Equilibrium properties of the lattice system with SALR interaction potential on a square lattice: quasi-chemical approximation versus Monte Carlo simulation

The lattice system with competing interactions that models biological objects (colloids, ensembles of protein molecules, etc.) is considered. This system is the lattice fluid on a square lattice with attractive interaction between nearest neighbours and repulsive interaction between next-next-nearest neighbours. The geometric order parameter is introduced for describing the ordered phases in this system. The critical value of the order parameter is estimated and the phase diagram of the system is constructed. The simple quasi-chemical approximation (QChA) is proposed for the system under consideration. The data of Monte Carlo simulation of equilibrium properties of the model are compared with the results of QChA. It is shown that QChA provides reasonable semiquantitative results for the systems studied and can be used as the basis for next order approximations.Comment: 10 pages, 8 figure

Spontaneous polarisation of the neutral interface for valence asymmetric coulombic systems

In this paper, we discuss the phenomenon of a spontaneous polarisation of a neutral hard planar interface for valence asymmetric coulombic systems. Within a field theoretical description, we account for the existence of non trivial charge density and electric potential profiles. The analysis of the phenomenon shows that the effect is related to combinatorics in relation with the existence of the two independent species cations and anions. This simple and basic feature is related to the quantum mechanical properties of the system. The theoretical results are compared with numerical simulations data and are shown to be in very good agreement, which a fortiori justifies our physical interpretation.Comment: 12 pages, 11 figure

The effect of short-range interaction and correlations on the charge and electric field distribution in a model solid electrolyte

A simple lattice model of a solid electrolyte presented as a xy-slab geometry system of mobile cations on a background of energetic landscape of the host system and a compensating field of uniformly distributed anions is studied. The system is confined in the z-direction between two oppositely charged walls, which are in parallel to xy-plane. Besides the long-range Coulomb interactions appearing in the system, the short-range attractive potential between cations is considered in our study. We propose the mean field description of this model and extend it by taking into account correlation effects at short distances. Using the free energy minimization at each of z-coordinates, the corresponding set of non-linear equations for the chemical potential is derived. The set of equations was solved numerically with respect to the charge density distribution in order to calculate the cations distribution profile and the electrostatic potential in the system along z-direction under different conditions. An asymmetry of charge distribution profile with respect to the midplane of the system is observed. The effects of the short-range interactions and pair correlations on the charge and electric field distributions are demonstrated

Exact diagonalization of the Bohr Hamiltonian for rotational nuclei: Dynamical gamma softness and triaxiality

Detailed quantitative predictions are obtained for phonon and multiphonon excitations in well-deformed rotor nuclei within the geometric framework, by exact numerical diagonalization of the Bohr Hamiltonian in an SO(5) basis. Dynamical gamma deformation is found to significantly influence the predictions through its coupling to the rotational motion. Basic signatures for the onset of rigid triaxial deformation are also obtained.Comment: 17 pages, 10 figures; to be published Phys. Rev.

Effect of in-source beam shaping and laser beam oscillation on the electromechanical properties of Ni-plated steel joints for e-vehicle battery manufacturing

Laser welding is a key enabling technology that transitions toward electric mobility, producing joints with elevated electrical and mechanical properties. In the production of battery packs, cells to busbar connections are challenging due to strict tolerances and zero-fault policy. Hence, it is of great interest to investigate how beam shaping techniques may be exploited to enhance the electromechanical properties as well as to improve material processability. Industrial laser systems often provide the possibility to oscillate dynamically the beam or redistribute the power in multicore fibers. Although contemporary equipment enables elevated flexibility in terms of power redistribution, further studies are required to indicate the most adequate solution for the production of high performance batteries. Within the present investigation, both in-source beam shaping and beam oscillation techniques have been exploited to perform 0.2-0.2 mm Ni-plated steel welds in lap joint configuration, representative of typical cell to busbar connections. An experimental campaign allowed us to define process feasibility conditions where partial penetration welds could be achieved by means of in-source beam shaping. Hence, beam oscillation was explored to perform the connections. In the subset of feasible conditions, the mechanical strength was determined via tensile tests alongside electrical resistance measurements. Linear welds with a Gaussian beam profile enabled joints with the highest productivity at constant electromechanical properties. Spatter formation due to keyhole instabilities could be avoided by redistributing the emission power via multicore fibers, while dynamic oscillation did not provide significant benefits

Hand-Held Laser Welding of AISI301LN for components with aesthetic requirements: Toward the integration of machine and human intelligence

The use of Hand-Held Laser Welding (HHLW) systems in the industry has been rapidly growing in recent years as an alternative solution to conventional manual arc-based welding systems. The decreasing cost of fiber laser sources and optics has been a driving factor in enabling a wider use of HHLW systems, beyond the established advantages of laser technology with respect to arc-based systems. While the industrial use of HHLW increases, the subject matter has been studied sparingly in the scientific literature. Due to the intrinsic flexibility of the technology, HHLW systems are highly appealing for joining relatively low thickness metals (≤2 mm) in autogenous configuration in sectors where production lots present low batch and high variability. However, a critical aspect of HHLW is correlated to the operator skill, where welding velocities can vary within and between the welds affecting both their aesthetic and mechanical properties. Hence, the development of combined digital and physical approaches to support manual operations may be highly beneficial. The current study presents an open laboratory HHLW system designed for process development purposes. Beyond conventional manual welding operations, the welding torch could be arranged in different configurations. The system could be combined with a linear axis (enabling welding with stable velocity and inclination) or manually with the aid of a newly developed roller device designed to provide constant speed and inclination. First, the process was benchmarked by joining in butt weld configuration 2 mm thick AISI301LN stainless steel sheets with the linear axis. Successively, four operators with different levels of training (rookie and professional) realized welds with the system in hand-held configuration and with the mechanical roller. The weld width variability was assessed as a direct indicator for aesthetic compliance while tensile tests were allowed to determine the mechanical properties of the joint obtained with different configurations

Shedding Light on Diatom Photonics by means of Digital Holography

Diatoms are among the dominant phytoplankters in the worl's ocean, and their external silica investments, resembling artificial photonics crystal, are expected to play an active role in light manipulation. Digital holography allowed studying the interaction with light of Coscinodiscus wailesii cell wall reconstructing the light confinement inside the cell cytoplasm, condition that is hardly accessible via standard microscopy. The full characterization of the propagated beam, in terms of quantitative phase and intensity, removed a long-standing ambiguity about the origin of the light. The data were discussed in the light of living cell behavior in response to their environment

Consequences of wall stiffness for a beta-soft potential

Modifications of the infinite square well E(5) and X(5) descriptions of transitional nuclear structure are considered. The eigenproblem for a potential with linear sloped walls is solved. The consequences of the introduction of sloped walls and of a quadratic transition operator are investigated.Comment: RevTeX 4, 8 pages, as published in Phys. Rev.

A formally exact field theory for classical systems at equilibrium

We propose a formally exact statistical field theory for describing classical fluids with ingredients similar to those introduced in quantum field theory. We consider the following essential and related problems : i) how to find the correct field functional (Hamiltonian) which determines the partition function, ii) how to introduce in a field theory the equivalent of the indiscernibility of particles, iii) how to test the validity of this approach. We can use a simple Hamiltonian in which a local functional transposes, in terms of fields, the equivalent of the indiscernibility of particles. The diagrammatic expansion and the renormalization of this term is presented. This corresponds to a non standard problem in Feynman expansion and requires a careful investigation. Then a non-local term associated with an interaction pair potential is introduced in the Hamiltonian. It has been shown that there exists a mapping between this approach and the standard statistical mechanics given in terms of Mayer function expansion. We show on three properties (the chemical potential, the so-called contact theorem and the interfacial properties) that in the field theory the correlations are shifted on non usual quantities. Some perspectives of the theory are given.Comment: 20 pages, 8 figure