Step Motion Research Articles

Continuous Identification of Freezing of Gait in Parkinson’s Patients Using Artificial Neural Networks and Instrumented Shoes

Freezing of gait is an episodic phenomena faced by many patients with Parkinson's disease. It is characterized by episodes during which patients are unable to generate effective forward stepping movements, despite absence of motor deficits. During the onset of the event, the patients are less stable with statistically different stride width, toe in/out angle and center of pressure distance. It has been postulated that the degree of freezing can be reduced by providing external sensory feedback to the patients during the event. However, this intervention could be facilitated by accurate identification of freezing events in real-time. This manuscript presents an Artificial Neural Network model which uses signals recorded by an instrumented footwear to predict if a walking subject is having a freezing episode. Our model presented in this paper is capable of continuously predicting freezing of gait events at a high temporal resolution of 50 Hz, using a 0.5 second window of data recorded by the instrumented shoes, with a sensitivity of 96.0±2.5%, a specificity of 99.6±0.3%, a precision of 89.5±5.9%, and an accuracy of 99.5±0.4%. This algorithm was tested with data collected from 10 patients with Parkinson's disease with frequent freezing of gait episodes.

In situ reflection electron microscopy for investigation of surface processes on Bi2Se3(0001)

The sublimation and van der Waals (vdW) epitaxy on Bi2Se3(0001) surface have been first visualized using in situ reflection electron microscopy. When Bi2Se3(0001) surface was exposed to a Se molecular beam (up to 0.1 nm/s) and heated to ∼400°C, we observed ascending motion of atomic steps corresponding to congruent Bi2Se3 sublimation. During the sublimation, grooves made by probe lithography act as sources of atomic steps: groove depth increases and generates atomic steps that move in the ascending direction away from the source. We used this phenomenon to create self-organized regularly-spaced zigzag atomic steps having 1 nm height on the Bi2Se3(0001) surface. The deposition of Bi (up to ∼0.01 nm/s) onto the Bi2Se3(0001) surface at constant Se flux (up to ∼0.1 nm/s) reversed the direction of the step flow, and vdW epitaxy was observed. The deposition of In and Se onto the Bi2Se3(0001) surface at ∼400°C led to the epitaxial growth of layered In2Se3. This vdW heteroepitaxy started with 2D island nucleation and, after 3–5 nm growth, continued with a screw-dislocation-driven formation of 3D islands. Ex situ Raman scattering measurements have shown that the grown 20-nm-thick In2Se3 film exhibits vibrational modes that originate from the β-In2Se3 crystal phase.

Phase-Dependent Effects of Transcutaneous Spinal Cord Stimulation on Regulation of Kinematics of Human Stepping Motions

Phase-Dependent Effects of Transcutaneous Spinal Cord Stimulation on Regulation of Kinematics of Human Stepping Motions

Air Quality Impact during COVID-19: A Case Study in One Institute of Higher Learning (IHL) in Malaysia

Novel coronavirus pneumonia (COVID-19) was first detected in Wuhan, China, soon its rapid escalation in global and become global spread of infection including Malaysia. The principal cases in Malaysia were distinguished on 25th January 2020. The number of cases keeps on ascending since March 2020 until Malaysia has the highest number of cases in Southeast Asia. Therefore, to respond and control the COVID-19 pandemic in the country, the 2020 Movement Control Order (MCO) is implemented. The MCO actualizes a movement of reasonable steps to control advance flare-ups of COVID-19 within the country, counting closing down all organization and private premises aside from those related with "fundamental administrations" and several parts with government permission, and travel disallowances on all outsiders entering Malaysia and on Malaysians taking off the country. Correspondingly, this MCO has brought about the decrease of air contamination as the number of engine vehicles and the activity of businesses is suspended. This study aims to determine the concentrations of particulate matter 2.5 at the selected monitoring stations in UTHM and to correlate environmental factor which is wind speed and wind direction with the Particulate Matter 2.5. This study uses PM2.5 fixations to explain the air pollution before to MCO, stages I, II, III, and IV, where the contingent MCO is actualized. Such outcomes relate to the air contamination list as it was discovered that the PM2.5 fixations showed a high decrease of up to -74 μg/m3 during Phase IV MCO.

Time evolution of GaAs(111) surface morphology and desorption rate during Langmuir evaporation: Monte Carlo simulation

The high-temperature GaAs annealing kinetics is studied by Monte Carlo simulation. The evaporation rate dependences on the annealing time are obtained for (111)A and (111)B substrate surfaces in a 800–1200 K temperature range. The surface morphology evolution and evaporation kinetics are shown to be dependent on the GaAs substrate orientation. The congruent evaporation of (111)A surface corresponds to the layer-by-layer evaporation mode, while, on the (111)B surface, multilayer vacancy islands are formed. At temperatures exceeding the congruent evaporation temperature, the initial evaporation stage before the gallium droplet formation agrees with the congruent evaporation mode. The appearance of Ga droplets on the surface, corresponding to the start of incongruent evaporation regime, results in a sharp fall of the GaAs evaporation rate. It is found that the Ga droplet on vicinal surfaces locally inverts the step movement direction.

Growth Kinetics of the (110) Faces of Complex Potassium Cobalt–Nickel Sulphate K2CoxNi1−x(SO4)2·6H2O Crystals

The normal growth rate, the steepness of polygonized growth hillocks and the velocity of step movement on the (110) faces of potassium cobalt–nickel sulphate crystals in aqueous solutions with cobalt to nickel ratios of 1:1 and 1:2 were investigated as a function of supersaturation by the geometry of growth hillocks using laser interferometry. It was found that the morphologies of growth hillocks on the (110) faces of the crystals grown from 1:1 and 1:2 solutions are similar and that the growth hillocks are formed by multiple screw dislocation sources. The experimental data on the growth kinetics of the (110) faces of the crystals were analyzed by using the Burton–Cabrera–Frank theory. It was found that (1) there is a critical supersaturation for the growth of the (110) faces, and the value of this supersaturation in the 1:2 solution is higher than that in the 1:1 solution, and (2) the kinetic coefficient of the step movement in the sectors of growth hillocks is highly anisotropic, and the values of this coefficient are larger in 1:2 solution than in 1:1 solution. These results are discussed in the presented work.

The Target-Step-Test (TST) to Evaluate Locomotory Differentiation Ability – Evaluation of the Test and Development of Norm Values for Healthy People

Abstract Introduction There is need of a clinical assessment measuring locomotory differentiation ability. Objective The Target-Step-Test (TST) for evaluating the locomotory differentiation ability should be checked for its reliability in the context of practical application. Furthermore, it is necessary to define a standard value range. In addition, an examination of the exercise attempts should enable a statement to be made about the adequate test execution. Materials and Methods 208 healthy adults between 18 and 45 years were asked to perform the TST twice. The test procedures of 205 test persons could be evaluated. The individual experiments and target steps were photo documented. The 4 directions of movement included stepping forward with the right and left leg and stepping to the side with the right and left leg. Each direction contains 3 exercise steps with open eyes and one target step with closed eyes. The difference to the target line was rounded up or down to 5 mm by the raters. Results For the inter-rater and intra-rater reliability as well as the test-retest reliability high intraclass correlation coefficients (ICCs) and corrected kappa values could be calculated. 90 % of the measurements performed are within the range of −4.85 to 5 cm of the target line. The testing of the measured value repetition shows no differences between 2nd and 3rd step with open eyes. Therefore, it should be sufficient to perform 2 exercise steps with open eyes before the decisive target step with closed eyes. Conclusions The TST is reliable regarding inter-rater, intra-rater and test-retest reliability. The standard value range for healthy adults is set to±5 cm distance from the target line. Regarding the test procedure, it is sufficient to execute the target step with closed eyes after practicing twice with open eyes. The Target-Step-Test is reliable and can easily be carried out in daily routine to measure locomotory differentiation ability as a step movement.

An embedded capacitive sensor for in-situ angular detection of micromotor

An embedded capacitive sensor in traveling wave ultrasonic motor is proposed for angular detection. Equivalent circuit model of the system is well studied that correlation between sensor structure, parasitic parameters and the property of detection signal is found. Sensor structure is optimized with innovate structural design including multi-layer shielding, planar isolation and differential detection design. The signal-to-noise ratio of the detection signal is found up to 40 ​dB and the angular detection accuracy during step motion is less than 0.1°.

Miniaturised Low-Cost Gamma Scanning Platform for Contamination Identification, Localisation and Characterisation: A New Instrument in the Decommissioning Toolkit.

Formerly clandestine, abandoned and legacy nuclear facilities, whether associated with civil or military applications, represent a significant decommissioning challenge owing to the lack of knowledge surrounding the existence, location and types of radioactive material(s) that may be present. Consequently, mobile and highly deployable systems that are able to identify, spatially locate and compositionally assay contamination ahead of remedial actions are of vital importance. Deployment imposes constraints to dimensions resulting from small diameter access ports or pipes. Herein, we describe a prototype low-cost, miniaturised and rapidly deployable ‘cell characterisation’ gamma-ray scanning system to allow for the examination of enclosed (internal) or outdoor (external) spaces for radioactive ‘hot-spots’. The readout from the miniaturised and lead-collimated gamma-ray spectrometer, that is progressively rastered through a stepped snake motion, is combined with distance measurements derived from a single-point laser range-finder to obtain an array of measurements in order to yield a 3-dimensional point-cloud, based on a polar coordinate system—scaled for radiation intensity. Existing as a smaller and more cost-effective platform than presently available, we are able to produce a millimetre-accurate 3D volumetric rendering of a space—whether internal or external, onto which fully spectroscopic radiation intensity data can be overlain to pinpoint the exact positions at which (even low abundance) gamma-emitting materials exist.

Location tracking scanning method based on multi-focus in confocal coordinate measurement system

Confocal microscopy is high precision and widely used method for topography measurement. The surface height information is obtained by peak extraction of the axial response signal (ARS) which axial tomography of the surface is required. Therefore, when scanning large-diameter surfaces with a confocal coordinate measuring system (CCMS), the relative horizontal scanning trajectory (RHST) between the confocal sensor and surface is repeated and time-consuming step motion, which greatly increases the measurement time. To improve the scanning measurement efficiency of CCMS, we propose a new location tracking scanning (LTS) method based on multi-focus. In the LTS method, the RHST is a continuous linear motion during the process of axial tomography, and the horizontal motional surface is located and tracked through a series of focuses to restore the ARS. A generatrix profile of a spherical surface is measured to verify the effectiveness of the proposed method, and the results show that the scanning measurement time can be reduced by more than 90% without loss of accuracy of the profile measurement.

Effect of simulated tennis steps and slides on tread element friction and wear

In hard court tennis, players change direction by either stepping or sliding. The shoe–surface friction during these movements is crucial to player performance. Too little friction when stepping may result in a slip. Too much friction when attempting to slide could cause the player to move only a short distance, or to fail to slide. To understand the influence of tread design on shoe–surface friction in tennis, experiments were performed on individual shoe tread elements that replicated the tribological conditions typically experienced during hard court step and slide movements. Tread element orientation had no effect on the static friction in step movements, but longer tread elements (in the sliding direction) had 9% lower dynamic friction during slide movements (p < 0.001). The friction between tennis shoe tread and hard court tennis surfaces is also shown to be influenced by the tread’s sliding history, and the wearing pattern that forms on the surface of the rubber.

Conversion of geared DC motor into stepper motor using switching delay time signals

In solar tracking system, general stepper motor is used to control the stepwise movement and low speed of solar panel in vertical motion. Degree of rotation is directly proportional to stepwise movement (stepping method) of stepper motor. But it is cumbersome process to hold a solar panel at a particular vertical position depending on the sun’s position using low cost stepper motors. So, geared DC motor is implemented into stepper motor for low-speed applications using Stepping Method (GDCSM). Degree per step movement of geared DC motor is identified using Step angle switching delay time signal (A) of microcontroller. Speed of geared DC motor is controlled by passing fixed time interval between the pulses where the pulses have fixed width. Controlling speed is implemented by using Step delay time signal (D) of microcontroller. Combining effect of switching delay time signals A and D represents the Stepping Method. Stepping method resembles the step movement and controlling speed of the stepper motor. Speed of 10RPM & 30RPM geared DC motors is operated at 10V DC power supply. Microcontroller ATmega 328P with switching delay time signals is used to control the geared DC motors. Performance of 10RPM & 30RPM GDCSM is analyzed with stepper motors in terms of Relative slip degree error per revolution (RE_mathrm{{S}}) and acceptable slippage degree tolerance under open loop condition. Change in consuming voltage tolerance (varDelta) during rotation of GDCSM is another parameter which is used to maintain the constant actual total step count per revolutions of GDCSM. At 40 ms of step angle delay time (A), 10RPMGDCSM has 120 steps per revolution. At 25 ms of A, 30RPMGDCSM has 55 steps per revolution. Speed of 10RPM & 30RPM GDCSM is controllable up to 2RPM when its RE_mathrm{{S}} or acceptable slippage degree tolerance value is less than or equal to 1%. If varDelta value of GDCSM is less than or equal to − 0.4%, then it behaves like stepper motor. GDCSM is suitable to hold and control vertical position of solar tracking system with low speed and step movement. Performance of geared DC motor experimentally showed better result than commercial available stepper motors like 28BYJ-48 or STP-43d1027-01.

Global motion estimation with iterative optimization-based independent univariate model for action recognition

Motion information used in the existed video action recognition schemes is mixing of global motion(GM) and local motion(LM). In fact, GM & LM have their respective semantic concepts. Thus, it is promising to decouple GM and LM from the mixed motions. Numerous efforts have been made on the design of global motion models for video encoding, video dejittering, video denoising, and so on. Nevertheless, some of the models are too basic to cover the camera motions in action recognition while others are over-complicated. In this paper, we focus on the characteristic of the action recognition and propose a novel independent univariate GM model. It ignores camera rotation, which appears rarely in action recognition videos, and represents the GM in x and y direction respectively. Furthermore, GM is position invariant because it is from the universal camera motion. Pixels with global motions are subjected to the same parametric model and pixels with mixed motion can be seen as outliers. Motivated by this, we develop an iterative optimization scheme for GM estimation which removes the outlier points step by step and estimates global motions in a coarse-to-fine manner. Finally, the LM is estimated through a Spatio-temporal threshold-based method. Experimental results demonstrate that the proposed GM model makes a better trade-off between the model complexity and the robustness. And the iterative optimization scheme is more effective than the existed algorithms. The compared experiments using four popular action recognition models on UCF-101 (for action recognition) and NCAA (for group activity recognition) demonstrate that local motions are more effective than the mixed motions.

Analysis and variable step control of a bidirectional complementary-type inchworm actuator

To meet the demands of high speed and large loading capacity in various nanopositioning applications, a voltage sequence based step analysis and the corresponding variable step control strategy are explored for a bidirectional complementary-type inchworm actuator. Specifically, the bidirectional variable step motion can be achieved without significant drop of the loading capacity by controlling the two-channel input voltage sequences, where the variable speed motions can help to achieve more rapid nano-positioning tasks. In particular, we introduce the voltage sequences in the modelling of the step length and the total clamping force for the purpose of achieving controllable bidirectional motion with large loading capacity. Real time control experiments are comprehensively conducted, which demonstrates a bidirectional variable step motion range of ±22 µm is achieved by controlling two-channel input signals. In addition, the actuator with the proposed method has an adjustable total clamping force capable of improving the motion stability and loading capacity in variable step motion, which are favourable to various engineering applications in high speed nanopositioning areas.

Validation of Walking Speed Estimation from Trunk Mounted Accelerometers for a Range of Walking Speeds.

Walking speed is a strong indicator of the health status of older people and patients. Using algorithms, the walking speed can be estimated from wearable accelerometers, which enables minimally obtrusive (longitudinal) monitoring. We evaluated the performance of two algorithms, the inverted pendulum (IP) algorithm, and a novel adaptation correcting for lateral step movement, which aimed to improve accuracy during slow walking. To evaluate robustness, we gathered data from different groups (healthy adults, elderly, and elderly patients) of volunteers (n = 159) walking under various conditions (over ground, treadmill, using walking aids) at a broad range of speeds (0.11–1.93 m/s). Both of the algorithms showed good agreement with the reference values and similar root-mean-square errors (RMSEs) for walking speeds ≥0.5 m/s, which ranged from 0.09–0.16 m/s for the different positions, in line with the results from others. However, for slower walking, RMSEs were significantly better for the new method (0.06–0.09 m/s versus 0.15–0.19 m/s). Pearson correlation improved for speeds <0.5 m/s (from 0.67–0.72 to 0.73–0.82) as well as higher speeds (0.87–0.97 to 0.90–0.98) with the new method. Overall, we found that IP(-based) walking speed estimation proved to be applicable for a variety of wearing positions, conditions and speeds, indicating its potential value for health assessment applications.

Spontaneous synchronization of motion in pedestrian crowds of different densities.

Interacting pedestrians in a crowd spontaneously adjust their footsteps and align their respective stepping phases. This self-organization phenomenon is known as synchronization. However, it is unclear why and how synchronization forms spontaneously under different density conditions, or what functional benefit synchronization offers for the collective motion of humans. Here, we conducted a single-file crowd motion experiment that directly tracked the alternating movement of both legs of interacting pedestrians. We show that synchronization is most likely to be triggered at the same density at which the flow rate of pedestrians reaches a maximum value. We demonstrate that synchronization is established in response to an insufficient safety distance between pedestrians, and that it enables pedestrians to realize efficient collective stepping motion without the occurrence of inter-person collisions. These findings provide insights into the collective motion behaviour of humans and may have implications for understanding pedestrian synchronization-induced wobbling, for example, of bridges.

Effects of step movement on the starting block with a back plate for start performance in competitive swimming relay start

Effects of step movement on the starting block with a back plate for start performance in competitive swimming relay start

Improvement in step resolution and response time of ultrasonic motor by using a piezoelectric resonant shunting circuit as damping control.

Ultrasonic motors can be driven by burst voltage to obtain micro-stepping motion, and the corresponding step size depends on the load and cycle number of the applied ac driving voltage in one burst. The rotor of the motor achieves a step motion through a process of startup-acceleration-deceleration-stop. To obtain a large torque (or thrust force) and quick startup, a large vibration amplitude of a stator and a high growth rate are desired; thus, a large mechanical quality factor and a high electromechanical coupling factor are required. However, the stator vibration decays for a long time before it stops because of low mechanical energy loss; meanwhile, the rotor moves a big step. Hence, there is contradiction between thrust force and resolution/response time. This paper presents a new drive method to improve the step resolution and response time while keeping the torque by damping control. By simply adding a switch and a shunting damp circuit and connecting the shunting circuit to ultrasonic motors at the end of a drive burst signal, the stator vibration attenuates more rapidly and the step size is reduced. First, the damping effect of the piezoelectric system with a passive resonant shunting circuit (a resistor and an inductor connected in series) on the free stator of a bar-type rotary traveling wave ultrasonic motor has been tested. Next, a drive circuit comprising electronic switches and the shunting circuit is designed and utilized for measuring the performance of the motor. Experimental results have well proven the proposed method.

Design and Fabrication of Step Feeder automation Machine for the Automobile Steering Ball joints

Automation feeding machine helps to replace the manual feeding of the components to achieve the production rate. Even so, all industrialists have been trying to get 100% efficiency from every machine and to give more production. The production rate of the machine is depended on certain factors like feeding, accuracy, Manpower, etc. However, feeding is the most important factor, because the production will be fast only while the component is federal quick. This paper is providing an automation solution of feed ball joints for an automotive industry when the vehicle gathers the steering assembly. There were many feeding mechanisms available. Still, the ball joint is such a large component and should need a certain interval to feed it correctly as required. In this machine, the hoppers to be a trapezoidal tanks stores the sorted of long components. The two-step feeders consist of cylinders, which make the movement of steps. The steps that are used the EN-8 materials are used to make the feeder assembly, and those are connected with the cylinders that are used to construct the up and down movements, when the cylinder makes the forward and retracts motion. The steps scoop up the components and feed them to the additive chute. The linear chute transfers the properly oriented components to the singling unit feeds the components to the machine for making further operations.

Structural and morphological instabilities of the Si(1 1 1)-7 × 7 surface during silicon growth and etching by oxygen and selenium

Using in situ reflection electron microscopy and ex situ atomic force microscopy, we have studied the morphological stability of large-scale (~10–100 μm) Si(111)-7 × 7 terraces during silicon growth and etching by oxygen and selenium. On the large-scale terraces, silicon growth at substrate temperatures T = 600–770 °C and Si deposition rates R = 0.002–0.2 BL/s proceeds in multilayer mode. Based on RMS surface roughness scaling W ∝ Θβ, we have discerned three modes of morphological instability caused by (I) effective adatom diffusion along step edges at low T and R (β ≈ 0.33), (II) effective diffusion and fast step motion along disordered “1 × 1” regions in 7 × 7 domain boundaries at intermediate T and R (β ≈ 0.2), and (III) accumulation of Si adatoms in high-atom-density “1 × 1” regions on the uppermost terraces at high T and R (β ≈ 0.5). The etching of the singular Si(111)-7 × 7 surface by oxygen leads to the slow development of multilayer morphology, while selenium-induced etching preserves flat surface morphology with periodic 2D vacancy island nucleation, growth, and coalesce, which is attributed to Se adatom diffusion. On the step-bunched surface, the Si or Se adatom diffusion to the step bunches leads to the self-organization of pyramidlike or valley-like morphology during Si growth or Se-induced etching, respectively.