Change In Potential Energy Research Articles

Potential Energy as Descriptor for Nanoparticle Coalescence

AbstractCoalescence is a fundamental process in gas‐phase synthesis of nanoparticles (NPs), affecting their structure and resultant properties. Various metrics are currently used to measure the degree of coalescence in atomistic simulation studies, such as the radius of the neck formed between the NPs’ centers of mass, gyration radii, sphericity, and surface area changes. A common characteristic of such metrics is that they typically require additional, often painstaking, data manipulation. Here, a new descriptor is introduced, the Overall Reduced Change in Potential Energy (ORCiPE) between initially uncoalesced and coalesced configurations. To benchmark the descriptor, its definition is analogous to that of the Overall Change in Surface Area, a common and dependable metric. When no phase transition occurred, comparison with other metrics confirms the reliability of ORCiPE in coalescing Au NPs. Considering that potential energy is a standard output property in atomistic simulations, ORCiPE is proposed as a valuable and facile coalescence metric.

Moment tensors for small earthquakes and the stress regime in the mid-Atlantic United States

Focal mechanisms for small magnitude earthquakes (M ~ 1.3–4.1) in the mid-Atlantic region of the United States have been determined using a double-couple moment tensor inversion procedure. The 26 new focal mechanisms obtained, when combined with previously published mechanisms, show a pattern of reverse faulting in the easternmost portion of the study area and strike-slip faulting in the west, consistent with previous studies. The change in focal mechanisms from east to west helps to constrain the geographic location of the east-west transition in the stress regime to a NE-SW area within central Pennsylvania within proximity of the Allegheny Front. Stress inversions performed to constrain variations in the stress state across the region show that the maximum compressive stress varies only slightly, but that the near-vertical stress is the minimum compressive stress in the east and transitions to the intermediate compressive stress in the west, as expected for an east-west transition in reverse to strike-slip faulting. Analysis of driving forces causing the stress change suggests that tectonic terrane structure, glacial isostatic adjustment, and changes in gravitational potential energy have little effect on the stress field in this region, leaving the interaction of sublithospheric mantle flow with the eastern edge of the Laurentian cratonic lithosphere beneath central Pennsylvania as a primary explanation. The cratonic lithospheric keel may cause a deflection in mantle flow, thereby changing the stress field enough so that the magnitude of the vertical stress in relation to the minimum horizontal stress results in strike-slip as opposed to reverse faulting.

Contrasting Response of Mesoscale Convective Systems Occurrence Over Tropical Land and Ocean to Increased Sea Surface Temperature

AbstractMesoscale convective systems (MCSs) are pivotal in global energy/water cycles and typically produce extreme weather events. Despite their importance, our understanding of their future change remains limited, largely due to inadequate representation in current climate models. Here, using a global storm‐resolving model that accurately simulates MCSs, we conclude contrasting responses to increased SST in their occurrence, that is, notable decreases over land but increases over ocean. This land‐ocean contrast is attributed to the changes in convective available potential energy (CAPE) and convective inhibition (CIN). Over land, notable rises in CIN alongside moderate increases in CAPE effectively suppress (favor) weak to moderate (intense) MCSs, resulting in an overall reduction in MCS occurrences. In contrast, substantial increases in CAPE with minimal changes in CIN over ocean contribute to a significant rise in MCS occurrences. The divergent response in MCS occurrence has profound impacts on both mean and extreme precipitation.

Understanding the role of chain stiffness in the mechanical response of cross-linked polymer: Flexible vs. semi-flexible chains

Cross-linked polymers are widely used in structural, engineering, and biomedical applications due to their lightweight and superior properties. Although chain bending stiffness has been recognized to play an essential role in their thermodynamical and mechanical properties, how it influences these properties of cross-linked polymers with flexible or semi-flexible chains remains under debate. Here, we systematically explore its influences utilizing coarse-grained (CG) molecular dynamics (MD) simulations based on a bead-spring CG model. It is found that with chain bending stiffness increasing, both density and elastic moduli (i.e., shear modulus and tensile modulus) of cross-linked polymers first decrease slightly and then decrease significantly followed by a gradual increase, along with the polymer transition from a dense cross-linked thermoset to a highly porous fibrous network. The moduli of cross-linked polymers with flexible and semi-flexible chains exhibit distinct scaling laws with the density. For cross-linked polymers with flexible chains, their moduli increase significantly with increasing strain rate, which correlates to the change in potential energy of interchain interaction during deformation. However, the moduli display slight dependence on strain rate for porous cross-linked polymers with sufficiently stiff chains, where the intrachain interactions (i.e., bond stretching and angle bending energies) become dominant and independent of strain rate. Moreover, the elastic moduli exhibit scaling laws with Debye-Waller factor for both dense cross-linked thermosets with flexible chains and highly porous networks with stiff backbones. Our work facilitates a better understanding for mechanical properties and deformation mechanism of cross-linked polymers with variable chain bending stiffness at molecular level, shedding light on tailoring mechanical properties of cross-linked polymers via chain engineering.

Strongly Coupled Simulation of Magnetic Rigid Bodies

AbstractWe present a strongly coupled method for the robust simulation of linear magnetic rigid bodies. Our approach describes the magnetic effects as part of an incremental potential function. This potential is inserted into the reformulation of the equations of motion for rigid bodies as an optimization problem. For handling collision and friction, we lean on the Incremental Potential Contact (IPC) method. Furthermore, we provide a novel, hybrid explicit / implicit time integration scheme for the magnetic potential based on a distance criterion. This reduces the fill‐in of the energy Hessian in cases where the change in magnetic potential energy is small, leading to a simulation speedup without compromising the stability of the system. The resulting system yields a strongly coupled method for the robust simulation of magnetic effects. We showcase the robustness in theory by analyzing the behavior of the magnetic attraction against the contact resolution. Furthermore, we display stability in practice by simulating exceedingly strong and arbitrarily shaped magnets. The results are free of artifacts like bouncing for time step sizes larger than with the equivalent weakly coupled approach. Finally, we showcase the utility of our method in different scenarios with complex joints and numerous magnets.

A low-cost method for quantifying bouncing ball dynamics with smartphone video

Abstract This study employed a low-cost method for quantifying bouncing ball dynamics with smartphone video. High-speed video analysis was used to investigate the bouncing behaviour of different balls, including table tennis, rubber, and tennis balls, on a table tennis surface. To examine the effect of surface material on bouncing dynamics, the table tennis ball was also tested on wood and tile surfaces. Key parameters analysed included bounce height decay, the coefficient of restitution (COR), and the bounce half-life. Additionally, we measured the total bouncing time and analysed the relationship between changes in gravitational potential energy, kinetic energy, and total mechanical energy (ME). Our results revealed a significant correlation between the COR and the decay rate of bounce height. Balls with higher COR values, indicative of lower energy loss per bounce, exhibited slower decay rates, resulting in longer bounce half-lives and extended total bounce times. For instance, the table tennis ball on a tile surface demonstrated a high COR of 0.93, a bounce half-life of 4.65 bounces, and a total bounce time of 8.22 ± 0.34 s. This suggests that material properties such as stiffness and elasticity of both the ball and the surface significantly influence the COR and decay rate, beyond just surface smoothness. Furthermore, our analysis of ME changes in the bouncing balls aligns with theoretical predictions, providing insights into the energy transformations occurring during bouncing. This improved understanding can also be a valuable tool for educators, helping teachers and students bridge the gap between theory and real-world observations, leading to a deeper grasp of the concepts.

Boosting the cold flow properties and oxidation stability of diesel-biodiesel blends by novel polymethacrylate graft copolymer nanocomposites

The applications and development of biodiesel fuels are restricted by the poor low-temperature fluidity and oxidation stability. Meanwhile, typical antioxidants are usually compounds containing phenyl groups, which have the disadvantages of high toxicity and carcinogenicity. To address these defects, our study originally synthesized a multifunctional additive using both post grafting and nanocomposite technology, as well as apply a biofuel antioxidant free of benzene ring group, 4-Amino-2,2,6,6-tetramethylpiperidine. Our findings reveal that the delayed crystallization behavior of B20 (20 vol%. biodiesel +80 vol%. diesel) is strongly dependent on the additive structure and amount, which the pour point (PP) and cold filter plugging point (CFPP) are decreased by 20 and 16 °C respectively at 1000 ppm. The post grafting technology enhanced additive antioxidant properties, which extend the induction period of B20 from 2.0 to 6.9 h. Our study confirmed the synthesized additives through possess synergistic enhancement effects on both cold flow properties and oxidation stability. In addition, DFT calculations simulating the potential energy changes of B20 solutions forecast copolymer structure affects the low-temperature fluidity. Hence this study pioneered the proposal for developing multifunctional additives through both post grafting and nanocomposite technology of methacrylate copolymer for biofuels, and provide a theoretical prediction strategy for exploring optimum copolymer pour point depressant for fuels.

Molecular dynamics simulation of alloying characteristics of Al–Mg nanoparticles under different process heating conditions

ABSTRACT The effect of thermal process parameters on the alloying of Al–10Mg (wt%) system has been studied in molecular dynamics approach. Five distinct values of heating rate have been considered for Al and Mg nanoparticles (NPs) to melt, coalesce followed by identical cooling. Detailed investigation of Al-Mg NPs alloying has been done in terms of alloying temperature, atomic migration, coalescence kinetics and mechanical characteristics for various heating rates were carried out. Prior to the alloying simulation, component melting simulations of Al and Mg single particles (SPs) were conducted to determine the melting temperature of NPs and to inspect their individual thermo-stability. From the change in potential energy, its evident that the melting temperature of the component NPs significantly depends on heating rates. Following the component melting, alloying simulations were conducted in three distinct phases: (i) heating, (ii) relaxation, and (iii) cooling and solidification. Following the solidification, uniaxial tensile test simulation was done on a block cut to characterise the mechanical behaviour in context to dislocation analysis, HCP evolution, stacking fault analysis and corresponding stress–strain relationship. Obtained results showed a substantial affiliation of heating rates and coalescence kinetics but showed minimal effect on mechanical properties.

Integrated analysis of on-road energy consumption and range optimization in the conversion of an IC engine vehicle to a battery-electric vehicle: a comprehensive research study

Abstract A major goal of this research project was to analyze how energy consumption and range of electric vehicles are affected by a variety of factors. The study includes an analysis of data based on factors such as state of charge, wheel traction power, power due to drag and aerodynamics, potential and kinetic energy changes, elevation, current, voltage, speed, and total loss due to traffic, and their effect on the consumption of energy and range of the electric vehicles. The data was analyzed using statistical methods such as MATLAB, Excel, and Python to find correlations between the various factors mentioned above. This research paper thoroughly explores the intricate relationships governing consumption of energy and range of the electric vehicles. Notably, this paper discovered connections between altitude and state of charge, current and state of charge, and even speed and voltage drop, highlighting the interplay of these elements. This paper also explored how factors like vehicle speed, slope, current, wheel traction power, and power due to gravity collectively shape EV propulsion dynamics. In simpler terms, this paper quantified energy losses due to traffic and emphasized how efficient motors and regenerative systems can significantly reduce these losses. Notably, regenerative efficiency stands out, cutting total energy losses by nearly half compared to scenarios where it is not used. These findings contribute to academic discussions and offer practical insights that undergraduate students can grasp, informing future EV designs and operations and promoting an energy-conscious transportation landscape.

Brownian Fluctuations of a non-confining potential

Brownian fluctuations arise for any quantity that depends on the stochastic variables of a Brownian particle. In this study, we explore the Brownian fluctuations of a two-dimensional quadratic potential that exhibits two regimes: A confining regime and a non-confining regime. Our analysis focuses on the statistical properties of the potential energy changes relative to an initial setup. We decompose the total potential into two components and thoroughly examine their mean, variance, skewness, and excess kurtosis, as well as their respective distributions. By analyzing these quantities individually, and with relation to the total potential, we gain insights into the nature of the statistical fluctuations of potential energy.

Unreliability of the gas discharge visualization (GDV) device and the Bio-Well for biofield science: Kirlian photography revisited and investigated. Part II

This is the second part of a research work to study the reliability of the Gas Discharge Visualization (GDV) device and the Bio-Well: These biofield machines, which are based on the Kirlian effect, were put to test in a Pranic Healing experiment. In the first part, the literature on Pranic Healing and Kirlian photography, as well as the functioning of the devices, were reviewed. In this second part, previous reliability studies on Kirlian photography devices are reported, explaining their negative results, and an original experiment is presented. The measurement variability and working of these technologies were investigated, evaluating their capacity to assess the energetic status of human beings and water. The experiment involved 40 participants: 20 Pranic healers and 20 non-healers. Healers performed a treatment on water, while non-healers simulated it; both groups were measured repeatedly before and after their real or sham performance; their water was measured as well and compared with controls. In the analysis, it was evaluated whether these Kirlian photography devices could return accurate, repeatable, and consistent information about the participants’ and water energy fields, allowing to detect potential subtle energy changes in the healer group compared to the non-healer one. The GDV-device and Bio-Well parameters showed large measurement variability and/or poor informative value, resulting inconsistent at detecting possible subtle energy variations in human beings and water. The findings of this research indicate that the GDV device and the Bio-Well may not be reliable tools for biofield science, and suggest that the literature related to these technologies should be revised and questioned.

Dipole Response of Mesoscale Eddy Formation to Monsoon Transition in the Southeast Tropical Indian Ocean

AbstractThe Southeast Tropical Indian Ocean (SETIO), dominated by the Indian Ocean monsoon, is an important source region for strong mesoscale eddies. To date, the impacts of the Indian Ocean monsoon on mesoscale eddies have not been clarified. Here we report on the dipole response of mesoscale eddy formation to monsoon transition in the SETIO, using satellite and reanalysis data sets. During the summer monsoon season, anticyclonic eddies are mainly concentrated north of 12°S, while cyclonic eddies are south of 12°S. This situation reverses during the winter monsoon season. We attribute this dipole feature to the oceanic perturbations and current shear during the different monsoon periods. A geographical boundary along 12°S aligns with meridional changes in eddy potential energy, which delineates the generation and direction of the newly‐formed eddies. The hot spot region, rich in eddy energy properties, tends to promote eddy formation and endurance during the monsoon periods.

Deriving the Average Change in Kinetic Energy of a Galaxy in Non-Relativistic Motion

This study presents a novel approach to calculating the average change in kinetic energy of galaxies exhibiting non-relativistic motion. The methodology integrates the dynamics of total observed motion, which encompasses both peculiar and recessive motion, with the gravitational influence of neighboring galaxies. The peculiar motion is quantified through peculiar redshift, while recessive motion is described by Hubble’s Law. The total observed velocity is the sum of these two components. The research derives an expression for the average acceleration of a galaxy based on the change in its total observed redshift wavelength over time. Utilizing Newton’s Second Law of Motion, the average observed force and subsequent work done by this force is calculated. The work done by conservative forces, primarily gravitational forces exerted by neighboring galaxies, is also considered to determine the total work done on the galaxy. Results indicate that the average total observed force causing the motion of a galaxy is a non-conservative force, resulting from the combined effects of non-conservative forces responsible for peculiar and recessive motion. The change in potential energy due to gravitational interactions with neighboring galaxies is accounted for, leading to the formulation of the average change in kinetic energy. The conclusion of the paper provides a comprehensive expression for the average change in kinetic energy of a galaxy, factoring in the mass of the galaxy, the speed of light, the total observed redshift, the change in distance with respect to Earth, and the gravitational constant. This expression is significant for understanding the dynamics of galactic motion and the forces at play in a non-relativistic context.

Future Increase in Lightning Around the South China Sea Under Climate Change

AbstractThe impact of global warming on lightning flash rates remains relatively unknown. In this study, the South China Sea (SCS) and the surrounding areas within Southeast Asia were selected to examine the long‐term trend and future projection of lightning activity based on the currently longest satellite‐based lightning data set available and climate models. Our study revealed a reduction in the observed lightning flash rates around the SCS, with a linear trend of −0.11 fl km−2 yr−2 during 1996–2013. In contrast, the precipitation around the SCS exhibited an increasing trend and was negatively correlated with the local lightning flash rate. The sea surface temperature gradient over equatorial Pacific Ocean, latent heat flux over the equatorial Indian Ocean, local convective available potential energy, precipitation and aerosol changes collectively accounted for 82% of the variance in the lightning fluctuations over the SCS and Southeast Asia. Multiple linear regression proxies of lightning flash rates were constructed and applied to the climate models. The models indicated that lightning activity around the SCS is projected to intensify by 10% and 12% by the end of the 21st century under SSP245 and SSP370, respectively.

An adaptive mesh scheme of the lattice spring model based on geometrical continuity

An adaptive mesh scheme is introduced for the lattice spring model (LSM), where the original triangular cells are subdivided into a set of smaller triangular cells. The scheme is based on geometrical continuity at the heterogeneous mesh boundary, where the refined grid cells intersect the original cell edge. The LSM simulations on the refined grid show a superior computational efficiency to the uniform grid. Each subdivision reduces the original cell edges by a factor of two. The refinement procedure was recursively applied ten times before any marked loss in accuracy was observed. The accuracy of the adaptive model is on par with a regular grid approach. More specifically, the characteristics of fracture cavity are comparable with a uniform grid of the same mesh density as the smallest cells in the adaptive approach. The fracture criterion such as J-integral, the elastic energy of the grid and potential energy change due to fracture growth and strain loading agree well with the theory of a mode I fracture, which enables simulations of process such as sub-critical fracture with a wide dynamic range.

Study on Confined Water in Flexible Graphene/GO Nanochannels.

The structural evolution of flexible nanochannels within a 2D material membrane, influenced by the ingress of water molecules, plays a crucial role in the membrane's filtration and structural stability. However, the experimental observation of nanoscale water is challenging, and current studies mostly focus on rigid nanochannels. Further investigation on the nanoconfined water is urgently needed, considering the flexibility and deformation of the channel. In this work, MD simulations and theoretical analyses are conducted to investigate the water structure and thermodynamic properties when confined within both rigid and flexible graphene/graphene oxide (GO) nanochannels. In free rigid graphene nanochannels, the interlayer distance exhibits a quantized increase with the number of water molecules, along with sudden changes in entropy, potential energy, and free energy of the water molecules. Meanwhile, in flexible graphene nanochannels, the average interlayer space increases linearly with the number of water molecules. In free rigid GO nanochannels, with the increase of oxidation concentration, the quantized increase in the interlayer space gradually diminishes, accompanied by a decrease in both potential energy and free energy. This work provides insights into the configurational evolution of flexible nanochannels within water, offering guidance in fields such as desalination and mass transport of 2D material membranes.

Molecular dynamics study on roles of surface mixed hydrate in the CH4/CO2 replacement mechanisms

The CH4/CO2 replacement method is a promising approach for the exploitation of natural gas hydrates, offering dual benefits of extracting CH4 and sequestering CO2. This technique not only facilitates the extraction process but also mitigates the greenhouse effect and maintains geological stability, thereby contributing to sustainable energy utilization and environmental preservation. Currently, there are multiple viewpoints about the replacement mechanism. Furthermore, mixed hydrates can form on the surface during the replacement process. The unclear mechanism of CH4/CO2 replacement and the obstruction of mass transfer caused by the mixed hydrate impede its practical applicability. Clarifying the effects of surface mixed hydrate in replacement mechanisms can offer valuable insights for identifying optimal operating conditions in practical exploitation applications. Therefore, the present study aims to reveal the significant roles of surface mixed hydrates in the replacement mechanism by employing the molecular dynamics simulation methodology. The results showed that under the mechanism of cage complete rupture, the surface mixed hydrate decomposes rapidly to form a thickening water zone. Additionally, each layer of the hydrate cage structure undergoes a process from deformation or partial rupture to sudden complete disintegration, which is concomitant with an abrupt change of potential energy. Under the mechanism of cage incomplete rupture, the surface mixed hydrates hinder mass transfer and decelerate the reaction rate. A similar situation arises when the number of the surface mixed hydrate layers is increased. Therefore, the key to distinguishing the replacement mechanism lies in whether the environmental conditions are sufficient to break the potential energy barrier of the surface mixed hydrate and disrupt its cage structure.

The effect of silica nanoparticles on the shock adiabatic relation and tensile strength in polyurethane

This work exploded the effect of silica nanoparticles on shock adiabatic relation and tensile fracture in polyurethane based on atomistic simulations. It is found that the non-uniform interface structures introduced by nanoparticles can increase the shock impedance, which also leading to increased twisting of polyurethane chains and the generation of local hotspots near the nanoparticles. The interface structures near the nanoparticle consists of polyurethane chains with a high gyration radius, and the average gyration radius increases approximately linearly with the increase in nanoparticle content. At lower shock velocity, the potential energy increment initially increases and then decreases with the increase in nanoparticle content. Bond analysis reveal that flexible segments dominate the bending and twisting deformations of polyurethane, while nanoparticles enhance the corresponding deformation degrees. Furthermore, nanoparticles can serve as void nucleation sites for early-stage tensile damage, resulting in a decrease in fracture strength. Differing from metals, the relationship between tensile strength and fracture temperature follows a more linear law. Nanoparticles inhibit the later growth and coalescence of voids by increasing the temperature and steric hindrance. The density and size distribution characteristics of voids are consistent with the changes in potential energy during the shock compression process. Unlike classical spallation, the curled polyurethane chains in the tensile region gradually orient along the shock direction, evolving into a void-fiber structure.

Crystal nucleation in an AlNiZr metallic liquid: Within and beyond classical nucleation theory

The Classical Nucleation Theory (CNT) has played a key role in crystal nucleation studies since the 19th century and has significantly advanced the understanding of nucleation. However, certain key assumptions of CNT, such as a compact and spherical nucleating cluster and the concept of individual diffusive jumps are questionable. The results of molecular dynamics (MD) studies of crystal nucleation in a Al20Ni60Zr20 metallic liquid demonstrate that the nucleating cluster is neither spherical nor compact. The seeding method was employed to determine the critical cluster size and nucleation parameters from CNT, which were then compared to those derived from the Mean First Passage Time (MFPT) method. While the CNT-based nucleation rate aligns well with experimental data from similar metallic liquids, the MFPT rate differs significantly. Further, contrary to the assumption of individual jumps for atoms to join the nucleating cluster, a cooperative mechanism of attachment or detachment is observed. This is accompanied by synchronized changes in the local potential energy. Similar cooperative motion also appeared in a non-classical nucleation process, particularly during the coalescence of nuclei.

N-doped Cu2O with the tunable Cu0 and Cu+ sites for selective CO2 electrochemical reduction to ethylene

The electrochemical carbon dioxide reduction reaction (CO2RR) to high value-added fuels or chemicals driven by the renewable energy is promising to alleviate global warming. However, the selective CO2 reduction to C2 products remains challenge. Cu-based catalyst with the specific Cu0 and Cu+ sites is important to generate C2 products. This work used nitrogen (N) to tune amounts of Cu0 and Cu+ sites in Cu2O catalysts and improve C2-product conversion. The controllable Cu0/Cu+ ratio of Cu2O catalyst from 0.16 to 15.19 was achieved by adjusting the N doping amount using NH3/Ar plasma treatment. The major theme of this work was clarifying a volcano curve of the ethylene Faraday efficiency as a function of the Cu0/Cu+ ratio. The optimal Cu0/Cu+ ratio was determined as 0.43 for selective electroreduction CO2 to ethylene. X-ray spectroscopy and density functional theory (DFT) calculations were employed to elucidate that the strong interaction between N and Cu increased the binding energy of NCu bond and stabilize Cu+, resulting in a 92.3% reduction in the potential energy change for *CO-*CO dimerization. This study is inspiring in designing high performance electrocatalysts for CO2 conversion.