Study on the winding quality for spiral HTS cable based on AI detection model

The development of high temperature superconducting (HTS) conductors is leading to the diverse structure designs of HTS cable. (RE)Ba2Cu3Ox (REBCO) tapes using spiral geometry has been a popular compact HTS cable structure, which is in the critical stage of engineering production and application. However, the winding quality of REBCO tapes is unstable for spiral HTS cables, because of the different winding methods like manual winding, device-assisted winding, or automatic winding. Although automatic winding will be the first choice for the actual applications by spiral HTS cables, the related winding quality is not monitored effectively yet. In this paper, we first discuss the possible influence of the winding quality on the critical current performance of spiral HTS cables. Then, an artificial intelligence (AI) based method is implemented to realize the detection model for the winding quality. From image data preparation to AI detection and postprocessing, the detection model provides the final results to show the winding intervals as a binary image. Through the intuitive analysis and the evaluation metrics, both error and correct winding conditions obtain acceptable detection results, and the correct one has a better performance. The identification of the winding intervals will help to determine the monitoring strategy for the spiral HTS cable fabrication.

Effective reduction of magnetisation losses in copper-plated multifilament coated conductors using spiral geometry

We wound copper-plated multifilament coated conductors spirally on a round core to decouple filaments electromagnetically under ac transverse magnetic fields and measured their magnetisation losses. Although the coated conductors were plated with copper, which connects all filaments electrically and allows current sharing among them, the spiral geometry decoupled filaments similar to the twist geometry, and the magnetisation loss was reduced effectively by the multifilament structure. The measured magnetisation loss of a 4 mm-wide, 10-filament coated conductor with a 20 μm-thick copper wound spirally on a 3 mm-core was only 7% of that of the same 10-filament coated conductor with a straight shape under an ac transverse magnetic field with an amplitude and frequency of 100 mT and 65.44 Hz, respectively. We separated the measured magnetisation losses into hysteresis and coupling losses and discussed the influence of filament width, copper thickness, and core diameter on both losses. We compared the hysteresis losses with the analytical values given by Brandt and Indenbom and compared the coupling losses with the values calculated using a general expression of coupling loss with the coupling time constants and geometry factors.

Numerical Study on the Impact of Spiral Tortuous Hole on Cuttings Removal in Horizontal Wells

Summary Horizontal wells are designed to have smooth (straight), curved, and lateral sections. However, the actual drilled path usually suffers from unwanted undulations from the planned well trajectory known as wellbore tortuosity. Wellbore tortuosity can slow the drilling penetration rate, aggravate drillstring vibration and buckling, complicate the casing and cement job, and lead to inaccurate wellbore position. This paper presents a validated computational fluid dynamics (CFD) model to investigate the impact of wellbore tortuosity on hole cleaning. The Eulerian-Eulerian approach is used to simulate solid-liquid laminar flow in annular geometry using polyhedral mesh. Then, the impact of wellbore tortuosity on cuttings accumulation, annular pressure loss, and fluid velocity was investigated and compared with the flow behavior in a straight horizontal well. A parametric analysis of spiral period length, spiral amplitude, drillstring rotation, flow rate, annular eccentricity, drilling rate of penetration (ROP), and cuttings size was conducted to assess their influence on cuttings transport in spiral tortuous holes and their relative magnitude to other design or operating factors. Simulation results show that polyhedral mesh is an optimum meshing technique for spiral profile geometry. Wellbore tortuosity aggravates hole cleaning in lateral sections based on the length of the spiral period and/or the spiral amplitude. Reduction in cuttings velocity was observed in the top part of the spiral geometry (crest), causing large deposition of cuttings in this area compared to the spiral lower part (trough). Drillstring rotation from 0 to 200 rev/min is the critical range for efficient hole cleaning in spiral geometry. Cuttings size can improve cuttings accumulation if the particle size is larger than the viscous layer located near the bed velocity profile. The drilling ROP and annular eccentricity aggravate cuttings accumulation and bed deposition in a spiral hole, similar to what is normally observed in straight horizontal wells.

Spiral sound-diffusing metasurfaces based on holographic vortices

In this work, we show that scattered acoustic vortices generated by metasurfaces with chiral symmetry present broadband unusual properties in the far-field. These metasurfaces are designed to encode the holographic field of an acoustical vortex, resulting in structures with spiral geometry. In the near field, phase dislocations with tuned topological charge emerge when the scattered waves interference destructively along the axis of the spiral metasurface. In the far field, metasurfaces based on holographic vortices inhibit specular reflections because all scattered waves also interfere destructively in the normal direction. In addition, the scattering function in the far field is unusually uniform because the reflected waves diverge spherically from the holographic focal point. In this way, by triggering vorticity, energy can be evenly reflected in all directions except to the normal. As a consequence, the designed metasurface presents a mean correlation-scattering coefficient of 0.99 (0.98 in experiments) and a mean normalized diffusion coefficient of 0.73 (0.76 in experiments) over a 4 octave frequency band. The singular features of the resulting metasurfaces with chiral geometry allow the simultaneous generation of broadband, diffuse and non-specular scattering. These three exceptional features make spiral metasurfaces extraordinary candidates for controlling acoustic scattering and generating diffuse sound reflections in several applications and branches of wave physics as underwater acoustics, biomedical ultrasound, particle manipulation devices or room acoustics.

The formation and evolution of the electron strahl in the inner heliosphere

<p>The electrons in the solar wind exhibit an interesting kinetic substructure with many important implications for the overall energetics of the plasma in the heliosphere. We are especially interested in the formation and evolution of the electron strahl, a field-aligned beam of superthermal electrons, in the heliosphere. We develop a kinetic transport equation for typical heliospheric conditions based on a Parker-spiral geometry of the magnetic field. We present the results of our theoretical model for the radial evolution of the electron velocity distribution function (VDF) in the solar wind. We study the effects of the adiabatic focusing of energetic electrons, wave-particle interactions, and Coulomb collisions through a generalized kinetic equation for the electron VDF. We compare and contrast our results with the observed effects in the electron VDFs from space missions that explore the radial evolution of electrons in the inner heliosphere such as Helios, Parker Solar Probe, and Solar Orbiter.</p>

Design of a compact high gain printed octagonal array of spiral-based fractal antennas for DBS application

This paper presents a compact octagonal array of microstrip patch antennas for direct broadcast satellite (DBS) (12.2–12.7 GHz) services. The proposed single element of this array is a new fractal antenna, having considerably high gain and can heavily suppress cross polarization along the main beam direction. The single element is derived from a 2D spiral geometry. The corporate feed network of the array is designed in such a manner to make the structure very compact. The fabricated single element resonates at 12.51 GHz and gives a gain and bandwidth of 9.32 dBi and 280 MHz, respectively. The array resonates at 12.46 GHz and gives gain of 17.67 dBi and a bandwidth of 506 MHz, which ensures a 100% coverage of the entire DBS service band. The measured cross polarization of single element and array along the direction of main beam are −45.50 and −43.35 dB, respectively. Both the single element as well as the array maintains a reasonably good radiation efficiency of 86.70 and 82.20%, respectively.

Sensitivity Enhancement of Acetone Gas Sensor using Polyethylene Glycol/Multi-Walled Carbon Nanotubes Composite Sensing Film with Thermal Treatment

There is a need to develop a chemiresistive gas sensor equipped with a thermostat over a wide area for the sensor, which can protect the sensor from the influence of ambient temperature due to the uniform temperature of the thermostat. In this paper, we demonstrated an acetone gas sensor based on a polyethylene glycol (PEG)/Multi-walled Carbon Nanotubes (MWCNTs) composite film, which was equipped with a thermostat. The sensor was operated at modest working temperatures for sensor sensitivity enhancement. The optimum design of the polyimide-based thermostat with widely uniform thermal distribution was investigated in detail. It was found that the temperature uniformity of the thermostat was achieved using double spiral geometry. The experimental results of the sensor response showed that the PEG/MWCNTs composite film with a moderate working temperature revealed a higher sensitivity than that without thermal treatment. Moreover, the sensing mechanisms of the PEG/MWCNTs composite gas sensor to acetone vapor were studied as well.

Low-Frequency Piezoelectric Accelerometer Array for Fully Implantable Cochlear Implants

We demonstrate a low-volume, stress-free, piezoelectric micro-electromechanical system (MEMS) cantilever array for fully implantable hearing aids. The 12-element spiral-matrix is sensitive to the lower part of audible frequency range (300–700 Hz) through the proper resonant frequency of the individual spirals tuned by dimensions of the cantilevers. The obtained high Q-factors (117–254) provide high frequency selectivity. The generated open circuit voltage signals could be sufficient for the direct analog conversion of the signals for cochlear multielectrode implants. By comparing different geometries we have also demonstrated that the initial stress, which is derived from silicon-dioxide (SiO2) and aluminum-nitride (AlN) layers, could be drastically reduced simply by the spiral geometry. The results of vibration measurements have shown a good agreement with the calculated resonant frequencies.

Analytical modelling of spiral cantilever structure for vibration energy harvesting applications

Research on harvesting energy from natural resources is more focused as it can make microelectronic devices self-powered. MEMS based vibration energy harvesters are gaining its popularity in recent days to extract energy from vibrating objects and to use that energy to power the sensors. A solution for the major constrain for vibration energy harvesting in micro scale has been addressed in this paper. Cantilever beams coated with piezoelectric materials which are optimized to resonate at the source vibration frequency are used in most of the traditional vibration energy harvesting applications. In micro scale such structures have very high natural frequency compared to the ambient vibration frequencies due to which frequency matching is a constrain. Tip mass at the end of the cantilever reduces the resonant frequency to a great extent but adds to complexity and fabrication difficulties. Here, we propose a spiral geometry for micro harvester structures with low fundamental frequencies compared to traditional cantilevers. The spiral geometry is proposed, simulated and analyzed, to show that such a structure would be able to vibrate near resonance at micro scale. The analysis consists of Modal analysis, Mises stress analysis and displacement analysis in COMSOL Multiphysics. The result shows that the frequency has been reduced by a factor of 300 when compared to normal cantilever in the same volume. The work provides guideline for vibration energy harvesting structure design for an improved performance.