When Less Is More: Investigating Factors Influencing the Distraction Effect of Virtual Reality From Pain

Virtual reality (VR) is a powerful method of redirecting attention away from pain. Yet, little is known about which factors modulate the size of this distraction effect. The aim of this study was to investigate the role of cognitive load and inter-individual differences in the cognitive and affective domain on heat pain thresholds during a VR game. Ninety healthy participants (mean age ± SD: 23.46 ± 3.28; 50% identified as male and 50% as female) played a low and high load version of a VR game while heat pain thresholds and heart rate were recorded. The effects of cognitive load were assessed by computing the difference in pain thresholds between the high and low load condition for each participant. In addition, we computed the difference in heart rate variability (HRV) measures between both conditions to explore whether these would be correlated with the difference in heat pain thresholds. Prior to the VR session, participants completed questionnaires about their emotional distress, pain-related cognitions, and different executive functioning tasks. Contrary to our expectations, not all participants benefitted from a higher load in terms of distraction from pain. Logistic regression analysis revealed that participants who reported more emotional distress were more likely to exhibit higher pain thresholds in the low relative to the high load condition. Accordingly, these participants tended to show marginally higher HRV in the low compared to the high load condition. Our study demonstrates that the potential benefits of an increased cognitive load in VR on pain sensitivity depends on individual differences in affective state.

Performance Testing of istSOS Under High Load Scenarios

In the last 20 years, a mainstream in Earth information and decision making has been drawn by the vision of the digital earth that calls for 3D representation, interoperability and modelling. In this context, the time dimension is essential but despite its importance, not many open standards and implementations are available. The Sensor Observation Service from the Open Geospatial Consortium is one of them and was specifically designed to collect, store and share timeseries of observations from sensors. To better understand the performance and limitation of one software implementation of this standard in real cases, this study executed a load testing of the istSOS application under a high load condition, characterized by a high number of concurrent users, in three cases mimicking existing monitoring networks. The results, in addition to providing reference values for future similar tests, show the general capacity of istSOS in meeting the INSPIRE quality of service requirements and in offering good performance with less than 500 concurrent users. When the number of concurrent users increases to 1000 and 2000, only 80% of the response times are below 30 seconds, performance that is unsatisfactory in most modern usages.

Molecular Dynamics Simulation on the Friction Properties of Couette Flow With Superhydrophobic Rough Surfaces Under Different Load

To reveal the effect of superhydrophobic rough surface on the friction properties, molecular dynamics simulations are used to study the friction properties of Couette flow. In particular, the influence of load on the flow properties is considered in this work. Results show that there is a critical load (Pcrit), and the friction-reduction properties of superhydrophobic surfaces with stripes are only presented when the load is smaller than the Pcrit. With the decrease in the distance between stripes, the Pcrit is increased. Under a low load, the friction force is increased with increasing the distance between stripes. However, under high load condition we observe an opposite trend. The height of stripe has little impacts on the Pcrit.

Investigating the Immediate and Cumulative Effects of Isometric Squat Exercise for Different Weight Loads on Intraocular Pressure: A Pilot Study

Background: The execution of resistance exercise against heavy loads promotes an acute intraocular pressure (IOP) rise, which has detrimental effects on ocular health. However, the effect of load on the IOP behavior during exercise remains unknown due to technical limitations. Hypotheses: IOP monitoring during isometric squat exercise permits assessment of IOP behavior during physical effort. Second, greater loads will induce a higher IOP rise. Study Design: Randomized cross-sectional study. Level of Evidence: Level 2. Methods: Twenty-six young adults (13 women, 13 men) performed an isometric squat exercise against 3 loads relative to their maximum capacity (low, medium, and high). IOP was measured before, during (1 measurement every 6 seconds), and after exercise (10 seconds of recovery). Results: There was a progressive IOP rise during exercise, which was dependent on the load applied (Bayes factor10 >100). Higher IOP values were found in the high load condition in comparison with the medium (mean IOP difference = 1.5 mm Hg) and low (mean IOP difference = 3.1 mm Hg) conditions, as well as when the medium load was compared with the low load condition (mean IOP difference = 1.6 mm Hg). Men reached higher IOP values in comparison with women during the last measurements in the high load condition. Ten seconds of recovery were enough to obtain IOP values similar to baseline levels. Conclusion: Isometric squat exercise induces an immediate and cumulative IOP elevation, which is positively associated with the load applied. These IOP increments return to baseline values after 10 seconds of recovery, and men demonstrate a more accentuated IOP rise in comparison with women when high levels of effort are accumulated. Clinical Relevance: These findings may help in better management of different ocular conditions and highlight the importance of an individualized exercise prescription in clinical populations.

Research on the precision loss of ball screw with short-time overload impact

Ball screw is the driving functional component most frequently used for the precision equipment. To a certain extent, the transmission accuracy of precision equipment is affected by the position error of ball screw caused by the elastic–plastic deformation between ball and raceway under the overload impact. This article aims to investigate the precision loss of ball screw considering short-time overload impact. A novel precision loss model combining the Hertzian and Thornton contact theories is established to describe the variations in the axial deformation depths. Thus, the axial precision loss can be defined as the differential value between the initial no-loading travel variations and the loading stroke variations caused by the axial plastic deformation of raceway. Meanwhile, the maximum stress and the residual plastic deformation for four couples of ball-raceway materials are analyzed. Furthermore, the relationship between the precision loss and the elastic–plastic deformation is studied by the theoretical analysis and experiments. The results show that the position and precision is affected indeed by the contact deformation. The position and precision loss of the nut relative to the screw increases with the increase in the axial load. The results can help to provide the prediction for the precision life of ball screw operating in high-load condition.

Investigating Fuel Condensation Processes in Low Temperature Combustion Engines

Condensation of gaseous fuel is investigated in a low temperature combustion (LTC) engine fueled with double direct-injected diesel and premixed gasoline at two load conditions. Possible condensation is examined by considering real gas effects with the Peng–Robinson (PR) equation of state (EOS) and assuming thermodynamic equilibrium of the two fuels. The simulations show that three representative condensation events are observed. The first two condensations are found in the spray some time after the two direct injections (DI), when the evaporative cooling reduces the local temperature until phase separation occurs. The third condensation event occurs during the late stages of the expansion stroke, during which the continuous expansion sends the local fluid into the two-phase region again. Condensation was not found to greatly affect global parameters, such as the average cylinder pressure and temperature mainly because, before the main combustion event, the condensed phase was converted back to the vapor phase due to compression and/or first stage heat release. However, condensed fuel is shown to affect the emission predictions, including engine-out particulate matter (PM) and unburned hydrocarbons (UHCs). Specifically, it was shown that the condensed fuel comprised more than 95% of the PM in the low load condition, while its contribution was significantly reduced at the high load condition due to higher temperature and pressure conditions.