Negative Stiffness Mechanism on An Asymmetric Wave Energy Converter by Using A Weakly Nonlinear Potential Model

Salter's duck,an asymmetrical wave energy converter(WEC)device,showed high efficiency in extracting energy from 2D regular waves in the past;yet,challenges remain for fluctuating wave conditions.These can potentially be addressed by adopting a negative stiffness mechanism(NSM)in WEC devices to enhance system efficiency,even in highly nonlinear and steep 3D waves.A weakly nonlinear model was developed which incorporated a nonlinear restoring moment and NSM into the linear formulations and was applied to an asymmetric WEC using a time domain potential flow model.The model was initially validated by comparing it with published experimental and numerical computational fluid dynamics results.The current results were in good agreement with the published results.It was found that the energy extraction increased in the range of 6%to 17%during the evaluation of the effectiveness of the NSM in regular waves.Under irregular wave conditions,specifically at the design wave conditions for the selected test site,the energy extraction increased by 2.4%,with annual energy production increments of approximately 0.8MWh.The findings highlight the potential of NSM in enhancing the performance of asymmetric WEC devices,indicating more efficient energy extraction under various wave conditions.

Ab initio potential energy surface and anharmonic vibration spectrum of NF_(3)^(+)

Potential energy surfaces(PESs), vibrational frequencies, and infrared spectra are calculated for NF_(3)^(+) using ab initio calculations, based on UCCSD(T)/cc-p VTZ combined with vibrational configuration interaction(VCI). Based on an iterative algorithm, the surfaces(SURF) program adds automatic points to the lattice representation of the potential function, the one-dimensional and two-dimensional PESs are calculated after reaching a convergence threshold, finally the smooth image of the potential energy surface is fitted. The PESs accurately account for the interaction between the different modes, with the mode q_(6) symmetrical stretching vibrations having the greatest effect on the potential energy change of the whole system throughout the potential energy surface shift. The anharmonic frequencies are obtained when the VCI matrix is diagonalized. Fundamental frequencies, overtones, and combination bands of NF_(3)^(+) are calculated, which generate the degenerate phenomenon between their frequencies. Finally, the calculated anharmonic frequency is used to plot the infrared spectra.Modal antisymmetric stretching ν_(5) and symmetric stretching ν_(6) exhibit a phenomenon of large-intensity borrowing. This study can provide data to support the characterization in the laboratory.

Properties of radiation defects and threshold energy of displacement in zirconium hydride obtained by new deep-learning potential

Zirconium hydride(ZrH_(2)) is an ideal neutron moderator material. However, radiation effect significantly changes its properties, which affect its behavior and the lifespan of the reactor. The threshold energy of displacement is an important quantity of the number of radiation defects produced, which helps us to predict the evolution of radiation defects in ZrH_(2).Molecular dynamics(MD) and ab initio molecular dynamics(AIMD) are two main methods of calculating the threshold energy of displacement. The MD simulations with empirical potentials often cannot accurately depict the transitional states that lattice atoms must surpass to reach an interstitial state. Additionally, the AIMD method is unable to perform largescale calculation, which poses a computational challenge beyond the simulation range of density functional theory. Machine learning potentials are renowned for their high accuracy and efficiency, making them an increasingly preferred choice for molecular dynamics simulations. In this work, we develop an accurate potential energy model for the ZrH_(2) system by using the deep-potential(DP) method. The DP model has a high degree of agreement with first-principles calculations for the typical defect energy and mechanical properties of the ZrH_(2) system, including the basic bulk properties, formation energy of point defects, as well as diffusion behavior of hydrogen and zirconium. By integrating the DP model with Ziegler–Biersack–Littmark(ZBL) potential, we can predict the threshold energy of displacement of zirconium and hydrogen in ε-ZrH_(2).

Geological reservoir and resource potential(10^(13)m^(3))of gas hydrates in the South China Sea

A detailed understanding of the distribution and potential of natural gas hydrate(NGHs)resources is crucial to fostering the industrialization of those resources in the South China Sea,where NGHs are abundant.In this study,this study analyzed the applicability of resource evaluation methods,including the volumetric,genesis,and analogy methods,and estimated NGHs resource potential in the South China Sea by using scientific resource evaluation methods based on the factors controlling the geological accumulation and the reservoir characteristics of NGHs.Furthermore,this study compared the evaluation results of NGHs resource evaluations in representative worldwise sea areas via rational analysis.The results of this study are as follows:(1)The gas hydrate accumulation in the South China Sea is characterized by multiple sources of gas supply,multi-channel migration,and extensive accumulation,which are significantly different from those of oil and gas and other unconventional resources.(2)The evaluation of gas hydrate resources in the South China Sea is a highly targeted,stratified,and multidisciplinary evaluation of geological resources under the framework of a multi-type gas hydrate resource evaluation system and focuses on the comprehensive utilization of multi-source heterogeneous data.(3)Global NGHs resources is n×10^(15)m^(3),while the NGHs resources in the South China Sea are estimated to be 10^(13)m^(3),which is comparable to the abundance of typical marine NGHs deposits in other parts of the world.In the South China Sea,the NGHs resources have a broad prospect and provide a substantial resource base for production tests and industrialization of NGHs.

Entrepreneurship training:its influences on innovation potentials among nursing students

Objective:To evaluate the influences of entrepreneurship training on the innovation potential among nursing students.Methods:A quasi-experimental design was utilized to conduct this study.The study was conducted in the classroom at the faculty of nursing,and the“i Hub”center at Ain Shams University(ASU)in Cairo,Egypt.A purposive sample of 42 nursing students who participated in the“Ain Shams University-innovate”competition from the Faculty of Nursing of ASU were included in this study.Data collection tools included(1)Nursing students'innovation skills assessment questionnaire and(2)Innovative projects evaluation tool.Results:There was a statistically significant difference between the mean scores of nursing students'total innovation skills pre-and post-implementation of entrepreneurship training,where P-value<0.05.Conclusions:The results of the current study support the research hypothesis because the implementation of entrepreneurship training positively affects nursing students'innovation potential.Developing entrepreneurship education in nursing and integrating it into nursing programs will stimulate creativity,innovation,and entrepreneurship among nursing students and health care services.

Potential energies of characteristic atoms on basis of experimental heats of formation of AuCu and AuCu_3 compounds(Ⅰ)

The systematic science of alloys(SSA)is a framework of the total energy and total volume able to be separated.The potential energy sequences of characteristic atoms at the central sites of the basic clusters in the fcc-based lattice Au-Cu system are separated out from smaller experimental heats of formation of L10-AuCu and L12-AuCu3 compounds only,by nine potential energy E-functions and through the use of structural unit inversion method.From these potential energy sequences,the potential energies and heats of formation of the disordered Au1-xCux alloys at 0 K are calculated.The potential energies,heats of formation and Tc-temperatures of order-disorder transitions of the L10-AuCu,L12-Au3Cu and L12-AuCu3 compounds,as well as the Au3Cu-,AuCu-and AuCu3-type ordered alloys with maximal ordering degrees are calculated too.The results show that the 5th E-function may be chosen for developing it into the free energy-,enthalpy-,vibrational energy-and vibrational entropy-functions for describing thermodynamic properties of the compounds,ordered and disordered phases and for establishing the phase diagram of the Au-Cu system in the future.

A Common Optical Potential for ~4He+^(12)C at Intermediate Energies

A common optical potential for 4He＋12C at intermediate bombarding energies, which is essential in analyzing exotic nuclei with 4He clusters, is obtained based on the Sao Paulo potential. Among systematic optical potentials for 4He＋12 C, this potential has the merit of using a fixed imaginary part of the Woods Saxon form. By optical- model calculations, this potential reproduces the experimental elastic scattering angular distributions of a He＋12 C well within the energy range of 26A 60A MeV. It is also applied successfully in calculations of the breakup reactions of 6Li＋12 C and 6He＋12 C with a three-body continuum discretized coupled-channel method.

Stereodynamics Study of Li+HF→LiF+H Reactions on X^2A’ Potential Energy Surface at Collision Energies below 5.00 kcal/mol

The product rotational polarizations of reaction Li-SHF→LiF-kH at different collision energies, as well as at the different vibrational states and rotational states, are calculated by using the quasi-classical trajectory method based on a new potential energy surface constructed by Aguado et al. [J. Chem. Phys. 119（2003） 10088]. We investigate the Mignment and the orientation of the product molecule by calculating the P（θr, φr） distribu- tions describing polar angle distribution, the P（θr） distributions describing the k-j＇ correlation and the P（φr） distributions describing the k-k＇-j＇ correlation. We also explore the dependence of reaction probabilities and cross sections on the rotational and vibrational quantum number of the title reaction. It is concluded that the vibrational state has more important impact on the angular distribution, reaction probability and cross section.

Momentum-Dependent Symmetry Potential from Nuclear Collective Flows in Heavy Ion Collisions at Intermediate Energies

Within the isospin-dependent quantum molecular dynamics model, we investigate the nuclear collective flows produced in semi-central 197 Au＋197 Au collisions at intermediate energies. The neutron proton differential flows and difference of neutron proton collective flows are sensitive to the momentum-dependent symmetry potential. This sensitivity is less affected by both the isoscalar part of nuclear equation of state and in-medium nucleon- nucleon cross sections. Moreover, this sensitivity becomes pronounced with increasing the rapidity cut.

Benchmarking calculations of excitation energies and transition properties with spectroscopic accuracy of highly charged ions used for the fusion plasma and astrophysical plasma

Atomic radiative data such as excitation energies, transition wavelengths, radiative rates, and level lifetimes with high precision are the essential parameters for the abundance analysis, simulation, and diagnostics in fusion and astrophysical plasmas. In this work, we mainly focus on reviewing our two projects performed in the past decade. One is about the ions with Z■30 that are generally of astrophysical interest, and the other one is about the highly charged krypton(Z = 36)and tungsten(Z = 74) ions that are relevant in research of magnetic confinement fusion. Two different and independent methods, namely, multiconfiguration Dirac–Hartree–Fock(MCDHF) and the relativistic many-body perturbation theory(RMBPT) are usually used in our studies. As a complement/extension to our previous works for highly charged tungsten ions with open M-shell and open N-shell, we also mainly focus on presenting and discussing our complete RMBPT and MCDHF calculations for the excitation energies, wavelengths, electric dipole(E1), magnetic dipole(M1), electric quadrupole(E2), and magnetic quadrupole(M2) transition properties, and level lifetimes for the lowest 148 levels belonging to the 3l3configurations in Al-like W61+. We also summarize the uncertainties of our systematical theoretical calculations, by cross-checking/validating our datasets from our RMBPT and MCDHF calculations, and by detailed comparisons with available accurate observations and other theoretical calculations. The data are openly available in Science Data Bank at https://doi.org/10.57760/sciencedb.10569.

Atomistic Modeling of Lithium Materials from Deep Learning Potential with Ab Initio Accuracy

Lithium has been paid great attention in recent years thanks to its significant appli-cations for battery and lightweight alloy.Developing a potential model with high ac-curacy and efficiency is impor-tant for theoretical simulation of lithium materials.Here,we build a deep learning potential(DP)for elemental lithium based on a concurrent-learning scheme and DP representation of the density-functional theory(DFT)potential energy surface(PES),the DP model enables material simulations with close-to DFT accuracy but at much lower computational cost.The simulations show that basic parameters,equation of states,elasticity,defects and surface are consistent with the first principles results.More notably,the liquid radial distribution func-tion based on our DP model is found to match well with experiment data.Our results demon-strate that the developed DP model can be used for the simulation of lithium materials.

From the Green's Function in Tight-Binding Representation to Interatomic Many-body Potentials

In this paper, we deduce the analytical form of many-body interatomic potentials based on the Green's function in tight-binding representation. The many-body potentials are expressed as the functions of the hopping integrals which are the physical origin of cohesion of atoms. For thesimple case of s-valent system, the inversion of the many-body potentials are discussed in detail by using the lattice inversion method.

Research on Potential Energy Recovery System of 16T Wheeled Hybrid Excavator

The system translates the arm/boom/buck's potential energy into electrical energy and then the electrical energy is stored in a storage device.This study develops a set of energy management strategy to make the recoverable energy recycling efficiently.This energy of traditional excavator is lost in the form of heat energy,which is wasteful,and makes the component's temperature higher and higher to reduce the machine's life.Research on this system not only conforms to the current topic of energy crisis,but also mates with the actual engineering,so it is significant to research that.

Accurate double many-body expansion potential energy surface of HS_2(A^2A') by scaling the external correlation

A globally accurate single-sheeted double many-body expansion potential energy surface is reported for the first excited state of HS_2 by fitting the accurate ab initio energies, which are calculated at the multireference configuration interaction level with the aug-cc-pVQZ basis set. By using the double many-body expansion-scaled external correlation method,such calculated ab initio energies are then slightly corrected by scaling their dynamical correlation. A grid of 2767 ab initio energies is used in the least-square fitting procedure with the total root-mean square deviation being 1.406 kcal · mol^（-1）.The topographical features of the HS_2（A_2A＇） global potential energy surface are examined in detail. The attributes of the stationary points are presented and compared with the corresponding ab initio results as well as experimental and other theoretical data, showing good agreement. The resulting potential energy surface of HS_2（A_2A＇） can be used as a building block for constructing the global potential energy surfaces of larger S/H molecular systems and recommended for dynamic studies on the title molecular system.

Photon Structure and Wave Function from the Vector Potential Quantization

A photon structure is advanced based on the experimental evidence and the vector potential quantization at a single photon level. It is shown that the photon is neither a point particle nor an infinite wave but behaves rather like a local “wave-corpuscle” extended over a wavelength, occupying a minimum quantization volume and guided by a non-local vector potential real wave function. The quantized vector potential oscillates over a wavelength with circular left or right polarization giving birth to orthogonal magnetic and electric fields whose amplitudes are proportional to the square of the frequency. The energy and momentum are carried by the local wave-corpuscle guided by the non-local vector potential wave function suitably normalized.

Global Potential Energy Surface for the H＋CH4←→H2＋CH3 Reaction using Neural Networks

A globla potential energy surface （PES） for the H＋CH4←→H2＋CH3 reaction has been constructed using the neural networks method based on 47783 high level ab initio geometry points. Extensive quasi-classical trajectories and quantum scattering calculations were carried out to check the convergence of the PES. This PES, fully converged with respect to the fitting procedure and the number of ab initio points, has a very small fitting error, and is much faster on evaluation than the modified Shepard interpolating PES, representing the best available PES for this benchmark polyatomic system.

Theoretical Study on Dissociation Potential Energy Surface of Peroxynitric Acid

The lowest energy structures of peroxynitric acid have been studied with B3LYP/6-311＋ G（2d,2p） method. The potential energy surfaces （PES） along the O-N and O-O bonds have been scanned at CCSD（T）/aug-cc-pVDZ level, respectively. The calculated results show that on the O-N PES, the O3-N4 bond length of the loose transition state is 2.82A^° and the corresponding energy barrier is 25.6 kcal/mol, while on the O-O PES, the loose transition state with of O2-O3 bond length of 2.35A^° has the energy barrier of 37.4 kcal/mol. Thus the primary reaction path for peroxynitric acid is the dissociation into HO2 and NO2.

Effect of Surface Potential Barrier on the Electron Energy Distribution of NEA Photocathodes

By calculating the energy distribution of electrons reaching the photocathode surface and solving the Schrodinger equation that describes the behavior of an electron tunneling through the surface potential barrier,we obtain an equation to calculate the emitted electron energy distribution of transmission-mode NEA GaAs photocathodes. Accord- ing to the equation,we study the effect of cathode surface potential barrier on the electron energy distribution and find a significant effect of the barrier-Ⅰ thickness or end height,especially the thickness,on the quantum efficiency of the cath- ode. Barrier Ⅱ has an effect on the electron energy spread, and an increase in the vacuum level will lead to a narrower electron energy spread while sacrificing a certain amount of cathode quantum efficiency. The equation is also used to fit the measured electron energy distribution curve of the transmission-mode cathode and the parameters of the surface barri- er are obtained from the fitting. The theoretical curve is in good agreement with the experimental curve.

A Global ab initio Potential Energy Surface for F+H_(2)→HF+H

A global three dimensional potential energy surface for the F＋H2→HF＋H reaction has been developed by spline interpolation of about 15,000 symmetry-unique ab initio points, obtained from the multi-reference configuration interaction level with Davidson correction using the aug-cc-pV5Z basis set. In the entrance channel the spin-orbit coupling energy is also included.

A Study on Reflection Phase Time of Particles Passing through a Potential Well

To understand the physical meaning of phase time further more, we discuss the reflection phase time of quantum-particles passing though a potential well It is shown that the reflection phase time is equal to the transmission phase time in value and negative under certain conditions for a square potential well by analyzing While quantum-particles passing through the potential well, we think that this course can be described only with the velocity of energy of quantum mechanics whether or not they are reflected or transmitted eventually