bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variational‐based modeling of micro‐electro‐elasticity with electric field‐driven and stress‐driven domain evolutions
Authors: Miehe C. , Zäh D. , Rosato D. 
Published: June 2012

SUMMARYRecently, increasing interest in so‐called functional or smart materials with electromechanical coupling has been shown such as ferroelectric piezoceramics. These materials are characterized by microstructural properties, which can be changed by external stress and electric field stimuli, and hence find use as the active components in sensors and actuators. The electromechanical coupling effects result from the existence and rearrangement of microstructural domains with uniformly oriented electric polarization. The understanding and efficient simulation of these highly nonlinear and dissipative mechanisms, which occur on the microscale of ferroelectric piezoceramics, are a key challenge of the current research. This paper does not offer a substantially new physical model of these phenomena but a new mathematical modeling approach based on a rigorous exploitation of rate‐type variational principles. This provides a new insight in the structure of the coupled problem, where the governing field equations appear as the Euler equations of a variational statement. We outline a variational‐based micro‐electro‐elastic model for the microstructural evolution of both electrically and mechanically driven electric domains in ferroelectric ceramics, which also incorporates the surrounding free space. To this end, we extend recently developed multifield incremental variational principles of electromechanics from local to gradient‐extended dissipative response and specialize it by a Ginzburg–Landau‐type phase field model, where the thickness of the domain walls enters the formulation as a length scale. This serves as a natural starting point for a canonical compact, symmetric finite element implementation, considering the mechanical displacement, the microscopic polarization, and the electric potential induced by the polarization as the primary fields. The latter is defined on both the solid domain and a surrounding free space. Numerical simulations treat domain wall motions for electric field‐driven and stress‐driven loading processes, including the expansion of the electric potential into the free space. Copyright © 2012 John Wiley & Sons, Ltd.
Load identification for full‐field reconstruction: applications to plates under tension loads
Authors: Martini D. , Hochard Ch. , Charles J.‐P. 
Published: June 2012

SUMMARYThe full‐field reconstruction method presented here is suitable for real‐time structural monitoring purposes, such as improving the performances of structures. The aim is to characterize mechanical fields and boundary conditions while the structure is in service, using just a few on‐line measurements. This characterization is an ill‐posed inverse problem, the solution of which requires making some prior assumptions. The structures studied are assumed to be in steady‐state configurations and to show linear mechanical behavior, and the loading zones are assumed not to be overstressed; the mechanical fields are monitored only inside the structures. The full‐field identification is regularized using the boundary conditions, which are identified from strain measurements, and the mechanical fields are then reconstructed from these identified boundary conditions. On the basis of Saint‐Venant's principle, the boundary conditions are approximated with a few parameters, the basis functions of which are obtained from the projections of Trefftz‐like solutions onto the boundaries of the structures. These approximate boundary conditions are linked to the global mechanical responses of the structures. Lastly, this full‐field reconstruction method is applied to plate‐like structures with holes subjected to in‐plane loads. The results show that the load identification procedure efficiently regularizes the full‐field reconstruction method, and that this method is suitable for structural monitoring purposes. The sensitivity of this method to errors is similar to that of the load identification procedure, and the maximum errors in the solutions are located at the boundaries. Copyright © 2012 John Wiley & Sons, Ltd.
A multiscale component mode synthesis approach for dynamic analysis of nanostructures
Authors: Lan J. , Li G. 
Published: June 2012

SUMMARYA component mode synthesis‐based multiscale approach is developed for dynamic analysis of nanostructures. The multiscale approach decomposes a nanostructure into atomistic and continuum regions and employs vibrational modes to connect the regions of different scales, enabling a reflectionless atomistic‐to‐continuum coupling. Dynamic response of the coupled atomistic and continuum regions is computed concurrently using a common time scale. Numerical results indicate that the multiscale approach has significant condensation and scaling advantages, and it is well suited for modeling and simulation of large and complex systems. Copyright © 2012 John Wiley & Sons, Ltd.
Analysis of the incompressibility constraint in the smoothed particle hydrodynamics method
Authors: Szewc K. , Pozorski J. , Minier J.‐P. 
Published: June 2012

SUMMARYSmoothed Particle Hydrodynamics (SPH) is a particle‐based, fully Lagrangian method for fluid‐flow simulations. In this work, fundamental concepts of the method are first briefly recalled. Then, we present a thorough comparison of two different incompressibility treatments in SPH: the weakly compressible approach, where a suitably chosen equation of state is used, and the truly incompressible method (in two basic variants), where the velocity field projection onto a divergence‐free space is performed. A noteworthy aspect of the study is that in each incompressibility treatment, the same boundary conditions are used (and further developed) that allows a direct comparison to be made. Two‐dimensional and three‐dimensional validation cases are studied. Problems associated with the numerical setup are discussed, and an optimal choice of the computational parameters is proposed and verified. The efficiency issues of the incompressibility treatments are considered, and the speed‐up features are highlighted. The results show that the present state‐of‐the‐art truly incompressible methods (based on a velocity correction) suffer from density accumulation errors. To address this issue, an algorithm, based on a correction for both particle velocities and positions, is presented. The usefulness of this density correction is examined and demonstrated. Copyright © 2012 John Wiley & Sons, Ltd.
Stable imposition of stiff constraints in explicit dynamics for embedded finite element methods
Authors: Annavarapu Chandrasekhar , Hautefeuille Martin , Dolbow John E. 
Published: June 2012

SUMMARYWe investigate various strategies to enforce the kinematics at an embedded interface for transient problems within the extended finite element method. In particular, we focus on explicit time integration of the semi‐discrete equations of motion and extend both dual and primal variational frameworks for constraint enforcement to a transient regime. We reiterate the incompatibility of the dual formulation with purely explicit time integration and the severe restrictions placed by the Courant–Friedrichs–Levy condition on primal formulations. We propose an alternate, consistent formulation for the primal method and derive an estimate for the stabilization parameter, which is more amenable in an explicit dynamics framework. Importantly, the use of the new estimate circumvents the need for any tolerances as an interface approaches an element boundary. We also show that with interfacial constraints, existing mass lumping schemes can lead to prohibitively small critical time steps. Accordingly, we propose a mass lumping procedure, which provides a more favorable estimate. These techniques are then demonstrated on several benchmark numerical examples, where we compare and contrast the accuracy of the primal methods against the dual methods in enforcing the constraints. Copyright © 2012 John Wiley & Sons, Ltd.
Concurrent multiscale modeling of amorphous materials in 3D
Authors: Su Z. C. , Tan V. B. C. , Tay T. E. 
Published: June 2012

SUMMARYA general three‐dimensional concurrent multiscale modeling approach is developed for amorphous materials. The material is first constructed as a tessellation of hexahedral amorphous cells. For regions of linear deformation, the number of degrees of freedom is reduced by computing the displacements of the vertices of the amorphous cells only instead of the atoms within. This is achieved by determining, a priori, the atom displacements within such pseudoamorphous cells associated with orthogonal deformation modes of the cell. Actual atom displacements are calculated using traditional molecular mechanics for regions of nonlinear deformation. Computational implementation of the coupling between pseudoamorphous cells and molecular mechanics regions and stiffness matrix formulation are elucidated. Multiscale simulations of nanoindentation on polymer and crystalline substrates show good agreement with pure molecular mechanics simulations. Copyright © 2012 John Wiley & Sons, Ltd.
Dispersion and stability properties of radial basis collocation method for elastodynamics
Authors: Chi S.W. , Chen J.S. , Luo H. , Hu H.Y. , Wang L. 
Published: June 2012

AbstractStrong form collocation with radial basis approximation, called the radial basis collocation method (RBCM), is introduced for the numerical solution of elastodynamics. In this work, the proper weights for the boundary collocation equations to achieve the optimal convergence in elastodynamics are first derived. The von Neumann method is then introduced to investigate the dispersion characteristics of the semidiscrete RBCM equation. Very small dispersion error (< 1%) in RBCM can be achieved compared to linear and quadratic finite elements. The stability conditions of the RBCM spatial discretization in conjunction with the central difference temporal discretization are also derived. We show that the shape parameter of the radial basis functions not only has strong influence on the dispersion errors, it also has profound influence on temporal stability conditions in the case of lumped mass. Further, our stability analysis shows that, in general, a larger critical time step can be used in RBCM with central difference temporal discretization than that for finite elements with the same temporal discretization. Our analysis also suggests that although RBCM with lumped mass allows a much larger critical time step than that of RBCM with consistent mass, the later offers considerably better accuracy and should be considered in the transient analysis. © 2012 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2013
Enhanced light harvesting of Si solar cells via luminescent down‐shifting using YVO4:Bi3+, Eu3+ nanophosphors
Authors: Huang C.K. , Chen Y.C. , Hung W.B. , Chen T.M. , Sun K.W. , Chang W.‐L. 
Published: June 2012

ABSTRACTThe colloids of YVO4 nanoparticles on microtextured Si surface are demonstrated to have promising potential for efficient solar spectrum utilization in crystalline Si solar cells. The solar cells showed an enhancement of 4% in short‐circuit current density and approximately 0.7% in power conversion efficiency when coated with YVO4 nanoparticles. The properties of cells integrated with YVO4 nanoparticles were characterized to identify the role of YVO4 in improved light harvesting. The current experiments conclude that the colloids of YVO4 nanoparticles not only act as luminescent down‐shifting centers in the ultraviolet region but also serve as an antireflection coating for enhancing the light absorption in the measured spectral regime. Copyright © 2012 John Wiley & Sons, Ltd.
The temperature‐sensitive luminescence of (Y,Gd)VO4:Bi3+,Eu3+ and its application for stealth anti‐counterfeiting
Authors: Chen Lei , Zhang Yao , Luo Anqi , Liu Fayong , Jiang Yang , Hu Qingzhuo , Chen Shifu , Liu Ru‐Shi 
Published: June 2012

AbstractAnti‐counterfeiting technologies are desired to protect products far away from the violation of dummy, fake and shoddy goods. The phosphor of (Y,Gd)VO4:Bi3+,Eu3+ was synthesized for the application of this purpose. Its photoluminescence was investigated by exciting with different wavelengths at variant temperatures. Wide emission color ranged from green through yellow to orange was tuned up by tailor‐ing Bi3+ and Eu3+ concentrations. The temperature dependent luminescence and wavelength selective excitation of (Y,Gd)VO4:Bi3+,Eu3+ were observed, which provide different encryptions in anti‐counterfeiting. To verify the feasibility in application, two anti‐counterfeiting patterns were fabricated practically and excellent performance was obtained. Moreover, the physical mechanisms for the different phenomena of luminescence were elucidated from excitation spectra combining with the configuration coordinate model. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Highly Ordered Arrays of Particle‐in‐Bowl Plasmonic Nanostructures for Surface‐Enhanced Raman Scattering
Authors: Li Xianglin , Zhang Yongzhe , Shen Ze Xiang , Fan Hong Jin 
Published: June 2012

AbstractA highly ordered particle‐in‐bowl (PIB) nanostructure array is designed and fabricated to achieve large field enhancement for the surface‐enhanced Raman scattering (SERS) application. This new type of PIB structure is composed of an Ag particle located at the bottom of an Au bowl, and the two are separated by a precisely controlled nanoscale dielectric layer. The fabrication of the PIB structure is based on the self‐assembly of polystyrene spheres and atomic layer deposition (ALD), which allows good control of the metal particle size and gap distance, as well as large‐scale ordering. Numerical simulation reveals a high enhancement of the local field at the nanogaps. The SERS performance of the PIB arrays, and the effects of the Ag particle size and the ALD dielectric layer thickness are characterized, results of which are in reasonable agreement with simulation. With Rhodmaine 6G as the probe molecule, the spatially averaged SERS enhancement factor is on the order of 3.8 × 107 and the local field enhancement from simulation can be up to 108.
Lagerungstechnik für Turbopumpen
Authors: Bernhardt Helmut , Ganswindt Christoph 
Published: June 2012

AbstractDieser Beitrag gibt einen Überblick über die Entwicklung der Lagerungstechnik in Turbomolekularpumpen, kurz Turbopumpen. Neben den heute gebräuchlichen Lagerkonfigurationen werden auch ihre jeweiligen Vor‐ und Nachteile erläutert.Die Verwendung von vollständig magnetgelagerten Turbopumpen war Anfang der neunziger Jahre verschiedenen Erschwernissen unterworfen. Die abschließende Beschreibung des heutigen Standes der Technik mit den Schwerpunkten Sicherheit, Zuverlässigkeit, Anwenderfreundlichkeit, Wartungsfreiheit und Energieeffizienz zeigt, wie sich die Entwicklung der Turbopumpen nachhaltig verändert hat.
Coarse‐grained models of water
Authors: Darré Leonardo , Machado Matías R. , Pantano Sergio 
Published: June 2012

AbstractCoarse‐grained (CG) models for macromolecules have become a standard in the study of biological systems, overcoming limitations in size and time scales encountered by atomistic molecular dynamics simulations. Just as in any biomolecular ensemble, water in CG models plays a key role in mediating intermolecular and intramolecular interactions. However, owing to the highly nontrivial properties of water, important simplifications have been commonly used to treat solvation effects. Recent developments of CG models for water are overviewed, comparing some characteristic features and limitations.This article is categorized under:

Molecular and Statistical Mechanics > Free Energy Methods
Evaluation of autumn mist‐netting data for monitoring passerine populations in interior Alaska
Authors: Benson Anna‐Marie , Johnson Walter N. , Barry Ronald P. , Guers Susan L. 
Published: June 2012

AbstractWe evaluated the data from 2 autumn mist‐netting stations for monitoring passerine population trends and measuring the timing of migration. Migration‐monitoring stations were operated during autumn from 1993 to 2009 at 2 interior Alaska locations: in Fairbanks (64°50′N, 147°50′W) by the Alaska Bird Observatory (ABO) and near the Tetlin National Wildlife Refuge (NWR), Alaska, USA (63°22′N, 143°13′W) by the U.S. Fish and Wildlife Service. The location of these 2 stations, near the north and western limits of the continental landmass, provides information from the initial stages of long‐distance migration. The timing of migrant passage through ABO and Tetlin NWR were similar when all 17 years were combined. Juveniles preceded adults in 10 of 14 species at ABO and in 13 of 14 species at Tetlin NWR. Relative capture rates (log of weather‐corrected capture rates) from the ABO and Tetlin NWR stations from 1996 to 2009 were correlated for 2 of 7 species: ruby‐crowned kinglet (Regulus calendula) and yellow warbler (Dendroica petechia). A high proportion of captured birds were juveniles; therefore, these stations are most useful for monitoring an index of productivity. Power calculations indicate that for 6 of 7 species, a 50% decline in relative capture rates could be detected in a 20‐year period. These stations provide a unique contribution for monitoring passerine populations by providing a large sample of the timing of migration and productivity indices at 2 interior‐Alaska locations. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.
Ca5Ni17Ge8 – A Complex Intermetallic Compound Combining Various Structure Motifs of Alkaline‐Earth Nickel Germanides
Authors: Hlukhyy Viktor , Siggelkow Lisa , Fässler Thomas F. 
Published: June 2012

AbstractThe intermetallic compound Ca5Ni17Ge8 was prepared by arc melting mixtures of the elements and subsequent annealing under argon atmosphere. The compound crystallizes in a new structure type with the space group Amm2, Z = 2, a = 4.0255(2) Å, b = 25.226(2) Å, c = 8.9861(6) Å and wR2 = 0.083 (all data).Ca5Ni17Ge8 consists of a $\rm^{3}_{\infty}$[Ni17Ge8] network in whose cavities the calcium atoms are situated. The three‐dimensional network comprises a unusual large diversity of structural motifs that are known from other compounds of the systems Ae/Ni/Ge (Ae: Ca, Sr, Ba), such as the coordination environments of the calcium atoms reminiscent to those in Ca7Ni49Ge22 and Ca15Ni68Ge37 as well as various Ni‐Ge structural motifs which occur similarly in Ca2Ni3Ge2, BaNi2Ge, SrNi2Ge, Ni3Sn2 and Ni3Sn.
The Interactive Systems Framework Applied to the Strategic Prevention Framework: The Rhode Island Experience
Authors: Florin Paul , Friend Karen B. , Buka Stephen , Egan Crystelle , Barovier Linda , Amodei Brenda 
Published: June 2012

AbstractThe Interactive Systems Framework for Dissemination and Implementation (ISF) was introduced as a heuristic systems level model to help bridge the gap between research and practice (Wandersman et al., in Am J Commun Psychol 41:171–181, 2008). This model describes three interacting systems with distinct functions that (1) distill knowledge to develop innovations; (2) provide supportive training and technical assistance for dissemination to; (3) a prevention delivery system responsible for implementation in the field. The Strategic Prevention Framework (SPF) is a major prevention innovation launched by the Center for Substance Abuse Prevention (CSAP) of the Substance Abuse and Mental Health Services Administration (SAMHSA). The SPF offers a structured, sequential, data‐driven approach that explicitly targets environmental conditions in the community and aims for change in substance use and problems at the population level. This paper describes how the ISF was applied to the challenges of implementing the SPF in 14 Rhode Island communities, with a focus on the development of a new Training and Technical Assistance Resources Center to support SPF efforts. More specifically, we (1) describe each of the three ISF interacting systems as they evolved in Rhode Island; (2) articulate the lines of communication between the three systems; and (3) examine selected evaluation data to understand relationships between training and technical assistance and SPF implementation and outcomes.Special Issue: Advances in Bridging Research and Practice Using the Interactive System Framework for Dissemination and Implementation; Guest Editors: Abraham Wandersman, Paul Flaspohler, Catherine A. Lesesne, Richard Puddy; Action Editor: Emilie Phillips Smith
Imaging-guided lumbar facet injections: is there a difference in outcomes between low back pain patients who remember to return a postal questionnaire and those who do not?
Authors: Kremer Stefanie , Pfirrmann Christian W. A , Hodler Juerg , Peterson Cynthia K. 
Published: June 2012

Abstract
Objectives
To determine whether data obtained from patients returning postal questionnaires accurately reflect how patients receiving imaging-guided lumbar facet injections respond.

Methods
Seventy-eight patients receiving lumbar facet joint injections who returned an outcomes questionnaire (responders) were age and gender matched with 78 patients who did not return the postal questionnaire (non-responders) after facet joint injections. Baseline numerical rating scale (NRS) pain data were collected. NRS and Patients’ Global Impression of Change (PGIC) data were collected 1 month after injection by postal questionnaire or telephone interview.
Differences in NRS scores were calculated using the unpaired t-test. One level injection patients were compared to patients having ≥2 levels injected using the paired and unpaired t-test. The proportion of patients reporting significant improvement in each group was calculated.

Results
NRS scores were significantly improved compared to baseline (p = 0.0001). Thirty-eight percent of responders were significantly improved compared to 50 % of non-responders. Patients having ≥2 levels injected reported significantly higher baseline NRS scores, but by 1 month there was no difference in NRS scores between groups.

Conclusions
Patients returning postal questionnaires report a less favourable outcome. Telephone interview patients having injections at more than one level have better outcomes.

Main messages

• Patients returning postal questionnaires report worse outcomes after facet injection.
• Method of data collection should be considered when reporting treatment outcomes.
• Patients receiving facet injections at more than one level report greater levels of pain reduction.