Dissipation Mechanism Research Articles

Chemical damping of the motion of a piston: irreversibilities arising from nonequilibrium conditions on the chemical potential

Abstract We revisit the thermodynamic analysis of an isothermal ideal gas mixture enclosed within a cylinder and separated from the surrounding atmosphere by a movable and frictionless piston. When equilibrium conditions based on the chemical potentials of one or more species in the mixture are not satisfied at all times, which occurs for example for a chemical reaction with finite and non-zero reaction rates in the forward and reverse directions and for mass transfer of one species across a permeable membrane occurring at a finite and non-zero rate, an irreversibility is necessarily introduced into the system with a resulting increase in the entropy of the Universe. Consequently, when the piston is set in motion, it cannot oscillate indefinitely. The piston must again come to rest despite there not being any mechanical dissipative mechanisms, i.e., friction or viscous dissipation, nor a thermal dissipative mechanism, i.e., irreversible heat transfer, operating within the system. Only when the system is reversible, such that the entropy of the Universe remains constant at all times, will the piston oscillate indefinitely. “Chemical damping”, or an irreversibility arising from nonequilibrium conditions on the chemical potential, provides another dissipative mechanism that has not yet been analyzed before.

Turbulent energy budget analysis based on coherent wind lidar observations

Abstract. The turbulent kinetic energy (TKE) budget terms, which collectively are a key physical quantity for describing the generation and dissipation processes of turbulence, are crucial for revealing the essence and characteristics of turbulence. Due to limitations in current observational methods, the generation and dissipation mechanisms of atmospheric turbulent energy are mainly based on ground or tower-based observations, and studies on the budget terms of TKE of vertical structures are lacking. We propose a new method for detecting TKE budget terms based on coherent wind lidar and compare it with data obtained with a three-dimensional ultrasonic anemometer. The results indicate that the error in the buoyancy generation term estimated by the wind lidar is relatively small, less than 0.00014 m2 s−3, which verifies the accuracy and reliability of our method. We explore the generation and dissipation mechanisms of turbulence under different weather conditions, and find that the buoyancy generation term plays a role in dissipating TKE under low-cloud and light-rain conditions. During the day, turbulent transport and the dissipation rate are the main dissipation terms, while buoyancy generation is the main dissipation term at night. The results show that the proposed method can accurately capture the vertical distribution of TKE, the dissipation rate, shear generation, turbulent transport, and buoyancy generation terms in the boundary layer and can comprehensively reflect the influence of each budget term on the vertical structure of turbulent energy. This research provides a new perspective and method for studies of atmospheric turbulence, which can be further applied to fine observations of the vertical structure and dynamics of turbulence.

Thermal effects on the resistive superconducting transition in step-edge YBCO squid arrays

Abstract The effect of thermal fluctuations in Yttrium Barium Copper Oxide (YBCO) SQUID filters (SQIFs), containing arrays of 258, 2304, and 4080 SQUIDs, were investigated using the electrical resistivity and applied magnetic field up to 9 tesla. Our study reveals that the SQIFs experience a two-step superconductor transition. The transition at lower temperature is only present in the SQIF samples, not in the control sample without the SQFIs, and it is investigated here in terms of two primary dissipation mechanisms. The first dominates near the transition temperature and has the characteristics of thermally activated phase slippage (TAPS). At lower temperatures, the dominant characteristics are those of thermally-activated magnetic flux flow (TAFF). The mechanisms producing such behaviors contribute significantly to dissipation effects, resulting in an additional DC voltage that overlays the Josephson current, regardless of the quantity of SQUIDs in the SQIFs. These dissipation effects can have significant implications for technologies utilizing high-temperature superconductor SQIFs unless the operating temperature is lowered significantly below the superconducting transition temperature.

Application of Surface-Cracking Process to Improve Impact Toughness of High-Strength BCC Steel at Low Temperatures

At very low temperatures, typically ductile materials, especially body-centered cubic (BCC) steels, often exhibit an abrupt transition to brittle fracture, significantly limiting their applicability in cryogenic and low-temperature environments. This challenge arises from the inherent properties of BCC steels, where ductility is drastically reduced, leading to unexpected failures under mechanical stress. Despite the advantages of high-strength BCC steels, including cost-effectiveness and mechanical robustness, their susceptibility to brittle fracture restricts their use in demanding low-temperature applications. To address this limitation, we developed an innovative surface-cracking process to enhance the impact toughness of BCC steels. The introduction of controlled surface cracks redistributes stress and energy dissipation mechanisms, improving the toughness of high-strength BCC steels at cryogenic temperatures. Microscopic observations and finite element analyses reveal that these surface cracks not only dissipate crack formation energy but also alter stress triaxiality at crack tips. This causes the stress state to transition toward a plane stress condition, effectively mitigating stress concentrations typically observed in plane strain states. By reducing localized stress severity and promoting uniform energy distribution, the surface cracks encourage failure mechanisms favoring ductile behavior over brittle fracture.

Synergistic enhancement of the dynamic impact damage resistance and energy absorption of ultra‐high molecular weight polyethylene fiber reinforced composites with multiple plasma modification

AbstractThe study reveals the dynamic impact damage resistance and energy absorption of oxygen/argon/nitrogen multiple plasma modified ultra‐high molecular weight polyethylene (UHMWPE) fiber reinforced composites. The interface bonding properties and impact resistance of the composite were studied by microsphere debonding test, low‐velocity and high‐velocity impact test. The modified parameters are optimized based on quadratic polynomial equation. The impact resistance of the composite was evaluated from the aspects of ballistic limit velocity, failure mode and energy dissipation mechanism. The results showed that compared with untreated composites, the depth of dents and damage area of multiple plasma modified composites were reduced by 43.53% and 11.73%, respectively. The energy absorption and limit velocity of high‐velocity impact were increased by 14.64% and 25.58%, respectively. The modified composites formed an energy dissipation mechanism dominated by fiber breakage. The impact damage resistance and energy absorption of UHMWPE fiber reinforced composites were enhanced with multiple plasma modification.Highlights Multiple plasma modification enhance synergistic energy absorption of composites. The optimum treatment parameters of composites plasma modification were analyzed. Interface bonding properties were evaluated from microscopic perspective.

On time-splitting methods for gradient flows with two dissipation mechanisms

We consider generalized gradient systems in Banach spaces whose evolutions are generated by the interplay between an energy functional and a dissipation potential. We focus on the case in which the dual dissipation potential is given by a sum of two functionals and show that solutions of the associated gradient-flow evolution equation with combined dissipation can be constructed by a split-step method, i.e. by solving alternately the gradient systems featuring only one of the dissipation potentials and concatenating the corresponding trajectories. Thereby the construction of solutions is provided either by semiflows, on the time-continuous level, or by using Alternating Minimizing Movements in the time-discrete setting. In both cases the convergence analysis relies on the energy-dissipation principle for gradient systems.

Synergistic mechanism of the energy dissipation and sediment erosion in pump turbine under sand-laden water based on entropy production theory

Synergistic mechanism of the energy dissipation and sediment erosion in pump turbine under sand-laden water based on entropy production theory

Structure of mushy layers grown from perfectly and imperfectly conducting boundaries. Part 2. Onset of convection

We study linear convective instability in a mushy layer formed by solidification of a binary alloy, cooled by either an isothermal perfectly conducting boundary or an imperfectly conducting boundary where the surface temperature depends linearly on the surface heat flux. A companion paper (Hitchen & Wells, J. Fluid Mech., 2025, in press) showed how thermal and salinity conditions impact mush structure. We here quantify the impact on convective instability, described by a Rayleigh number characterising the ratio of buoyancy to dissipative mechanisms. Two limits emerge for a perfectly conducting boundary. When the salinity-dependent freezing-point depression is large versus the temperature difference across the mush, convection penetrates throughout the depth of a high-porosity mush. The other limit, which we will call the Stefan limit, has small freezing-point depression and inhibits convection, which localises at onset to a high-porosity boundary layer near the mush–liquid interface. Scaling arguments characterise variation of the critical Rayleigh number and wavenumber based on the potential energy contained in order-one aspect ratio convective cells over the high-porosity regions. The Stefan number characterises the ratio of latent and sensible heats, and has moderate impact on stability via modification of the background temperature and porosity. For imperfectly conducting boundaries, the changing surface temperature causes stability to decrease over time in the limit of large freezing-point depression, but in the Stefan limit combines with the decreasing porosity to yield non-monotonic variation of the critical Rayleigh number. We discuss the implications for convection in growing sea ice.

Erratum to: Modulation mechanism of electron energy dissipation on superlubricity based on fluorinated 2D ZIFs

Erratum to: Modulation mechanism of electron energy dissipation on superlubricity based on fluorinated 2D ZIFs

Energy dissipation mechanism of G-phase and L-phase metallic glass nanofilms subjected to high-velocity nano-ballistic impact

Energy dissipation mechanism of G-phase and L-phase metallic glass nanofilms subjected to high-velocity nano-ballistic impact

Phase-field modeling of ductile fracture in bioinspired interfaces with dissipative structures

Intrinsic toughening, which occurs during ductile fracture and is motivated by plasticity, plays an important role in the industrial design of biomimetic composites. The interface structure in biomimetic composites can serve as a source of energy dissipation and stress relaxation, thereby achieving the goal of toughening. A new ductile fracture mechanism is proposed considering the influence of accumulated plastic deformation on local fracture toughness in a ductile phase-field model. The inducement to control the toughening mechanism is local energy dissipation, and the possible arrangement and shape of the dissipative structure are designed to capture the corresponding interface toughening mechanism. The channel structures of the barnacle substrate provide great inspiration for the structural toughening of the interface. The toughening mechanisms of weak interfaces are further explored by 3D printing structure specimens. The results indicate that the form of the R-curve is like a mixture of local J shaped and Γ shaped R-curves, which can also be called a periodic alternating mode. The J shaped R-curve represents the dissipation mechanism of the channel shape, while the Γ shaped R-curve represents the periodic crack arrest caused by local deformation of the channel.

Energy dissipation in pearlitic steel under impact loading

Energy dissipation plays a crucial role in the mechanical performance of pearlitic steel, particularly as structural materials subjected to impact loading. However, quantitatively distinguishing various dissipative mechanisms remains a great challenge due to the extremely short temporal and small spatial scales of shock deformation. In this paper, we address this challenge by performing molecular dynamics simulations of pearlitic steel under planar shock waves, generated by a piston moving at constant velocities. It is revealed that, the ratio of energy dissipation to input energy is inversely correlated with the piston velocity. The shock energy dissipates via the heat and structural contributions. The former accounts for 100% of the dissipation for pure elastic deformation, while it still consumes more than 93% of the dissipation when the deformation occurs beyond elasticity. In structural dissipation, the main contributor is the formation of new surfaces due to voids and spallation.

Tunable underwater sound absorption via piezoelectric materials with local resonators

In recent years, piezoelectric composite materials have been widely used in the design of underwater anechoic coatings due to their adaptability to tuning parameters. However, there are also some shortcomings, such as a single dissipation mechanism, narrow bandwidth, and poor low-frequency sound absorption. This work proposes an acoustic composite structure combining piezoelectric composite materials with local resonance units, which effectively enhances the sound absorption performance of the structure through the coupling effect of the piezoelectric energy consumption mechanism and local resonance mechanism. Compared to conventional acoustic structures, the proposed acoustic composite structure not only has a strong low-frequency sound absorption effect but also enriches the mid-high frequency sound absorption modes by connecting shunt damping circuits. On this basis, the effect of piezoelectric parameters and resonator morphological properties on structural sound absorption performance is further investigated, and the results show that the designed structure has the characteristic of sound absorption performance that is tunable. In addition, key factors affecting the sound absorption performance of the structure have been optimized to achieve better broadband sound absorption performance. This work may provide valuable ideas for the development of low-frequency broadband adjustable underwater sound-absorbing coatings.

Metal coordination network polyurethane adhesives based on energy dissipation mechanism: Excellent adhesion and flame retardant properties

Metal coordination network polyurethane adhesives based on energy dissipation mechanism: Excellent adhesion and flame retardant properties

Numerical study of turbulent flow boiling heat transfer in structured cooling channels using lattice Boltzmann method with advanced outlet boundary conditions

This study investigated the application of the lattice Boltzmann (LB) method to simulate turbulent flow boiling in structured cooling channels. The simulation used a central moment-based pseudopotential LB model with advanced characteristic boundary conditions to address numerical instabilities associated with turbulent multiphase flow. This approach ensures prolonged stability, facilitating the accurate modeling of complex flow boiling dynamics. The simulation results revealed that structured cooling channels considerably enhanced thermal performance, achieving a 27.3% increase in critical heat flux compared to flat channels. This improvement is induced by the fin structure of structured cooling channel, which makes heat distribution and promotes lower local wall heat flux compared with incident heat flux. Moreover, the simulations showed that fin structures manage bubble detachment more effectively, thereby enhancing heat transfer during the phase-change process. The study suggests that advanced outlet boundary conditions are crucial in stabilizing simulations for fin-structured channels, and the findings provide significant insights into heat dissipation mechanisms in high-heat-flux applications.

Study on the Mechanism of Energy Dissipation in Hemispherical Resonator Gyroscope.

The hemispherical resonator gyroscope is a gyroscope based on the principle of Coriolis vibration, widely used in inertial measurement systems of spacecraft. This article decomposes the gyroscope into two parts: the resonator shell and the gyroscope head, establishes the energy dissipation mechanism of the gyroscope, and conducts experimental verification. Firstly, based on the working principle of the gyroscope, a mechanical analysis model of the hemispherical resonator gyroscope head with a resonator spherical shell containing quality defects under second-order vibration state was established. The unbalanced force applied by the resonator spherical shell to the hemispherical resonator gyroscope head was analyzed, and the energy transfer path and dissipation mechanism from the spherical shell to the hemispherical resonator gyroscope head were explained. Finally, through the constructed testing platform, the circumferential quality factor test of the hemispherical resonator gyroscope before and after assembly was completed according to the designed experimental plan, and the consistency between theory and experimental phenomena was verified experimentally.

Tunable Mechanically Interlocked Semi‐Crystalline Networks

High‐performance polymers based on dynamic chemistry have been widely explored for multi‐field advanced applications. However, noncovalent sacrifice bond mediated energy dissipation mechanism causes a trade‐off between mechanical toughness and resilience. Herein, we achieved the synchronous boost of seemingly conflicting material properties including mechanical robustness, toughness and elasticity via the incorporation of mechanical chemistry into traditional semi‐crystalline networks. Detailed rheological tests and all‐atom molecular dynamics simulation reveal that the excellent mechanical robustness and toughness are attributed to the dissociation of crystalline domains threading through the sieve‐shape macrocycles. Reversible nano‐crystalline domains and ring‐sliding effect accelerated segment motion efficiently reduce energy dissipation to achieve instantaneous resilience. Moreover, the model polymers demonstrate that the multiple dynamic components endow the resulting polymer with excellent reprocessability under mild conditions. This mechanically interlocked semi‐crystalline polymer exhibits potential application as thermal/photo actuator. This work deeply reveals the synergic effects of mechanically interlocked sites and tunable crystalline domains, thus providing a reliable guide for comprehensive improvement of material performance.

Tunable Mechanically Interlocked Semi-Crystalline Networks.

High-performance polymers based on dynamic chemistry have been widely explored for multi-field advanced applications. However, noncovalent sacrificial bond-mediated energy dissipation mechanism causes a trade-off between mechanical toughness and resilience. Herein, we achieved the synchronous boost of seemingly conflicting material properties including mechanical robustness, toughness and elasticity via the incorporation of mechanical chemistry into traditional semi-crystalline networks. Detailed rheological tests and all-atom molecular dynamics simulation reveal that the excellent mechanical robustness and toughness are attributed to the dissociation of crystalline domains threading through the sieve-shape macrocycles. Reversible nano-crystalline domains and ring-sliding-effect accelerated segment motion efficiently reduce energy dissipation to achieve instantaneous resilience. Moreover, the model polymers demonstrate that the multiple dynamic components endow the resulting polymer with excellent reprocessability under mild conditions. This mechanically interlocked semi-crystalline polymer exhibits potential applications as a thermal/photo actuator. This work reveals the synergic effects of mechanically interlocked sites and tunable crystalline domains, thus providing a reliable guide for the comprehensive improvement of material performance.

Experimental Investigation of Embedment Depth Effects on the Rocking Behavior of Foundations

Shallow foundations supporting high-rise structures are often subjected to extreme lateral loading from wind and seismic activities. Nonlinear soil–foundation system behaviors, such as foundation uplift or bearing capacity mobilization (i.e., rocking behavior), can act as energy dissipation mechanisms, potentially reducing structural demands. However, such merits may be achieved at the expense of large residual deformations and settlements, which are influenced by various factors. One key factor which is highly influential on soil deformation mechanisms during rocking is the foundation embedment depth. This aspect of rocking foundations is investigated in this study under varying subgrade densities and initial vertical factors of safety (FSv), using the PIV technique and appropriate instrumentation. A series of reduced-scale slow cyclic tests were performed using a single-degree-of-freedom (SDOF) structure model. This study first examines the deformation mechanisms of strip foundations with depth-to-width (D/B) ratios of 0, 0.25, and 1, and then explores the effects of embedment depth on the performance of square foundations, evaluating moment capacity, settlement, recentering capability, rotational stiffness, and damping characteristics. The results demonstrate that the predominant deformation mechanism of the soil mass transitions from a wedge mechanism in surface foundations to a scoop mechanism in embedded foundations. Increasing the embedment depth enhances recentering capabilities, reduces damping, decreases settlement, increases rotational stiffness, and improves the moment capacity of the foundations. This comprehensive exploration of foundation performance and soil deformation mechanisms, considering varying embedment depths, FSv values, and soil relative densities, offers insights for optimizing the performance of rocking foundations under lateral loading conditions.

Mitigation of energy dissipation of graphene resonators by introduction of boron-nitride

Uncovering the material dissipation mechanisms of two-dimensional materials is essential for their implementation in advanced devices. While graphene resonators are highly attractive due to their high operational frequency and excellent durability, they dissipate a considerable amount of energy due to significant material dissipation associated with atomic friction manifested by the relative slipping of atomic layers. We mitigate the atomic friction by changing the atomic composition of the devices through the insertion of boron and nitride atoms that create polar interlayer bonds and, therefore, also reduce the energy dissipation. As a case study, we built boron carbonitride (BCN) foam cantilever devices and studied their frequency responses compared to those of their graphene counterparts. Indeed, we show that inserting boron and nitride atoms into the lattice improves the interlayer interactions and, thus, reduces the interlayer atomic friction. In addition, the air dissipation of BCN is also lower than that of graphene. Therefore, we pave the path for the development of BCN devices with tunable dissipation.