a polymeric matrix. Attention is payed to the outflow of the liquid healing agents from the capsule into the damaged area and the subsequent phase transition from liquid to solid. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Experimental and model study of the formation of chitosan-tripolyphosphate-siRNA nanoparticles

Chitosan-tripolyphosphate (TPP) nanoparticles have received great interest as a drug delivery system due to the simple and mild procedure of ionic gelation and the biocompatibility of chitosan. We have studied the formation of chitosan nano- and microparticles through ionic gelation with TPP in the absence and presence of NaCl, by measuring the kinetics of formation, particle size, and zeta potential. Depending on the experimental conditions (concentrations of chitosan and TPP and the presence or absence of NaCl), particle formation displays an exponential or a sigmoidal time dependency. In order to explain the kinetics measurements, we have set up a simple kinetics model involving four different species. The model is constructed on the basis of previously proposed mechanisms of particle formation and our measurements of particle size and kinetics of formation. The model can simulate all the different time dependencies of particle formation. We also determined the effect of small interfering RNA (siRNA) on the rate of particle formation, but apparently siRNA has little or no influence on particle formation when TPP is present.     

Study on statistically similar RVEs for real microstructures based on different statistical descriptors

A method for constructing statistically similar representative volume elements (SSRVEs) for a real dual-phase (DP) steel microstructure is presented in this contribution. The advantageous material properties of such kind of steels originate from the interaction of the microstructure constituents of the material on the microscale. In order to capture these effects directly in the material modeling, the FE² method is a suitable tool, where an RVE representing the microstructure of a material is used in the microscopic boundary value problem, which is solved at each Gauss-point of the macroscopic boundary value problem. However, RVEs based on real microstructures typically implicate high computational expenses due to the complexity of the underlying microstructure and its discretization. SSRVEs, which have a lower complexity than conventional RVEs but are still able to represent the material, can be used instead. Here, different statistical measures for the construction of SSRVEs and their comparison are the main focus. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

An efficient numerical method for fully-resolved particle simulations on high-performance computers

A numerical method for fully-resolved particle simulations on adaptively-refined Cartesian meshes is presented. When the particle size is on the order of or smaller than the smallest scales of the carrier flow, fully resolving the particle surfaces on uniform Cartesian meshes results in a tremendous computational effort. This is circumvented by locally refining the mesh near the moving particle surfaces. A new dynamic load-balancing strategy is described which enables the application of this approach to particulate turbulent flows on high-performance computers. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Shape control of piezolaminated thin-walled structures using nonlinear piezoelectric actuators

In the present paper a 2D-shell finite element model is proposed to carry out static analysis of piezolaminated composite shells by incorporating nonlinear constitutive relations in order to describe the electromechanical coupling under strong electric fields. The present shell element has 5 mechanical DOFs and 3 electrical DOFs per node. The developed composite piezolaminated shell element is employed to study the static behavior and shaping of spherical antenna reflector laminated with piezo-patches under both weak and strong electric fields. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)