Effect Of Reorientation Research Articles

An Electrically Resistive Switching Nonvolatile Memory System Based on PEDOT:PSS

The current density–voltage (J–V) curves of poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) are examined at room temperature, which reveal nonlinear behavior and hysteresis loop‐like patterns. Herein, the potential of the material for nonvolatile applications requiring resistive random access memory (ReRAM) is demonstrated. The resistive switching effect is explained using a Schottky barrier and the space‐charge‐limited conduction model. Additionally, dielectric and electrical characteristics are analyzed in the frequency range from 20 Hz to 10 MHz. The impedance, electric modulus, dielectric loss tangent, and AC conductivity are explored through On‐ and Off‐states of resistive switching. A modified Debye function and Jonscher's power law are used for data fitting. The resistive switching memory behavior of PEDOT:PSS are studied using J–V and chemical impedance spectroscopy (CIS) measurements. The Cu/PEDOT:PSS/Cu sandwich‐type devices show bipolar switching behavior, and an equivalent circuit model based on the impedance spectra is proposed to describe the CIS response in both states. The switching process is attributed to the electrical‐field‐induced effect of dipolar reorientation on the electrical conductivity of PEDOT:PSS at grain boundaries.

Post-infarct evolution of ventricular and myocardial function

Adverse ventricular remodeling following acute myocardial infarction (MI) may induce ventricular dilation, fibrosis, and loss of global contractile function, possibly resulting in heart failure (HF). Understanding the relation between the time-dependent changes in material properties of the myocardium and the contractile function of the heart may further our understanding of the development of HF post-MI and guide the development of novel therapies. A finite element model of cardiac mechanics was used to model MI in a thick-walled truncated ellipsoidal geometry. Infarct core and border zone comprised 9.6 and 8.1% of the LV wall volume, respectively. Acute MI was modeled by inhibiting active stress generation. Chronic MI was modeled by the additional effect of infarct material stiffening, wall thinning and fiber reorientation. In acute MI, stroke work decreased by 25%. In the infarct core, fiber stress was reduced but fiber strain was increased, depending on the degree of infarct stiffening. Fiber work density was equal to zero. Healthy tissue adjacent to the infarct showed decreased work density depending on the degree of infarct stiffness and the orientation of the myofibers with respect to the infarct region. Thinning of the wall partially restored this loss in work density while the effects of fiber reorientation were minimal. We found that the relative loss in pump function in the infarcted heart exceeds the relative loss in healthy myocardial tissue due to impaired mechanical function in healthy tissue adjacent to the infarct. Infarct stiffening, wall thinning and fiber reorientation did not affect pump function but did affect the distribution of work density in tissue adjacent to the infarct.

Enhancement of Shock Absorption Using Hybrid SMA-MRF Damper by Complementary Operation

A hybrid damper concept is presented here using a combination of a Magnetorheological (MR) Fluid (MRF) and Shape Memory Alloy (SMA)-based energy dissipation. A demonstration is performed utilizing the shear operating mode of the MRF and the one-way effect of the SMA. The damping performance of different MRF-SMA configurations is investigated and the corresponding energy consumption is evaluated. We demonstrate that the operation of MRF and SMA dampers complement each other, compensating for each other’s weaknesses. In particular, the slow response from the MR damper is compensated by passive SMA damping using the pseudoplastic effect of martensite reorientation, which can dissipate a significant amount of shock energy at the beginning of the shock occurrence. The MR damper compensates for the incapability of the SMA to dampen subsequent vibrations as long as the magnetic field is applied. The presented hybrid SMA-MR damper demonstrates superior performance compared to individual dampers, allowing for up to five-fold reduction in energy consumption of the MR damper alone and thereby opening up the possibility of reducing the construction volume of the MR damper.

Layer-Dependent Interlayer Antiferromagnetic Spin Reorientation in Air-Stable Semiconductor CrSBr.

Magnetic van der Waals (vdW) materials possess versatile spin configurations stabilized in reduced dimensions. One magnetic order is the interlayer antiferromagnetism in A-type vdW antiferromagnet, which may be effectively modified by the magnetic field, stacking order, and thickness scaling. However, atomically revealing the interlayer spin orientation in the vdW antiferromagnet is highly challenging, because most of the material candidates exhibit an insulating ground state or instability in ambient conditions. Here, we report the layer-dependent interlayer antiferromagnetic spin reorientation in air-stable semiconductor CrSBr using magnetotransport characterization and first-principles calculations. We reveal an odd-even layer effect of interlayer spin reorientation, which originates from the competitions among interlayer exchange, magnetic anisotropy energy, and extra Zeeman energy of uncompensated magnetization. Furthermore, we quantitatively constructed the layer-dependent magnetic phase diagram with the help of a linear-chain model. Our work uncovers the layer-dependent interlayer antiferromagnetic spin reorientation engineered by magnetic field in the air-stable semiconductor.

Hysteresis Phenomena and the Effect of Reorientation in a Polymer-Liquid Crystal System Under the Influence of Laser Radiation and Uniaxial Deformation

The orientational structure in a polymer-liquid crystal thin film induced by uniaxial mechanical deformation has been studied. It is shown that the dependence of the deflection angle of the director of a nematic liquid crystal on the direction of the tensile force has a hysteresis region in which the orientation structure spontaneously changes from a state with positive torsion of the director to a state with negative torsion. It is established that the effect of modification of the hysteresis loop leads to an expansion of the hysteresis region and a decrease in the field at which orientation bistability appears.

Mechanical model for the deformation of the wood cell wall

Abstract The molecular mechanisms responsible for the deformation of wood, as well as the mechanical interaction of cell-wall components, such as cellulose, lignin and hemicelluloses, are not well understood. In a recently published experiment [1], we have shown that wood foils and single cells of compression wood of spruce (Picea abies [L.] Karst.) could deform permanently under tensile load via a stick and slip mechanism at the molecular level occurring during shear of the matrix between cellulose microfibrils. The shear originates from the fact that microfibrils are spiralling around the central lumen of the wood cell which can be considered as a hollow tube. During stretching, the microfibril angle between the cell axis and the direction of the cellulose was found to decrease in synchrotron X-ray diffraction experiments, giving rise to shear deformation of the matrix and to a recovery mechanism after irreversible deformation. The corresponding stick and slip mechanism is treated here in the framework of a simple mechanical model which shows that the cellulose fibril orientation might define slip planes for shear deformation, in analogy to the slip planes in single crystals as described by Schmid’s law. Moreover, the effect of fibril reorientation upon straining as well as the possibility of cell torsion are considered in the model and discussed with respect to experimental data.

Numerical investigation on the effect of depletion-induced stress reorientation on infill well hydraulic fracture propagation

Depletion-induced stress change causes the redistribution of stress field in reservoirs, which can lead to the reorientation of principal stresses. Stress reorientation has a direct impact on fracture propagation of infill wells. To understand the effect of stress reorientation on the propagation of infill well's fractures, an integrated simulation workflow that combines the reservoir flow calculation and the infill well hydraulic fracturing modeling is adopted. The reservoir simulation is computed to examine the relationship between the extent of stress reversal region and reservoir properties. Then, the hydraulic fracturing model considering the altered stress field for production is built to characterize the stress evolution of secondary fracturing. Numerical simulations show that stress reorientation may occur due to the decreasing of the horizontal stresses in an elliptical region around the parent well. Also, the initial stress difference is the driving factor for stress reorientation. However, the bottom hole pressure, permeability and other properties connected with fluid flow control timing of the stress reorientation. The decrease of the horizontal stresses around the parent well lead to asymmetrical propagation of a hydraulic fracture of the infill well. The study provides insights on understanding the influence of stress reorientation to the infill well fracturing treatment and interference between parent and infill wells.

Analysis of dielectric behavior of PVDF: PSF polyblends at lower frequency range from measurements of transient absorption and desorption currents

AbstractTransient current measurements were carried out for polyvinylidene fluoride:polysulfone (PVDF:PSF) blends films of different ratios under different polarizing fields and polarizing temperatures in absorption and desorption mode. The time‐dependent desorption current in polymer blend samples interprets the combined effect of dipole reorientation, space charge dissipation, and hopping of charge carriers. The activation energy has been calculated using the isochronal curve. Thermal activation behaviors of isochronal current in a specific temperature scale followed by a peak centered at about 120–160°C, have indicated the close correlation of transient currents with the dielectric loss peak. The presence of a dielectric loss peak for each polyblend concentration may be due to the existence of relaxing dipoles in the polyblend. With increasing concentration of PSF in the polyblend, this peak tends to shift toward the higher frequency range and suggests the speeding up of the dipolar relaxation process. The dielectric loss factor of polyblend thin films using transient study in absorption and desorption mode using applied step voltage f is related to Hamon's frequency (0.1/t).

Effect of spin reorientation on the dielectric and conductivity behavior of Ca2FeCoO5

Effect of spin reorientation on the dielectric and conductivity behavior of Ca2FeCoO5

Phase field study on the microscopic mechanism of grain size dependent cyclic degradation of super-elasticity and shape memory effect in nano-polycrystalline NiTi alloys

A non-isothermal and crystal plasticity based phase field model was established by incorporating various inelastic deformation mechanisms, i.e., martensite transformation, martensite reorientation, the austenitic plasticity caused by dislocation slipping, and the martensitic plasticity caused by dislocation slipping and deformation twinning, in which the deformation twinning mechanism was newly considered. The grain size (GS) effect of martensite transformation and reorientation was characterized by introducing a grain boundary energy, and the GS dependent resistances of dislocation slipping and deformation twinning were considered in the phase field simulation for the first time to describe the GS dependence of plastic deformation. Through a series of phase field simulations on the inelastic cyclic deformation of two-dimensional nano-polycrystalline NiTi shape memory alloy (SMA) systems, the microscopic mechanism of the GS dependent cyclic degradation of the super-elasticity (SE), one-way shape memory effect (OWSME) and stress-assisted two-way shape memory effect (SATWSME) of such alloy systems was newly clarified. The simulated results show that with decreasing the GS, the cyclic degradations of the SE and SATWSME are both mitigated gradually, while that of OWSME is aggravated first and then mitigated; when reducing the GS to 10 nm, almost no functional degradation occurs. Further analysis shows that the GS dependence of the cyclic degradations of SE and SATWSME can be attributed to that: as reducing the GS, the plastic deformation resistances gradually increase due to the Hall-Patch effect, and the GS effect of martensite transformation and reorientation reduces the deformation mismatch introduced in the polycrystalline system and leads to the decrease of local internal stress level (i.e., the driving force of plastic deformation decreases) (Factor I) during the cyclic deformation, therefore, the generation and accumulation of plastic deformation are inhibited. However, for the cyclic degradation of OWSME, besides Factor I, since the reorientation-induced plasticity is mainly concentrated on the grain boundaries and their nearby grain interiors, the increase of grain boundary proportion results in the concentration and accumulation of plastic deformation at more locations during the cyclic deformation (Factor II). The competition between Factors I and II makes the cyclic degradation of OWSME show a non-monotonic variation with the decrease of the GS .

US-CHINA TRADE WAR: IMPACT ON GLOBAL ECONOMY AND IMPLICATION FOR UKRAINE

The article analyzes the economic causes and consequences of the trade and economic war between the USA and PRC. The authors note that the trade war provoked the effects of trade reorientation and the emergence of beneficiaries among third countries, but, due to the transfer mechanism of global value chains, the losses to the world economy can largely overlap the overall short-term gain from such trade substitution. Particular attention is paid to the impact of the trade and economic war between the USA and PRC on the Ukrainian economy. It is substantiated that Ukraine has also acquired certain export opportunities due to a decrease in the American share in the Chinese market. So, the extremely dynamic growth of Ukrainian exports to China, which has been observed in recent years, testifies to the above effect of reorientation and replacement of trade flows.

ТОРГОВЕЛЬНА ВІЙНА МІЖ США І КНР: ВПЛИВ НА СВІТОВУ ЕКОНОМІКУ ТА НАСЛІДКИ ДЛЯ УКРАЇНИ

The article analyzes the economic causes and consequences of the trade and economic war between the USA and PRC. The chronology of the introduction of mutual trade barriers by these countries and a temporary compromise in the form of the first round of the Trade Agreement are considered. Based on the systematisation of estimates of the effects of additional trade tariffs, a contradictory (albeit asymmetric) effect on economic growth, investment and employment in these countries is shown, as well as a predicted increase in the overall negative effect for a significant number of countries in the medium term. The main scenarios of the possible development of trade and economic relations between the United States and China are considered. The authors note that the trade war provoked the effects of trade reorientation and the emergence of beneficiaries among third countries, but, due to the transfer mechanism of global value chains, the losses to the world economy can largely overlap the overall short-term gain from such trade substitution. It has been shown that any trade relocation takes time and has additional costs. Alternative suppliers may not have the same transactional supply efficiency. Particular attention is paid to the impact of the trade and economic war between the USA and PRC on the Ukrainian economy. It is substantiated that Ukraine has also acquired certain export opportunities due to a decrease in the American share in the Chinese market. So, the extremely dynamic growth of Ukrainian exports to China, which has been observed in recent years, testifies to the above effect of reorientation and replacement of trade flows. But, at the same time, the deterioration of world economic dynamics as a result of the trade and economic war increases the overall risks for the Ukrainian economy, especially in the medium term. In the context of the current economic policy of Ukraine, the issue of maximizing the utilization of industrial export opportunities to China and expanding the export of goods with higher added value remains important.

Loading influence on the corrosion assessment during stress-induced martensite reorientation in nickel-titanium SMA

The effect of stress-induced martensite reorientation on the corrosion behavior of a nickel-titanium (NiTi) shape memory alloy (SMA) was characterized by mechanical-electrochemical techniques. This martensite reorientation influenced the passive state of NiTi SMA. These passive to active state transitions could be sensed by the global interfacial electrochemical measurements, such as electrochemical impedance spectroscopy (EIS), open circuit potential (OCP) and linear polarization resistance (LPR) methods. The increase in the loading when exposed to a corrosive environment resulted in the breakdown of the passive layer. A later repassivation stage was reached due to the formation rate becoming more dominant than the breakdown rate during loading conditions. The integration of the mechanical loading by tensile testing, strain distribution by digital image correlation (DIC) and electrochemical methods by OCP and EIS, characterized and detected the influence of the mechanical effect in the corrosion assessment and interfacial mechanisms.

Dipole reorientation and local density of optical states influence the emission of light-emitting electrochemical cells.

Herein, we analyze the temporal evolution of the electroluminescence of light-emitting electrochemical cells (LECs), a thin-film light-emitting device, in order to maximize the luminous power radiated by these devices. A careful analysis of the spectral and angular distribution of the emission of LECs fabricated under the same experimental conditions allows describing the dynamics of the spatial region from which LECs emit, i.e. the generation zone, as bias is applied. This effect is mediated by dipole reorientation within such an emissive region and its optical environment, since its spatial drift yields a different interplay between the intrinsic emission of the emitters and the local density of optical states of the system. Our results demonstrate that engineering the optical environment in thin-film light-emitting devices is key to maximize their brightness.

Effect of anion reorientation on proton mobility in the solid acids family CsHyXO4 (X = S, P, Se, y = 1, 2) from ab initio molecular dynamics simulations.

The high temperature phases of the solid acids CsHSeO4, CsHSO4 and CsH2PO4 show extraordinary high proton conductivities, while the low temperature phases do not conduct protons at all. We systematically investigate proton dynamics in the low and high temperature phases of these compounds by means of ab initio molecular dynamics simulations in order to develop a general picture of the proton transfer mechanism. For all of these compounds, proton conduction follows a Grotthuss mechanism via a combined proton transfer and subsequent structural reorientation of the environment. We demonstrate that the drastically reduced conductivity of the low temperature phases is caused by a highly ordered, rigid hydrogen bond network, while efficient long range proton transfer in the high temperature phases is enabled by the interplay of high proton transfer rates and frequent anion reorientation. Furthermore, we present a simple descriptor for the quantitative prediction of the diffusion coefficient within the solid acids family. As a side result, we show that the rate of the most elementary proton hopping reaction depends on the heavy-atom configuration of the nearest atoms in a ubiquitous manner, and is in turn almost independent from the global nature of the compound, i.e. whether it is organic or inorganic, ordered or disordered.

Adsorption of hexacontane on atomically-flat surfaces of graphite and Au(111)

We report the results of comparative study of monolayer films of n-hexacontane (C60H122) adsorbed on atomically flat graphite and reconstructed Au(111) surfaces. Scanning tunneling microscopy (STM) revealed polymorphism in monolayer on Au(111) surface. It was shown that under the same conditions of deposition hexacontane molecules may form two packing structures. The effect of collective reorientation of molecules was revealed on graphite surface. Obtained results are explained in terms of commensurability between alkyl chain and substrate.

Effects of Reorientation of Graphene Platelets (GPLs) on Young's Modulus of Polymer Nanocomposites under Uni-Axial Stretching.

The orientation of reinforcement fillers in composites plays a vital role in their mechanical properties. This paper employs the Mori–Tanaka micromechanics model, incorporating the effect of stretching-induced reorientation of graphene platelets (GPL), to predict Young’s modulus of GPL/polymer nanocomposites. Subjected to uni-axial stretching, dispersion of GPLs is described by an orientation distribution function (ODF) in terms of a stretching strain and two Euler angles. The ODF shows that GPLs tend to realign along the stretching direction. Such realignment is enhanced at a higher Poisson’s ratio and under a larger stretching strain. It is found that the out-of-plane Young’s modulus of GPL nanofillers has a limited effect on the overall Young’s modulus of the composites. With an increase in stretching strain and GPL concentration, Young’s modulus increases in the stretching direction while it decreases in the transverse direction. A larger aspect-ratio of GPLs with fewer layers is preferred for enhancing Young’s modulus in the stretching direction, but it is unfavorable in the transverse direction. Moreover, Young’s moduli in both longitudinal and transverse directions are more sensitive to the reorientation of smaller-sized GPLs with a greater concentration in the composites.

Dynamic Response of Graphitic Flakes in Nematic Liquid Crystals: Confinement and Host Effect.

Electric field-induced reorientation of suspended graphitic (GP) flakes and its relaxation back to the original state in a nematic liquid crystal (NLC) host are of interest not only in academia, but also in industrial applications, such as polarizer-free and optical film-free displays, and electro-optic light modulators. As the phenomenon has been demonstrated by thorough observation, the detailed study of the physical properties of the host NLC (the magnitude of dielectric anisotropy, elastic constants, and rotational viscosity), the size of the GP flakes, and cell thickness, are urgently required to be explored and investigated. Here, we demonstrate that the response time of GP flakes reorientation associated with an NLC host can be effectively enhanced by controlling the physical properties. In a vertical field-on state, higher dielectric anisotropy and higher elasticity of NLC give rise to quicker reorientation of the GP flakes (switching from planar to vertical alignment) due to the field-induced coupling effect of interfacial Maxwell-Wagner polarization and NLC reorientation. In a field off-state, lower rotational viscosity of NLC and lower cell thickness can help to reduce the decay time of GP flakes reoriented from vertical to planar alignment. This is mainly attributed to strong coupling between GP flakes and NLC originating from the strong π-π interaction between benzene rings in the honeycomb-like graphene structure and in NLC molecules. The high-uniformity of reoriented GP flakes exhibits a possibility of new light modulation with a relatively faster response time in the switching process and, thus, it can show potential application in field-induced memory and modulation devices.

Методика выбора скважин-кандидатов для проведения повторного гидроразрыва пласта на основе эффекта переориентации трещины

Методика выбора скважин-кандидатов для проведения повторного гидроразрыва пласта на основе эффекта переориентации трещины

Hot deformation characterization of lamellar Ti-43Al-2Si alloy fabricated by cold crucible continuous casting

In order to investigate the hot deformation behavior of lamellar Ti-43Al-2Si (at%, similarly hereinafter) alloy with equiaxed colonies prepared by cold crucible continuous casting, the isothermal compression tests were carried out at different temperatures in the range of 1100–1250 °C using the strain rates between 0.001 s−1 and 1 s−1 with true strain of 0.8. A constitutive equation at elevated temperature and three-dimensional processing map of this alloy were established based on flow stress data at different temperatures and strain rates. The microstructures depended on deformation condition were observed by optical microscope (OM), backscattered electron (BSE) and electron back-scattered diffraction (EBSD). It was found that the deformation activation energy (Q) varied with the deformation temperature and strain rate, and average value was 451.15 kJ/mol which was much larger than that of the powder metallurgy TiAl-based alloy but smaller than that of the well directionally solidified (DS) microstructure TiAl-based alloy. Based on the processing map, the appropriate hot working domain of this alloy without deformed cracks was determined to be within the temperature window from 1150 °C to 1250 °C and in the strain rate range of 0.001–0.01 s−1. The flow softening feature of the present alloy during deformation was noted and caused by synergetic effect of dynamic recrystallization (DRX), globularization and reorientation of lamellae. In addition, the Zener-Hollomom parameter played a key role on the DRX process.