Standing balance of vehicle passengers: The effect of vehicle motion, task performance on post-drive balance.

BACKGROUND: Motion platforms and driving simulators have been shown to contribute to motion sickness and a short-term increase in standing postural sway. However, no studies to date have investigated how the motion of a passenger vehicle and the performance of a task during a drive on a closed test track affects post-drive standing balance. RESEARCH QUESTIONS: What are the effects of (1) a continuous, scripted drive on a closed test track, and (2) the performance of a handheld tablet-based task during the scripted drive, on post-drive standing balance? METHODS: Fifty adults (23 males, 27 females; 40.0 ± 20.6 yr) rode in the front passenger seat of a midsized sedan on a scripted drive. Participants were assigned to one of the acceleration levels (Low, Moderate) and completed both Task and No-Task test conditions, involving a visual-based task on a handheld tablet device. Before and after each scripted drive, participants completed two standing balance exercises: 1) feet tandem, eyes open, on firm support, and 2) feet together, eyes closed, on foam support. An inertial measurement unit (IMU) captured estimates of postural trunk sway. Root-mean-square (RMS) of angular position and velocity in the anteroposterior (A/P) and mediolateral (M/L) directions, and elliptical fit and path length of sway trajectory were computed. A nonparametric analysis was performed on the balance metrics. RESULTS: Exposure to a scripted drive in a vehicle affected participants' postural sway, especially after using a handheld device during the drive. M/L RMS sway velocity and path length increased for both exercises following the scripted drive with task. Additionally, M/L RMS sway increased for the more challenging balance exercise, during which participants stood with feet together on foam support with eyes closed. SIGNIFICANCE: This study is the first to explore balance following a scripted drive on a closed test track. Changes in post-drive balance introduces potential risks to vehicle passengers; concurrent performance of a task on a handheld device further increases the likelihood that post-drive balance will be negatively affected.

A modified anaerobic digestion process with chemical sludge pre-treatment and its modelling.

Activated Sludge Models (ASMs) assume an unbiodegradable organic particulate fraction in the activated sludge, which is derived from the decay of active microorganisms in the sludge and/or introduced from wastewater. In this study, a seasonal change of such activated sludge constituents in a municipal wastewater treatment plant was monitored for 1.5 years. The chemical oxygen demand ratio of the unbiodegradable particulates to the sludge showed a sinusoidal pattern ranging from 40 to 65% along with the change of water temperature in the plant that affected the decay rate. The biogas production in a laboratory-scale anaerobic digestion (AD) process was also affected by the unbiodegradable fraction in the activated sludge fed. Based on the results a chemical pre-treatment using H2O2 was conducted on the digestate to convert the unbiodegradable fraction to a biodegradable one. Once the pre-treated digestate was returned to the digester, the methane conversion increased up to 80% which was about 2.4 times as much as that of the conventional AD process, whilst 96% of volatile solids in the activated sludge was digested. From the experiment, the additional route of the organic conversion processes for the inert fraction at the pre-treatment stage was modelled on the ASM platform with reasonable simulation accuracy.