Equivalent Field Research Articles

Hydrothermal Numerical Simulation of Injection Operations at United Downs, Cornwall, UK

The United Downs Deep Geothermal Project (UDDGP) is designed to utilize a presumably permeable steep dipping fault damage zone (constituting the hydrothermal reservoir in a very low permeability granitic host rock) for fluid circulation and heat extraction between an injection well at 2.2 km depth (UD−2) and a production well at 5 km depth (UD−1). Soft hydraulic stimulation was performed to increase the permeability of the reservoir. Numerical simulations are performed to analyze the hydraulic stimulation results and evaluate the increase in permeability of the reservoir. Experimental and field data are used to characterize the initial reservoir static model. The reservoir is highly fractured, and two distinct fracture networks constitute the equivalent porous matrix and fault zone, respectively. Based on experimental and field data, stochastic discrete fracture networks (DFN) are developed to mimic the reservoir permeability behavior. Due to the large number of fractures involved in the stochastic model, equivalent permeability fields are calculated to create a model which is computationally feasible. Hydraulic test and stimulation data from UD−1 are used to modify the equivalent permeability field based on the observed difference between the real fractured reservoir and the stochastic DFN model. Additional hydraulic test and stimulation data from UD−2 are used to validate this modified permeability. Results reveal that the equivalent permeability field model derived from observations made in UD−1 is a good representation of the actual overall reservoir permeability, and it is useful for future studies. The numerical simulation results show the amount of permeability changes due to the soft hydraulic stimulation operation. Based on the validated permeability field, different flow rate scenarios of the petrothermal doublet and their respective pressure evolution are examined. Higher flow rates have a strong impact on the pressure evolution. Simulations are performed in the acidized enhanced permeability region to make a connection between the ongoing laboratory works on the acid injection and field response to the possible acidizing stimulation.

Interfacial voids and microstructure evolution, bonding behavior and deformation mechanism of TC4 diffusion bonded joints

The interfacial voids closure and related microstructure evaluation of diffusion bonding process was studied by the method of combining simulation and experiment on TC4 joints. It was found that the interfacial microvoids of joints transformed narrow oval to rounded circle with the increase of bonding time. Meanwhile, the distance of two adjacent interfacial microvoids increased, indicating the improvement of the bonded ratio. At the tip of microscopic convex region, the initial boundary was replaced by recrystallized grains. At the voids neck region, the initial bonding interfaces were replaced by straight grain boundary for the inadequate deformation, resulting from the incomplete driven force of recrystallization and grain boundary migration. The bonded interface developed from straight grain boundary to grains across the original interface. The evolution of Mises equivalent stress fields and the local strain fields of the interfacial region were by Finite Element Analysis (FEA) method. The results indicated that the stress at the asperity tip region was always higher than that at the neck of the void. The distribution of dislocations on the bonding interface region demonstrated that the grain boundary migration was controlled by the multiple slip of dislocations, which controlled by Power-Law Creep mechanism.

Magnetoacoustic waves controlled by in-plane uniaxial magnetic anisotropy

Controlling the magnetoacoustic wave transmission with various equivalent magnetic fields is a key technology for future hybrid surface acoustic wave (SAW) devices. In this work, we experimentally and theoretically display acoustically driven spin wave resonance in Ni films with in-plane uniaxial magnetic anisotropy at an arbitrary angle relative to the SAW vector. Our experimental results show that by adjusting the angle between the hard axis and the SAW vector, we achieve the excitation of magnetoacoustic waves in any in-plane orientation. Moreover, we clearly prove that the anisotropic effective field can be utilized to optimize the applied field configuration for driving magnetoacoustic waves and design orientation sensors due to the angle-sensitive performance of acoustic spin wave resonance.

Improvement of high-frequency magnetic properties in antiferromagnetic coupling trilayers by easy-plane magnetocrystalline anisotropy

Antiferromagnetic coupling ferromagnet/nonmagnet/ferromagnet structure trilayers with high resonance frequencies have been attracted much attention. However, their initial permeability is very low as the equivalent antiferromagnetic coupling field is an in-plane equivalent field. Therefore, how to improve the initial permeability and keep the high resonance frequencies is a worthy problem. In this work, an antiferromagnetic coupling Co82Ir18(35 nm)/Ru(0.35 nm)/Co82Ir18(35 nm) trilayer with easy-plane magnetocrystalline anisotropy was fabricated by direct current magnetron sputtering. The high-frequency magnetic properties and the tuning of optical mode ferromagnetic resonance in the trilayer were investigated using vector network analyzer with a shorted micro-strip method. The resonance frequency of the trilayer has a large increase (from 3.80 GHz to 8.16 GHz, the increment is 4.36 GHz) compared with the Co82Ir18(70 nm) single film due to the high-frequency optical mode resonance in the antiferromagnetic coupling ferromagnet/nonmagnet/ferromagnet structure. Moreover, through the introduction of easy-plane magnetocrystalline anisotropy, the calculated results reveal that initial permeability of our trilayer is the largest among other antiferromagnetic coupling Co-based trilayers without easy-plane magnetocrystalline anisotropy at the same resonance frequency (8.16 GHz), where the high-frequency magnetic properties of antiferromagnetic coupling trilayers are improved. Meanwhile, the tuning of optical mode ferromagnetic resonance reveals that the switch field about 161 Oe (about 1/2 of the single film) is observed which can switch the system from optical mode to acoustic mode. The results of this work indicate that it is effective to enhance the high-frequency magnetic properties of antiferromagnetic coupling trilayers by introducing the easy-plane magnetocrystalline anisotropy, which is a new method in improving the applied ability of antiferromagnetic coupling trilayers.

Suppression of Superconductivity in Heavy-ion Irradiated 2H-NbSe2 Caused by Negative Pressure

Effects of columnar defects created by 320 MeV Au irradiation on 2H-NbSe2 single crystals with a dose equivalent matching field up to 16 T were studied. Critical temperature is found to be suppressed almost linearly at a rate of 0.07 K/T. At the same time, the lattice parameters a and c are found to be expanded at rates of 0.016%/T and 0.030%/T, respectively. Such a lattice expansion should work as negative pressure to affect Tc. By separating the effect of heavy-ion irradiation on Tc suppression through lattice expansion and disorder, it is found that Tc is suppressed more by lattice expansion rather than by disorder.

Properties and Simulating Research of Epoxy Resin/Micron-SiC/Nano-SiO2 Composite

The dielectric behavior of insulations is a key factor affecting the development of anti-corona materials for generators. Epoxy resin (EP), as the matrix, is blended with inorganic fillers of micron SiC and nano SiO2 to investigate the effect of micro and nano doping on the conductivity and breakdown mechanism of the composites. Using experimental and simulation analysis, it is found that the effect of nano-SiO2 doping concentration on the conductivity is related to the dispersion of SiC particles. The lower concentration of SiO2 could decrease the conductivity of the composites. The conductivity increases with raising the nano-SiO2 doping concentration to a critical value. Meanwhile, the breakdown field strength of the composites decreases with the rising content of SiC in constant SiO2 and increases with more SiO2 when mixed with invariable SiC. When an equivalent electric field is applied to the samples, the electric field at the interface of micron particles is much stronger than the average field of the dielectric, close to the critical electric field of the tunneling effect. The density of the homopolar space charge bound to the surface of the stator bar elevates as the concentration of filled nanoparticles increases, by which a more effective Coulomb potential shield can be built to inhibit the further injection of carriers from the electrode to the interior of the anti-corona layer, thus reducing the space charge accumulation in the anti-corona layer as well as increasing the breakdown field strength of the dielectric.

Comparison of single-phase Newtonian and non-Newtonian nanofluid and two-phase models for convective heat transfer of nanofluid flow in backward-facing step

The aim is to investigate the application of nanofluids for improving the heat transfer in a backward-facing step channel. Numerical simulations are performed using single-phase models for both Newtonian and non-Newtonian fluids in the Reynolds number range 280–470. Constant and temperature-dependent thermo-physical properties of different volume fractions (0–4%) of nanoparticles are considered. The thermal enhancement of the nanofluids within the channel is analyzed and compared with the experimental data. A detailed comparison of different CFD models is established. Numerical results are obtained with two types of single-phase models (Newtonian and non-Newtonian) and three types of two-phase models (mixture, volume of fluid (VOF), Eulerian) and compared with experimental results obtained for the Nusselt number. The finite volume method is used to solve the system of governing partial differential equations describing the steady-state, two-dimensional, laminar, mixed convective flow in a micro backward facing step channel with uniform heat flux. The single-phase and two-phase models predict practically equivalent hydrodynamic fields, but significantly different thermal fields are observed in our results. The performance efficiency coefficient (PEC) is determined using single-phase and two-phase methods for Al2O3-water nanofluids at different Reynolds numbers to investigate their thermal performance.

Arithmetically equivalent fields in a Galois extension with Frobenius Galois group of 2-power degree

AbstractLet $F_{2^n}$ be the Frobenius group of degree $2^n$ and of order $2^n ( 2^n-1)$ with $n \ge 4$ . We show that if $K/\mathbb {Q} $ is a Galois extension whose Galois group is isomorphic to $F_{2^n}$ , then there are $\dfrac {2^{n-1} +(-1)^n }{3}$ intermediate fields of $K/\mathbb {Q} $ of degree $4 (2^n-1)$ such that they are not conjugate over $\mathbb {Q}$ but arithmetically equivalent over $\mathbb {Q}$ . We also give an explicit method to construct these arithmetically equivalent fields.

Semi-Active Controllable Stiffness Engine Mount Utilizing Natural Rubber-Based Magnetorheological Elastomers

This study proposes the design and fabrication of a natural rubber-based magnetorheological elastomer (NR-MRE) engine mount as a new device in absorbing the vibration originated from the automotive engine. The conceptual design was performed through a simulation process by Finite Element Method Magnetics to analyze the magnetic field distribution. The simulation result had indicated that the device was capable of generating an equivalent magnetic field density of 0.31 T at the effective area. The MRE was prepared by utilizing 60 wt% of carbonyl iron particles (CIPs), and the cavity was filled by compression molding. The MRE compound was tested based on its basic mechanical properties, while the MRE engine mounts were tested under a static compression load at off- and on-state conditions. It was observed that the compound possessed a good tensile strength for a load bearer matrix with an average of 12.65 MPa. Subsequently, the results of the static compression load had showed that the MRE engine mounts recorded an increase of 12% in the force generated as compared to conventional engine mounts at an off-state condition. Meanwhile, at an on-state condition of 2.4 A, the MRE engine mounts recorded an increase in the force generated with 106%. The study has demonstrated that the proposed device can be one of the potential candidates for vibration control applications due to its stiffness controllability.

Validity of equivalent square field concept in small field dosimetry.

The equivalent square (ES) concept has been used for traditional radiation fields defined by the machine collimating system. For small fields, the concept Sclin was introduced based on measuring dosimetric field width (full-width half maximum, FWHM) of the cardinal axis of the beam profiles. The pros and cons of this concept are evaluated in small fields and compared with the traditional ES using area and perimeter (4A/P) method based on geometric field size settings, for example, light field settings. One hundred thirty-seven square and rectangular fields from 5-50mm with every possible permutation (keeping one jaw fixed and varying other jaw from 5 to 50 mm) were utilized to measure FWHM for the validation of Sclin . Using a microSilicon detector and a scanning water tank, measurements were performed on an Elekta (Versa) machine with Agility head and a Varian TrueBeam with different MLC/Jaw design to evaluate the Sclin concept and to understand the effect of exchange factor in small fields. Field output factors were also measured for all 137 fields. The data fitting for fields ranging from 5-50mm between the traditional 4A/P method and Sclin shows differences and indicates a linear relationship with distinct separation of slope for Elekta and Varian machines. ForElekta Agility machine ES based on 4A/P<Sclin and for the VarianTrueBeam 4A/P>Sclin for square fields. Our measured data show that both methods are equally valid but does vary by the machine design. The field output factor is dependent on the elongation factor as well as machine design. For fields with sides ≥10mm, the exchange factor is nearly identical in both machines with magnitude up to 4%, which is close to measurement uncertainty (±3%), but for small fields (<10mm), the Elekta machine has higher exchange factors compared to the Varian machine. The results demonstrate that the two concepts for defining equivalent field (Sclin and 4A/P) are equivalent and can be directly related through an empirical equation. This study confirms that 4A/P is still valid for small fields except for very small fields (≤10mm) where source occlusion is a dominating factor. The Sclin method is potentially sensitive to measurement uncertainty due to measurement of FWHM which is machine-, detector- and user-dependent, while the 4A/P method relies mainly on geometry of the machine and has less dependency on type of machine, detector, and user. The exchange factors are comparable for both types of machines. The conclusion is based on data from an Elekta with Agility head and a Varian TrueBeam machine that may have potential for bias due to light field/collimator set up and alignment. Care should be taken in extrapolating these data to any other machine.

Development of Bunching System for High Intensity Cyclotron at CIAE

ABSTRACT A new double-gap buncher is designed for the CYCIAE-10 cyclotron in order to get the high-intensity proton beam with the order of mA. RF simulation is carefully performed to achieve a deep quantitative analysis of the equivalent capacitance and electrical field distribution. Uniform electrical field technology is verified by EM field simulation to get an electrical field uniformity of 94.67%. Type L matching circuit is used to transfer the loading reactance to 50 Ohms. Variable vacuum capacitor with 5–50 pF is selected for its small power loss and the convenience of commissioning. Dynamic calculation of the buncher and mechanical design are also presented in this paper. The open-loop bench test shows that 370 Vpeak RF voltage is established in the central electrode with power consumption of 37 W. Alternative redesign and online test are carried out, and more than 1 mA H− beams are achieved on the inner target, which verify the buncher design.

A new leaky wave antenna using wire‐loaded metagratings: The theoretical analysis and implementation

SummaryA new leaky wave antenna (LWA) based on wire‐loaded metagratings (MGs) is proposed, with the capability of successfully employing MGs for leaky modes. Periodic capacitive‐wired and inductive‐wired MGs are located on a dielectric substrate in the LWA framework and backed by a perfect electric conductor (PEC) layer. These MGs are partial radial surfaces to radiate energy using equivalent surface impedance with a local value of the complex wavenumber. A theoretical analysis has created a model for the equivalent electromagnetic fields produced via loaded‐wire MGs and generated the Z‐matrix and S‐matrix for a two‐port structure from the electromagnetic fields. As a result, a beam‐scanning range of 53° for the operating bandwidth of 9.9–11.9 GHz is achieved with a scanning sensitivity of 26.5°/GHz. Meanwhile, the realized gain is obtained up to 12.9 dB. The measurement and simulation results indicated that the MGs LWA was consistent. The proposed antenna performed admirably in beam‐steering communication systems.

Larmor rotation in galaxies

The role of the gravitomagnetic field in the rotation of galaxies is clarified. Larmor’s theorem simplifies the analysis of different galactic equilibrium solutions. In particular, the self-consistent solution, which takes into account both the equivalent Larmor gravitomagnetic field and fluid convection, recovers previous results that reproduce galactic rotation curves without recourse to dark matter.

Optimization of Pixel Size and Electrode Structure for Ge:Ga Terahertz Photoconductive Detectors.

To investigate the effects of the pixel sizes and the electrode structures on the performance of Ge-based terahertz (THz) photoconductive detectors, vertical structure Ge:Ga detectors with different structure parameters were fabricated. The characteristics of the detectors were investigated at 4.2 K, including the spectral response, blackbody response (Rbb), dark current density-voltage characters, and noise equivalent power (NEP). The detector with the pixel radius of 400 μm and the top electrode of the ring structure showed the best performance. The spectral response band of this detector was about 20–180 μm. The Rbb of this detector reached as high as 0.92 A/W, and the NEP reached 5.4 × 10−13 W/ at 0.5 V. Compared with the detector with a pixel radius of 1000 μm and the top electrode of the spot structure, the Rbb increased nearly six times, and the NEP decreased nearly 12 times. This is due to the fact that the optimized parameters increased the equivalent electric field of the detector. This work provides a route for future research into large-scale array Ge-based THz detectors.

The Use of an Equivalent Temperature Field to Emulate an Induced Residual Stress Field in a Rotating Disk Due to Full Or Partial Rotational Autofrettage

Abstract The evaluation of equivalent temperature fields for cylindrical and spherical pressure vessels to imitate autofrettage induced residual stresses has been successfully implemented in studying crack growth in autofrettaged vessels by the finite element method. Rotational autofrettage is a recent method that can be employed for strengthening hollow disks used in many turbomachinery. The evaluation of the equivalent temperature field becomes pivotal in the performance assessment of autofrettaged cracked disks subjected to high rotational speed. In this work, an equivalent thermal loading method for emulating the residual stress field in a hollow rotating disk, induced by full or partial rotational autofrettage in a finite element analysis is suggested. An analytical, or a numerical discrete solution, evaluating the equivalent temperature field for an arbitrary axisymmetric residual stress field, induced in a rotating disk due to rotational autofrettage, is developed. This solution is implemented in a finite element analysis to emulate the original rotational autofrettage induced residual stresses in a typical rotating disk. Applying the equivalent temperature field, the residual stresses obtained in the finite element analysis, are further corroborated with the original residual stress field introduced by rotational autofrettage. It is found that the developed equivalent temperature fields excellently reproduce the residual stress fields, within less than 1%, induced by both full or partial rotational autofrettage.

Dynamics of magnetic skyrmions under temperature gradients

We expand the Zhang–Li spin-transfer torque [Phys. Rev. Lett. 93, 127204 (2004)] to finite temperatures by the scattering amplitude. Considering various factors, including the adiabatic and diabatic effects of electrons and magnons, entropy equivalent field, thermal dipole field, thermal activation, magnetic-anisotropy gradient, and diffusion, we answer a recent question both experimentally and theoretically controversial: Will skyrmions move to the hot or cold region under thermal gradients?

A nonlinear magneto-elastoplastic coupling model based on Jiles–Atherton theory of ferromagnetic materials

As seen in the Jiles–Atherton (J–A) model and its modified form, the linear relationship between the magnetization coefficient and the stress deviates significantly from the experimental results. It is necessary to introduce many parameters that are difficult to obtain or unknown to describe the effect of elastoplastic deformation on magnetization or hysteresis, such as shape coefficient, pinning coefficient, and molecular field coefficient. In this paper, a new nonlinear magneto-elastoplastic model for ferromagnetic materials is established based on the magneto-mechanical coupling effect, and both the sixth-order term of magnetization and the nonlinear equation of the magnetization coefficient are introduced into the magnetostriction equation. In the models established in this paper, the elastoplastic deformation equivalent magnetic field is introduced into the effective magnetic field, and the Frohlich–Kennelly equation is used to describe the anhysteretic magnetization. After comparing the prediction results of different models with the available experimental results, it is observed that the proposed model in this paper exhibits superior prediction ability for magnetostrictive strain, magnetization, and hysteresis phenomena under different stresses. This paper has also analyzed the mechanism of the effect of elasto-plastic loading and residual stress on the hysteresis in different models as well as the differences between them. The determination coefficient of the proposed model in this paper is closer to 1, which is better than the existing models, indicating that it has a better fitting effect and is of great significance to the development of quantitative non-destructive testing technology.

Designing an ultra-thin and wideband low-frequency absorber based on lumped resistance.

Traditional absorbers are mostly limited by their large size and high profile, which renders them unfavorable for practical devices. To solve this problem, we design and test an ultra-thin metamaterial absorber (UTMA). The top layer of the metamaterial absorber is designed as a patterned combination of split ring and metal strips, so that its resonant frequency point is in the target low frequency. Meanwhile, ohmic loss is enhanced by loading lumped resistance in the gap of the meta-surface to improve the absorb efficiency (> 90%) and to expand the working bandwidth (1.24-3.14 GHz). Moreover, the total thickness of the absorber is 9 mm (0.037λwith respect to the lowest operating frequency). The working mechanism of UTMA is analyzed based on the equivalent media theory, surface current and electric field energy distribution. The experimental results are in good agreement with the simulation, which verifies the feasibility of the design. In this work, the metamaterial absorber is designed to meet the target requirements from three performance indexes: low frequency, ultra-thin, and wideband, leading to the prospect of broad applications in the military and civil fields.

Fivefold Helically Corrugated Waveguide for High-Power W-Band Gyro-Devices and Pulse Compression

The design, simulation, manufacture, and measurement of a W-band fivefold (5F) helically corrugated waveguide (HCW) is reported. The 5F HCW is based on the coupling of the traveling TE₃₁ and near cutoff TE₂₁ modes to create an operating eigenwave. The fabricated test structure has circular waveguide ports and features elliptical polarizer sections and broadband TE₁₁ to TE₃₁ mode converters on either side of the 5F HCW. The optimized mode converter design, based on a fourfold (4F) HCW, has a predicted power conversion efficiency greater than 90% from 89 to 102.5 GHz, and 96% peak efficiency at 94 GHz. The optimization of the 5F HCW geometry produced an eigenwave suitable for gyro-devices, but the optimization could equally well have been directed to applications such as pulse compression and microwave undulators. Analysis of simulated electric field profiles showed that the propagating power in the 5F HCW was increased by a factor of 6 over that in the 3F HCW at equivalent peak electric field strength. This is due to the larger diameter of the waveguide. Test structures were manufactured through a combination of precision machining of a sacrificial mandrel, copper growth by electroforming followed by removal of the aluminum mandrel by chemically etching. Measurements of the 5F HCW structure's dispersion showed excellent agreement with the prediction over the design range of 90-98 GHz.

Return to Play and Player Performance After Meniscal Tear Among Elite-Level European Soccer Players: A Matched Cohort Analysis of Injuries From 2006 to 2016.

Background:Meniscal injuries are extremely common in soccer athletes, and little is known about postrecovery performance.Purpose:To (1) identify characteristics associated with return to play (RTP) to the same league level and (2) evaluate long-term effects that injury and management approach may have on player performance.Study Design:Cohort study; Level of evidence, 3.Methods:Using publicly available records, we identified athletes who sustained meniscal tears across the 5 major European soccer leagues (English Premier League, Bundesliga, La Liga, Ligue 1, and Serie A) between 2006 and 2016. Injured athletes were matched to controls 1:2 by demographics and performance. Investigations included rate of RTP to the same league level, reinjury, player characteristics associated with RTP within 2 seasons, long-term availability, field time, and performance metrics standardized to 90 minutes of play during the next 4 seasons.Results:A total of 250 players sustaining meniscal tears were included, of which 106 (42%) received surgical management. Median absence was 57.5 days (interquartile range [IQR], 35-92) or 7 games (IQR, 4-12). Rate of RTP was 70%, and the reinjury rate 5% if a player could RTP. Age greater than 30 years was a negative predictor for RTP (odds ratio [OR], 0.62; P = .002), whereas higher preinjury goals per game (OR, 2.80; P = .04) and surgical management (OR, 1.38; P = .002) were positive predictors for RTP. Surgical management was associated with higher long-term availability (P < .01). As compared with the control, there were no significant differences in field time or performance metrics after RTP, either overall or by player position. As compared with nonoperative management, defenders undergoing surgery demonstrated decreased field time. Attackers and midfielders demonstrated similar field time and performance regardless of management.Conclusion:RTP of elite soccer athletes sustaining meniscal tear is contingent on age, preinjury performance, and management approach. Those who RTP to the same league level can be expected to demonstrate equivalent field time, performance, and long-term availability as noninjured athletes.