Continuous Force Research Articles

Dynamic modulation of cortico-muscular coupling during real and imagined sensorimotor synchronisation

People have a natural and intrinsic ability to coordinate body movements with rhythms surrounding them, known as sensorimotor synchronisation. This can be observed in daily environments, when dancing or singing along with music, or spontaneously walking, talking or applauding in synchrony with one another. However, the neurophysiological mechanisms underlying accurately synchronised movement with selected rhythms in the environment remain unclear. Here we studied real and imagined sensorimotor synchronisation with interleaved auditory and visual rhythms using cortico-muscular coherence (CMC) to better understand the processes underlying the preparation and execution of synchronised movement. Electroencephalography (EEG), electromyography (EMG) from the finger flexors, and continuous force signals were recorded in 20 participants during tapping and imagined tapping with discrete stimulus sequences consisting of alternating auditory beeps and visual flashes. The results show that the synchronisation between cortical and muscular activity in the beta (14-38 Hz) frequency band becomes time-locked to the taps executed in synchrony with the visual and auditory stimuli. Dynamic modulation in CMC also occurred when participants imagined tapping with the visual stimuli, but with lower amplitude and a different temporal profile compared to real tapping. These results suggest that CMC does not only reflect changes related to the production of the synchronised movement, but also to its preparation, which appears heightened under higher attentional demands imposed when synchronising with the visual stimuli. These findings highlight a critical role of beta band neural oscillations in the cortical-muscular coupling underlying sensorimotor synchronisation.

The rise of Arab Gulf agro-capital: continuity and change in the corporate food regime

ABSTRACT The role of non-Northern capitals within the corporate food system is a matter of increasing debate within food regime literature. This article intervenes on this discussion by proposing that the Arab Gulf states are a new capital within the corporate food system. It argues that the emphasis on the role of the state, which has drawn definitions of mercantilism, has led to the exceptional and reifying treatment of this entrant. As a result, this analytical focus has obfuscated the manner that new capitals such as the Gulf states have acted as a force of continuity, as well as change.

Microstructure and magnetic properties of ultra-thin grain-oriented silicon steel: Conventional process versus strip casting

Ultra-thin grain-oriented silicon steels were processed via the conventional process and strip casting process, and the mechanisms of texture inheritance and inhibitor induced secondary recrystallization were comparatively studied in detail. In the conventional route with commercial grain-oriented silicon steel as the starting material, exact {111} 〈112〉 dominated the deformation texture after cold rolling with ~ 63% reduction, and strong Goss texture was formed in 0.08–0.10 mm thin-gauge primary recrystallized sheet. Meanwhile, weak {210} 〈001〉 and {h11} < 1/h12 > textures were also observed because of the inhomogeneous deformation with initial deviated Goss texture. After high temperature annealing, the sheet experienced incomplete secondary recrystallization with abnormal growth of Goss grains accompanied by normal growth of {210} 〈001〉 and {411} 〈148〉 grains, considering the absence of pinning force on grain boundary migration. In the strip casting process, the intensity of γ-fiber texture was increased, while grain size decreased from ~ 13.3 to ~11.4 μm and the area fraction of Goss grains decreased from 2.8% to 0.6% in the primary recrystallized sheet with decrease of thickness from 0.15 to 0.08 mm. During high temperature annealing process, MnS, (Nb,V)N and AlN provided continuous and sufficient inhibition force for normal grain growth, which guaranteed the formation of complete secondary recrystallization of exact Goss grains. Superior magnetic induction B8 was up to 1.97 T in the strip casting process, which was 0.09 T higher than the conventional route. Meanwhile, the iron losses P1.7/50 and P1.0/1000 were as low as 0.85 and 20.7 W/kg, respectively, which were comparable to the reported ultra-thin grain-oriented silicon steels. The present study provided a novel method to produce high efficiency ultra-thin grain-oriented silicon steel, which may significantly contribute to energy saving in high-frequency electrical devices.

Design and Manufacturing of a Body-Powered Hook with Force Regulation System and Composite-Based Nanomaterials

New developments in upper limb prostheses are based almost exclusively on myoelectric technology, which prioritizes the needs and infrastructure of developed countries. However, 80% of people with disabilities living in developing countries cannot afford these devices. The main needs of users in developing countries were identified through the I-Corps program, to select the ideal prosthesis type and generate a list of design requirements to improve prosthetic performance. A body-powered hook was developed through a four-stage process: conceptual design, detailed design, design for manufacturing, and manufacturing. The result was the lightweight body-powered hook with a voluntary open mechanism; it weighed 100 g and was manufactured on carbon fiber enriched with nanomaterials to provide hydrophobic and antibacterial properties. Furthermore, this prosthesis contains a novel continuous force regulation system, which allows a constant griping force from 0 to 30 N, providing the user with proprioceptive force to enable accurate and quick-responsive control. Due to its high functionality, robustness and comfort, the upper limb prosthesis developed in this study is an appropriate alternative for most users, regardless of their economic condition or the infrastructure of their country.

Anti-collision and Obstacle Avoidance of Mobile Sensor-plus-actuator Networks over Distributed Parameter Systems with Time-varying Delay

This paper addresses the anti-collision problem among mobile sensors-actuators, and settles the obstacle avoidance trouble between dynamic sensors-actuators and erratic obstacles in mobile sensor-actuator networks, which are based on a class of distributed parameter systems with time-varying delay. Initially, the radar obstacle avoidance technology is evolved into an obstacle avoidance function, combined with the anti-collision function. Subsequently, the static output feedback controller of distributed parameter systems is established. Then, by using the abstract development equation theory, operator semigroup approach and Lyapunov stability arguments, the stability analysis of the distributed parameter systems with time-varying delay is carried out. Moreover, an iterative and continuous control force on account of Newton’s second law is constructed, which makes anti-collision and obstacle avoidance control of mobile sensors-actuators be realized, and accelerates the state of this delayed system to be stable. Finally, numerical simulation results indicate that the proposed control strategy is effective.

Early Growing Season Anomalies in Vegetation Activity Determine the Large‐Scale Climate‐Vegetation Coupling in Europe

AbstractThe climate‐vegetation coupling exerts a strong control on terrestrial carbon budgets and will affect the future evolution of global climate under continued anthropogenic forcing. Nonetheless, the effects of climatic conditions on such coupling at specific times in the growing season remain poorly understood. We quantify the climate‐vegetation coupling in Europe over 1982–2014 at multiple spatial and temporal scales, by decomposing sub‐seasonal anomalies of vegetation greenness using a grid‐wise definition of the growing season. We base our analysis on long‐term vegetation indices (Normalized Difference Vegetation Index and two‐band Enhanced Vegetation Index), growing conditions (including 2m temperature, downwards surface solar radiation, and root‐zone soil moisture), and multiple teleconnection indices that reflect the large‐scale climatic conditions over Europe. We find that the large‐scale climate‐vegetation coupling during the first two months of the growing season largely determines the full‐year coupling. The North Atlantic Oscillation and Scandinavian Pattern phases one‐to‐two months before the start of the growing season are the dominant and contrasting drivers of the early growing season climate‐vegetation coupling over large parts of boreal and temperate Europe. The East Atlantic Pattern several months in advance of the growing season exerts a strong control on the temperate belt and the Mediterranean region. The strong role of early growing season anomalies in vegetative activity within the growing season emphasizes the importance of a grid‐wise definition of the growing season when studying the large‐scale climate‐vegetation coupling in Europe.

Actionable strategy framework for digital transformation in AECO industry

PurposeThe Fourth Industrial Revolution (4IR) holds the potential to improve capabilities- and technology-based innovation, which will enable breakout for architectural, engineering, construction and operation and maintenance (AECO) companies, for international competitiveness. Though the top management of such companies is convinced on the utility of the applications, they are unsure on the strategy of implementing the same. The objective of this research is to suggest a strategy framework for digital transformation of the AECO value chain.Design/methodology/approachThe nascent level of research on 4IR in construction necessitated the adoption of the integrative review methodology for the study. Extensive literature review of research on strategy and 4IR has been utilized to establish the validity of the first two pillars, namely “a strategy of simple rules in a complex environment; and deployment of dynamic capabilities.” The validation of a construct for the third pillar of “confluence of change and continuity forces” has been achieved via hypothesis testing of data obtained through a questionnaire survey.FindingsThe present study has integrated three diverse ideas of strategy, named as the pillars, to facilitate sustainable digital transformation. Within the third pillar, top three continuity forces which offer resistance to change are organization culture, existing delivery processes and networks, and existing standard operating procedures. On the other hand, the leading drivers of change are needs of competitiveness; global industry trends and the advent of new technologies/innovations.Research limitations/implicationsThis provides a practical approach to operationalize digital transformation of the AECO at an organization level. The validation relied on opinion and perspectives of a sample frame in the Indian context, which was its limitation.Originality/valueThis paper suggests a strategy framework of three pillars to help address specific strategy dilemmas during implementation of digital transformation of particular organizations in AECO. The study contributes to both theory and practice by helping leaders of AECO companies, associations, policymakers and the academia to strategize transformations successfully.

Continuous assessment of longitudinal temperature force on ballasted track using rail vibration frequency

In this study, the possibility of using the rail vibration frequency to assess the longitudinal temperature force on the rail of ballasted track was investigated experimentally. An empirical formula was subsequently derived to link the frequency index to multiple factors, including the longitudinal temperature force, under-rail stiffness, and fastener spacing. Further tests were conducted to analyse the applicability and accuracy of the frequency index in continuous longitudinal force measurements under different line conditions (i.e. in the non-expansion zone and expansion zone). A technique for using the frequency index to assess the longitudinal temperature force was finally developed. The main results are as follows. (1) The first-order pinned–pinned modal frequency and peak frequency of the mid-span response are very close, and they both change linearly with the longitudinal temperature force on the rail. The rate of change in the vertical direction is larger than that in the horizontal direction. (2) Even if influenced by multiple factors, the peak frequency of the rail mid-span response is suitable for continuous longitudinal temperature force assessment under appropriate measures, and longitudinal temperature force detection could be realized with proper preparation. (3) Using the mid-span response frequency to detect the temperature force of rail located in the expansion zone causes deviation of the results, and under-rail materials whose stiffnesses are insensitive to temperature help reduce this deviation.

Kinematic accuracy and nonlinear dynamics of a flexible slider-crank mechanism with multiple clearance joints

Clearance joint appears in the multibody system and it could cause the uncertainty of motion. A general method for dynamic modelling and analysis of slider-crank mechanism with multiple clearance joints is presented and discussed in this work. The contact-impact characteristics of clearance joint are described by the nonlinear continuous contact force model. With flexible link taken into account, the dynamic characteristics of slider-crank mechanism with multiple clearance joints are analyzed based on the presented model. Then, the dynamic response of a flexible slider-crank mechanism is measured to clarify how to clearance joints can cause the vibration phenomenon of multibody system. Moreover, the stability and chaos analysis are conducted with the purpose of performing a parametric study, which quantifies the effects of clearance size and rotational speed on dynamic behavior of multibody system with multiple clearance joints. The numerical results indicate that the dynamic behavior of a flexible slider-crank mechanism depends on the characteristics of clearance joints.

Constitutional Reform and the Value of Social Citizenship

Abstract Viewed through the lens of social policy, Russia’s 2020 constitutional reform codifies existing priorities without addressing the issues that have fragmented the meaning of social citizenship. Placing these changes in theoretical and historical context, we identify the core causes of inequity in the social welfare system, the sustained gap between state promises, and Russians’ lived experience. Our case studies highlight the sources of shared social grievances and the obstacles to national collective action that maintain stability in the facing of increased localized protest actions. We conclude by emphasizing the importance of observing the opposing forces of continuity and change in Russian politics as they define and redefine the meaning of social citizenship.

A smart point-of-care compliance monitoring solution for brace treatment of adolescent idiopathic scoliosis patients

Scoliosis is a medical condition which occurs in adolescents, where an individual's spine develops curvature. A Thoracolumbosacral orthosis (TLSO) is a type of brace used as a long term treat-ment method to control the lateral curvature of the spine in adolescent idiopathic scoliosis (AIS). However, compliance of the daily prescribed duration and tightness of the brace is a big challenge, which plays a significant role in the success of brace treatment. In this paper, we designed and de-veloped a wearable multi-modal sensor solution, which is embedded into the AIS patient's brace. The custom-designed hardware consists of a sensor board, a force sensor & housing, a miniature triaxial accelerometer and gyroscope sensor. The force sensor records the force being exerted by the patient's brace padding, while the accelerometer and gyroscope sensors capture upper trunk movements, providing cues to determine the patient's activities and lifestyle to help with more accurate estimation of the two key parameters, including 1) the in-brace tightness level 2) the duration of the brace wear, in an unsupervised manner. Furthermore, we presented a signal pro-cessing and data analytic methodology to identify the duration and tightness of the brace wear, in addition to identifying various patient activities based on the fusion of continuous force and iner-tial motion sensor recordings. We, specifically, derived a signal processing activity identification method using power spectral density estimation of the sensor data recordings. Then, we evaluate of the effectiveness of brace treatment in a pervasive manner. The proposed method evaluates the duration of brace wear through the process of segmentation and calculates the tightness level of the brace by estimating the baseline force per segment of data. This analysis is done when the patient performs activities including sitting, standing, climbing, walking, running and lying. We investigated an experimental scenario in which the patient performs a series of pre-defined activ-ities at home during day-long segments of brace wear. All analysis is performed using pervasive sensor data recordings. The experimental results demonstrated that we achieved an overall accu-racy of 99.8%, 100% and 99.9% for patients 1, 2 and 3 respectively for semi-supervised activity detection. We continued our compliance study for approximately a month. The level of tight-ness of brace-fit gradually reduced over a period of 2 weeks by 30% as the compliance of brace treatment increased from 7% to 90% on average. Given our experimental results and objective observations, our proposed system is capable of arranging for re-fitting sessions automatically so that the physician can adjust the brace tightness levels for a more effective brace treatment. • Brace treatment for AIS patients is long-term & pervasive demanding self-compliance. • Pervasive monitoring can provide two key factors of duration and tightness of the brace-wear. • We design a multimodal smart brace monitoring system to estimate the two factors. • We design a robust signal processing recipe to undertake unsupervised recordings. • Our experiments demonstrated that our system generates reliable & robust estimates.

Continuous contact force model with an arbitrary damping term exponent: Model and discussion

More than twenty continuous contact force models have been presented for modeling contact-impact problems; however, there was no uniformity regarding the value of the damping term exponent in these models. A new type of continuous contact force model is proposed in this research, in which the value of the damping term exponent can be arbitrary. Then, the effect of the value of the damping term exponent on the model accuracy is investigated by comparing the simulation and experimental results. As it is almost impossible to obtain an analytical solution based on the system dynamic equation, according to the rule of energy equivalence, an approximate dynamic equation is developed by introducing an equivalent indentation and equivalent velocity. Based on the system dynamic equation and the approximate dynamic equation, a primary formula for the hysteresis damping factor of the model can be obtained. Through nondimensional analysis, new models for different values of the damping term exponent are established by modifying the primary formula. The comparison between the simulation results and published experimental data demonstrates the validities of the new models and reveals that the influence of the value of the damping term exponent on the model accuracy can be considered to be negligible.

Influence of Projectile-Barrel Coupling on Gun Vibration of the Moving Tank Under the Influence of a Stabilizer

The initial disturbance of the projectile and the barrel vibration is the premiere factors influencing the firing accuracy of the moving tank. To better understand the launch progress of the moving tank, a novel mechanical–electrical-hydraulic co-simulation model of the moving tank under the influence of a stabilizer was established, and a contact model with clearance for projectile-barrel rigid-flexible coupling was presented. Therein, the projectile-barrel coupling relationship was described by a cylindrical joint with clearance, and an improved contact algorithm based on the L–N model (Lankarani–Nikravesh continuous contact force model) was introduced to calculate the projectile-barrel contact force. The established model was verified tentatively by comparing with previously published literature. The simulation results indicate that the projectile-barrel coupling affects both the cradle vibration characteristics and the barrel dynamic bending features of the moving tank. It causes the gun's pointing deviation towards the target and the pointing deviation of the projectile velocity at muzzle exit and ultimately affects the firing accuracy of the moving tank.

Periodic forcing of a large turbulent separation bubble

Abstract

Benchmarking surface tension measurement method using two oscillation modes in levitated liquid metals

The Faraday forcing method in levitated liquid droplets has recently been introduced as a method for measuring surface tension using resonance. By subjecting an electrostatically levitated liquid metal droplet to a continuous, oscillatory, electric field, at a frequency nearing that of the droplet’s first principal mode of oscillation (known as mode 2), the method was previously shown to determine surface tension of materials that would be particularly difficult to process by other means, e.g., liquid metals and alloys. It also offers distinct advantages in future work involving high viscosity samples because of the continuous forcing approach. This work presents (1) a benchmarking experimental method to measure surface tension by excitation of the second principal mode of oscillation (known as mode 3) in a levitated liquid droplet and (2) a more rigorous quantification of droplet excitation using a projection method. Surface tension measurements compare favorably to literature values for Zirconium, Inconel 625, and Rhodium, using both modes 2 and 3. Thus, this new method serves as a credible, self-consistent benchmarking technique for the measurement of surface tension.

A highly efficient beam-in-beam large sliding contact method for flexible multibody dynamics

Beam-in-beam large sliding contact exists in simulations of drillstring-riser systems, offshore pipe-in-pipe systems, medical catheter-guidewire-stent systems, among others. Large sliding between the pipes may lead to discontinuity of contact force and non-sparsity of system Jacobian in numeric simulations, which then may result in non-physical disturbances and low efficiency. To overcome this phenomenon, a consistent-contact-force algorithm and a highly efficient implicit-integration scheme are proposed in this paper. Geometric treatments are applied in gap and overlap areas to obtain continuous contact force, in addition to contact-history-based fast detection. The contact force Jacobian is ignored as the flexible multibody system is solved with an inexact Newton iteration and an empirical formula is used to estimate the convergence conditions. Four numeric examples are computed to verify the presented method, including a buckling benchmark and a riser-recoil industrial application. The numeric results show that the proposed method is accurate and highly efficient.

Large eddy simulations of forced and stably stratified turbulence: Evolution, spectra, scaling, structures and shear

Large eddy simulations (LES) of forced stratified turbulence in a triply-periodic box at multiple Froude numbers (Fr0) are carried out to study the effect of stratification on energy evolution, spectra, scaling, vortical structures and shear for flows at Re=25000. The dynamic Smagorinsky model is used as the sub-grid scale (SGS) closure with a grid density of 963. A three-dimensional (3D) continuous forcing scheme adapted from Rosales et al. (2005), where a constant factor is multiplied to the velocity scales, is applied to LES for the first time in stably-stratified turbulence. Calculations for three different Froude numbers, Fr0=0.1,0.2 and 0.3, are presented here. The behavior of the energy spectra and flux and evolution of local quantities such as buoyancy Reynolds number, Froude number, Richardson number and shear distribution at a fully developed state are analysed in detail. In addition, the 3D isosurfaces and two-dimensional (2D) isocontours of vorticity are presented, which clearly highlight the suppression of turbulence in the vertical direction. Increase in the intensity of stratification, results in a delay in the attainment of a fully-developed state. Moreover, the dissipation rates and enstrophy at the fully developed state are lower for lower Froude numbers. A κ-3 scaling is observed for the vertical kinetic energy spectra and a κ-53 scaling for the potential energy spectra. For moderate stratification, i.e. at Fr0=0.3, the scaling results based on the Bolgiano and Obukhov theory are verified here as well.

A methodology for dynamic behavior analysis of the slider-crank mechanism considering clearance joint

Abstract The slider-crank mechanism is used widely in modern industrial equipment whereby the contact-impact of a revolute clearance joint affects the dynamic behavior of mechanical systems. Combining multibody dynamic theory and nonlinear contact theory, the computational methodology for dynamic analysis of the slider-crank mechanism with a clearance joint is proposed. The differential equations of motion are obtained considering the revolute clearance joint between the connecting rod and slider. In the mechanical system, the contact force is evaluated using the continuous force model proposed by Lankarani and Nikravesh, which can describe the contact-impact phenomenon accurately. Then, the experimental study is performed whereby the numerical results are compared with the test data to validate the proposed model. Moreover, the dynamic response analysis is conducted with various driving velocities and clearance sizes, which also explains that the sensitive dependence of a mechanical system on the revolute clearance joint.

Diagnosis of damage evolution process for asphalt mixtures using pattern recognition with acoustic emission signals

The fractures in asphalt materials evolving from microcracks directly affect the performance of asphalt pavements. Acoustic Emission (AE) technique plays a crucial role in dynamically monitoring the internal structural changes of stressed materials. This study attempted to characterize the fracture mechanism of asphalt mixtures by identifying the characteristics of recoded AE data. Firstly, the three-point bending tests and AE tests were simultaneously conducted to investigate the damage evolution process of asphalt mixtures through the time characteristics of AE parameters. Secondly, the cusp catastrophe model based on AE energy rate was employed to explore the mutational characteristics of AE process and to evaluate the damage state of asphalt mixtures. Finally, the k-means method was applied to distinguish the patterns of AE signals associating with the specific damage behaviors of asphalt mixtures during the flexural failure process. The results show that abrupt change of AE energy rate and cumulative AE energy could reflect the evolutionary characteristics of damage in asphalt mixtures. The mutational analysis of AE energy rate reveals that the damage state of asphalt mixtures subjected to the continuous external forces would change between instability and stability, which could be served as a complementary approach for further understanding the periodic variation characteristics of damage evolution process based on cumulative AE energy. The k-means method could effectively classify the recorded AE signals of asphalt mixtures in three-point bending tests into three distinctive clusters. The potential mechanisms for the clustered signals corresponding to different damage behaviors of asphalt mixtures could be characterized by the parametric characteristics and the wavelet power spectrum of AE signals.

The relationship between disability and parental status: a register study of the 1968 to 1970 birth cohorts

BackgroundHaving children is a major life course event yet some disabilities could make it biologically challenging and some others could limit access to necessary socioeconomic resources. To date, there is relatively little data on disability and parental status and our study aimed to investigate this relationship.MethodsThis longitudinal cohort study was based on register data obtained from all people born in Sweden from 1968 to 1970 (n = 440220). We performed descriptive analyses, graphical plots, logistic regression, and Cox regression analyses.ResultsOur findings from both logistic regression and Cox regression indicated that individuals that started to receive disability benefits at an early age had reduced chances of having children during the follow-up duration. Men with disabilities were less likely to have children when compared to women with disabilities and to men and women without disabilities.ConclusionsWe found evidence that disability during early adulthood was associated with reduced chances of having children. Findings support policies and programmes aimed at promoting optimal health during early adulthood, as this would promote continued labour force participation, reduce early use of disability benefits, and possibly improve chances of becoming a parent.