Range Of Forces Research Articles

Connections between Upper Tropospheric and Lower Stratospheric Circulation Responses to Increased CO2

Abstract There are myriad ways atmospheric circulation responds to increased CO2. In the troposphere, the region of the tropical upwelling narrows, the Hadley cells expand, and the upper-level subtropical zonal winds that comprise the subtropical jet strengthen. In the stratosphere, the tropical upwelling narrows and strengthens, enhancing the Brewer–Dobson circulation. Despite the robustness of these projections, dynamical coupling between the features remains unclear. In this study, we analyze output from the NASA Goddard Institute for Space Studies (GISS) ModelE coupled climate model to examine any connection between the upper tropospheric and lower stratospheric circulation by considering the features’ seasonality, hemispheric asymmetry, scaling, and transient response to a broad range of CO2 forcings. We find that a narrowing and strengthening of upper tropospheric upwelling occurs with a strengthening of the subtropical jet. There is also a narrowing and strengthening of lower stratospheric upwelling that is related to an equatorward shift in critical latitude for wave breaking and the associated strengthening of the subtropical lower stratosphere’s zonal winds. However, the stratospheric responses display different seasonal, hemispheric, and transient patterns than those in the troposphere, indicating independent circulation changes between the two domains.

Micromechanical Loading Studies in Ex Vivo Cultured Embryonic Rat Bones Enabled by a Newly Developed Portable Loading Device.

Mechanical loading has been described as having the potential to affect bone growth. In order to experimentally study the potential clinical applications of mechanical loading as a novel treatment to locally modulate bone growth, there is a need to develop a portable mechanical loading device enabling studies in small bones. Existing devices are bulky and challenging to transfer within and between laboratories and animal facilities, and they do not offer user-friendly mechanical testing across both ex vivo cultured small bones and in vivo animal models. To address this, we developed a portable loading device comprised of a linear actuator fixed within a stainless-steel frame equipped with suitable structures and interfaces. The actuator, along with the supplied control system, can achieve high-precision force control within the desired force and frequency range, allowing various load application scenarios. To validate the functionality of this new device, proof-of-concept studies were performed in ex vivo cultured rat bones of varying sizes. First, very small fetal metatarsal bones were microdissected and exposed to 0.4 N loading applied at 0.77Hz for 30s. When bone lengths were measured after 5days in culture, loaded bones had grown less than unloaded controls (p < 0.05). Next, fetal rat femur bones were periodically exposed to 0.4 N loading at 0.77Hz while being cultured ex vivo for 12days. Interestingly, this loading regimen had the opposite effect on bone growth, i.e., loaded femur bones grew significantly more than unloaded controls (p < 0.001). These findings suggest that complex relationships between longitudinal bone growth and mechanical loading can be determined using this device. We conclude that our new portable mechanical loading device allows experimental studies in small bones of varying sizes, which may facilitate further preclinical studies exploring the potential clinical applications of mechanical loading.

Stacked rigid and compliant dielectric structures for increasing force range in soft capacitive sensors

Stacked rigid and compliant dielectric structures for increasing force range in soft capacitive sensors

The impact of task context on predicting finger movements in a brain-machine interface.

A key factor in the clinical translation of brain-machine interfaces (BMIs) for restoring hand motor function will be their robustness to changes in a task. With functional electrical stimulation (FES) for example, the patient's own hand will be used to produce a wide range of forces in otherwise similar movements. To investigate the impact of task changes on BMI performance, we trained two rhesus macaques to control a virtual hand with their physical hand while we added springs to each finger group (index or middle-ring-small) or altered their wrist posture. Using simultaneously recorded intracortical neural activity, finger positions, and electromyography, we found that decoders trained in one context did not generalize well to other contexts, leading to significant increases in prediction error, especially for muscle activations. However, with respect to online BMI control of the virtual hand, changing either the decoder training task context or the hand's physical context during online control had little effect on online performance. We explain this dichotomy by showing that the structure of neural population activity remained similar in new contexts, which could allow for fast adjustment online. Additionally, we found that neural activity shifted trajectories proportional to the required muscle activation in new contexts. This shift in neural activity possibly explains biases to off-context kinematic predictions and suggests a feature that could help predict different magnitude muscle activations while producing similar kinematics.

Experiments and simulations of the drawing envelope of commercially pure aluminum

The range of blank-holding force (BHF) for which deep drawing of AA1100-H24 is successful is investigated using a combination of experiments and simulations. The experiments involve circular blanks of three different diameters: 35 mm, 37 mm and 40 mm. The thickness of the blanks is 0.51 mm. These are drawn with a punch of 20 mm diameter, i.e., at drawing ratios of 1.75, 1.85 and 2.0, respectively, using a custom, modular forming apparatus where the BHF can be controlled at will, between 0 and 2,400 N. The experiments are performed in an Instron 8872 servo-hydraulic frame that allows precise measurements of the punch force and displacement. The working envelopes are determined experimentally in the space of BHF and draw depth, which can be categorized into three regimes: wrinkling, safe and tearing. It is found that grey zones exist between the three regimes. These experiments are then simulated in Abaqus/Standard, using two types of elements: axisymmetric and shell. In the latter case, plastic anisotropy is introduced, using the Yld2000-2D anisotropic yield function. Wrinkling and tearing failure are triggered by inducing suitable geometric imperfections. It is shown that the models are able to reproduce the experiments well. This serves as a verification of the modelling framework, which can then be used for the simulations of more complex forming processes.

Analytical modeling and performance evaluation of an adjustable permanent magnet linear eddy current brake with mechanical magnetic adjuster

A novel mechanical flux-adjusting permanent magnet linear eddy current brake with high performance and its nonlinear analytical model are proposed. The innovative point lies in attaching an additional mechanical magnetic adjuster directly above the interior permanent magnet bar, which can achieve flexible adjustment of the air-gap flux and improve the generation capacity of the braking force and its regulation range. Considering the importance of the analytic model in practical design, the average air-gap flux density and eddy current density are estimated based on the equivalent magnetic circuit method and Ampere’s law, where the critical flux-weakening effect and leakage flux effect are calculated quantitatively. Then a practical theoretical model of braking force is derived based on the energy conversion and verified by the 3D finite-element method. Through analysis of the magnitude and regulation range of the braking force in a given range of speed, the advantages of the device and the electromagnetic force model are proved separately. Moreover, design suggestions for selecting the key geometrical parameters are further given, which offer useful information for pre-design and optimization.

A Shallow-water Model Exploration of Atmospheric Circulation on Sub-Neptunes: Effects of Radiative Forcing and Rotation Period

Sub-Neptune-type exoplanets are abundant in our Galaxy yet have no solar system analogs. They exist in a broad range of stellar forcing and rotational regimes that are distinctly different from solar system planets and more commonly studied hot Jupiters. Here we present simulations that explore global atmospheric circulation of sub-Neptunes generated with a two-dimensional shallow-water model, SWAMPE. We explore the circulation regimes of synchronously rotating sub-Neptunes with a focus on the interaction of planetary rotation rate and radiative timescale in a variety of stellar insolations. In highly irradiated, short-timescale regimes, our models exhibit high day–night geopotential contrasts. As the timescales become longer, the geopotential contrasts and longitudinal variability decrease, while temporal variability increases. The transition from day-to-night flow to jet-dominated flow is primarily driven by the radiative timescale. Strong- and medium-forcing regimes exhibit transitions between day-to-night flow and jet-dominated flow at similar points in the parameter space. The weak-forcing regime differs owing to comparatively stronger rotational effects. Planetary rotation period dominates in determining equator-to-pole geopotential contrast. Our simulations exhibit higher time variability when either radiative timescale or rotation period is long.

Black dots: High-yield traction force microscopy reveals structural factors contributing to platelet forces.

Measuring the traction forces produced by cells provides insight into their behavior and physiological function. Here, we developed a technique (dubbed 'black dots') that microcontact prints a fluorescent micropattern onto a flexible substrate to measure cellular traction forces without constraining cell shape or needing to detach the cells. To demonstrate our technique, we assessed human platelets, which can generate a large range of forces within a population. We find platelets that exert more force have more spread area, are more circular, and have more uniformly distributed F-actin filaments. As a result of the high yield of data obtainable by this technique, we were able to evaluate multivariate mixed effects models with interaction terms and conduct a clustering analysis to identify clusters within our data. These statistical techniques demonstrated a complex relationship between spread area, circularity, F-actin dispersion, and platelet force, including cooperative effects that significantly associate with platelet traction forces. STATEMENT OF SIGNIFICANCE: Cells produce contractile forces during division, migration, or wound healing. Measuring cellular forces provides insight into their health, behavior, and function. We developed a technique that calculates cellular forces by seeding cells onto a pattern and quantifying how much each cell displaces the pattern. This technique is capable of measuring hundreds of cells without needing to detach them. Using this technique to evaluate human platelets, we find that platelets exerting more force tend to have more spread area, are more circular in shape, and have more uniformly distributed cytoskeletal filaments. Due to our high yield of data, we were able to apply statistical techniques that revealed combinatorial effects between these factors.

Research on obstacle avoidance motion planning method of manipulator in complex multi scene

In order to improve the efficiency and success rate of obstacle avoidance motion planning of industrial manipulator in complex multi scenes, a collision detection model between manipulator and obstacles based on cylinder and sphere bounding box is established, and an improved RRT* algorithm based on heuristic probability fusion artificial potential field method(P-artificial potential field RRT*, PAPF-RRT*) is proposed. The probability target bias and random sampling point optimization strategy are introduced into the sampling, and the location optimization constraints are applied to the sampling points to enhance the sampling guidance and quality. In order to change the expansion direction of the traditional new node and the local optimization problem in special environment, the target gravity, obstacle repulsion and adaptive step size of the artificial potential field method are combined, so that the algorithm can guide the expansion direction and step size of the new node in real time within the resultant force range generated by APF, reducing excessive exploration and the expansion of the collision region. The Cubic B-spline is used to interpolate and optimize the planned path to reduce the complexity of the path and improve the flexibility of the path. The simulation results in two-dimensional and three-dimensional multi scenes show that the present algorithm reduces the average path search time by 31.22% and shortens the path length by 17.32% comparing with the traditional RRT* algorithm. The visual simulation results show that the present algorithm can make the manipulator successfully avoid obstacles and run to the target point quickly and smoothly.

Technical, ergonomic and cognitive learning methodology in transumbilical single-port laparoscopic hysterectomy.

We introduced learning curves on a detailed step protocol and ergonomic aspect to determine key surgical points in transumbilical single-port laparoscopic hysterectomy (TSPLH) and to popularize both technical and cognitive methodology on laparoendoscopic single-site surgery (LESS). A retrospective analysis of 87 TSPLH procedures was conducted by a single surgeon in three learning stages. Technical, ergonomic, and cognitive steps were introduced, and surgical outcomes were analyzed. Key production points in TSPLH include developing a clear retroperitoneal space, maintaining appropriate strength and direction with a vaginal manipulator, coagulating the uterine artery, and applying an improved vaginal stump suturing method. Technical factors included instrument domination, hand-eye coordination, and alternating hand functions. Ergonomic techniques focused on shoulder, elbow, arm, wrist, and finger movements, range of motion, muscle power, continuous forces, and flexibility. Improved cognitive factors such as confidence, decision-making, and communication were also observed. The study aimed to form methodological education on TSPLH and LESS and benefit more surgeons. The detailed production and key ergonomic points will help guide self-learning and education.

A Novel Force-Sensing Smart Textile: Inserting Silicone-Embedded FBG Sensors into a Knitted Undergarment.

A number of textile-based fiber optic sensors have recently been proposed for the continuous monitoring of vital signs. However, some of these sensors are likely unsuitable for conducting direct measurements on the torso as they lack elasticity and are inconvenient. This project provides a novel method for creating a force-sensing smart textile by inlaying four silicone-embedded fiber Bragg grating sensors into a knitted undergarment. The applied force was determined within 3 N after transferring the Bragg wavelength. The results show that the sensors embedded in the silicone membranes achieved enhanced sensitivity to force, as well as flexibility and softness. Additionally, by assessing the degree of FBG response to a range of standardized forces, the linearity (R2) between the shift in the Bragg wavelength and force was found to be above 0.95, with an ICC of 0.97, when tested on a soft surface. Furthermore, the real-time data acquisition could facilitate the adjustment and monitoring of force during the fitting processes, such as in bracing treatment for adolescent idiopathic scoliosis patients. Nevertheless, the optimal bracing pressure has not yet been standardized. This proposed method could help orthotists to adjust the tightness of brace straps and the location of padding in a more scientific and straightforward way. The output of this project could be further extended to determine ideal bracing pressure levels.

Dynamics of Air Flow in Partially Water‐Saturated Porous Media

AbstractDynamics of flowing air in partially water‐saturated, porous geological formations are governed by a wide range of forces and parameters. These dynamics are reviewed in the contexts of flow patterns that arise and the corresponding applicability of diverse modeling approaches. The importance of reliable gas‐liquid flow models draws from the key role gases play in earth systems, and the various engineering practices involving air injection into geological formations. Here, we focus on air flow in water‐wet porous media. We survey the factors that affect flow patterns and phase configurations, and the measures that quantify them. For single‐phase flow in saturated media (i.e., air flow in dry media or water flow in water‐saturated media), the continuum approach (Darcy's law) is generally applicable and offers a good interpretive tool. However, the coupled two‐phase flow continuum approach appears appropriate only for phase‐saturation degrees that allow both phases to be continuous in the flow domain. Furthermore, air flow in wet media is highly unstable. As a result, air commonly flows in preferential pathways or in the form of bubbles and ganglia, which are not amenable to continuum modeling. On the other hand, pore‐scale models that account for the complex geometries and interfaces between the fluids and the media require extreme computational efforts, and generally inaccessible details on medium characteristics. Other stochastically‐based representations, such as percolation theory, have value in the conceptualization of complex flow problems but demonstrate limited success in interpreting phase configurations, saturation degrees, and relative permeabilities.

Insights into the Morphology and Surface Properties of Microalgae at the Nanoscale by Atomic Force Microscopy (AFM): A Review

Atomic force microscopy (AFM) is a method that provides the nanometer-resolution three-dimensional imaging of living cells in their native state in their natural physiological environment. In addition, AFM’s sensitivity to measure interaction forces in the piconewton range enables researchers to probe surface properties, such as elasticity, viscoelasticity, hydrophobicity and adhesion. Despite the growing number of applications of AFM as a method to study biological systems, AFM is not yet an established technique for studying microalgae. Following a brief introduction to the basic principles and operation modes of AFM, this review highlights the major contributions of AFM in the field of microalgae research. A pioneering AFM study on microalgae was performed on diatoms, revealing the fine structural details of diatom frustule, without the need for sample modification. While, to date, diatoms are the most studied class of microalgae using AFM, it has also been used to study microalgae belonging to other classes. Besides using AFM for the morphological characterization of microalgae at the single cell level, AFM has also been used to study the surface properties of microalgal cells, with cell elasticity being most frequently studied one. Here, we also present our preliminary results on the viscoelastic properties of microalgae cell (Dunaliella tertiolecta), as the first microrheological study of microalgae. Overall, the studies presented show that AFM, with its multiparametric characterization, alone or in combination with other complementary techniques, can address many outstanding questions in the field of microalgae.

Surface Textured Double Layer Triboelectric Nanogenerator for Autonomous and Ultra‐Sensitive Biomedical Sensing

AbstractTriboelectric nanogenerators (TENGs) have demonstrated great promise especially for the realization of self‐powered biomedical sensors. Nevertheless, developing TENG sensors able to detect the broad range of biomechanical movements experienced on the human body is still a challenge. Herein, a unique ridge‐structured device sensitive to wide range of forces is reported (i.e., low‐forced pulse monitoring to high‐forced gait monitoring). The device is composed of thermoplastic polyurethane layer sandwiched between two textured silicon elastomeric layers. Compared to non‐textured surface configurations, the proposed ridged‐structure provides an increased frictional contact area between the triboelectric materials, while also acting as a spacer between the triboelectric materials. The influence of ridge dimensions on the output performance is investigated by mechanical simulations and electromechanical experimental tests. The optimized device shows a maximum peak output power and current densities of 490 mW m−2 and 1750 µA m−2, respectively at 30 N and 7 Hz of compressive forces. The proposed device exhibits stable electrical output for 10000 cycles. As a proof of concept, the proposed device is used as wearable sensors for monitoring pulse rate, breath patterns, and gait movements. The study suggests the possibility of utilization of novel‐structured sandwich‐type elastomer ridge‐based TENG in different aspects of biomedical sensing and smart wearable application.

Quantification of van der Waals forces in bimodal and trimodal AFM.

The multifrequency formalism is generalized and exploited to quantify attractive forces, i.e., van der Waals interactions, with small amplitudes or gentle forces in bimodal and trimodal atomic force microscopy (AFM). The multifrequency force spectroscopy formalism with higher modes, including trimodal AFM, can outperform bimodal AFM for material property quantification. Bimodal AFM with the second mode is valid when the drive amplitude of the first mode is approximately an order of magnitude larger than that of the second mode. The error increases in the second mode but decreases in the third mode with a decreasing drive amplitude ratio. Externally driving with higher modes provides a means to extract information from higher force derivatives while enhancing the range of parameter space where the multifrequency formalism holds. Thus, the present approach is compatible with robustly quantifying weak long range forces while extending the number of channels available for high resolution.

An Axial Force Sensor Based on a Long-Period Fiber Grating with Dual-Peak Resonance

A high-sensitivity axial force sensor with a large measurement range based on a dual-peak long-period fiber grating (LPFG) is proposed and experimentally demonstrated. Previously, the relationship between the grating period and the dual-peak wavelengths has been investigated based on the coupled-mode theory. In our experiment, the LPFG was fabricated in our laboratory by illuminating the fiber core with the aid of a 213 nm UV laser. The sensitivity of the proposed axial force sensor can reach −14.047 nm/N in the force range from 0.490 N to 4.508 N. Taking the advantages of a compact size, low cost, and large measurement range, our force sensor has more applicable abilities in harsh environments.

Optimization of a dynamic absorber with nonlinear stiffness and damping for the vibration control of a floating offshore wind turbine toy model

Passive vibration mitigation of offshore wind turbines using nonlinear absorbers or nonlinear energy sinks has started to receive attention in the literature. In most cases, little attention has been paid to the possibility of detached resonances that occur when the nonlinear energy sink is attached to the linear system describing the wind turbine. Sea motions that alter the initial conditions of the floating offshore wind turbine may cause the nonlinear energy sink to operate at one or more detached resonances, completely negating its ability to control turbine vibration. In this paper, we are interested in optimizing the parameters of a nonlinear energy sink with nonlinear stiffness and nonlinear viscous damping for vibration control of a toy model (e.g., a linear mass-spring-damper system) of a floating offshore wind turbine over its entire operating range. The mechanism of cancellation of the detached resonance is studied analytically under 1:1 resonance. It is shown that the nonlinear energy sink with properly tuned nonlinear viscous damping allows the complete elimination of undesired regimes and completely restores the absorber's ability to strongly limit the vibration of a floating offshore wind turbine over its entire forcing range. The results obtained over a wide range of parameters suggest that both the optimal nonlinear energy sink parameters (linear and nonlinear stiffness and nonlinear damping) and the damping of floating offshore wind turbine vibration depend on simple power laws of nonlinear energy sink mass and linear damping.

Greater task difficulty during unilateral motor tasks changes intracortical inhibition and facilitation in the ipsilateral primary motor cortex in young men

This study aimed to clarify the changes in short-interval intracortical inhibition (SICI) and facilitation (ICF) in the ipsilateral primary motor cortex (iM1) when the task difficulty during unilateral force-matching tasks was manipulated. Twelve young male adults matched their left index finger abduction force to a displayed target force. Task difficulty was manipulated by varying the acceptable force range of the mean target force (5% MVC). Briefly, unilateral force-matching tasks with lesser and greater task difficulty (EASY and DIFF, respectively) were assigned acceptable force ranges of ± 7% and ± 0% of the target force, respectively. To evaluate SICI and ICF in iM1, paired-pulse transcranial magnetic stimulation with 2-ms and 10-ms interstimulus intervals was applied to correct motor-evoked potentials (MEPs) from the first dorsal interosseous muscle during each task. Test stimulus intensity to evoke the MEP with a peak-to-peak amplitude of approximately 0.5–1.5 mV for each task was lower in DIFF than in EASY (P = 0.001), indicating that DIFF increased corticospinal excitability of the ipsilateral hemisphere compared with EASY. The MEPs in SICI and ICF were significantly larger in DIFF than in EASY (P < 0.050). These results suggest that greater corticospinal excitability in the ipsilateral hemisphere during DIFF is associated with reduced SICI and increased ICF.

Reviewing the 3C’s of blended learning for police education: assessing capacity, building capability, and conquering challenges

ABSTRACT Police education and training, in common with education at all levels, was seriously affected by the onset of lockdown during the COVID-19 pandemic. Police organisations in England and Wales sought to cope by moving training and education programmes online, almost overnight. This paper presents findings from interviews conducted with Learning and Development leaders in 17 police forces in England and Wales to gauge the capacity of organizations to provide blended learning (BL) in the pre COVID period and plans for the future. Findings indicated that although there are challenges, the appetite and capacity to adopt BL methods in forces range on a spectrum. The paper and makes recommendations to support the rollout and use of BL in police education generally and proposes a theory of change to assist the introduction of BL in police organisations.

A Tool to Enable Intraoperative Insertion Force Measurements for Cochlear Implant Surgery.

Residual hearing preservation during cochlear implant (CI) surgery is closely linked to the magnitude of intracochlear forces acting during the insertion process. So far, these forces have only been measured in vitro. Therefore, the range of insertion forces and the magnitude of damage-inducing thresholds in the human cochlea in vivo remain unknown. We aimed to develop a method to intraoperatively measure insertion forces without negatively affecting the established surgical workflow. Initial experiments showed that this requires the compensation of orientation-dependent gravitational forces. We devised design requirements for a force-sensing manual insertion tool. Experienced CI surgeons evaluated the proposed design for surgical safety and handling quality. Measured forces from automated and manual insertions into an artificial cochlea model were evaluated against data from a static external force sensor representing the gold standard. The finalized manual insertion tool uses an embedded force sensor and inertial measurement unit to measure insertion forces. The evaluation of the proposed design shows the feasibility of orientation-independent insertion force measurements. Recorded forces correspond well to externally recorded reference forces after reliable removal of gravitational disturbances. CI surgeons successfully used the tool to insert electrode arrays into human cadaver cochleae. The presented positive evaluation poses the first step towards intraoperative use of the proposed tool. Further in vitro experiments with human specimens will ensure reliable in vivo measurements. Intraoperative insertion force measurements enabled by this tool will provide insights on the relationship between forces and hearing outcomes in cochlear implant surgery.