The Tracking and Frequency Measurement of the Sway of Leafless Deciduous Trees by Adaptive Tracking Window Based on MOSSE

The tree sway frequency is an important part of the dynamic properties of trees. In order to obtain trees sway frequency in wind, a method of tracking and measuring the sway frequency of leafless deciduous trees by adaptive tracking window based on MOSSE was proposed. Firstly, an adaptive tracking window is constructed for the observed target. Secondly, the tracking method based on Minimum Output Sum Of Squared Error Filter (MOSSE) is used to track tree sway. Thirdly, Fast Fourier transform was used to analyze the horizontal sway velocity of the target area on the trees, and the sway frequency was determined. Finally, comparing the power spectral densities (PSDs) of the x axis acceleration measured by the accelerometer and PSDs of the x axis velocity measured by the video, the fundamental sway frequency measured by the accelerometer is equal to the fundamental sway frequency measured by video. The results show that the video-based method can be used successfully for measuring the sway frequency of leafless deciduous trees.

Intermittent short-arm centrifugation is a partially effective countermeasure against upright balance deterioration following 60-day head-down tilt bed rest

This study investigated whether artificial gravity (AG), induced by short-radius centrifugation, mitigated deterioration in standing balance and anticipatory postural adjustments (APAs) of trunk muscles following 60-day head-down tilt bed rest. Twenty-four participants were allocated to one of three groups: control group (N=8); 30 minutes continuous AG daily (N=8); intermittent 6x5 minutes AG daily (N=8). Before and immediately after bed rest, standing balance was assessed in four conditions: eyes open and closed on both stable and foam surfaces. Measures including sway path, root-mean-square, and peak sway velocity, sway area, sway frequency power, and sway density curve were extracted from the centre of pressure displacement. APAs were assessed during rapid arm movements using intramuscular or surface electromyography electrodes of the rectus abdominis, obliquus externus and internus abdominis, transversus abdominis, erector spinae at L1, L2, L3, and L4 vertebral levels, and deep lumbar multifidus muscles. The relative latency between the EMG onset of the deltoid and each of the trunk muscles was calculated. All three groups had poorer balance performance in most of the parameters (all P<0.05) and delayed APAs of the trunk muscles following bed rest (all P<0.05). Sway path and sway velocity were deteriorated, and sway frequency power was less in those who received intermittent AG than in the control group (all P<0.05), particularly in conditions with reduced proprioceptive feedback. These data highlight the potential of intermittent AG to mitigate deterioration of some aspects of postural control induced by gravitational unloading, but no protective effects on trunk muscle responses were observed.

Role of Body Roll in Caravan Fishtailing

During towing of a caravan or trailer it is not uncommon that the trailer sways back and forth as a result of steering input, crosswind or one of many other causes. Normally there is sufficient damping in the oscillations to realign the trailer with the tow vehicle. On some occasions the swaying enters an uncontrollable phase where the sway amplitude increases at each cycle. This paper examines the contribution of body roll of caravans to the out-of-control sway. The paper proposes resonance of fundamental body roll frequency with the sway frequency as a significant contributing factor. It also proposes that body roll can control sway amplitude helping to explain the out-of-control condition. There are some keys offered that may interest caravan manufacturers and caravan owners alike.

Immediate Effect of Transcranial Direct Current Stimulation Combined with Functional Electrical Stimulation on Plantar Distribution and Body Sway Frequency in a Patient with Hemiparesis from Stroke: A Case Report

Objectives: The present study aimed to evaluate the immediate effect of a single session of anodal transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) combined with functional electrical stimulation (FES) of the tibialis anterior (TA) muscle on plantar distribution and body sway frequency in an individual with hemiparesis stemming from a stroke. A further aim was to determine whether the effects of the combination of stimulation techniques would lead to greater improvement than the techniques administered separately. Methods: The therapy was conducted with one 60-year-old male with right-side stroke and complete, but disproportional hemiparesis with brachial predominance on the left side, 42 months elapsed since the event and severe Fugl-Meyer score. The patient was submitted to four different randomly performed intervention protocols with a 48-hour intervention between sessions: 1) anodal tDCS + sham FES + active TA contraction; 2) sham tDCS + active FES + active TA contraction; 3) anodal tDCS + active FES + active TA contraction; 4) sham tDCS + sham FES + active TA contraction). TDCS was administered for 20 minutes with the anode over C4 and the cathode over the supraorbital region on the contralateral side and FES was administered over the left TA. The evaluation of plantar distribution was performed with a foot-pressure platform and body sway frequency was evaluated using a force plate before and after each protocol. Results: Beneficial changes occurred in the area of contact of the left hindfoot and right forefoot following intervention protocols 1, 2 and 3 and a reduction in body sway frequency occurred under all data acquisition conditions after protocols 1 and 2. Conclusion: The use of tDCS (combined and alone) and the use of FES contributed to improvements in plantar distribution and body sway frequency in a stroke survivor with hemiparesis. The use of tDCS either alone or combined with FES achieved better results than the use of FES alone.

Balance and Gait Represent Independent Domains of Mobility in Parkinson Disease

Background The Instrumented Stand and Walk (ISAW) test, which includes 30 seconds of stance, step initiation, gait, and turning, results in many objective balance and gait metrics from body-worn inertial sensors. However, it is not clear which metrics provide independent information about mobility. Objective It was hypothesized that balance and gait represent several independent domains of mobility and that not all domains would be abnormal in individuals with Parkinson disease (PD) or would change with levodopa therapy. Design This was a cross-sectional study. Methods A factor analysis approach was used to identify independent measures of mobility extracted from the ISAW in 100 participants with PD and 21 control participants. First, a covariance analysis showed that postural sway measures were independent of gait measures. Then, the factor analysis revealed 6 independent factors (mobility domains: sway area, sway frequency, arm swing asymmetry, trunk motion during gait, gait speed, and cadence) that accounted for 87% of the variance of performance across participants. Results Sway area, gait speed, and trunk motion differed between the PD group in the off-levodopa state and the control group, but sway frequency (but not sway area) differed between the PD group in the off-levodopa state and the control group. Four of the 6 factors changed significantly with levodopa (off to on): sway area, sway frequency, trunk motion during gait, and cadence. When participants were on levodopa, the sway area increased compared with off levodopa, becoming more abnormal, whereas the other 3 significant metrics moved toward, but did not reach, the healthy control values. Limitations Exploratory factor analysis was limited to the PD population. Conclusions The different sensitivity various balance and gait domains to PD and to levodopa also support neural control of at least 6 independent mobility domains, each of which warrants clinical assessment for impairments in mobility.

Control of a gantry crane using input-shaping schemes with distributed delay

This paper presents simulation and real-time implementation of input-shaping schemes with a distributed delay for control of a gantry crane. Both open-loop and closed-loop input-shaping schemes are considered. Zero vibration and zero vibration derivative input shapers are designed for performance comparison in terms of trolley position response and level of sway reduction. Simulation and experimental results have shown that all the shapers are able to reduce payload sway significantly while maintaining satisfactory position response. Investigations with different cable lengths that correspond to ±20% changes in the sway frequency have shown the distributed delay-based shaper has asymmetric robustness behaviour. The shaper provides highest robustness for the case of 20% increase in the sway frequency but lower robustness for the case of 20% decrease. However, other schemes give symmetric robustness behaviour for both cases.

Positioning Performance Comparison Between Collocated Slider-Driven PZT Actuators and Conventional Suspension-Driven Actuators

The recording density of hard disk drives is achieving the physical limit due to the recording magnet size limitations. Therefore, the bit density BPI (Bits per inch) is saturated. The residual aim is to increase track density TPI (tracks per inch), because reducing mechanical track misregistration has a possibility of increasing TPI. The Dual Stage Actuator using a PZT microactuator which enables better positioning accuracy, is widely used in 3.5 inch high density drives. The latest PZT actuator called a “Milli” actuator drives the whole suspension. However, the mass of the suspension is around several milli-grams, thus the reaction force of PZT driving sometimes causes excitation to attached arm resonance at 8–9 kHz. In addition, the fundamental resonance frequency of a milli-actuator is around 20–25 kHz, the sway frequency of whole suspension.