bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of accelerated ultraviolet and thermal exposure on nanoscale mechanical properties of nylon fibers
Authors: Wanasekara Nandula D. , Chalivendra Vijaya , Calvert Paul 
Published: July 2012

AbstractNanoindentation using atomic force microscopy was used to examine the mechanical properties of fibers at nanoscale. The effect of accelerated aging of nylon fibers under ultraviolet (UV) and thermal‐oxidative conditions on mechanical property gradients across the fiber cross‐section was investigated. It was identified that UV degradation produces bulk degradation up to 48 h of exposure and later surface degradation predominates with lower values of Young's modulus at surface compared to center. Wide angle X‐ray scattering shows a decrease of crystallinity with UV exposure. Unlike UV degradation, the thermal degradation was predominant at the surface for the first 3 weeks of exposure and was homogeneous after 4 weeks of exposure. These results support the idea that property gradients arise at high levels of degradation of nylon fiber as a result of UV and thermal‐oxidative conditions, and ultimately lead to embrittlement of the fibers. These results are in contrast to polypropylene, where the nanoindentation modulus increased with degradation and increased from the core to the surface after degradation. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
Theoretical modeling and experiments on the piezoelectric coefficient in cellular polymer films
Authors: Qaiss A. , Saidi H. , Fassi‐Fehri O. , Bousmina M. 
Published: July 2012

AbstractThis article presents an analytical model allowing the determination of the, d33, piezoelectric coefficient in cellular polymer films. The cellular film is identified to an equivalent effective layered structure made of alternating gas and solid layers that are electrically charged at their interfaces. The model expresses the d33 piezoelectric coefficient as a function of porosity, film thickness, free‐stress surface charge density, and the film modulus, which depends on frequency. The temperature is indirectly taken into account as it is involved in the parameters appearing in the final equation of the model. The obtained results showed that the piezoelectric activity of charged cellular polymer films decreases with the film thickness and increases with the film expansion and the surface charge density. The variation with the percentage of porosity shows a nonlinear trend, with an increase in the d33 piezoelectric coefficient with the void fraction, and then a decrease when such a percentage exceeds a thickness‐dependent critical value. Such quantitative description of the piezoelectric activity can help the design of cellular films with enhanced piezoelectric performances. The model predictions were also compared with some experimental results obtained on cellular piezoelectric films made of polypropylene filled with 10% of calcium carbonate microparticles. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Thermal, mechanical, and rheological properties of polylactide/poly(1,2‐propylene glycol adipate)
Authors: Zhang Huiliang , Fang Jianyong , Ge Huanhuan , Han Lijing , Wang Xuemei , Hao Yanping , Han Changyu , Dong Lisong 
Published: July 2012

AbstractPolylactide (PLA) was melt blended with poly(1,2‐propylene glycol adipate) (PPA) in a Thermo‐Haake mixer. Thermal, mechanical, and rheological properties of the blends were investigated by means of differential scanning calorimetry, dynamic mechanical analysis, tensile test, and small amplitude oscillatory shear rheometry. PPA lowered the glass transition temperature and increased the ability of PLA to cold crystallization. With the increase in PPA content (5–25 wt%), the blends showed decreased tensile strength and Young's modulus; however, impact strength and elongation‐at‐break along were dramatically increased due to the plastic deformation. Morphological results of PLA/PPA blends showed that PPA was good compatible with PLA. The plasticization effect of PPA was also manifested by the lowering of dynamic storage modulus and viscosity in the melt state of the blends compared with neat PLA. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Optical properties of europium (2,2′‐bipyridine‐N,N‐dioxide)2 (NO3)3 complex‐doped poly(methyl methacrylate)
Authors: Puthiyottil R. , Varghese S. , Gopalakrishnapanicker U. , Guthrie J.T. 
Published: July 2012

AbstractA complex of Eu(C10H8N2O2)2 (NO3)3, in different amounts [0.1, 0.3, 0.5, 1, 2 wt % with respect to the poly(methyl methacrylate) (PMMA)], was doped into PMMA matrix and the resulting formulation deposited by a solvent casting technique. Each complex‐doped PMMA composition was characterized by UV‐visible spectroscopy, fluorescence spectroscopy, fluorescence lifetime analysis, X‐ray diffraction and infrared spectroscopy. The structural properties of the composites are discussed on the basis of the results from these analyses. The chelate‐doped PMMA shows good luminescence properties with relatively long life times. It has been shown that the fluorescence life time of the complex‐doped PMMA composites varies with the amount of the chelate molecule in the composite. The results from the fluorescence analyses suggest that, in the doped systems, the microenvironment around the central metal ion changes with composition. The optical properties of the system vary with composition. The observations should be of value to the development of superior luminescent materials. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
In situ studies on the temperature‐related deformation behavior of isotactic polypropylene spherulites with uniaxial stretching: The effect of crystallization conditions
Authors: Huo Hong , Yao Xuemin , Zhang Yao , Li Jingqing , Shang Yingrui , Jiang Shichun 
Published: July 2012

AbstractThe deformation behavior of isotactic polypropylene (iPP) spherulites with uniaxial stretching was investigated at different drawing temperatures via in situ polarized optical microscope (POM) observation. The iPP spherulites were prepared by two procedures: cooled to the room temperature from melt and annealed at 135, 140, and 145°C for 3 h. It was found that the crystallization conditions dominate the crystalline morphology and even the tensile properties of iPP. For iPP which crystallized during cooling progress, the spherulites were imperfect and the boundaries of the spherulites were diffuse, displaying good toughness at various drawing temperatures. For iPP annealed at high temperatures displayed the brittle fracture‐modes and the crack happened between spherulites, which due to the large and perfective spherulites have thick lamellas and weak connection at interspherulitic boundary. The shape and size of the iPP spherulites formed at 140 and 145°C are affected with uniaxial stretching till to the fracture of the samples at different drawing temperatures. The spherulites obtained at 135°C are deformed along the drawing direction at 100°C but not affected at low drawing temperatures, indicating the toughness increased with the increase of the drawing temperatures. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Glycerol and esterified products of palmitic acid as a mixed plasticizer for thermoplastic tapioca starch
Authors: Ekabutr Pongpol , Lerdwijitjarud Wanchai , Sittattrakul Amnard 
Published: July 2012

AbstractIn this work, a mixture of glycerol (Gly) and derivatives of pentaerythritol or α,α′‐diglycerol is used as a plasticizer for preparing a thermoplastic starch (TPS). A coplasticizer containing both hydroxyl group and a long aliphatic chain was synthesized by esterification reaction between pentaerythritol or α,α′‐diglycerol and palmitoyl chloride in two different molar ratios, that is, 1:1 (PT1 and DG1), 1:2 (PT2 and DG2). The esterification products were characterized using Fourier transform infrared spectroscopy, 1H, and 13C nuclear magnetic resonance spectroscopy. The starch and the mixed plasticizer were blended in an internal mixer. The morphology and miscibility of the blends were investigated by scanning electron microscope. The mechanical properties, moisture adsorption, and retrogradation phenomenon of the TPS specimens were studied. The results indicated that the TPS specimen containing a mixed plasticizer in a weight ratio of 80% Gly: 20% PT1 showed the highest values of Young's modulus and tensile strength, because this mixed plasticizer system could form stronger hydrogen bonds with starch molecules. Moreover, thermoplastic starch with higher content of pentaerythritol or α,α′‐diglycerol derivatives as a coplasticizer showed lower moisture adsorption, because its long aliphatic chain (hydrophobic part) of pentaerythritol derivatives may prevent starch molecules to reform hydrogen bonding and to recrystallize. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Reinforcing effect of nanosilica on the properties of natural rubber/reclaimed ground rubber tire vulcanizates
Authors: De Debapriya , Panda Prabir Kr. , Roy Madhusudan , Bhunia Satyaban , Jaman Abu Ismail 
Published: July 2012

AbstractIn this investigation, incorporation of silica into natural rubber (NR)‐reclaim rubber (RR) blend system was carried out by sol‐gel technique at various sol‐gel reaction temperatures. The effect of RR on silica reinforcement, hitherto unexplored, was studied for different NR/RR blend systems. The degree of reinforcement of sol‐gel vulcanizates by equilibrium swelling method indicates that the reinforcing efficiency of the in situ generated silica by sol‐gel technique increases with increasing reclaim rubber content. The reinforcing efficiency, tensile properties and thermal stability of sol gel vulcanizates (SGV) prepared at 50°C become maxima as compared to SGV prepared at 30°C and 70°C. The amount of silica incorporated by sol‐gel technique was determined by thermogravimetry analysis. It indicates that the thermal stability increases with silica content. Attenuated total reflection study indicates that RR forms bond with silica particles due to the presence of active functional site on RR. Scanning electron microscopy studies further indicate the coherency and homogeneity in the silica filled NR/RR vulcanizates. The microwave diagnosis of different SGVs was also carried out and the frequency dependence of dielectric permittivity (E') and loss (E”) were measured. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Production of double‐walled nanoparticles containing meloxicam
Authors: Albuquerque Bruna , Costa Mariana Sousa , Peça Inês N. , Cardoso M. Margarida 
Published: July 2012

AbstractDouble‐walled nanospheres, containing meloxicam, were fabricated with poly‐(D,L‐lactide‐co‐glycolide) (PLGA) and poly(L‐lactide) (PLLA) using the solvent evaporation technique. This article discusses the effect of formulation variables [sonication power, sonication time, concentration of poly(vinyl alcohol), organic/aqueous volume ratio in the first emulsion] on the production of double‐walled nanospheres. The involved phase separation of these two polymers was investigated using differential scanning calorimetry. Double‐walled microspheres containing meloxicam were also produced to determine the composition of the shell and core polymer, based on different solubilities of polymers in ethyl acetate, and to examine the inner morphology and drug distribution using optical and fluorescence microscopy. The produced microparticles have shown a double‐walled structure with meloxicam solubilized in the PLGA‐rich phase. Therefore, adjusting the selected formulation variables and using a mass ratio of 1:1 PLLA/PLGA, double‐walled nanospheres where meloxicam is dispersed within the core can be produced. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Using NSGA‐II and TOPSIS Methods for Interior Ballistic Optimization Based on One‐Dimensional Two‐Phase Flow Model
Authors: Li Kejing , Zhang Xiaobing 
Published: July 2012

AbstractIn order to meet the design demands of new gun systems or new types of projectiles, the interior ballistic charge design seems especially important. In this paper, a one‐dimensional two‐phase flow model is presented. The model describes the transient combustion of granular propellants in a gun, and pressure waves are considered as an objective. This study adopts a hybrid method to solve the problem. In the first stage, the non‐dominated sorting genetic algorithm (NSGA‐II) with “a “filter” is employed to approximate a set of Pareto‐optimal solutions. In the subsequent stage, a multi‐attribute decision‐making (MADM) approach is adopted to rank these solutions from the best to the worst. The ranking of Pareto‐optimal solutions is based on the technique ordered preference by similarity to ideal solution (TOPSIS) method. In TOPSIS method each objective needs a corresponding weight coefficient, and a practical problem is introduced. Both the entropy method and linear analysis method are adopted to get two sets of weights for the objectives, respectively. The two pairs of final, best compromise solutions are compared for satisfying the designer’s aim. For the analysis of the results, a two‐phase flow interior ballistic model for design optimization is established, and the hybrid approach could get a reasonable design scenario.
Experimental results from a linear wave power generator connected to a resonance circuit
Authors: Ekergård Boel , Boström Cecilia , Hagnestål Anders , Waters Rafael , Leijon Mats 
Published: July 2012

AbstractThe output voltage from a direct‐driven permanent magnet linear generator installed in a wave power plant varies both in amplitude and frequency. Electrical conversion is therefore necessary before grid connection can be achieved. The aim of this paper is to present an electrical conversion system based on the electric resonance phenomena. As one of the first steps in the development, and to gain further knowledge and understanding of the proposed resonance circuit, experimental tests with a single‐phase permanent magnet linear generator connected to a resonance circuit were performed. The experimental results presented in this paper indicated that a successful resonance between the generator and external circuit was achieved. The research regarding the wave energy converters lies within The Lysekil Wave Power Project at Uppsala University and has been ongoing since 2002.This article is categorized under:

Wind Power > Science and Materials
Energy Infrastructure > Systems and Infrastructure
Forest bioenergy feedstock harvesting effects on water supply
Authors: Neary Daniel G. , Koestner Karen A. 
Published: July 2012

AbstractWater flowing from forested catchments, both unmanaged and managed, is highly valued in terms of both quantity and quality. Increasing energy production using wood feedstocks produces varying degrees of impacts and thereby raises concerns about environmental impacts on the highly valued water supply resources of forest ecosystems. The term water supply encompasses both key components of water quantity and water quality. Water quantity considers the amount of increases or decreases, timing, consistency, and relative magnitude of water yields. Plant nutrients (anions and cations), fertilizers, herbicides, ash additions, temperature, dissolved oxygen, pH, bacteria, and sediment comprise water quality. Within the life cycle of forest bioenergy, operational activities during stand establishment, midrotation silviculture, harvesting, product transportation, wood storage, energy production, and ash recycling create variable levels of impacts. Disturbance levels associated with bioenergy operations depend on their type, intensity, frequency, duration, timing, area of extent, and the level of best management practices (BMPs) employed for mitigating of soil disturbances. Feedstock growing, stand tending, harvesting, and wood transportation are considered nonpoint source disturbances since they occur over larger landscapes than energy production activities, which are usually localized at power plants. Water‐quantity effects of forest bioenergy production are normally associated with vegetation management and related soil disturbances. Water‐quality effects mostly occur as a result of soil disturbances during harvesting, the use of intra‐rotation silvicultural chemicals (ash, fertilizers, and herbicides), and inter‐rotation site preparation for forest regeneration. Using existing practices designed for environmental protection (BMPs), forest bioenergy programs are completely compatible with maintaining high‐quality water supplies in forested catchments.This article is categorized under:Bioenergy > Climate and EnvironmentEnergy Policy and Planning > Climate and EnvironmentEnergy and Development > Climate and Environment
The IVP for the dispersion generalized Benjamin–Ono equation in weighted Sobolev spaces
Authors: Fonseca Germán , Linares Felipe , Ponce Gustavo 
Published: July 2012

We study the initial value problem associated to the dispersion generalized Benjamin–Ono equation. Our aim is to establish persistence properties of the solution flow in weighted Sobolev spaces and to deduce from them some sharp unique continuation properties of solutions to this equation. In particular, we shall establish optimal decay rate for the solutions of this model.

Résumé
Nous étudions le problème de Cauchy associé à lʼéquation de Benjamin–Ono avec dispersion généralisée. Notre objectif est dʼétablir les propriétés de persistance de la solution dans des espaces de Sobolev avec poids et dʼen déduire quelques propriétés de prolongement unique pour ses solutions. En particulier, nous établirons un taux de décroissance optimal pour les solutions de ce modèle.
Control of the secondary cross-flow instability using localized suction
Authors: Friederich Tillmann , Kloker Markus J. 
Published: July 2012

AbstractTransition control by suction in a three-dimensional boundary-layer flow subject to cross-flow instability is investigated using direct numerical simulation. Whereas the classical application of (homogeneous) suction at the wall is aimed at modifying the quasi-two-dimensional base flow to weaken primary cross-flow instability, here the three-dimensional nonlinear disturbance state with large-amplitude steady cross-flow vortices (CFVs) is controlled. Strong, localized ‘pinpoint’ suction is shown to be suitable for altering the CFVs and the associated flow field such that secondary instability is weakened or even completely suppressed. Thus significant delay of transition to turbulence can be achieved.
Interaction of a laminar vortex ring with a thin permeable screen
Authors: Naaktgeboren Christian , Krueger Paul S. , Lage José L. 
Published: July 2012

AbstractThe canonical case of a vortex ring interacting with a solid surface orthogonal to its symmetry axis exhibits a variety of intricate behaviours, including stretching of the primary vortex ring and generation of secondary vorticity, which illustrate key features of vortex interactions with boundaries. Replacing the solid boundary with a permeable screen allows for new behaviour by relaxing the no-through-flow condition, and can provide a useful analogue for the interaction of large-scale vortices with permeable structures or closely spaced obstructions. The present investigation considers the interaction of experimentally generated vortex rings with a thin permeable screen. The vortex rings were generated using a piston-in-cylinder mechanism using piston stroke-to-diameter ratios ($L/ D$) of 1.0 and 3.0 (nominal) with jet Reynolds numbers ($R{e}_{j} $) of 3000 and 6000 (nominal). Planar laser-induced fluorescence and digital particle image velocimetry (DPIV) were used to study the interaction with wire-mesh screens having surface open-area ratios ($\phi $) in the range 0.44–0.79. Solid surfaces ($\phi = 0$) and free vortex rings ($\phi = 1$) were also included as special cases. Measurement of the vortex trajectories showed expansion of the vortex ring diameter as it approached the boundary and generation of secondary vorticity similar to the case of a solid boundary, but the primary vortex diameter then began to contract towards the symmetry axis as the flow permeated the screen and reorganized into a transmitted vortex downstream. The trajectories were highly dependent on $\phi $, with little change in the incident ring trajectory for $\phi = 0. 79$. Measurement of the hydrodynamic impulse and kinetic energy using DPIV showed that the change between the average upstream and downstream values of these quantities also depended primarily on $\phi $, with a slight decrease in the relative change as $L/ D$ and/or ${\mathit{Re}}_{j} $ were increased. The kinetic energy dissipation ($ \mrm{\Delta} E$) was much more sensitive to $\phi $, with a strongly nonlinear dependence, while the decrease in impulse ($ \mrm{\Delta} I$) was nearly linear in $\phi $. A simple model is proposed to relate $ \mrm{\Delta} E$ and $ \mrm{\Delta} I$ in terms of bulk flow parameters. The model incorporates the decrease in flow velocity during the interaction due to the drag force exerted by the screen on the flow.
Inertial dynamics of air bubbles crossing a horizontal fluid–fluid interface
Authors: Bonhomme Romain , Magnaudet Jacques , Duval Fabien , Piar Bruno 
Published: July 2012

AbstractThe dynamics of isolated air bubbles crossing the horizontal interface separating two Newtonian immiscible liquids initially at rest are studied both experimentally and computationally. High-speed video imaging is used to obtain a detailed evolution of the various interfaces involved in the system. The size of the bubbles and the viscosity contrast between the two liquids are varied by more than one and four orders of magnitude, respectively, making it possible to obtain bubble shapes ranging from spherical to toroidal. A variety of flow regimes is observed, including that of small bubbles remaining trapped at the fluid–fluid interface in a film-drainage configuration. In most cases, the bubble succeeds in crossing the interface without being stopped near its undisturbed position and, during a certain period of time, tows a significant column of lower fluid which sometimes exhibits a complex dynamics as it lengthens in the upper fluid. Direct numerical simulations of several selected experimental situations are performed with a code employing a volume-of-fluid type formulation of the incompressible Navier–Stokes equations. Comparisons between experimental and numerical results confirm the reliability of the computational approach in most situations but also points out the need for improvements to capture some subtle but important physical processes, most notably those related to film drainage. Influence of the physical parameters highlighted by experiments and computations, especially that of the density and viscosity contrasts between the two fluids and of the various interfacial tensions, is discussed and analysed in the light of simple models and available theories.