Number Of Twists Research Articles

Detection of natural pulse waves (PWs) in 3D using high frame rate imaging for anisotropy characterization

IntroductionNumerous studies have shown that natural mechanical waves have the potential to assess the elastic properties of the myocardium. When the Aortic and Mitral valves close, a shear wave is produced, which provides insights into tissue stiffness. In addition, the Atrial Kick (AK) generates a wave similar to Pulse Waves (PWs) in arteries, providing another way to assess tissue stiffness. However, tissue anisotropy can also impact PW propagation, which is currently underexplored. This study aims to address this gap by investigating the impact of anisotropy on PW propagation in a phantom.MethodsTube phantoms were created using Polyvinyl Alcohol (PVA). Anisotropy was induced between two sets of two freeze-thaw cycles by stretching and twisting the material. The study first tests and validates the procedure of making helical anisotropic vessel phantoms using the shear wave imaging technique (by estimating the shear wave speed at different probe angles). Using plane wave ultrasound tomography synchronized with a peristaltic pump, 3D high frame rate imaging is performed and used to detect the 3D propagation pattern of PW for each manufactured vessel phantom. Finally, the study attempts to extract the anisotropic coefficient of the vessel using pulse wave propagation angle.ResultsThe Shear wave imaging results obtained for the isotropic vessel show very similar values for each probe angle. On the contrary, the results obtained for the axial anisotropy vessel show a region with a higher shear wave speed at about 0°, corresponding to the long axis of the vessel. Finally, the results obtained for the helical anisotropy depicted increasing shear wave velocity value from −20° to 20°. For the axial phantom, the wavefront of the pulse wave is perpendicular to the long axis of the vessel, while oriented for the helical anisotropic vessels phantom. The pulse wave propagation angle increased with the number of twists made during the vessel manufacturing.DiscussionThe results show that anisotropy can be induced in PVA vessel phantoms by stretching and twisting the material in freeze-thaw cycles. The findings also suggest that vessel anisotropy affects pulse wave propagation angles. Estimating the pulse wave propagation angle may be interesting in characterizing tissue anisotropy in organs where such waves are naturally present.

Triggering mechanism of an eruptive filament located in a weak active region

IntroductionThe triggering mechanism for filaments located in a weak magnetic field typically leans toward magnetohydrodynamic instabilities due to the weak magnetic strength inherent in filament structures. However, a subset of eruption events associated with significant flares remains. Therefore, we seek to understand the role that reconnection plays in the eruption of filaments with weak magnetic fields.MethodsWe reconstruct the coronal magnetic field of an eruptive filament located in a relatively weaker magnetic environment, and analyze the magnetic field properties such as twist number and squashing factor.ResultsThis filament remains stable until the expansion of the heated bright arcades underneath. This expansion initially activates the filament, prompting its upward movement, leading to a gentle reconnection slightly to its south. The ensuing reconnection continues to propel the filament upward with uniform acceleration. These upward motions cause the drainage of filament mass, likely activating the torus instability of the filament. This torus instability then triggers the final eruption of the filament, successfully generating a coronal mass ejection (CME) and leaving behind a double-ribbon flare.DiscussionWe conclude that the torus instability serves as the primary triggering mechanism of this eruption, while pre-eruption reconnection plays a role in pushing the filament upward to meet the instability condition.

Pull-out behavior of twin-twisted steel fibers from various strength cement-based matrices

This research explores a novel steel fiber made by twisting together two straight steel wires. The pull-out behavior of the twin-twisted steel fiber was investigated, proving its slip-hardening ability in cement-based matrices. The number of twists per unit length, fiber embedment length, matrix compressive strength, and fiber equivalent diameter were the experimental variables. Hooked-end fibers were also investigated for comparison. Pull-out test results of twin-twisted steel fibers quantified the mechanisms of frictional bonding and mechanical untwisting and their effects on the pull-out response and slip hardening of steel fibers. The maximum pull-out load increased with the increase of fiber twists per unit length, which increased the likelihood of damage to the matrix tunnel and had a negative effect on the energy absorption capacity. Defects at interfaces and scratches on fiber surfaces were examined using SEM imaging. Twin-twisted steel fibers reached an enhanced hardening response and energy absorption capacity compared to hooked fibers yet showed lower maximum bond strength. New bond strength and energy dissipation indexes were introduced and could effectively be used for fiber optimization.

Therapeutic effect of iridoid and xanthone glycosides components extracted from Swertia Mussotti on calculous cholecystitis and its clinical complications by targeting COX2

Swertia Mussotti is used as febrifuge, analgesic and to treat calculous cholecystitis, however, the underling mechanism remains unclear. This study investigates the therapeutic effect of the active fraction named iridoid and xanthone glycoside (IXG) extracted from S. mussotii on six animal models related to calculous cholecystitis and its complications, and to explore its potential target proteins. Four main compounds including swertiamarin (STR), sweroside (SRS), gentiopicroside (GPS) and mangiferin (MGR) were identified from the IXG by UHPLC-TOF-MS. The in vivo experiments results confirmed that IXG significantly decreased the level of total bilirubin (TBIL), direct bilirubin (DBIL) and cyclooxygenase-2 (COX2) in calculous cholecystitis. IXG treatment dramatically reduced the number of twists and the time of clicking foot in 2nd phase induced by glacial acetic acid and formalin, however, no effect was showed on central pain established by hot plate test. IXG also significantly decreased the anal temperature induced by yeast and 2,4-dinitrophenol. These results indicated that IXG alleviate calculous cholecystitis and its clinical symptom. In addition, IXG suppressed the expression of Prostaglandin E2 (PGE2) in vitro. Mechanistically, COX2 was identified as the direct target of IXG in RAW264.7 cells, and downregulated the protein levels of COX2. The results confirmed that IXG ameliorates calculous cholecystitis and its clinical symptom (pain and fever) by suppressing the production of PGE2 through targeting COX2.

Influence of wet wire drawing speed on the brass-plated steel cord properties

Steel cords are a reinforcing phase of the rubber-steel-canvas composite, and their properties, including strength, depend on the quality of the wires. The novelty of the work is a multi-parameter analysis of the cord production process, which showed that there is a relationship between the rheological properties of the lubricating emulsion, the friction conditions and deformation of the brass coating, and the properties of the wires and their resistance to cracking when braiding into a steel cord. It was shown that the friction conditions depend on the wire temperature and the rheological properties of the emulsion. As the drawing speed increases, the emulsion viscosity improves. The grease reaches its optimum at a specific drawing speed depending on the type of emulsion and the type of wire. Further increases in drawing speed result in an increase in temperature at the material/tool interface. This leads to a decrease in the viscosity of the emulsion and the breakdown of the lubricant film in the contact zone. Inappropriate selection of wet drawing speed contributes to a decrease in plastic properties and a reduction in the number of twists and bends of the wire, which leads not only to wire breakage at the stage of cord braiding but also to its premature breaking during the tensile test.

Optimizing one-axis twists for variational Bayesian quantum metrology

Quantum metrology and sensing seek advantages in estimating an unknown parameter of some quantum state or channel, using entanglement such as spin squeezing produced by one-axis twists or other quantum resources. In particular, qubit phase estimation, or rotation sensing, appears as a ubiquitous problem with applications to electric field sensing, magnetometry, atomic clocks, and gyroscopes. By adopting the Bayesian formalism to the phase estimation problem to account for limited initial knowledge about the value of the phase, we formulate variational metrology and treat the state preparation (or encoding) and measurement (or decoding) procedures as parameterized quantum circuits. It is important to understand how effective various parametrized protocols are as well as how robust they are to the effects of complex noise such as spatially correlated noise. First, we propose a family of parametrized encoding and decoding protocols called arbitrary-axis twist ansatzes, and show that it can lead to a substantial reduction in the number of one-axis twists needed to achieve a target estimation error. Furthermore, we demonstrate that the estimation error associated with these strategies decreases with system size in a faster manner than classical (or no-twist) protocols, even in the less-explored regimes where the prior information is limited. Last, using a polynomial-sized tensor network algorithm, we numerically analyze practical variational metrology beyond the symmetric subspace of a collective spin and find that quantum advantage persists for the arbitrary-axis twist ansatzes with a few one-axis twists and smaller total twisting angles for practically relevant noise levels. Published by the American Physical Society 2024

Analysis of modeled 3D solar magnetic field during 30 X/M-class solar flares

Using non-linear force free field (NLFFF) extrapolation, 3D magnetic fields were modeled from the 12-min cadence Solar Dynamics Observatory Helioseismic and Magnetic Imager (HMI) photospheric vector magnetograms, spanning a time period of 1 hour before through 1 hour after the start of 18 X-class and 12 M-class solar flares. Several magnetic field parameters were calculated from the modeled fields directly, as well as from the power spectrum of surface maps generated by summing the fields along the vertical axis, for two different regions: areas with photospheric |Bz|≥ 300 G (active region—AR) and areas above the photosphere with the magnitude of the non-potential field (BNP) greater than three standard deviations above |BNP|̄ of the AR field and either the unsigned twist number |Tw| ≥ 1 turn or the shear angle Ψ ≥ 80° (non-potential region—NPR). Superposed epoch (SPE) plots of the magnetic field parameters were analyzed to investigate the evolution of the 3D solar field during the solar flare events and discern consistent trends across all solar flare events in the dataset, as well as across subsets of flare events categorized by their magnetic and sunspot classifications. The relationship between different flare properties and the magnetic field parameters was quantitatively described by the Spearman ranking correlation coefficient, rs. The parameters that showed the most consistent and discernable trends among the flare events, particularly for the hour leading up to the eruption, were the total unsigned flux ϕ), free magnetic energy (EFree), total unsigned magnetic twist (τTot), and total unsigned free magnetic twist (ρTot). Strong (|rs| ∈ [0.6, 0.8)) to very strong (|rs| ∈ [0.8, 1.0]) correlations were found between the magnetic field parameters and the following flare properties: peak X-ray flux, duration, rise time, decay time, impulsiveness, and integrated flux; the strongest correlation coefficient calculated for each flare property was 0.62, 0.85, 0.73, 0.82, −0.81, and 0.82, respectively.

Transverse Spin Hall Effect and Twisted Polarization Ribbons at the Sharp Focus

Transverse Spin Hall Effect and Twisted Polarization Ribbons at the Sharp Focus

Determining triple half-twist of optical Möbius strips in electromagnetic fields with a non-planar structure.

Polarization ellipses in a nonparaxial field form twisted strips when traced along closed contours around a circular polarization singularity line. We found an analytical expression for the twist number of the strip when the contour is coplanar with the polarization ellipse in its center. Necessary and sufficient conditions for strips having one or three half-twists are found. A set of five parameters of electromagnetic field at the polarization singularity point is found which definitely determines the value of the twist number of the strip.

Onset mechanism of an inverted U-shaped solar filament eruption revealed by NVST, SDO, and STEREO-A observations

Context. Solar filaments, also called solar prominences when appearing on the solar limb, consist of dense, cool plasma suspended in the hot and tenuous corona. They are the main potential sources of solar storms. Aims. To understand the onset mechanism of solar filaments, we investigated the eruption process of an inverted U-shaped solar filament and two precursory jet-like activities. Methods. Using observations from the New Vacuum Solar Telescope (NVST), the Solar Dynamics Observatory (SDO), and the Solar Terrestrial Relations Observatory-Ahead (STEREO-A), we investigated the event from two distinct observational perspectives: on the solar disk using NVST and SDO, and on the solar limb using STEREO-A. We employed both a nonlinear force-free field model and a potential field model to reconstruct the coronal magnetic field with the aim to understand its magnetic properties. Results. Two precursor jet-like activities were observed before the eruption, displaying an untwisted rotation. The second activity released an estimated twist of over two turns. During these two jet-like activities, Y-shaped brightenings, which are newly emerging magnetic flux accompanied by magnetic cancellation, and the formation of newly moving fibrils were identified. When these observational features are combined, it can be inferred that these two precursor jet-like activities released the magnetic field that constrained the filament and were caused by newly emerging magnetic flux. Before the filament eruption, it was observed that some moving flows had been ejected from the site as the onset of two jet-like activities, indicating the same physical process as in the two jet-like activities. Extrapolations revealed that the filament was below the height of the decay index of 1.0 and had a strong magnetic field (540 Gauss) and a high twist number (2.4 turns) before the eruption. An apparent rotational motion was observed during the filament eruption. Conclusions. We deduce that the solar filament, exhibiting an inverted U-shape, is a significantly twisted flux rope. The eruption of the filament was initiated by the release of constraining magnetic fields through continuous magnetic reconnection. This reconnection process was caused by the emergence of new magnetic flux.

<i>In Situ</i> Measurement of Twist Propagation and Yarn Tension with Superconducting Magnetic Bearing Twisting Element for Ring Spinning Process

The twisting of yarn in one of the most widely used conventional ring spinning processes is based on the ring/traveler system. The existing limitation of productivity in the ring spinning process lies on the prevailing force relation between ring, traveler and yarn as well as the frictional heat between traveler and ring, principally in the ring traveler system. Recently, a frictional free twisting element based on a superconducting magnetic bearing (SMB) was developed to increase the productivity of ring spinning drastically, which was patented by ITM and Leibniz IFW Dresden. This SMB consists of a circular superconductor and a permanent magnet (PM) ring. In the superconducting state, the PM ring levitates and can freely rotate even up to an angular speed of 50.000 rpm. It is connected with the spindle via the yarn through a guide attached to the PM ring to impart yarn twist. Through the rotation of the PM ring, the twist propagates to the nip point of the delivery rollers. The twist propagation rate depends on different parameters, e.g., spindle speed, balloon geometry, and friction between yarn and yarn guides. A change in the level of twist affects the process, yarn tension, yarn breakage rate, and yarn properties. Hence, it is important to investigate the twist distribution to derive effective measures for improving the twist propagation especially at higher angular spindle speeds and thus eliminate weak points to increase process stability and yarn quality. The aim of these measurements is to analyze the twist distribution along the yarn path to understand the causes of yarn breakages. In this study, the yarn path was traced at different regions by in-situ measuring the helix angle of twisted yarn using a high-speed camera. From the recorded images, the number of twists per unit length was determined using the image processing software ‘Image J’. Thus, the measurement method allows a new insight into the problem of yarn breakages originating from twist propagation in order to take optimized measures at higher angular spindle speeds.

Enhanced Twist-Averaging Technique for Magnetic Metals: Applications Using Quantum Monte Carlo.

We propose an improved twist-averaging (TA) scheme for quantum Monte Carlo methods that use converged Kohn-Sham or Hartree-Fock orbitals as the reference. This TA technique is tailored to sample the Brillouin zone of magnetic metals, although it naturally extends to nonmagnetic (NM) conducting systems. The proposed scheme aims to reproduce the reference magnetization and achieves charge neutrality by construction, thus avoiding the large energy fluctuations and the postprocessing needed to correct the energies. It shows the most robust convergence of total energy and magnetism to the thermodynamic limit (TDL) when compared to four other TA schemes. Diffusion Monte Carlo applications are shown on NM Al and ferromagnetic α-Fe. The cohesive energy of Al in the TDL shows an excellent agreement with the experimental result. Furthermore, the magnetic moments in α-Fe exhibit rapid convergence with an increasing number of twists.

Twisted pair transmission line coil – a flexible, self-decoupled and robust element for 7 T MRI

ObjectiveThis study evaluates the performance of a twisted pair transmission line coil as a transceive element for 7 T MRI in terms of physical flexibility, robustness to shape deformations, and interelement decoupling. MethodsEach coil element was created by shaping a twisted pair of wires into a circle. One wire was interrupted at the top, while the other was interrupted at the bottom, and connected to the matching circuit. Electromagnetic simulations were conducted to determine the optimal number of twists per length (in terms of B₁+ field efficiency, SAR efficiency, sensitivity to elongation, and interelement decoupling properties) and for investigating the fundamental operational principle of the coil through fields streamline visualisation. A comparison between the twisted pair coil and a conventional loop coil in terms of B₁+ fields, maxSAR₁₀g, and stability of S₁₁ when the coil was deformed was performed. Experimentally measured interelement coupling between individual elements of multichannel arrays was also investigated. ResultsIncreasing the number of twists per length resulted in a more physically robust coil. Poynting vector streamline visualisation showed that the twisted pair coil concentrated most of the energy in the near field. The twisted pair coil exhibited comparable B₁+ fields and improved maxSAR₁₀g to the conventional coil but demonstrated exceptional stability with respect to coil deformation and a strong self-decoupling nature when placed in an array configuration. DiscussionThe findings highlight the robustness of the twisted pair coil, showcasing its stability under shape variations. This coil holds great potential as a flexible RF coil for various imaging applications using multiple-element arrays, benefiting from its inherent decoupling.

A Postmodern Twist to the Western Film Tradition in The Ballad of Buster Scruggs by The Coen Brothers

Although the Coen brothers had already made films related to the Western genre, The Ballad of Buster Scruggs (2018) is a different venture, since they wrote the script of this anthology movie comprising six stories themselves. Besides delving into some of the themes that they have dealt with in their filmography–mortality, ethics, violence, justice, etc.–they also provide the film with a number of postmodern twists that hint at an effort to work through some of the problems posed by the mythology of the American West. The Ballad of Buster Scruggs contains the use of intertextuality across various art forms, a parodic treatment, and the inclusion of unusual perspectives that are all typical of postmodern aesthetics and politics of representation.

Ni-P Electroless Plating of Polyethylene Terephthalate Fibers with Various Twist Number Utilizing Supercritical CO2-Assisted Catalyzation

Weavable devices are multifunctional fabric-based devices prepared by weaving various functional fibers into a single piece of fabric. Metalized polymer fibers are promising electrical conductors for such weavable devices because of the decnet electrical conductivity derived from the metal coating and flexibility arising from the polymer fiber. However, ensuring both sufficient electrical conductivity and stability in these metalized polymer fibers for practical device application remains challenging because of the insufficent adhesion between the metal coating and polymer fiber. An electroless plating with the catalyzation step performed in supercritical carbon dioxide (sc-CO2)1 is developed to produce metallized polymers possessing high electrical conductivity and good adhesive properties between the metal coating and polymer fiber. In application, fibers are often twisted to enhance a specific property, such as the mechanical property, and the twist number (twist per meter, T/m) is expected to affect the electroless plating performance.In this presentation, Ni-P electroless plating of polyethylene terephthalate (PET) fibers with a different twist number (twist per meter, T/m) is reported. The sc-CO2-assisted catalyzation was utilized to achieve electroless plating of Ni-P coatings on the PET fibers. The electrical resistance of the Ni-P/PET fibers was decreased following an increase in the twist number as listed in Table 1. Elemental analyses revealed that the Ni content in the Ni-P coating was higher for the PET fibers with a larger twist number. This tendency corresponded well the the electrical resistance results since Ni-P with a higher Ni content is expected to have a lower electrical resistance. Results obtained in this study indicate that PET fibers with a larger twist number is beneficial for the electroless Ni-P plating by decreasing of the electrical resistance in the fabricated Ni-P/PET fibers. Reference T.-F.M. Chang et al., Microelectron. Eng. 2020, 223, 111233. Figure 1

Entropy generation analysis on heat transfer characteristics of Twisted corrugated spiral heat exchanger utilized in solar pond

In the present study, heat transfer and entropy generation in the spiral corrugated heat exchanger used in the solar pond have been numerically studied. The thermal boundary condition of the third type has been selected for simulation and different geometric parameters have been studied to improve heat transfer and reduce entropy generation. New correlations based on experimental data have been used to validate the simulation. The results were obtained by changing the parameters such as the number of corrugations, the twist number of the corrugations, and the change of the Reynolds number. Also, dimensionless parameters have been defined to investigate the increase of heat transfer and decrease of entropy generation based on the first and second laws of thermodynamics, and finally, the optimal geometries have been introduced by the NH multi-criteria parameter. The simulation results showed that the corrugation creation on the tube will increase heat transfer and decrease entropy generation. Therefore, it was found that the twist number of the corrugation has a greater effect than the number of corrugations. In the best case, when the number of corrugations and their twist is high, the heat transfer improvement number (NH) can grow up to 89%, which will decrease with the increase of Reynolds number.

Simulation of performance enhancement of heat exchanger with twisted tapes using ANSYS software

Heat transfer effectiveness in a heat exchanger depends on the fluid flow through the exchanger. The heat transfer coefficient is directly proportional to the Nusselt number of the fluid flow. A higher Nusselt number indicates a greater heat transfer rate. The enhancement of heat transfer quality can be achieved by increasing the surface area for heat transfer, disrupting the boundary layer, and inducing swirl flow in the fluid. Twisted tape inserts are used in the heat exchanger to induce swirl flow. In this simulation, six types of inserts with a length of 2000 mm, width of 35 mm, and twist ratios of 2.5, 5.0, 7.5, 10, 12.5, and 15 were used. The mass flow rates of the fluid used were 0.4 kg/s, 0.6 kg/s, and 0.8 kg/s. The simulation was conducted using the ANSYS software with the Computational Fluid Dynamics (CFD) subprogram. The simulation results showed different flow patterns in each experiment. As the number of twists in the twisted tapes increased, the vortex flow in the fluid also increased. The highest performance was observed in the experiment using the twisted tape insert with 15 twists and a mass flow rate of 0.8 kg/s.

Quantum heat machines enabled by twisted geometry

In this paper, we analyze the operation of an Otto cycle heat machine driven by a non-interacting two-dimensional electron gas on a twisted geometry. We show that due to both the energy quantization on this structure and the adiabatic transformation of the number of complete twists per unit length of a helicoid, the machine performance in terms of output work, efficiency, and operation mode can be altered. We consider the deformations as in a spring, which is either compressed or stretched from its resting position. The realization of classically inconceivable Otto machines, with an incompressible sample, can be realized as well. The energy-level spacing of the system is the quantity that is being either compressed or stretched. These features are due to the existence of an effective geometry-induced quantum potential which is of pure quantum-mechanical origin.

Number of Tape Twists Effects on Solar Water Heater Performance

In solar applications, research into appropriate methods to improve the performance of the solar water heater is important. The current work studies improved the performance of the solar water heater by analyzing the effect of the number of added tape twists. A four-pipe solar water heater was built, and four twisted tapes were used, each with a different number of twists (flat, one, three, and five twists), and each tape was inserted into a pipe. The addition of twisted tapes has found that improved the performance of the solar water heater, and this improvement increased with the number of twists. A one, three, and five-twisted tapes achieved a temperature increase of (5.33, 14.09, and 20.27%) respectively, relative to a flat tape, and the instantaneous efficiency of the five twists tape was the highest, where the highest instantaneous efficiency of the four types rates (9.6, 13.4, 13.8, and 15 %) respectively.

Unprecedented sensing of the twist level in fiber tows, as shown for carbon fiber by inductance-based self-sensing, which provides fast, low-cost and large-format sensing

Twisting is commonly imposed on fiber tows to improve the processability, as needed for manufacturing composites and other products. Twist level (number of twists per unit length) determination commonly involves visual inspection. This work provides a method of sensing the twist level, as shown for carbon fiber tows up to 4 twists/inch. This method involves measuring the inductance (0.5–2.0 kHz), which increases monotonically with the twist level, due to Faraday's Law. The method is fast, low-cost, high-durability and large-format (scanning not needed). Uncoated and nickel-coated carbon fiber tows (PAN-based, 12K) give similar fractional increases in the inductance (≤46%) due to twisting. Magnetic character (as provided by nickel) is not required. A larger tow (24K) increases the inductance, but reduces the fractional increase due to twisting. Increasing the voltage enhances the inductance, but the fractional increase due to twisting is not affected. An increase in frequency also enhances the inductance, but the fractional change in inductance due to the twisting is diminished. The resistance decreases monotonically with the twist level (≤14% and ≤4% decrease for uncoated and nickel-coated carbon fibers, respectively), due to the increasing number of fiber-fiber contacts, which enable current detour when defects are encountered. Inductance-based sensing is superior in twist-level sensitivity to resistance-based sensing. Both sensitivities decrease monotonically with increasing twist level, with highest sensitivity below 1 twist/inch. The lowest twist level with demonstrated sensing is 0.1 twist/inch. This work also provides the first report of inductance-based structural self-sensing, which differs from the widely reported resistance-based structural self-sensing.