Identifying ‘associated-sleeping-beauties’ in ‘swan-groups’ based on small qualified datasets of physics and economics

Scientometrics - ‘Sleeping beauties’ refer to the papers that received no or scarce citation after appearance, but considerable citations several years later, which is a special...     

Sensitivity analysis and shape optimization based on FE–EFG coupled method

By use of 4-node isoparametric quadrangle interface element between finite element (FE) and meshless regions, a collocation approach is introduced to couple firstly FE and element-free Galerkin (EFG) method in this paper. By taking derivative of discreteness equilibrium equation at interface element with respect to design variable, a numerical method for discreteness-based shape design sensitivity analysis in interface element is obtained. The design sensitivity analysis (DSA) of coupled FE–EFG method is achieved by employing the DSA of nodal displacement at the interface element. The numerical method presented is testified by examples. It can be observed excellent agreement between the numerical results and the analytical solution. Finally the shape optimization of fillet is achieved by using coupled FE–EFG method. The result obtained show that imposing of the essential boundary condition is easy to implement, the computational time is reduced and the distortion of mesh is avoided.     

Structure–properties relationship in single polymer composites based on polyamide 6 prepared by in-mold anionic polymerization

Single polymer composites (SPCs) based on polyamide 6 (PA6) were prepared by in-mold activated anionic ring-opening polymerization (AAROP) of caprolactam in the presence of PA6 textile fibers. The influence of the reinforcing fibers content, their surface treatment, as well as of the temperature of AAROP upon the morphology, crystalline structure, and mechanical properties of the resulting SPCs was followed. The presence of oriented transcrystalline layer (TCL) on the surface of the reinforcing fibers was demonstrated by means of microscopy methods. Its orientation and polymorph structure were determined by synchrotron wide-angle X-ray scattering. Studies on the mechanical behavior in tension of the SPCs showed a well-expressed growth of the stress at break (70–80 %) and deformation at break (up to 150–190 %) in composites with 15–20 wt% of reinforcements. The best mechanical properties were found in SPCs whose reinforcing fibers were solvent-pretreated prior to AAROP in order to remove the original finish. In these samples a stronger adhesion at the fiber/matrix interface was proved by scanning electron microscopy of cryofractured samples. This effect was related to a thinner TCL in which the α-to-γ polymorph transition is impeded.     

Effect of testosterone incorporation on cell proliferation and differentiation for polymer–bioceramic composites

In the current study, we characterized the polycaprolactone (PCL), poly(lactic acid-co-glycolic acid) (PLGA), and biphasic calcium phosphate (BCP) composites coated with testosterone propionate (T) using Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (XRD). Osteoblastic cells were seeded with PCL/BCP, PCL/BCP/T, PLGA/PCL/BCP and PLGA/PCL/BCP/T scaffolds, and cell viability, proliferation, differentiation and adhesion were analyzed. The results of physic-chemical experiments showed no displacements or suppression of bands in the FTIR spectra of scaffolds. The XRD patterns of the scaffolds showed an amorphous profile. The osteoblastic cells viability and proliferation increased in the presence of composites with testosterone over 72?h, and were significantly greater when PLGA/PCL/BCP/T scaffold was tested against PCL/BCP/T. Furthermore alkaline phosphatase production was significantly greater in the same group. In conclusion, the PLGA/PCL/BCP scaffold with testosterone could be a promising option for bone tissue applications due to its biocompatibility and its stimulatory effect on cell proliferation.     

A facile way to fabricate novel 2–3-type composites based on zinc powders and polyvinylidene fluoride with enhanced dielectric properties

This study describes a simple and low-cost method for fabricating novel 2–3-type composites composed of zinc flakes and polyvinylidene fluoride (PVDF) by direct wet ball-milling and hot-pressing of the mixture of raw zinc powders and PVDF powders in alcohol. It is interesting that zinc spherical powders can be changed into 2-dimensional zinc flakes in the ball-milling and parallel oriented in the polymer under the following hot-pressing process. The composites are demonstrated to have significantly higher dielectric constants than those of bulk zinc/PVDF composites, with quite low dielectric loss and good thermal stability. A mechanism of parallel-board microcapacitor is proposed to explain the relationship of microstructure and dielectric properties.     

Preparation and characterization of hybrid antimicrobial materials based on Zn–Lu composites

The development of advanced functional materials, capable of providing effective antimicrobial activity, has a big demand from the contemporary society. Advanced functional antimicrobial amorphous silica composites (ASC) are prepared by using sol–gel process and modified by Zn ions and rare-earth element Lu. The preparation conditions are optimized by single-factor analysis, and as-prepared functional hybrids are characterized by scanning electron microscopy (SEM), X-ray diffraction analysis, X-ray photoelectron spectroscopy (XPS), atomic adsorption spectrometry and inductively coupled plasma analyses. The presence of homogeneously mixed Zn and Lu, in the form of ZnO and Lu₂O₃, and dense micropores is confirmed by SEM and XPS. The amorphous structure and large surface area are beneficial for better antimicrobial performance. The as-prepared Zn–Lu ASC exhibited excellent antimicrobial properties against Escherichia coli and Staphylococcus aureus. We demonstrate that the addition of rare-earth element, Lu, has rendered synergistic effect on antimicrobial properties by increasing the release of Zn ions and generating excess reactive oxygen species. The present study provides a mechanistic insight and novel approach to fabricate functional antimicrobial materials for a wide range of applications.     

Evolution analysis of online topics based on ‘word-topic’ coupling network

Scientometrics - Analyzing topic evolution is an effective way to monitor the overview of topic spreading. Existing methods have focused either on the intensity evolution of topics along a timeline...     

An X-ray and neutron reflectometry study of ‘PEG-like’ plasma polymer films

Plasma-enhanced chemical vapour-deposited films of di(ethylene glycol) dimethyl ether were analysed by a combination of X-ray photoelectron spectroscopy, atomic force microscopy, quartz crystal microbalance with dissipation monitoring (QCM-D), X-ray and neutron reflectometry (NR). The combination of these techniques enabled a systematic study of the impact of plasma deposition conditions upon resulting film chemistry (empirical formula), mass densities, structure and water solvation, which has been correlated with the films'' efficacy against protein fouling. All films were shown to contain substantially less hydrogen than the original monomer and absorb a vast amount of water, which correlated with their mass density profiles. A proportion of the plasma polymer hydrogen atoms were shown to be exchangeable, while QCM-D measurements were inaccurate in detecting associated water in lower power films that contained loosely bound material. The higher protein resistance of the films deposited at a low load power was attributed to its greater chemical and structural similarity to that of poly(ethylene glycol) graft surfaces. These studies demonstrate the utility of using X-ray and NR analysis techniques in furthering the understanding of the chemistry of these films and their interaction with water and proteins.     

Dynamic mechanical thermal analysis of all-PP composites based on β and α polymorphic forms

All polypropylene (all-PP) composites were manufactured by exploiting the polymorphic forms of PP, in which alpha (α)-PP tapes worked as reinforcement and beta (β)-PP served as matrix. The mechanical performance of the composite was investigated in a range of frequencies and temperatures using dynamic mechanical thermal analysis (DMTA). The volume fractions of matrix and reinforcement were estimated using optical microscope images. Both the DMTA and the static flexural bending tests revealed that the α-PP tapes act as an effective reinforcement for the β-PP matrix. Time–temperature superposition (TTS) was applied to estimate the stiffness of the composites as a function of frequency (f = 10⁻⁹...10²³) in the form of a master curve. The Williams–Landel–Ferry (WLF) model described properly change in the experimental shift factors used to create the storage modulus versus frequency master curve. The activation energies for the α and β relaxations were also calculated by using the Arrhenius equation.     

‘Green’ composites Part 1: Characterization of flax fabric and glutaraldehyde modified soy protein concentrate composites

Fully biodegradable, environment friendly ‘green’ composites were prepared using glutaraldehyde (GA) modified soy protein concentrate (MSPC-G) and flax fabric. Soy protein concentrate (SPC) polymer has low tensile properties, poor moisture resistance and is brittle. SPC polymer with 15% glycerin, as an external plasticizer, exhibited fracture stress and Young's modulus of 17 and 368 MPa, respectively. SPC polymer was cross-linked with GA to increase its tensile properties and improve its processability as a resin to manufacture flax fabric-reinforced composites. GA reacts with the free amine groups in SPC to form crosslinks. MSPC-G showed 20% increase in fracture stress and 35% increase in Young's modulus as well as improved moisture resistance compared to SPC. Besides the mechanical properties, MSPC-G was also characterized for its thermal stability and dynamic mechanical properties.Composite laminates, approximately 1 mm thick, were made using flax fabric and MSPC-G polymer. Composite specimens were prepared with two different orientations, namely, 0° or 90°. The laminates exhibited a Young's modulus of 1.01 and 1.26 GPa in the longitudinal and transverse directions, respectively. The experimental values were compared with the theoretical predictions using pcGINA^© software and showed good agreement. The composite specimens also showed good adhesion between flax fabric and MSPC-G resin.     

The morphology and phase mixing studies on poly(ester–urethane) during shape memory cycle

Three series of shape memory poly(ester–urethane) with varying hard-segment contents were synthesized. The materials were designed to display a three-phase structure consisting of a disperse phase formed by crystallites and hard domains embedded in an amorphous matrix. The initial undeformed morphology was investigated using techniques such as modulated differential scanning calorimetry, Fourier transform infrared spectroscopy, and wide angle X-ray scattering. These techniques were used to determine the phase separation, hydrogen-bonding structure, and crystalline fraction of the specimens prior to thermo-mechanical treatments. The obtained information was correlated with small angle X-ray scattering investigations of morphological changes that occurred during shape memory cycling. The deformation cycle led to the formation of an oriented nanostructure derived from chain alignment. The nanostructure recovered was observed to be triggered by the melting of the crystallites and bulk incompatibility. A relationship between the ability of the studied poly(ester–urethane) specimens to recover their original shape and their original nanostructure was determined.     

A ‘FE-Meshfree’ TRIA3 element based on partition of unity for linear and geometry nonlinear analyses

A new 3-node triangular element is developed on the basis of partition of unity (PU) concept. The formulation employs the parametric shape functions of classical triangular element (TRIA3) to construct the PU and the least square point interpolation method to construct the local displacement approximation. The proposed element synergizes the individual merits of finite element method and meshfree method. Moreover, the usual linear dependence problem associated with PU finite elements is eliminated in the present element. Application of the element to several linear and geometric nonlinear problems shows that the proposed element gives a performance better than that of classical linear triangular as well as linear quadrilateral elements, and comparable to that of quadratic quadrilateral element. The proposed element does not necessitate a new mesh or additional nodes in the mesh. It uses the same mesh as the classical TRIA3 element and is able to give more accurate solution than the TRIA3 element.     

Effects of annealing and deforming temperature on microstructure and deformation characteristics of Ti–Ni–V shape memory alloy

Effects of annealing temperature T_an and deforming temperature T_d on microstructure and deformation characteristics of Ti–50.8Ni–0.5V (atomic fraction, %) shape memory alloy were investigated by means of optical microscopy and tensile test. With increasing T_an, the microstructure of Ti–50.8Ni–0.5V alloy wire changes from fiber style to equiaxed grain, and the recrystallization temperature of the alloy is about 580 °C; the critical stress for stress-induced martensite σ_M of the alloy decreases first and then increases, and the minimum value 382 MPa is got at T_an = 450 °C; the residual strain ?_R first increases, then decreases, and then increases, and its maximum value 2.5% is reached at T_an = 450 °C. With increasing T_d, a transformation from shape memory effect (SME) to superelasticity (SE) occurs in the alloy annealed at different temperatures, and the SME → SE transformation temperature was affected by T_an; the σ_M of the alloy increases linearly; the ?_R of the alloy annealed at 350–600 °C decreases first and then tends to constant, while that of the alloy annealed at 650 °C and 700 °C decreases first and then increases. To get an excellent SE at room temperature for Ti–50.8Ni–0.5V alloy, T_an should be 500–600 °C.     

Effect of rolling conditions on the structure and shape memory properties of Fe–Mn–Si alloys

Lattice defects play an important role in controlling the γ → ε martensitic transformation in shape memory ferrous alloys. This work focuses on the relation between various rolling and annealing processes, the microstructure resulting from the processes, and strain recovery of two Fe–Mn–Si alloys with different stacking fault energies (SFEs). Rolling experiments, conducted over a temperature range from 20 °C to 1000 °C, produce quite different microstructures, which vary from a high dislocation density to a structure containing only few isolated dislocations. In addition, annealing temperature has a very important influence not only on the dislocation arrays but also on the stacking faults remaining in the austenite, whose density depends on the SFE value for the alloy. Within the framework of the processing parameters selected for this work, i.e. roll speed, rolling reductions, processing temperatures and schedules, rolling at intermediate temperatures and annealing at a temperature of 650 °C seem to be the most appropriate methods to obtain a microstructure favorable for a nearly full degree of shape recovery.     

Crosslinked poly(ε-caprolactone)/poly(sebacic anhydride) composites combining biodegradation,controlled drug release and shape memory effect

In this study, we investigated the shape memory effect and drug release behavior of a biodegradable polymeric composite consisted of crosslinked poly(ε-caprolactone) (cPCL) and poly(sebacic anhydride) (PSA). This composite was prepared by a solution-casting method. The drug delivery system was applied to cooperate with the shape memory property in the biodegradable polymeric composites for the first time. The effect of PSA addition on the mechanical, shape memory, in vitro degradation and drug release behavior was studied by static tensile test, dynamic mechanical analysis (DMA), FT-IR and degradation evaluation, etc. In vitro degradation and drug release results showed that the degradation speed of cPCL and the release accumulation of drug could be enhanced by adding PSA into cPCL matrix. The multifunctional polymer composite has great potential as drug eluting stents in biomedical field.     

The influence of cobalt oxide–graphene hybrids on thermal degradation,fire hazards and mechanical properties of thermoplastic polyurethane composites

In this work, cobalt oxide nanoparticles decorated on graphene nanosheets was firstly synthesized by a facile hydrothermal method. The structure and morphology of the synthesized hybrids were characterized by X-ray diffraction, Raman spectrum and Transmission electron microscopy measurements. Subsequently, the hybrids were introduced into thermoplastic polyurethane matrix for acting as reinforcements. The hybrids were well dispersed in thermoplastic polyurethane and no obvious aggregation of graphene nanosheets was observed. The obtained nanocomposites exhibited significant improvements in thermal stability, flame retardancy, mechanical properties and reduced the fire toxicity effectively, compared with those of neat polyurethane. The obvious improvements of these properties were mainly attributed to the ‘‘tortuous path’’ effect of graphene nanosheets, catalytic char formation function of cobalt oxide–graphene hybrids and the synergism between the catalysis effect of cobalt oxide nanoparticles and the adsorption effect of graphene nanosheets.     

The effects of water aging on the interphase region and interlaminar fracture toughness in polymer–glass composites

Three different unidirectional polymer–glass composite systems involving phenolic and polyester resins were aged for 6 and 11 weeks in tap water and tested in the mode I double cantilever beam (DCB) test. The results showed a dramatic increase in water absorption and a decrease in fracture toughness for phenolic/glass systems. Fractographic analysis revealed interfacial debonding to be dominant failure mechanism, indicating a strong influence of water degradation on fracture toughness results. The interphase region of each system was investigated using the nano-indentation and the nano-scratch techniques before and after aging in water. The nano-indentation test produced a series of indents as small as 30 nm in depth, to detect water degradation of the material properties at the interphase region between the fibre and the matrix. The nano-hardness results indicated interdiffusion in water aged interphase regions. The nano-scratch test was used in conjuction with the nano-indentation test, in order to detect the width of the interphase regions before and after water degradation. It was shown, from the coefficient of friction and the scratch profile depth, that the interphase region width increased and the material properties degraded during water aging. Qualitative links between water degradation of the glass–polymer interphase on a nanometer level and interlaminar fracture toughness are discussed.     

Hybridisation effect on diffusion kinetic and tensile mechanical behaviour of epoxy based flax–glass composites

This paper aims at investigating the hybridisation effect on the diffusion kinetic and the tensile mechanical behaviour of flax–glass fibres reinforced epoxy composites. For this purpose, hybrid composites composed of flax and glass fibre laminates with different stacking sequences were consolidated by compression moulding and subjected to environment ageing. The obtained results show that the water uptake and the diffusion coefficient are clearly reduced by the addition of glass fibre layers in flax laminate. The ageing conditions performed show that the flax–glass hybridisation presents a positive effect in a wet environment at low temperatures (∼20 °C) in the Young’s modulus and the tensile strength. For example, the Young’s modulus fell by 50% and 41% for hybrid laminates with 6% and 11% of glass fibres, and by 67% for the Flax laminate. However, the flax–glass hybridisation was not necessarily a relevant choice when the hybrid laminates were exposed in a wet environment at high temperatures. Indeed, at 55 °C, this hybridisation had a negative effect on the tensile strength and on the specific tensile strength.     

Investigating the effects of bulk supercooling and rapid solidification on Co–Ni–Ga ferromagnetic shape memory alloys

In this study, Electromagnetic Levitation (EML) technique was utilized to explore the effect of bulk supercooling and rapid solidification in alloys with Co₄₆Ni₂₇Ga₂₇ and Co₄₈Ni₂₂Ga₃₀ (at.%) compositions. The effects of γ + β on the martensitic and austenitic transformation temperatures and magnetic properties were investigated. The presence of γ phase was found to suppress the martensitic and austenitic transformations to below room temperature. Bulk supercooling and rapid solidification led to the formation of homogeneous martensitic phase from the hyperperitectic Co₄₆Ni₂₇Ga₂₇ alloy. In contrast with pure martensite phase in Co₄₈Ni₂₂Ga₃₀, the hyperperitectic martensite in supercooled Co₄₆Ni₂₇Ga₂₇ sample showed no grain boundaries microsegregation and embrittlement that caused deep cracks along grain boundaries. The sample had a high Curie temperature about 400 K and good directional magnetic properties.     

Influence of thermal cycling on the martensitic transformation and shape memory effect of a Fe－16Mn－

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