bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aggregation‐Induced Luminescence of Polyisobutene Succinic Anhydrides and Imides
Authors: Pucci Andrea , Rausa Riccardo , Ciardelli Francesco 
Published: March 2008

AbstractPIB derivatives such as PIBSAs and the corresponding PIBSIs characterized by different contents of functional groups were prepared. They showed luminescence both in their neat form and in heptane solution when the amount of functional groups per polymer chain was higher than a critical value. This behavior is attributed to aggregation‐induced emission, a phenomenon caused by the aggregation of non‐emissive chromophoric carbonyl groups present on PIB derivatives. AIE was studied in heptane solution as a function of the type (SAs or succinimides) and number of interacting functional groups. The results suggest that fluorescence measurements might be an effective tool to determine the degree of functionalization of PIB derivatives.magnified image
Preparation of pH‐Responsive Hydrophilic Core‐Shell Particles for Encapsulation of Water‐Soluble Material
Authors: Park Young‐Ho , Han Joo‐Hyun , Suh Kyung‐Do 
Published: March 2008

AbstractDual pH‐responsive PAAc/ PVAm core‐shell particles to encapsulate water‐soluble material were prepared through the deposition of PVAm on the surface of PAAc core particles. The structural characteristics of the core‐shell particles were confirmed by SEM and CLSM. To investigate the release profiles of the core‐shell particles and PAAc core, methylene blue, which is a cationic water‐soluble dye, was introduced. Release profiles were dominantly affected by the core swelling behavior at different pH values. The release rate of the core‐shell was less than the PAAc core, indicating that it is affected by ionic interactions between the particle and the cationic dye.magnified image
Addition Polymers of Strained Cyclic Olefins – Transition Metal Catalysed Polymerisations of the Cyclobutene Derivative Bicyclo[3.2.0]hept‐6‐ene
Authors: Curran Katherine , Risse Wilhelm , Boggioni Laura , Tritto Incoronata 
Published: March 2008

AbstractBicyclo[3.2.0]hept‐6‐ene was converted into the corresponding addition polymer poly(6,7‐bicyclo[3.2.0]heptylene) with the aid of early and late transition metal based olefin polymerisation catalysts. Moderate to very good yields (42–99%) of polymer were obtained with [Pd(NCEt)4][BF4]2, [(η3‐allyl)Pd(solv)2][SbF6], [(2,9‐dimethyl‐1,10‐phenanthroline)Pd(CH3)(NC(CH2)6CH3)][SbF6], and Cp2ZrCl2/MAO, using monomer to transition metal ratios between 50/1 and 250/1. Reaction occurs at the olefin π‐bond, and the four‐membered ring of the monomer is retained during polymerisation which differs from ring‐opening olefin metathesis polymerisation in which the four‐membered ring is opened. The nearly exclusively saturated structure of the polymer was confirmed by 1H and 13C NMR spectroscopy. It is proposed that the polymers consist of repeating units that are predominantly cis‐exo‐enchained. GPC analysis of the soluble polymers prepared with [Pd(NCEt)4][BF4]2 showed that the molecular mass values $\overline M _{\rm n}$(GPC) were in the range of 3 700 to 22 600.magnified image
Novel High‐Performance Talc/Poly[(butylene adipate)‐co‐terephthalate] Hybrid Materials
Authors: Raquez Jean Marie , Nabar Yogaraj , Narayan Ramani , Dubois Philippe 
Published: March 2008

AbstractNew talc/PBAT hybrid materials were prepared through reactive extrusion. First, PBAT was free‐radically grafted with MA to improve the interfacial adhesion between PBAT and talc. Then, the resulting MA‐g‐PBAT was reactively melt‐blended with talc through esterification reactions of MA moieties with the silanol functions from talc. Sn(Oct)2 and DMAP were used as catalysts. Interestingly, the tensile properties for these compatibilized composites were improved due to a better interfacial adhesion between both partners. XPS showed the formation of covalent ester bonds between the silanol functions from talc particles, and the MA moieties grafted onto the polyester backbones.magnified image
A Very Useful Redox Initiator for Aqueous RAFT Polymerization of N‐Isopropylacrylamide and Acrylamide at Room Temperature
Authors: Bai Wei , Zhang Liang , Bai Ruke , Zhang Guangzhao 
Published: March 2008

AbstractReversible addition fragmentation chain transfer (RAFT) polymerizations of N‐isopropylacrylamide (NIPAM), and acrylamide (AM) were successfully performed in aqueous media at ambient temperature using a redox initiator, potassium persulfate (K2S2O8), and sodium thiosulfate (Na2S2O3). The molecular weight of the polymers obtained increases linearly with monomer conversion, molecular weight distribution is narrow even at high conversion (>90%), and a linear relationship exists between ln([M]0/[M]) and polymerization time. Moreover, self‐chain extension reaction also proceeded successfully. All the results demonstrate that K2S2O8–Na2S2O3 is a very efficient initiating system for the RAFT polymerizations of NIPAM and AM in aqueous media at room temperature.magnified image
Controlled Array of Ferritin in Tubular Nanostructure
Authors: Kim Min Sup , Shin Kwang Min , Kim Sun I. , Spinks Geoffrey M. , Kim Seon Jeong 
Published: March 2008

AbstractWe have demonstrated that uniform and continuous poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid) (PAMPS) tubular core‐shell nanostructures containing linear features of ferritin nanoparticles can be directly fabricated using two immiscible solutions employing coaxial electrospinning. By adjusting the concentration of PAMPS as the outer solution in the coaxial electrospinning process, the width of a one dimensional (1D) array of ferritin could be accurately controlled. We demonstrate the formation of a nearly linear chain of individual ferritin particles encapsulated in a PAMPS nanofiber of 40 nm diameter. The ability to accurately control the width of the ferritin 1D arrays encapsulated in tubular nanostructures is a key component in determining the efficiency and performance of nanodevices. The demonstrated method of forming tubular nanostructures containing inner 1D particle arrays can also be extended to other materials with potential applications in nanoelectronic devices, such as nanobiosensors and batteries.magnified image
Low‐Band Gap Polymeric Cyanine Dyes Absorbing in the NIR Region
Authors: Geiger Thomas , Benmansour Hadjar , Fan Bin , Hany Roland , Nüesch Frank 
Published: March 2008

AbstractTwo new, fully conjugated polymeric cyanine dyes based on trimethine and heptamethine moieties have been synthesized. Both polymers were characterized by gel permeation chromatography, UV‐vis and IR spectroscopy, elementary analysis and cyclic voltammetry. The structure of one material could be confirmed with NMR spectroscopy. Upon head‐to‐tail coupling of the dye moieties distinct bathochromic shifts up to 159 nm were observed for the polymers which absorb solely in the near infrared (NIR) region with maxima up to 1 002 nm and very high molar absorption coefficients. This highly efficient absorption in the NIR spectral domain combined with the strong electron accepting properties makes these dyes interesting candidates for many optical applications; investigations on photovoltaic devices based on polymeric cyanine dye/C60 heterojunctions identify one of these possibilities.magnified image
Fatigue strength estimation of butt welded joints in magnesium AZ31 alloy using the genetic algorithm
Authors: Karakas Ö. , Canyurt O. E. , Gulsoz A. 
Published: March 2008

AbstractGenetic Algorithm is applied to calculate the substitute structural length (SSL) and obtain the fatigue strength of welded joints in magnesium. Fatigue tests with unnotched and notched specimens of the base material metal (BM), the weld metal (WM) and the heat‐affected zone (HAZ) of magnesium AZ31 (MgAl3) were carried out in order to derive the unknown substitute structural length. Results of fatigue tests with geometrically similar welded joints with full and partial penetration were available. The comparison of the experimental and predicted substitute structural length using Genetic Algorithm Substitute Structural Length Estimation Model (GASLEM) shows that the developed models seem to be capable of predicting the SSL values. Fatigue strength values were also obtained using predicted SSL.
Microstructure‐oriented characterisation of the cyclic deformation behaviour of Ti‐6Al‐4V
Authors: Rojek N. , Smaga M. , Walther F. , Eifler D. 
Published: March 2008

AbstractIn this paper, the cyclic deformation behaviour of the titanium alloy Ti‐6Al‐4V is characterised in uniaxial stress‐ and total‐strain‐controlled load increase and constant amplitude tests at ambient temperature by means of mechanical stress‐strain hysteresis and temperature measurements. The measured physical values obviously show a pronounced interrelation with the underlying fatigue processes and represent the actual fatigue state. In selected experiments the influence of elevated temperatures on the cyclic deformation behaviour was investigated. Using the plastic strain amplitude and the change of the specimen temperature with the physically based lifetime calculation “PHYBAL” an excellent accordance with experimentally determined lifetimes could be realised. Microstructural changes were evaluated by transmission electron microscopy in defined fatigue states, additionally, the fracture surface was analysed by scanning electron microscopy.
Über adiabatic shearbands und die Entstehung der „Steilen Weißen Bänder”︁ in Wälzlagern
Authors: Schlicht H. 
Published: March 2008

AbstractBei der Überrollung von Wälzelementen entstehen nach überelastischen Beanspruchungen unter der Laufbahnoberfläche strukturelle Veränderungen. Mikro‐ und makroplastische Verformungen des Gefüges infolge der dreiachsigen Beanspruchung begleiten den Wälzermüdungsprozess vom ersten Lastwechsel an. Sie bestimmen die Lebensdauer des Wälzelements. Man beobachtet neben den plastischen Verformungen des Gefüges des Weiteren die sog. „butterflies”︁ und die sog. flachen und steilen „Weißen Bänder”︁. Diese Gefüge sind nicht anätzbar. Die weißen Bänder entstehen bei Kugellagern erst nach einer größeren Anzahl von Überrollungen und liegen im Umfangsschnitt unter ≈ 30 ° bzw. ≈ 80 ° zur Kontaktfläche. Die butterflies und die weißen Bänder entstehen offenbar infolge einer zweiachsigen Werkstoffbeanspruchung. Ein Einfluss auf die Lebensdauer ist nicht erwiesen. Struktur und Entstehungsmechanismus sind strittig.Es gibt Gefügeerscheinungen, die den butterflies und den weißen Bändern ähnlich sind, die sog. adiabatic shearbands. Diese entstehen nach einer lokalen Makro‐Scherung des Gefüges, ausgelöst durch eine einmalige, extrem kurzzeitige Druck‐Scher‐Beanspruchung. Blitztemperaturen nahe dem Schmelzpunkt verursachen im Scherbereich bei martensitisch gehärteten Werkstoffen die Bildung von Neuhärtungszonen; auch diese Gefüge sind nicht anätzbar.Der vorliegende Aufsatz beschäftigt sich mit der Frage, ob während des stetig und langzeitig ablaufenden Prozesses der plastischen Verformungen eine Beanspruchungskonstellation entsteht, die die adiabatische Bildung von butterflies und von weißen Bändern ermöglicht. Berücksichtigt man jüngste Erkenntnisse zur Wälzermüdung sowie zur Werkstoffbeanspruchung durch eine EHD‐Strömung, dann darf man zumindest die „Steilen Weißen Bänder”︁ als adiabatic shearbands ansehen.
Rheologisches Verhalten hochgefüllter Kunststoffe. Einfluss der Füllstoffe
Authors: Markov A.V. 
Published: March 2008

AbstractIm Rahmen dieser Arbeit wurde das Fliessverhalten gefüllter thermoplastischer Polymere untersucht. Es wurde gezeigt, dass die rheologischen Eigenschaften hochgefüllter Kunststoffe im Allgemeinen vom Fließverhalten des Matrixpolymers, den Eigenschaften und der Struktur der dispersen Phase und Wechselwirkungen zwischen Polymer und Füllstoff sowie zwischen den einzelnen Füllstoffpartikeln abhängig sind. In der Arbeit wurde das theoretische Verhältnis zwischen der Viskosität von gefüllten und ungefüllten Polymeren als Funktion des Füllstoffgehalts und der Wechselwirkungen zwischen den Komponenten vorgeschlagen. Auf Basis des entwickelten Modells kann man die stochastische Struktur des gefüllten Materials und die nicht linearen viskosen Eigenschaften der Kunststoffschmelze berücksichtigen.
The influence of the electroplating parameters on the conditions of deposited nickel‐iron coatings
Authors: Hoffmann J. E. , Bedner K. , Clemens H. , Degen R. , Dhum C. , Giro F. , Kirsch U. , Schmitt M. , Saumer M. 
Published: March 2008

AbstractSeveral specific electroplating parameters are varied to develop a manufacturing process for nickel‐iron coatings with low residual stresses and favourable structures and hardness values. Here, the produced coating conditions on the surface are characterised according to alloy compositions, microstructures, residual stresses, texture and microhardness as well as the elastic indentation modulus. The manufacture of the coatings was carried out in a laboratory electroplating plant. The process parameters are: electroplating in electrolytic baths with and without saccharin as an additive, with different iron content as well as with various current parameters. The results show significant influences of saccharin, as a bath additive, and of the pulse frequency during the reverse current pulse procedure on the coating conditions. Supplementary investigations are scheduled for determining the distributions of the conditions through the coating thickness. Similarly, micromechanical tests are planned. Process parameters with optimal conditions can then be selected from the determined process‐condition property relation. This is to subsequently serve as the basis for improving the manufacture of micro gear‐wheels. The micro gear‐wheels are produced by electroforming using the direct LIGA process.
Examining item bias in the anxiety subscale of the Hospital Anxiety and Depression Scale in patients with chronic obstructive pulmonary disease
Authors: Tang Wai‐Kwong , Wong Eric , Chiu Helen F. K. , Lum C. M. , Ungvari Gabor S. 
Published: March 2008

AbstractThe Hospital Anxiety and Depression Scale (HADS) is a widely used screening instrument for depression and anxiety in medically compromised patients. The purpose of this study was to examine the differential item functioning (DIF) of the anxiety subscale of the HADA (HADS‐A). A research assistant administered the HADS‐A to 166 Chinese patients with chronic obstructive pulmonary disease (COPD) who were consecutively admitted to a rehabilitation hospital. Although the HADS‐A was overall uni‐dimensional, there were one mute item and two items with borderline misfit. Only one item had a DIF for arterial oxygen saturation. No item had DIF for other indicators of the severity of COPD. In conclusion, this study found that for one item the HADS‐A has significant item bias for the severity of disease in patients with COPD. Copyright © 2008 John Wiley & Sons, Ltd.
An energy‐efficient node‐scheduling scheme for wireless sensor networks based on minimum dominating sets
Authors: Pazand Babak , Datta Amitava 
Published: March 2008

AbstractOne of the major requirements for new wireless sensor networks is to extend the lifetime of the network. Node‐scheduling techniques have been used extensively for this purpose. Some existing approaches rely mainly on location information through global positioning system (GPS) devices for designing efficient scheduling strategies. However, integration of GPS devices with sensor nodes is expensive and increases the cost of deployment dramatically. In this paper we present a location‐free solution for node scheduling. Our scheme is based on a graph theoretical approach usingminimum dominating sets. We propose a heuristic to extract a collection of dominating sets. Each set consists of a group of working nodes which ensures a high level of network coverage. At each round, one set is responsible for covering the sensor field while the nodes in other sets are in sleep mode. We evaluate our solution through simulations and discuss our future research directions. Copyright © 2008 John Wiley & Sons, Ltd.
Analytical integration of singular kernels in symmetric boundary element analysis of Kirchhoff plates
Authors: Mazza M. , Leonetti L. , Aristodemo M. 
Published: March 2008

AbstractAn analytical integration method for evaluating the singular integrals arising in the construction of symmetric boundary element models is proposed, referring to the analysis of Kirchhoff plates. Kernels involved in the symmetric boundary formulation of Kirchhoff plates exhibit singularities up to O(1/r4). The proposed technique temporarily deactivates the singularities by using a limit approach and carries out the integration on contiguous boundary elements in order to smooth the singularities of the kernels through sufficiently continuous shape functions. The paper contains a brief presentation of the boundary integral formulation of the Kirchhoff plate, with the explicit expressions of the fundamental solutions involved and the derivation of the symmetric boundary element model. A detailed description of the proposed integration technique is presented, which discusses the main steps of the analytical procedure and provides the final results. The technique is illustrated through the discussion of a series of relevant cases, including high singularities and referring to both collinear and corner supports. Copyright © 2008 John Wiley & Sons, Ltd.
Fast Bayesian approach for parameter estimation
Authors: Jin Bangti 
Published: March 2008

AbstractThis paper presents two techniques, i.e. the proper orthogonal decomposition (POD) and the stochastic collocation method (SCM), for constructing surrogate models to accelerate the Bayesian inference approach for parameter estimation problems associated with partial differential equations. POD is a model reduction technique that derives reduced‐order models using an optimal problem‐adapted basis to effect significant reduction of the problem size and hence computational cost. SCM is an uncertainty propagation technique that approximates the parameterized solution and reduces further forward solves to function evaluations. The utility of the techniques is assessed on the non‐linear inverse problem of probabilistically calibrating scalar Robin coefficients from boundary measurements arising in the quenching process and non‐destructive evaluation. A hierarchical Bayesian model that handles flexibly the regularization parameter and the noise level is employed, and the posterior state space is explored by the Markov chain Monte Carlo. The numerical results indicate that significant computational gains can be realized without sacrificing the accuracy. Copyright © 2008 John Wiley & Sons, Ltd.
Non‐linear coupled multi‐field mechanics and finite element for active multi‐stable thermal piezoelectric shells
Authors: Varelis Dimitris , Saravanos Dimitris A. 
Published: March 2008

AbstractIn this paper, a coupled multi‐field mechanics framework is presented for analyzing the non‐linear response of shallow doubly curved adaptive laminated piezoelectric shells undergoing large displacements and rotations in thermal environments. The mechanics incorporate coupling between mechanical, electric and thermal fields and encompass geometric non‐linearity effects due to large displacements and rotations. The governing equations are formulated explicitly in orthogonal curvilinear coordinates and are combined with the kinematic assumptions of a mixed‐field shear‐layerwise shell laminate theory. A finite element methodology and an eight‐node coupled non‐linear shell element are developed. The discrete coupled non‐linear equations of motion are linearized and solved, using an extended cylindrical arc‐length method together with a Newton–Raphson technique, to enable robust numerical predictions of non‐linear active shells transitioning between multiple stable equilibrium paths. Validation and evaluation cases on laminated cylindrical strips and cylindrical panels demonstrate the accuracy of the method and its robust capability to predict non‐linear response under thermal and piezoelectric actuator loads. Moreover, the results illustrate the capability of the method to model piezoelectric shells undergoing large shape changes by actively jumping between stable equilibrium states and quantify the strong relationship between shell curvature, applied electric potential, applied temperature differential and induced shape change. Copyright © 2008 John Wiley & Sons, Ltd.
High‐frequency response analysis via algebraic substructuring
Authors: Ko Jin Hwan , Bai Zhaojun 
Published: March 2008

AbstractHigh‐frequency response analysis (Hi‐FRA) of large‐scale dynamical systems is critical to predict the resonant behavior of modern micro‐devices and systems operated over MHz or GHz frequency range. Algebraic substructuring (AS) is a powerful technique to extract a large number of natural frequencies. In this work, we extend the AS technique for FRA between two specified cutoff frequencies ωmin and ωmax. The technique is referred to as ASFRA. ASFRA can be efficiently applied to Hi‐FRA, as demonstrated by two examples of microelectromechanical sensors operated at 1–2 and 200–250 MHz ranges. To some extent ASFRA generalizes the underlying numerical algorithm and functionality of commercially viable automated multi‐level substructuring (AMLS) technique. AMLS is designed for FRA up to a specific frequency ωmax, starting from the lowest, and is inefficient for Hi‐FRA. Copyright © 2008 John Wiley & Sons, Ltd.
Nodal velocity derivatives of finite element solutions: The FiND method for incompressible Navier–Stokes equations
Authors: Ilinca F. , Pelletier D. 
Published: March 2008

AbstractThis paper presents the development and application of the finite node displacement (FiND) method to the incompressible Navier–Stokes equations. The method computes high‐accuracy nodal derivatives of the finite element solutions. The approach imposes a small displacement to individual mesh nodes and solves a very small problem on the patch of elements surrounding the node. The only unknown is the value of the solution (u, p) at the displaced node. A finite difference between the original and the perturbed values provides the directional derivative. Verification by grid refinement studies is shown for two‐dimensional problems possessing a closed‐form solution: a Poiseuille flow and a flow mimicking a boundary layer. For internal nodes, the method yields accuracy slightly superior to that of the superconvergent patch recovery (SPR) technique of Zienkiewicz and Zhu (ZZ). We also present a variant of the method to treat boundary nodes. The local discretization is enriched by inserting an additional mesh point very close to the boundary node of interest. Computations show that the resulting nodal derivatives are much more accurate than those obtained by the ZZ SPR technique. Copyright © 2008 John Wiley & Sons, Ltd.
An analysis of monotonicity conditions in the mixed hybrid finite element method on unstructured triangulations
Authors: Mazzia Annamaria 
Published: March 2008

AbstractIn this paper we consider the mixed hybrid finite element method on unstructured triangular grids and evaluate its monotonicity properties by using a non standard set of basis functions for the velocity approximation space.The mixed hybrid discretization of the steady‐state diffusion equation produces a system matrix that depends only on the inner product of the outward normals to the edges of the triangulation and not on the choice of the velocity space basis. This property is used to study the characteristics of the system matrix. It is well known that this matrix is of type M if the angles of the triangulation are not bigger than π/2. An M‐matrix has a nonnegative inverse, i.e. all the elements are nonnegative. This implies the existence of a discrete maximum principle and thus monotonicity of the discretization. We show that, when the triangulation is of Delaunay type and satisfies the property that no circumcenters of boundary elements with Dirichlet conditions lie outside the domain, the inverse of the final matrix is always positive, even in the presence of obtuse angles. Copyright © 2008 John Wiley & Sons, Ltd.