Initial Energy Research Articles

Willmore flow of complete surfaces

We consider the Willmore flow equation for complete, properly immersed surfaces in Rn. Given bounded geometry on the initial surface, we extend the result in [5] and prove short time existence and uniqueness of the Willmore flow. We also show that a complete Willmore surface with low Willmore energy must be a plane, and that a Willmore flow with low initial energy and Euclidean volume growth must converge smoothly to a plane.

Energy deficit in surgery on the examples of cholestasis and massive liver resection

The paper is dedicated to the energy processes associated with diseases in living organisms. Experiments involved 151 rats. Liver tissue was taken to determine its energy state in cholestasis (common bile duct ligation) and after resection of 60% and 80% of the parenchyma (without cholestasis). Adenine nucleotides (ATP, ADP, and AMP) and activity of gluconeogenesis enzymes were studied in cholestasis every 3 days for 15 days and after liver resection – every 6 hours for 3 days. Particular attention was paid to the energy deficit in liver tissue. A certain level of energy deficit n agent of metabolic stress. The experiments revealed that the energy deficit in the liver tissue increased by 15% by day 6 of cholestasis and by 48–50% of the initial energy level by days 12–15. The increase in energy deficit in liver tissue inversely correlated with the decrease in the activity of gluconeogenesis enzymes – by day 15 glucose-6- phosphate dehydrogenase reduced by 44% and isocitrate dehydrogenase – by 48% of the initial energy level. Decompression after 15 days from the onset of cholestasis was followed by an increase in energy deficit by 15%, as compared to the initial energy level, within 3–5 days. No development of metabolic stress was evidenced by a decrease in the activity of gluconeogenesis enzymes. After 12 hours after resection of 60% and 80% of the liver parenchyma, the liver energy deficit in both groups accounted for 50% of the initial energy level. After resection of 60% of the liver parenchyma, the energy deficit decreased rapidly: after 24 hours to 30%, after 72 hours to 11%; 2 rats out of 30 died during this period. After 12 hours after resection of 80% of the liver parenchyma, the energy deficit rose sharply: after 24 hours to 70% of the initial energy level. This led to the death of 26 animals out of 31. Both groups of animals demonstrated an inverse relationship between the decreased amount of energy used for hepatocyte function and the increased activity of key enzymes of gluconeogenesis. The obtained results suggest that in both groups of animals, metabolic stress developed after liver resection, however, after resection of 80% of the organ parenchyma, it “choked” due to the deficit of remnant hepatocytes. Most of the energy was spent for the development of regeneration. Metabolic stress and regeneration develop simultaneously. A deficit of 50% of energy in liver tissue with a further increase may indicate a critical condition, both in cholestasis and after a massive resection. The research into energy changes in cholestasis and after massive liver resections reveals new patterns of internal processes of the body.

Toward high-fidelity Numerical Wave Tank development: Scale resolving Partially-Averaged Navier–Stokes simulations of dam-break flow

Numerical Wave Tanks (NWTs) based on Navier–Stokes equations are emerging as valuable tools for simulating various ocean and coastal engineering flows. By capturing essential hydrodynamic non-linearities, including turbulent processes, these Navier–Stokes based NWTs can potentially provide high-accuracy data to complement traditional experimental wave basins for design and development applications. Many NWT approaches currently use the RANS (Reynolds Averaged Navier–Stokes) method. For many coastal resiliency and wave-energy converter applications, a higher fidelity turbulence treatment may be needed. In this work, we explore the applicability of the scale-resolving Partially-Averaged Navier–Stokes (PANS) technique for NWT computation. The PANS model is employed to study the dam-break benchmark case which is an important benchmark case for seawall and wave energy converter hydrodynamics analysis. Computations using RANS are also provided as a reference for accuracy and computational effort. The objectives are to: (i) investigate the effect of enhancing turbulence scale resolution on the pressure field, wave elevation and three-dimensional effects within the tank; and (ii) examine the influence of initial kinetic energy and grid resolution on the results. It is shown that, the early transient behavior is reasonably insensitive to scale resolution or initial turbulence level. Indeed, RANS and PANS of different scale resolutions yield similar results in the early stages as the flow physics is dominated by quasi-linear flow processes. The differences between RANS and PANS appear at later times. The so-called second pressure peak, standing wave amplitude and three-dimensional effects are better captured with increasing scale resolution for the same grid resolution. Overall, the results indicate that PANS is a viable model for NWT applications, with more detail being captured at a similar computational cost compared to RANS.

Blow-up phenomena for a singular nonlocal viscoelastic problem with logarithmic nonlinearity

This article deals with the blow-up phenomena for a singular nonlocal viscoelastic equation with logarithmic nonlinearity subject to nonlocal boundary conditions u(α,t)=0 and ∫0αxu(x,t)dx=0. Under the three different initial energy levels, we established the finite time blow-up criterion, and then give the upper bounds for blow-up time T∗ depending on the sign and range of initial energy E(0).

Моделювання коливальних процесів віброударних систем

In order to improve the efficiency of methods and means of mathematical modeling of vibro-impact systems, a generalized function of the periodic mode of movement of the executive body has been developed. It is presented in the form of the dependence of the shock impulse on the ratio of the angular velocities of the linear conservative system and its own. When obtaining this function, the Heaviside integral jump function and the periodic Green's function were used. The function of the dependence of the oscillation frequency on the impact impulse is determined from the impact conditions for the function of the system's response to a periodic sequence of impulses. The design model of a vibroimpact system is considered, both with one impact element and a motion limiter, and with a double-sided impact pair with alternate impact interactions with the limiters. In the intervals between impacts, there is a linear force interaction. When developing the mathematical model, a stereomechanical impact model was used, which is characterized by the velocity recovery coefficient after the impact. The analysis of the dependence function of the oscillation frequency on the shock impulse made it possible to obtain skeletal diagrams of resonant and quasi-resonant oscillations of vibro-impact systems with one and many degrees of freedom. Based on the obtained phase diagrams of the state of vibro-impact systems, it was determined: in a system with a gap, an increase in the impact speed increases the oscillation frequency, and the vibro-impact nonlinearity is «hard»; in a system with tension, with an increase in the value of the shock impulse, the oscillation frequency decreases (nonlinearity is «soft»). In the absence of a gap, the system is isochronous. Depending on the initial energy reserve and the location of the limiters in an asymmetric oscillatory system, with one degree of freedom, there can be vibro-impact modes with both one (closer located) and both limiters. In a linear conservative system with several degrees of freedom, a single-impact T-periodic regime is realized. If the dissipation during motion and impact is very small, then a regime close to resonant can exist in the system. In this case, periodic oscillations are supported by a weak external periodic force. The developed mathematical model makes it possible to fully describe the process of changing the relative coordinate of the movement of the working body, both in transient and in the established modes of movement of the system.

Enhancing the crack initiation resistance of hydrogels through crosswise cutting

The achievement of tough adhesion between hydrogels and solid surfaces has significantly expanded the potential applications of hydrogels. This robust adhesion is commonly attained by combining tough hydrogels with strong interfacial bonding and it is reflected in high adhesion toughness. However, the practical use of such strategies is limited since enhanced adhesion diminishes rapidly after cyclic loading. Furthermore, relying solely on adhesion toughness as a measure of adhesion quality may underestimate the adhesive's bearing capacity. To address these issues, here we introduce a macro-structural design strategy called crosswise cutting in hydrogels and propose a new measure of hydrogel adhesion named crack initiation resistance. This strategy can significantly enhance hydrogel adhesion by increasing the peak peel force while constraining the crack initiation length, thus improving the crack initiation resistance. The toughening mechanism behind this strategy is further explored by decomposing the crosswise cutting into longitudinal and transverse cuttings. Through extensive experiments, we demonstrate that longitudinal cutting can increase both the peak peel force and crack initiation length during peeling. Conversely, transverse cutting can constrain the crack initiation length while maintaining a high peak peel force. To quantitatively evaluate the crack initiation resistance of an adhesion system, we define a new parameter, the critical crack initiation energy release rate (Gc*), which considers both the peak peel force and crack initiation length. Theoretical derivations of Gc* for hydrogels with longitudinal and transverse cuttings are provided. By varying cutting types, hydrogel thickness, and cut sizes, the value of Gc* can be significantly increased, with the optimal choice being the crosswise cutting satisfying specific dimensions. The underlying mechanisms pertaining to the increase of Gc* via crosswise cutting are explained by the stress de-concentration effect, and the value of Gc* can be predicted by the macroscopic Lake-Thomas model. It is hoped that this study will draw attention to the assessment of the adhesion quality of hydrogels in practical applications and provide some new insights for the design of future soft adhesives.

Influence of Cargo Luggage on the Vertical Drop Crashworthiness of Aircraft Mid-Fuselage Section

The evaluation of structural crashworthiness is important for the development of civil aircraft. In this study, cargo luggage was considered in the vertical drop simulation of an aircraft mid-fuselage section. First, quasi-static compression tests on three types of luggage made of different materials were conducted. Then, a finite element model (FEM) of the cargo luggage was developed with a crushable foam material in LS-PrePost4.5 software. The finite element analysis results of the luggage made of different materials were consistent with the corresponding compression experiments. Secondly, the FEM of the mid-fuselage section was established without cargo luggage. The simulated displacement and acceleration of the fuselage section were consistent with the test results. Finally, the influences of cargo luggage on the fuselage vertical drop response were studied with the FEM considering both the fuselage structure and cargo luggage. Compared with the responses of the fuselage without cargo luggage, the cargo luggage could reduce the deformation of the cargo bay and maintain the integrity of the passenger living space in the cabin at the vertical velocity of 6 m/s, even though the initial kinetic energy was higher.

Primary processes in bacterial reaction center revealed by femtosecond broadband fluorescence spectroscopy

To gain a deeper understanding of the highly efficient mechanisms within the photosynthetic bacterial reaction center (BRC), we have employed femtosecond broadband fluorescence spectroscopy to investigate the dynamics of initial photo-induced energy transfer and charge separation in BRC at room temperature. Benefiting from the broadband spectral coverage inherent of this technique, two distinct transient emission species associated with bacteriochlorophylls B and P are directly identified, with Stokes shifts determined to be ~197 and 450 cm−1, respectively. The ultrafast energy transfers from bacteriopheophytin H to B (98 fs) and from B to P (170 fs) are unveiled through fitting the emission dynamics. Notably, the anticipated sub-200 fs lifetime of B emission significantly extends to ~400 fs, suggesting a plausible coupling between the electronic excited state of Band the vibronic states of P, potentially influencing the acceleration of the energy transfer process. These findings should pave the way for understanding the impact of vibronic dynamics on the photo-induced primary processes in the photosynthetic reaction center.

Underwater electrical explosion of metallic wire and tube: A comparison study

With an initial energy storage of approximately 53.5 kJ, experiments on underwater electrical explosions of metallic wire and thin-wall tube were conducted. Two sets of controlled experiments were designed, and the wire and tube for each set were of the same length, cross-sectional area, and material. Load voltage, circuit current, and shock wave pressure were measured and analyzed, and electric power, energy deposition, and energy deposition rate were also calculated and investigated. Experimental results indicated that the underwater electrical tube explosion (UETE) always has higher and earlier local resistance peak, voltage peak, and electric power peak, as well as faster phase transition and ionization process than the underwater electrical wire explosion (UEWE). In addition, the energy deposition rate from the beginning of discharge or the decrease in current to the voltage peak is significantly increased when replacing a wire with a tube. For the shock-wave characteristics, the peak pressure, energy density, and impulse of the shock wave generated by UETE are greater than that generated by UEWE. The peak pressure at ∼33 cm increased from 21.1 to 24.5 MPa in the first set and from 18.1 to 21.7 MPa in the second when a tube was used instead of a wire. These experimental results help us understand the physical process of UETE and provide an alternative methodology for load design in industrial applications.

Black hole binaries in AGN accretion discs – II. Gas effects on black hole satellite scatterings

ABSTRACT The black hole (BH) binaries in active galactic nuclei (AGN) are expected to form mainly through scattering encounters in the ambient gaseous medium. Recent simulations, including our own, have confirmed this formation pathway is highly efficient. We perform 3D smoothed particle hydrodynamics (SPH) simulations of BH scattering encounters in AGN discs. Using a range of impact parameters, we probe the necessary conditions for binary capture and how different orbital trajectories affect the dissipative effects from the gas. We identify a single range of impact parameters, typically of width ∼0.86−1.59 binary Hill radii depending on AGN disc density, that reliably leads to binary formation. The periapsis of the first encounter is the primary variable that determines the outcome of the initial scattering. We find an associated power law between the energy dissipated and the periapsis depth to be ΔE ∝ r−b with b = 0.42 ± 0.16, where deeper encounters dissipate more energy. Excluding accretion physics does not significantly alter these results. We identify the region of parameter space in initial energy versus impact parameter where a scattering leads to binary formation. Based on our findings, we provide a ready-to-use analytic criterion that utilizes these two pre-encounter parameters to determine the outcome of an encounter, with a reliability rate of >90 per cent. As the criterion is based directly on our simulations, it provides a reliable and highly physically motivated criterion for predicting binary scattering outcomes which can be used in population studies of BH binaries and mergers around AGN.

Blue diode lasers – Understanding and influencing melt pool dynamics in copper

Within the last years an increasing demand of copper components was observed, especially in the fields of energy transition, e-mobility, or digitalization. For joining those components, laser welding has become more and more popular. Infrared lasers are commonly used for metal welding. They are characterized by a low absorptivity in solid copper at room temperature. In contrast, lasers in the blue wavelength spectrum are characterized by a significantly higher absorptivity. This facilitates the initial energy input into the material and makes the welding process more efficient. Further, in the liquid state, the absorptivity change in copper is much smaller for the blue wavelength. This results in a continuous heating of the material, a more stable melt pool and a lower amount of spatter. One supplier of lasers in the visible wavelength spectrum is Laserline. In 2023, they launched a 4 kW blue diode laser, the currently highest available power for this wavelength. It makes accessible a broad variety of applications. But the scientific investigations for the blue wavelength at a power of several kilowatt are still limited. It is the paper’s purpose to extend them by analysing welding of copper and its alloys with a blue diode laser. One the one hand, synchrotron trials were performed allowing a look into the material during welding. A special focus was on the transition between heat conduction and deep penetration welding as well as the keyhole behaviour. On the other hand, conventional welding trials were performed analysing the impact of beam shaping on the melt pool dynamics.

Estimating the initial fracture energy of concrete using various machine learning techniques

The assessment of the energy required for crack propagation in concrete structures has been fascinating since fracture mechanics was applied to concrete. In the case of concrete, considered a quasi-brittle material, the fracture energy has proven to be a crucial factor in the reliable design of structures and modeling failure behavior. However, due to the complex, time-consuming, and expensive laboratory tests, there has been ongoing and intense debate regarding the methods to estimate the fracture energy of concrete. The advent of machine learning (ML) methods in this domain can hold great promise for resolving such issues once and for all. This study used a comprehensive analysis of twelve ML algorithms for estimating the initial fracture energy of concrete (IFEC), utilizing a more extensive and diverse database (500 data points) than previous studies. The performance of the ML models was evaluated using several metrics, such as coefficient of determination (R2) and variance accounted for (VAF). The findings revealed that all the ML models employed in this study demonstrate remarkable accuracy in estimating the IFEC value, with R2 and VAF values of more than 0.86 and 93.10 %, respectively. A ranking of the models based on their estimation accuracy was provided, facilitating the selection of the support vector regression (R2 = 0.9897; VAF = 99.50 %) and long-short-term memory (R2 = 0.9804; VAF = 99.00 %) methods as the most reliable models for IFEC estimation. Both the laboratory test and ML models presented the highest IFEC value for a water-to-cement ratio of 0.35. Additionally, by increasing the values of each of the parameter's maximum size of aggregates (from 7 mm to 35 mm) and the specimen’s age (from 3 days to 180 days), the IFEC value was increased by about 100 %. Notably, a user-friendly software based on the ML models was developed, enabling fast and highly accurate estimation of IFEC, thereby eliminating the need for time-consuming and expensive laboratory tests.

Global well posedness for the semilinear edge-degenerate parabolic equations on singular manifolds

Abstract In this article, we study the long-time dynamical behavior of the solution for a class of semilinear edge-degenerate parabolic equations on manifolds with edge singularities. By introducing a family of potential well and compactness method, we reveal the dependence between the initial data and the long-time dynamical behavior of the solution. Specifically, we give the threshold condition for the initial data, which makes the solution exist globally or blowup in finite-time with subcritical, critical, and supercritical initial energy, respectively. Moreover, we also discussed the long-time behavior of the global solution, the estimate of blowup time, and blowup rate. Our results show that the relationship between the initial data and the long-time behavior of the solution can be revealed in the weighted Sobolev spaces for nonlinear parabolic equations on manifolds with edge singularities.

Predictors of Transthoracic Impedance in Patients Who Underwent Elective Electrical Cardioversion

Successful synchronized direct current cardioversion (DCCV) requires adequate current delivery to the heart. However, adequate current for successful DCCV is not yet established. Trans-myocardial current depends on two factors: input energy and transthoracic impedance (TTI). While factors affecting TTI have been studied in animal models, factors affecting TTI in humans have not been well established. Here we explored the potential factors that affect TTI in humans. Retrospective review of patients undergoing DCCV at a large quaternary medical center between October 2019 and August 2021 was conducted. Pertinent clinical information, including demographics, echocardiography findings, laboratory findings and body characteristics were collected. Cardioversion details including joules delivered and TTI were recorded by the defibrillator for each patient's first shock. Predictors of thoracic impedance were assessed using regression analysis. A total of 220 patients (29% female) were included in the analysis. 143 (65%) of the patients underwent DCCV for atrial fibrillation, 77 (35%) underwent DCCV for atrial flutter. Mean impedance in our population was 73 ± 18 ohms. In a regression model with high impedance defined as the upper quartile of our cohort, BMI, female sex, obstructive sleep apnea and chronic kidney disease (All p values <0.05) were significantly associated with high impedance. According to an ROC analysis, BMI has a high predictive value for high impedance, with an AUC of 0.76. In conclusion, our study reveals that elevated BMI, female sex, sleep apnea and chronic kidney disease were predictors of higher TTI. These factors may help in determining the appropriate initial shocking energy in patients undergoing DCCV for atrial fibrillation and flutter.

A special phenomenon of wave interactions: An application of nonlinear evolution equation in (3+1)-dimension

The Lie group transformation approach can be used in the reduction of the generalized (3+1)-dimensional nonlinear evolution equation to ordinary differential equations (ODEs). In this work, infinitesimal generators, commutator table of Lie algebra, adjoint representation of subalgebras, symmetry group, and similarity reduction for (3+1)-dimensional shallow-water-like (gSWL) equation are obtained. Interactions of soliton solutions of a gSWL equation are evaluated that depict how near-inertial waves affect the dynamics of barotropic and baroclinic balanced flows. It is shown that the temporo-spatial localization of multi-soliton complexes (MSCs), gradually escalating incoherent interactivity amidst multi parameter group of MSCs along with spatial inhomogeneity alter the shape of quasi-periodic MSCs. The interactions among bright and dark solitons are shown. The increased number of solitons and increased self-interactions among solitary waves contribute to an unstable wave field. Breathers have a well-separating and initial localized energy domain. A limiting case of breather solutions is the peregrine soliton. Thus, interactions among these soliton structures show that multiple breathers retain their wave characteristic.

Prompt photon production in proton–nucleus collisions at LHC: a comparison among color dipole models* *Supported by the National Natural Science Foundation of China (Grant No. U1832120), the Natural Science Foundation for Outstanding Young Scholars of Hebei Province (Grant No. A2020210012), the S&T Program of Hebei (Grant No. 236Z4601G), and the Scientific Research Foundation for the Introducing Returned Overseas Chinese Scholars

The nuclear modification factor for prompt photon production in proton–nucleus collisions is investigated within color dipole formalism. By means of the Glauber–Gribov approach, the nuclear effects are studied in various rapidity bins with the evolution equation-based saturation models and the phenomenological dipole models. The theoretical results are compared with the experimental data provided by PHENIX, ATLAS and CMS Collaborations. At forward rapidity and midrapidity, a reasonable agreement with the experimental data is shown for the theoretical results with the modified Kharzeev, Levin and Nardi model, and the Kowalski and Teaney model. Then, we analyze the influence of the initial state energy loss effect on the nuclear modification factor and find that it is obvious only at backward rapidity together with small p T. Finally, the theoretical results are also compared with those of JETPHOX Monte Carlo program and the predictive results for the LHCb at very forward rapidities are presented.

On the post-impact fatigue behavior and theoretical life prediction of CF/PEEK-titanium hybrid laminates using an energy dissipation approach

This paper aims to illustrate the effect of the impact damage on fatigue behavior of CF/PEEK-titanium hybrid laminates. To achieve this end, a fatigue life model was proposed to predict the S–N curves of the laminates at various initial impact energy levels and stress ratios based on the energy dissipation approach. The energy dissipation behavior of the laminates during fatigue loading under different experimental conditions was analyzed through a large amount of post-impact fatigue tests, and the correlation between the initial impact damage and the total fatigue dissipation energy was determined. The full-field axial strain distribution of the titanium layer on the impacted side of the laminate was characterized in terms of initial impact energy level and maximum stress using digital image correlation, and then the post-impact fatigue failure mechanism of CF/PEEK-Ti hybrid laminates was summarized. Finally, the validity of the proposed model was verified by fatigue tests under other conditions of stress ratio and impact energy level. It is worth mentioning that the proposed model is also applicable to other types of FMLs, and can accurately predict the residual fatigue life of laminates after impact with only one set of S–N curve data.

Quantum Dynamics of Photodissociation: Recent Advances and Challenges.

Recent advances in constructing accurate potential energy surfaces and nonadiabatic couplings from high-level ab initio data have revealed detailed potential landscapes in not only the ground electronic state but also excited ones. They enabled quantitatively accurate characterization of photoexcited reactive systems using quantum mechanical methods. In this Perspective, we survey the recent progress in quantum mechanical studies of adiabatic and nonadiabatic photodissociation dynamics, focusing on initial state control and product energy disposal. These new insights helped to understand quantum effects in small prototypical systems, and the results serve as benchmarks for developing more approximate theoretical methods.

Global classical solutions for three-dimensional compressible isentropic magneto-micropolar fluid equations with Coulomb force and slip boundary conditions in bounded domains

In this paper, we study an initial-boundary value problem of three-dimensional (3D) compressible isentropic magneto-micropolar fluid equations with Coulomb force and slip boundary conditions in a bounded simply connected domain, whose boundary has a finite number of two-dimensional connected components. We derive the global existence and uniqueness of classical solutions provided that the initial total energy is suitably small. Our result generalizes the Cauchy problems of compressible Navier–Stokes equations with Coulomb force [S. Liu, X. Xu and J. Zhang, Global well-posedness of strong solutions with large oscillations and vacuum to the compressible Navier–Stokes–Poisson equations subject to large oscillations and non-flat doping profile, J. Differ. Equ. 269 (2020) 8468–8508] and compressible MHD equations [H. Li, X. Xu and J. Zhang, Global classical solutions to 3D compressible magnetohydrodynamic equations with large oscillations and vacuum, SIAM J. Math. Anal. 45 (2013) 1356–1387] to the case of bounded domains although tackling many surface integrals caused by the slip boundary condition are complex. The main ingredient of this paper is to overcome the strong nonlinearity caused by Coulomb force, magnetic field, and rotation effect of micro-particles by applying piecewise-estimate method and delicate analysis based on the effective viscous fluxes involving velocity and micro-rotational velocity.

Quantum and classical molecular dynamics for H atom scattering from graphene.

This work presents systematic comparisons between classical molecular dynamics (cMD) and quantum dynamics (QD) simulations of 15-dimensional and 75-dimensional models in their description of H atom scattering from graphene. We use an experimentally validated full-dimensional neural network potential energy surface of a hydrogen atom interacting with a large cell of graphene containing 24 carbon atoms. For quantum dynamics simulations, we apply Monte Carlo canonical polyadic decomposition to transform the original potential energy surface (PES) into a sum of products form and use the multi-layer multi-configuration time-dependent Hartree method to simulate the quantum scattering of a hydrogen or deuterium atom with an initial kinetic energy of 1.96 or 0.96 eV and an incident angle of 0°, i.e., perpendicular to the graphene surface. The cMD and QD initial conditions have been carefully chosen in order to be as close as possible. Our results show little differences between cMD and QD simulations when the incident energy of the H atom is equal to 1.96 eV. However, a large difference in sticking probability is observed when the incident energy of the H atom is equal to 0.96 eV, indicating the predominance of quantum effects. To the best of our knowledge, our work provides the first benchmark of quantum against classical simulations for a system of this size with a realistic PES. Additionally, new projectors are implemented in the Heidelberg multi-configuration time-dependent Hartree package for the calculation of the atom scattering energy transfer distribution as a function of outgoing angles.