Investigating the n=1 and n=2 error fields in W7-X using the newly accelerated FIELDLINES code

No fusion device can be created without any uncertainty; there is always a slight deviation from the geometric specification. These deviations can add up create a deviation of the magnetic field. This deviation is known as the (magnetic) error field. Correcting these error fields is desired as they cause asymmetries in the divertor loads and can thus cause damage to the device if they grow too large. These error fields can be defined by their toroidal (n) and poloidal number (m). The correction of the n = 1 and n = 2 fields in Wendelstein 7-X (W7-X) is investigated in this work. This investigation focuses on field line diffusion to the divertor, a proxy for divertor heat flux. Such work leverages the 25x speedup obtained through the implementation of a new particle-wall collision model. The n = 1 and n = 2 error fields of the as-built coils model of W7-X are corrected by scanning phase and amplitude of the trim and control coils. Reductions in the divertor load asymmetry by factors of four are demonstrated using error field correction. It is found that the as-built coils model has a significantly lower m⁄n = 1⁄1 error field than found in experiments.

Remote Patient Monitoring with Wearable Sensors Following Knee Arthroplasty

(Background) Inertial Measurement Units (IMUs) provide a low-cost, portable solution to obtain functional measures similar to those captured with three-dimensional gait analysis, including spatiotemporal gait characteristics. The primary aim of this study was to determine the feasibility of a remote patient monitoring (RPM) workflow using ankle-worn IMUs measuring impact load, limb impact load asymmetry and knee range of motion in combination with patient-reported outcome measures. (Methods) A pilot cohort of 14 patients undergoing primary knee arthroplasty for osteoarthritis was prospectively enrolled. RPM in the community was performed weekly from 2 up to 6 weeks post-operatively using wearable IMUs. The following data were collected using IMUs: mobility (Bone Stimulus and cumulative impact load), impact load asymmetry and maximum knee flexion angle. In addition, scores from the Oxford Knee Score (OKS), EuroQol Five-dimension (EQ-5D) with EuroQol visual analogue scale (EQ-VAS) and 6 Minute Walk Test were collected. (Results) On average, the Bone Stimulus and cumulative impact load improved 52% (p = 0.002) and 371% (p = 0.035), compared to Post-Op Week 2. The impact load asymmetry value trended (p = 0.372) towards equal impact loading between the operative and non-operative limb. The mean maximum flexion angle achieved was 99.25° at Post-Operative Week 6, but this was not significantly different from pre-operative measurements (p = 0.1563). There were significant improvements in the mean EQ-5D (0.20; p = 0.047) and OKS (10.86; p < 0.001) scores both by 6 weeks after surgery, compared to pre-operative scores. (Conclusions) This pilot study demonstrates the feasibility of a reliable and low-maintenance workflow system to remotely monitor post-operative progress in knee arthroplasty patients. Preliminary data indicate IMU outputs relating to mobility, impact load asymmetry and range of motion can be obtained using commercially available IMU sensors. Further studies are required to directly correlate the IMU sensor outputs with patient outcomes to establish clinical significance.

Exoskeleton Application to Military Manual Handling Tasks

Objective The aim of this review was to determine how exoskeletons could assist Australian Defence Force personnel with manual handling tasks. Background Musculoskeletal injuries due to manual handling are physically damaging to personnel and financially costly to the Australian Defence Force. Exoskeletons may minimize injury risk by supporting, augmenting, and/or amplifying the user’s physical abilities. Exoskeletons are therefore of interest in determining how they could support the unique needs of military manual handling personnel. Method Industrial and military exoskeleton studies from 1990 to 2019 were identified in the literature. This included 67 unique exoskeletons, for which Information about their current state of development was tabulated. Results Exoskeleton support of manual handling tasks is largely through squat/deadlift (lower limb) systems (64%), with the proposed use case for these being load carrying (42%) and 78% of exoskeletons being active. Human–exoskeleton analysis was the most prevalent form of evaluation (68%) with reported reductions in back muscle activation of 15%–54%. Conclusion The high frequency of citations of exoskeletons targeting load carrying reflects the need for devices that can support manual handling workers. Exoskeleton evaluation procedures varied across studies making comparisons difficult. The unique considerations for military applications, such as heavy external loads and load asymmetry, suggest that a significant adaptation to current technology or customized military-specific devices would be required for the introduction of exoskeletons into a military setting. Application Exoskeletons in the literature and their potential to be adapted for application to military manual handling tasks are presented.

Load Position and Weight Classification during Carrying Gait Using Wearable Inertial and Electromyographic Sensors

Lifting and carrying heavy objects is a major aspect of physically intensive jobs. Wearable sensors have previously been used to classify different ways of picking up an object, but have seen only limited use for automatic classification of load position and weight while a person is walking and carrying an object. In this proof-of-concept study, we thus used wearable inertial and electromyographic sensors for offline classification of different load positions (frontal vs. unilateral vs. bilateral side loads) and weights during gait. Ten participants performed 19 different carrying trials each while wearing the sensors, and data from these trials were used to train and evaluate classification algorithms based on supervised machine learning. The algorithms differentiated between frontal and other loads (side/none) with an accuracy of 100%, between frontal vs. unilateral side load vs. bilateral side load with an accuracy of 96.1%, and between different load asymmetry levels with accuracies of 75–79%. While the study is limited by a lack of electromyographic sensors on the arms and a limited number of load positions/weights, it shows that wearable sensors can differentiate between different load positions and weights during gait with high accuracy. In the future, such approaches could be used to control assistive devices or for long-term worker monitoring in physically demanding occupations.

Influence of age and sex on drop jump landing strategies in élite youth soccer players

The vertical drop jump (VDJ) test evaluates frontal-plane knee control in a controlled environment. Age- and sex-related changes in landing and bouncing mechanisms in youth soccer players are still under investigated. This study characterizes knee biomechanics in a large cohort of élite academy players, stratified by sex and age group. A sample of 189 young soccer players (132 male U10-U12 and U14-U17, 57 females U10-U14) from the Academy of a professional “Serie A” Italian club were tested. Motion capture technology was used to obtain sagittal and frontal plane knee angles, as well as VDJ landing asymmetry and peak vertical ground reaction forces at push-off. Landing kinetics and kinematics changed as a function of age and sex in youth élite soccer players: (i) males and females showed different landing load asymmetry between dominant and non-dominant leg, peak push-off force and knee flexion even before puberty, (ii) landing asymmetry tended to reduce in older players and (iii) knee varus increased in males after adolescence. In conclusion, besides its role in injury prevention, the VDJ can help in monitoring players’ growth and development, and this process should start at an early age. This data collection could be used as a tool for further screening test to highlight anomalous landing behaviour.

Determination of lower limbs loading during balance beam exercise

In women’s artistic gymnastics, the balance beam belongs among the disciplines with the heaviest lower limbs load. The aim of our research was to disclose a lower limbs weekly load volume regarding load asymmetry, and to determine the take-off and landing reaction forces between landing ground and foot in selected gymnastic elements. In 9 female artistic gymnasts of junior and senior category one training week was video-recorded and analysed. The reaction forces were measured using 5 Bertec force plates in one female Czech nation-al team member. Based on the training video recordings 12 jump and acrobatic elements were analysed. Among the total of 422 recorded take-offs and landings 41% were performed from both legs, (BL), 44.5% from one lower limb (HL) and 14.5% from the other lower limb (LL). The maximum reaction force of the landing ground during take-offs was 2.4 BW in av-erage, 3.1 BW in landings. In asymmetrical elements, one leg was loaded three times more (538.3 BW) than the other (174.1 BW) in one training day in total. We recommend to record the load asymmetry in the course of the gymnastic trainings in order to choose and person-alise the appropriate regeneration process and compensational exercise.

The influence of phase load asymmetry on power losses in power distribution network lines of oil and gas enterprises

The influence of phase load asymmetry on power losses in electric lines is investigated. The influence of phase load redistribution on power losses in three-phase three-conductor line with the insulated neutral is analyzed. It is demonstrated that additional power losses occur in this line which are in quadratic dependency on the relative change of phase loads. The influence of neutral conductor resistance in the four-conductor three-phase electric network on power losses in different asymmetry modes is investigated. It is shown that power losses in this network are much larger than in three-conductor network with identical phase load asymmetry and depend on the neutral conductor resistance. Significant economic effect can be obtained by increasing the cross-section of neutral conductor. At the same time, the simultaneous decrease of power losses and increase of the operational reliability of electric network are observed.

Biomechanical Assessment of the NIOSH Lifting Equation in Asymmetric Load-Handling Activities Using a Detailed Musculoskeletal Model

Objective: To assess adequacy of the National Institute for Occupational Safety and Health (NIOSH) Lifting Equation (NLE) in controlling lumbar spine loads below their recommended action limits during asymmetric load-handling activities using a detailed musculoskeletal model, that is, the AnyBody Modeling System. Background: The NIOSH committee employed simplistic biomechanical models for the calculation of the spine compressive loads with no estimates of the shear loads. It is therefore unknown whether the NLE would adequately control lumbar compression and shear loads below their recommended action limits during asymmetric load-handling activities. Method: Twenty-four static stoop lifting tasks at different load asymmetry angles, heights, and horizontal distances were performed by one normal-weight (70 kg) and one obese (93 kg) individual. For each task, the recommended weight limit computed by the NLE and body segment angles measured by a video-camera system (VICON) were prescribed in the participant-specific models developed in the AnyBody Modeling System that estimated spinal loads. Results: For both individuals, the NLE adequately controlled L5-S1 loads below their recommended action limits for all activities performed in upright postures. Both individuals, however, experienced compressive and/or shear L5-S1 loads beyond the recommended action limits when lifting was performed near the floor with large load asymmetry. Conclusion: The NLE failed to control spinal loads below the recommended limits during asymmetric lifting tasks performed near the floor. Application: The NLE should be used with caution for extreme tasks involving load handling near the floor with large load asymmetry.