pinecone/core-2020-05-10-deduplication huggingface dataset:
Fracture Mechanical Analysis of Cracks in Ice Shelves using the Finite Element Method and Configurational Forces

Ice shelves are important elements of the climate system and sensitive to climate changes. The disintegration of large Antarctic ice shelves is the focus of this fracture mechanical analysis. Ice is a complex material which, depending on the context, can be seen as a viscous fluid or as an elastic solid. A fracture event usually occurs on a rather short time scale, thus the elastic response is important and linear elastic fracture mechanics can be used. The investigation of the stress intensity factor as a measure of crack tip loading is based on a 2-dimensional analysis of a single crack with a mode-I type load and additional body loads. This investigation is performed using configurational forces. Depth dependent density and temperature profiles are considered. The relevant parameters are obtained by literature, remote sensing data analysis and modeling of the ice dynamics. The criticality of wet surface cracks is investigated
Direct numerical simulation of transition in MHD duct flow

Transition in the flow of electrically conducting fluid in a square duct with insulating walls is studied by direct numerical simulations. A uniform magnetic field is applied in the transverse direction. Moderate values of the Reynolds (  Re  = 5000 ) and Hartmann (  Ha  = 0 … 30 ) numbers are considered that correspond to the classical Hartmann & Lazarus [1] experiments. It is shown that the laminarization begins in the Hartmann layers, whereas the sidewall layers remain turbulent. Complete re‐laminarization occurs in the range of   R  =  Re / Ha  ≈︁ 220 , which is in agreement with the H. & L. experiments. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim
Analysis of Calving Events in Antarctic Ice Shelves Using Configurational Forces

Previous studies on the sensitivity of cracks in ice shelves with different boundary conditions, stress states and density profiles revealed the need for further analyses. As the transfer of boundary conditions from dynamic ice flow simulations to the linear elastic fracture analyses proved to be a critical point in previous studies, a new approach to relate viscous and elastic material behaviour is proposed. The numerical simulations are conducted using Finite Elements utilizing the concept of configurational forces. To show the applicability of the approach, a 2-dimensional plane stress geometry with volume loads due to the ice shelf flow is analyzed. The resulting crack path is compared to available crack paths from satellite images
A parametric study on creep-fatigue endurance of welded joints

This work is devoted to parametric study on creep-fatigue endurance of the steel AISI type 316N(L) weldments defined as type 3 according to R5 Vol. 2/3 procedure at 550◦C. The study is implemented using a novel direct method known as the Linear Matching Method (LMM) and based upon the creep-fatigue evaluation procedure considering time fraction rule for creep-damage assessment. Seven geometrical configurations of the weldment, which are characterised by individual values of a geometrical parameter p, are proposed. Parameter p, which represents different grades of TIG dressing, is a ratio between the radius of the fillet of the remelted metal on a weld toe and the thickness of welded plates. For each configuration, the total number of cycles to failure N⋆ in creep-fatigue conditions is assessed numerically for different loading cases including normalised bending moment ˜M and dwell period At. The obtained set of N⋆ is extrapolated by the analytic function dependent on ˜M , At and p. Proposed function for N⋆ shows good agreement with numerical results obtained by the LMM. It is used for the identification of Fatigue Strength Reduction Factors (FSRFs) effected by creep and dependent on At and p
Finite Element Simulation of Frost Wedging in Ice Shelves

Break-up events in ice shelves have been studied extensively during the last years. One popular assumption links disintegration events to surface melting of the ice shelf in conjunction with growing melt-water ponds, leading to hydro-fracture. As this explanation only holds during warm seasons [1], the possibility of frost wedging as forcing mechanism for autumn and winter break-up events is considered. Frost wedging can only occur if a closed ice lid seals the water inside the crack. Hence, the present study of frost wedging in a single crack uses ice lid thicknesses to evaluate the additional pressure on the crack faces. The investigation of the resulting stress intensity factor as a measure of crack criticality follows consequently. The results show that freezing water inside a crack can result in unstable crack growth of an initially stable water filled crack
Cyclic yield strength in definition of design limits for fatigue and creep

This study proposes a cyclic yield strength (CYS, σc ) as a key characteristic for the definition of safe design for engineering structures operating under fatigue and creep conditions. CYS is defined on a cyclic stress-strain curve, while monotonic yield strength (MYS, σm ) is defined on a monotonic stress-strain curve. Both values of σc and σm are identified using a 2-steps fitting procedure of the experimental stress-strain curves using Ramberg-Osgood and Chaboche material models. Comparison of σc and fatigue endurance limit σf on the S-N fatigue curve reveals that they are approximately equal. Hence, basically safe fatigue design is guaranteed in purely elastic domain defined by the σc . A typical creep rupture curve in time-to-failure approach for creep analysis has 2 inflections corresponding to the σc and σm . These stresses separate 3 sections on the creep rupture curve, which are characterised by 3 different creep fracture modes and 3 creep deformation mechanisms. Thus, basically safe creep design is guaranteed in linear creep domain with brittle failure mode defined by the σc . These assumptions are confirmed for several structural low- and high-alloy steels for normal and high-temperature applications
A Law for Small Scale, Continuous Calving

Ice shelves are formed by the viscous flow of inland ice into the ocean, they are floating and loosing mass by iceberg calving. There are two different kinds of calving: large tabular icebergs detach as singular events in time, and small scale calving occuring on a rather continuous time scale. Three visco-elastic approaches are discussed, in order to derive a general law for calving rates applicable to small scale calving. The results are highly dependent on the termination criterium for each approach, hence the computed calving rate has to be adapted and validated with measurements to get the most qualified value
Boundary Layer Heat Transport in turbulent Rayleigh-Bénard Convection in Air

We study the convective heat transfer in a large-scale Rayleigh-Bénard (RB) experiment which is called the “Barrel of Ilmenau”. We present the results of flow visualization and Particle Image Velocimetry (PIV) measurements of the near wall flow field in a plane perpendicular to the surface of the heated bottom plate. The experiment was run in a smaller rectangular inset that was placed inside the larger barrel. The Rayleigh number amounts to Ra=1.4 × 1010. The aspect ratios were Γx=1 in flow direction and Γy=0.26 perpendicular to the vertical flow plane. The measurements have been undertaken using a 2 W continuous wave Laser in combination with a light sheet optics and various cameras. Due to the slender geometry of the cell, the mean wind is confined in one direction where the Laser light sheet is aligned parallel. The flow was seeded with droplets of 1...2 µm size generated using an ordinary fog machine. Flow visualization as well as the PIV data clearly show the intermittent character of the boundary layer flow field that permanently switches between “laminar” and “turbulent” phases
How long does it take to consensus in the Hegselmann-Krause model?

Hegselmann and Krause introduced a discrete-time model of opinion dynamics
with agents having limit confidence. It is well known that the dynamics reaches
a stable state in a polynomial number of time steps. However, the gap between
the known lower and upper bounds for the worst case is still immense. In this
paper exact values for the maximum time, needed to reach consensus or to
discover that consensus is impossible, are determined for small number of
agents using an integer linear programming approach.Comment: 2 pages, 1 figur
Fluid pressure penetration for advanced FEA of metal-to-metal seals

This numerical study investigates the behaviour of the contact faces in the metal-to-metal seal of a typical pressure relief valve in the commercial FE-package ANSYS. The valve geometry is simplified to an axisymmetric problem, which comprises a simple representative geometry consisting of only three components. A cylindrical nozzle, which has a valve seat on top, contacts with a disk, which is preloaded by a compressed linear spring. Analysis considerations include the effects of the Fluid Pressure Penetration (FPP) across the valve seat which exists at two different scales. In-service observations show that there is certain limited fluid leakage through the valve seat at operational pressures about 90% of the set pressure, which is caused by the fluid penetrating into surface asperities at the microscale. At the macroscale, non-linear FE-analysis using the FPP technique available in ANSYS revealed that there is also a limited amount of fluid penetrating into gap, which is caused primarily by the global plastic deformation of the valve seat. Accurate prediction of the fluid pressure profile over the valve seat is addressed in this study by considering the FPP interaction on both scales. The shape of this pressure profile introduces an additional component of the spring force, which needs to be considered to provide a reliable sealing
A fully meshless method for ‘gas - evaporating droplet' flow modelling

A meshless method for modelling two-phase flows with phase transition is described. The method is based on consideration of three systems: viscous-vortex blobs, thermal-blobs and droplets; and can be applied for numerical simulation of 2D non-isothermal flows of ‘gas-evaporating droplets' in the framework of the one-way coupled two-fluid approach. The carrier phase is viscous incompressible gas. The dispersed phase is presented by a cloud of identical spherical droplets, and, due to evaporation, the radius and mass of droplets are time dependent. The carrier phase parameters are calculated using the viscous-vortex and thermal-blob method; the dispersed phase parameters are calculated using the Lagrangian approach. Two applications have been considered: (i) a standard benchmark - Lamb vortex; (ii) a cold spray injected into a hot quiescent gas. In the latter problem three cases corresponding to three droplet sizes were investigated. The smallest droplets (of the three cases considered) are more readily entrained by the carrier phase and form ring-like structures; the flow shows better mixing. Larger droplets evaporate less intensively. The medium sized droplets collect into two narrow bands stretched along the jet axis. The largest droplets form a two-phase jet, which remains close to the jet axis
Discussion of Different Model Approaches for the Flow Behavior of Ice

Ice of Antarctic ice shelves is assumed to behave on long-term as an incompressible viscous fluid, which is dominated on short time scales by the elastic response. Hence, a viscoelastic material model is required. The thermodynamic pressure is treated differently in elastic and viscous models. For small deformations, the elastic isometric stress for ν → 0.5 gives similar results to those solving for pressure in an incompressible laminar flow model. A viscous model, in which the thermodynamic pressure is approximated by an elastic isometric stress, can be easily extended to viscoelasticity
Tools for assessing and optimizing the energy requirements of high
  performance scientific computing software

Score-P is a measurement infrastructure originally designed for the analysis
and optimization of the performance of HPC codes. Recent extensions of Score-P
and its associated tools now also allow the investigation of energy-related
properties and support the user in the implementation of corresponding
improvements. Since it would be counterproductive to completely ignore
performance issues in this connection, the focus should not be laid exclusively
on energy. We therefore aim to optimize software with respect to an objective
function that takes into account energy and run time.Comment: The work described in this article was performed in the projects
  Score-E and READEX. Score-E is supported by the German Ministry of Education
  and Research under Grant No. 01IH13001A, and the project READEX has received
  funding from the European Union's Horizon 2020 research and innovation
  programme under Grant Agreement No. 67165
Nanofiller Fibre-Reinforced Polymer Nanocomposites

In this work, the technology of nano and micro-scale particle reinforcement
concerning various polymeric fibre-reinforced systems including polyamides (PA),
polyesters, polyurethanes, polypropylenes and high performance/temperature
engineering polymers such as polyimide (PI), poly(ether ether ketone) (PEEK),
polyarylacetylene (PAA) and poly p-phenylene benzobisoxazole (PBO) is reviewed.
When the diameters of polymer fibre materials are shrunk from micrometers to
submicrons or nanometers, there appear several unique characteristics such as
very large surface area to volume ratio (this ratio for a nanofibre can be as
large as 103 times of that of a microfibre), flexibility in surface
functionalities and superior mechanical performance (such as stiffness and
tensile strength) compared with any other known form of the material. However,
nanoparticle reinforcement of fibre reinforced composites has been shown to be a
possibility, but much work remains to be performed in order to understand how
nanoreinforcement results in dramatic changes in material properties. The
understanding of these phenomena will facilitate their extension to the
reinforcement of more complicated anisotropic structures and advanced polymeric
composite systems
Hydrolytic degradation of poly(ε-caprolactone) with different end groups and poly(ε-caprolactone-co--Y-butyrolactone): characterization and kinetics of hydrocortisone delivery

7 páginas, 8 figuras, 2 tablas.-- El pdf es el borrador del artículo.Asymmetric telechelic alfa-hydroxyl-ω-(carboxylic acid)-poly(ε-caprolactone) (HA-PCL), alfa-hydroxyl-ω-(benzylic ester)-poly(ε-caprolactone) (HBz-PCL), and an asymmetric telechelic copolymer alfa-hydroxyl-ω-(carboxylic acid)-poly(ε-caprolactone-co-Y-butyrolactone) (HA-PCB) were synthesized by ring-opening polymerization of ε-caprolactone (CL). CL and CL/-butyrolactone mixture were used to obtain homopolymers and copolymer respectively at 150°C and 2 hr using ammonium decamolybdate (NH4) [Mo10O34] (Dec) as a catalyst. Water (HA-PCL and HA-PCB) or benzyl alcohol (HBz-PCL) were used as initiators. The three polylactones reached initial molecular weights between 2000 and 3000 Da measured by proton nuclear magnetic resonance (1H-NMR). Compression-molded polylactone caplets were allowed to degrade in 0.5 M aqueous p-toluenesulfonic acid at 37°C and monitored up to 60 days for weight loss behavior. Data showed that the copolymer degraded faster than the PCL homopolymers, and that there was no difference in the weight loss behavior between HA-PCL and HBz-PCL. Caplets of the three polylactones containing 1% (w/w) hydrocortisone were placed in two different buffer systems, pH 5.0 with citrate buffer and pH 7.4 with phosphate buffer at 37°C, and monitored up to 50 days for their release behavior. The release profiles of hydrocortisone presented two stages. The introduction of a second monomer in the polymer chain significantly increased the release rate, the degradation rate for HA-PCB being faster than those for HBz-PCL and HA-PCL. At the pH studied, only slight differences on the liberation profiles were observed. SEM micrographs indicate that hydrolytic degradation occurred mainly by a surface erosion mechanism.The financial support by Consejo Nacional de Ciencia y Tecnología and Universidad de Guanajuato is acknowledged. L.M.O.C. thanks Consejo Nacional de Ciencia y Technología\ud
(CONACYT) for a Ph.D. scholarship.Peer reviewe
Characterization of polyether-poly(methyl methacrylate)-lithium perchlorate blend electrolytes

Em publicaçãoSolid polymer electrolytes (SPEs) systems based on interpenetrating blends of poly(ethylene oxide-co-propylene oxide) and poly(methyl methacrylate) host matrices, with lithium perchlorate as guest salt, were prepared. These electrolytes were presented as free-standing films, and their thermal and electrochemical properties were characterized by conductivity and electrochemical stability measurements.
The properties of the interpenetrating blends of poly(ethylene oxide-co-propylene oxide) and poly(methyl methacrylate) host matrices as the electrolyte component of a solid-state electrochromic device are reported and the results obtained suggest that this electrolyte provides an encouraging performance in this application. The most conducting electrolyte composition of this SPE system is the formulation designated as SPE2-0PC (5.01x10-4 S cm-1 at about 57ºC). The lowest decomposition temperature was registered with the SPE6-15PC composition (233ºC). The average transmittance in the visible region of the spectrum was above 41% for all the samples analyzed. After coloration the device assembled with 71 wt% PC presented an average transmittance of 15.71% and an optical density at 550nm of 0.61.Fundação para a Ciência e a Tecnologia (FCT
Morphology and conduction properties of graphite-filled immiscible PVDF/PPgMA blends

Graphite was dispersed in immiscible polyvinylidene "uoride/maleated polypropylene (PVDF/PPgMA) blends to improve electrical and thermal conductive properties by building a double-percolation structure. The morphology of PVDF/PPgMA blends was !rst investigated for several compositions by selective solvent extraction, scanning electron microscopy, and dynamic mechanical thermal analysis. Blends of PVDF and PPgMA were prepared in different relative fractions, and a PVDF/PPgMA ratio of 7/3 showed a well-co-continuous structure. From this blend, the morphology and properties of composites with different concentrations of graphite were investigated to prepare double-percolated structures. Graphite was observed to selectively localize in the PPgMA phase. The electrical and thermal conductive properties of graphite-containing blends were measured, showing enhanced conductivity for the double-percolation structures compared with single-polymer composites containing the same graphite loading
Structure and blood compatibility of highly oriented poly(lactic acid)/thermoplastic polyurethane blends produced by solid hot stretching

YesHighly oriented poly(lactic acid) (PLA)/thermoplastic polyurethane (TPU) blends were fabricated through solid hot stretching technology in an effort to improve the mechanical properties and blood biocompatibility of PLA as blood-contacting medical devices. It was found that the tensile strength and modulus of the blends can be improved dramatically by stretching. With the increase of draw ratio, the cold crystallization peak became smaller, and the glass transition and the melting peak moved to high temperature, while the crystallinity increased, and the grain size of PLA decreased, indicating of the stress-induced crystallization during drawing. The oriented blends exhibited structures with longitudinal striations which indicate the presence of micro-fibers. TPU phase was finely and homogeneously dispersed in the PLA, and after drawing, TPU domains were elongated to ellipsoid. The introduction of TPU and orientation could enhance the blood compatibility of PLA by prolonging kinetic clotting time, and decreasing hemolysis ratio and platelet activation
Layer-by-layer deposition of antimicrobial polymers on cellulosic fibers : a new strategy to develop bioactive textiles

In recent years, there has been an increase of infectious diseases caused by different microorganisms and the development of antibiotic resistance. In this way, the search for new and efficient antibacterial materials is imperative. The main polysaccharides currently used in the biomedical and pharmaceutical domains are chitin and its derivative chitosan (CH) and alginates (ALG). In this study, a simple technique of Layer by Layer (LbL) of applying polycation CH and polyanion ALG was used to prepare CH/ALG multilayers on cotton samples via the electrostatic assembly with success. The CH/ALG cotton samples (functionalized) were investigated for their antibacterial properties towards Staphylococcus aureus and Klebsiella pneumonia using the international standard method JIS L 1902:2002. The antibacterial activity of the functionalized samples was tested in terms of bacteriostatic and bactericidal activity, and results showed that the samples exhibited a bacteriostatic effect on the two bacteria tested, as expected. In addition, samples with five layers (CH/ALG/CH/ALG/CH) were more effective in inhibiting bacterial growth. This new coating for cellulosic fibers is a new strategy and may open new avenues for the development of antimicrobial polymers with potential application in health-care field.The authors would like to thank Fundacao para a Ciencia e Tecnologia (FCT) for the funding granted concerning the project - PTDC/EBB-BIO/113671/2009 (FCOMP-01-0124-FEDER-014752) Skin2Tex. Also, we would like to thank Fundo Europeu de Desenvolvimento Regional (FEDER) through COMPETE - Programa Operacional Factores de Competitividade (POFC) for the co-funding
Preparation of electrospun nanofibers from solutions of different gelatin types using a benign solvent mixture composed of water/PBS/ethanol

The feasibility of using Phosphate Buffer Saline (PBS)/ethanol mixtures as a benign solvent to electrospin three types of gelatin was studied. Gelatins with different chemical properties, such as Bloom, were selected and the effect of the gelatin nature and its concentration on the electrospinnability of the dope solution and on the fiber diameter of the electrospun mats were studied. Viscosity of the gelatin solution, which follows a power law relationship with the gelatin concentration, was found to significantly influence the morphology of the mats and the fiber diameter. It was demonstrated that the PBS/ethanol solvent interacted with the gelatins as a good solvent with a Flory exponent of 0.65. In addition, the effect of the solvent composition on the fiber formation process was evaluated corroborating that the ionic strength of the medium and the PBS/ethanol ratio significantly affected the morphology and the diameter of the electrospun fibers. Chemical structure and thermal stability of the electrospun gelatin mats were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC). Finally, cytotoxicity of the electrospun mats was analyzed by the Alamar Blue assay, using human foreskin fibroblasts (BJ-5ta), resulting in a high cell viability (80-90%) regardless the type of gelatinPostprint (author's final draft