Weak Injection Research Articles

Bimerons create bimerons: Proliferation and aggregation induced by currents and magnetic fields

AbstractThe aggregation of topological spin textures at nano and micro scales has practical applications in spintronic technologies. Here, the authors report the in‐plane current‐induced proliferation and aggregation of bimerons in a bulk chiral magnet. It is found that the spin‐transfer torques can induce the proliferation and aggregation of bimerons only in the presence of an appropriate out‐of‐plane magnetic field. It is also found that a relatively small damping and a relatively large non‐adiabatic spin‐transfer torque could lead to more pronounced bimeron proliferation and aggregation. Particularly, the current density should be larger than a certain threshold in order to trigger the proliferation; namely, the bimerons may only be driven into translational motion under weak current injection. Besides, the authors find that the aggregate bimerons could relax into a deformed honeycomb bimeron lattice with a few lattice structure defects after the current injection. The results are promising for the development of bio‐inspired spintronic devices that use a large number of aggregate bimerons. The findings also provide a platform for studying aggregation‐induced effects in spintronic systems, such as the aggregation‐induced lattice phase transitions.

The analytical solutions of squeezing flow and heat transfer in an horizontal filtering channel

Flow and heat transfer dynamics inside different industrial chambers play a vital role in understanding momentum and heat transfer during industrial operations. Analysis of such flow and heat transfer helps operators to know how the system works. To better understand the filtration process, the current study analytically investigated the internal flow and heat transfer through a porous horizontal filter channel under the influence of a uniform magnetic field while removing unwanted contaminations from the fluid inside the filter chamber. Thus, the novelty of the current study is to advance the filtration process by investigating how the top moving wall, which aims to minimise filter cake formation, affects permeates outflow (the current design). The partial differential equations (PDEs) model representing the internal flow and heat transfer during filtration is transformed into a system of ordinary differential equations (ODEs) using Lie point symmetry reduction without changing the dynamics under investigation. After that, the transformed equations are solved analytically using the perturbation approximation technique. The comparative analysis between the obtained semi-analytical and NDSolve numerical solutions was used to show the correlation of internal flow, temperature, and pressure profiles. The obtained solutions are used to find the best combination of dimensionless parameters that arise from flow and heat transfer dynamics that lead to optimum outflow. Graphical analysis of flow and heat transfer dynamics are used to indicate the combination of parameters that leads to maximum outflow based on scientific evidence. It is observed that, on average, the velocity increases significantly by 122.55% across all cases of Re ranging from 0 to 3.2 at the top permeable wall y=1. This significant increase is due to the motion of the moving wall and fluid injection happening at y=1. The results show that more chamber volume, small pores size, weak injection, weak magnetic force, and less Joule heating are crucial to increase internal temperature and permeate outflow velocity during filtration.

Improved sample introduction approach in hydrophilic interaction liquid chromatography to avoid breakthrough of proteins

When therapeutic proteins are analysed under hydrophilic interaction liquid chromatography (HILIC) conditions, there is an inherent mismatch between the sample diluent (proteins must be solubilised in aqueous media) and the mobile phase, which is mostly composed of aprotic solvent (acetonitrile). This difference in eluent strength between sample diluent and mobile phase is responsible for severe analyte breakthrough and peak distortion. As demonstrated with therapeutic proteins of different sizes (insulin of 6 kDa, anakinra of 17 kDa and rituximab subunits of 25 and 50 kDa), only very small volumes of 0.1–0.2 µL can be injected without breakthrough effects, when performing rapid analysis on short HILIC columns of 20–50 mm, leading to poor sensitivity. In order to avoid the undesired effect of the strong sample diluent, a special injection program should be preferred. This consists in the addition and automatic injection of a defined volume of weak solvent (acetonitrile) along with the sample to increase retention factors during sample loading. Various injection programs were tested, including the addition of a pre-injection or post-injection or both (bracketed injection) of acetonitrile plugs. Several weak to strong injection solvent ratios of 1:1, 1:2, 1:4 and 1:10 were tested. Our work proves that the addition of a pre-plug solvent with a weak vs. strong injection solvent ratio of 1:10 is a valuable strategy to inject relatively large volumes of proteins in HILIC, regardless of column dimensions, thus maximising sensitivity. No peak deformation or breakthrough was observed under these conditions. However, it is important to note that peak broadening (40 % larger peaks) was observed when the injection program increased the injection solvent ratio from 1:1 to 1:10. Finally, this strategy was applied to a wide range of therapeutic mAb products with different physico-chemical properties. In all cases, relatively large volumes can be successfully injected onto small volume HILIC columns using a purely aqueous sample diluent, as long as an appropriate (weak) solvent pre-injection is applied.

Observation of spin polarization modulation responses of injection-locked vertical-cavity surface-emitting lasers

We report on the modulation responses of an injection-locked vertical-cavity surface-emitting laser (VCSEL) measured using an optical spin-polarization modulation technique. We reveal that weak injection locking is suitable to maintain a strong resonance response at a high-frequency region depending on the linear birefringence of the VCSEL, a unique feature of spin-polarization modulation response. The measured results can be reasonably reproduced with simulated ones on the basis of spin-flip rate equations. Our findings support novel applications of spin-controlled VCSELs with injection locking.

A massive, energetic model for the luminous transitional Type Ib/IIb SN 2020cpg

ABSTRACT Using a combined spectral and light-curve modelling approach, we fit a massive and energetic explosion model to the luminous Type Ib/IIb SN 2020cpg. This model has an ejected mass of ∼(7 ± 2) M⊙ with a final explosion energy of ∼(6 ± 1) × 1051 erg with MNi = 0.27 ± 0.05 M⊙. The early spectra are hot and blue with weak He i lines, and a complicated Hα region suggested to be a multicomponent feature. Modelling the spectra required ∼0.08 M⊙ of H at velocities >11 000 km s−1 and a total He mass of ∼1.0 M⊙ at velocities >9500 km s−1 above CO-rich ejecta. This model has a ratio of kinetic energy and ejected mass of 0.85$_{-0.3}^{+0.5}$ foe M⊙−1. The high luminosity and explosion energy results in a broadened Hα line that is blended with Si ii, C ii, and He i, which led to the initial classification of SN 2020cpg as a Type Ib. We instead classify SN 2020cpg as a bright transitional event between the Type Ib and Type IIb classes. Comparing our model parameters to stellar evolution models, a progenitor mass of 25–30 M⊙, i.e. stripped of most of the hydrogen shell and of some of the helium shell prior to collapse produces a He core of comparable mass. The excess 56Ni production in SN 2020cpg as compared to objects of similar ejected mass may suggest evidence of additional energy sources such as a failed GRB or weak magnetar energy injection, or a smaller remnant mass.

Experimental and Numerical Investigation on Oil Displacement Mechanism of Weak Gel in Waterflood Reservoirs.

The production performance of waterflood reservoirs with years of production is severely challenged by high water cuts and extensive water channels. Among IOR/EOR methods, weak gel injection is particularly effective in improving the water displacement efficiency and oil recovery. The visualized microscopic oil displacement experiments were designed to comprehensively investigate the weak gel mechanisms in porous media and the numerical simulations coupling equations characterizing weak gel viscosity induced dynamics were implemented to understand its planar and vertical block and movement behaviors at the field scale. From experiments, the residual oil of initial water flooding mainly exists in the form of cluster, column, dead end, and membranous, and it mainly exists in the form of cluster and dead end in subsequent water flooding stage following weak gel injection. The porous flow mechanism of weak gel includes the preferential plugging of large channels, the integral and staged transport of weak gel, and the residual oil flow along pore walls in weak gel displacement. The profile-control mechanism of weak gel is as follows: weak gel selectively enters the large channels, weak gel blocks large channels and forces subsequent water flow to change direction, weak gel uses viscoelastic bulk motion to form negative pressure oil absorption, and the oil droplets converge to form an oil stream, respectively. The numerical simulation indicates that weak gel can effectively reduce the water-oil mobility ratio, preferentially block the high permeability layer and the large pore channels, divert the subsequent water to flood the low permeability layer, and improve the water injection swept efficiency. It is found numerically that a weak gel system is able to flow forward under high-pressure differences in the subsequent water flooding, which can further improve oil displacement efficiency. Unlike the conventional profile-control methods, weak gels make it possible to displace the bypassed oil in the deep inter-well regions with significant potential to enhance oil recovery.

Injection Locking of Optoelectronic Oscillators With Large Delay

The optoelectronic oscillator is a delay line oscillator that leverages optical fibre technology to realize the large delay required for low phase noise systems. Spurious sidemodes are an artefact of the delay line oscillator, yet treatments of injection locking of optoelectronic oscillators have relied on the application of classical injection locking theory valid only for single mode oscillators. The large delay contributed by the optical fibre delay line is accounted for by the classical theory only in part through the quality factor Q that captures the round-trip group delay in a neighborhood of the oscillation frequency. This paper presents a new formulation of time delay oscillators subject to injection that describes all the essential features of their dynamics and phase noise. The common assumptions of a single mode oscillator and weak injection are removed. This is important to correctly predict the lock-in range, the suppression of sidemodes and the phase noise spectrum. The findings of the analysis are validated by experimental measurements provided by an optoelectronic oscillator under injection by an external source.

Effect of fast-burning compound ACP and catalyst on the combustion performance of Al/Mg-based fuel-rich HTPB propellants

In order to solve the problem of weak injection of fuel-rich propellant and to enhance its burning rate, the combustion behaviors of Al/Mg-based fuel-rich HTPB propellants with 40wt% metal content were studied with and without the addition of fast burning compound hydrated tetra-(4-amino-1, 2, 4-triazole) copper perchlorate (ACP) and burning rate catalyst Pb5. The results show that the burning rates of the Al/Mg-based fuel-rich HTPB propellants with the addition of fast burning compound and catalyst increase significantly, and the pressure exponents decrease. With the increase of pressure, the fluctuation of burning interface of the propellants increases and the flame height decreases. Compared with the Mg-based propellants of high burning rate, the agglomeration of condensed combustion products of the Al-based propellants is much more serious; the combustion extent of aluminum in the Al-based propellants is obviously lower than that of magnesium in the Mg-based propellants. These results are very meaningful for the design of fuel-rich HTPB propellants with high performance.

A Tsuji burner in a counterflow

This paper addresses the aerodynamics of a new type of Tsuji burner involving a cylindrical porous fuel injector of radius a placed at the centre of a planar air counterflow configuration with strain rate , with specific attention given to flows with large values of the Reynolds number , where ν represents the air kinematic viscosity. For cases in which the fuel-injection velocity is comparable to the characteristic counterflow velocity , the boundary layer is blown off from the cylinder surface, so that the flame is embedded in the thin twin mixing layers that form about the stream surfaces separating the outer air stream from the fuel stream. Molecular transport effects are confined to these mixing layers, while the flow structure outside is nearly inviscid, with the air-side velocity being potential, while the velocity found on the fuel side is rotational, because fuel injection generates vorticity through the requirement that fuel emerges normal to the cylinder surface. The inviscid flow is computed numerically, with use made of the streamfunction-vorticity formulation for values of the ratio of injection velocity to counterflow velocity , the only relevant parameter of the flow, ranging from small injection velocities to large injection velocities . Asymptotic methods are used to investigate the form of the solution for extreme values of Λ. In the limit of weak injection, the vorticity, scaling with , is confined to a thin near-cylinder boundary layer of thickness Λ that necessarily separates from the cylinder to form a cavity of finite size on both sides of the cylinder. In the opposite limit of strong injection, the vorticity needed to maintain the fuel flow normal to the porous cylinder is found to be small, of order , so that the flow is irrotational in the first approximation. The velocity distribution along the fuel-air interface is seen to determine the evolution of the diffusion flame, including the length of the stretched jet flames that develops along the counterflow centre plane.

Research on reasonable development strategy of offshore buried hill fractured reservoir

In order to improve the overall production degree of offshore buried hill fractured reservoir, expand the swept volume of water flooding, and improve the reservoir development effect, according to the actual reservoir characteristic parameters, numerical simulation software and three-dimensional physical model are used to study the reasonable pressure level, injection production mode and water flooding strategy of Oilfield A. The results show that, according to the pressure sensitivity experiment and numerical simulation analysis, the reasonable formation pressure is 70% of the original pressure for the buried hill fractured reservoir, and higher recovery can be achieved at this pressure level. By comparing different injection and production mode schemes, it is determined that under the weak injection and forcible production mode, the swept volume of reservoir water flooding is the largest, the water free recovery period of production wells is longer, and the water cut rising rate is low. The reservoir development is divided into four stages. For different stages, depressurization production, pulse water flooding, cyclic water flooding and asynchronous water flooding strategies are adopted respectively. Compared with the conventional stable water flooding strategy, the balanced development of fractures and matrix can be realized, so as to improve the full cycle development effect of the reservoir. The application of the development strategy results in this study to oilfield production practice has played an obvious role in improving the development effect of fractured reservoir, which has field practical significance and can provide reference for the development of similar fractured reservoir.

Giant inverse Rashba-Edelstein effect: Application to monolayer OsBi2

We propose that the hybridization between two sets of Rashba bands can lead to an unconventional topology where the two Fermi circles from different bands own in-plane helical spin textures with the same chiralities, and possess group velocities with the same directions. Under the weak spin injection, the two Fermi circles both give the positive contributions to the spin-to-charge conversion and thus induce the giant inverse Rashba-Edelstein Effect with large conversion efficiency, which is very different from the conventional Rashba-Edelstein Effect. More importantly, through the first-principles calculations, we predict that monolayer OsBi2 could be a good candidate to realize the giant inverse Rashba-Edelstein Effect. Our studies not only demonstrate a new mechanism to achieve highly efficient spin-to-charge conversion in spintronics, but also provide a promising material to realize it.

Electrical Conduction Currents Prior to Negative Streamer Inception in Mineral-Oil/Solid Interfaces

This paper is an experimental study of the electrical conduction of mineral-oil/solid interfaces in negative polarity. This study is performed in a point-plane configuration immersed in mineral oil submitted to impulse voltages. The interface is assembled with an inclined solid in contact with the point electrode tip. Charge recordings and conduction currents of different combinations of mineral-oil/solid interfaces are reported. Different polymers and oil-impregnated papers are used as the solid materials. It is found that for voltages lower than the inception voltage, the injection of charge belongs to a weak injection regime. The spatial limitation with solids of similar permittivity as the mineral oil decreases the charge injection. The charge injection at mineral-oil/solid interfaces follow two conduction current type characteristics. Experiments with mineral-oil/PTFE interface shows the existence of a transition between both conduction current types if the applied voltage is increased.

Electro-thermo-convection in a differentially heated square cavity under arbitrary unipolar injection of ions

A numerical investigation of electro-thermo-convection in a 2-D differentially heated square cavity filled with a dielectric liquid is presented. Fully coupled governing equations of electric potential, charge transport, Navier–Stokes equations, and the energy equation are implemented in the finite-volume framework of OpenFOAM®. For this kind of electro-thermo-convection, previous studies mainly focused on the strong injection regime. This study extends the analysis to arbitrary injection strengths in weak, medium and strong regimes. Moreover, the flow configuration considered in this study investigates the simultaneous action of buoyancy and Coulomb forces acting in orthogonal direction to each other. For strong and medium injection, the flow transforms from a steady two-cell flow to a periodic two-cell flow and finally evolves into a chaotic flow with multiple cells, as the value of T is increased. In the weak injection regime, chaotic flow with multiple flow cells is observed right from the onset of instability. Heat transfer rates and the maximum velocity are directly proportional to the electric Rayleigh number T. Present study gives an insight into different flow structures and the related heat transfer phenomenon at arbitrary injection strengths.

Study of mutual injection-pulling between two mutually-coupled single-loop optoelectronic oscillators

This paper analyzes the injection-locking and injection-pulling behavior of two mutually coupled single-loop free-running OEOs with nearby frequencies. We derive the phase dynamics equations of two mutually-coupled OEOs considering weak RF signal injection and the phase stability of the mutually injection-locked system is studied. Also, we present compact closed form expressions for the oscillation frequencies of two mutually injection-pulled OEOs in terms of the injection-ratios and the phase shifts of the mutually injected RF signals. The beat frequency of the mutually injection-pulled system is calculated in terms of the injection ratios. The influence of mutual injection-pulling on the RF output power spectrums of two OEOs are studied. It is shown that the RF output power spectrums of two mutually injection-pulled OEOs are highly asymmetric and strongly depends on the injection ratios. The experimental results corroborating the theoretical findings are given.

Source injection coupled quadrature oscillator: transient oscillation amplitude and thermally induced phase noise

This paper analyzes the transient oscillation amplitude of the source injection coupled quadrature oscillator (SIC-QOSC). With the help of the Describing Function Method, we estimate an expression to describe the nonlinear behavior of the negative transconductor. Using the estimated expression, we obtain an accurate closed-form formula for the time-domain amplitude of the SIC-QOSC. The proposed formula could be useful for designers to analyze the transient behavior of the SIC-QOSC. This aspect of SIC-QOCS has not studied yet. Also, this paper analyzes the thermally induced phase noise of the SIC-QOSC. For this purpose, we use the weak injection method. Using the extracted formulas, designers can understand the design tradeoffs to design an optimum SIC-QOSC. To evaluate the validity of the extracted formulas for the transient oscillation amplitude as well as the phase noise, we compare the calculated results with the appropriate simulations. Simulations have been done in 0.18 µm CMOS technology with a 1.8 V supply voltage. We reached a good agreement between the simulations and our analytical results.

Controllable vortex shedding from dissipative exchange flows in ferromagnetic channels

Ferromagnetic channels subject to spin injection at one extremum sustain long-range coherent textures that carry spin currents known as dissipative exchange flows (DEFs). In the weak injection regime, spin currents carried by DEFs decay algebraically and extend through the length of the channel, a regime known as spin superfluidity. Similar to fluids, these structures are prone to phase-slips that manifest as vortex-antivortex pairs. Here, we numerically study vortex shedding from DEFs excited in a magnetic nanowire with a physical obstacle. Using micromagnetic simulations, we find regimes of laminar flow and vortex shedding as a function of obstacle position tunable by the and spin injection sign and magnitude. Vortex-antivortex pairs translate forward (VF regime) or backward (VB regime) with respect to the detector's extremum, resulting in well-defined spectral features. Qualitatively similar results are obtained when temperature, anisotropy, and weak non-local dipole fields are included in the simulations. These results provide clear features associated with DEFs that may be detected experimentally in devices with nominally identical boundary conditions. Furthermore, our results suggest that obstacles can be considered as DEF control gates, opening an avenue to manipulate DEFs via physical defects.

Experimental investigation on the injection profile variation in the weak gel injection process

In this paper, the gel-forming performance and rheological properties of weak gel systems were studied through laboratory gel-forming experiments. The plugging behavior and mechanism of the weak gel system for sand-packed tubes with different permeability were evaluated. The results showed that intramolecular cross-linking was dominated when the polymer concentration was low and the viscosity increased litter after gelation. Intermolecular cross-linking plays a major role when the polymer concentration is high. The injection speed has a great influence on the resistant factor (RF in short) of the weak gel. During low-speed injection, the weak gel has a large amount of retention on the surface of the rock particles, resulting the high viscosity of the weak gel. The RF during low-speed injection is much higher than that in high-speed injection and it keeps increasing as the injection volume increase. The impact of the injection rate on RF of hydrolyzed polyacrylamide (HPAM) is significantly lower than weak gels, because the retention of HPAM in the sand-packed tube reaches a stable level, the RF remains basically unchanged.

Characteristics of Weak-Gel Flooding and Its Application in LD10-1 Oilfield.

Weak gel is a kind of three-dimensional cross-linking system with low polymer concentration and appropriate cross-linking agents, dominated by intermolecular cross-linking, supplemented by intramolecular cross-linking, and with a weak cross-linking degree. In this paper, the microstructure and properties of the weak gel were observed and evaluated under different conditions. Seepage behavior experiments and parallel core displacement experiments were carried out to evaluate profile control and flooding performance of the weak gel. Under a certain polymer concentration, with the increase in cross-linker concentration, the reticular structure of the weak gel becomes more uniform and the strength of the weak gel was further enhanced. Weak gel has more retention in porous media and greater strength. The profile control and flooding performance of the weak gel are much better than those of the polymer. A field test of weak-gel flooding was successfully carried out in LD10-1 oilfield. Most of the production wells around the weak gel injection wells responded after weak-gel injection and the accumulative oil incremental oil production of the test area was 57.8 × 104 m3 up to December 2018.

On the Energy Coupling Efficiency of AGN Outbursts in Galaxy Clusters

Abstract Active galactic nucleus (AGN) jets are believed to be important in solving the cooling flow problem in the intracluster medium (ICM), while the detailed mechanism is still under debate. Here we present a systematic study on the energy coupling efficiency η cp, the fraction of AGN jet energy transferred to the ICM. We first estimate the values of η cp analytically in two extreme cases, which are further confirmed and extended with a parameter study of spherical outbursts in a uniform medium using hydrodynamic simulations. We find that η cp increases from ∼0.4 for a weak isobaric injection to ≳0.8 for a powerful point injection. For any given outburst energy, we find two characteristic outburst powers that separate these two extreme cases. We then investigate the energy coupling efficiency of AGN jet outbursts in a realistic ICM with hydrodynamic simulations, finding that jet outbursts are intrinsically different from spherical outbursts. For both powerful and weak jet outbursts, η cp is typically around 0.7–0.9, partly due to the nonspherical nature of jet outbursts, which produce backflows emanating from the hot spots, significantly enhancing the ejecta–ICM interaction. While for powerful outbursts a dominant fraction of the energy transferred from the jet to the ICM is dissipated by shocks, shock dissipation only accounts for ≲30% of the injected jet energy for weak outbursts. While both powerful and weak outbursts could efficiently heat cooling flows, powerful thermal-energy-dominated jets are most effective in delaying the onset of the central cooling catastrophe.

On the Weak-Injectivity Profile of a Ring

We consider two types of weak-injectivity domains of a module. Small weak-injectivity domains gauge the extent of weak injectivity of modules; weak-injectivity domains are an alternative way to gauge their injectivity. We focus on notions which are opposite, respectively, to weakly injective or injective modules according to these two schemes. While we do consider both notions to some extent, our emphasis is on modules with smallest weak-injectivity domain; we name those modules extremely poor. The intersection of all (small) domains of weak injectivity is the natural focus of attention. The intersection of all (small) domains of weak injectivity contains the class of all (finitely generated) semisimple modules, but it is not always equal to it. The domain of weak injectivity of an extremely poor module thusly depends on the ring in question. We consider necessary and sufficient conditions for said intersections to consist solely of semisimple modules and look at examples of both circumstances, when this is the case and when it is not. When the intersection of weak-injectivity domains consists of semisimple modules, every extremely poor module is poor; we study further connections between these two notions. Comparisons are also drawn to paupers (poor modules with no proper poor direct summands); paupers are a type of poor module that is significant in understanding the intrinsic structure of poor modules. Extremely poor modules over PCI domains and extremely poor abelian groups are given particular attention.