Filament Cross-section Research Articles

Influence of Twist on Selected Properties of Multifilament Yarn

Abstract Owing to twisting of filament fiber bundle, the structure and consequently various parameters and properties of a fiber bundle are changed. The aim of the work is to verify the effect of multifilament yarn twist (or twist coefficient) on selected mechanical properties such as multifilament tenacity, breaking elongation, and coefficient of fiber stress utilization in the yarn. Furthermore, the influence of twist on structural parameters such as the angle of peripheral fibers, the packing density, and the substance cross-sectional area of fiber bundle is observed. Two multifilament yarns with different filament cross-section shape and material were used for the experiment. Experimentally obtained data was compared with the known model dependencies derived decades ago based on the helical model. It can be stated that multifilament yarn retraction can be predicted based on the angle of peripheral fibers using the Braschler’s model. The coefficient of fiber stress utilization in the multifilament yarn determined experimentally corresponds with a theoretical curve, constructed according to Gégauff and Neckář, in the area of Koechlin’s twist coefficient α > 54 ktex1/2 m−1. Results as well as possible causes of deviations of experimental data from the theoretical one are discussed in this work.

Oxygen vacancy chain and conductive filament formation in hafnia

The stability and aggregation mechanisms of oxygen vacancy chains are studied for hafnia using self-energy corrected density functional theory. While oxygen vacancies tend not to align along the c-axis of monoclinic HfO2, oxygen vacancy chains along a-axis and b-axis are energetically favorable, with cohesive energies of 0.05 eV and 0.03 eV per vacancy, respectively. Nevertheless, with an increase of the cross section area, intensive oxygen vacancy chains become much more stable in hafnia, which yields phase separation into Hf-clusters and HfO2. Compared with disperse single vacancy chains, intensive oxygen vacancy chains made of 4, 6, and 8 single vacancy chains are energetically more favorable by 0.17, 0.20, and 0.30 eV per oxygen vacancy, respectively. On the other hand, while a single oxygen vacancy chain exhibits a tiny electronic energy gap of around 0.5 eV, metallic conduction emerges for the intensive vacancy chain made of 8 single vacancy chains, which possesses a filament cross section area of ∼0.4 nm2. This sets a lower area limit for Hf-cluster filaments from metallic conduction point of view, but in real hafnia resistive RAM devices the cross section area of the filaments can generally be much larger (>5 nm2) for the sake of energy minimization. Our work sets up a bridge between oxygen vacancy ordering and phase separation in hafnia, and shows a clear trend of filament stabilization with larger dimensions. The results could explain the threshold switching phenomenon in hafnia when a small AFM tip was used as the top electrode, as well as the undesired multimode operation in resistive RAM cells with 3 nm-thick hafnia.

Identification of intermittent transport in the scrape-off layer of MAST through high speed imaging

Using footage from high speed movies taken of the boundary plasma in the Mega Amp Spherical Tokamak (MAST) general properties of filaments are inferred through statistical moments. Filaments are observed up to and beyond the ψN=1.5 flux surface which, in single null configurations, lies well beyond the secondary separatrix and leads to filaments observed > 30cm from the top of the plasma. In the divertor filaments are observed to connect through to the target, however a quiescent region is observed close to the X-point where no coherent filaments are identified. This region coincides with a sharp rise in the integrated magnetic shear which may change the nature of the filament cross-section.

Magma mixing induced by particle settling.

A time series of experiments at high temperature have been performed to investigate the influence of particle settling on magma mixing. A natural rhyolite glass was held above a natural basalt glass in a platinum crucible. After melting of the glasses at superliquidus temperatures, a platinum sphere was placed on the upper surface of the rhyolitic melt and sank into the experimental column (rhyolitic melt above basaltic melt). Upon falling through the rhyolitic–basaltic melt interface, the Pt sphere entrained a filament of rhyolitic melt in its further fall. The quenched products of the experiments were imaged using X-ray microCT methods. The images of our time series of experiments document the formation of a rhyolite filament as it is entrained into the underlying basalt by the falling platinum sphere. When the Pt particle reached the bottom of the crucible, the entrained rhyolitic filament started to ascend buoyantly up to the initial rhyolitic–basaltic interface. This generated a significant thickness increase of a comingled “melange” layer at the interface due to “liquid rope coiling” and piling up of the filament. As a consequence, the basalt/rhyolite interface was greatly enlarged and diffusive hybridisation greatly accelerated. Further, bubbles, originating at the interface, are observed to have risen into the overlying rhyolite dragging basalt filaments with them. Upon crossing the basalt/rhyolite interface, the bubbles have non-spherical shapes as they adapt to the differing surface tensions of basaltic and rhyolitic melts. Major element profiles, measured across the rhyolite filaments, exhibit asymmetrical shapes from the rhyolite into the basalt. Na and Ti reveal uphill diffusion from the rhyolite towards the interface in the filament cross sections. These results reveal the potential qualitative complexity of the mingling process between rhyolitic and basaltic magmas in the presence of sinking crystals. They imply that crystal-rich magma mingling may be expected to be accelerated with respect to crystal-poor systems. We urge the further fluid dynamic analysis of these phenomena, obtainable for the first time using detailed tomographic imaging.Electronic supplementary materialThe online version of this article (doi:10.1007/s00410-016-1305-1) contains supplementary material, which is available to authorized users.

Dynamics of 3D isolated thermal filaments

Simulations have been carried out to establish how electron thermal physics, introduced in the form of a dynamic electron temperature, affects isolated filament motion and dynamics in 3D. It is found that thermal effects impact filament motion in two major ways when the pressure perturbation within the filament is supported primarily through a temperature increase as opposed to density: they lead to a strong increase in filament propagation in the bi-normal direction and a significant decrease in net radial propagation. Both effects arise from the temperature dependence of the sheath current which leads to a non-uniform floating potential, with the latter effect supplemented by faster pressure loss. The reduction in radial velocity can only occur when the filament cross-section loses angular symmetry. The behaviour is observed across different filament sizes and suggests that filaments with much larger temperature perturbations than density perturbations are more strongly confined to the near SOL region.

Effects of filament cross section on the performance of automotive upholstery fabrics

Aim of this study was to investigate the effects of filament cross section on the performance of automotive upholstery fabrics. Thirty-six yarns were produced by changing the cross section of poly(ethylene terephthalate) fibers (round, octolobal and W-channel) and the air-jet texturing parameters (overfeed and number of core and effect yarns). After heat-setting and dyeing the yarns were woven into fabrics and laminated. Performance tests of both the air-jet textured yarns and the fabrics were carried out. It was observed that W-channel gave the most different air-jet textured yarn structure. It formed a bulky, uneven yarn structure with many open loops. No pronounced difference in the recovery from strain behaviors of the air-jet textured yarns was recorded. For all the cross-section types, increase in the looped structure resulted in higher permanent elongation values. In case of fabrics, all the filament cross sections gave satisfactory results for the light fastness and the abrasion resistance tests. It was concluded that changing filament cross section had the most significant effect on air permeability. W-channel gave the lowest air permeability, while octolobal gave the highest one.

Mechanical Properties and Strain-Induced Filament Degradation of Ex Situ and In Situ MgB2Wires

We have compared the mechanical properties and the degradation of the critical current after uniaxial tensile loading at room temperature (RT) and at 77 K of ex situ and in situ MgB2 wires. The strain that the wires can withstand without degradation is at 77 K substantially higher than at RT. In order to explain the mechanical behavior of the wires, the lattice distortions of the different wire constituents and their texture have been measured simultaneously with the composite wire stress and strain in a high-energy synchrotron beamline. The different MgB2 microstructure in both wire types is revealed in filament cross sections prepared by the focused-ion-beam technique and in fracture surfaces.

Shape-controlled anisotropy of superparamagnetic micro-/nanohelices.

Micro-/nanopropellers can be actuated remotely by a rotating magnetic field and steered at high precision through various fluidic environments. Recent progress comprises microfabrication of superparamagnetic microhelices not possessing remanent magnetization, but rather magnetized by an applied magnetic field. In this article we present a numerical approach for computing, from first principles, the effective susceptibility of polarizable helical micro-/nanopropellers. We show that nanopropeller geometry, in particular, filament cross-section elongation and orientation, play a central role in determining its magnetic anisotropy and polarizability. The numerical predictions are in qualitative agreement with the previously reported experiments, showing that tight polarizable helices are propulsive. The numerical results are also supported by the approximate slender-body theory. Finally, we propose a semi-quantitative energy criterion to rank polarizable helices with different geometries of the filament by their propulsive capacity and also estimate their maximal propulsion speed.

MHD Seismology of a loop-like filament tube by observed kink waves

We report and analyze observational evidence of global kink oscillations in a solar filament as observed in Hα by instruments administered by National Solar Observatory (NSO)/Global Oscillation Network Group (GONG). An M1.1-class flare in active region (AR) 11692 occurred on 2013 March 15 and induced a global kink mode in the filament lying towards the southwest of AR 11692. We find periods of about 61–67 minutes and damping times of 92–117 minutes at positions of three vertical slices chosen in and around the filament apex. We find that the waves are damped. From the observed period of the global kink mode and damping timescale using the theory of resonant absorption, we perform prominence seismology. We estimate a lower cut-off value for the inhomogeneity length scale to be around 0.34–0.44 times the radius of the filament cross-section.

Numerical investigation of isolated filament motion in a realistic tokamak geometry

This paper presents a numerical investigation of isolated filament dynamics in a simulation geometry representative of the scrape-off layer (SOL) of the Mega Amp Spherical Tokamak (MAST) previously studied in Walkden et al 2013 (Plasma Phys. Control. Fusion 55 105005). This paper focuses on the evolution of filament cross-sections at the outboard midplane and investigates the scaling of the centre of mass velocity of the filament cross-section with filament width and electron temperature.By decoupling the vorticity equation into even and odd parity components about the centre of the filament in the bi-normal direction parallel density gradients are shown to drive large velocities in the bi-normal (approximately poloidal) direction which scale linearly with electron temperature. In this respect increasing the electron temperature causes a departure of the filament dynamics from two-dimensional (2D) behaviours.Despite the strong impact of three-dimensional effects the radial motion of the filament is shown to be relatively well predicted by 2D scalings. The radial velocity is found to scale positively with both electron temperature and cross-sectional width, suggesting an inertially limited nature. Comparison with the two-region model (Myra et al 2006 Phys. Plasmas 13 112502) achieves reasonable agreement when using a corrected parallel connection length due to the neglect of diamagnetic currents driven in the divertor region of the filament.Analysis of the transport of particles due to the motion of the filament shows that the background temperature has a weak overall effect on the radial particle flux whilst the filament width has a strong effect.

The investigation of barrier and comfort properties of multifunctional coated conductive knitted fabrics

The aim of this work was to investigate the barrier and comfort properties of protective uncoated and coated-impregnated three-layered knitted fabrics with different arrangements of special yarns, such as conductive yarns and yarns with different filament cross sections. Depending on content (7.5–30%) of conductive PES yarns with carbon core filaments and PES/stainless steel spun yarns, fabrics were grouped into A and B. In order to achieve multifunctional barrier and comfort properties, high porosity polyurethane and fluorocarbon resin coatings were applied. At the beginning of the research, the fabrics of groups A and B were coated with commercially available micro-porous polyurethane foam Tubicoat® MB according to the crushed foams method and impregnated with fluorocarbon water-repellent agent Tubiguard® 270. The achieved functional, barrier (water and oil repellency, resistance to water penetration, and electrostatic shielding), and comfort (air permeability, water vapor permeability, water retentivity, and drying intensiveness) properties were determined.

Lateral Exchange Smooths the Way for Vimentin Filaments

Lateral Exchange Smooths the Way for Vimentin Filaments

Role of filament cross-section in properties of PET multifilament yarn and fabric. Part I: Effect of fibre cross-sectional shape on transmission behaviour of fabrics

The transmission property of a fabric is a key factor that affects clothing’s comfort and decides the functional potential of clothing. The dependence of filament cross-section with varying shape factor (SF) on air, moisture and thermal transmission behaviour of fabric is determined in case of polyester multifilament woven fabrics. The linear density of each filament is kept identical for all 12 cross-section shape filaments. The SF of filament cross-section is an important factor which remained the prime factor to influence the transmission behaviour of fabric samples directly in many cases. Other indirect factors that influence the transmission behaviour of fabrics when the SF is identical are yarn structure, inter-fibre and inter-yarn space. Twelve different novel cross-sectional shapes are considered to make the multifilament woven polyester fabrics. The fabrics made from multifilament yarns having different SFs show that relative moisture vapour permeability and air permeability decrease with the rise in SF. Wickability increases with the rise in the SF of a filament cross-section. Multilobal, hexalobal and plus shapes were made a part of novel cross-sectional shapes in order to develop fabrics of higher comfort index.

Geochemistry and nano-structure of a putative ∼3240 million-year-old black smoker biota, Sulphur Springs Group, Western Australia

Filaments of pyrite found within a volcanic hosted massive sulphide (VHMS) deposit from the ∼3270–3230Ma Sulphur Springs Group of Western Australia have previously been interpreted as remnants of some of Earth's oldest thermophilic microbial communities. We here re-examine these pyrite filaments using a suite of in situ high spatial resolution techniques and provide new observations on their geochemistry, morphology, texture, distribution and habitat.A number of the Sulphur Springs filaments retain geochemical evidence for remnants of organic material. This takes the form of patches of carbon and nitrogen enrichment seemingly enclosed within a completely pyritised filament. The distribution of this organic material closely resembles that observed in younger bona fide pyritised filamentous microbes. Most filaments also possess a distinctive sponge-like nano-porous pyrite texture, which is replicated in younger pyritised microfossils and bio-mediated pyrite framboids, and is consistent with pyrite nucleation in an organic matrix. New 3D analyses confirm previous observations of approximately uniform filament diameters, lack of branching, clustering of filaments, plus zones of filaments with preferred orientations. Multiple sulphur isotope analyses indicate that the sulphur for pyritisation likely came from a mixture of seawater and magmatic sources, consistent with a black smoker type habitat and permissive of the presence of life in this setting.While these data are consistent with a biological interpretation for the Sulphur Springs filaments, perhaps as pyritised filamentous microorganisms or bundles of pyritised extra-cellular polymeric substances (EPS), the evidence is not compelling. Solid filament cross-sections and straight lengthwise morphology of most filaments resemble abiotic crystal needles or whiskers, while the parallel and radial alignments of filaments could be replicated by crystal growth patterns. Carbon and nitrogen enrichment could have occurred when organic material entrained within hydrothermal fluids was adsorbed onto these mineral crystals. Further work to obtain larger databases of nano-scale textures and morphologies from both biological and abiotic pyrite is needed before an abiotic formation mechanism can be confidently rejected.

Statistical analysis of the relationship between electrical transport and filament microstructure in multifilamentary Bi2Sr2CaCu2Ox/Ag/Ag–Mg round wires

After processing, multifilamentary Bi2Sr2CaCu2Ox (Bi2212) round wires have complex microstructures. In this study, the microstructures are analyzed quantitatively using a new statistical method in which filaments are categorized based on the predominant phases observed by cross-sectional scanning electron microscopy (SEM). A Matlab program is created to analyze the SEM micrographs and categorize over 100 filaments within the image. In total, 26 wires, each heat treated differently so as to vary the critical current density (Jc), are studied. In some wires, two distinct cross-sectional areas are analyzed, so a total of 41 cross-sections and 5506 filaments are characterized. Five filament types are defined: filaments containing predominantly Bi2212, filaments containing relatively large Bi2Sr2CuOx (Bi2201) grains, filaments containing relatively large alkaline earth cuprate (AEC) grains but no significant other non-Bi2212 phases, filaments containing relatively large copper-free (CF) grains but no other significant non-Bi2212 phases, and filaments containing relatively large AEC and CF grains. The majority of filaments (78% of all filaments classified) are either predominantly Bi2212 or containing-large-Bi2201 grains. Clear correlations between the number of these two types of filaments and the wire Jc are found; Jc is directly proportional to the percentage of ‘predominantly-Bi2212’ filaments. Although typically 70–90% of the containing-large-Bi2201 filament cross-sections is actually Bi2212 phase, Jc is inversely proportional to the percentage of this type of filament. Surprisingly, the correlations between Jc and the other filament types are weak or non-existent. Furthermore, using high-angle annular dark-field imaging in a scanning transmission electron microscope, Bi2201 intergrowths are found within Bi2212 grains, and results suggest possible differences in the Bi2201 intergrowth densities within Bi2212 grains extracted from predominantly Bi2212 filaments and those from Bi2201-containing filaments. These results indicate that significant enhancements in Bi2212 wire performance require either avoiding the formation of Bi2201, or ensuring complete conversion of Bi2201 to Bi2212.

Intermediate Filament Structure, Assembly and Nanomechanics

Intermediate filaments (IFs) consist of two-stranded coiled coils that form anti-parallel, half-staggered tetramers. By time-lapse electron microscopy, complemented with total internal reflection fluorescence (TIRF) microscopy, we have investigated the in vitro assembly of vimentin to define the assembly pathway for vertebrate cytoplasmic IFs. First, we have characterized the physical and structural state of the soluble vimentin subunits by analytical ultracentrifugation (AUC) and X-ray crystallography. Assembly is induced by a change in the ionic strength and starts with the lateral association of tetramers to full-width unit-length filaments (ULFs) driven by the interaction of the basic, non-structured head domains with the acidic coiled-coil rods. In a next step, ULFs longitudinally anneal by an end-on-addition mechanism to yield filaments. This mechanism is also exhibited by muscle desmin and the epithelial keratins, whereas the nuclear IF proteins, i.e. the lamins, do not assemble into ULFs. In a next step, the subunit composition of ULFs and IFs of different IF proteins was analyzed by scanning transmission electron microscopy (STEM) and cryo-electron tomography of native specimens. Depending on the ionic conditions used for assembly, on average keratin IFs harbor 8, vimentin IFs 16 and desmin IFs 24 coiled-coil dimers per filament cross-section. The formation of ULFs was investigated further by small-angle X-ray scattering (SAXS) and AUC, employing a mutant vimentin variant that is arrested in the ULF state. With these data at hand, we investigated the impact of human disease mutations found in desmin that cause myofibrillar myopathy. Last but not least, we explored the network formation of lamin A and some of its disease variants, which strongly deviates from that of cytoplasmic IFs. These data give a first mechanistic clue how the lamin network provides mechanical stability to the nuclear envelope and nuclear architecture.

Impact of ion valency on the assembly of vimentin studied by quantitative small angle X-ray scattering.

The assembly kinetics of intermediate filament (IF) proteins from tetrameric complexes to single filaments and networks depends on the protein concentration, temperature and the ionic composition of their environment. We systematically investigate how changes in the concentration of monovalent potassium and divalent magnesium ions affect the internal organization of the resulting filaments. Small angle X-ray scattering (SAXS) is very sensitive to changes in the filament cross-section such as diameter or compactness. Our measurements reveal that filaments formed in the presence of magnesium chloride differ distinctly from filaments formed in the presence of potassium chloride. The principle multi-step assembly mechanism from tetramers via unit-length filaments (ULF) to elongated filaments is not changed by the valency of ions. However, the observed differences indicate that the magnesium ions free the head domains of tetramers from unproductive interactions to allow assembly but at the same time mediate strong inter-tetrameric interactions that impede longitudinal annealing of unit-length filaments considerably, thus slowing down filament growth.

Punta Sayısının Örme Kumaşlarda Eğilme Dayanımı Üzerindeki Etkilerinin Araştırılması

In this study, it is aimed to investigate the effects of filament yarn’s number of nips on bending rigidity of knitted fabric which is made of that yarn. For this purpose, polyester POY (Partially Oriented Yarn) filaments with 283 dtex linear density and 68 filaments in cross section were used as raw material. POY bobbins were intermingled at different speed and pressure levels thus yarns having five different numbers of nips were produced. Single jersey knitted fabrics were produced using these yarns on the circular knitting sample machine. According to ASTM circular bending test method, bending rigidity of knitted fabrics was determined by using the digital pneumatic stiffness tester. The effects of the change in the number of nips on the bending rigidity of knitted fabrics were examined and the test results were analyzed statistically.

Comfort Characteristics of Knitted Active Sportswear: Liquid Water Transportation

Liquid water transport is a critical factor that affects the physiological comfort of sportswear. In this study, active kinds of sportswear of different international brands are studied and their liquid transport performances are evaluated. The fabric structure has been analysed by using a Leicamicroscope and the filament cross section has been analysed by using scanning electron microscopy. Vertical wicking against gravity is measured by using a vertical wicking tester. The in-plane flow of liquid is measured by using an in-plane gravimetric wicking tester. The liquid transport along the thickness is measured in terms of absorbency by using a gravimetric absorbency tester. It has been observed that the fabric structure, filament cross sectional shape and filament denier have substantial influence on liquid water transport.It is seen that with an increase in the fibre specific surface area, by changing the fibre shape factor and diameter, the wicking rate throughout the fabric increases.

Role of filament cross-section in properties of PET multifilament yarn and fabric. Part II: effect of fibre cross-sectional shapes on fabric hand

To investigate the effect of fibre cross-sectional shape on hand of polyethylene terephthalate continuous multifilament fabrics, different fabric samples are developed with similar fabric areal density, weave, yarn and fibre linear density. The effect of fibre cross-sectional shape on various structure–property relationship of fabric is precisely characterized. Different cross-sectional shapes have different stiffness as well as different packing index with ideal geometry of filament yarns. The low-stress mechanical properties and hand behaviour of fabric are also altered by change in cross-sectional shape of filaments. The experimental results indicate that the alteration in cross-sectional shape can be a powerful tool for fabric engineering.