scholarly journals Dynamics and stability of skyrmions in a bended nano-beam

2021 ◽  
Author(s):  
Anruo Zhong ◽  
Xiaoming Lan ◽  
Yangfan Hu ◽  
Biao Wang
Keyword(s):  
Energy Cost ◽  
High Mobility ◽  
Bending Moment ◽  
Elastic Fields ◽  
Spintronic Devices ◽  
Bulk Stress ◽  
The Stability ◽  
Magnetic Skyrmions ◽  
Nontrivial Topology ◽  
A Current

Abstract Magnetic skyrmions are attracting much attention due to their nontrivial topology and high mobility to electric current. Nevertheless, suppression of the skyrmion Hall effect and maintaining high velocity of skyrmions with low energy cost are two major challenges concerning skyrmion-based spintronic devices. Here we show theoretically that in a nano-beam suffering appropriate bending moment, both Bloch-type and Néel-type skyrmions move with a vanishing Hall angle under a current density smaller than that required when the bending is absent. Moreover, bending alone can be used to move skyrmions, whose velocity is solved analytically from the Thiele equation. Generally speaking, inhomogeneous elastic fields affect the stability and dynamics of skyrmions, where the local stability is dominantly determined by the local bulk stress. These findings throw new light on how to drive skyrmions straightly with lower energy cost, which is vital for utilizing skyrmions as information carriers.

scholarly journals Manipulation of Skyrmion Motion Dynamics for Logical Device Application Mediated by Inhomogeneous Magnetic Anisotropy

Nanomaterials ◽  
2022 ◽  
Vol 12 (2) ◽  
pp. 278
Author(s):  
Jia-Qiang Lin ◽  
Ji-Pei Chen ◽  
Zhen-Yu Tan ◽  
Yuan Chen ◽  
Zhi-Feng Chen ◽  
...  
Keyword(s):  
Magnetic Anisotropy ◽  
High Mobility ◽  
Perpendicular Magnetic Anisotropy ◽  
Micromagnetic Simulation ◽  
Spintronic Devices ◽  
Potential Barriers ◽  
Device Application ◽  
Size And Shape ◽  
Magnetic Skyrmions ◽  
Motion Dynamics

Magnetic skyrmions are promising potential information carriers for future spintronic devices owing to their nanoscale size, non-volatility and high mobility. In this work, we demonstrate the controlled manipulation of skyrmion motion and its implementation in a new concept of racetrack logical device by introducing an inhomogeneous perpendicular magnetic anisotropy (PMA) via micromagnetic simulation. Here, the inhomogeneous PMA can be introduced by a capping nano-island that serves as a tunable potential barriers/well which can effectively modulate the size and shape of isolated skyrmion. Using the inhomogeneous PMA in skyrmion-based racetrack enables the manipulation of skyrmion motion behaviors, for instance, blocking, trapping or allowing passing the injected skyrmion. In addition, the skyrmion trapping operation can be further exploited in developing special designed racetrack devices with logic AND and NOT, wherein a set of logic AND operations can be realized via skyrmion–skyrmion repulsion between two skyrmions. These results indicate an effective method for tailoring the skyrmion structures and motion behaviors by using inhomogeneous PMA, which further provide a new pathway to all-electric skyrmion-based memory and logic devices.

scholarly journals Role of higher-order exchange interactions for skyrmion stability

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Souvik Paul ◽  
Soumyajyoti Haldar ◽  
Stephan von Malottki ◽  
Stefan Heinze
Keyword(s):  
Exchange Interactions ◽  
Ferromagnetic State ◽  
Higher Order ◽  
Spin Model ◽  
Spin Interaction ◽  
Spintronic Devices ◽  
The Stability ◽  
Magnetic Skyrmions ◽  
Moriya Interaction

Abstract Transition-metal interfaces and multilayers are a promising class of systems to realize nanometer-sized, stable magnetic skyrmions for future spintronic devices. For room temperature applications, it is crucial to understand the interactions which control the stability of isolated skyrmions. Typically, skyrmion properties are explained by the interplay of pair-wise exchange interactions, the Dzyaloshinskii-Moriya interaction and the magnetocrystalline anisotropy energy. Here, we demonstrate that higher-order exchange interactions – which have so far been neglected – can play a key role for the stability of skyrmions. We use an atomistic spin model parametrized from first-principles and compare three different ultrathin film systems. We consider all fourth-order exchange interactions and show that, in particular, the four-site four spin interaction has a large effect on the energy barrier preventing skyrmion and antiskyrmion collapse into the ferromagnetic state. Our work opens perspectives to stabilize topological spin structures even in the absence of Dzyaloshinskii-Moriya interaction.

scholarly journals The effect of flexural–torsional buckling on the stability of timber members: a case study

2021 ◽  
Vol 3 (6) ◽  
Author(s):  
Osama A. B. Hassan
Keyword(s):  
Axial Compression ◽  
Bending Moment ◽  
List Type ◽  
Torsional Buckling ◽  
Solution Methods ◽  
Simplified Solution ◽  
The Stability ◽  
Flexural Torsional Buckling ◽  
Building Engineering

Abstract This study investigates the stability of timber members subjected to simultaneously acting axial compression and bending moment, with possible risk for torsional and flexural–torsional buckling. This situation can occur in laterally supported members where one side of the member is braced but the other side is unbraced. In this case, the free side will buckle out of plane while the braced side will be prevented from torsional and flexural–torsional buckling. This problem can be evident for long members in timber-frame structures, which are subjected to high axial compression combined with bending moments in which the member is not sufficiently braced at both sides. This study is based on the design requirement stated in Eurocode 5. Solution methods discussed in this paper can be of interest within the framework of structural and building Engineering practices and education in which the stability of structural elements is investigated. Article Highlights This case study investigates some design situations where the timber member is not sufficiently braced. In this case, a stability problem associated with combined torsional buckling and flexural buckling can arise. The study shows that the torsional and/or flexural–torsional buckling of timber members can be important to control in order to fulfil the criteria of the stability of the member according to Eurocode 5 and help the structural engineer to achieve safer designs. The study investigates also a simplified solution to check the effect of flexural torsional buckling of laterally braced timber members.

scholarly journals Review of claudin proteins as potential biomarkers for necrotizing enterocolitis

2021 ◽  
Author(s):  
Victoria Griffiths ◽  
Niazy Al Assaf ◽  
Rizwan Khan
Keyword(s):  
Necrotizing Enterocolitis ◽  
Intestinal Permeability ◽  
Central Feature ◽  
Search Terms ◽  
Area Of Interest ◽  
Noninvasive Biomarker ◽  
Current Area ◽  
The Stability ◽  
Human Neonates ◽  
A Current

Abstract Background Claudin proteins are a component of tight junctions found in cell-cell adhesion complexes. A central feature of necrotizing enterocolitis (NEC) is intestinal permeability, with changes to claudin proteins potentially contributing to intestinal instability, inflammation, and the progression of NEC. A current area of interest is the development of a novel, noninvasive biomarker for the detection of NEC in neonates at risk of developing this disease, in order to reduce morbidity and mortality through earlier intervention. Aims This review aims to explore the relevance of claudin proteins in the pathophysiology of NEC and their potential usefulness as a biomarker. Methods This review was conducted using the search terms “claudin” + “necrotizing enterocolitis”, with 27 papers selected for review. Results Claudin proteins appear to have a role in the stability of the gut epithelium through the regulation of intestinal permeability, maturity, and inflammation. Formula feeding has been shown to promote inflammation and result in changes to claudin proteins, while breastfeeding and certain nutritional supplements lead to reduced inflammation and improved intestinal stability as demonstrated through changes to claudin protein expression. Preliminary studies in human neonates suggest that urinary claudin measurements may be used to predict the development of NEC. Conclusions Alterations to claudin proteins may reflect changes seen to intestinal permeability and inflammation in the context of NEC. Further research is necessary to understand the relevance of claudin proteins in the pathophysiology of NEC and their use as a biomarker.

scholarly journals Flexural-Torsional Vibration of Thin-Walled Beams Subjected to Combined Initial Axial Load and End Bending Moment: Application to the Design of Saw Tooth Blades

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Van Binh Phung ◽  
Anh Tuan Nguyen ◽  
Hoang Minh Dang ◽  
Thanh-Phong Dao ◽  
V. N. Duc
Keyword(s):  
Boundary Conditions ◽  
Axial Load ◽  
Stability Boundary ◽  
Bending Moment ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Rayleigh Method ◽  
Thin Walled ◽  
The Stability ◽  
Fixed End

The present paper analyzes the vibration issue of thin-walled beams under combined initial axial load and end moment in two cases with different boundary conditions, specifically the simply supported-end and the laterally fixed-end boundary conditions. The analytical expressions for the first natural frequencies of thin-walled beams were derived by two methods that are a method based on the existence of the roots theorem of differential equation systems and the Rayleigh method. In particular, the stability boundary of a beam can be determined directly from its first natural frequency expression. The analytical results are in good agreement with those from the finite element analysis software ANSYS Mechanical APDL. The research results obtained here are useful for those creating tooth blade designs of innovative frame saw machines.

Defects and Polytype Instabilities

2018 ◽  
Vol 924 ◽  
pp. 147-150
Author(s):  
Jörg Pezoldt ◽  
Andrei Alexandrovich Kalnin
Keyword(s):  
Long Range ◽  
Basal Plane ◽  
Partial Dislocation ◽  
Stacking Faults ◽  
Dislocation Loops ◽  
Elastic Fields ◽  
Basal Plane Dislocation ◽  
The Stability ◽  
Shockley Dislocation ◽  
Polytype Structure

A model based on the generation and recombination of defect was developed to describe the stability of stacking faults and basal plane dislocation loops in crystals with layered polytype structures. The stability of the defects configuration was analysed for stacking faults surrounded by Shockley and Frank partial dislocation as well as Shockley dislocation dipoles with long range elastic fields. This approach allows the qualitative prediction of defect subsystems in polytype structure in external fields.

Study of Dynamic Modes of Current Stabilization Systems of Powerful Electromagnets with Pulse-Width Modulation

2021 ◽  
Vol 22 (6) ◽  
pp. 313-320
Author(s):  
M. S. Lur’e ◽  
O. M. Lur’e ◽  
A. S. Frolov
Keyword(s):  
Pulse Width ◽  
Pulse Width Modulation ◽  
Functional Differential Equations ◽  
Original System ◽  
Nyquist Stability ◽  
Detailed Assessment ◽  
Functional Differential ◽  
The Stability ◽  
Automatic Systems ◽  
A Current

This study is devoted to the consideration of a method for assessing the stability of systems with pulse-width modulation, based on the linearization of its equivalent system with pulse-width modulation. An approximate study of the dynamic modes of operation of systems with pulse-width modulation, taking into account the stability for the system of automatic control of the supply current of electromagnets under the conditions of external and internal interference, is carried out. Variants of execution of schemes of pulse-width regulators for the power supply of an electromagnet based on a unipolar and bipolar element with pulse-width modulation are presented. The possibility of linearization of systems with pulse-width modulation for the subsequent detailed assessment of the stability of such systems is shown. The prospects of using functional differential equations for stability analysis of automatic systems with pulse-width modulation are shown. The frequency characteristics of an equivalent pulse system are analyzed using the example of a current stabilization system of high-power electromagnets with a pulse-width regulator, taking into account the replacement of the latitude modulation by the amplitude one. Based on the analysis of the resulting transfer function, which is a stable linearized equivalent open system, the ways of evaluating the stability of the original system with pulse-width modulation using the Nyquist stability criterion are proposed. The conclusion is made about the advantage of a system with PWM, in relation to a system with AIM, in terms of stability, and recommendations are given for the use of the obtained data in the analysis oftransients in such systems.

scholarly journals The mobility of positive ions in helium. Part I.―Helium ions

1931 ◽  
Vol 134 (823) ◽  
pp. 125-136 ◽  
Keyword(s):  
Direct Action ◽  
High Mobility ◽  
Ionic Clusters ◽  
Frequency Curve ◽  
Current Frequency ◽  
Positive Ions ◽  
Mobility Of Ions ◽  
Helium Gas ◽  
A Current ◽  
Α Particles

In a previous paper we gave an account of some experiments on the mobility of positive ions in helium gas. It was shown that minute traces of impurity profoundly affect the speed at which the charge is carried through the gas, so that very little significance can be attached to the values of the mobility of ions recorded in the literature. In particular we studied the behaviour of carefully purified helium gas when admitted at a pressure of 360 mm. of mercury into a baked-out apparatus. In our method of determining the mobility, a single group of ions gives rise to a peak in a current frequency curve, and it is easy to follow the changes produced by an impurity. Initially the ions in the helium had a high mobility and in one case we obtained a group with a mobility of the order of 17 cm./sec./volt/cm. at 760 mm. As the gas became contaminated by impurities gradually evolved from the glass walls and metal parts of the apparatus, peaks corresponding to groups of smaller mobility appeared, and eventually the charge was all carried by a group with mobility rather less than 8. The ions in these experiments were produced by means of α-particles from polonium. Traces of impurity in helium may affect the results in several ways. Firstly, they may lead to the formation of ionic clusters, particularly if the molecules of the impurity have a permanent dipole. In our experiments it seemed unlikely that molecules capable of forming clusters were present. Secondly, although with small concentrations of an impurity a negligible number of its ions will be produced by the direct action of the α-rays, they may be formed indirectly in either of the two following ways:—

The Lateral Buckling of Steel-Concrete Composite П-Beam

2008 ◽  
Vol 400-402 ◽  
pp. 287-293
Author(s):  
Li Zhong Jiang ◽  
Lin Lin Sun ◽  
Xing Li
Keyword(s):  
Bending Moment ◽  
Computing Methods ◽  
Lateral Buckling ◽  
Computing Model ◽  
Negative Moment ◽  
Numerical Computing ◽  
Negative Bending ◽  
The Stability ◽  
Simplified Calculation ◽  
Elastic Stage

Based on the theoretical analysis of steel-concrete composite П-beam’s lateral buckling, the computing model and simplified computing model on the stability of composite П-beams are brought forward. According to above two models, composite beam’s lateral buckling is studied in negative moment regions using the energy method, and the formulas which are used to calculate critical bending moment in negative moment regions in the elastic stage are deduced. Compared with other stability theories and methods, this paper represents the design correction and suggestion about the stability of composite П-beam in negative bending regions. Moreover, the simplified calculation method, which is used to compute the lateral critical buckling moment of steel-concrete composite П-beam loaded by equal-end moment, not only simplifies the computing process, the computing results also have the equivalent accuracy with numerical computing methods.

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