Interaction Forces Research Articles

Repetitive Impedance Learning-Based Physically Human-Robot Interactive Control.

Model-based impedance learning control can provide variable impedance regulation for robots through online impedance learning without interaction force sensing. However, the existing related results only guarantee the closed-loop control systems to be uniformly ultimately bounded (UUB) and require the human impedance profiles being periodic, iteration-dependent, or slowly varying. In this article, a repetitive impedance learning control approach is proposed for physical human-robot interaction (PHRI) in repetitive tasks. The proposed control is composed of a proportional-differential (PD) control term, an adaptive control term, and a repetitive impedance learning term. Differential adaptation with projection modification is designed for estimating robotic parameters uncertainties in the time domain, while fully saturated repetitive learning is proposed for estimating time-varying human impedance uncertainties in the iterative domain. Uniform convergence of tracking errors is guaranteed by the PD control and the use of projection and full saturation in the uncertainties estimation and is theoretically proved based on a Lyapunov-like analysis. In impedance profiles, the stiffness and damping are composed of an iteration-independent term and an iteration- dependent disturbance, which are estimated by repetitive learning and compressed by the PD control, respectively. Therefore, the developed approach can be applied to the PHRI where iteration-dependent disturbances exist in the stiffness and damping. The control effectiveness and advantages are validated by simulations on a parallel robot in a repetitive following task.

Research on non-linear dynamic simulation model of feeding system

Abstract The automatic gun feeding system is an important mechanism for achieving continuous shooting, but due to its complex structure, there is a lot of contact during firing, and its reliability is lower. To improve the reliability of the feeding system and its dynamic characteristics, a multi rigid body dynamic simulation model of the feeding system considering contact nonlinearity was established based on nonlinear dynamics theory. The dynamic characteristics of the feeding system were analyzed for single and continuous firing. The research results indicate that the presence of contact nonlinearity increases the interaction forces between components and also increases the uncertainty of component motion.

Fluid-structure coupling analysis in liquid-filled containers using scaled boundary finite element method

In this study, a semi-analytical model is developed to investigate the fluid-structure coupling characteristics of liquid sloshing in an elastic rectangular container subjected to horizontal external excitation based on the scaled boundary finite element method (SBFEM) for the first time. The fluid inside the container is assumed to be incompressible, inviscid and irrotational, with the hydrodynamic pressure chosen as independent nodal variable in the governing equations. The container walls are considered as cantilever beams. The coupled fluid-structure system is initially divided into the structural domain and fluid domain, after which the SBFEM is employed to obtain the governing equations for each sub-domain. In the framework of the SBFEM, only the boundary of each sub-domain, rather than the entire computational domain, needs to be meshed and discretized. This method reduces the spatial dimension of the problem by one and offers an efficient approach to model the computational domain, while allowing for analytical formulations to be derived for the internal of the domain, resulting in an accurate description of the field variables. The fundamental equation of the entire coupled fluid-structure system is then assembled by performing the equilibrium condition and compatibility condition to ensure the balance of interaction forces at the interface between container walls and the liquid. The free vibrations analysis of the fluid-structure coupling system is solved by utilizing the generalized eigenvalue problem, and the transient dynamic response is determined using the synchronous solution algorithm in conjunction with the implicit-implicit scheme of the Newmark method. To validate the excellent accuracy and stability of the proposed formulation, several numerical examples are presented to investigate the free vibration and transient dynamic characteristics for the fluid-structure coupling problem. The obtained results show good agreement with reference solutions available in the literature. Additionally, the effects of geometrical and material parameters on the system responses are examined and discussed.

Virtual Inspection System for Pumping Stations with Multimodal Feedback.

Pumping stations have undergone significant modernization and digitalization in recent decades. However, traditional virtual inspections often prioritize the visual experience and fail to effectively represent the haptic physical properties of devices during inspections, resulting in poor immersion and interactivity. This paper presents a novel virtual inspection system for pumping stations, incorporating virtual reality interaction and haptic force feedback technology to enhance immersion and realism. The system leverages a 3D model, crafted in 3Ds Max, to provide immersive visualizations. Multimodal feedback is achieved through a combination of haptic force feedback provided by a haptic device and visual information delivered by a VR headset. The system's data platform integrates with external databases using Unity3D to display relevant information. The system provides immersive 3D visualizations and realistic force feedback during simulated inspections. We compared this system to a traditional virtual inspection method that demonstrated statistically significant improvements in task completion rates and a reduction in failure rates when using the multimodal feedback approach. This innovative approach holds the potential to enhance inspection safety, efficiency, and effectiveness in the pumping station industry.

Electrode Binder Design on Silicon‐Based Anode for Next‐Generation Lithium‐Ion Batteries

AbstractAs an important part of the electrode material of lithium‐ion batteries, the binder significantly affects the forming strength of the solid electrolyte interface (SEI), and also determines the mechanical properties and cycling stability. In the silicon anode, binder have greater effect in the chemical and electrochemical stability because of the volume of the silicon anode changes by more than 300 %. Thus, the development of functional new binders with enhanced properties is one of the keys to mitigating the instability of silicon anodes. This concept first briefly introduces the advantages and disadvantages of conventional electrode binders, then the current research progress of silicon anode binders is briefly summarized based on the different types of interaction forces of binders. Finally, we conclude the properties indicators of silicon anode binders with superior performance in batteries, and comment our previous work in detail.

A new active rehabilitation training mode for upper limbs based on Tai Chi Pushing Hands

Robot-assisted rehabilitation is a crucial approach to restoring motor function in the limb. However, the current training trajectory lacks sufficient theoretical or practical support, and the monotony of single-mode training is a concern. Tai Chi Pushing Hands, a beneficial and effective daily exercise, has been shown to improve balance function, psychological state, and motor function of the upper extremities in patients recovering from stroke. To address these issues, we propose a new active rehabilitation training that incorporates Tai Chi Pushing Hands movements and yin-yang balance principles. The training trajectory and direction are encoded by the velocity field and consist of two processes: yang (push) and yin (return). During yang, the limb actively pushes the robot to move, while during yin, the limb actively follows the robot’s movement. To provide necessary assistance, an admittance controller with self-adaptive parameters is designed. In addition, we introduce two indexes, the ‘Intention Angle’ (ϖ) and the time ratio (Γ), to evaluate motion perception performance. Our experiment was conducted on a 4-degree-of-freedom upper limb rehabilitation robot platform, and the subjects were separated into a familiar group and an unfamiliar group. The experiment results show that the training could be completed well no matter whether the subject is familiar with Tai Chi Pushing Hands or not. The parameters and the movement of the robot can be adjusted based on the interactive force to adapt to the ability of the subject.

Influence of millimeter range electromagnetic waves on bovine serum albumin interaction with acridine orange

ABSTRACT The effect of non-ionizing millimeter range electromagnetic waves (MM EMW) (30–300 GHz) on the bovine serum albumin (BSA) interaction peculiarities with acridine orange (AO) has been studied in vitro. The frequencies 41.8 and 50.3 GHz were chosen, since the first one is nonresonant frequency for the water, while the second one is resonant for water. The binding constant and number of binding sites were calculated at both irradiation presence and absence. AO was revealed to bind to BSA, while after the protein irradiation the interaction force strengthens. However, it was also shown that there are differences of the interaction parameters while irradiating by 41.8 or 50.3 GHz. AO binds to BSA, irradiated by MM EMW with the frequency 41.8 GHz much more weaker, than to that, irradiated by MM EMW with the frequency 50.3 GHz.

Building Functional Liquid-Based Interfaces: From Mechanism to Application.

Functional liquid-based interfaces, with their inhomogeneous regions that emphasize the functionalized liquids, have attracted much interest as a versatile platform for a broad spectrum of applications, from chemical manufacturing to practical uses. These interfaces leverage the physicochemical characteristics of liquids, alongside dynamic behaviors induced by macroscopic wettability and microscopic molecular exchange balance, to allow for tailored properties within their functional structures. In this Minireview, we provide a foundational overview of these functional interfaces, based on the structural investigations and molecular mechanisms of interaction forces that directly modulate functionalities. Then, we discuss design strategies that have been employed in recent applications, and the crucial aspects that require focus. Finally, we highlight the current challenges in functional liquid-based interfaces and provide a perspective on future research directions.

Unprecedented hybrid lead bromides featuring trivalent aromatic cation for potential photodetection

Organic cations, as charge compensators, balance the negative charge of lead halide anions through soft interaction forces, which have a significant impact on the crystal structure and electronic structure of hybrid lead halides. However, previous studies have mainly focused on monovalent and bivalent cations, and the use of trivalent cations in the synthesis and structure-activity relationship of hybrid lead halides has rarely been explored. Herein, two organic-inorganic hybrid lead bromines with trivalent aromatic cations were successfully synthesized, namely (H3tib)2Pb3Br12·H2O (1) and (H3tib)Pb2Br7 (2) (tib = 1, 3, 5-tri(1H-imidazol-1-yl)benzene). X-ray single-crystal diffraction techniques show that the crystal structures of 1 and 2 contain previously unreported (Pb3Br12)6− two-dimensional anion layer and (Pb2Br7)3− one-dimensional anionic chain, respectively. 1 is characterized by an indirect band gap with a band gap value of 3.04 eV, while 2 is characterized by a direct band gap with a value of 3.25 eV. The photocurrent switching ratio of 1 under visible light reaches 20.0, indicating its great potential in photodetection. Through Hirshfeld surface analysis and density functional theory (DFT) calculations, the electronic and band structure characteristics of the two compounds were discussed in depth.

A many-objective evolutionary algorithm based on interaction force and hybrid optimization mechanism

In many-objective optimization, both convergence and diversity are equally important. However, in high-dimensional spaces, traditional decomposition-based many-objective evolutionary algorithms struggle to ensure population diversity. Conversely, traditional Pareto dominance-based many-objective evolutionary algorithms face challenges in ensuring population convergence. In this paper, we propose a novel many-objective evolutionary algorithm based on interaction force and hybrid optimization mechanism (MaOEAIH) for effectively addressing the difficulty in balancing convergence and diversity. First, we use the concept of interaction force to simulate the convergence (akin to gravity) and diversity (repulsion) of the population. Subsequently, we design an optimization mechanism that combines decomposition and Pareto dominance to enhance the convergence and diversity of the population separately. Simultaneously, to eliminate dominance resistance solutions, we propose a quartile method based on boundary solutions. Additionally, Random perturbations are also introduced to certain individuals within the population to facilitate their escape from local optima. MaOEAIH is compared with some state-of-the-art algorithms on 31 well-known test problems with 3-15 objectives. The experimental results show that, compared to other algorithms, MaOEAIH not only obtains solution sets of higher quality when dealing with different types of many-objective optimization problems, but also effectively addresses key challenges including insufficient selection pressure, difficulty balancing convergence and diversity, and susceptibility to population entrapment in local optima within many-objective optimization scenarios.

Effect of non-covalent binding of tannins to sodium caseinate on the stability of high-internal-phase fish oil emulsions

In this study, we designed the noncovalent binding of sodium caseinate (SC) to tannic acid (TA) to stabilize high internal phase emulsions (HIPEs) used as fish oil delivery systems. Hydrogen bonding was the dominant binding force, followed by weak hydrophobic interaction and weak van der Waals forces, as demonstrated by FTIR, fluorescence spectroscopy, and molecular docking experiments, with a binding constant of 3.25 × 106, a binding site of 1.2, and a static quenching of the binding. Increasing SC:TA from SC to 2:1 decreased the particle size from 107.37 ± 10.66 to 76.07 ± 2.77 nm and the zeta potential from −6.99 ± 2.71 to −22 ± 2.42 mV. TA increased the interfacial tension of SC, decreased the surface hydrophobicity from 1.3 × 104 to 1.6 × 103 and improved the oxidation resistance of SC. The particle size of high internal phase emulsions stabilized by complexes with different mass ratios (SC:TA from 1:0 to 2:1) increased from 4.9 ± 0.02 to 12.9 μm, the potential increased from −32.37 ± 2.7 to −35.07 ± 2.58 mV, and the instability index decreased from 0.75 to 0.02. Thicker interfacial layers could be observed by laser confocal microscopy, and an increase in the storage modulus indicated a formation of a stronger gel network. SC:TA of 1:0 showed emulsion breakage after 14 d of storage at room temperature. SC:TA of 2:1 showed the lowest degree of oil-water separation after freeze-thaw treatment. Especially, the most stable high endo-phase emulsion (at SC:TA of 2:1) prepared at each mass ratio was selected for further stability exploration. The emulsion particle size increased only from 15.63 ± 0.06 to 22.27 ± 0.35 μm at salt ion concentrations of 50–200 mM and to 249.33 ± 31.79 μm at 300 mM. The instability index and storage modulus of the high endo-phase emulsions increased gradually with increasing salt ion concentrations. At different heating temperatures (55–85 °C), the instability index of the high internal phase emulsion gradually decreased and the storage modulus gradually increased. Meanwhile, at 50 °C for 15 d of accelerated oxidation, the content of hydroperoxide decreased from 53.32 ± 0.18 to 37.48 ± 0.77 nmol/g, about 29.7 %, and the thiobarbituric acid value decreased from 1.06 × 103 to 0.8 × 103, about 24.5 %, in the high endo-phase emulsions prepared by 2:1 SC:TA compared to the fish oils, and the SC-stabilized high endo-phase only emulsion broke at the sixth day of oxidation. From the above findings, it was concluded that the high internal phase emulsion prepared with SC:TA of 2:1 can be used as a good delivery system for fish oil.

Study of adhesive wear mechanisms in asperity junctions based on phase field fracture method

Adhesive wear that is mostly induced by adhesion between asperities of rough surfaces in contact is one of the most common forms of wear of materials. However, the adhesive wear mechanisms are still not fully understood. In this work, the phase field fracture method that does not require any assumption on the crack path is used to explore the debris formation mechanism during asperity separation in adhesive wear. It is found that for ideal materials without defects the size of wear particles depends on the contact length. A small contact length leads to fracture at the junction and the formation of small wear particles. On the contrary, a large contact length will cause fracture in the bulk, resulting in large wear particles. Moreover, the angle of crack propagation decreases with increasing base angle of asperity and the ratio of the asperity height to the base edge width. The variation of fracture angle is mainly related to the ratio of asperity height to the base edge width that will influence the angle of the interaction force between asperities in the wear process. For materials with initial hole defect, the formation mechanism of wear particles will be little affected when the hole is rather small or far away from the junction. However, as the hole diameter further increases, the wear particles will change from large particles to small ones. And for materials with initial crack defect, the crack propagation always starts from the initial crack during adhesive wear. Moreover, for adhesive wear of materials with an initial crack at the bottom of asperity, fracture angle in the bulk is significantly positively correlated with the contact length and large wear particles are easy to form. However, during adhesive wear of asperity with the initial crack inside the bulk of asperity, small particles are more likely to form. This work contributes to further understanding of adhesive wear process.

Heterodyne High-Harmonic Electrostatic Force Microscopy with Improved Spatial Resolution for Nanoscale Identification of Metallic/Semiconducting Carbon Nanotubes.

There are two main types of carbon nanotubes (CNTs): metallic and semiconducting. Naturally grown CNTs are randomly distributed, posing challenges in distinguishing between the two types. Here, a novel approach for nanoscale high-resolution imaging and identification of CNTs was introduced by incorporating the heterodyne technique into high-harmonic electrostatic force microscopy (HH-EFM) on an atomic force microscopy (AFM) platform. In the developed heterodyne HH-EFM, a more localized high-order gradient of tip-sample nonlinear interaction force is used as signal channels, resulting in an improved spatial resolution, compared to the conventional HH-EFM. Furthermore, the heterodyne HH-EFM also has the capability to visualize material carrier density and assess qualitative carrier transport performance. Our work not only presents a new approach to identifying/exploring electrical properties of low-dimensional nanomaterials but also provides a solution for optimizing resolution in long-range interaction-based functional AFM technologies.

Periodic spiking pulse formation in broadband nonlinear optoelectronic oscillator.

An approach to generating periodic spiking pulses in a broadband opto-electronic oscillator (OEO) without external injection is proposed and demonstrated. Through biasing the electro-optic Mach-Zehnder modulator (MZM) in the OEO cavity at its nonlinear working point, spiking pulses are excited by the self-generated chaos under the combined action of the loop filter response time and the nonlinear excitation effect. An interaction force is introduced between pulses. As a result, the pulse number in a single roundtrip duration and the temporal distribution of the generated spiking pulses can be tuned by adjusting the loop gain and the direct-current (DC) bias voltage of the MZM. Both numerical simulation and experiment are carried out to demonstrate the spiking pulse generation mechanism, where ultra-short spiking pulse trains with even and uneven temporal distribution are generated.

Effective mechanical potential of cell-cell interaction in tissues harboring cavity and in cell sheet toward morphogenesis.

Measuring mechanical forces of cell-cell interactions is important for studying morphogenesis in multicellular organisms. We previously reported an image-based statistical method for inferring effective mechanical potentials of pairwise cell-cell interactions by fitting cell tracking data with a theoretical model. However, whether this method is applicable to tissues with non-cellular components such as cavities remains elusive. Here we evaluated the applicability of the method to cavity-harboring tissues. Using synthetic data generated by simulations, we found that the effect of expanding cavities was added to the pregiven potentials used in the simulations, resulting in the inferred effective potentials having an additional repulsive component derived from the expanding cavities. Interestingly, simulations by using the effective potentials reproduced the cavity-harboring structures. Then, we applied our method to the mouse blastocysts, and found that the inferred effective potentials can reproduce the cavity-harboring structures. Pairwise potentials with additional repulsive components were also detected in two-dimensional cell sheets, by which curved sheets including tubes and cups were simulated. We conclude that our inference method is applicable to tissues harboring cavities and cell sheets, and the resultant effective potentials are useful to simulate the morphologies.

Multifunctional corrosion inhibition of brass by interface engineering based on ternary layer-by-layer self-assembly with trivalent cerium captured

A nanoscale ternary layer-by-layer self-assembly (LbL) thin film was fabricated on brass via a simple dipping method. Dual driving force of intermolecular interactions and coordination realized the high homogeneous dispersion of Ce3+, thereby improving the controlled distribution and release of inhibitors. Compared to previous nanometer-thick conversion coatings, ternary LbL film exhibited excellent multifunctional corrosion protection. The maximum strengthening reached 496.8 % in impendence, and corrosion inhibition efficiency remained 95.0 % after a 10-day exposure in 3.5 wt% NaCl. These improvements originated from dynamic barrier effect by crosslinked gel film of PA/PAH and the surface passivation through interface deposition of Ce species.

Investigation of vibration of nanorotating plates submerged in viscous-moving fluid medium

ABSTRACT In view of the great importance of dynamical behavior prediction of nanostructures in the fluid media and their various applications in biomedical engineering, aerospace, etc. in this research, the free vibration behavior of a nano-scale rotating plate coupled with an incompressible viscous fluid is studied. To this end, nonlocal elasticity theory is adopted to apply small-scale effects. Using the Navier–Stokes relation, the interaction forces between the fluid and nanorotating plate are obtained. In order to solve the governing differential equations, the Galerkin method is utilized, and the system’s vibration frequency response has been obtained for the clamped-free-free-free boundary condition.

Comparative analysis of in vivo bio-integration of three hyaluronic acid-based fillers for 26 weeks: a histological study

ABSTRACT Stabilized hyaluronic acid (HA), produced through diverse cross-linking technology and formulated as an injectable gel, has found widespread utilization in aesthetic industry. Cross-linked HA essentially constitutes a gel particle composition formed by numerous viscoelastic particulates. Various product formulations yield HA gels with distinct properties, including particle size, viscoelasticity, and interaction forces between particles. While previous studies have primarily concentrated on the biological safety and macroscopic expression of fillers, limited research exists on the internal mechanisms governing their macro-performance. This study selected three common dermal fillers for analysis, establishing an animal model to assess their in vivo interaction with surrounding tissues and explore their internal mechanisms. The findings revealed that particle size plays a crucial role in tissue integration.

Supramolecular chemistry in cyclodextrin inclusion complexes: The formation rules of terpenes/β-cyclodextrin inclusion complexes

Supramolecular chemistry of cyclodextrins (CDs) inclusion complexes is a hot research topic at present, but current studies often focus on the host-guest interaction between CDs and hydrophobic substances, while ignoring the self-assembly behavior of the host and guest during the inclusion process. Based on the spatial structures, six representative terpenes were selected in this study, and the stoichiometric ratio between terpenes and β-cyclodextrin (β-CD) was investigated by isothermal titration calorimetry (ITC) method. Meanwhile, the constructed inclusion complexes (ICs) were characterized by nuclear magnetic resonance, X-ray diffraction, scanning electron microscope, etc. On this basis, the assembly process of β-CD and terpenes was investigated firstly by molecular simulation method, and the inclusion process between β-CD and terpenes was further studied in terms of the formation of individual ICs and ICs aggregates. Results showed that hydrophobic interaction and van der Waals force were the main driving forces of the reaction between terpenes and β-CD, and the formation of ICs, β-CD molecule aggregation, terpene aggregation, and ICs aggregation occurred simultaneously during the inclusion process of terpenes and β-CD. To sum up, this study may provide certain thinking and reference for the subsequent supramolecular chemical research on CDs.

Swelling, Protein Adsorption, and Biocompatibility of Pectin-Chitosan Hydrogels.

The study aims to determine how chitosan impacts pectin hydrogel's ability to attach peritoneal leukocytes, activate complement, induce hemolysis, and adsorb blood proteins. The hydrogels PEC-Chi0, PEC-Chi25, PEC-Chi50, and PEC-Chi75 were prepared by placing a mixture solution of 4% pectin and 4% chitosan in a ratio of 4:0, 3:1, 2:2, and 1:3 in a solution of 1.0 M CaCl2. Chitosan was found to modify the mechanical properties of pectin-calcium hydrogels, such as hardness and cohesiveness-to-adhesiveness ratio. Chitosan in the pectin-calcium hydrogel caused pH-sensitive swelling in Hanks' solution. The PEC-Chi75 hydrogel was shown to adsorb serum proteins at pH 7.4 to a greater extent than other hydrogels. PEC-Chi75's strong adsorption capacity was related to lower peritoneal leukocyte adherence to its surface when compared to other hydrogels, showing improved biocompatibility. Using the optical tweezers approach, it was shown that the force of interaction between pectin-chitosan hydrogels and plasma proteins increased from 10 to 24 pN with increasing chitosan content from 0 to 75%. Thus, the properties of pectin-calcium hydrogel, which determine interactions with body tissues after implantation, are improved by the addition of chitosan, making pectin-chitosan hydrogel a promising candidate for smart biomaterial development.