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The mechanical and acoustic emission characteristics of rock-like materials under non-uniform loads were investigated by means of a self-developed mining-induced stress testing system and acoustic emission monitoring system. In the experiments, the specimens were divided into three regions and different initial vertical stresses and stress loading rates were used to simulate different mining conditions. The mechanical and acoustic emission characteristics between regions were compared, and the effects of different initial vertical stresses and different stress loading rates were analysed. The results showed that the mechanical properties and acoustic emission characteristics of rock-like materials can be notably localized. When the initial vertical stress and stress loading rate are fixed, the peak strength of region B is approximately two times that of region A, and the maximum acoustic emission hit value of region A is approximately 1–2 times that of region B. The effects of the initial vertical stress and stress loading rate on the peck strain, maximum hit value, and occurrence time of the maximum hit are similar in that when either of the former increase, the latter all decrease. However, peck strength will increase with the increase in loading rate and decrease with the increase in initial vertical stress. The acoustic emission hits can be used to analyse the damage in rock material, but the number of acoustic emission hits cannot be used alone to determine the degree of rock damage directly.

The transport of cargo particles that are pulled by several molecular motors in a cooperative manner is studied theoretically in this article. The transport properties depend primarily on the maximal number N of motor molecules that may pull simultaneously on the cargo particle. Because each motor must unbind from the filament after a finite number of steps but can also rebind to it again, the actual number of pulling motors is not constant but varies with time between zero and N. An increase in the maximal number N leads to a strong increase of the average walking distance (or run length) of the cargo particle. If the cargo is pulled by up to N kinesin motors, for example, the walking distance is estimated to be$5^{N-1}/N$micrometers, which implies that seven or eight kinesin molecules are sufficient to attain an average walking distance in the centimeter range. If the cargo particle is pulled against an external load force, this force is shared between the motors, which provides a nontrivial motor-motor coupling and a generic mechanism for nonlinear force-velocity relationships. With increasing load force, the probability distribution of the instantaneous velocity is shifted toward smaller values, becomes broader, and develops several peaks. Our theory is consistent with available experimental data and makes quantitative predictions that are accessible to systematic in vitro experiments.

Still little is known about how spinopelvic alignment affects spinal load distribution. Musculoskeletal modeling can potentially help to discover associations between spine alignment and risk factors of spinal disorders (e.g. disc herniation, vertebral fracture, spondylolisthesis, low back pain). The present study exploited the AnyBody full-body musculoskeletal model to assess the relation between lumbar loads and spinopelvic alignment in the sagittal plane. The model was evaluated in the standing position. The simulated postures were set using spinopelvic parameters gleaned from the literature and characterizing the healthy adult population. The parameters were: sagittal vertical axis, Roussouly lumbar type, sacral slope, and pelvic incidence. A total of 2772 configurations were simulated based on the following measurements: compression force and anterior shear at levels L4L5 and L5S1; multifidus, longissimus spinae, and rectus abdominis muscle forces. Changes in global sagittal alignment, lumbar typology, and sacral inclination, but not in pelvic incidence, were found to affect intervertebral loads in the lumbar spine and spinal muscle activation. Considering these changes would be advantageous for clinical evaluation, due to the recognized relation between altered loads and risk of disc herniation, vertebral fracture, spondylolisthesis, and low back pain. Musculoskeletal modeling proved to be a valuable biomechanical tool to non-invasively investigate the relation between internal loads and anatomical parameters.

The load distribution among lumbar spinal structures—still an unanswered question—has been in the focus of this hybrid experimental and simulation study. First, the overall passive resistive torque-angle characteristics of healthy subjects’ lumbar spines during flexion–extension cycles in the sagittal plane were determined experimentally by use of a custom-made trunk-bending machine. Second, a forward dynamic computer model of the human body that incorporates a detailed lumbar spine was used to (1) simulate the human–machine interaction in accordance with the experiments and (2) validate the modeled properties of the load-bearing structures. Third, the computer model was used to predict the load distribution in the experimental situation among the implemented lumbar spine structures: muscle–tendon units, ligaments, intervertebral discs, and facet joints. Nine female and 10 male volunteers were investigated. Lumbar kinematics were measured with a marker-based infrared device. The lumbar flexion resistance was measured by the trunk-bending machine through strain gauges on the axes of the machine’s torque motors. Any lumbar muscle activity was excluded by simultaneous sEMG monitoring. A mathematical model was used to describe the nonlinear flexion characteristics. The subsequent extension branch of a flexion–extension torque–angle characteristic could be significantly distinguished from its flexion branch by the zero-torque lordosis angle shifted to lower values. A side finding was that the model values of ligament and passive muscle stiffnesses, extracted from well-established literature sources, had to be distinctly reduced in order to approach our measured overall lumbar stiffness values. Even after such parameter adjustment, the computer model still predicts too stiff lumbar spines in most cases in comparison with experimental data. A review of literature data reveals a deficient documentation of anatomical and mechanical parameters of spinal ligaments. For instance, rest lengths of ligaments—a very sensitive parameter for simulations—and cross-sectional areas turned out to be documented at best incompletely. Yet by now, our model well reproduces the literature data of measured pressure values within the lumbar disc at level L4/5. Stretch of the lumbar dorsal (passive) muscle and ligament structures as an inescapable response to flexion can fully explain the pressure values in the lumbar disc. Any further external forces like gravity, or any muscle activities, further increase the compressive load on a vertebral disc. The impact of daily or sportive movements on the loads of the spinal structures other than the disc cannot be predicted ad hoc, because, for example, the load distribution itself crucially determines the structures’ current lever arms. In summary, compressive loads on the vertebral discs are not the major determinants, and very likely also not the key indicators, of the load scenario in the lumbar spine. All other structures should be considered at least equally relevant in the future. Likewise, load indicators other than disc compression are advisable to turn attention to. Further, lumbar flexion is a self-contained factor of lumbar load. It may be worthwhile, to take more consciously care of trunk flexion during daily activities, for instance, regarding long-term effects like lasting repetitive flexions or sedentary postures.

Distributed multi-controller deployment is a promising method to achieve a scalable and reliable control plane of Software-Defined Networking (SDN). However, it brings a new challenge for balancing loads on the distributed controllers as the network traffic dynamically changes. The unbalanced load distribution on the controllers will increase response delay for processing flows and reduce the controllers’ throughput. Switch migration is an effective approach to solve the problem. However, existing schemes focus only on the load balancing performance but ignore migration efficiency, which may result in high migration costs and unnecessary control overheads. This paper proposes Efficiency-Aware Switch Migration (EASM) to balance the controllers’ loads and improve migration efficiency. We introduce load difference matrix and trigger factor to measure load balancing on controllers. We also introduce the migration efficiency problem, which considers load balancing rate and migration cost simultaneously to optimally migrate switches. We propose EASM to efficiently solve to the problem. The simulation results show that EASM outperforms baseline schemes by reducing the controller response time by about 21.9%, improving the controller throughput by 30.4% on average, maintaining good load balancing rate, low migration costs and migration time, when the network scale changes.

Background Motor imagery (MI) induced EEG patterns are widely used as control signals for brain-computer interfaces (BCIs). Kinetic and kinematic factors have been proved to be able to change EEG patterns during motor execution and motor imagery. However, to our knowledge, there is still no literature reporting an effective online MI-BCI using kinetic factor regulated EEG oscillations. This study proposed a novel MI-BCI paradigm in which users can online output multiple commands by imagining clenching their right hand with different force loads. Methods Eleven subjects participated in this study. During the experiment, they were asked to imagine clenching their right hands with two different force loads (30% maximum voluntary contraction (MVC) and 10% MVC). Multi-Common spatial patterns (Multi-CSPs) and support vector machines (SVMs) were used to build the classifier for recognizing three commands corresponding to high load MI, low load MI and relaxed status respectively. EMG were monitored to avoid voluntary muscle activities during the BCI operation. The event-related spectral perturbation (ERSP) method was used to analyse EEG variation during multiple load MI tasks. Results All subjects were able to drive BCI systems using motor imagery of different force loads in online experiments. We achieved an average online accuracy of 70.9%, with the highest accuracy of 83.3%, which was much higher than the chance level (33%). The event-related desynchronization (ERD) phenomenon during high load tasks was significantly higher than it was during low load tasks both in terms of intensity at electrode positions C3 ( p  < 0.05) and spatial distribution. Conclusions This paper demonstrated the feasibility of the proposed MI-BCI paradigm based on multi-force loads on the same limb through online studies. This paradigm could not only enlarge the command set of MI-BCI, but also provide a promising approach to rehabilitate patients with motor disabilities.

Wave-induced forces pose significant challenges to marine structures, especially pile groups, where cap structures and pile spacings play critical roles in load distribution and structural stability. A physical wave flume experiment was conducted to investigate the influences of cap structures and pile spacings on wave load distributions under different wave conditions. Spatial and temporal variations in wave load distributions, including temporal variations in horizontal force, were measured as wave pressure rather than force. The results demonstrate that cap structures significantly alter the distributions of wave loads on pile groups. The integration of the cap increases the horizontal forces on the front pile and slightly reduces the vertical pressures across the pile group, particularly on the rear pile at relatively low elevations. The cap also delays the peak moment of horizontal force, especially in shallow water depths, where impact loads are more prominent and the cap induces water splash-back. Additionally, reducing pile spacing mitigates interference effects, optimizing the load distribution across piles by modulating flow velocity and pressure. The vertical pressure distribution exhibits a tiered pattern, with lower sections experiencing consistent loading, middle sections being subjected to higher loads at larger spacings, and upper sections being more affected by the cap at smaller spacings. As wave velocity and water depth increase, the differences in pressure intensity between pile groups with and without cap structures decrease, indicating the stabilizing effect of wave characteristics on structural response. This study provides insights into the design of marine pile group structures to optimize their performance characteristics under dynamic wave loading conditions.

An efficient prediction of the extreme value of traffic loads is crucial for the structural design, reliability evaluation, maintenance planning, and further life-cycle cost analysis of bridges. In this work, a novel method is proposed for predicting the appropriate extreme traffic load distribution. Specifically, the average conditional exceedance rate (ACER) statistical model is estimated from the historical traffic loads which was collected through a weigh-in-motion system installed in toll stations. The basic idea of the ACER approach lies in the introduction of a cascade of conditioning approximations and the average exceedance rate to capture the dependence effects and obtain the data tail, the trend features of which are fitted with a similar Gumbel distribution function and extrapolated to the concerned level. An illustration case dealing with traffic loads using the ACER strategy is presented, the extreme value and confidence interval (CI) in any return period can be predicted by application of this approach. Furthermore, the peaks-over-threshold (POT) method based on the asymptotic extreme theory is also applied to illustrate the advantages of the ACER method. The ACER method has advantages in analyzing extreme traffic loads, with good robustness and the ability to handle extreme value prediction for different sampling strategies, it also can produce more accurate confidence intervals and predicts consistent extreme values. The study results are expected to help accurately determine traffic loads and ensure safety in bridge engineering.

The ground load acting on a tunnel is an important issue in tunnel design, especially when the tunnel passes through highly weathered sandstone. A systematic field-monitoring campaign was performed to investigate the ground loads on a tunnel structure, the behavior of the composite support system, and the deformation of the tunnel boundaries. The monitoring results were analyzed and compared with those of various theories, such as the whole-soil column theory and those of Terzaghi, Bierbaumer, Xie Jiaxiu, and Protodyakonov. The ground load on a highway tunnel in highly weathered sandstone does not conform to current theoretical methodologies. It was confirmed that Terzaghi’s theory is suitable for estimating the peak magnitude of the vertical ground load, but differs from the field-monitoring results for ground load distribution profile. To facilitate tunnel design, a potential profile for ground loads is proposed, in which the vertical load component is ‘mountain’-shaped and the horizontal component adopts a ‘folded-line’ pattern. The roof rockbolts are subjected to compression and should be replaced by pipe grouting that is capable of providing enhanced reinforcement and accelerating the construction schedule. The bending moments acting on the lining were found to form a ‘butterfly’ shape. Supplementary finite-element modeling was undertaken to explore the mechanical behavior of the tunnel lining. These results indicated that steel rebar needs to be pre-installed in both the intrados of the lining roof and extrados of the spandrels to improve the lining tensile strength.

Pitch bearings of wind turbines are large, grease-lubricated rolling bearings that connect the rotor blades with the rotor hub. Rolling bearings are the standard bearing type for this application. Most blade bearings are four-point bearings with one or two rows. Three-row roller bearings with two axial rows and one radial row have higher costs, but are an increasingly used alternative. Both rotor blade and rotor hub have a varying stiffness along the circumference of the bearing rings. This results in rotationally non-symmetric load sharing (load distributions) of the bearing rollers. The load distribution depends on the pitch angle, the load magnitude and the load angle. In this paper, we evaluate the load sharing of such a three-row bearing for a reference wind turbine of the 3 MW-class, taking account of the stiffness of the interface parts hub and rotor blade. A set of finite-element simulations with varying loads, load angles and pitch angles has been executed to determine the influence of the named parameters on the loads of the individual rollers. Curve fits of these discrete load points allow the determination of roller loads for any given parameter combination. One application of the results is the determination of the overall bearing load which is a key input for fatigue lifetime calculations.