Full Solution Research Articles

Transporting Particles with Vortex Rings

Due to their long-lived nature, vortex rings are highly promising for the non-contact transportation of colloidal microparticles. However, because of the high complexity of the structures, their description using rigorous, closed-form mathematical expressions is challenging, particularly in the presence of strongly inhomogeneous colloidal suspensions. In this work, we comprehensively study this phenomenon, placing special emphasis on a quantitative description of the ability of vortex rings to move the particles suspended in a liquid over distances significantly exceeding the ring’s dimensions. Moreover, within the study, we present straightforward analytical approximations extracted by using the fitting of the experimental and numerical simulation observations that reveal the dynamics of vortex rings transporting the microparticles. It includes both the dependence of the concentration on the distance traveled by the vortex ring and coefficients describing the evolution of vortex ring shape in time, which were not presented in the literature before. It turns out that despite the fact that 2D modeling is a simplification of the full 3D problem solution and is unable to capture some of the minor effects of real behavior, it has demonstrated a good consistency with the results obtained via experiments regarding the process of particles transportation.

Neural Packing: from Visual Sensing to Reinforcement Learning

We present a novel learning framework to solve the transport-and-packing (TAP) problem in 3D. It constitutes a full solution pipeline from partial observations of input objects via RGBD sensing and recognition to final box placement, via robotic motion planning, to arrive at a compact packing in a target container. The technical core of our method is a neural network for TAP, trained via reinforcement learning (RL), to solve the NP-hard combinatorial optimization problem. Our network simultaneously selects an object to pack and determines the final packing location, based on a judicious encoding of the continuously evolving states of partially observed source objects and available spaces in the target container, using separate encoders both enabled with attention mechanisms. The encoded feature vectors are employed to compute the matching scores and feasibility masks of different pairings of box selection and available space configuration for packing strategy optimization. Extensive experiments, including ablation studies and physical packing execution by a real robot (Universal Robot UR5e), are conducted to evaluate our method in terms of its design choices, scalability, generalizability, and comparisons to baselines, including the most recent RL-based TAP solution. We also contribute the first benchmark for TAP which covers a variety of input settings and difficulty levels.

New variable separation solutions and localized waves for (2+1)-dimensional nonlinear systems by a full variable separation approach

A full variable separation approach is firstly proposed for (2+1)-dimensional nonlinear systems by extending the well-established multilinear variable separation approach through the assumption that the expansion function is composed of full variable separated functions, namely, functions with respect to only one spacial or temporal argument. Taking the (2+1)-dimensional Boiti-Leon-Manna-Pempinelli equation, the Nizhnik-Novikov-Veselov equation and the dispersive long wave equation as examples, new full variable separation solutions are obtained with several arbitrary one dimensional functions. Especially, a common formula for some suitable physical quantities is discovered. By taking the arbitrary functions in different explicit expressions, the solutions can be used to describe plentiful novel nonlinear localized waves, which might be non-travelling waves as the spacial and temporal variables are fully separated into different functions. In particular, some new hybrid solitary waves, which can pulsate periodically, appear and/or decay with an adjustable lifetime, are discovered through the on-site interactions between a doubly periodic wave and a ring soliton, a four-humped dromion and a four-humped lump, and a doubly periodic wave and a cross type solitary wave. Nonlinear wave structures and their dynamical behaviours are discussed and graphically displayed in detail.

How CPS and Autonomous Robots are Integrated to other I4.0 Technologies: a systematic literature review

ABSTRACT Industry 4.0 (I4.0) brings a set of challenges that need to be settled to enable the expected industrial revolution. Cyber-Physical Systems (CPS) and Autonomous Robots are two of mainstream I4.0 technologies and can be combined with other Enabling Technologies to overcome main I4.0 challenges. This Systematic Literature Review (SLR) aimed to understand how these Enabling Technologies were combined with CPS and Autonomous Robots to achieve fully featured I4.0 solutions. The 5C is a CPS architecture which was used as a measurement to CPS compliance. After filtering and processing 15,144 papers from six different academic search engines, it was found that full 5C compliant solutions are rare to find; that not all enabling technologies were integrated; and most of existing research focused in implementing practical solutions, but comparison to conventional approaches is scarce. We conclude that there is a need for further research to accomplish full 5C I4.0.

PC-ILP: A Fast and Intuitive Method to Place Electric Vehicle Charging Stations in Smart Cities

The widespread use of electric vehicles necessitates meticulous planning for the placement of charging stations (CSs) in already crowded cities so that they can efficiently meet the charging demand while adhering to various real-world constraints such as the total budget, queuing time, electrical regulations, etc. Many classical and metaheuristic-based approaches provide good solutions, but they are not intuitive, and they do not scale well for large cities and complex constraints. Many classical solution techniques often require prohibitive amounts of memory and their solutions are not easily explainable. We analyzed the layouts of the 50 most populous cities of the world and observed that any city can be represented as a composition of five basic primitive shapes (stretched to different extents). Based on this insight, we use results from classical topology to design a new charging station placement algorithm. The first step is a topological clustering algorithm to partition a large city into small clusters and then use precomputed solutions for each basic shape to arrive at a solution for each cluster. These cluster-level solutions are very intuitive and explainable. Then, the next step is to combine the small solutions to arrive at a full solution to the problem. Here, we use a surrogate function and repair-based technique to fix any resultant constraint violations (after all the solutions are combined). The third step is optional, where we show that the second step can be extended to incorporate complex constraints and secondary objective functions. Along with creating a full software suite, we perform an extensive evaluation of the top 50 cities and demonstrate that our method is not only 30 times faster but its solution quality is also 36.62% better than the gold standard in this area—an integer linear programming (ILP) approach with a practical timeout limit.

PEREGRINATIONS ON THE STUDY OF THE OPTICAL PROPERTIES OF NONSPHERICAL PARTICLES

PEREGRINATIONS ON THE STUDY OF THE OPTICAL PROPERTIES OF NONSPHERICAL PARTICLES

Shape models and spin states of Jupiter Trojans

The leading theory for the origin of Jupiter Trojans (JTs) assumes that JTs were captured to their orbits near the Lagrangian points of Jupiter during the early reconfiguration of the giant planets. The natural source region for the majority of JTs would then be the population of planetesimals born in a massive trans-Neptunian disk. If true, JTs represent the most accessible stable population of small Solar System bodies that formed in the outer regions of the Solar System. For this work, we compiled photometric datasets for about 1000 JTs and applied the convex inversion technique in order to assess their shapes and spin states. We obtained full solutions for 79 JTs, and partial solutions for an additional 31 JTs. We found that the observed distribution of the pole obliquities of JTs is broadly consistent with expectations from the streaming instability, which is the leading mechanism for the formation of planetesimals in the trans-Neptunian disk. The observed JTs’ pole distribution has a slightly smaller prograde vs. retrograde asymmetry (excess of obliquities >130°) than what is expected from the existing streaming instability simulations. However, this discrepancy can be plausibly reconciled by the effects of the post-formation collisional activity. Our numerical simulations of the post-capture spin evolution indicate that the JTs’ pole distribution is not significantly affected by dynamical processes such as the eccentricity excitation in resonances, close encounters with planets, or the effects of nongravitational forces. However, a few JTs exhibit large latitude variations of the rotation pole and may even temporarily transition between prograde- and retrograde-rotating categories.

Against Quantitative Primitivism

Abstract The problem of quantity is the problem of identifying what about the physical world explains why it can be so well represented with mathematical entities. I introduce “quantitative primitivism,” the dominant position in the literature, which offers only a partial solution to the problem of quantity. I argue that a reductive account of quantitativeness provides a full solution to the problem and describe two reductive accounts in the literature. I discuss some of the unique metaphysical consequences of reductive accounts of quantity, including a novel dissolution to the long-standing absolutist–comparativist debate.

An Investigation on the Teeth Crowning Effects on the Transient EHL Performance of Large-Scale Wind Turbine Spur Gears

Crowning is applied to wind turbine gears, including spur gears, to ensure adequate stress distribution and contact localization in wind turbine main gearbox gears to improve the gear performance in the presence of misalignments. Each gear tooth is crowned along the face width using a parabolic curve that graduates from a maximum height at the edges and vanishes at the center of the tooth flank. This crowning transfers the elastohydrodynamic contact problem from a line to a point contact case where the surface curvatures and pressure gradient are considered in both directions of the solution space. A wide range of longitudinal crowning heights is considered in this analysis under heavily loaded teeth for typical large-scale wind turbine gears. Furthermore, the variation in the velocities is considered in the analysis. The full transient elastohydrodynamic point contact solution considers the non-Newtonian oil behavior, where the numerical solution is based on the finite difference method. This work is focused on the evaluation of the effectiveness of teeth’s longitudinal crowning in terms of the consequences on the resulting pressure distribution and the corresponding film thickness. The modification of the tooth flank significantly elevates the film thickness levels over the zones close to the tooth edges without a significant increase in the pressure values. Moreover, the zone close to the tooth edges from both sides, where the pressure is expected to drop to the ambient pressure, is extended as a result of the flank modification.

Stability of coherent-solitonic states for Gross-Pitaevskii equation with parabolic potential

We investigate analytically and numerically the linear stability of coherent-solitonic states of the Gross-Pitaevskii equation with parabolic potential. The two lowest-order states are linearly stable. For small enough nonlinearity, either positive or negative, higher states with low intensity develop a limited number of unstable perturbation modes. When the state intensity is raised above a threshold, its stabilization occurs. The full numerical solution of the Gross-Pitaevskii equation confirms that the linear analysis gives an adequate description of solution stability properties for low-order states and moderate propagation lengths.

Flow and deformation due to periodic loading in a soft porous material

Soft porous materials, such as biological tissues and soils, are exposed to periodic deformations in a variety of natural and industrial contexts. The detailed flow and mechanics of these deformations have not yet been systematically investigated. Here, we fill this gap by identifying and exploring the complete parameter space associated with periodic deformations in the context of a one-dimensional model problem. We use large-deformation poroelasticity to consider a wide range of loading periods and amplitudes. We identify two distinct mechanical regimes, distinguished by whether the loading period is slow or fast relative to the characteristic poroelastic timescale. We develop analytical solutions for slow loading at any amplitude and for infinitesimal amplitude at any period. We use these analytical solutions and a full numerical solution to explore the localisation of the deformation near the permeable boundary as the period decreases and the emergence of nonlinear effects as the amplitude increases. We show that large deformations lead to asymmetry between the loading and unloading phases of each cycle in terms of the distributions of porosity and fluid flux.

Model discovery of compartmental models with Graph-Supported Neural Networks

In this proposal, our objective is to create a neural network for the discovery of models using compartmental models as systems of Ordinary Differential Equations (ODEs), employing Graph-Supported Neural Networks (GSNN). We design the GSNN as a graph of transition functions of the structure of the model to ensure that the three properties of the ODE solution are satisfied: additivity to one, positivity, and boundness. Rather than directly estimating the solution, these neural networks approximate the transition functions. We present theoretical evidence substantiating that our GSNN maintains these properties, along with approximation outcomes from both simulated and real-world data. These outcomes demonstrate that our GSNN outperforms the non-graph-supported approach for these issues, with instances where it even surpasses full model-based solutions and Recurrent Neural Networks. Furthermore, an evolutionary algorithm successfully generated a consistent model using the data, offering a comprehensive framework for neural network-based model discovery in these scenarios.

Peculiarities of beta functions in sigma models

In this paper we consider perturbation theory in generic two-dimensional sigma models in the so-called first-order formalism, using the coordinate regularization approach. Our goal is to analyze the first-order formalism in application to β functions and compare its results with the standard geometric calculations. Already in the second loop, we observe deviations from the geometric results that cannot be explained by the regularization/renormalization scheme choices. Moreover, in certain cases the first-order calculations produce results that are not symmetric under the classical diffeomorphisms of the target space. Although we could not present the full solution to this remarkable phenomenon, we found some indirect arguments indicating that an anomaly similar to that established in supersymmetric Yang-Mills theory might manifest itself starting from the second loop. We discuss why the difference between two answers might be an infrared effect, similar to that in β functions in supersymmetric Yang-Mills theories.In addition to the generic Kähler target spaces we discuss in detail the so-called Lie-algebraic sigma models. In particular, this is the case when the perturbed field Gij¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {G}^{i\\overline{j}} $$\\end{document} is a product of the holomorphic and antiholomorphic currents satisfying two-dimensional current algebra.

Single-crystal quality data from polycrystalline samples: finding the needle in the haystack.

Multi-grain crystallography, traditionally performed at synchrotron sources in association with high-pressure studies, has new relevance with respect to laboratory single-crystal X-ray diffraction, in which crystals can be grown rapidly in situ, and a preliminary dataset analysed and solved in a matter of minutes. Subsequently, a full-sphere of IUCr-quality data can then be collected in a few hours. To demonstrate the applicability of laboratory multi-grain crystallography with Cu Kα X-rays, co-crystals of hexafluorobenzene and pyrrole were grown rapidly by cooling a 1:1 liquid mixture in an X-ray capillary on the diffractometer. The software is able to identify a single unit cell from as few as 10% of the diffraction spots from a small number of diffraction frames. Once a unit cell is identified, a full crystal structure solution is rapidly obtained by collecting a small amount of data to a resolution of ca 1 Å. The co-crystal obtained from the 1:1 mixture showed that hexafluorobenzene and pyrrole crystallize in a 3:4 ratio, in contrast to the columnar 1:1 adduct structures typified by hexafluorobenzene and benzene. The generality of our multi-grain approach for samples that are liquid at room temperature (and form a polycrystalline solid mass on cooling) is further demonstrated by investigating and solving the 1:1 co-crystal formed between hexafluorobenzene and pyridine.

Exact thermal fracture analysis of multiferroic composites weakened by a crack containing medium

The purpose of the present work is to study the thermal fracture behaviors of multiferroic composites weakened by a propagating tangential crack containing a medium. The thermally, magnetically and (or) electrically impermeable/permeable crack models in the static state are the special cases of the present dynamic, partially permeable one. The heat conduction equation and magneto-electro-elastic governing equations with boundary conditions are converted analytically into singular integral equations which are solved exactly to yield the full plane solutions. Three cases of the eigenvalue properties are considered depending on material properties. Based on those solutions, various loadings generated by the crack interior are determined. Numerical experiments are conducted, which show that the thermal fracture behaviors depend on the magnetic, electric and elastic properties of the crack interior as well as the external loadings and inherent material properties characterized by the crack moving velocity.

Generalized filtered lifting line theory for arbitrary chord lengths and application to wind turbine blades

AbstractThe filtered lifting line theory is an analytical approach used to solve the equations of flow subjected to body forces with a Gaussian distribution, such as used in the actuator line model. In the original formulation, the changes in chord length along the blade were assumed to be small. This assumption can lead to errors in the induced velocities predicted by the theory compared to full solutions of the equations. In this work, we revisit the original derivation and provide a more general formulation that can account for significant changes in chord along the blade. The revised formulation can be applied to wings with significant changes in chord along the span, such as wind turbine blades.

Tabulated chemistry method for fast calculations of detailed chemical kinetics in system level simulations of internal combustion engines

To reduce the emissions from internal combustion engines, new combustion strategies along with alternate fuels blends are currently under investigation. The engine performance and emissions depend primarily on the chemical reactions occurring inside the engine. However, the modeling of reactions in engine simulation models using a detailed reaction mechanism is computationally very expensive, especially for very large mechanisms. Hence, a tabulated chemistry solver is developed in this work to reduce the computational time. The thermochemical states of the mixture are pre-calculated at different engine operating conditions based on homogeneous reactor simulations and stored in a lookup table which can be interpolated during the engine simulations. The present work introduces a novel method for thermochemical mapping between detailed chemistry and tabulated chemistry along with automatic identification of important intermediate species during table generation. The evolution of the thermochemical state of the mixture is described using a progress variable and its derivative. Different progress variables are investigated, and a novel formulation is proposed. The method is then applied to predict the reactions and knock phenomenon as well as the emissions in spark-ignited engines. The results using the tabulated chemistry are in good agreement with the detailed chemistry. The crank angle at the knock onset is predicted with a root-mean-squared error of 0.6 degrees crank angle. The cylinder pressure and temperature are in excellent agreement with the full detailed chemistry solution. The concentration of emissions (CO, NOx etc.) are also in good agreement for a wide range of engine operating conditions. The tabulated chemistry method provided a speedup of ~750 times as compared to detailed chemistry for a mechanism with 679 species. The computational time of the tabulated chemistry method remains constant and independent of the mechanism size. The method can be applied to large parametric studies for engine design, optimization, and calibration.

A coupled damped harmonic oscillator model for arbitrary arrays of floating cylinders using homotopy methods

A coupled damped harmonic oscillator model is derived for the long-time motion of an array of floating cylinders moving in heave, forced by a prescribed initial displacement. Eigenmodes of the coupled damped harmonic oscillator model are set to be the complex resonances of the corresponding linear potential theory model of the array. Thus, the solution of the coupled damped harmonic oscillator model has the same form as the singularity expansion method. The derivation of the coupled damped harmonic oscillator model is underpinned by a homotopy method to calculate the complex resonances for arbitrary arrays. A recursive homotopy method is used to study the complex resonances as one of the geometrical parameters is varied. The coupled damped harmonic oscillator model is shown to give accurate approximations of the full linear solutions, except for exceptional cases in which additional complex resonances appear.

A novel and computationally efficient subgrid technique for modeling scattering and Doppler effects of rough dynamic sea surfaces using the finite-difference time-domain method

Over the last decade, the improvements in computational performance that multiprocessing, solid-state hard drives, and fast memories have brought to desktop workstations have made modeling and simulation methods that were previously inaccessible into the office workspace. These methods were previously restricted to large servers or computer clusters because of their demanding computation and large memory requirements when applied to underwater acoustic simulation scenarios. One such method is the Finite-difference Time-domain (FDTD) technique. The FDTD method is a discrete numeric model that provides the full pressure wave solution solved directly in the time domain. This makes it an ideal model for investigating scattering and Doppler effects of boundaries with complex geometries and motion. A fully developed sea surface generated using the Pierson–Moskowitz wavenumber spectra meets these criteria. A novel subgrid technique has been developed to improve the accuracy of signals scattered from fully developed sea surfaces. This method remains computationally efficient because the subgrid is applied only along the rough sea surface as it varies over time. The FDTD subgrid method has been applied to simulations that investigate the “frozen” sea surface assumption that is utilized by other traditional models that incorporate boundary motion.

Improved optimisation method considering full solution space for disassembly line balancing problem in remanufacturing system

Disassembly is a key process towards waste recycling. The disassembly line balancing problem (DLBP) is a hot topic in achieving efficient disassembly. However, the existing decoding approaches cannot provide the best disassembly plans because solution spaces were reduced when solving the DLBP. To provide efficient recycling schemes for decision-makers, this study designed stochastic and partial stochastic decoding approaches searching the full solution space for four classical layouts: straight DLBP (SDLBP), U-shaped DLBP (UDLBP), two-sided DLBP (TDLBP), and parallel DLBP (PDLBP). In addition, this study constructed four mixed-integer programming (MIP) models considering both adjacent task constraints and tool switching constraints between adjacent tasks and between the first and final tasks of adjacent cycle times, optimising the number of workstations, idle time balancing index, number of tool switches, and energy consumption for the SDLBP, UDLBP, TDLBP, and PDLBP. Then, the MIP models as well as the stochastic, partial stochastic, and original decoding approaches were applied to solve four disassembly layouts. Finally, the comparison results show that the designed decoding approaches have superior solution performances and can recycle waste products more efficiently than existing methods. In addition, three heuristic algorithms, the NSGA-Ⅱ, the artificial fish swarm algorithm, and the differential evolution algorithm, combined with the designed partial stochastic decoding approach and have excellent solving performance, were applied to optimise a waste printer industrial case. Then, the optimisation results in obtaining balanced operation schemes for each objective.