Robust Force Research Articles

Multi-Scale Research on the Mechanisms of Soil Arching Development and Degradation in Granular Materials with Different Relative Density

Soil arching is significantly influenced by relative density, while its mechanisms have barely been analyzed. A series of DEM numerical simulations of the classical trapdoor test were carried out to investigate the multi-scale mechanisms of arching development and degradation in granular materials with different relative density. For analysis, the granular assembly was divided into three zones according to the particle vertical displacement normalized by the trapdoor displacement δ. The results show that before the maximum arching state (corresponding to the minimum arching ratio), contact forces between particles in a specific zone (where the vertical displacement of particles is larger than 0.1δ but less than 0.9δ) increase rapidly and robust arched force chains with large particle contact forces are generated. The variation in contact forces and force chains becomes more obvious as the sample porosity decreases. As a result, soil arching generated in a denser particle assembly is stronger, and the minimum value of the arching ratio is increased with the sample porosity. After the maximum arching state, the force chains in this zone are degenerated gradually, leading to a decrease in particle contact forces in microscale and an increase in the arching ratio in macroscale. The recovery of the arching ratio after the minimum value is also more significant in simulations with a larger relative density, as the degeneration of contact force chains is more obvious in denser samples. These results indicate the importance of contact force chain stabilities in specific zones for improving soil arching in engineering practice.

Unveiling Humility as an Influential Virtue

Humility is the quality or condition of having a modest opinion and a candid acknowledgement of one's own and others' strengths and weaknesses. A rudimentary objective of this article is to unveil humility as an influential virtue in various aspects of human interaction and societal dynamics through overviewing secondary qualitative data garnered from books, journal articles and web documents published between 1967 and 2021. Although historical perceptions hold humility as a passive or subservient trait, it emerges as a robust force capable of fostering meaningful connections, enhancing leadership effectiveness, and promoting overall well-being. The research employs a thematic analysis under a qualitative research design, drawing on insights from psychology, philosophy, and religions to unravel the subtle impact of humility on our day-to-day lives. The research findings indicate humility as a virtue that contributes to the establishment of trust, collaboration, and positive social dynamics, thereby influencing the overall structure of communities and organizations. This article is significant as it makes readers recognize the strength of humility that contributes not only to personal development but also to the cultivation of healthier, more collaborative, and more resilient societies.

Indonesia's Defense Diplomacy Strategy in Facing China's Gray Zone in the South Chine Sea

Purpose: This study aims to identify an effective strategy for Indonesia to counter China's gray zone tactics in the South China Sea. Theoretical Reference: Employing a quantitative method with a descriptive approach rooted in the positivist philosophy, this research follows the principles outlined by Sugiyono (2011). This method is chosen for investigating specific populations or samples, with a focus on quantitative/statistical data analysis to test predetermined hypotheses. Method: The research employs multiple regression analysis to assess the significance of Soft Power Diplomacy and Smart Power Diplomacy strategies as essential national resources for persuading China to undertake desired actions in addressing the challenges posed by China's Gray Zone in the South China Sea. Smart power, as defined by Jr J.N. (2007), involves integrating soft and hard power for a comprehensive strategy. According to R. Wilson (2008), smart power effectiveness lies in combining a robust military force with investments in alliances, partnerships, and cooperation. Result and Conclusion: The findings indicate that both Soft Power Diplomacy and Smart Power Diplomacy are influential tools and strategies within Indonesia's foreign policy context to effectively navigate and counteract China's Gray Zone activities in the South China Sea. Implications of Research: The identified strategies hold significant implications for shaping Indonesia's defense diplomacy against China's gray zone tactics, emphasizing the importance of integrating soft and hard power elements for a more comprehensive and efficient approach. Originality/Value: This research contributes to the field by highlighting the relevance and effectiveness of Soft Power Diplomacy and Smart Power Diplomacy as key components in Indonesia's defense diplomacy strategy, providing a nuanced understanding of countering China's Gray Zone activities in the South China Sea.

Active Compliance Smart Control Strategy of Hybrid Mechanism for Bonnet Polishing.

Compliance control strategies have been utilised for the ultraprecision polishing process for many years. Most researchers execute active compliance control strategies by employing impedance control law on a robot development platform. However, these methods are limited by the load capacity, positioning accuracy, and repeatability of polishing mechanisms. Moreover, a sophisticated actuator mounted at the end of the end-effector of robots is difficult to maintain in the polishing scenario. In contrast, a hybrid mechanism for polishing that possesses the advantages of serial and parallel mechanisms can mitigate the above problems, especially when an active compliance control strategy is employed. In this research, a high-frequency-impedance robust force control strategy is proposed. It outputs a position adjustment value directly according to a contact pressure adjustment value. An open architecture control system with customised software is developed to respond to external interrupts during the polishing procedure, implementing the active compliance control strategy on a hybrid mechanism. Through this method, the hybrid mechanism can adapt to the external environment with a given contact pressure automatically instead of relying on estimating the environment stiffness. Experimental results show that the proposed strategy adapts the unknown freeform surface without overshooting and improves the surface quality. The average surface roughness value decreases from 0.057 um to 0.027 um.

Optimization algorithm to generate a robust magnetic force of the magnetic navigation system against position error of a magnetic robot

We propose an optimization algorithm to generate a robust magnetic force against position error to achieve good controllability of the magnetic robot in the region of interest of a magnetic navigation system comprising electromagnets. We formulate an optimization problem that minimizes the norm of the spatial derivatives of the magnetic force subject to the constraints of the magnetic flux density and magnetic force. The robust magnetic force generated by the proposed algorithm was compared with conventional pseudo-inverse matrix method and verified through an experiment in which a magnetic robot was successfully steered along a bifurcated glass tube to reach a target position.

Impact force localization and reconstruction via gated temporal convolutional network

Techniques for identifying impact forces are crucial for improving the operational reliability and safety of aerospace composite structures. To address the challenges of theoretical modeling that arise from the complexity of composite structures, we propose a Gated Temporal Convolutional Network (GTCN) method. This method establishes inverse mapping relationships between structural vibration responses and impact forces. The GTCN increases the receptive field through dilated convolution, concurrently employing gating mechanisms to extract pivotal features from input signals in the vertical direction. Simulations and experiments are conducted to robustly validate the efficacy and applicability of the proposed impact force identification method. The simulation results demonstrate that the GTCN method is capable of obtaining robust impact force localization and reconstruction results, even amidst conditions of elevated noise levels. The average localization error of the GTCN is kept within 20 mm even at a noise level of 5 dB. Meanwhile, the GTCN method achieves satisfactory identification results for different types of impact forces (Gaussian, semi-cosine, and sawtooth), with an average localization accuracy above 95%. The applicability of the GTCN method to real-world structure is verified in the experiments. The average relative error of the reconstructed forces by GTCN is less than 15%. GTCN achieves stable identification of impact forces when the number of sensors is larger than 2. In both simulations and experiments, the GTCN performs better than Temporal Convolutional Network (TCN) and Convolutional Neural Network (CNN) with higher identification accuracy. The proposed method demonstrates considerable potential for application in the health monitoring of aircraft composite structures.

AI-Powered Robust Interaction Force Control of a Cardiac Ultrasound Robotic System

AI-Powered Robust Interaction Force Control of a Cardiac Ultrasound Robotic System

Atomistically informed hierarchical modeling for revisiting the constituent structures from heredity and nano-micro mechanics of sheath-core carbon fiber.

To better understand the heterogeneous anisotropic nanocomposite features and provide reliable underlying constitutive parameters of carbon fiber for continuum-level simulations, hierarchical modeling approaches combining quantum chemistry, molecular dynamics, numerical and analytical micromechanics are employed for studying the structure-performance relationships of the precursor-inherited sheath-core carbon fiber layers. A robust debonding force field is derived from energy matching protocols, including bond dissociation enthalpy calculations and rigid-constraint potential energy surface scan. Logistic long range bond stretching curves with exponential parameters and shifted force vdW curves are designed to diminish energy perturbations. The pseudo-crystalline microstructure is proposed and validated using virtual wide angle X-ray diffraction patterns and bond-orientational order parameters. The distribution or alignment features of the nanocomposite microstructures are collected from quantum chemical topology analysis and normal vector extractions. Non-equilibrium tensile loading simulation predicts the decomposed strain energy contributions, principal-axis modulus, strength limit, localized stress, and fracture morphologies of the model. Finally, an atomistically-informed stiffness prediction model combining numerical homogenization and analytical self-consistent Eshelby-Mori-Tanaka-type effective mean field micromechanics theory is proposed, giving a successful estimation of the overall stiffness matrix of the sheath-core carbon fiber system. The hierarchical models in combination with the carbonization reaction template will help in providing efficient and feasible schemes for the synergistic process-performance control of distinct types of carbon fiber.

Trailing-edge fringes enable robust aerodynamic force production and noise suppression in an owl wing model

As one of the unique owl-wing morphologies, trailing-edge (TE) fringes are believed to play a critical role in the silent flight of owls and have been widely investigated using idealized single/tandem airfoils. However, the effect of TE fringes and associated mechanisms on the aeroacoustics of owl wings, which feature curved leading edges, wavy TEs, and several feather slots at the wingtips, have not yet been addressed. In this study, we constructed two 3D owl wing models, one with and one without TE fringes, based on the geometric characteristics of a real owl wing. Large-eddy simulations and the Ffowcs Williams‒Hawkings analogy were combined to resolve the aeroacoustic characteristics of the wing models. Comparisons of the computed aerodynamic forces and far-field acoustic pressure levels demonstrate that the fringes on owl wings can robustly suppress aerodynamic noise while sustaining aerodynamic performance comparable to that of a clean wing. By visualizing the near-field flow dynamics in terms of flow and vortex structures as well as flow fluctuations, the mechanisms of TE fringes in owl wing models are revealed. First, the TE fringes on owl wings are reconfirmed to robustly suppress flow fluctuations near the TE by breaking up large TE vortices. Second, the fringes are observed to effectively suppress the shedding of wingtip vortices by mitigating the flow interaction between feathers (feather-slot interaction). These complementary mechanisms synergize to enhance the robustness and effectiveness of the TE fringe effects in owl wing models, in terms of aerodynamic force production and noise suppression. This study thus deepens our understanding of the role of TE fringes in real owl flight gliding and points to the validity and feasibility of employing owl-inspired TE fringes in practical applications of low-noise fluid machinery.

Fast and robust vision-based cable force monitoring method free from environmental disturbances

For long-term vision-based cable force monitoring, it is essential to fully consider different types of challenges, such as complex backgrounds in the field of view, illumination changes, occlusion, camera motion, and real-time realization. To address these challenges, this study proposes a vision-based, robust real-time cable force measurement method. In terms of innovation, three unique aspects were incorporated. First, to solve the difficulty of cable edge recognition caused by complex backgrounds, a linear feature detection operator called edge drawing lines was optimized by setting screening strategy based on the slope and line segments length. Second, the average of bilateral edge displacements was used as the final value to offset the displacement deviation caused by the illumination change. Third, to overcome obstacles to identifying the cable frequency caused by the camera motion, an interference frequency elimination method without reference targets or additional sensors was proposed. Furthermore, the integrated cable force calculation method was developed into a real-time measurement software. Finally, the proposed method was applied to a long-span cable-stayed bridge, where the camera was vibrated by the bridge deck or the wind significantly. The reliability of the proposed method was proved by comparing the results obtained with those achieved by accelerometers.

Public sphere or private asset? The nature of digital commons in China

ABSTRACT Since its introduction into China, the Internet is said to bring in a robust force of commons in cyberspace. Under the ideology of ‘sharing’ and ‘free flow of information’, the Internet is making good use of users' free labor and their personal data. The unique business model has become the foundation of digital commons in China. Furthermore, we could figure out the rise of the Internet in China has been following the similar ‘illegal’ model all the time, thus causing copyright infringement and other disputes accordingly. This paper traces the early ages of cyberspace in China, trying to figure out how the private-public mixed nature of the digital commons came into being and discusses relavant legal issues during the process, shedding a light on the unique relationship between mode of production tranformation and legal regime.

Fast charge transport motivated by tunable Mo2C/Mo2N high-quality heterointerface for superior pseudocapacitive storage

The development of potential transition-metal carbide/nitride heterojunctions is hindered by overall understanding and precise modulation for heterointerface effects. Herein, we demonstrate that Mo2C/Mo2N heterojunction with the precisely regulated high-quality interface can achieve marvelous rate performance and energy output via enlarging the interface-effect range and maximizing “accelerated charge” amount. The heterointerface mechanism improving properties is synergistically revealed from kinetics and thermodynamics perspectives. Kinetics analysis confirms that the self-built electric field affords a robust force to drive rapid interface electrons/ions migration. The small adsorption energy, high density of states and quite low diffusion barrier thermodynamically enhance the electrochemical reaction dynamics on heterointerface. Consequently, the almost optimal performance of ultrahigh capacitance retention (85.6% even at 10 A g−1) and pronounced energy output (96.4 Wh kg−1) in hybrid-supercapacitors than other Mo2C/Mo2N-based materials is presented. This work gives new insight into the energy storage mechanism of heterojunction and guides the design of advanced electrodes.

Edge Graphitized Oxygen-Rich Carbon Based on Stainless Steel-Assisted High-energy Ball Milling for High-Capacity and Ultrafast Sodium Storage.

Oxygen doping is an effective strategy for constructing high-performance carbon anodes in Na ion batteries; however, current oxygen-doped carbons always exhibit low doping levels and high-defect surfaces, resulting in limited capacity improvement and low initial Coulombic efficiency (ICE). Herein, a stainless steel-assisted high-energy ball milling is exploited to achieve high-level oxygen doping (19.33%) in the carbon framework. The doped oxygen atoms exist dominantly in the form of carbon-oxygen double bonds, supplying sufficient Na storage sites through an addition reaction. More importantly, it is unexpected that the random carbon layers on the surface are reconstructed into a quasi-ordered arrangement by robust mechanical force, which is low-defect and favorable for suppressing the formation of thick solid electrolyte interfaces. As such, the obtained carbon presents a large reversible capacity of 363mAhg-1 with a high ICE up to 83.1%. In addition, owing to the surface-dominated capacity contribution, an ultrafast Na storage is achieved that the capacity remains 139mAhg-1 under a large current density of 100Ag-1 . Such good Na storage performance, especially outstanding rate capability, has rarely been achieved before.

The Rising Security Challenge of East Asia's "Dual Graying": Implications for U.S.-Led Security Architecture in the Indo-Pacific

executive summary: This article explains the impact of "dual graying"—the concurrent phenomena of rapid population aging and the proliferation of gray-zone conflicts—on the security planning and postures of Northeast Asian states and considers the implications of these trends in the broader context of Indo-Pacific demographics. main argumentThe major Northeast Asian powers (China, Japan, South Korea, and Taiwan) as well as Russia are at the leading edge of one of the most consequential challenges of the 21st century: the rapid aging of their populations at a rate unprecedented in human history that is resulting in a shrinkage of their total population sizes. In addition to the graying of their populations, these powers face a range of new "gray" conflicts—interactions residing somewhere between war and peace—that exacerbate long-standing military concerns. Contrary to predictions that rapid aging will diminish the likelihood of interstate war, security tensions are rising among graying rivals in this region of the world, and states are increasing both military spending and military development. This "dual graying" underscores the need for new approaches to the U.S. network of regional security partners. policy implications• The rapid aging among regional powers does not so far suggest that an "aging peace" is likely to develop; rather, tensions are increasing over old and new areas of conflict. • The escalation of regional gray-zone conflicts is taxing U.S. allies and partners with graying and shrinking populations. Demographic changes in several of these major partners may necessitate a re-examination of roles and commitments within the U.S. alliance network. • Innovations in military and civilian technologies may eventually offset many of the challenges resulting from shrinking and rapidly aging populations, but in the meantime growing labor shortages will force many militaries to seek to adapt in other ways to maintain robust force postures. • In the wider Indo-Pacific, differential aging and population growth among major security actors suggests a growing role for several middle-power states (such as India, Indonesia, the Philippines, and Vietnam) that may benefit from a "demographic dividend" over the next several decades.

A real-time unmeasured dynamic response prediction for nuclear facility pressure pipeline system

A real-time unmeasured dynamic response prediction process for the nuclear power plant pressure pipeline is proposed and its performance is tested in the test-loop system (KAERI). The aim of the process is to predict unmeasurable or unreachable dynamic responses such as acceleration, velocity, and displacement by using a limited amount of directly measured physical responses. It is achieved by combining a well-constructed finite element model and robust inverse force identification algorithm. The pressure pipeline system is described by using the displacement-pressure vibro-acoustic formulation to consider fully filled liquid effect inside the pipeline structure. A robust multiphysics modal projection technique is employed for the real-time sensor synchronized prediction. The inverse force identification method is also derived and employed by using Bathe's time integration method to identify the full-field responses of the target system from the modal domain computation. To validate the performance of the proposed process, an experimental test is extensively performed on the nuclear power plant pressure pipeline test-loop under operation conditions. The results show that the proposed identification process could well estimate the unmeasured acceleration in both frequency and time domain faster than 32,768 samples per sec.

Mass-Manufacturable 3D Magnetic Force Sensor for Robotic Grasping and Slip Detection.

The manipulation of delicate objects remains a key challenge in the development of industrial robotic grippers. Magnetic force sensing solutions, which provide the required sense of touch, have been demonstrated in previous work. The sensors feature a magnet embedded within a deformable elastomer, which is mounted on top of a magnetometer chip. A key drawback of these sensors lies in the manufacturing process, which relies on the manual assembly of the magnet-elastomer transducer, impacting both the repeatability of measurements across sensors and the potential for a cost-effective solution through mass-manufacturing. In this paper, a magnetic force sensor solution is presented with an optimized manufacturing process that will facilitate mass production. The elastomer-magnet transducer was fabricated using injection molding, and the assembly of the transducer unit, on top of the magnetometer chip, was achieved using semiconductor manufacturing techniques. The sensor enables robust differential 3D force sensing within a compact footprint (5 mm × 4.4 mm × 4.6 mm). The measurement repeatability of these sensors was characterized over multiple samples and 300,000 loading cycles. This paper also showcases how the 3D high-speed sensing capabilities of these sensors can enable slip detection in industrial grippers.

The Perinatal Workforce Pipeline and Strategies for Meeting Community Need

Significant deficits in the national perinatal workforce are expected over the next three decades, and North Carolina is no exception. Rural communities are especially at risk of not meeting community need. Numerous strategies in Western North Carolina are being leveraged to maintain a robust, well-trained, and diverse perinatal work force.

Series Elastic Actuators-Driven Parallel Robot With Wide-Range Impedance Realization for Balance Assessment and Training

In this article, a novel robotic device is proposed that can realize a large range of compliance and a force sufficient to achieve human-balance training. The proposed device is called a virtual ground robot (VGR) and consists of a 3-degree-of-freedom parallel mechanism, which is driven by three series elastic actuators (SEAs). The proposed VGR can produce a large force and impedance overcoming the limitation of SEA using properly designed parallel legs, 3-PRRS, which can also reduce the size of the VGR. As a result, the proposed VGR can achieve 2.38-times stiffness ellipsoid as a conventional 3-RPS parallel robot. It can also achieve significantly large compliance by exploiting the advantages of SEAs, which have not been realized using conventional motion platforms. The dynamics and kinematics of the VGR are investigated from the SEA space to the entire task space, based upon which, the spatial impedance control of the VGR is designed by utilizing the robust force control of the SEA. The VGR is utilized as a device for measuring and training the balance of a human; a person can stand on the VGR, and balance-related values such as force, position, and center of the pressure are observed and controlled by the robot. The features and performance of the developed robot were theoretically examined and validated experimentally.

Building robust machine learning force fields by composite Gaussian approximation potentials

Machine learning (ML) interatomic potentials have received a lot of interest in recent years, motivated by their high accuracy at low computational costs. However, these potentials tend to overfit, which threatens their reliability. This work proposes a systematic solution to this problem, by augmenting ML potentials with simpler auxiliary potentials, which aim at ensuring that the physics behind interatomic interactions are respected. The versatility of the proposed solution is demonstrated by developing a ML force field for amorphous silicon dioxide (a-SiO2), in which a main potential is augmented with a set of simpler pairwise short-range auxiliary potentials. The resulting potential exhibits a significant improvement in transferability and scalability, at only a moderate increase in computational costs.

Full-engine simulation of micro gas turbine based on time-marching throughflow method

Gas turbines are widely used in power generation, aviation, and clean energy utilization. The accuracy of the overall performance prediction is of great importance when designing gas turbines. The purpose of this study is to develop a full-engine throughflow simulation method based on a time-marching scheme to obtain a more accurate prediction of gas turbine performance. To precisely calculate the flow deflection inside the blades, a robust inviscid blade force model was established using a theoretical derivation. The results indicate that in transonic flow, the blade force model can deteriorate the conservation of the throughflow governing equations during the time-marching process. To overcome this issue, a quasi-orthogonal body-fitted coordinate system was adopted based on theoretical analysis. Subsequently, a viscous force model coupled with a variety of empirical models was introduced to simulate the viscous effects. A simple but effective way of distributing the fuel source terms in the combustion area was employed to simulate the burning process. Finally, the developed throughflow method was applied to conduct flow simulations of the KJ66 micro gas turbine engine. The predicted overall performance matched well with the experimental data, with a maximum error of less than 6.48% among the comparisons of thrust, specific fuel consumption, and exhaust gas temperature; furthermore, the proposed method was more accurate than the traditional thermal cycle calculation. The novelty of the present study lies in the time-marching solution of the full-engine throughflow simulation and its ability to eliminate the dependence on the generic component map and obtain meridional distributions of the flow parameters. The results can offer valuable guidelines for the integrated design and optimization of components in Brayton cycles. • A strictly conservative throughflow model is developed for gas turbine simulation. • The full-engine throughflow simulation of micro gas turbine is achieved. • Throughflow model can eliminate the dependence on generic map of components. • Throughflow model can improve off-design performance prediction for gas turbine. • Throughflow model can obtain meridional details of flow parameters in gas turbine.