bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vinyl Monomers, Polymers and Supramolecular Assemblies from Aminocaprolactam
Authors: Tarkin‐Tas Eylem , Tas Huseyin , Mathias Lon J. 
Published: April 2012

Abstractα‐Aminocaprolactam is a “green” monomer in two ways: it is a fermentation product from sugars, and its derivatives are naturally biocompatible and biodegradable. In this overview, the synthesis of a variety of α‐amino‐ε‐caprolactam (ACL) derivatives through reaction with acid chlorides, anhydrides, and alkyl halides is described first. The product vinyl and divinyl derivatives were then polymerized using free radical initiators, and the obtained polymers characterized by solution NMR spectroscopy, differential scanning calorimetry, and thermal gravimetric analysis. The homopolymers of these monomers displayed surprisingly high glass transition temperature (Tg) values plus unexpectedly large sub‐Tg transitions that are believed due to relaxation of hydrogen bonding of pendent ACL units that allows group rotation. Finally, bis‐ and tetra‐caprolactams of various diacid chlorides and diisocyantes were synthesized and shown to form self‐assembled polymers and networks with excellent physical and thermal properties.
Synthesis and Characterization of Allylmelamine Based Polymers
Authors: Gabriel Herbert , List Manuela , Schwarzinger Clemens 
Published: April 2012

AbstractNovel linear polymers on the basis of allyl functionalized melamine derivatives, without using formaldehyde as cross‐linking agent, were created. Allylpentamethylmelamine and allyltetramethylmelamine were polymerized by free radical mechanism in substance. Allylpentamethyl‐melamine was also copolymerized with styrene by anionic polymerization. The new polymers offer a broad range of industrial application for melamine derivatives, not only in homopolymerization but also in the copolymerization with other monomers. For molar mass determination the polymer has been separated in different fractions by SEC and characterized by SEC and MALDI‐ToF mass spectrometry.
Adsorption of Methyl Orange, Pb2+ and Cd2+ from Aqueous Solution by Composites of Lignocellulose‐Montmorillonite Modified with Methacryloxypropyl Trimethoxysilane
Authors: Bunhu Tavengwa , Tichagwa Lilian 
Published: April 2012

AbstractA composite material based on lignocellulose and montmorillonite clay (MPSgLig‐NaMMT) was prepared and evaluated as an adsorbent for the removal of pollutants (dyes and heavy metals) from aqueous solution. The lignocellulose‐montmorillonite composite was prepared by in situ intercalative polymerisation, using methacryloxypropyl trimethoxysilane (MPS) as a coupling agent. The composite material was characterised by FTIR, TGA and SAXS. The lignocellulose‐montmorillonite composite was assessed as an adsorbent for methyl orange dye from aqueous solution. The composite material showed enhanced adsorption of methyl orange (MetO) compared with the NaMMT or lignocellulose separately. Competitive adsorption studies were carried out from binary mixtures of MetO with Cd2+ or Pb2+ in aqueous solution. The adsorption process of MetO onto the composite material was found to follow the Freundlich adsorption model. The adsorption of methyl orange from binary mixtures, were found to follow both the pseudo first‐order and pseudo second‐order models.
The Combination of Liquid Chromatography and Mass Spectrometry Techniques for the Characterization of Aliphatic Polyesters
Authors: Pretorius Nadine O. , Simpson Jaylin M. , McLeary James B. , Pasch Harald 
Published: April 2012

AbstractAliphatic polyesters are industrially implemented in high performance coatings, paints and varnishes, however it is typically difficult to correlate the resulting properties with the synthesis parameters as these polymers vary in reactivity and application properties. Due to the stepwise polymerization mechanism, it is often assumed that copolyester synthesis by direct polyesterification will lead to randomized products. The formation of cyclic products by transesterification allows even further randomization, enabling a highly complex system. The different methods of polymer chromatography in combination with sophisticated spectroscopic techniques are useful tools for enabling the full description of the molecular heterogeneity of these complex polyesters. Through the use of SEC, HPLC, MALDI‐TOF and ESI‐MS information was obtained on the extent of heterogeneity found during the synthesis of model polyesters based on maleic anhydride and phthalic anhydride with propylene glycol which serve as building blocks for the more complex industrial variety.
Viscosity, Rheological and Morphological Properties of Sulfonated Poly(ether ether ketone): PEM Fuel Cell Membrane Material
Authors: Sultan Abdullah S. , Al‐Ahmed Amir , Zaidi S. M. Javaid 
Published: April 2012

AbstractViscosity and rheological properties of sulfonated poly(ether ether ketone) (SPEEK) have been investigated. Viscometric data were correlated by different models for polyelectrolytes. Results of viscosity for SPEEK show the characteristic properties of polyelectrolytes. Effects of parameters such as degree of sulfonation (DS), temperature, and type of solvents were investigated. Dynamic and steady shear measurements were carried out in an ARES rheometer at room temperature. It was observed that the degree of sulfonation (DS) and the solution concentration have an enormous effect on the rheological properties such as storage modulus, G′ and dynamic viscosity (η′). Membranes (thickness, ∼100 µm) were prepared by solution casting method using three different solvents, namely, N,N‐Dimethylacetamide, Dimethylsulfoxide and N,N‐Dimethylformamide. Scanning electron microscopy (SEM) and DSC studies were also carried out to study the morphological properties of these membranes. The degree of sulfonation (DS) of SPEEK, the solvent type and the temperature were found to have pronounced effects on the viscosity and rheological properties. SPEEK showed better properties in DMAc and results of SEM and DSC also confirm that membranes prepared in DMAc showed uniform morphology and higher thermal stability. These viscosity and rheological parameters give insight about the interaction of SPEEK with DMAc and these results can be helpful for membrane fabrication.
Electrochemical corrosion studies and pitting corrosion sensitivity of a self‐pierce rivet joint of carbon fibre reinforced polymer (CFRP) – laminate and EN AW‐6060‐T6
Authors: Mandel M. , Krüger L. 
Published: April 2012

AbstractThe galvanic corrosion of a self‐pierce rivet joint of EN AW‐6060‐T6 and a carbon fibre reinforced plastic (CFRP) laminate joint by an Almac®‐coated self‐pierce steel rivet was electrochemically investigated in a 5 wt.% sodium chloride solution. Furthermore, the joint was examined in a climate chamber according to the VDA 621‐415 (VDA = Verein Deutscher Automobilhersteller) standard test and microscopically observed. Electrochemical tests of the single components already reveal that a rivet joint of the materials can lead to pitting corrosion on the aluminium alloy surface and enforces the dissolution of the anti‐corrosion layer Almac® of the rivet. This predicted corrosion behaviour was confirmed by the microscopic observations after the exposure of the joint in the climate chamber.
Fabrication of carbon fibre reinforced, aluminium matrix composite by potassium iodide (KI) – potassium hexafluoro‐titanate (K2TiF6) flux
Authors: Juhasz K. L. , Baumli P. , Kaptay G. 
Published: April 2012

AbstractCarbon fibres (CF) reinforced aluminium (Al) matrix composite material was fabricated using a special flux of potassium iodide (KI) with 10 weight% of potassium hexafluoro‐titanate (K2TiF6) at 820°C under protective argon atmosphere. The fabrication was performed with no extra pressure or mixing applied. Liquid Al spontaneously penetrated the space between the carbon fibres (or single fibres were spontaneously transferred from molten salt into liquid Al), due to the perfect wettability between these phases and the corresponding action of the interfacial capillary force. Perfect wettability is ensured by the formation of a thin metallic titanium carbide layer at the fibres/aluminium interface. Metallic titanium appears in liquid Al due to its exchange reaction with the K2TiF6 content of the molten salt.
Characterisation of the bonding zone of co‐extruded aluminium‐titanium‐compounds
Authors: Striewe B. , Grittner N. , von Hehl A. , Hunkel M. , Stelling O. , Schimanski K. , Schaper M. , Zoch H.‐W. , Bach F.‐W. 
Published: April 2012

AbstractThe combination of different metallic materials enables the design of lightweight structures with tailor‐made properties at global as well as local scale and offers great potential for advanced solutions especially for the aircraft and automobile sector. However, after conventional fusion joining, e. g. after laser beam welding, heat affected zones, porosity or grain growth may occur and impair the local properties. In contrast, by solid‐state joining techniques like co‐extrusion these disadvantages can be avoided. Therefore co‐extrusion exhibits an attractive solution for long products combining aluminium and titanium based alloys. Current investigations have been focused on the co‐extrusion of aluminium and titanium, where titanium is the reinforcing element that is inserted in aluminium profiles. In the context of a current research project the formation of the intermetallic layer and the mechanical properties were investigated in detail. In addition to that the influence on the intermetallic layer and the mechanical properties on heat treatment were investigated. The mechanical properties were determined by tensile tests. The intermetallic layers were analysed with light optical microscope, scanning electron microscope and electron probe micro analysis. During the co‐extruding an intermetallic layer with a thickness of 1 μm to 3 μm arises in the bonding zone between aluminium and titanium partner. Alloying elements from the aluminium alloy enrich in this layer. A subsequent heat treatment leads to an age hardening of the aluminium, however, it does not affect the layer thickness. The tensile tests specimen show different failure locations. The heat treatment leads to increased tensile strength values, but also to a decreased yield strength level.
Highly heat conductive open‐porous aluminium fibre based parts for advanced heat transfer applications
Authors: Andersen O. , Meinert J. , Studnitzky T. , Stephani G. , Kieback B. 
Published: April 2012

AbstractDue to their oxygen affinity, aluminium alloys are difficult‐to‐sinter materials. Either mechanical destruction or the action of a liquid phase can be used to break oxide layers and thus achieve the desired diffusion bonds between the individual particles. In the present work, a liquid phase sintering approach is used in conjunction with high‐purity particulates and controlled processing conditions in order to obtain high‐purity, high‐porosity (up to 90 %) parts with an exclusively open porosity. Appropriate sinter conditions were determined with the help of thermodynamic calculations using the PANDAT software package. Bonding of the sintered fibre structures to tubes, sheets and other massive structures may be achieved by co‐sintering or brazing. The resulting metallic contacts allow for excellent heat transfer between the fibre structure and heat‐carrying fluids. These advantageous properties may be exploited in applications such as adsorption cooling devices or very fast phase‐change material (PCM) heat‐storage devices. The present study reports on the manufacturing of such PCM‐aluminium fibre compounds and their performance measured on a PCM storage demonstrator run in a laboratory environment.
Development of a mixer to fabricate particle stabilized aluminium matrix emulsions and monotectic alloys
Authors: Budai I. 
Published: April 2012

AbstractAluminum matrix monotectic alloys with a homogeneous distribution of the second phase droplets can be obtained in large ingots, if the droplets are stabilized by solid particles of optimized wettability at the interface of the two, immiscible liquid metals. In this paper, Al‐matrix emulsions with Cd‐rich droplets, stabilized by Al4Sr intermetallic particles are prepared, based on our previous paper. The new information in the present paper is the development of a new type of a mixer, allowing increased rotational speed, and hence, more efficient emulsification without the danger of mixing the liquid metals out of the crucible. As the comparative experiments proved, the ratio of emulsified Cd‐rich liquid was found to increase considerably when the old mixer was replaced by the new one. Particularly, there is no 1‐phase Cd‐rich sedimentation found at the bottom of the crucible when the mixer of the new design is applied.
Thermal Polymerization of Styrene, Part 2 – (Mini)emulsion Polymerization
Authors: Katzer Johannes , Pauer Werner , Moritz Hans‐Ulrich , Wulkow Michael 
Published: April 2012

AbstractAn experimental and theoretical study on the thermal (spontaneous) polymerization of styrene in compartmentalized systems is presented. Experimental data on thermally polymerized miniemulsions varying temperature and droplet size is provided. This data is used to test a new model approach to describe the thermal polymerization process of a disperse phase. The mathematical model is based on a chemical master equation balancing radical species that are capable of desorption (monomeric radicals) and ones that cannot leave a particle. Reasonable agreement between theory and experiment for the data provided here and for literature data can be achieved. Part 1 of this series is a review on the thermal bulk polymerization of styrene.magnified image
Effect of Hydrogen and External Donor on Propylene Polymerization Kinetics with a 4th‐Generation Ziegler‐Natta Catalyst
Authors: Alshaiban Ahmad , Soares João B. P. 
Published: April 2012

AbstractApparent kinetic rate constants and activation energies for catalyst activation, deactivation, and propylene propagation with a 4th‐generation Ziegler‐Natta catalyst are estimated. The rate of polymerization in the presence of donor and hydrogen is higher than in their absence. Catalyst activation and propagation rate constants increase with the addition of hydrogen, likely because hydrogen frees 2–1‐terminated dormant sites. The deactivation term was the highest without electron donor, presumably because the nonspecific sites deactivate faster than the specific sites. Apparent activation energies for catalyst activation, deactivation, and propagation are not significantly influenced by the presence of hydrogen or external donor, indicating that they do not affect these mechanisms substantially. magnified image
Construction of tetrahedral meshes of degree two
Authors: George P.L. , Borouchaki H. 
Published: April 2012

SUMMARYThere is a need for finite elements of degree two or more to solve various PDE problems. This paper discusses a method to construct such meshes in the case of tetrahedral element of degree two. The first section of this paper returns to Bézier curves, Bézier triangles and then Bézier tetrahedra of degree two. The way in which a Bézier tetrahedron and a P2 finite element tetrahedron are related is introduced. A validity condition is then exhibited. Extension to arbitrary degree and dimension is given. A construction method is then proposed and demonstrated by means of various concrete application examples. Copyright © 2012 John Wiley & Sons, Ltd.
Modified meshless local Petrov–Galerkin formulations for elastodynamics
Authors: Soares D. , Sladek V. , Sladek J. 
Published: April 2012

SUMMARYThis paper is concerned with the extension to the elastodynamic problems of the idea of analytical integrations in meshless local weak formulations. In this context, Taylor series expansions of the incognita fields are considered, and the related integrals of the meshless formulations are solved analytically, rendering a so‐called modified methodology. The moving least squares approximation is employed for the spatial variation of the displacement fields, and two variants of the meshless local Petrov–Galerkin (MLPG) formulation are discussed here, which are based on the use of Heaviside or Gaussian weight test functions. Once the spatial discretization is considered, the semi‐discretized ordinary differential equations for nodal unknowns that arise are treated in the time‐domain by the Houbolt's method. Considering the modified meshless methodology, it was found that the standard derivatives of the shape functions must also be modified to achieve numerically stable procedures, taking into account dynamic analyses. Thus, an efficient and easy‐to‐implement technique is developed to properly compute the shape function derivatives. As described in the paper, the proposed modified MLPG formulations are more effective than standard MLPG formulations, especially taking into account well refined large scale problems, providing much better computational efficiency, good accuracy and more robust convergence. Copyright © 2012 John Wiley & Sons, Ltd.
Geometrical design of thermoelectric generators based on topology optimization
Authors: Takezawa A. , Kitamura M. 
Published: April 2012

SUMMARYThis paper discusses an application of the topology optimization method for the design of thermoelectric generators. The proposed methodology provides the optimized geometry in accordance with various arbitrary conditions such as the types of materials, the volume of materials, and the temperature and shape of the installation position. By considering the coupled equations of state for the thermoelectric problem, we introduce an analytical model subject to these equations, which mimics the closed circuit composed of thermoelectric materials, electrodes, and a resistor. The total electric power applied to the resistor and the conversion efficiency are formulated as objective functions to be optimized. The proposed optimization method for thermoelectric generators is implemented as a geometrical optimization method using the solid isotropic material with penalization method used in topology optimizations. Simple relationships are formulated between the density function of the solid isotropic material with penalization method and the physical properties of the thermoelectric material. A sensitivity analysis for the objective functions is formulated with respect to the density function and the adjoint equations required for calculating it. Depending on the sensitivity, the density function is updated using the method of moving asymptotes. Finally, numerical examples are provided to demonstrate the validity of the proposed method. Copyright © 2012 John Wiley & Sons, Ltd.
Immersed smoothed finite element method for two dimensional fluid–structure interaction problems
Authors: Zhang Zhi‐Qian , Liu G. R. , Khoo Boo Cheong 
Published: April 2012

SUMMARYA novel method called immersed smoothed FEM using three‐node triangular element is proposed for two‐dimensional fluid–structure interaction (FSI) problems with largely deformable nonlinear solids placed within incompressible viscous fluid. The fluid flows are solved using the semi‐implicit characteristic‐based split method. Smoothed FEMs are employed to calculate the transient responses of solids based on explicit time integration. The fictitious fluid with two assumptions is introduced to achieve the continuous form of the FSI conditions. The discrete formulations to calculate the FSI forces are obtained in terms of the characteristic‐based split scheme, and the algorithm based on a set of fictitious fluid mesh is proposed for evaluating the FSI force exerted on the solid. The accuracy, stability, and convergence properties of immersed smoothed FEM are verified by numerical examples. Investigations on the mesh size ratio indicate that the stability is fairly independent of the wide range of the mesh size ratio. No additional volume correction is required to satisfy the incompressible constraints. Copyright © 2012 John Wiley & Sons, Ltd.
A note on upper bound formulations in limit analysis
Authors: Muñoz J.J. , Huerta A. , Bonet J. , Peraire J. 
Published: April 2012

SUMMARYIn this paper, we study some recent formulations for the computation of upper bounds in limit analysis. We show that a previous formulation presented by the authors does not guarantee the strictness of the upper bound, nor does it provide a velocity field that satisfies the normality rule everywhere. We show that these deficiencies are related to the quadrature employed for the evaluation of the dissipation power. We derive a formulation that furnishes a strict upper bound of the load factor, which in fact coincides with a formulation reported in the literature. From the analysis of these formulations, we propose a post‐process, which consists in computing exactly the dissipation power for the optimum upper bound velocity field. This post‐process may further reduce the strict upper bound of the load factor in particular situations. Finally, we also determine the quadratures that must be used in the elemental and edge gap contributions, so that they are always positive and their addition equals the global bound gap. Copyright © 2012 John Wiley & Sons, Ltd.
Risk factors for pressure ulcer development in critically Ill patients: A conceptual model to guide research
Authors: Benoit Richard , Mion Lorraine 
Published: April 2012

AbstractThis paper presents a proposed conceptual model to guide research on pressure ulcer risk in critically ill patients, who are at high risk for pressure ulcer development. However, no conceptual model exists that guides risk assessment in this population. Results from a review of prospective studies were evaluated for design quality and level of statistical reporting. Multivariate findings from studies having high or medium design quality by the National Institute of Health and Clinical Excellence standards were conceptually grouped. The conceptual groupings were integrated into Braden and Bergstrom's (Braden and Bergstrom [1987] Rehabilitation Nursing, 12, 8–12, 16) conceptual model, retaining their original constructs and augmenting their concept of intrinsic factors for tissue tolerance. The model could enhance consistency in research on pressure ulcer risk factors. © 2012 Wiley Periodicals, Inc. Res Nurs Health 35:340–362, 2012
Reliability and validity of the 4‐item perceived stress scale among pregnant women: Results from the OTIS antidepressants study
Authors: Karam Fatiha , Bérard Anick , Sheehy Odile , Huneau Marie‐Claude , Briggs Gerald , Chambers Christina , Einarson Adrienne , Johnson Diana , Kao Kelly , Koren Gideon , Martin Brigitte , Polifka Janine E. , Riordan Sara H. , Roth Mark , Lavigne Sharon Voyer , Wolfe Lori ,   the OTIS Research Committee
Published: April 2012

AbstractWe aimed to estimate the reliability of the 4‐item Perceived Stress Scale (PSS) and its validity in predicting maternal depression and quality of life (QoL). Data regarding stress, depression and QoL were collected during pregnancy among a sub‐sample from the Organization of Teratology Information Specialists Antidepressants in Pregnancy Cohort. The 4‐item PSS demonstrated acceptable internal consistency (Cronbach's alpha coefficient = .79), alternate forms stability reliability with the 10‐item PSS (Pearson correlation coefficient r = .63; p < .001), convergent validity with the Edinburgh Postnatal Depression Scale (r = .67; p < .001), and concurrent validity with the mental health component of the Short‐Form‐12 (r = −.62; p < .001) as a measure of QoL. The 4‐item PSS is a valid and useful tool for assessing maternal stress during pregnancy. © 2012 Wiley Periodicals, Inc. Res Nurs Health 35:363–375, 2012