Energy Dissipation Mechanisms Research Articles

Emergence of nanoscale viscoelasticity from single cancer cells to established tumors

Tumors are complex materials whose physical properties dictate growth and treatment outcomes. Recent evidence suggests time-dependent physical properties, such as viscoelasticity, are crucial, distinct mechanical regulators of cancer progression and malignancy, yet the genesis and consequences of tumor viscoelasticity are poorly understood. Here, using Wide-bandwidth AFM-based ViscoElastic Spectroscopy (WAVES) coupled with mathematical modeling, we probe the origins of tumor viscoelasticity. From single carcinoma cells to increasingly sized carcinoma spheroids to established tumors, we describe a stepwise evolution of dynamic mechanical properties that create a nanorheological signature of established tumors: increased stiffness, decreased rate-dependent stiffening, and reduced energy dissipation. We dissect this evolution of viscoelasticity by scale, and show established tumors use fluid-solid interactions as the dominant mechanism of mechanical energy dissipation as opposed to fluid-independent intrinsic viscoelasticity. Additionally, we demonstrate the energy dissipation mechanism in spheroids and established tumors is negatively correlated with the cellular density, and this relationship strongly depends on an intact actin cytoskeleton. These findings define an emergent and targetable signature of the physical tumor microenvironment, with potential for deeper understanding of tumor pathophysiology and treatment strategies.

A pseudo-Double-Network Hydrogel Built upon Layered Double Hydroxides with Self-Strengthening Properties.

While great achievements have been made in the development of mechanically robust nanocomposite hydrogels, incorporating multiple interactions on the bases of two demensional inorganic cross-linkers to construct self-strengthening hydrogels has rarely been investigated. To this end, we propose here a new method for the coupling the dynamic covalent bonds and non-covalent interactions within a pseudo double-network system. The pseudo first network, formed through the Schiff Base reation between Tris-modified layered double hydroxides (Tris-LDHs) and oxidized dextran (ODex), is linked to the second network built upon non-covalent interactions between Tris-LDHs and poly(acrylamide-co-2-acrylamido-2-methyl-propanesulfonate) (p-(AM-co-AMPS). The swelling and mechanical properties of the resulting hydrogels have been investigated as a function of the ODex and AMPS contents. The as-prepared hydrogel can swell to 420 times of its original size and retain more than 99.9 wt.% of water. Mechanical tests show that the hydrogel can bear 90 % of compression and is able to be stretched to near 30 times of its original length. Cyclic tensile tests reveal that the hydrogels are capable of self-strengthening after mechanical training. The unique energy dissipation mechanism based on the dynamic covalent and non-covalent interactions is considered to be responsible for the outstanding swelling and mechanical performances.

Energy Dissipation in Tribological Stressed Greases

Lubricating greases that are subject to a continuous friction process are in a non-equilibrium state. In processes far from equilibrium, there is a possibility that dissipative structures will form. In this work, the conjecture is pursued that this is also possible in loaded grease films. On the one hand, the shear process is considered in interaction with structural degradation, and on the other hand, the behavior of energy dissipation mechanisms is investigated. In the two models presented, it is shown that there are conditions under which it is possible to trigger self-organization processes. The next step must be the development of suitable experiments.

Highly stretchable polymer semiconductor thin films with multi-modal energy dissipation and high relative stretchability

Stretchable polymer semiconductors (PSCs) have seen great advancements alongside the development of soft electronics. But it remains a challenge to simultaneously achieve high charge carrier mobility and stretchability. Herein, we report the finding that stretchable PSC thin films (<100-nm-thick) with high stretchability tend to exhibit multi-modal energy dissipation mechanisms and have a large relative stretchability (rS) defined by the ratio of the entropic energy dissipation to the enthalpic energy dissipation under strain. They effectively recovered the original molecular ordering, as well as electrical performance, after strain was released. The highest rS value with a model polymer (P4) exhibited an average charge carrier mobility of 0.2 cm2V−1s−1 under 100% biaxial strain, while PSCs with low rS values showed irreversible morphology changes and rapid degradation of electrical performance under strain. These results suggest rS can be used as a parameter to compare the reliability and reversibility of stretchable PSC thin films.

Numerical and Experimental Investigations of Particle Dampers Attached to a Pipeline System

The structure of pipeline systems is complex, and the working environment is harsh. Under the excitation of the engine equipment foundation and pump fluid, it is easy to generate excessive vibration, which seriously affects the safe operation of the equipment. Particle damping achieves structural vibration suppression through the principle of particle collision dissipation. Due to the drawbacks of traditional pipeline vibration reduction methods, this article introduces a particle damping technology for pipeline system vibration suppression and designs particle dampers based on the structural characteristics of pipelines. We analyzed the energy dissipation mechanism of particle damping, revealed the influence of the materials, structure, external excitation, and other parameters of the pipeline particle dampers on the energy dissipation characteristics of the particle damping, established a pipeline vibration reduction test system with particle damping, and verified its effectiveness in pipeline system vibration reduction. This study can provide a technical reference for vibration reduction in pipeline systems.

Evaluation of the Thermal Performance of Two Passive Facade System Solutions for Sustainable Development

Sustainable development is essential for the future of the planet. Using passive elements, like ventilated facades based on insulation and air chambers, or living walls, which are solutions based on nature, is a powerful strategy for cities to improve their thermal environment, reduce energy consumption, and mitigate the effects of climate change. This approach allows for the quantification of the influence of passive surfaces on energy fluxes compared to bare surfaces. In addition, it delves into understanding how the incorporation of vegetation on building facades alters surface energy fluxes, involving a combination of physical and biochemical processes. This comprehensive investigation seeks to harness the potential of passive and natural solutions to address the pressing challenges of urban sustainability and climate resilience. This research uses a surface energy balance model to analyze the thermal performance of two facades using experimental data from a PASLINK test cell. This study uses the grey box RC model, which links continuous-time ordinary differential equations with discrete measurement data points. This model provides insight into the complex interplay among factors that influence the thermal behavior of building facades, with the goal of comprehensively understanding how ventilated and green facades affect the dynamics of energy flow compared to conventional facades. The initial thermal resistance of the bare facade was 0.75 (°C m2)/W. The introduction of a ventilated facade significantly increased this thermal resistance to 2.47 (°C m2)/W due to the insulating capacity of the air chamber and its insulating layer (1.70 (°C m2)/W). Regarding the modular living wall, it obtained a thermal resistance value of 1.22 (°C m2)/W (this vegetated facade does not have an insulating layer). In this context, the modular living wall proved to be effective in reducing convective energy by 68% compared with the non-green facade. It is crucial to highlight that evapotranspiration was the primary mechanism for energy dissipation in the green facade. The experiments conclusively show that both the modular living wall and open-ventilated facade significantly reduce solar heat loads compared with non-passive bare wall facades, demonstrating their effectiveness in enhancing thermal performance and minimizing heat absorption.

Seismic behavior of precast columns with unbonded prestressed tendons and energy-dissipating bars: physical and numerical investigations

The study of the strength and failure modes of construction components has become increasingly important with the advent of industrialized construction. Recently, because of the need to promote the survivability of both structures and persons, it has encompassed failure modes associated with seismic threats. This study reports the seismic behavior of precast segmented columns designed with both unbonded prestressed tendons (UPTs) and energy-dissipating (ED) bars. A physical specimen was subjected to a quasi-static cyclic test; this permitted the evaluation of the damage mode and behavior of the energy dissipation mechanism, and permitted the establishment and verification of a fiber beam element simulation model. The model was then used to evaluate the effects of the variation of the design parameters on the behavior of precast assembled columns. The test specimen exhibited stable energy dissipation and a pinching effect during cyclic loading. An analysis using the fiber beam element model with varying design parameters revealed that high-strength concrete could mitigate the concrete damage and residual deformation after an earthquake, and that the concrete strength and steel bar strength should be matched when enhancing the seismic resilience of precast columns with high-strength steel bars. It was determined that increasing the prestress mechanism, namely the ratio of the UPTs, could greatly improve the residual deformation, while the ratio of ED bars is the key factor in enhancing the energy dissipation capacity of the precast columns. Suitable ratios of UPTs and ED bars are the keys to ensuring stable energy dissipation and low residual drifts. Moreover, an increased axial load ratio and prestress level are able to restrain the joint opening and improve the bearing capacity of the precast columns; however, an excessive axial load or prestressing force would result in the rapid degeneration of the carrying capacity and larger residual displacements.

Study on the Influence of Sample Size on the Mechanical and Integrity Characteristics of Coal Measure Sandstone under High Strain Rate

In order to explore the size effect of the mechanical and damage characteristics of coal measure sand stones under dynamic load, uniaxial impact compression tests were carried out on coal-bearing sand stones with a diameter of 50 mm and a length–diameter ratio of L/R = 0.5, 0.8, 1, 1.2, 1.5, 1.8, and 2 by using the Hopkinson pressure bar test system. The size effect law of the mechanical properties and energy dissipation of coal-bearing sandstone under a high strain rate were investigated. Then, the mercury injection test was carried out on the fragments at different positions, and the electron microscope scanning test was carried out on the fragments near the end of the transmission rod. Based on the area damage definition method and normalization treatment, the integrity model of coal measure sandstone, considering the influence of the length–diameter ratio, was established. The results showed that the peak strength and dynamic elastic modulus of coal measure sandstone increased first and then decreased with the increase in length–diameter ratio under impact compression load, and they reached the maximum when the length–diameter ratio was 1.2. The dynamic peak strain increased gradually with the increase in length–diameter ratio. The energy of coal-bearing sandstone showed strong size effect, that is, the total absorbed energy, elastic energy, and dissipated energy increased with the increase in length–diameter ratio, and the size effect of total absorbed energy was the most obvious. Under the same impact pressure, the porosity of coal-bearing sand stones with seven kinds of length–diameter ratios near the incident end was roughly the same. But when the length–diameter ratio was greater than 0.5, the porosity decreased gradually with the increase in the distance from the incident end. And the larger the length–diameter ratio, the more obvious the decreasing trend. When the length–diameter ratio was smaller, the size of the holes and cracks and the cluster density were larger. The integrity model of coal measure sandstone, considering the influence of the length–diameter ratio, showed that the larger the length–diameter ratio, the better the relative integrity of coal-bearing sandstone.

Chaotic discrete breathers in bcc lattice

It is well known that a modulationally unstable short-wavelength delocalized nonlinear vibrational mode (DNVM) can create chaotic discrete breathers (DBs) in a nonlinear lattice. A necessary condition for this is that the DNVM must have a frequency outside the phonon spectrum of the lattice. This phenomenon has been repeatedly analyzed for one- and two-dimensional lattices, and here it is studied for a bcc lattice with β-Fermi–Pasta–Ulam–Tsingou potential. Using the group-theoretical approach developed by Chechin and Sakhnenko, four DNVMs are found with a wave vector at the boundary of the first Brillouin zone and frequencies above the phonon spectrum. It is shown that the development of the modulational instability of all four DNVMs with amplitudes above a certain value leads to the formation of chaotic DBs, which is justified by calculating the energy localization parameter and the maximum particle energy. Chaotic DBs in the three-dimensional bcc lattice radiate their energy faster than in previously studied two-dimensional lattices. The results obtained describe one of the possible mechanisms of energy dissipation by a crystal lattice in a far-from-equilibrium system.

Finite element analysis and hysteretic model of self-centering steel connection with dual energy dissipation mechanism

In the traditional steel beam-column connection, the beam flanges were welded to the column face, while the beam web was bolted to the column face by shear tab. During seismic events, this connection often suffers from brittle failure. This paper presents a novel self-centering steel connection with dual energy dissipation mechanism. The connection utilizes the sliding of friction elements and the plastic deformation of T-stub at different stages to dissipate energy. As a result, the proposed connection not only enhances energy dissipation capacity but also increases the safety redundancy of the structure. The main focus of this study is to investigate the structural behavior of this new type of connection by refined finite element analysis models. These models are constructed using ANSYS and validated against experimental results. Furthermore, parametric analysis is conducted to investigate the influence of various factors on the seismic performance of the connection. These factors include the initial post-tensioning force of prestressed steel strands, the shape form of T-stub flange, the flange thickness of T-stub, the coefficient of friction between friction plates and web of T-stub, and the pre-tension force of high-strength bolts. The results demonstrate that increasing the initial post-tensioning force of the steel strands reduces the residual deformation and enhances the self-centering ability of the connection, and the dual energy dissipation behavior is more obvious. Meanwhile, the occurrence of both sliding and plastic deformation of T-stub is postponed. The influence of the thickness of the T-stub flange is minimal during the friction-based energy dissipation stage but significant during the energy dissipation stage of the plastic deformation of T-stub. Moreover, increasing either the coefficient of friction between friction plates and T-stub webs or the initial post-tensioning force of high-strength bolts significantly improves the bending strength of the connection and reduces residual deformation. Meanwhile, these factors mostly affect the friction sliding stage to delay the starting point of sliding, but their influence on the plastic deformation is minimal. Finally, a theoretical hysteretic model is proposed based on the dual energy dissipation mechanism. The model is compared and analyzed against experimental results, demonstrating good agreement. This provides theoretical foundation for the design of similar structural connection.

Enhancing energy dissipation properties of damping styrene-butadiene-styrene copolymer materials by hydrogen bonding

Mimicking the unique structure of biological tissue and energy dissipation mechanism of biology, various damping materials have been fabricated to provide impact protection. Utilizing the viscoelasticity of polymers around glass transition temperature, polymer materials generally are used as damping materials. However, it is still a great challenge to tailor the energy dissipation capacity and working temperature of damping materials. Here, we report an approach to adjust the energy-dissipation performance of polystyrene-polybutadiene-polystyrene (SBS) triblock polymer materials by incorporating distinct hydrogen-bonding moieties on the side groups of polybutadiene soft segment. The hydrogen bonding moieties reinforce the interaction between polymer chains and significantly improved the energy-dissipation capacity of SBS elastomers. Especially, when carbamate moieties are incorporated on the soft segment of SBS and SBS-U-2 is afforded. The hydrogen bonds deriving from carbamate moieties significantly increase the viscoelasticity of SBS-U-2 and provide excellent energy dissipation capacity. The current work provides a facile approach to fabricate damping materials based on engineering polymeric materials.

Analytical fracture toughness model for multiphase epoxy matrices modified by thermoplastic and carbon nanotube/thermoplastic

The introduction of a toughener is considered one of the most effective approaches to address the brittleness of epoxy resins. This paper introduces an analytical model for investigating the Mode-I fracture toughness of modified epoxy resins by including a phase-separating thermoplastic (TP) polymer, polyetherimide (PEI), and the combination of PEI and carbon nanotubes (CNTs). The fracture energy contributions from different toughening mechanisms, identified by the fractographical studies of the modified epoxy resins, were calculated, in which the energy contribution from TP deformation was obtained by molecular dynamics model simulation. The developed fracture toughness model showed satisfactory agreement with the experimental data. In the TP/epoxy binary system, the increase in TP content from 5 to 20 wt% resulted in a rise in the contribution of TP deformation (crack bridging) leading to a commensurate increase in fracture toughness from 33% to 70%. This transformation established TP deformation as the dominant mechanism for crack energy dissipation. In the CNT/TP/epoxy ternary system, from the model, the observed synergy in toughness was attributed to the improved dispersion of nanotubes. The developed analytical model may be used to formulate multiphase toughened resin matrices for optimal fracture toughness.

Unraveling the Fate of Impacted Ice Particles and the Consequences for Plume Fly‐Through Missions

AbstractPlanetary exploration mission concepts that include flying directly through material for collection and/or analysis are becoming increasingly common, with Enceladus water ice particles offering a particularly high‐value target. Despite this interest, understanding and predicting what happens to ice samples upon impacting a surface at the high‐ and hyper‐velocities expected for these missions remains a critical knowledge gap. We describe a set of custom simulations using the Hot Optimal Transportation Meshfree method that was implemented to better understand ice impacts. We then compare the simulations with relevant experimental results from the Aerosol Impact Spectrometer. These simulations and experiments illustrate the complex relationship between different energy dissipation mechanisms and how they affect the fate of the particle. These results highlight the importance of understanding the implications of this complex physics on successful sample collection and transfer in order to achieve the scientific goals of the mission.

Stability analysis of energy dissipation mechanisms in rocks surrounding circular opening

This study analyzes the stability of surrounding rock for a circular opening based on the energy and cavity expansion theory, and regards the surrounding rock failure of circular opening as an unstable state driven by energy. Firstly, based on the large-strain cylindrical cavity contraction and energy dissipation method, the deformation caused by the excavation of surrounding rock is regarded as the cylindrical cavity contraction process. By introducing the energy dissipation mechanism, the energy dissipation solution of cylindrical cavity contraction is obtained. The energy dissipation process of surrounding rock is characterized by the strain energy changes in the elastic and elasto-plastic regions of this cavity contraction analysis. Secondly, the deformation control effect of support and surrounding rock parameters on the energy dissipation of surrounding rock is studied based on the energy dissipation solution of surrounding rock under support conditions. Finally, the effectiveness and reliability of the analytical approach was demonstrated by comparing the support design results with those in the literature. The research results indicate that the three-dimensional mechanical properties and dilatancy angle of rock and soil mass have a significant impact on the energy support design of surrounding rock. This study provides a general analysis method for the stability analysis of surrounding rock of deep buried tunnels and roadway.

Unlocking the Power of Multicatalytic Synergistic Transformation: toward Environmentally Adaptable Organohydrogel.

A sustainable and efficient multicatalytic chemical transformation approach is devised for the development of all-biobased environmentally adaptable polymers and gels with multifunctional properties. The catalytic system, utilizing Lignin aluminum nanoparticles (AlNPs)-aluminum ions (Al3+ ), synergistically combines multiple catalytic cycles to create robust, mechanically stable, and versatile organohydrogels. Single catalytic cycles alone fail to achieve desired results, highlighting the importance of cooperatively combining different cycles for successful outcomes. The transformation involves free radical crosslinking, reversible quinone-catechol reactions, and an autocatalytic mechanism, resulting in a dual crosslinking strategy that incorporates both covalent and ionic crosslinking. This approach creates a dynamic gel system with combined energy dissipation and storage mechanisms. The engineered organohydrogels demonstrate vital multifunctionalities such as good thermal stability, self-healing, and adhesive properties, flame-retardancy, mechanical resilience and durability, conductivity, viscoelastic properties, environmental adaptability, and resistance to extreme conditions such as freezing and drying. The developed catalytic technology and resulting gels hold significant potential for applications in flexible electronics, energy storage, actuators, and sensors.

Impact response and energy absorption of metallic buffer with entangled wire mesh damper

An innovative metallic buffer consisting of series-connected hat-shaped entangled wire mesh damper (EWMD) and parallel springs are proposed in this work to enhance the reliability of engineering equipment. The impact response and the energy dissipation mechanism of hat-shaped EWMD under different quasi-static compression deformations (2–7 mm) and impact heights (100–200 mm) are investigated using experimental and numerical methods. The results demonstrate distinct stages in the quasi-static mechanical characteristics of hat-shaped EWMD, including stiffness softening, negative stiffness, and stiffness hardening. The loss factor gradually increases with increasing compression deformation before entering the stiffness hardening stage. Under impact loads, the hat-shaped EWMD exhibits optimal impact energy absorption when it enters the negative stiffness stage (150 mm), resulting in the best impact isolation effect of metallic buffer. However, the impact energy absorption significantly decreases when hat-shaped EWMD enters the stiffness hardening stage. Interestingly, quasi-static compression analysis after experiencing different impact loads reveals the disappearance of the negative stiffness phenomenon. Moreover, with increasing impact loads, the stiffness hardening point progressively shifts to an earlier stage.

The Key Role of Cyclic Electron Flow in the Recovery of Photosynthesis in the Photobiont during Rehydration of the Lichen Cladonia stellaris

Lichens are poikilohydric organisms and an important part of the ecosystem. They show high desiccation tolerance, but the mechanism of dehydration resistance still needs to be studied. The photosynthesis recovery of the photobiont in rehydrated lichen Cladonia stellaris after 11-year desiccation was investigated by simultaneously monitoring both photosystem I and II (PSI and PSII) activities. The responses of the photochemical efficiency and relative electron transport rate (rETR) of PSI and PSII, and the quantum yield of the cyclic electron flow (CEF) were measured using a Dual-PAM-100 system. PSI recovered rapidly, but PSII hardly recovered in C. stellaris during rehydration. The maximal photochemical efficiency of PSII (Fv/Fm) was generally very low and reached about just 0.4 during the rehydration. These results indicated that PSII had restored little and was largely inactivated during rehydration. The quantum yield of PSI recovered quickly to almost 0.9 within 4 h and remained constant at nearly 1 thereafter. The results showed that the activation of the CEF in the early stages of rehydration helped the rapid recovery of PSI. The quantum yield of the CEF made up a considerable fraction of the quantum yield of PSI during rehydration. A regulated excess energy dissipation mechanism and non-photochemical quenching (NPQ) also recovered. However, the small extent of the recovery of the NPQ was not enough to dissipate the excess energy during rehydration, which may be responsible for the weak activity of PSII during rehydration. The results indicated that both CEF and NPQ were essential during the rehydration of the photobiont in C. stellaris. The methods used in the measurements of chlorophyll a fluorescence and P700+ absorbance changes in this study provided a speedy and simple way to detect the physiological characteristics of the photobionts of lichen during rehydration. This work improves our understanding of the mechanism behind lichen’s desiccation tolerance.

Vibration energy transfer in a forced oscillation fluidized bed

Fluidized bed technology plays a vital role in petroleum, chemical, and coal separation. To improve fluidization stability, airflow is periodically introduced to form a pulsed gas–solid fluidized bed. The vibrating airflow drives the particles with vibration energy transfer and dissipation in the pulsed fluidized bed. The fluidization quality will be greatly improved when the pulsation frequency is equal to the natural frequency. The understanding of the mechanism governing vibration energy transfer and dissipation enables further adjustment of parameters to effectively control the fluidized bed, thereby optimizing its operational state. In this work, the response mechanism of the fluidized bed to resonance effect is described, and its vibration energy transfer and dissipation mechanism is investigated. Furthermore, an evaluation index for energy dissipation rate is proposed. Additionally, based on the theory of spring oscillators, an enhanced natural frequency model for bubble-free fluidized beds is established in this study, incorporating particle properties and bed height as key factors. The predicted error is effectively controlled within 15%, demonstrating excellent agreement with existing literature and research findings.

Research on the Mechanical Model and Hysteresis Performance of a New Mild Steel-Rotational Friction Hybrid Self-Centering Damper.

A mild steel-friction self-centering damper with a hybrid energy-dissipation mechanism (MS-SCFD) was proposed, which consisted of a mild steel, frictional, dual-energy-dissipation system and a disc spring resetting system. The structure and principle of the MS-SCFD were explained in detail while the restoring force model was established. The hysteretic behavior of the MS-SCFD under low-cycle reciprocating loading was modeled. Then, the influence of parameters such as the disc spring preload, the friction coefficient, and the soft-steel thickness on the mechanical properties of the MS-SCFD was investigated. The results indicate that the simulation results are basically consistent with the theoretical prediction results, with a maximum error of only 9.46% for the key points of bearing capacity. Since the MS-SCFD is provided with a hysteretic curve in the typical flag type, it will obtain the capacity of excellent self-centering performance. It can effectively enhance the stiffness, bearing capacity, and self-centering capability of the damper after the pre-pressure of the disc spring is increased. The energy-dissipation capacity of the MS-SCFD increases with the increase in the friction coefficient. However, it also increases the residual deformation of the MS-SCFD. The energy dissipation of the MS-SCFD is particularly sensitive to the thickness of mild steel. After being loaded, all components of the MS-SCFD are not damaged except for the plastic deformation caused by the yielding of the mild steel. The normal function of the MS-SCFD can be restored simply by replacing the mild steel plates after the earthquake. Therefore, it can significantly enhance the economy and applicability of the damper.

Investigation on Kinetics and Mechanism of Energy Dissipation by Ultrasound-Assisted Leaching of Low-Nickel Matte

Investigation on Kinetics and Mechanism of Energy Dissipation by Ultrasound-Assisted Leaching of Low-Nickel Matte