Amount Of Twist Research Articles

On the helical buckling of anisotropic tubes with application to arteries

The helical stability experienced by elastic cylinders is investigated using numerical methods. A doubly fiber-reinforced incompressible nonlinear elastic tube subject to axial loading, internal pressure and twist is examined using a numerical scheme based on the modified Riks (quasi-static) procedure. Under the application of such loadings (qualitatively physiological for arteries) vessels form tortuous shapes and a range of topologically and geometrically complex morphologies. These configurations can be highly unstable owing to the nonlinear interaction (geometry, material and self contact) among the multiple bifurcation modes. The present work attempts to model such complex configurations using a thick-walled cylindrical tube. These complex morphologies are most commonly termed as helical coiling, looping and winding in the biomechanics community. We show that these bifurcations are very sensitive to the applied pressure, axial stretch and the amount of twist. Illustration of the helical buckling is then provided by considering an anisotropic constitutive model that includes both fiber stretching and fiber shearing, as opposed to previous analyses that only consider fiber stretching. The numerical implementation is achieved via user routine in the finite element code Abaqus.

Research on Tooth Flank Twist Based on Orthogonal Polynomials Characterization

Tooth flank twist is a common phenomenon in the helical crowning modification of helical cylindrical gear, which reduces the performance of the gear. At present, the measurement of tooth flank twist is still in the stage of replacing surface with line. The development of 3-D measurement technology makes the acquisition of gear information more comprehensive and complete. By processing the 3-D point cloud data, the twist deviation on the tooth flank can be found, which is particularly important for improving the quality of the tooth flank. In this paper, a characterization method of tooth flank twist based on orthogonal polynomials was proposed, which can effectively separate the twist deviations existing on the tooth flank. The correctness of the method was verified by measurement experiments. Taking worm grinding wheel grinding to process helical crowning modification as an example, the model of various parameters of the gear and the amount of twist was established and the twist deviation in processing was predicted. This provides a new method for eliminating the twist deviation of the tooth flank.

YANGI TURDAGI TIBBIYOT BINTLARI UCHUN XOMASHYO XUSUSIYATLARI TADQIQI

This article presents the topicality of the problem, the sequence of technological processes in manufacture of silk twisted yarn from raw silk used for making of a medical bandage. In order to fold a few threads, and give them a twist, first raw silk is rewound onto a spool. Before rewinding, hanks are checked for gluing, in our case low gluing is determined, therefore, in order to soften the glued spots, the thread is treated with an emulsion by spraying. Then, the raw silk is kept in the common room and is rewound to the two flange reel using the MT-85 machine according to the Japanese technology. The principle of operation and technological drawings are provided. Torsion is carried out by adding 3 raw silk 2,33 tex to give the left twist S 350 tw/m and adding 8 raw silk 3,23 tex with the left twisting S 500 tw/m. The torsion process is performed on a TK-2 twisting machine. The process of fixing the twist of the finished twisted yarns is implemented using Japanese equipment SC-750. The quality indicators of twisted yarn are as follows: linear density, coefficient of variation in linear density, breaking load, breaking elongation, direction and amount of twist, and coefficients of variation in twisting.

A numerical structure-based method of simulating filament yarns

Simulation of yarn and filament behavior is very important due to its role in optimizing the processes of producing different types of yarn. Virtual yarn models make it possible to simulate the behavior of fabrics more accurately and that of sewing yarns in seam lines more realistically. The structure of yarns is an important factor affecting their behavior. However, in most studies in the field of yarn simulation, the structure of yarns is ignored, and they are simulated as single strings. In this paper, a model is developed to simulate the behavior of multi-filament yarns based on a multi-string structure and the inter-string forces affected by tension and twist. To this end, the properties that affect a yarn structure, such as the number of filaments, the amount of twist as well as the material and the fineness of the filaments, are incorporated into the model. In order to investigate the validity and accuracy of the proposed model, the simulated behavior is compared to the behavior of real yarns in six different modes. The results show that the model is able to simulate the behavior of yarns with an average error of 5.73%, as compared to reality. In order to investigate the effects of the yarn structure and the corresponding inter-structural forces on the yarn simulation, the yarn behavior is simulated with several simple single-strand models in which inter-string forces are not taken into account. A comparison of the models shows that the proposed one is able to yield results closer to reality and reduce the simulation error averagely for 7.76%.

The Creation of Twist by Reconnection of Flux Tubes

A fundamental process in a plasma is the magnetic reconnection of one pair of flux tubes (such as solar coronal loops) to produce a new pair. During this process magnetic helicity is conserved, but mutual helicity can be transformed to self-helicity, so that the new tubes acquire twist. However, until recently, when Wright (Astrophys. J.878, 102, 2019) supplied a solution, the partition of self-helicity between the two tubes was an outstanding puzzle. Here we examine Wright’s result in detail and apply it to a variety of cases. The simplest case, which Wright himself used to illustrate the result, is that of thin ribbons or flux sheets. We first explicitly apply his method to the usually expected standard case (when the tubes approach one another without twisting before reconnection) and confirm his result is valid for flux sheaths and tubes as well as sheets.For the reconnection of sheets, it is shown that the orientation of the sheets needs to be chosen carefully. For flux sheaths and tubes, Wright’s results are demonstrated to hold for the standard case. There is both a local and a global aspect to the effect of reconnection. The local effect of reconnection is to produce an equipartition of the added self-helicity (and therefore of twist), but the extra global effect of the location and orientation of the feet of the sheet, shell or tube in general adds different amounts of magnetic helicity to the two structures.It is important, as Wright realized, to account for any twist or writhe already existing in the fluxes prior to reconnection. Here we show explicitly that, if a section of a flux sheet is twisted by a multiple of pi with its ends held fixed and is then reconnected with another sheet, then the effect of the reconnection is to add that multiple of pi to one sheet and subtract it from the other, while conserving the total helicity. If, on the other hand, the central part of a flux sheath is twisted before reconnection by any angle, then the effect of reconnection is to add that amount of twist to one sheath and subtract it from the other, while conserving the total helicity. Thus, for the local part of the process in both sheets and sheaths, there is no longer helicity equipartition.Finally, we apply Wright’s results explicitly to flux tubes, and in particular to determine the twist that is acquired by an erupting flux rope due to reconnection during an eruptive solar flare or coronal mass ejection.

A practical guide for the use of contour locking plates for the repair of humeral diaphyseal fractures with proximal extension

IntroductionThe emergence of minimally invasive techniques has expanded the use of plates and improved their safety for the repair of humeral diaphyseal fractures with proximal extension. In this study, we aimed to determine the best contouring method for long locking plates in the repair of humeral fractures using this approach. Patients and methodsComparative observations were performed between helical and spiral modelling in plastic models to identify which shape best fits the contours of the humerus. To determine the best shape, we attempted to assess the torsion required for the plate to settle laterally in the greater tuberosity and anteriorly in the diaphyseal region of the humerus. After establishing the best approach, we transferred the method to two anatomical specimens and confirmed the viability of the method and pathways. Additionally, to confirm the clinical applicability of the method, we applied the method in ten patients. ResultsAfter placing the plates in the bone models, it was found that the helical plate was more distant from the bone. On the other hand, the spiral plate achieved better accommodation along the contours of the humerus. The amount of twist was tested at 50°, 70° and 90°. When the plate was twisted at 70°, it maintained contact with the greater tuberosity proximally and the anterior cortical diaphyseal region. Eight patients completed the follow-up. Radiographic consolidation and good functional outcomes were achieved in all patients. ConclusionsSpiral modelling at 70° allows anatomical accommodation at the greater tuberosity proximally and in the diaphyseal region.

Compositional and Structural Influence on Some Weft-Knitted Fabrics Comprised of Cotton and Lyocell Yarn

Cotton is the most commonly used natural fiber in knitting sector across the world. But lyocell is also gaining popularity these days in knitting sector due to its unique properties and environment friendliness. This study was carried out to find out the changes lyocell fiber can bring to weft-knitted fabric properties in respect of cotton and the possibility of using both cotton and lyocell yarns separately in the same fabric for cost-effective product. Four different weft-knitted fabric structures were produced using 100% cotton yarn and 100% lyocell yarn of the same count and stitch length, and then wales per inch, courses per inch, width, fabric areal density (g/m2), pilling resistance and bursting strength of the fabrics were compared. Results of the two sets of samples were found different as lyocell fabrics showed lower values in all tests except pilling resistance test. Two more fabrics were made with only single jersey plain structure: one of those by alternately feeding both 100% cotton and lyocell yarn in order to obtain a fabric composed of 50% cotton and 50% lyocell yarn and the other one by using 100% lyocell yarn only containing the same amount of twist as cotton yarn. Produced fabrics showed better results than 100% lyocell fabric in all experiments, while only the pilling resistance was found better than that of 100% cotton fabric. In the case of fabric structure, fabrics containing tuck stitches showed comparatively higher fabric width and fabric areal density, similar pilling resistance but lower bursting strength than fabric with only knit stitches.

Quality assessment of the drying process for Eucalyptus delegatensis timber using greenhouse solar drying technology

The aim of this study was to investigate the process of drying Eucalyptus delegatensis in a greenhouse solar kiln. Specific objectives were to assess stress formation, moisture gradients and timber distortion, the moisture content distribution within various sections of the timber stack, and internal checking and collapse development within the boards. The maximal temperature and relative humidity (RH) in the daytime were set at 43 °C/72% RH. At night time, the temperature was at ambient condition with 90% RH. The strain measurements were undertaken before and after the samples were sliced. The timber quality at the end of drying was assessed based on Australian and New Zealand standard (AS/NZS 4787:2001). The moisture content values in the three different sections (front, middle and end) of 2400 mm long boards were compared by Analysis of Variance. The results showed that the mean compressive strain was − 2 × 10− 4 mm/mm in the core layers and the tensile strain was 14 × 10− 4 mm/mm in the outer layers. All sample boards were within the acceptable limits for cupping, spring and bow, even though the relative humidity level did not reach the set value. However, the amount of twist in three out of twelve sample boards was above the acceptable limit. Mean moisture gradient was 0.6%. There was a significant difference in moisture content at the end section compared to the front and middle sections. Internal checking, collapse and residual stress were graded as Class “C” (class A is the highest grade and D is the lowest).

Dref-3 yarn structure with plied staple fibrous core

PurposeDref-3 friction spun core yarns produced using staple fibre yarn as the core, e.g. Jute core yarn wrapped with cotton fibre, have poorer mechanical properties compared to the core yarn itself. The purpose of this study was to understand the structure of such yarns, that will lead to the optimization of fibre, machine and process variables for production of better quality yarn from the Dref-3/3000 machines.Design/methodology/approachThe Dref spinning trials were conducted following a full factorial design with six variables, all with two operative levels. The Dref-3 friction spun yarn, in which the core is a plied, twisted ring yarn composed of cotton singles and the sheath, formed from the same cotton fibres making the singles, has been examined. The structures have also been studied by using the tracer fibre technique.FindingsIt was observed that rather than depending on the plied core yarn, the tensile properties of the Dref-3 yarn are significantly determined by the parameters those affect the constituent single yarn tensile properties, i.e. the amount of twist and its twist direction, yarn linear density and the sheath fibre proportion used during the Dref spinning in making the final yarn. Further, when the twist direction of single yarn, double yarn and the Dref spinning false twisting are in the same direction, the produced core-sheath yarn exhibits better tensile properties.Practical implicationsThe understanding of the yarn structure will lead to optimized production of all staple fibre core Dref spun yarns.Social implicationsThe research work may lead to utilization of coarse and harsh untapped natural fibres to the production of value-added textile products.Originality/valueThough an earlier research has reported the effects of sheath fibre fineness and length on the tensile and bending properties of Dref-3 friction yarn, the present study is the first documented attempt using the tracer fibre technique to understand Dref-3 yarn structure with plied staple fibrous core.

Studies on Thermal Behaviour of Cotton and Eri/Cotton Blended Fabrics Using Response Surface Methodology

Eri silk fibre, the lone domesticated non-mulberry variety of silk is reported to possess excellent thermal insulation property and the fabrics made of eri silk yarn is popularly used as warmth giving apparels by the people of north-eastern states of India in particular. On the other side, cotton fibre which is comparatively cheaper than eri silk has wide application in making apparel fabrics. This paper deals with the manufacturing of plain woven fabrics made of eri/cotton blended yarn as weft over cotton warp yarn and to conduct an in-depth study on the effect of blend composition and yarn parameters like count (Ne) and amount of twist on its thermal behaviour. The Box and Behnken model of Design of Experiment for three variables and three levels, a popular statistical tool, has been used to study the influence of chosen factors. The fitted regression equation has been found to be linear in nature confirming the presence of independent effect of yarn fineness, twist and eri content in the blended yarn over thermal insulation value of the fabric with strong degree of association. The effects of yarn count, twist and proportion of eri in blends have been well explained using response surface methodology.

The solar properties of fabrics produced using different weft yarns

Woven fabric is composed of two yarns system, known as the weft and warp yarns. Each yarn system has an effect on the physical, performance, and optical properties of fabric. Any change in one or both yarn systems greatly alters the fabric properties. The solar and luminous properties of fabrics are also affected by altering the weft yarn or both yarn systems. This study investigates the effect of altering the weft yarn system on the solar and luminous properties of fabrics. The differences in the weft yarn in the fabrics were based on the weft yarn structure, including the yarn linear density, amount of twist on the yarn, yarn evenness, hairiness, spinning method, fiber composition of the yarn, and weft density of the fabric. The fabric luminous and solar properties were measured according to EN 14500 using an ultraviolet-visible-near-infrared (UV/VIS/NIR) test device and calculated from the EN 410 standard test method. According to a variance analysis, the weft density factor is shown to have an effect on the solar properties of the fabric, especially the UV transmittance properties of the fabric. Although non-parametric test results with a 95% confidence level show that the yarn structure does not influence the solar characteristics of the fabric, we show from the test results that the yarn structure influences the solar properties of the fabric. Yarn hairiness was the dominant factor for the IR and visible portions of the solar radiation spectra. In the UV region, the fiber composition factor was found to be important. The effect of the yarn linear density was similar to the effect of the weft density factor. The solar transmittance decreases and the reflectance increases when the number of weft yarns per unit length is increased and the yarn linear density in the Ne numbered system is decreased. Increasing the yarn hairiness decreases the transmittance in the IR portion of the solar spectra. The degree of influence that the yarn structure has on the solar properties (with the exception of the UV portion) of the fabric was dominated by the number of weft yarns per unit length. The transmittance properties of the fabric were more affected by altering the yarn structure than the reflectance and absorbance properties.

On the twists of interplanetary magnetic flux ropes observed at 1 AU

AbstractMagnetic flux ropes (MFRs) are one kind of fundamental structures in the solar/space physics and involved in various eruption phenomena. Twist, characterizing how the magnetic field lines wind around a main axis, is an intrinsic property of MFRs, closely related to the magnetic free energy and stableness. Although the effect of the twist on the behavior of MFRs had been widely studied in observations, theory, modeling, and numerical simulations, it is still unclear how much amount of twist is carried by MFRs in the solar atmosphere and in heliosphere and what role the twist played in the eruptions of MFRs. Contrasting to the solar MFRs, there are lots of in situ measurements of magnetic clouds (MCs), the large‐scale MFRs in interplanetary space, providing some important information of the twist of MFRs. Thus, starting from MCs, we investigate the twist of interplanetary MFRs with the aid of a velocity‐modified uniform‐twist force‐free flux rope model. It is found that most of MCs can be roughly fitted by the model and nearly half of them can be fitted fairly well though the derived twist is probably overestimated by a factor of 2.5. By applying the model to 115 MCs observed at 1 AU, we find that (1) the twist angles of interplanetary MFRs generally follow a trend of about radians, where is the aspect ratio of a MFR, with a cutoff at about 12π radians AU−1, (2) most of them are significantly larger than 2.5π radians but well bounded by radians, (3) strongly twisted magnetic field lines probably limit the expansion and size of MFRs, and (4) the magnetic field lines in the legs wind more tightly than those in the leading part of MFRs. These results not only advance our understanding of the properties and behavior of interplanetary MFRs but also shed light on the formation and eruption of MFRs in the solar atmosphere. A discussion about the twist and stableness of solar MFRs are therefore given.

Strain energy function for isotropic non-linear elastic incompressible solids with linear finite strain response in shear and torsion

We find the strain energy function for isotropic incompressible solids exhibiting a linear relationship between shear stress and amount of shear, and between torque and amount of twist, when subject to large simple shear or torsion deformations. It is inclusive of the well-known neo-Hookean and the Mooney–Rivlin models, but also can accommodate other terms, as certain arbitrary functions of the principal strain invariants. Effectively, the extra terms can be used to account for several non-linear effects observed experimentally but not captured by the neo-Hookean and Mooney–Rivlin models, such as strain stiffening effects due to limiting chain extensibility.

Numerical solution of Schrödinger equation for biphoton wave function in twisted waveguide arrays

We consider the generation of entangled biphoton states with orbital-angular-momentum in triangular quadratic waveguide arrays with twisted geometry. For this purpose, we derive the Shrodinger equation for biphoton wave function and equation for pump field profile. We describe numerically the process of biphoton generation through spontaneous four-wave mixing. We suggest that biphoton correlations can be controlled by the amount of twist and pump field profile.

Abstract 1498: Alpha-Lipoic acid suppresses migration and invasiveness of thyroid cancer cells through inhibition of epithelial-mesenchymal transition .

Abstract Reactive oxygen species (ROS) are recently known as a contributor to tumor progression and metastasis through several mechanisms including induction of epithelial-mesenchymal transition (EMT), invasion, and tumor angiogenesis. In this study, we investigated the role of alpha-Lipoic acid (ALA), a potential antioxidant, on EMT in thyroid cancer cell lines. Human thyroid cancer-derived cell lines, BCPAP (BRAF V600E), HTH83 (HRAS Q61R), CAL62 (KRAS G12R), BHT101 (BRAF V600E), and FTC133 (PTEN null) were treated with ALA, and changes in ROS generation were measured by DCFH-DA. The expression of E-cadherin, vimentin and Twist were determined by immunoblot analysis. Cell migration and invasion were evaluated by scratch assay and by Boyden chamber assay. ALA significantly decreased intracellular ROS generation in most cell lines. The total amount of E-cadherin increased and those of vimentin and Twist decreased after ALA treatment in 4 thyroid cancer cell lines (BCPAP, HTH83, BHT101 and CAL62) in a dose-dependent manner (0.2∼1.0 mM). But, the changes in E-cadherin, vimentin and Twist were opposite in FTC133 cells. The cell migration and invasion ability decreased after treatment with ALA in all cell lines except FTC133 (PTEN null cell). These results suggest that ALA is a potential agent to inhibit EMT resulting in suppression of migration and of invasiveness in thyroid cancer cell lines with RAS or BRAF mutation, probably through reducing cellular amount of Twist. We suggest that it might be caused by antioxidant effects of ALA, but the exact mechanism of action of ALA is not clear yet. ALA could be a novel, potential agent to suppress metastasis of tumors in patients with thyroid cancer. Citation Format: Ji Min Han, Hyun-Jeung Choi, Ji Hye Yim, Won Gu Kim, Tae Yong Kim, Young Kee Shong, Eui Young Kim, Won Bae Kim. Alpha-Lipoic acid suppresses migration and invasiveness of thyroid cancer cells through inhibition of epithelial-mesenchymal transition . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1498. doi:10.1158/1538-7445.AM2013-1498

Optical vortex pulses

A new technique offers a stable train of laser pulses with a controllable amount of twist. A new technique offers a stable train of laser pulses with a controllable amount of twist.

Torsion of Incompressible Fiber-Reinforced Nonlinearly Elastic Circular Cylinders

Torsion of solid cylinders in the context of nonlinear elasticity theory has been widely investigated with application to the behavior of rubber-like materials. More recently, this problem has attracted attention in investigations of the biomechanics of soft tissues and has been applied, for example, to examine the mechanical behavior of passive papillary muscles of the heart. A recent study in nonlinear elasticity was concerned specifically with the effects of strain-stiffening on the torsional response of solid circular cylinders. The cylinders are composed of incompressible isotropic nonlinearly elastic materials that undergo severe strain-stiffening in the stress-stretch response. Here we investigate similar issues for fiber-reinforced transversely-isotropic circular cylinders. We consider a class of incompressible anisotropic materials with strain-energy densities that are of logarithmic form in the anisotropic invariant. These models reflect stretch induced strain-stiffening of collagen fibers on loading and have been shown to model the mechanical behavior of many fibrous soft biological tissues. The consideration of anisotropy leads to a more elaborate mechanical response than was found for isotropic strain-stiffening materials. The classic Poynting effect found for rubber-like materials where torsion induces elongation of the cylinder is shown to be significantly different for the transversely-isotropic materials considered here. For sufficiently large anisotropy and under certain conditions on the amount of twist, a reverse-Poynting effect is demonstrated where the cylinder tends to shorten on twisting The results obtained here have important implications for the development of accurate torsion test protocols for determination of material properties of soft tissues.

The effect of yarn twist direction on the formability of woven fabrics

This experimental work examines the influence of the yarn twist on the formability of a woven fabric. Consideration is given to the phenomenon of bedding between warp and weft yarns, as affected by the local helix angles of bent yarns. A total of 28 plain weave woven fabrics (four groups, each with seven samples) were produced, using Solospun™ yarns as warp and weft threads. The fabric bending length and the initial modulus of each sample were measured from which the formability was calculated. Results indicated that the fabrics in which the warp and weft twists are unidirectional (Z & Z) have higher formability in comparison to those fabrics in which the warp and weft twists are opposite to each other (Z & S). In addition, among the former fabrics the highest formability belongs to those in which the total helix angle of the warp and weft is close to 90 degree whereas the lowest formability belongs to the latter fabrics with least amount of twist.

THREE-DIMENSIONAL NONLINEAR EVOLUTION OF A MAGNETIC FLUX TUBE IN A SPHERICAL SHELL: INFLUENCE OF TURBULENT CONVECTION AND ASSOCIATED MEAN FLOWS

We present the first 3D MHD study in spherical geometry of the non-linear dynamical evolution of magnetic flux tubes in a turbulent rotating convection zone. We study numerically the rise of magnetic toroidal flux ropes from the base of a modelled convection zone up to the top of our computational domain where bipolar patches are formed. We compare the dynamical behaviour of flux tubes in a fully convective shell possessing self-consistently generated mean flows such as meridional circulation and differential rotation, with reference calculations done in a quiet isentropic zone. We find that two parameters influence the tubes during their rise through the convection zone: the initial field strength and amount of twist, thus confirming previous findings in Cartesian geometry. Further, when the tube is sufficiently strong with respect to the equipartition field, it rises almost radially independently of the initial latitude (either low or high). By contrast, weaker field cases indicate that downflows and upflows control the rising velocity of particular regions of the rope and could in principle favour the emergence of flux through Omega-loop structures. For these latter cases, we focus on the orientation of bipolar patches and find that sufficiently arched structures are able to create bipolar regions with a predominantly East-West orientation. Meridional flow seems to determine the trajectory of the magnetic rope when the field strength has been significantly reduced near the top of the domain. Finally differential rotation makes it more difficult for tubes introduced at low latitudes to reach the top of the domain.

Numerical simulations of the solar corona and Coronal Mass Ejections

Abstract Numerical simulations of Coronal Mass Ejections (CMEs) can provide a deeper insight in the structure and propagation of these impressive solar events. In this work, we present our latest results of numerical simulations of the initial evolution of a fast CME. For this purpose, the equations of ideal MagnetoHydroDynamics (MHD) have been solved on a three-dimensional (3D) mesh by means of an explicit, finite volume solver, where the simulation domain ranges from the lower solar corona up to 30R e. In order to simulate the propagation of a CME throughout the heliosphere, a magnetic flux rope is superposed on top of a stationary background solar (MHD) wind with extra density added to the flux rope. The flux rope is launched by giving it an extra initial velocity in order to get a fast CME forming a 3D shock wave. The magnetic field inside the initial flux rope is described in terms of Bessel functions and possesses a high amount of twist.