Stretchable Textile Yarn Based on UHF RFID Helical Tag

In the context of wearable technology, several techniques have been used for the fabrication of radio frequency identification (RFID) tags such as 3D printing, inkjet printing, and even embroidery. In contrast to these methods where the tag is attached to the object by using sewing or simple sticking, the E-Thread® technology is a novel assembling method allowing for the integration of the RFID tag into a textile yarn and thus makes it embeddable into the object at the fabrication stage. The current E-Thread® yarn uses a RFID tag in which the antenna is a straight half-wave dipole that makes the solution vulnerable to mechanical strains (i.e., elongation). In this paper, we propose an alternative to the current RFID yarn solution with the use of an antenna having a helical geometry that answers to the mechanical issues and keeps quite similar electrical and radiative properties with respect to the present solution. The RFID helical tag was designed and simulated taking into consideration the constraints of the manufacturing process. The helical RFID tag was then fabricated using the E-Thread® technology and experimental characterization showed that the obtained structure exhibited good performance with 10.6 m of read range in the ultra high frequency (UHF) RFID band and 10% of tolerance in terms of elongation.

AC losses of Roebel and CORC® cables at higher AC magnetic fields and Ramp Rates

We have measured ReBCO coated conductor-based CORC® and Roebel cables at 77 K in a Spinning Magnet Calorimeter which subjected the tapes in the samples to a radial magnetic field of 566 mT (peak) at frequencies up to 120 Hz (272 T/s, cyclic average) with an approximately sinusoidal waveform. The samples were oriented such that the field applied to the tapes within the cables was entirely radial, simplifying subsequent analysis. An expression for loss which included hysteretic, flux creep, and eddy current losses was fit to both the CORC® and the Roebel cables. This expression allowed easy comparison of the relative influence of eddy currents and flux creep (or power-law behavior) effects. The loss of both the CORC® and Roebel cables measured here were seen to be essentially the sum of the hysteretic loss, flux creep effects, and the normal metal eddy current losses of the individual tapes. The losses of these cables were measured at high B*dB/dt with no coupling current loss observed under the present preparation conditions. The influence of flux creep effects on loss were not negligible. The losses of the CORC® cable per meter of tape were seen to be reduced from the case of a flat tape because of the helical geometry of the tapes.

Experimental investigation of a rotor blade tip vortex pair

This paper presents the results of an experimental study of two closely spaced vortices generated by a rotating blade with a modified tip geometry. The experiments are carried out in two water channel facilities and involve a generic one-bladed rotor operating in a regime near hover. It is equipped with a parametric fin placed perpendicular to the pressure surface near the tip, which generates a co-rotating vortex pair having a helical geometry. Based on previous results obtained with a fixed wing, a series of small-scale experiments is first carried out, to validate the method of vortex pair generation also for a rotating blade, and to obtain a qualitative overview of its evolution going downstream. A more detailed quantitative study is then performed in a larger facility at three times the initial scale. By varying the fin parameters, it was possible to obtain a configuration in which the two vortices have almost the same circulation. In both experiments, the vortex pair is found to merge into a single helical wake vortex within one blade rotation. Particle image velocimetry measurements show that the resulting vortex has a significantly larger core radius than the single tip vortex from a blade without fin. This finding may have relevance in the context of blade–vortex interactions, where noise generation and fatigue from fluid–structure interactions depend strongly on the vortex core size.

Optimisation of helical geometry of inspection probe for steam generator tubes of the PFBR

The steam generator (SG) tubes of the prototype fast breeder reactor (PFBR) located in Kalpakkam, India, need to be periodically inspected using the remote field eddy current (RFEC) technique. During the pre-service inspection of the SG tubes, it was found that the RFEC probes experienced frequent mechanical breakages. To avoid these failures, changes in the existing structural design of the RFEC probe were required. A helical groove design was proposed to obtain a smooth transition in the variation of stress across the probe during the inspection. It was difficult to calculate the flexural stiffness of the proposed helical geometry probe due to the varying cross-section along its length. In this paper, the smearing approach adopted to calculate the stiffness of the RFEC probe and the sensitivity analysis carried out to determine the optimal design of the probe are discussed. A probe was fabricated based on the helical groove design and tested to qualify its suitability for the SG inspection. The RFEC probe with helical grooves was employed for the pre-service inspection of the SG tubes of the PFBR. More than 200 tubes have been inspected using the proposed design and no mechanical failure of the probe has been observed.

Helical Flow of Polymer Melts in Extruders : Model Development and Validation with Experiments

Operating and processing conditions as well as the selection of the screw design in injection molding industry are largely based on trial-and-error exercise, which is expensive and time consuming. A better approach is to develop mathematical models for prediction of the final process performance where the conditions and parameters of a process can be used as inputs in those models. However, most of the models developed and used so far contain unrealistic geometrical and mathematical simplifications. The objective of this work is to develop a steady-state three dimensional mathematical model to describe the flow of an incompressible polymer melt inside a helical geometry, which represents the polymer's true motion in extrusion and injection molding processes. In order to develop the model in helical geometry, where at least two axes are not perpendicular, the mathematical model is first developed in a natural system (i.e. cylindrical) and using transformation tools are then changed to the physical helical one. In this initiative, we develop an iterative computational alogrithm based on shooting Newton-Raphson method in order to simulate the process. The transformation matrices to adapt the equations of change form a natural system (i.e. orthogonal cylindrical systems) to a physical system (i.e. Helical coordinates) are also developed for velocity and derivative profiles. Subsequently the solution approach to solve the indirectly coupled equations of change is explained and the simulation results are compared with experimental data. The simulation results are vallidated against data obtained from ten different experiments with an industrial injection molding machine, processing two different polymers - high density polyethylene (HDPE) and poly ethylene terephthalate (PET). It is observed that the simulation results are in good agreement with experimental data. This outcome demonstrates the utility of the developed mathematical model and simulation approach. Important features of this work are the consideration of the linear backward motion of the screw leading to calculation of proper process shot size and the incorporation of the tapering screw designs with upward and downward sections in the direction of the flow into the model. Another important feature in the development of the mathematical model is that the rheological and physical properties of plastic resins are not constant and change as the melt temperature changes during the process. From the standpoint of industrial practice, the direct benefit of this work is the ability to effectively calculate adequate shot size, recovery rate, and various state variables throughout the extent of the machine.

Helical Flow of Polymer Melts in Extruders : Model Development and Validation with Experiments

Operating and processing conditions as well as the selection of the screw design in injection molding industry are largely based on trial-and-error exercise, which is expensive and time consuming. A better approach is to develop mathematical models for prediction of the final process performance where the conditions and parameters of a process can be used as inputs in those models. However, most of the models developed and used so far contain unrealistic geometrical and mathematical simplifications. The objective of this work is to develop a steady-state three dimensional mathematical model to describe the flow of an incompressible polymer melt inside a helical geometry, which represents the polymer's true motion in extrusion and injection molding processes. In order to develop the model in helical geometry, where at least two axes are not perpendicular, the mathematical model is first developed in a natural system (i.e. cylindrical) and using transformation tools are then changed to the physical helical one. In this initiative, we develop an iterative computational alogrithm based on shooting Newton-Raphson method in order to simulate the process. The transformation matrices to adapt the equations of change form a natural system (i.e. orthogonal cylindrical systems) to a physical system (i.e. Helical coordinates) are also developed for velocity and derivative profiles. Subsequently the solution approach to solve the indirectly coupled equations of change is explained and the simulation results are compared with experimental data. The simulation results are vallidated against data obtained from ten different experiments with an industrial injection molding machine, processing two different polymers - high density polyethylene (HDPE) and poly ethylene terephthalate (PET). It is observed that the simulation results are in good agreement with experimental data. This outcome demonstrates the utility of the developed mathematical model and simulation approach. Important features of this work are the consideration of the linear backward motion of the screw leading to calculation of proper process shot size and the incorporation of the tapering screw designs with upward and downward sections in the direction of the flow into the model. Another important feature in the development of the mathematical model is that the rheological and physical properties of plastic resins are not constant and change as the melt temperature changes during the process. From the standpoint of industrial practice, the direct benefit of this work is the ability to effectively calculate adequate shot size, recovery rate, and various state variables throughout the extent of the machine.

Challenges in Studying Steric Interactions in Highly Strained Perhalogenated Alkanes and Silanes.

The decomposition of the molecular total energy in their hyperconjugative, steric and electrostatic effects can lead to interesting interpretations about the stereoelectronic effects that govern their geometry and properties. In this work, we have studied homologous series of perfluoroalkanes, perchloroalkanes, perfluorosilanes and perchlorosilanes, and all molecules have preference for helical geometries. According to Natural Bond Orbitals (NBO) calculations, the silanes have their helical geometry stabilised by hyperconjugative interactions, as well as the perfluoroalkanes. However, it was surprisingly difficult to disclose that steric interactions are ruling the helical geometry preference in perchloroalkanes by comparing the NBO analysis and the Quantum Theory of Atoms ins Molecules (QTAIM). Although perchloroalkanes have extremely intense steric interactions between Cl lone pairs, some of them were underestimated by the NBO analysis, which showed the opposite behaviour compared with QTAIM that indicates steric effects as the leading forces to helical geometry preference.

Mechanically Induced Single-molecule Helicity Switching of Graphene-Nanoribbon-fused Helicene on Au(111)

Helicene is a functional material with chirality caused by its characteristic helical geometry. The inversion of its helicity by external stimuli is a challenging task in the advanced control of...

Structural variability of CG-rich DNA 18-mers accommodating double T–T mismatches

Solution and crystal data are reported for DNA 18-mers with sequences related to those of bacterial noncoding single-stranded DNA segments called repetitive extragenic palindromes (REPs). Solution CD and melting data showed that the CG-rich, near-palindromic REPs from various bacterial species exhibit dynamic temperature-dependent and concentration-dependent equilibria, including architectures compatible with not only hairpins, which are expected to be biologically relevant, but also antiparallel duplexes and bimolecular tetraplexes. Three 18-mer oligonucleotides named Hpar-18 (PDB entry 6rou), Chom-18 (PDB entry 6ros) and its brominated variant Chom-18Br (PDB entry 6ror) crystallized as isomorphic right-handed A-like duplexes. The low-resolution crystal structures were solved with the help of experimental phases for Chom-18Br. The center of the duplexes is formed by two successive T–T noncanonical base pairs (mismatches). They do not deform the double-helical geometry. The presence of T–T mismatches prompted an analysis of the geometries of these and other noncanonical pairs in other DNA crystals in terms of their fit to the experimental electron densities (RSCC) and their geometric fit to the NtC (dinucleotide conformational) classes (https://dnatco.datmos.org/). Throughout this work, knowledge of the NtC classes was used to refine and validate the crystal structures, and to analyze the mismatches.