Drift Mechanism Research Articles

An investigation on the novel granular composite of Co2FeSi Heusler alloy with Mn and Al2O3: Structural and magnetic properties

The magnetic-field-induced resistance switching of a granular composite containing Co 2 FeSi with Mn and Al 2 O 3 was investigated for the first time. Field emission scanning electron microscopy (FESEM) images showed a mean particle size of about 100–150 nm. Different compositions of materials showed different Magnetoresistance (MR). Positive and negative MR responses were observed in the samples while the possible mechanisms were also discussed. The electric resistance of the samples increased by the Al 2 O 3 amount and tunneling became the dominant electron drift mechanism. The electron conductance percolation threshold of the composite was found to be around 20 to 30 wt% Al 2 O 3 in which the MR reached a maximum value. This paper is part of a series of systematic investigations on these novel composites publishing for the first time. • The sharp resistance increase at Al 2 O 3 ratios shows the behavior of the sample changes from metal to insulator. • This research indicates the effect of initial magnetization on the MR behavior of the granular composites. • This investigation can pave the way for the development of granular magnetoresistive elements with novel composites.

Suppressed drift and low-noise sensor module with a single-axis gold proof-mass MEMS accelerometer for micro muscle sound measurement

This paper describes a highly sensitive microelectromechanical systems (MEMS) accelerometer sensor module to measure micro muscle sounds. Regarding the drift mechanism, we focus on charged particles based on residual water related to MEMS fabrication. Based on temperature programmed desorption analysis and electrical experiments, it is clarified that the drift is caused by negatively charged OH− and is suppressed by vacuum packaging. The noise floor can be reduced by the improved sensitivity of the MEMS accelerometer. The developed MEMS accelerometer can realize the sensitivity of 1157.0 fF/G and Brownian noise of 149.0 nG/√Hz. The developed sensor module consisting of the developed MEMS accelerometer and the capacitance to digital converter can achieve a noise floor of 26.7 μG/√Hz without any obvious drifts, establishing the target value of less than 50 μG/√Hz. Therefore, it is confirmed that the developed sensor module can detect micro muscle sounds without contracting a muscle in the frequency range of 20–40 Hz.

Reconfigurable halide perovskite nanocrystal memristors for neuromorphic computing

Many in-memory computing frameworks demand electronic devices with specific switching characteristics to achieve the desired level of computational complexity. Existing memristive devices cannot be reconfigured to meet the diverse volatile and non-volatile switching requirements, and hence rely on tailored material designs specific to the targeted application, limiting their universality. “Reconfigurable memristors” that combine both ionic diffusive and drift mechanisms could address these limitations, but they remain elusive. Here we present a reconfigurable halide perovskite nanocrystal memristor that achieves on-demand switching between diffusive/volatile and drift/non-volatile modes by controllable electrochemical reactions. Judicious selection of the perovskite nanocrystals and organic capping ligands enable state-of-the-art endurance performances in both modes – volatile (2 × 106 cycles) and non-volatile (5.6 × 103 cycles). We demonstrate the relevance of such proof-of-concept perovskite devices on a benchmark reservoir network with volatile recurrent and non-volatile readout layers based on 19,900 measurements across 25 dynamically-configured devices.

Ambivalence in decision making: An eye tracking study

An intuition of ambivalence in cognition is particularly strong for complex decisions, for which the merits and demerits of different options are roughly equal but hard to compare. We examined information search in an experimental paradigm which tasked participants with an ambivalent question, while monitoring attentional dynamics concerning the information relevant to each option in different Areas of Interest (AOIs). We developed two dynamical models for describing eye tracking curves, for each response separately. The models incorporated a drift mechanism towards the various options, as in standard drift diffusion theory. In addition, they included a mechanism for intrinsic oscillation, which competed with the drift process and undermined eventual stabilization of the dynamics. The two models varied in the range of drift processes postulated. Higher support was observed for the simpler model, which only included drifts from an uncertainty state to either of two certainty states. In addition, model parameters could be weakly related to the eventual decision, complementing our knowledge of the way eye tracking structure relates to decision (notably the gaze cascade effect).

The Remarkable Spin-down and Ultrafast Outflows of the Highly Pulsed Supersoft Source of Nova Herculis 2021

Abstract Nova Her 2021 (V1674 Her), which erupted on 2021 June 12, reached naked-eye brightness and has been detected from radio to γ-rays. An extremely fast optical decline of 2 magnitudes in 1.2 days and strong Ne lines imply a high-mass white dwarf. The optical pre-outburst detection of a 501.42 s oscillation suggests a magnetic white dwarf. This is the first time that an oscillation of this magnitude has been detected in a classical nova prior to outburst. We report X-ray outburst observations from Swift and Chandra that uniquely show (1) a very strong modulation of supersoft X-rays at a different period from reported optical periods, (2) strong pulse profile variations and the possible presence of period variations of the order of 0.1–0.3 s, and (3) rich grating spectra that vary with modulation phase and show P Cygni–type emission lines with two dominant blueshifted absorption components at ∼3000 and 9000 km s−1 indicating expansion velocities up to 11,000 km s−1. X-ray oscillations most likely arise from inhomogeneous photospheric emission related to the magnetic field. Period differences between reported pre- and post-outburst optical observations, if not due to other period drift mechanisms, suggest a large ejected mass for such a fast nova, in the range 2 × 10−5–2 × 10−4 M ⊙. A difference between the period found in the Chandra data and a reported contemporaneous post-outburst optical period, as well as the presence of period drifts, could be due to weakly nonrigid photospheric rotation.

Identifying key regulators of the intestinal stem cell niche.

The intestinal tract is lined by a single layer of epithelium that is one of the fastest regenerating tissues in the body and which therefore requires a very active and exquisitely controlled stem cell population. Rapid renewal of the epithelium is necessary to provide a continuous physical barrier from the intestinal luminal microenvironment that contains abundant microorganisms, whilst also ensuring an efficient surface for the absorption of dietary components. Specialised epithelial cell populations are important for the maintenance of intestinal homeostasis and are derived from adult intestinal stem cells (ISCs). Actively cycling ISCs divide by a neutral drift mechanism yielding either ISCs or transit-amplifying epithelial cells, the latter of which differentiate to become either absorptive lineages or to produce secretory factors that contribute further to intestinal barrier maintenance or signal to other cellular compartments. The mechanisms controlling ISC abundance, longevity and activity are regulated by several different cell populations and signalling pathways in the intestinal lamina propria which together form the ISC niche. However, the complexity of the ISC niche and communication mechanisms between its different components are only now starting to be unravelled with the assistance of intestinal organoid/enteroid/colonoid and single-cell imaging and sequencing technologies. This review explores the interaction between well-established and emerging ISC niche components, their impact on the intestinal epithelium in health and in the context of intestinal injury and highlights future directions and implications for this rapidly developing field.

Electrical Characterization and Study of Current Drift Phenomena and Hysteresis Mechanism in Junctionless Ion-Sensitive Field-Effect Transistor

A comprehensive study of the drain current drift mechanism and hysteresis phenomena in fabricated p-channel junctionless ion-sensitive field-effect transistor (JL-ISFET) has been investigated for the first time. The current drift measurements have been performed through transient analysis of drain current, under different pH and liquid-gate bias (Vlg). Further, time-dependent gate-capacitance (CG) has also been analyzed to see the effect of hydroxyl ions (OH−) in the sensing film (Al2O3). The hysteresis has also been investigated for different pH loop (7 → 3 → 7 → 11 → 7 and 7 → 11 → 7 → 3 → 7) and times (960s, 1500s, and 1920s). It has been observed that the drift of JL-ISFET occurs because of chemical modification of the sensing film, due to OH−. The proposed device exhibits a threshold voltage sensitivity of 58.2 mV/pH that is near the Nernstian limit. Further, the hysteresis width and maximum drain current drift are measured as \(\sim \) 1.3 mV and 2.4 μ A (\(\sim \) 75%), respectively.

Research advances of the drift reducing technologies in application of agricultural aviation spraying

With the gradual deterioration of the ecological environment and the increase in requirements for the quality of modern life, the use of pesticides is bound to develop towards higher pesticide utilization and less environmental pollution, and the low-volume spraying for agricultural aviation operation combined with the Drift Reducing Technologies (DRTs) may be a useful way to achieve this goal. Based on an analysis of the spray drift mechanism and the primary factors influencing aerial spraying, previous research on DRTs in aerial spraying were reviewed and summarized, and it was found that DRTs in aerial spraying can effectively reduce the environmental pollution caused by pesticide drift by reducing the spraying amount of pesticides and improving the control effect of pesticides, included aerial electrostatic spray technology, aerial spray adjuvant, aerial air-assisted spray technology, drift reducing nozzles and aerial variable-rate spray technology. And according to the analysis of the current research status, some suggestions and countermeasures to reduce droplet drift of agricultural aviation spraying were put forward from the aspects of strengthening the research on DRTs for plant protection Unmanned Aerial Vehicle (UAV) and adopting reasonable DRTs methods. It is hoped that provide reference and guidance for the enterprises’ product improvement and users’ practical operation, and play the advantages of precision agricultural aviation spraying fully. Keywords: agricultural aviation spraying, pesticide, drift, DRTs, precision agriculture DOI: 10.25165/j.ijabe.20211405.6225 Citation: Chen S D, Lan Y B, Zhou Z Y, Deng X L, Wang J. Research advances of the drift reducing technologies in application of agricultural aviation spraying. Int J Agric & Biol Eng, 2021; 14(5): 1–10.

Gallium-Nitride Field Effect Transistors in Extreme Temperature Conditions

Abstract Compact power electronic circuits and higher operating temperatures of switching devices call for an analysis and verification on the impact of the parasitic components in these devices. The found drift mechanisms in a gallium-nitride field effect transistors (GaN-FET) are studied by literature and related to measurement results. The measurements in extreme temperature conditions are far beyond the manufacturer-recommended operating range. Influences to parasitic elements in both static and dynamic operation of the GaN-FETs are investigated and related toward device losses in switch-mode power electronic circuits with the example of a half-bridge circuit. In this article, static operation investigation on the effect of temperature toward resistance, leakage currents, and reverse conduction is conducted. Dynamic operation between the two states of GaN-FET is also addressed and related to the potential impact in a switching circuit losses. A thermal chamber was built to precisely measure the effect of temperature toward parasitic elements in the devices using a curve tracer. It was found that the increment in RDSon, IDSS, IGSS, and VSD can be justified by the literature and verified by measurements. Incremental COSS and decreasing VGSth was found when exposing devices to extreme temperatures. These two parameters give real challenge over designing circuits at high temperature where timing is critical. Albeit temperature challenges, it is found that investigated GaN-FETs have potential to be used in extreme temperature-operating conditions.

Parabolic velocity profile causes shape-selective drift of inertial ellipsoids

Understanding particle drift in suspension flows is of the highest importance in numerous engineering applications where particles need to be separated and filtered out from the suspending fluid. Commonly known drift mechanisms such as the Magnus force, Saffman force and Segré–Silberberg effect all arise only due to inertia of the fluid, with similar effects on all non-spherical particle shapes. In this work, we present a new shape-selective lateral drift mechanism, arising from particle inertia rather than fluid inertia, for ellipsoidal particles in a parabolic velocity profile. We show that the new drift is caused by an intermittent tumbling rotational motion in the local shear flow together with translational inertia of the particle, while rotational inertia is negligible. We find that the drift is maximal when particle inertial forces are of approximately the same order of magnitude as viscous forces, and that both extremely light and extremely heavy particles have negligible drift. Furthermore, since tumbling motion is not a stable rotational state for inertial oblate spheroids (nor for spheres), this new drift only applies to prolate spheroids or tri-axial ellipsoids. Finally, the drift is compared with the effect of gravity acting in the directions parallel and normal to the flow. The new drift mechanism is stronger than gravitational effects as long as gravity is less than a critical value. The critical gravity is highest (i.e. the new drift mechanism dominates over gravitationally induced drift mechanisms) when gravity acts parallel to the flow and the particles are small.

Influence of particle-fluid density ratio on the dynamics of finite-size particles in homogeneous isotropic turbulent flows.

In this paper, direct numerical simulations of particle-laden homogeneous isotropic turbulence are performed using lattice Boltzmann method incorporating interpolated bounce-back scheme. Four different particle-fluid density ratios are considered to explore how particles with different particle-fluid density ratios respond to the turbulence. Overall particle dynamics in the homogeneous isotropic turbulence such as the Lagrangian statistics of single particle and the preferential concentration of particles are investigated. Results show that particle acceleration and angular acceleration are more intermittent than velocity and angular velocity for finite-size particles with different particle-fluid density ratios. The preferential concentration of particles is investigated using radial distribution function and Voronoï tessellation, and the preferential concentration is more profound for particles with two intermediate particle-fluid density ratios. The Voronoï analysis indicates that the distribution of Voronoï cells satisfy the log-normal distribution better than the gamma distribution. The mechanism of preferential concentration is analyzed using the sweep-stick mechanism and drift mechanism. Results show that although a higher probability of having particles located near the sticky points is found, the sticky mechanism is very weak for large density ratios. The particle clustering is then found to be better qualitatively described by the drift mechanism.

Test Particle Model Predictions of SEP Electron Transport and Precipitation at Mars

AbstractExtreme space weather events can episodically release solar energetic particles (SEPs) that precipitate into planetary atmospheres, leading to aurora and increased ionization. While the induced magnetosphere of Mars does not substantially obstruct SEP protons, the effect on SEP electrons is not known. We use a test particle model modified for relativistic electrons to model transport of 10–200 keV electrons from outside the bow shock and deep in the magnetotail of Mars. We find a substantial influence of curvature and gradient drifts on precipitation, leading to depletions in the bow shock and transport onto closed field lines. The model estimates ∼3% of incident flux precipitates into the Mars atmosphere for a typical SEP event under nominal solar wind conditions, exceeding the estimate from the guiding center path approximation without drift terms. Precipitation is globally patchy. The model estimates 55% of electrons precipitating into cusps along open field lines and 45% precipitating on closed field lines, suggesting drift and nonadiabatic transport mechanisms have a significant influence on precipitation. We also predict that the fraction of precipitating differential flux increases as a function of energy. We discuss how these predictions would be affected by disturbed conditions that tend to accompany the arrival of SEPs and by differing SEP electron spectra hardness and anisotropy. We finally discuss how the simulation predictions compare to observations of diffuse aurora.

Molecular-level evaluation of ionic transport under external electric fields in biological dielectric liquids

Ionic conduction is a critical parameter to evaluate the electrical performance of biological dielectric liquids. In this work, detailed molecular dynamics (MD) simulations were carried out to reveal both drift mechanisms of ions (H3O+, Cu2+, OH– and Cl-) and local structure evolution characteristics in biological dielectric liquids under external electric fields. The drift velocities of all ionic species increase nonlinearly with the addition of static electric fields. At relatively low field regimes, the structural cages formed by corresponding biological dielectric molecules are found to reduce ion transport. Above certain field thresholds, the accelerated ions impart appreciable energy to the surrounding molecular segments, making the binding of the cages broken. As such, the electric motion as a replacement of the thermal motion is eventually taken place. The computed thresholds are 0.97 V/nm, 0.645 V/nm, 0.67 V/nm, and 0.77 V/nm for H3O+, Cu2+, OH–, and Cl-, respectively. Additionally, given the electrostatic potential feature of biological dielectric molecules, the structural cages have greater advantages in limiting cationic migration, in which the binding effect for cations is more stable and persistent. The results provide a helpful guideline for designing the next-generation biological dielectric liquids.

Enhancement Mode GaN-FETs in Extreme Temperature Conditions, Part I: Static Parasitic Parameters

Abstract Smaller packaging and sizing of power electronics and higher operating temperatures of switching devices call for an analysis and verification on the impact of the parasitic components in these devices. Found drift mechanisms in an eGaN-FET are studied by literature and related to measurements performed in extreme temeprature conditions far beyond the manufacturer recommended operating range. A thermal chamber was build to precisely measure the effect of temperature in these devices using a curve tracer. It is found that the increment in RDSon, IDSS, IGSS and VSD can be justified by the theory and backed up by measurements. It is also found that the particular eGaN-FET can be suited for extreme temperature operating conditions.

Temperature dependences of the elektrophysical properties of the solid solution Si1-xSnx (0  x  0.04)

The current-voltage characteristics of p-Si–n-Si1-xSnx (0  x  0.04) structures have been studied in the temperature range from 293 to 453 K. It was determined that the initial sections of the direct branches of the I–V characteristic at all temperatures are described by the expo-nential dependence of the current on the voltage, and then a quadratic section follows, which is described by the drift mechanism of carrier transfer in the regime of ohmic relaxation of the space charge. We determined the activation energies of two deep levels with values of 0.21 eV and 0.35 eV, which are assigned to interstitial Sn atoms and A-centers, respectively. The prospect of using solid solutions Si1-xSnx (0  x  0.04), obtained on silicon substrates, as an active material in the manufacture of injection diodes is substantiated.

Performance-based-plastic design method of reinforced concrete structure for operational performance level

Under major load earthquakes, reinforced concrete structures designed according to the current codes will experience an inelastic deformation which is difficult to predict and control. Performance-based plastic design (PBPD) methodology is applied forward to design reinforced concrete structures in this study. In this method, as performance criteria, the target drift and yield mechanisms are preselected. Based on the work-energy balance principle, the design base shear is given as earthquake level and calculated as work required to push the structure as monotonically load to the target drift. The load equals the energy needed by an equivalent single degree of freedom in the same state. The plastic design is utilized to design the desired yield mechanism. The method was adopted on a 10-story reinforced concrete structure with an earthquake load in lateral forces based on SNI 1726:2019 and the Performance-Based Plastic Design (PBPD) method. Pushover analysis was carried out where the structure was pushed to obtain lateral load resistance followed by yielding gradually until plastic deformation occurred collapse From the pushover analysis, the ductility value for SNI 1726:2019 is less ductile than analytical using the Performance-Based Plastic Design (PBPD) method

Long-time drift induced changes in electrical characteristics of graphene–metal contacts

Chemical vapour deposition (CVD) graphene is commonly recognized as promising 2D material for development of electronic devices. However, the long-term drift of electrical parameters still requires deeper understanding before the technological means can be selected for an individual type of the devices. In this work, the changes in the electrical resistance were investigated over long time in the planar samples based on the CVD graphene with Au and Ni contacts. The samples were arranged as arrays of the resistors on a silicon substrate covered with a 250 nm layer of thermally grown silicon dioxide. The annealing in pure argon gas flow at 573 K was used to return the electrical properties of samples to the initial state. The effects of drift and annealing were compared for the three parts of structures, namely the electrical contact, the graphene sheet and the edge of the metal film with a hanging graphene sheet. For these parts, the resistance changes were related to the strain and doping of supported and hanged parts of the graphene sheet. Raman spectroscopy and Kelvin force probe microscopy were used to characterize charge doping, strain and work function in the graphene. The drift was explained in terms of the most prominent changes in the doping, strain and work function detected within the edge zone of the contact. It was proved that the annealing significantly changed the p-type doping and work function in the graphene layer in this edge zone. The properties were almost independent of test conditions in the SiO2 supported graphene. The changes in the contact parameters produced by drift mechanisms were proved being reversible under proper annealing conditions.

Delta distribution of electronegative plasma predicted by reformed “spring oscillator” dynamic equation with dispersing force

In our relevant paper [Zhao S X (2021) Chin. Phys. B 30 055201], a delta distribution of negative ions is given by fluid simulation and preliminarily explained by decomposed anions transport equation. In the present work, first, the intrinsic connection between the electropositive plasma transport equation and spring oscillator dynamic equation is established. Inspired by this similarity, reformed “spring oscillator” equation with dispersing instead of restoring force that gives quasi-delta solution is devised according to the math embodied in the anion equation, which is of potential significance to the disciplines of atomic physics and astronomy as well. For solving the “diffusion confusion”, the physics that determines the delta profile within the continuity equation is explored on the basis that recombination loss source term plays the role of drift flux, which is applicable for fluid model of low temperature plasma, but not the ordinary fluid dynamics. Besides, the math and physics revealed in this work predict that the ratio of recombination or attachment (for electrons) frequency versus the species diffusion coefficient is a very important parameter in determining the delta distribution, as it acts as the acceleration of object, according to the reformed oscillator equation. With this theory, the analogous delta profile of electrons density in the famous drift and ambi-polar diffusion heating mechanism of electronegative capacitively coupled plasma is interpreted.

Seismic performance assessment of steel strip dampers equipped in high-rise steel frame

This paper aims to utilize a novel steel strip damper to enhance seismic resilience of high-rise steel frame in high seismic intensity regions. The developed damper is composed of external casing, internal casing and steel strip fuses dissipating seismic energy via bending-dominated deformation throughout the entire section, which is convenient for post-earthquake replacement. A series of cyclic loading tests have shown the damper's good energy dissipation capacity with features of stable and full hysteretic loops. A numerical model for the damper is proposed and validated by the experimental results. Then a 20-story steel frame is adopted as the representative building and retrofitted using a design procedure based on the stiffness and displacement demands. Nonlinear dynamic analysis considering damper failure is performed to evaluate seismic responses of the steel frames. And incremental dynamic analysis is employed to discuss the seismic fragility. Finally, seismic losses of the steel frames are assessed through the story-based loss estimation method in which the demolition-related economic losses are included. The analyses indicate that the presented damper can obviously mitigate the roof displacement, inter-story drift, plastic damage and soft story deformation mechanism; the damper-fused frame has much lower probability to collapse; the expected total losses, expected annual losses and expected life-cycle losses are significantly decreased by retrofitting with the novel dampers.

Mechanical drift modeling and analysis of V-shaped linear ultrasonic motors with a flexible clamp

The flexible clamp used in linear ultrasonic motors (LUMs) not only supports the motor but also simplifies the structure and improves the vibration characteristics. However, the flexible clamp causes the mechanical drift phenomenon, leading to a reduction in positional accuracy. To solve this problem, the mechanical drift mechanism and the control methods of V-shaped LUMs are investigated in this work. First, a mechanical model of the stator of a LUM with a flexible clamp is established to analyze the reason for the mechanical drift. Then, based on the mechanical model, the rules of the appearance of mechanical drift in clamping components with different stiffnesses and shapes are studied. The results indicate that mechanical drift is obvious when the stiffnesses of the two flexible clamps are different, whereas it hardly occurs when clamping components with tremendous tangential stiffnesses are used. Finally, two new types of V-shaped LUM stators that have a flexible clamp on one side and an analogous straight-beam clamp on the other side are proposed. Experiments were conducted to validate the mechanical model analysis and the clamp drift findings, and the results demonstrate that the novel motors have little mechanical drift and stable running characteristics and can be used in precision motion platforms.