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The response of crystalline materials to elasto-plastic cyclic loading is reviewed and analyzed. The important parameters characterizing the cyclic plastic response of single crystals, polycrystals, and multiphase materials are presented and related to the internal dislocation structure. Cyclic plastic strain localization is shown to be the characteristic feature of cyclic plastic straining which leads to surface relief formation and fatigue crack initiation. Recent models of fatigue crack initiation are presented. The mechanisms and kinetics of early crack growth are reviewed and the analysis of the relation of the crack growth kinetics and fatigue life curves is suggested.

Background Abnormal glutamatergic neurotransmission in the primary motor cortex (M1) contributes to Parkinson's disease (PD) pathophysiology and is related to l -dopa-induced dyskinesia (LID). We previously showed that short-term treatment with safinamide, a monoamine oxidase type-B inhibitor with anti-glutamatergic properties, improves abnormally enhanced short-interval intracortical facilitation (SICF) in PD patients. Objective To examine whether a long-term SICF modulation has beneficial effects on clinical measures, including LID severity, and whether these changes parallel improvement in cortical plasticity mechanisms in PD. Methods We tested SICF in patients with and without LID before (S0) and after short- (14 days - S1) and long-term (12 months - S2) treatment with safinamide 100 mg/day. Possible changes in M1 plasticity were assessed using intermittent theta-burst stimulation (iTBS). Finally, we correlated safinamide-related neurophysiological changes with modifications in clinical scores. Results SICF was enhanced at S0, and prominently in patients with LID. Safinamide normalized SICF at S1, and this effect persisted at S2. Impaired iTBS-induced plasticity was present at S0 and safinamide restored this alteration at S2. There was a significant correlation between the degree of SICF and the amount of iTBS-induced plasticity at S0 and S2. In patients with LID, the degree of SICF at S0 and S2 correlated with long-term changes in LID severity. Conclusions Altered SICF contributes to M1 plasticity impairment in PD. Both SICF and M1 plasticity improve after long-term treatment with safinamide. The abnormality in SICF-related glutamatergic circuits plays a role in LID pathophysiology, and its long-term modulation may prevent LID worsening over time.

A novel model called Instinct Plasticity Echo State Network with New Weights Selection Method, which is Optimized by Genetic Algorithm, is proposed (IP-NESN-GA). There are three proposed methods that are employed in the conventional ESN. New weights selection method provides a novel approach to replace the random weights of ESN, which obtains much better performance than the conventional ESN. At the same time, Instinct Plasticity is successfully applied in ESN, which enhances the connection among reservoir states and increase the accuracy. Finally, Genetic Algorithm is applied to seek the most suitable parameters. The detecting ability of our proposed model is assessed on two kinds of distinct grammatical constructions data. It not only performs significantly better than the baselines in the meaning error and sentence error, but it also visualizes the expected probabilities for each of the possible thematic roles.

Halide perovskites, fascinating memristive materials owing to mixed ionic-electronic conductivity, have been attracting great attention as artificial synapses recently. However, polycrystalline nature in thin film form and instability under ambient air hamper them to be implemented in demonstrating reliable neuromorphic devices. Here, we successfully fabricated vertically aligned 2D halide perovskite films (V-HPs) for active layers of artificial synapses, showing moisture stability for several months. Unlike random-oriented HPs, which exhibit negligible current hysteresis, the V-HPs possess multilevel analog memristive characteristics, programmable potentiation and depression with distinguished multi-states, long-short-term plasticity, paired-pulse facilitation, and even spike-timing-dependent plasticity. Furthermore, high classification accuracy is obtained with implementation in deep neural networks. These remarkable improvements are attributed to the vertically well-aligned lead iodide octahedra acting as the ion transport channel, confirmed by first-principles calculations. This study paves the way for understanding HPs nanophysics and demonstrating their potential utility in neuromorphic computing systems.

Neural networks with a large number of parameters are prone to overfitting problems when trained on a relatively small training set. Introducing weight penalties of regularization is a promising technique for solving this problem. Taking inspiration from the dynamic plasticity of dendritic spines, which plays an important role in the maintenance of memory, this letter proposes a brain-inspired developmental neural network based on dendritic spine dynamics (BDNN-dsd). The dynamic structure changes of dendritic spines include appearing, enlarging, shrinking, and disappearing. Such spine plasticity depends on synaptic activity and can be modulated by experiences—in particular, long-lasting synaptic enhancement/suppression (LTP/LTD), coupled with synapse formation (or enlargement)/elimination (or shrinkage), respectively. Subsequently, spine density characterizes an approximate estimate of the total number of synapses between neurons. Motivated by this, we constrain the weight to a tunable bound that can be adaptively modulated based on synaptic activity. Dynamic weight bound could limit the relatively redundant synapses and facilitate the contributing synapses. Extensive experiments demonstrate the effectiveness of our method on classification tasks of different complexity with the MNIST, Fashion MNIST, and CIFAR-10 data sets. Furthermore, compared to dropout and L2 regularization algorithms, our method can improve the network convergence rate and classification performance even for a compact network.

Two-dimensional (2D) crystals of conjugated polymers (2DCCPs) have attracted significant attention in the past few decades due to their superior and intriguing optoelectronic properties. With the increase in brain-inspired neuromorphic computing, 2DCCPs have also been employed in the construction of synaptic devices because they offer clear advantages of easy integration, high stability, long–range order and no biological rejection. However, pursuing controllable strategies to obtain high-quality and large-scale 2DCCPs remains a challenge on account of their intrinsic complex structures. Herein, we present a universal methodology to grow centimeter-scale 2DCCPs in a controlled manner within minutes by selecting an appropriate growth-assisting solvent and surfactant. The thickness of the as-produced 2DCCPs was down to two molecular layers. The photonic synaptic transistors based on the as-grown 2DCCPs could perform typical synaptic functions, including short-term plasticity, paired-pulse facilitation, long-term plasticity and spike intensity-dependent plasticity. The transistor was also proven to have potential application as a high-pass filter. This methodology shows great potential to be expanded to many other polymer systems and opens new pathways for large-area integrated wireless communication systems and artificial visual systems.

Huntington’s disease (HD) mouse models suggest that cardiovascular exercise may enhance neuroplasticity and delay disease signs, however, the effects of exercise on neuroplasticity in people with HD are unknown. Using a repeated-measures experimental design, we compared the effects of a single bout of high-intensity exercise, moderate-intensity exercise, or rest, on motor cortex synaptic plasticity in 14 HD CAG-expanded participants (9 premanifest & 5 early manifest) and 20 CAG-healthy control participants, using transcranial magnetic stimulation. Measures of cortico-motor excitability, short-interval intracortical inhibition and intracortical facilitation were obtained before and after a 20-minute bout of either high-intensity interval exercise, moderate-intensity continuous exercise, or rest, and again after intermittent theta burst stimulation (iTBS). HD participants showed less inhibition at baseline compared to controls. Whereas the control group showed increased excitability and facilitation following high-intensity exercise and iTBS, the HD group showed no differences in neuroplasticity responses following either exercise intensity or rest, with follow-up Bayesian analyses providing consistent evidence that these effects were absent in the HD group. These findings indicate that exercise-induced synaptic plasticity mechanisms in response to acute exercise may be attenuated in HD, and demonstrate the need for future research to further investigate exercise and plasticity mechanisms in people with HD.

As a part of round robin analysis to develop a finite element elastic-plastic seismic analysis procedure for nuclear safety class 1 components, a series of parametric analyses was carried out on the simulated pressurizer surge line system model to investigate sensitivity of the analysis results to finite element analysis variables. The analysis on the surge line system model considered dynamic effect due to the seismic load corresponding to PGA 0.6 g and elastic-plastic material behavior based on the Chaboche combined hardening model. From the parametric analysis results, it was found that strains such as accumulated equivalent plastic strain and equivalent plastic strain are more sensitive to the analysis variables than von Mises effect stress. The parametric analysis results also identified that finite element density and ovalization option in the elbow elements have more significant effect on the analysis results than the other variables.

The seismic pullout strength of the cast-in-place anchor bolts embedded in the plain concrete is a function of the accumulated tensile damage during the load reversals. The present study deals with the seismic tension analysis of the cast-in-place anchor bolts considering the resultant stiffness and strength degradation phenomena. In this way, a nonlinear fracture-based damage plasticity model is developed and implemented in the Abaqus code. Primarily, the validity and accuracy of the developed constitutive model are assessed based on the existing pullout tests. Then, the developed framework is utilized to assess the seismic pullout response of the anchor bolts with a low embedded depth-to-diameter ratio ( h e d b ⩽ 10 ) . Assumed parametric study space contains several plain slabs with various anchor diameters, embedded depths, and compressive concrete strengths. Based on the observations, the seismic load results in significant degradation of stiffness (damage) and pullout strength. The seismic-induced damage is increased when the compressive concrete strength and the embedded anchor depth are increased. However, the slender anchors undergo lower damage than the stubby ones. The size effect phenomenon in the concrete material leads to distinct behavior of the cast-in-place anchor bolts with various embedded depth-to-diameter ratios. Considering the crack patterns of the modeled slabs, the degraded stiffness state at the end of the seismic loading step increases the inclination angle of the pullout cracks during the monotonic loading step. The inclination angle of the cracks is detected to be a function of the embedded depth-to-diameter ratio.

This paper presents the two uncoupled elastoplastic-damage models; uncoupled Lemaitre’s and Vaz’s damage models. The two models are implemented into the finite element ABAQUS software using user routine UMAT to analyze and predict damage and damage evolution. In the context of von-Mises yield criteria, damage variable and fracture indicator are predicted, in addition to the von-Mises stress and the effective plastic strain. Both the elastoplastic tangent operator and the return mapping procedure are formulated using the consistent formulation. Two cases have been analyzed; the first one is an axisymmetric notched bar, while the second case is a plane strain doubled notched plate. In addition to the aforementioned predictions, a parametric study is carried out to explore the effect of the damage denominator and damage exponent on the damage behavior. It is concluded that the two models succeeded in the prediction of the point of fracture, while the uncoupled Lemaitre's damage model gives a more efficient description of the damage band.

The aim of this paper is to propose a demountable shear wall (DSW) system for multistory precast concrete buildings. For this purpose, instead of a large wall panel, several slender walls are used by connecting to adjacent beams. To evaluate the efficiency of the DSW system, nonlinear cyclic and time history analyses are performed on eighteen 4-, 8- and 12-story models, including three conventional shear wall models and fifteen DSW models with various wall numbers. The results indicate that for DSW system, when using more walls with a smaller width, the structural deformation tends from flexural-type to almost shear-type. This result prevents the plastic strain from concentrating on the columns and walls of the first story and causes the damage to be uniformly distributed on the walls of all stories. The DSW models exhibit hysteretic behavior without significant strength degradation at high drift levels. Also, DSW models with more walls, while increasing the ductility factor (up to 30%) and creating a more uniform distribution of drifts, reveal less value of maximum floor acceleration (up to 48%) and story shear (up to 53%), compared to conventional shear wall models.

In order to study the mechanical mechanism of the new tension–compression composite anchor, the finite element software is used to establish the numerical calculation model of the new composite anchor, and the numerical drawing test is carried out. Through numerical experiments, the optimal position range of the bolt bearing plate is obtained, and the axial load and shear stress distribution of the bolt were analyzed. The results show that the ultimate pullout force of the new tension–compression composite bolt increases first and then decreases with the movement of the bearing plate position, and the optimal position is at the position where the length ratio of the tension–compression anchorage section is 3:4. At the same time, the study shows that the optimal position of the bearing plate has an optimal position interval. The ultimate uplift capacity of the new tension–compression composite anchor is 118.6% and 94% higher than that of the traditional tension anchor and pressure anchor, respectively. The shear stress distribution of the new tension–compression composite anchor is more uniform. The peak shear stress first appears at the bearing plate and begins to transfer to both sides of the bearing plate with the increase in the drawing force, which increases first and then decreases. Since the new tension–compression composite anchorage section is in an unbonded state, the axial load of the bolt is always equal to the drawing force. The axial force distribution of the tensile anchorage section is similar to that of the traditional tensile bolt and decreases exponentially along the axial direction of the bolt. Under the action of ultimate drawing force, the plastic zone distribution of the new tension–compression composite anchor is different from that of the traditional tension anchor and the traditional pressure anchor. The plastic zone first appears in the position of the bearing plate and begins to transfer to both sides of the bearing plate with the increase in the drawing force. When the plastic strain exceeds the allowable strain of the interface, the bolt pulls out from the anchor hole and the bolt support structure fails.

The science and technology related with light has revolutionized modern society, and understanding the effects of light on semiconducting materials has become crucial to current science and technology. Although much research has been done on the effects of light on the electronic and optical properties of materials, the effects of light on the mechanical properties of materials are not well understood. It was recently found that extraordinarily large plasticity appears in bulk compression of single-crystal ZnS in complete darkness even at room-temperature. This is believed to be due to the less interactions between dislocations and photo-excited electrons and/or holes. However, methods for evaluating dislocation behavior in such semiconductors with small dimensions under a particular light condition had not been well established. Here we show a new nanoindentation method that incorporates well designed lighting system for exploring dislocation behavior depending on the light conditions in advanced semiconductors. We used single-crystal ZnS as a model material because its bulk deformation behavior has been well investigated. It is confirmed that the decrease of dislocation mobility with light observed in conventional bulk deformation tests can be understood even by the nanoindentation tests at room-temperature. It is remarkable that we experimentally demonstrate that dislocation mobility appears to be more sensitive to light exposure than dislocation nucleation.

The “puzzle” of emotional plasticity concerns making sense of two conflicting bodies of evidence: evidence that emotions often appear modular in key respects, and evidence that our emotions also of...

BackgroundRepetitive transcranial magnetic stimulation (rTMS) is a non-invasive tool commonly used to drive neural plasticity in the young adult and aged brain. Recent data from mouse models have shown that even at subthreshold intensities (0.12 Tesla), rTMS can drive neuronal and glial plasticity in the motor cortex. However, the physiological mechanisms underlying subthreshold rTMS induced plasticity and whether these are altered with normal ageing are unclear.ObjectiveTo assess the effect of subthreshold rTMS, using the intermittent theta burst stimulation (iTBS) protocol on structural synaptic plasticity in the mouse motor cortex of young and aged mice.MethodsLongitudinal in vivo 2-photon microscopy was used to measure changes to the structural plasticity of pyramidal neuron dendritic spines in the motor cortex following a single train of subthreshold rTMS (in young adult and aged animals) or the same rTMS train administered on 4 consecutive days (in young adult animals only). Data were analysed with Bayesian hierarchical generalized linear regression models and interpreted with the aid of Bayes Factors (BF).ResultsWe found strong evidence (BF>10) that subthreshold rTMS altered the rate of dendritic spine losses and gains, dependent on the number of stimulation sessions and that a single session of subthreshold rTMS was effective in driving structural synaptic plasticity in both young adult and aged mice.ConclusionThese findings provide further evidence that rTMS drives synaptic plasticity in the brain and uncovers structural synaptic plasticity as a key mechanism of subthreshold rTMS induced plasticity.

Objective: Some of the neurological diseases cause morphologic changes in the striatal neurons. Medial forebrain bundle (MFB)lesion is a commonly used method to produce a Parkinsonian model rat. Melatonin is a hormone which exerts a neuroprotectiveeffect on the neurons. The aim of this study is to investigate the effect of melatonin on the dendritic morphology of striatal mediumspiny neurons (MSNs) in rats with MFB lesion.Materials and Methods: Twelve male Wistar albino rats were given saline injections into the MFB and divided into sedentary andtreatment groups. The treatment group was administered a 10 mg/kg dose of melatonin intraperitoneally for 30 days. The lesionwas confirmed histologically by Nissl staining. Golgi staining technique was applied to observe neuronal morphology. Neuronalstructures were analysed from three-dimensional images by Neurolucida (MBF Bioscience) software.Results: The MFB lesion caused a reduction in the total dendritic length and in the number of dendritic endings. The melatoninenhanced the number of dendritic endings compared to the sedentary group. The melatonin led to an increase in the total spinedensity, spine densities of thin and mushroom types.Conclusion: Melatonin improved the dendritic degeneration due to MFB lesion.

Studies with transcranial magnetic stimulation (TMS) show that both acute and long-term exercise can influence TMS-induced plasticity within primary motor cortex (M1). However, it remains unclear how regular exercise influences skill training-induced M1 plasticity and motor skill acquisition. This study aimed to investigate whether skill training-induced plasticity and motor skill learning is modified in endurance-trained cyclists. In 16 endurance-trained cyclists (24.4 yrs; 4 female) and 17 sedentary individuals (23.9 yrs; 4 female), TMS was applied in 2 separate sessions: one targeting a hand muscle not directly involved in habitual exercise and one targeting a leg muscle that was regularly trained. Single- and paired-pulse TMS was used to assess M1 and intracortical excitability in both groups before and after learning a sequential visuomotor isometric task performed with the upper (pinch task) and lower (ankle dorsiflexion) limb. Endurance-trained cyclists displayed greater movement times (slower movement) compared with the sedentary group for both upper and lower limbs (all P 0.05). Furthermore, endurance-trained cyclists demonstrated a greater increase in M1 excitability and reduced modulation of intracortical facilitation in resting muscles of upper and lower limbs after visuomotor skill learning (all P

This study assesses experimentally and numerically the cyclic loading response of reinforced concrete beams with web openings and shear-flexure strengthened carbon fiber reinforced polymer (CFRP) sheets using an external bonded technique. The influence of the beams on the reverse cyclic effect including the parameters of the hysteretic failure modes, stiffness degradation performance, energy dissipation, pinching width ratio, and ductility, are discussed. A numerical approach is employed to evaluate an innovative rectangular web opening and external bonding strengthening with an FRP sheet. A numerical model was used to validate the results of the tested specimens. Appropriate simulation techniques, which characterize the properties of constitutive materials, and a concrete damaged plasticity model were used for modeling development. Further, they are incorporated to apply models with new parameters. The results indicated that the use of CFRP as a strengthening system around the opening can significantly improve the overall stiffness capacity and beam behavior under cyclic loading. In particular, the increase in the load-carrying capacity over the control beam reached 63.43% for the beam with an opening in the shear zone and 73% for that with an opening in the flexural zone. The load–displacement hysteresis loops of the tested specimens were compared with those simulated by numerical models. Good convergence between the predicted and measured results was observed under all cyclic loading rates.

This study investigated the capacity of finite element modelling (FEM) approaches to predict the experimentally obtained behaviour of concrete-filled spiral-welded stainless-steel tube (CF-SWSST) short and long columns. Using the ABAQUS software, FEM was carried out of 24 CF-SWSST column tests. Nominal outside diameter to thickness ratios, effective length to diameter ratios and load eccentricity to diameter ratios equal to 51–114.5, 4.5–12.0, and 0–0.4 had been considered for the tests that were modelled. The distinct spiral weld seam geometry of the SWSST was explicitly considered in the FEM. Widely reported and accepted FEM modelling approaches and material models were adopted for this work. The concrete damaged plasticity model was utilised for the concrete core, while the stress–strain behaviour of stainless-steel was modelled using a modified Ramberg-Osgood relationship. On average, the capacities predicted by the FEM for the CF-SWSST columns were found to be non-conservative. The non-conservativeness was higher for specimens under concentric axial loading and increased with column and section slenderness. The actual to predicted capacity ratios were much closer to 1.0 for eccentrically loaded CF-SWSST columns, with conservative capacities predicted for eccentrically loaded specimens with the smallest section slenderness. For load eccentricity to diameter ratios of 0.15 and 0.4, there was negligible difference in the prediction conservativeness. Compared to analogous concrete-filled spiral-welded mild-steel tube columns, the FEM predictions obtained for the CF-SWSST columns were notably less conservative. This suggested that separate material constitutive models may be warranted for the FEM of CF-SWSSTs compared to their mild-steel counterparts. For the modelled eccentrically loaded specimens, the FEM predicted globally flexurally deformed states which agreed with those obtained experimentally, though the local buckling patterns were not replicated. In addition, the FEM qualitatively captured the experimentally obtained bending stiffness and strain variations. A modelling sensitivity study found that the FEM results were effectively equivalent even when the SWSSTs were modelled as plain seamless tubes.

Advent of concrete damaged plasticity material models has drastically improved the accuracy in predicting the structural response of concrete structural elements using finite element Analysis. However, exploration of the accuracy of this method in analysing complex concrete forms is scanty. Gravity Beams, a term coined in this investigation, are those beams in which gravity is used to design the topology of beam form conjointly with the novel manufacturing strategy ‘Fabric Formwork’. In this investigation these beam forms were numerically analysed using prevalent material and damage models. Numerical structural response was evaluated using these models and compared to experimental response. It was deduced from the comparative evaluation that numerical models closely predict the structural response of gravity beams. Moreover, dissimilarity analysis revealed that the diversion of the results was due the shape error between Modelled gravity beams, which were used for numerical analysis, and actual 3D scanned beams. It was deduced after analysis of experimental and numerical failure patterns that local imperfections also play a major role in the deviation in the numerical model. Furthermore, cross-sectional proportion ratio (CPR) was also introduced to give a numerical identity to gravity beams. This ratio was used to frame a parametric comparison of gravity beams and the corresponding structural response, to explore the parametric dependency.

In this paper, 3D nonlinear finite element analyses (FEA) were conducted using the ABAQUS program to investigate the openings’ influences on voided slabs’ structural behaviors. In these FEAs, the quasi-static solution was adopted, and the concrete behavior was represented by the concrete damaged plasticity model (CDPM). CDPM parameters were calibrated versus voided slab's test results taken from the literature. The calibrated FEA model's efficiency to describe the opening effect was then verified by matching with external experimental observations of conventional slabs with openings. Finally, a parametric study was implemented, in which eleven slabs’ models with or without openings were contrasted. The considered variables were the size, shape, arrangement, and location of openings. The FEA results showed that the openings adversely affected the mechanical properties of voided slabs, and they became more influential as the interrupted reinforcement bars due to openings increased. However, constructing the opening near the support far away from the zone of high flexural stresses resulted in slight deteriorations in the strength, stiffness, and toughness of voided slabs.

Objective To test the hypothesis that intermittent theta burst stimulation (iTBS) variability depends on the ability to engage specific neurons in the primary motor cortex (M1). Methods In a sham-controlled interventional study on 31 healthy volunteers, we used concomitant transcranial magnetic stimulation (TMS) and electroencephalography (EEG). We compared baseline motor evoked potentials (MEPs), M1 iTBS-evoked EEG oscillations, and resting-state EEG (rsEEG) between subjects who did and did not show MEP facilitation following iTBS. We also investigated whether baseline MEP and iTBS-evoked EEG oscillations could explain inter and intraindividual variability in iTBS aftereffects. Results The facilitation group had smaller baseline MEPs than the no-facilitation group and showed more iTBS-evoked EEG oscillation synchronization in the alpha and beta frequency bands. Resting-state EEG power was similar between groups and iTBS had a similar non-significant effect on rsEEG in both groups. Baseline MEP amplitude and beta iTBS-evoked EEG oscillation power explained both inter and intraindividual variability in MEP modulation following iTBS. Conclusions The results show that variability in iTBS-associated plasticity depends on baseline corticospinal excitability and on the ability of iTBS to engage M1 beta oscillations. Significance These observations can be used to optimize iTBS investigational and therapeutic applications.

Nanostructures on GaAs have drawn significant attention because of their applications in photodetectors, photoemitter devices and emerging quantum devices. However, how to machine nanostructures with a desirable machined depth on GaAs is still a challenge. Atomic force microscopy (AFM) tip-based nanoscratching technique has been proven as a useful method to machine nanostructures. In this study, an AFM tip-based nanoscratching approach was used to machine nanochannels on GaAs. To predict the machined depth, a theoretical model was established during the removal of material in ductile regime. Furthermore, the influence of the machined depth on the material removal mechanism and the subsurface damage were also studied. The results demonstrated that materials were removed by ploughing and cutting respectively for the two sides of the channel when the machined depth was smaller than 11 nm. However, if the machined depth is larger than 11 nm, the removal of material for both sides of the channel was dominated by cutting. Transmission electron microscope analysis revealed the plasticity of the sample induced by nanoscratching was caused by stacking faults and dislocations, accompanied with nanocrystallization and amorphization. Our findings are of huge significance for understanding the material removal mechanism of GaAs at a nanometric machined depth.

Transcranial magnetic stimulation (TMS) is a powerful tool to probe in vivo brain circuits, as it allows to assess several cortical properties such as excitability, plasticity and connectivity in humans. In the last 20 years, TMS has been applied to patients with dementia, enabling the identification of potential markers of the pathophysiology and predictors of cognitive decline; moreover, applied repetitively, TMS holds promise as a potential therapeutic intervention. The objective of this paper is to present a comprehensive review of studies that have employed TMS in dementia and to discuss potential clinical applications, from the diagnosis to the treatment. To provide a technical and theoretical framework, we first present an overview of the basic physiological mechanisms of the application of TMS to assess cortical excitability, excitation and inhibition balance, mechanisms of plasticity and cortico-cortical connectivity in the human brain. We then review the insights gained by TMS techniques into the pathophysiology and predictors of progression and response to treatment in dementias, including Alzheimer’s disease (AD)-related dementias and secondary dementias. We show that while a single TMS measure offers low specificity, the use of a panel of measures and/or neurophysiological index can support the clinical diagnosis and predict progression. In the last part of the article, we discuss the therapeutic uses of TMS. So far, only repetitive TMS (rTMS) over the left dorsolateral prefrontal cortex and multisite rTMS associated with cognitive training have been shown to be, respectively, possibly (Level C of evidence) and probably (Level B of evidence) effective to improve cognition, apathy, memory, and language in AD patients, especially at a mild/early stage of the disease. The clinical use of this type of treatment warrants the combination of brain imaging techniques and/or electrophysiological tools to elucidate neurobiological effects of neurostimulation and to optimally tailor rTMS treatment protocols in individual patients or specific patient subgroups with dementia or mild cognitive impairment.

Objective: The extent of plastic responses of motor cortex (M1) to paired associative stimulation (PAS) varies among healthy subjects. Continuous theta-burst stimulation (cTBS) of cerebellum enhances the mean PAS-induced plasticity in groups of healthy subjects. We tested whether the initial status of Responder or Non-Responder to PAS, influenced the effect of cerebellar stimulation on PAS-induced plasticity. Methods: We assessed in 19 young healthy volunteers (8 Responders, 11 Non-Responders to PAS), how cTBS and iTBS (intermittent TBS) applied to the cerebellum before a PAS protocol influenced the plastic responsiveness of M1 to PAS. We tested whether the PAS-induced plastic effects could be depotentiated by a short cTBS protocol applied to M1 shortly after PAS and whether cerebellar stimulation influenced GABA-ergic intracortical inhibition and M1 plasticity in parallel. Results: Cerebellar cTBS restored the M1 response to PAS in Non-Responders while cerebellar iTBS turned the potentiating response to PAS to a depressive response in both groups. The depotentiation protocol abolished both responses. Conclusion: Non-Responder status to PAS is a state of M1 amenable to bidirectional plastic modulation when primed by a change in cerebello-thalamic drive. Significance: The meaning of lack of responsiveness to certain protocols probing plasticity should be reconsidered. (c) 2021 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

The purpose of this paper is to numerically investigate the fatigue life and the fatigue crack growth path of 2024 aluminum plate riveted joints. For this purpose, according to field observations, the parameters affecting fatigue life are obtained. Relevant geometric parameters such as rivet shank length, hole diameter and dimensional tolerances, as well as the location pattern of the rivets and the material of the rivet joints are studied. In this study, modeling is performed to calculate the equivalent plastic strain using the finite element method. For this purpose, a three-dimensional elastoplastic model is used for simulation. The information obtained from the finite element method in this study made it possible to place the rivets in this type of joint for use in high safety structures such as the aerospace industry. Given the importance of the problem of crack growth in 2024 aluminum plates, having the geometrical and physical parameters of the problem, the goal is to achieve the exact path of crack growth and fatigue life of riveted joints. Fatigue crack growth simulation is performed on the samples using the boundary element method. The stress intensity factor for different loading modes is determined using the boundary element method. The results showed that the geometric parameters and the rivet material have a significant effect on fatigue cracking in aluminum plates.

The seismic behavior of stainless-steel built-up box columns subjected to constant axial loads and cyclic lateral deformation that are used in special moment frames (SMFs) has been investigated through finite element (FE) analysis. A total of 208 numerical models were conducted to cover a range of parameters affecting the seismic behavior of the columns. These include the web slenderness ratio, flange slenderness ratio, global slenderness ratio, axial load level, and lateral loading protocol. The performance indices of overstrength factor, axial shortening, out-of-plane deformation, plastic hinge length, and rotation capacity were calculated and compared. Local buckling of the columns also was investigated and was shown to be responsible for a sharp rise in plastic strain and premature fracture. Predictive empirical formulas are proposed for calculating the plastic hinge length and axial shortening. All previous experimental data on built-up box columns composed of different types of steel materials were collected and added to the FE analysis results to form a reliable database. It was found that ASCE 41-17 conservatively calculated the plastic rotation angles of the built-up box columns. Furthermore, it was indicated that the highly ductile limits of AISC 341-16 for stainless-steel built-up box columns are satisfactory.

The load-bearing capacity of perfobond Leisten (PBL) shear connectors in hybrid structures is represented by the shear-friction effect between the shear surfaces caused by the interlocking of aggregates when the fracture surface of the concrete dowel slips under an external load. To carry out an accurate numerical simulation of the bearing capacity and shear transmission mechanism of the PBL shear connectors, based on the secondary development function of the user subroutine, user-defined field variable subroutine (USDFLD), the effective simulation of the transverse shear expansion effect of the concrete dowel is achieved. A comparison with the results of the test data shows that the concrete damage plasticity (CDP) model demonstrates good robustness and convergence for the prediction and simulation of the damage characteristics of concrete structures. Based on the user subroutine USDFLD's automatic update function of material points and element integration points to field variables, this model effectively simulated the functional gradient model of the concrete dilatancy angle, the load on the shear connectors is always transmitted from the near load end to the far one, and the bearing capacity is clearly affected by the boundary conditions.

To better meet the requirements of building industrialization, this study proposes the use of a concealed column to connect the two single-faced superposed shear walls horizontally. The seismic behavior, such as failure mode, hysteresis loop, skeleton curve, ductility coefficient, and reinforcement strain, of the single-faced superposed shear wall is studied using the pseudo-static test method, with the integral cast-in-place shear wall under the same geometric dimensions and experimental conditions as the control group. The research results show that the seismic behavior indexes of the two specimens are close under 0.1 axial compression ratio, indicating that the new specimen can be equivalent to cast-in-place, which possesses better overall mechanical performance and excellent seismic behavior. The vertical seam structure with the concealed column is reasonable; thus, the prefabricated and the cast-in-place parts in the new single-faced superposed shear wall can work together to withstand external loads. Finally, ABAQUS finite element analysis is carried out on the new single-sided superposed shear wall specimen and cast-in-place shear wall specimen. The analysis results of the concrete equivalent plastic strain nephogram and the reinforcement Mises cloud diagram are consistent with the test results; the trends of the hysteresis loop and skeleton curves are basically similar.

Masing/non-Masing behavior of material plays an important role in the strain energy-based methods of fatigue life prediction. Materials under fatigue are found to show three distinct categories of behavior viz. Masing, non-Masing (Type-I: when master curve can be constructed) and non-Masing (Type-II: when master curve cannot be constructed). The master curve method available in the literature for the estimation of cyclic plastic strain energy density (CPSED) can be used only for Type-I non-Masing and Masing behaviors of materials. Moreover, it could be used for estimation only, not for prediction of CPSED. Very recently (in 2021), a new method, as summarized in this article, was proposed for the prediction of CPSED and fatigue life of material irrespective of Masing or non-Masing (Type-I and Type-II) behavior. Although the method was developed, the validation of the proposed method with different Type-II non-Masing behavior materials remained a matter of further investigation. As Type-II non-Masing behavior was not highlighted earlier in the literature, such data is not readily available. In this article, we conducted low cycle fatigue tests on SS 304L material, and after an extensive literature review and analysis, three materials’ data for each of Type-I and Type-II non-Masing behaviors could be collected. The method of prediction of CPSED and fatigue life is summarized and implemented on the six different materials. The CPSED and fatigue life could be predicted within a scatter band of 1.2 and 2, respectively. This article confirms the universal nature of the new method of CPSED and fatigue life prediction.

Expanding upon Faure’s and Epstein’s writings on the plasticity of the cinematic image, this article updates this concept for the post-cinematic image of the internet era via an analysis of Olivier...

Understanding the drillability indices of thermal granite under various water-cooling conditions is of great significance for deep drilling and wellbore stability during the extraction of deep geothermal energy. In this paper, we report the results of micro-drilling tests, indentation hardness tests, friction-and-wear tests as well as conventional physico–mechanical tests on thermal granite after water-cooling treatment, and the relationships between mechanical strength and drilling parameters of granite are discussed based on statistical analysis. In addition, the micro-characteristics of thermal and water-cooling defects in granite were observed via scanning electron microscopy. With increase in thermal temperature, the conventional physico–mechanical parameters and indentation hardness of thermal granite after water-cooling decreased linearly, while the average values of drilling rate, plasticity coefficient, and the mass losses of granite specimens and the grinder increased exponentially. The average P-wave velocity, uniaxial compressive strength, tensile strength and indentation hardness decreased by 84.9, 66.2, 73.3 and 66.1%, respectively, when the granite was heated to 600 °C. At 600 °C, the wellbore wall of granite collapsed during the micro-drilling tests and the friction-and-wear tests, and the average width and density of micro-cracks of thermal granite increased to 20.54 μm and 4.82 mm/mm2. The average width and density of micro-cracks in thermal granite under various water-cooling conditions developed gradually with thermal temperature, which was the main reason for the degradation in the drillability indices of granite. Strong links exist between the mechanical strength and drilling parameters of granite after water-cooling, and the drilling parameters of thermal granite can be estimated by the use of mechanical strength with given empirical equations. This study provides a theoretical basis for the geothermally accurate simulation and engineering of wellbore stability for deep hot dry rock drilling.

Adoption of heavy haul traffic on many railroads, comprising Russian railways, has highlighted the relevance of assessing the effect of increased axial loads on the contact fatigue life of rails.The article describes a set of theoretical studies carried out to create a scientifically substantiated method for predicting the contact fatigue life of rails depending on the values of axial loads. The stress-strain state of the contact area has been determined using the finite element model of wheel rolling on a rail. It has been found that the wheel-rail rolling contact area undergoes complex multiaxial loading with the simultaneous action of normal and shear strains. Based on the analysis of models describing multiaxial fatigue damage, the Brown–Miller model was chosen, which considers the simultaneous action of normal strains at the contact area and of maximum shear strains, which most fully describes the stress-strain state of the wheel-rail rolling contact area. To apply the Brown–Miller model, fatigue stress-strain curves for rail steel have been identified. Based on the analysis of methods for determining the parameters of stress-strain curves carried out by V. A. Troschenko, a modified Roessle– Fatemi hardness method has been applied. Based on the experimentally determined values of hardness on the rolling surface, the parameters of the curves of elastic and plastic fatigue have been revealed by calculation and experiment. To establish the damaging effect of the load from wheel rolling on a rail, the concept of relative damage per rolling cycle had been assumed which is the value inverse to the number of cycles preceding formation of a contact-fatigue crack at a given value of the axial load.Calculations of the relative damage rate of the rolling surface of rails caused by contact fatigue defects were carried out with the Fatigue software package considering mean values of the indicators of the degree of fatigue strength and plasticity of rail steel and the calculated stresses in the wheel-rail contact area, as well as the plasticity correction using Neuber method. The polynomial dependence of relative damageability of the rolling surface of rails is obtained. The established functional dependence of relative damageability of the rolling surface of rails on the values of vertical forces can be used as the basis for the developed methodology for predicting the contact fatigue life of rails.

The undrained shear strength of surficial marine clays is a significant parameter for engineering construction and geological disaster assessment. The full-flow penetration test is an effective method to evaluate marine clay strength. Currently, this method is mainly used for deep penetration, in which the stable full-flow failure state with plasticity solutions is reached; however, surficial penetration lacks a theoretical basis, and related empirical methods are still being explored, especially considering the effect of ambient water. Based on this, first, a model in the framework of computational fluid dynamics is proposed to simulate the whole penetration process of a ball penetrometer in two-phase materials (i.e., marine clay and ambient water). Furthermore, centrifugal penetration tests of two typical clay samples (i.e., South China Sea soil and kaolin clay) are used to verify the accuracy of the proposed relative motion model. Second, the characteristics of the penetration resistance factor during the whole penetration in homogenized marine clays are obtained, and the relevant mechanism is analyzed by the variation in the velocity field, volume fraction and streamline of two-phase materials. Finally, the critical depth to distinguish between surficial and stable penetration is given as 6.5 times the ball diameter; the penetration resistance factor is divided into surficial and stable penetration resistance factors, and dimensionless evaluation methods are established, which provides the basis for obtaining the strength of surficial marine clays.

The construction site of the foundation pit support project in the urban area is narrow. Micropile has the advantages of flexible pile position layout, strong site adaptability, and fast construction speed, which can effectively control the horizontal displacement of the foundation pit and ensure the safety of surrounding buildings. However, the lateral bearing capacity of micropile is weak. In order to study the lateral force characteristics and failure characteristics of micropile, laboratory tests on the flexural and tensile strength of reinforced concrete micropiles with different diameters and with or without external steel pipes were performed. The authors studied the lateral force characteristics and failure characteristics of various types of micropiles. Based on numerical simulation software ABAQUS, the measured yield strength of the specimen was used as the loading force. And taking the occurrence and development of concrete damage into consideration, the loading process was simulated. The result shows the following: (1) the micropile specimens with external steel pipe had better flexural performance than the bare micropiles and the mechanical characteristics of the specimens changed from brittleness to plasticity; (2) the degree of concrete damage is greatly reduced after the external steel pipe is attached, and the bearing capacity of the micropile specimen of the same diameter is increased by 70% after the external steel pipe is added; and (3) the specimens were mainly damaged due to tensile damage. The calculation formula for the lateral bearing capacity of the concrete-filled steel tube micropile considering the damage is proposed through fitting analysis. The calculation formula, the finite element calculation value, and the calculation formula proposed by other scholars are compared with the authors' test and the test data of other scholars. The meta-calculation results, experimental results, and formula calculation results proposed by the authors have high accuracy.

Coal permeability plays an important role in the simultaneous exploitation of coal and coal-bed methane (CBM). The stress of mining-disturbed coal changes significantly during coal mining activities, causing damage and destruction of the coal mass, ultimately resulting in a sharp increase in permeability. Conventional triaxial compression and permeability tests were conducted on a triaxial creep-seepage-adsorption and desorption experimental device to investigate the permeability evolution of mining-disturbed coal. The permeability evolution models considering the influence of the stress state and stress path on the fracture propagation characteristics were established based on the permeability difference in the deformation stages of the coal mass. The stress-strain curve of the coal was divided into an elastic stage, yield stage, and plastic flow stage. As the axial stress increased, the permeability decreased and then increased, and the curve’s inflection point corresponded to the yield point. The permeability models exhibited a good agreement with the experimental data and accurately reflected the overall trends of the test results. The results of this study provide a theoretical basis for coal mine disaster prevention and the simultaneous exploitation of coal and CBM.

A conventional analog to digital converter (ADC) faces many issues with leading-edge technologies due to noise, manufacturing deviations, signal swings, etc. Thus, we pursue to design an adaptive spiking neural ADC (SN-ADC) with promising features, e.g., robust to noise, low-power, technology scaling issues, and low-voltage operation. Therefore, our approach promises to be technology agnostic, i.e., effectively translatable to aggressive new technologies. It supports machine learning and self-x (self-calibration, self-healing) that needs for industry 4.0 and the internet of things (IoTs). In this work, we design an adaptive spike-to-rank coding (ASRC), which is the main part of the spiking neural ADC. The ASRC is based on CMOS memristors emulating short-term plasticity (STP) and long-term plasticity (LTP) biological synapses. The proposed ASRC compensates deviations by adapting the weights of the synapses. Also, ASRC is designed using XFAB 0.35 μm CMOS technology and Cadence design tools. In addition, ASRC is simulated to test its performance in the temperature range (−40°C to 85°C).

Rutting has a significant impact on the pavements' performance. Rutting depth is often used as a parameter to assess the quality of pavements. The Asphalt Institute (AI) design method prescribes a maximum allowable rutting depth of 13mm, whereas the AASHTO design method stipulates a critical serviceability index of 2.5 which is equivalent to an average rutting depth of 15mm. In this research, static and repeated compression tests were performed to evaluate the permanent strain based on (1) the relationship between mix properties (asphalt content and type), and (2) testing temperature. The results indicated that the accumulated plastic strain was higher during the repeated load test than that during the static load tests. Notably, temperature played a major role. The power-law model was used to describe the relationship between the accumulated permanent strain and the number of load repetitions. Furthermore, graphical analysis was performed using VESYS 5W to predict the rut depth for the asphalt concrete layer. The α and µ parameters affected the predicted rut depth significantly. The results show a substantial difference between the two tests, indicating that the repeated load test is more adequate, useful, and accurate when compared with the static load test for the evaluation of the rut depth.

The paper analyzes the influence of tension (dam) on the stress-strain stain and plasticity margin. For the analysis, a model of continuous rolling in three adjacent stands was developed using the Deform 3D software. The adequacy of the model was confirmed by comparing the experimental data from the small-section wire mill 150 and the simulation results. Further, a computational experiment was planned to identify the effect of mismatched of rolling speeds on stress-strain stain. It is shown that for small deviations of rolling speed from the matched mode, there is no significant change in the reserve plasticity along the specific trajectory of the particles movement.

To estimate the multiaxial notch local elastic–plastic strains real timely, an online notch elastic–plastic analytical method is proposed coupling with the modified pseudo stress criterion and Chaboche constitutive model. Moreover, for the Ramberg–Osgood material, the non-proportional cyclic strain hardening can be well considered by the proposed unified online accumulation method of equivalent plastic strain increment. Meanwhile, a rapid and effective simulating algorithm for the proposed online method is provided and verified by the experimental data of TC21 titanium alloy and SAE1070 steel notched specimens. Comparisons show that the simulated results can agree with the measured data quite well under multiaxial irregular loading.

Objective Breastfeeding, which is important for early growth, is a possible moderator of genetic influence, such as the effect of the fat mass and obesity-associated gene (FTO) on body mass index (BMI). The aim of this study was to assess the moderating effect of breastfeeding duration on the relationship between FTO rs9939609 and BMI in a Caucasian sample. Methods Adolescents born in 1997 and in 1999, who were living in the Swedish county Västmanland in 2012, were invited to participate in the Survey of Adolescent Life in Västmanland. The adolescents and their parents completed self-reported questionnaires in 2012, 2015, and 2018. Genotyping of rs9939609 T > A polymorphism was conducted from saliva DNA samples. Interaction effects of parental reported breastfeeding duration in months, including regions of significance, on the relationship between rs9939609 and BMI plus overweight were assessed. Results Considering physical activity levels, parental reported breastfeeding duration was a moderator of the relationship between rs9939609 and BMI for the younger (regions of significance = 28.1 months) and older adolescents (region of significance = >19.9 months), but not for the young adults. Plots of the association between breastfeeding duration and BMI showed higher BMI for AA with short breastfeeding, but lower BMI with longer breastfeeding than AT and TT. Longer breastfeeding lowered the odds for overweight among the younger adolescents, especially among AA individuals. Conclusion Rs9939609 AA individuals were more susceptible than AT and TT individuals to both short and long breastfeeding durations, which is consistent with the differential susceptibility hypothesis. FTO rs9939609 AA might be a plasticity variant with differential susceptibility to environmental influences. Breastfeeding duration may be one of many factors that affect the relationship between rs9939609 and BMI.

Background The split sleeve cold expansion process is widely used to improve the fatigue life of fastener holes in the civil and military aircraft industry. The process introduces beneficial compressive residual stresses around the processed hole, but uncertainties remain about the character of the stress field immediately adjacent to the bore of the hole. Objective The primary objective of this study was to implement the contour method with minimising error associated with cutting-induced plasticity to provide detailed and reliable characterisation of the residual stress introduced by the split sleeve cold expansion process. Methods A systematic FE study of plasticity effects by simulating different contour cutting strategies (a single cut, two sequential cuts and a 6-cut sequence) for a cold expanded hole in an aluminium alloy coupon was conducted. The identified ‘optimum’ cutting strategy was then applied experimentally on coupons containing a hole that had been processed to 3.16% applied expansion. Results The FE study of different cutting simulations show that the locations of the stress error is consistent with the location where cutting-induced plasticity accumulated and that the magnitude and locations of stress re-distribution plasticity can be controlled by an optimised cutting strategy. In order to validate this hypothesis a high quality contour measurement was performed, showing that accurate near bore stress results can be achieved by the proposed 6-cut approach that controls cutting induced plasticity. Conclusions The present work has demonstrated that detailed FE simulation analysis can be a very effective tool in supporting the development of an optimum cutting sequence and in making correct choices of boundary conditions. Through optimizing these key aspects of the cutting sequence one is much more likely to have a successful, low error contour residual stress result.

Background: Occipital strokes often cause permanent homonymous hemianopia leading to significant disability. In previous studies, non-invasive electrical brain stimulation (NIBS) has improved vision after optic nerve damage and in combination with training after stroke. Objective: We explored different NIBS modalities for rehabilitation of hemianopia after chronic stroke. Methods: In a randomized, double-blinded, sham-controlled, three-armed trial, altogether 56 patients with homonymous hemianopia were recruited. The three experiments were: i) repetitive transorbital alternating current stimulation (rtACS, n = 8) vs. rtACS with prior cathodal transcranial direct current stimulation over the intact visual cortex (tDCS/rtACS, n = 8) vs. sham (n = 8); ii) rtACS (n = 9) vs. sham (n = 9); and iii) tDCS of the visual cortex (n = 7) vs. sham (n = 7). Visual functions were evaluated before and after the intervention, and after eight weeks follow-up. The primary outcome was change in visual field assessed by high-resolution and standard perimetries. The individual modalities were compared within each experimental arm. Results: Primary outcomes in Experiments 1 and 2 were negative. Only significant between-group change was observed in Experiment 3, where tDCS increased visual field of the contralesional eye compared to sham. tDCS/rtACS improved dynamic vision, reading, and visual field of the contralesional eye, but was not superior to other groups. rtACS alone increased foveal sensitivity, but was otherwise ineffective. All trial-related procedures were tolerated well. Conclusions: This exploratory trial showed safety but no main effect of NIBS on vision restoration after stroke. However, tDCS and combined tDCS/rtACS induced improvements in visually guided performance that need to be confirmed in larger-sample trials. NCT01418820 (clinicaltrials.gov)

This paper conducted a comprehensive study on the bearing capacity and damage behavior of circular high-strength concrete-filled thin-walled steel tubular (HCFTST) columns based on the quasi-static seismic test. The moment-axial force relationship was first analyzed in fiber element method, and the influences of key parameters including the peak strain of concrete, material strengths and diameter-to-thickness (D/t) ratios were investigated to develop a practical design method. Then, a dependent triaxiality fracture criterion of high-strength (HS) steel was introduced to establish the finite element damage model for revealing the seismic damage behavior of HCFTST columns, and subsequently a modified restoring force model based on the truss mechanism and the unified theory of concrete-filled steel tube was established and verified. The result indicates that: increasing the steel yield strength, reducing the concrete strength as well as the D/t ratio could respectively push the moment-axial force curves moving inward; the proposed parabolic moment-axial force curve agreed well with the tested bearing capacity; the HS steel tube generated a deep plasticity accumulation to induce the ductile fracture, and the concrete damage area appeared in a V-shaped distribution; increasing the axial compression ratios and D/t ratios amplified the fracture damage of the steel tube web; the established restoring force model displayed a comparatively reasonable accuracy on the degradation behavior (e.g., bearing capacity and stiffness) and the hysteretic characteristic (e.g. softening platform). The aforementioned study could provide the meaningful references for the design and seismic analysis of HCFTST columns.

Старков Н. В. Влияние формы штампованных листовых деталей на их пружинение и устранение его при импульсной электрогидравлической калибровке. Обработка материалов давлением. 2020. № 1 (50). С. 159-164. Высокопрочные стали с пределом прочности 800–1100 МПа в последние годы стали предметом исследования как предприятий, их использующих, так и научных учреждений, которые изучают их свойства в технологических процессах листовой штамповки. Эти стали наряду с высокой прочностью, отвечают требованиям высокого уровня пластичности, технологичности при выполнении сборочных операций и др. требованиям. Высокая прочность и значительное деформационное упрочнение приводят к отклонению размеров штампованных деталей по сравнению с размерами заданными инструментом. Это следствие действия упругих напряжений, которые неравномерно распределены по толщине заготовки после снятия деформирующей нагрузки, Такое пружинение характерно для деталей в форме прямолинейного или изогнутого жёлоба; в виде открытого сложного профиля и др. похожих деталей. Пружинение отсутствует полностью или очень незначительное у деталей в форме тела вращения или коробчатой формы с замкнутым контуром и фланцем или без него. Процесс импульсной электрогидравлической (ЭГ) калибровки деталей является наиболее эффективным для устранения пружинения деталей после штамповки на механических прессах. При этом ЭГ калибровка деталей из высокопрочных сталей должна выполняться с предварительным созданием в них напряжений, близких к пределу текучести металла. Это позволяет более полно использовать процесс релаксации напряжений, при котором упругие деформации металла переходят в пластические.

The improvement of lightweight and safety is the development requirement of automobile parts. Therefore, the demand of thin-walled parts with ultra-high strength is more urgent. However, with the increase of strength, the springback phenomenon of parts is particularly serious, which greatly affects the forming quality of parts. Generally, the springback of automobile parts should be controlled within 5%. Thus, the accurate simulation and prediction of springback can provide important support for the manufacture of ultra-high strength automobile thin-walled parts. In this paper, the bending springback of the medium-Mn steel, as one of the third-generation automobile steels, was studied based on experiment and simulation under different conditions. Tensile tests were carried out to evaluate comprehensive mechanical properties with high strength and high plasticity. Cyclic loading-unloading tests were conducted to analyze the changing rules of unloading elastic modulus and inelastic recovery with strain. The correlation model between unloading elastic modulus and true plastic strain was further established and the model parameters were obtained. Furthermore, V-shaped bending tests were carried out under different conditions to analyze the effects of rolling direction, bending angle, and punch fillet radius on springback. The effect of rolling direction on springback angle is negligible. The bending angle has a positive effect on springback angle, while the punch fillet radius has a negative effect. Finally, the material model with constant and variable elastic moduli were developed by using user-defined material subroutines for the medium-Mn steel. V-shaped bending tests under constant and variable elastic moduli were simulated and compared with the experimental result. The simulated result with variable elastic modulus was closer to the experimental one, which proves the importance of considering the change of unloading elastic modulus in the numerical simulation of medium-Mn steel. The research result of this paper is helpful to enhance the simulation accuracy of springback of medium-Mn steel part and promote its industrial application.

Multilevel resistive switching (RS) is a key property to embrace the full potential of memristive devices for non-volatile memory and neuromorphic computing applications. In this study, we employed nanoparticulated cobaltite oxide (Co3O4) as a model material to demonstrate the multilevel RS and synaptic learning capabilities because of its multiple and stable redox state properties. The Pt/Co3O4/Pt memristive device exhibited tunable RS properties with respect to different voltages and compliance currents (CC) without the electroforming process. That is, the device showed voltage-dependent RS at a higher CC whereas CC-dependent RS was observed at lower CC. The device showed four different resistance states during endurance and retention measurements and non-volatile memory results indicated that the CC-based measurement had less variation. Besides, we investigated the basic and complex synaptic plasticity properties using the analog current-voltage characteristics of the Pt/Co3O4/Pt device. In particular, we mimicked the potentiation–depression and four-spike time-dependent plasticity (STDP) rules such as asymmetric Hebbian, asymmetric anti-Hebbian, symmetric Hebbian, and symmetric anti-Hebbian learning rules. The results of the present work indicate that the cobaltite oxide is an excellent nanomaterial for both multilevel RS and neuromorphic computing applications.