Virtual Test Research Articles

Differences in Brain Activity During Real and Virtual Reality Motor Tasks in Normal Healthy Individuals.

This study aimed to clarify the differences between brain activity during virtual reality and real motor tasks. Twelve healthy adults participated in this study. Near-infrared spectroscopy (NIRS) was used to measure brain activity, and a total of 34 channels, 17 channels each, centred on the bilateral motor cortex, were used as measurement sites. Two types of motor tasks were used: a real Box and Block test (R-BBT) and a virtual reality Box and Block test (VR-BBT). In both motor tasks, an increase in oxy-haemoglobin (O2Hb) and a slight decrease in deoxy-haemoglobin (HHb) levels were observed in the central region of the participant's motor cortex. The O2Hb in the motor cortex during R-BBT increased at the beginning of the task, rapidly decreased, and remained at a low value. Conversely, the amount of O2Hb in the motor cortex during the VR-BBT remained high throughout the task. In addition, O2Hb in the dorsal prefrontal cortex during the VR-BBT was significantly higher than during the R-BBT. This study indicates that brain activity differs significantly between real and virtual reality motor tasks, even for similar tasks.

Increasing Accessibility to Intradialytic Cycling in Rural and Remote Settings: Program Report.

Access to exercise and rehabilitation is often lower in rural or remote areas and hemodialysis (HD) dependence imposes additional barriers. Intradialytic cycling (IDC) can improve HD-related symptoms, such as leg cramping, restless legs, and symptoms of depression, as well as physical function and fitness, but access to exercise professionals with this expertise is limited. To promote access to IDC in rural and remote HD units, we describe the implementation and initial evaluation of a novel IDC program using virtual assessment to safely prescribe and individualize IDC. We developed and piloted a protocol for virtual IDC assessment and prospectively collected metrics informed by the Reach, Effectiveness, Adoption, Implementation, and Maintenance (RE-AIM) framework to support future quality improvement activities. Rural HD units were defined as per Alberta Kidney Care North (AKC-N)'s operations. The virtual IDC program components were: HD unit education sessions, support and interest from local unit staff and those receiving HD, a bike, a supervising kinesiologist, a stable Internet connection, a nurse present during the 25-minute initial virtual assessment, and virtual follow-up every 3 to 4 weeks with the kinesiologist. The initial assessment consists of a virtual bike test where the participant performs a graded, symptom-limited cycling trial with documentation of vital signs and rating of self-perceived exertion (relative intensity). The data are used to prescribe IDC (frequency, intensity, time). The HD unit staff learn participant and bike set-up, confirm safe exercise parameters for that day, adjust the bike intensity, and take vital signs. Outcomes for evaluating the impact of the IDC program using the RE-AIM health framework were selected. Out of the 24 HD units in AKC-N, 18 units were defined as either remote or rural (75%). Four of the units (22%) adopted the program, which was less than our target of 30% of units. Individual-level participation (Reach) within those units ranged widely (1-67%) with only one unit reaching the target of at least 30% individual-level participation. Reasons for starting IDC were intradialytic cramping, restless legs, deconditioning, and boredom during HD. Reasons for non-participation were lack of interest and a desire to sleep. Routine exercise program questionnaires on health-related quality of life for program effectiveness were not consistently completed by participants. All virtual assessments were completed as per protocol with a nurse (100% fidelity); however, tests often needed to be re-scheduled due to technical issues with Wi-Fi, limited unit staffing, operational demands, and/or safety concerns. At 1 year, all 4 units continued to participate with 2 additional HD units starting the following year. Reach could be improved by introducing intradialytic exercise to individuals at HD initiation, prior to moving to their local satellite HD unit. Existing measures of program effectiveness may not be relevant to program participants or feasible to implement without an on-site exercise professional. Technical issues and navigating the busy schedules of unit staff were limitations to completing tests as scheduled. Implementing a protocolized approach with virtual support can increase accessibility to an evidence-based treatment in HD units without exercise professionals. For people requiring HD, reach may be improved with early education and exposure at HD start and with orientation sessions for staff. Adding a virtual IDC assessment day for staff as part of their routine monthly task schedule may promote institutionalization. Formalized follow-up sessions for kinesiologists and nurses to discuss program concerns would benefit the program in the future. Completion of program effectiveness measures may be improved by selecting more individualized options, for example, person-reported measures related to the individual's reason for referral.

Design and Evaluation of Maliki V-Lab: A Metaverse-Based Virtual Laboratory for Computer Assembly Learning in Higher Education

Some schools keep using online learning media even after the new normal of COVID-19 to provide broader reach for students and teachers. Online learning in practicum class requiring physical practice equipment remains a challenge. This research proposes Maliki V-Lab, a metaverse-based VR laboratory that provides practicum class for computer assembly as an online learning media platform. The developed system then evaluated for the usefulnes and sense of virtual presence. System usability was measured using the System Usability Scale (SUS) questionnaire, and virtual presence was measured using the Igroup Presence Questionnaire (IPQ) that consist four categories. The system usability test result is marginally acceptable, while virtual presence test result is acceptable for general presence, spatial presence, and expected realism category, and marginally acceptable for involvement category. Based on these results, this system can used for practical learning specifically according to the criteria that have been tested. Maliki V-Labs needs to improve the level of usability and virtual presence before it can be expanded with another practicum class and another type of respondent.

Spatial memory and learning: investigating the role of dynamic visual acuity.

The vestibular system's contribution to spatial learning and memory abilities may be clarified using the virtual Morris Water Maze Task (vMWMT). This is important because of the connections between the vestibular system and the hippocampus area. However, there is ongoing debate over the role of the vestibular system in developing spatial abilities. This study aimed to evaluate the relationship between Dynamic Visual Acuity (DVA) across three planes and spatial abilities. This cross-sectional study was conducted with 50 healthy adults aged 18 to 55 with normal stress levels and mental health and no neurological, audiological, or vestibular complaints. The Trail-Making Test (TMT) Forms A and B for the assessment of executive functions, the DVA test battery for the evaluation of visual motor functions, and the Virtual Morris Water Maze Test (vMWMT) for the assessment of spatial learning and spatial memory were performed. All participants also underwent the Benton Face Recognition Test (BFRT) and Digit Symbol Substitution Tests (DSST) to assess their relation with spatial memory. DVA values in horizontal (H-DVA), vertical (V-DVA), and sagittal (S-DVA) planes ranged from (-0.26) to 0.36 logMAR, (-0.20) to 0.36 logMAR, and (-0.28) to 0.33 logMAR, respectively. The latency of three planes of DVA was affected by vMWMT (Horizontal, Vertical, and Sagittal; Estimate: 22.733, 18.787, 13.341, respectively p < 0.001). Moreover, a moderately significant correlation was also found, with a value of 0.571 between the Virtual MWM test and BFRT and a value of 0.539 between the DSST (p < 0.001). Spatial abilities in healthy adults were significantly influenced by dynamic visual functions across horizontal, vertical, and sagittal planes. These findings are expected to trigger essential discussions about the mechanisms that connect the vestibular-visual system to the hippocampus. The original vMWMT protocol is likely to serve as a model for future studies utilizing this technology.

Multiphysics Modeling and Co-Simulation of Ship Electric Power and Propulsion Systems for Virtual Testing and Verification

Multiphysics Modeling and Co-Simulation of Ship Electric Power and Propulsion Systems for Virtual Testing and Verification

PEM: Perception Error Model for Virtual Testing of Autonomous Vehicles

PEM: Perception Error Model for Virtual Testing of Autonomous Vehicles

Determining the Mechanical Properties of Super-Elastic Nitinol Bone Staples Through an Integrated Experimental and Computational Calibration Approach.

Super-elastic bone staples have emerged as a safe and effective alternative for internal fixation. Nevertheless, several biomechanical aspects of super-elastic staples are still unclear and require further exploration. Within this context, this study presents a combined experimental and computational approach to investigate the mechanical characteristics of super-elastic staples. Two commercially available staples with distinct geometry, characterized by two and four legs, respectively, were examined. Experimental four-point bending tests were conducted to evaluate staple performance in terms of generated forces. Subsequently, a finite element-based calibration procedure was developed to capture the unique super-elastic behavior of the staple materials. Finally, a virtual bench testing framework was implemented to separate the effect of geometry from that of the material characteristics on the mechanical properties of the devices, including generated force, strain distribution, and fatigue behavior. The experimental tests indicated differences in the force vs. displacement curves between staples. The material calibration procedure revealed marked differences in the super-elastic properties of the materials employed in staple 1 and staple 2. The results obtained from the virtual bench testing framework have showed that both geometric features and material characteristics had a substantial impact on the mechanical properties of the device, especially on the generated force, whereas their effect on strain distribution and fatigue behavior was comparatively less pronounced. To conclude, this study advances the biomechanical understanding of Nitinol super-elastic staples by separately investigating the impact of geometry and material characteristics on the mechanical properties of two commercially available devices.

(Invited) Contribution of Oxygen Reduction to Mg Corrosion: Computational Modelling

The magnesium corrosion mechanisms are still a matter of discussions. Independent from that there is agreement that the cathodic behaviour is based on the superposition of water and oxygen reduction reactions [1]. Accessing the amount of cathodic reaction contributions to the entire corrosion current density via experiment is challenging [2,3]. In a recent work of Wang et al. [4] a combined experimental and computational approach was utilized to explore the superposition of cathodic reactions during Mg corrosion in aqueous electrolytes for different iron impurity situations. The study shows significant variation of percentual contribution of oxygen reduction to the cathodic current for the studied purity levels.In this work a computational modelling approach is presented accordingly. It is based on the numerical model developed by Höche [5] and enables virtual local electrochemical testing and computational assessment of (electro-)chemical system and transport descriptors. Respective simulation results show, how corrosion and testing system parameters change the measured oxygen approach curves. Subsequently a multi-parameter calibration enabled the quantification of oxygen reduction reaction to the entire corrosion process. The reproduction of experimental results and strategies for model improvement are discussed. REFERENCES: [1] Höche, D., Blawert, C., Lamaka, S. V., Scharnagl, N., Mendis, C., & Zheludkevich, M. L., The effect of iron re-deposition on the corrosion of impurity-containing magnesium. Physical Chemistry Chemical Physics, 18-2 (2016), 1279-1291.[2] Yasakau, K. A., Höche, D., Lamaka, S. L., Ferreira, M. G., & Zheludkevich, M. L., Kelvin microprobe analytics on iron-enriched corroded magnesium surface. Corrosion, 73-55 (2017), 583-595.[3] E.L. Silva, S.V. Lamaka, D. Mei, M.L. Zheludkevich, The Reduction of Dissolved Oxygen During Magnesium Corrosion, ChemistryOpen, 7 (2018) 664-668.[4] C. Wang, W. Xu, D. Höche, M.L. Zheludkevich, S.V. Lamaka, Exploring the contribution of oxygen reduction reaction to Mg corrosion by modeling assisted local analysis, Journal of Magnesium and Alloys, 11 (2023) 100-109.[5] Höche D., Simulation of corrosion product deposit layer growth on bare magnesium galvanically coupled to aluminum. Journal of the electrochemical society, 162-1 (2014), C1. ACKNOWLEDGEMENTS: C. Wang, W. Xu, thank China Scholarship Council for the funding, grants no. 201806310128 and 201908510177

Human motor augmentation with an extra robotic arm without functional interference.

Extra robotic arms (XRAs) are gaining interest in neuroscience and robotics, offering potential tools for daily activities. However, this compelling opportunity poses new challenges for sensorimotor control strategies and human-machine interfaces (HMIs). A key unsolved challenge is allowing users to proficiently control XRAs without hindering their existing functions. To address this, we propose a pipeline to identify suitable HMIs given a defined task to accomplish with the XRA. Following such a scheme, we assessed a multimodal motor HMI based on gaze detection and diaphragmatic respiration in a purposely designed modular neurorobotic platform integrating virtual reality and a bilateral upper limb exoskeleton. Our results show that the proposed HMI does not interfere with speaking or visual exploration and that it can be used to control an extra virtual arm independently from the biological ones or in coordination with them. Participants showed significant improvements in performance with daily training and retention of learning, with no further improvements when artificial haptic feedback was provided. As a final proof of concept, naïve and experienced participants used a simplified version of the HMI to control a wearable XRA. Our analysis indicates how the presented HMI can be effectively used to control XRAs. The observation that experienced users achieved a success rate 22.2% higher than that of naïve users, combined with the result that naïve users showed average success rates of 74% when they first engaged with the system, endorses the viability of both the virtual reality-based testing and training and the proposed pipeline.

DEM analysis of the effect of geocell on splitting tensile behavior of asphalt mixture based on multi-phase model

Herein, an investigation was conducted upon the reinforcement of geocell on the splitting tensile process of asphalt mixture using laboratory tests and the discrete element method (DEM). Micromechanical modeling of geocell-reinforced asphalt mixture and virtual splitting tensile test was built using PFC3D based on the vital material features and mechanical properties of different ingredients (e.g., the three-dimensional irregular shapes and elastic properties of coarse aggregates and geocell, the viscoelastic properties of asphalt mastic, and the random distribution of air voids in asphalt mastic). Meanwhile, the parameters of the DE model were determined by splitting tensile test, and the effects of geocell on the splitting tensile process of contact force, displacement and stress were evaluated through the virtual splitting test. The results indicated the efficiency of the built DE model and virtual test in effectively predicting the splitting process of geocell-reinforced asphalt mixture. Besides, geocell acted mainly in the falling stage of the load-displacement curve during the splitting process, where the contact force distribution of each phase component shifted from the lower to the higher range, and the effect between coarse aggregates was the greatest, followed between coarse aggregate and asphalt mastic, with the least within asphalt mastic. Further, the maximum displacement of asphalt mixture in the X and Y directions was reduced by the geocell, significantly constraining the coarse aggregate and mastic in geocell-reinforced layer. In addition, the stress in the splitting center of asphalt mixture was greater than that at the sides, and the stress within the geocell of the reinforced layer was significantly lower compared to the unreinforced layer, especially in the falling stage. Overall, the present results forge a theoretical basis for the tensile performance of geocell-reinforced asphalt mixture from the microscopical perspective.

Calibration of an expeditious terramechanics model using a higher‐fidelity model, Bayesian inference, and a virtual bevameter test

AbstractThe soil contact model (SCM) is widely used in practice for off‐road wheeled vehicle mobility studies when simulation speed is important and highly accurate results are not a main concern. In practice, the SCM parameters are obtained via a bevameter test, which requires a complex apparatus and experimental procedure. Here, we advance the idea of running a virtual bevameter test using a high‐fidelity terramechanics simulation. The latter employs the “continuous representation model” (CRM), which regards the deformable terrain as an elasto‐plastic continuum that is spatially discretized using the smoothed particle hydrodynamics method. The approach embraced is as follows: a virtual bevameter test is run in simulation using CRM terrain to generate “ground truth” data; in a Bayesian framework, this data is subsequently used to calibrate the SCM terrain. We show that (i) the resulting SCM terrain, while leading to fast terramechanics simulations, serves as a good proxy for the more complex CRM terrain; and (ii) the SCM‐over‐CRM simulation speedup is roughly one order of magnitude. These conclusions are reached in conjunction with two tests: a single wheel test, and a full rover simulation. The SCM and CRM simulations are run in the open‐source software Chrono. The calibration is performed using PyMC, which is a Python package that interactively communicates with Chrono to calibrate SCM. The models and scripts used in this contribution are available as open source for unfettered use and distribution in a public repository.

A computational study on efficient yield surface calibrations using a crystal plasticity spectral solver

A computational framework is presented, capable of calculating virtual loads using the spectral solver in the DAMASK software for crystal plasticity simulations in desired stress directions. Calculations are used for the calibration of yield surfaces. The required spatial resolution is assessed based on a comparison with the previously published crystal plasticity finite-element method (CPFEM) and experimental results for three different aluminum alloys (AA1050, AA3103O, and AA3103H18) with 1000 and 2500 grains in a representative volume element. The results of the crystal plasticity fast Fourier transform (CPFFT) method agree well with CPFEM. The elongated grain morphology of the AA3103H18 alloy was found to have a small effect on predicted anisotropy. An analysis was made of how many tests are required for proper calibration of the Yld2004-18p orthotropic yield surface. It was found that 32 virtual tests, along either uniformly distributed strain rate or stress directions but obeying the orthotropic symmetry of the Yld2004-18p yield surface, make a good compromise between accuracy and computation time. Randomly chosen directions have a significantly larger error and require more virtual tests for a similarly good calibration of the yield surface. Since a preselected set of strain–rate directions does not require extra iterations, it is the preferred choice for the calibration of the full stress-based Yld2004-18p.

1 experimental and numerical evaluation of residual mechanical performance of carbon/epoxy laminated coupons after integration of solid battery cells for aeronautical applications

The present study deals with a numerical and experimental evaluation of the residual mechanical performance of a quasi-isotropic carbon/epoxy laminated composite plate in which solid battery cells have been integrated. Firstly, the mechanical properties of the multifunctional Reinforced Multilayer Stack (RMS) battery cells have been determined thanks to dedicated multi-instrumented tests, while those of the AS4/8552 composite material have been extracted from the literature and validated by comparisons with tensile tests on plates without battery, considered as a reference case. Then, on the basis of the recommendations obtained from a virtual test campaign using FE simulations, a 16-ply laminated composite plate containing 6 solid battery cells was manufactured with a modified curing cycle that preserves the electrical properties of the batteries while ensuring the mechanical properties of the composite material. Various control methods, such as CT-scan and optical analysis, were used to demonstrate the promising quality of the manufactured composite coupon with embedded cells. Finally, a mechanical tensile test was carried out to experimentally determine the reduction in mechanical properties. The analysis of such a test with non-linear FE simulation has allowed a better understanding of the damage and failure process when solid battery cells are integrated into high performance laminated composite structures designed for the aeronautical industry.

Simulation of Autonomous Driving for a Line-Following Robotic Vehicle: Determining the Optimal Manoeuvring Mode

Mobile robotic systems offer valuable test platforms due to their shared features with autonomous vehicles, including features such as sensor technologies, navigation algorithms, and control systems. However, constraints in laboratory environments or technical resources, along with the need for extensive testing, often necessitate the use of virtual test laboratories. While line-following is a widely preferred application in mobile robotics, research on this topic within virtual laboratories is limited. This study pioneers the use of a car-like robotic vehicle in conducting line-following tests within a virtual laboratory environment. To facilitate these tests, a virtual simulator was developed to meet the requirements of realistic simulations. This simulator includes simulated elements, such as roads and environmental features, along with virtual sensors designed to collect and process dynamic motion data. An exceptional aspect of this study is its ability to collect consistent dynamic travel data by sampling realistic sensor information within a virtual environment. The developed line-following algorithm employs a controller to minimise lateral deviation while the robotic vehicle follows a road line during its movement. The study conducted virtual driving tests using two different manoeuvre modes on four distinct road segments, exploring how the manoeuvring style influences the driving quality. It was demonstrated that in the low manoeuvre mode, the ride is more comfortable, but exhibits a greater route deviation due to reduced oscillation, while the high manoeuvre mode exhibits the opposite behaviour.

Building energy performance metamodels for district energy management optimisation platforms

Reactive control strategies lack the flexibility necessary to optimize the operational costs of buildings and district systems. To overcome this limitation and to enable the transition to model predictive control strategies (MPC), the development of dedicated control platforms and models is required. Predictive models for district systems management should provide supply and demand side integrated modelling, high accuracy, generalization capacity and reduced computational times. However, traditionally available MPC solutions do not meet these requirements as simplified models offer short computational times but lack the required accuracy; detailed physics-based models provide satisfactory generalization but at the expense of high computational costs; and the generalization capacity of data models is constrained by the quality and availability of data. In contrast, metamodels developed through the combined use of physics-based models and machine learning techniques offer a powerful alternative at reduced computational cost. This paper describes an upgraded Integrated District Model concept developed through co-simulation coupling metamodels of buildings with a district heating infrastructure Modelica model. Furthermore, the process to produce the metamodels and optimization engine required to generate demand flexibility optimization functionalities for the buildings of the Stepa Stepanovic subnetwork (Belgrade) is depicted. Starting from the development of metamodels of instances of specific buildings (residential and educational use) the process was expanded to provide additional generalization to define, (1) a generic metamodel with the capacity to reproduce the behaviour of any instance of building of the residential typology, and (2) metamodels with generalization capacity in relation to operational settings. As part of this process the potential of several machine learning algorithms (e.g Support Vector Machines, etc) was evaluated including the latest ensemble boosting methods (e.g. Adaboost, Gradient Boosting and Extreme Gradient Boosting) with comparatively low use in the building simulation community. Finally, a virtual test bed consisting in metamodels coupled to an optimization engine based on genetic algorithms, was implemented, and compared to a traditional Physics-based model MPC solution (EnergyPlus-GENOPT), to evaluate the potential of the developed building level optimization functionalities. The metamodels and optimization engine were able to reproduce the optimized settings identified by the EnergyPlus-GENOPT MPC solution with cost savings potentials of 5–10%.

The method of virtual bench tests conducting to analyze the vehicle technical characteristics compatibility to detect and prevent the risk of resonant phenomena in the sprung cab

BACKGROUND: A relevant issue when designing vehicles with multiple levels of suspension systems is collaborative operation of these systems, which ensures the required vehicle dynamics and smoothness parameters, as well as the absence of risk for the occurrence of resonance phenomena. The vehicle cab is a dynamic system with 6 degrees of freedom, so its oscillatory motions have a complex spatial character with the oscillation energies overflow from one direction to another. The solving of problems of the sprung cab dynamics should be conducted in a spatial nonlinear formulation, which makes it possible to take into account the phenomena of redistribution of oscillation energy between the directions of space. This approach can be put into operation with simulation modeling methods through creating a spatial virtual rig of the cab with a suspension system and modeling its dynamics with the application of appropriate external inputs.&#x0D; AIM: Development of the method of using virtual tests to analyze the compatibility of technical characteristics of the cab suspension system, the frame system and the primary vehicle suspension systems to detect and prevent the risk of resonant phenomena in the cab.&#x0D; METHODS: Building a virtual test rig of a vehicle cab as a multibody dynamics system of connected bodies in space, mounted at the movable vehicle frame with spring-dampers. Virtual tests are conducted by simulation modeling methods according to the method for analyzing nonlinear phenomena when spatial resonances occur in the secondary suspension system of a vehicle cab.&#x0D; RESULTS: The method of vehicle cab virtual tests conducting for analyzing oscillatory processes occurring in the cab, including resonances, using a virtual test rig in a multibody dyamics software package.&#x0D; CONCLUSION: The developed method ensures an ability to take measures to detect and prevent the risk of spatial resonance phenomena in the vehicle cab at all stages of the components design and the cab suspension systems study.

Development and research of the model of a wheel-legged robot

BACKGROUND: The development of robots capable of moving in both walking and wheeled modes and distinguishing with a simple design from the already developed robots is a relevant task for some recent years. In order for such a robot to have scientific and commercial success, it is necessary for it to be as structurally complex, smooth, reliable and inexpensive as its wheeled equivalent and, in addition, to be able to move stably and quickly over terrain that is impassable for wheeled robots. The robot dynamics is modeled with the Universal Mechanism and the MATLAB/Simulink software packages. The results of virtual tests of the robot in main motion modes (straight-line motion, turning, step climbing) are given in the paper.&#x0D; AIM: Increasing the mobility of a wheel-legged robot, equipped with the pseudo-walking propulsion system, using reasonable control laws.&#x0D; METHODS: In order to evaluate ride performance of the studied robot, methods of numerical simulation of its motion based on the multibody dynamics software packages are used.&#x0D; RESULTS: The maximal velocity of stable straight-line motion, the turning velocity and the height of the largest climbed step were obtained for the robot with given power of engines.&#x0D; CONCLUSION: The model of the new mobile robot equipped with the simple-designed propulsion system has been developed. This model demonstrated high cross-country abilities and other mobility indicators according to the results of virtual tests.

Using virtual reality-based neurocognitive testing and eye tracking to study naturalistic cognitive-motor performance

Natural human behavior arises from continuous interactions between the cognitive and motor domains. However, assessments of cognitive abilities are typically conducted using pen and paper tests, i.e., in isolation from “real life” cognitive-motor behavior and in artificial contexts. In the current study, we aimed to assess cognitive-motor task performance in a more naturalistic setting while recording multiple motor and eye tracking signals. Specifically, we aimed to (i) delineate the contribution of cognitive and motor components to overall task performance and (ii) probe for a link between cognitive-motor performance and pupil size. To that end, we used a virtual reality (VR) adaptation of a well-established neurocognitive test for executive functions, the ‘Color Trails Test’ (CTT). The VR-CTT involves performing 3D reaching movements to follow a trail of numbered targets. To tease apart the cognitive and motor components of task performance, we included two additional conditions: a condition where participants only used their eyes to perform the CTT task (using an eye tracking device), incurring reduced motor demands, and a condition where participants manually tracked visually-cued targets without numbers on them, incurring reduced cognitive demands. Our results from a group of 30 older adults (>65) showed that reducing cognitive demands shortened completion times more extensively than reducing motor demands. Conditions with higher cognitive demands had longer target search time, as well as decreased movement execution velocity and head-hand coordination. We found larger pupil sizes in the more cognitively demanding conditions, and an inverse correlation between pupil size and completion times across individuals in all task conditions. Lastly, we found a possible link between VR-CTT performance measures and clinical signatures of participants (fallers versus non-fallers). In summary, performance and pupil parameters were mainly dependent on task cognitive load, while maintaining systematic interindividual differences. We suggest that this paradigm opens the possibility for more detailed profiling of individual cognitive-motor performance capabilities in older adults and other at-risk populations.

Assessment of Numerical Captive Model Tests for Underwater Vehicles: The DARPA SUB-OFF Test Case

During the early design stage of an underwater vehicle, the correct assessment of its manoeuvrability is a crucial task. Conducting experimental tests still has high costs, especially when dealing with small vehicles characterized by low available budget. In the current investigation, virtual towing tank tests are simulated using the open-source OpenFOAM library in order to assess the reliability of CFD methods for the prediction of hydrodynamic forces and moments. A well-known case study, the Defence Advanced Research Projects Agency (DARPA) SUB-OFF model, is used, and the outcomes are compared to the experimental results available in the literature. Five different configurations are investigated for pure drift tests, rudder tests and pure rotation in both vertical and horizontal plane. The results show an overall good agreement with the experimental data with a quite low demanding mesh arrangement of 3M cells, a favourable balance between accuracy and computational time. In more detail, the expected error in the most significant forces during manoeuvres is less than 2% for the fully appended configuration (the submarine real operative condition), whereas the accuracy is moderately reduced for the barehull configuration (a case not representative of a real hull) with an expected error of 15%. A possible reason for the differences observed could be attributed to the description of the two streamwise vortices generated when manoeuvring. Apart from the lateral force and yaw moment, the results of the longitudinal force are also presented, having a greater disparity when compared to the experimental data. Nevertheless, the longitudinal force has no important role for the purpose of making stability and control predictions. The study contributes to the validation and consolidation of CFD methods, offering insights into their accuracy and limitations for practical applications in underwater vehicles.

Estimation of linear hydrodynamic derivatives of a 37000 tdw chemical tanker using virtual captive model tests

Forecasting the hydrodynamic properties of a ship is crucial for assessing its maneuvering capabilities. This study presents the results of static drift and circular motion simulations conducted on a 37000 tdw chemical tanker. The calculations were carried out using the ISIS-CFD solver, accessible through the FineTM/Marine academic license provided by NUMECA. The flow solution was obtained by numerically solving the Reynolds-Averaged Navier Stokes equations, employing the k-ω Shear Stress Transport (SST) model to represent turbulence. The simulation results were used to determine the linear hydrodynamic derivatives, which were then compared with hydrodynamic derivatives estimated with empirical formulas proposed by Clarke et. al. [1] and Tribon Initial Design module in the absence of experimental results.