Modeling of Polymer Friction on Boundaries of Solids and Inside Materials

Friction models are proposed for anisotropic and heterogeneous dry friction on boundaries of polymer solids. Unit vectors and oriented angles of sliding velocities, radii of curvature and unit normal vectors of sliding trajectories are taken as independent variables in constitutive equations of anisotropic and heterogeneous friction. Heterogeneous dry friction of a polymer pin in pin-on-disc tests is illustrated in the case of Archimedean spiral trajectory. Individual molecular chains composing polymer materials can move inside the material with a high degree of friction anisotropy. The resistance of macromolecule motion is considered with respect to micromechanical models of macromolecules, their kinematics, and friction laws. Two approaches are applied for modeling of anisotropic friction inside polymer materials: continuum-based models (anisotropic viscous friction) and micromechanical models (anisotropic dry friction). Examples of macromolecule dry friction are considered under conditions of spinning and sliding of a disc-like macromolecule and snake-like sliding of a long macromolecule.

Control and Modification of Nanostructured Materials by Electron Beam Irradiation

I have proposed a bottom-up technology utilising irradiation with active beams, such as electrons and ions, to achieve nanostructures with a size of 3–40 nm. This can be used as a nanotechnology that provides the desired structures, materials, and phases at desired positions. Electron beam irradiation of metastable θ-Al2O3, more than 1019 e/cm2s in a transmission electron microscope (TEM), enables the production of oxide-free Al nanoparticles, which can be manipulated to undergo migration, bonding, rotation, revolution, and embedding. The manipulations are facilitated by momentum transfer from electrons to nanoparticles, which takes advantage of the spiral trajectory of the electron beam in the magnetic field of the TEM pole piece. Furthermore, onion-like fullerenes and intercalated structures on amorphous carbon films are induced through catalytic reactions. δ-, θ-Al2O3 ball/wire hybrid nanostructures were obtained in a short time using an electron irradiation flashing mode that switches between 1019 and 1022 e/cm2s. Various α-Al2O3 nanostructures, such as encapsulated nanoballs or nanorods, are also produced. In addition, the preparation or control of Pt, W, and Cu nanoparticles can be achieved by electron beam irradiation with a higher intensity.

Analytical solutions for low-thrust orbit transfers

This paper presents analytical solutions for the estimation of the $$\Delta V$$ Δ V cost of the transfer of a spacecraft subject to a low-thrust action. The equations represent an extension of solutions already available in the literature. Moreover, the paper presents novel analytical solutions for low-thrust transfers under the effect of the second-order zonal harmonics of the Earth’s gravitational potential. In particular, the paper is divided into two parts. The first part presents analytical expressions for the $$\Delta V$$ Δ V cost of transfers. All analytical equations were validated through numerical integration of the dynamics of the spacecraft. The second part of the paper introduces new analytical equations for low-thrust transfers between circular inclined orbits with different values of the right ascension of the ascending node, under the effect of the second-order zonal harmonic of the Earth’s gravitational potential. Both in the first and second parts, analytic solutions for the variation with time of the orbital elements during the transfer are presented. The proposed equations are applicable to low-thrust transfer realised through a long spiral trajectory.

Research on the Elastic Properties of Discontinuous Contact Wire Rope for WR-CVT

This study mainly conducts the research on the discontinuous contact elastic properties of wire rope based on WR-CVT. The geometry model and finite element model of continuous contact and discontinuous contact of 2/3 lay pitch wire rope are established. And the contact stress distribution of the steel wire is analyzed through 5 sections and 5 contact points. The results show that on the C-C plane, the contact stress of the discontinuous contact model is 229.4 MPa higher than that of the continuous contact, but this difference is not obvious on the D-D plane. The contact stress nephogram is elliptical, but in the noncontact area, the shape of the contact trace shows a distinct noncomplete ellipse, and the contact trace is distributed along the spiral trajectory of the steel wire. Point 4 due to the reduction in contact area, compared with continuous contact, discontinuous contact shows a higher stress value. The geometric dimensions of the wear scars of continuous contact and discontinuous contact indicate that regardless of the length of the wear scar or the width of the wear scar, the geometric characteristics of steel wire wear mark in discontinuous contact are larger than that in continuous contact, so the discontinuous contact aggravates the surface wear of wire. This research lays a theoretical foundation for the discontinuous contact wear and fatigue of WR-CVT wire rope and other components.

Analysis of Gas-Liquid-Solid Three-Phase Flows in Hydrocyclones Through a Coupled Method of VOF and DEM

Liquid-gas-solid three-phase flows in hydrocyclones are studied numerically in this paper by employing a coupled method of volume of fluid (VOF) and discrete element model (DEM) with RSM turbulence model. The numerical method is validated by comparing the calculated results to those of experiments published in literature about the separation of particle flows in hydrocyclones. Since VOF-DEM model could capture the gas-liquid interface of particle flows, the three-dimensional formation process of the air-core together with the formation of the spiral trajectory of particles are depicted for the first time. In addition, the effects of the particle concentration ? (less than 12%) on the air-core formation time Tf and diameter Da are studied systematically, which has not been reported in literature. The increase of ? has both positive and negative actions on the change of Tf and Da, and compromises of two kinds of actions generate the valley or peak of curves of Tf vs ? and Da vs ?, respectively. Moreover, the results for three hydrocyclones with different cone angles are also compared to study the effects of the cylindrical and conical section on the air-core formation and the separation performance of the hydrocyclones. By analyzing the flow fields and the pressure changes inside the hydrocyclones, qualitative explanations of the relevant discoveries are given in this paper. The results will be helpful in the investigation of the multiphase flow behaviors in the hydrocyclone and in the selection of the appropriate hydrocyclone.

Spiral-based chaotic chicken swarm optimization algorithm for parameters identification of photovoltaic models

Photovoltaic (PV) systems are becoming increasingly significant because they can convert solar energy into electricity. The conversion efficiency is related to the PV models’ parameters, so it is crucial to identify parameters of PV models. Recently, various heuristic methods have been proposed to identify the parameters, but they cannot provide sufficient accurate and reliable performance. To address this problem, this paper proposes a spiral-based chaos chicken swarm optimization algorithm (SCCSO) including three strategies: i) the information-sharing strategy provides the latest information of the roosters for searching global optimal solution, beneficial to improve the exploitation ability; ii) the spiral motion strategy can enable hens and chicks to move towards their corresponding targets with a spiral trajectory, improving the exploration ability; iii) a self-adaptive-based chaotic disturbance mechanism is introduced around the global optimal solution to generate a promising solution for the worst chick at each iteration, thereby improving the convergence speed of the chicken flock. Besides, SCCSO is used for identifying different PV models such as the single diode, the double diode, and PV module models. Comprehensive analysis and experimental results show that SCCSO provides better robustness and accuracy than other advanced heuristic methods.

Human Fundamental Upward Movement; Spiral Trajectory and Walking of 3D + 1D Space and Time

Background: There are few biomechanical studies on the physical transfer of a person lying on a floor or bed perpendicular to the direction of gravity. Basic biomechanics research can be an important source. This study aimed to analyze the biomechanical properties of the upward movement of the floor in the supine position. Methods: Healthy volunteers were recruited by snowball sampling. The movement from the supine position to upward movement on the carpet floor was repeated three times. The three procedures were analyzed with an 11 segments model using a 3D motion analysis Move Tr 3D (Library©) under the 4 CCD cameras. The analysis of the motion trace was examined. The movement of the reflection marker with respect to the Z-axis was analyzed with the vertical direction of the gravity as the Z-axis. It was observed from the XY plane, XZ plane, ZY plane, and how many dimensions the reflection marker took was analyzed. Results: Five healthy volunteers (Medium age 27 years, Female) who received written consent to the study were investigated. A spiral motion was observed in the trajectory of all reflection markers. A walking motion was observed in which the right and left sides of the body alternately swam to the back. Each reflex marker body site was moving headward as if contacting the floor with either the left or right side having 0 to the vertical Z-axis of gravity; the opposite left or right side walked with repeated movements floating from the floor and raising the Z coordinate. 3D Space + 1D time were observed in the human fundamental upward movement. Conclusion: The Human Fundamental Upward Movement on the floor was observed Spiral Trajectory and the Walking of 3D+1D Space and Time. KEYWORDS: Human Fundamental Movement, Upward movement, Positioning Change, Transfer, Biomechanics

Numerical-Experimental Study Regarding the Single Point Incremental Forming Process

The present paper proposes a numerical-experimental comparative study on the single point incremental forming process. A DC04 steel sheet with a thickness of 0.6 mm was used for both the numerical simulation using the finite element method and the experimental research. The type of trajectory used was a spiral trajectory and the finished part obtained was a truncated cone-shaped part. The analysis program used for simulation was Ls-Dyna. The simulations were performed in several variants: with a fixed mesh and with an adaptive mesh, using two different element formulations: 25 (Belytschko-Tsay formulation with thickness stretch) and -16 (fully integrated shell element modified for higher accuracy) and two contact types: automatic surface to surface (ASTS) and forming one way surface to surface (FOSS). The results of the numerical analysis and of the experimental research were focused on determining the major strain, minor strain, thickness reduction and forces at the end of the single point incremental forming process, as well as determining the processing time.

Spiral trajectories induced by radial thrust with applications to generalized sails

In this study, new analytical solutions to the equations of motion of a propelled spacecraft are investigated using a shape-based approach. There is an assumption that the spacecraft travels a two-dimensional spiral trajectory in which the orbital radius is proportional to an assigned power of the spacecraft angular coordinate. The exact solution to the equations of motion is obtained as a function of time in the case of a purely radial thrust, and the propulsive acceleration magnitude necessary for the spacecraft to track the prescribed spiral trajectory is found in a closed form. The analytical results are then specialized to the case of a generalized sail, that is, a propulsion system capable of providing an outward radial propulsive acceleration, the magnitude of which depends on a given power of the Sun-spacecraft distance. In particular, the conditions for an outward radial thrust and the required sail performance are quantified and thoroughly discussed. It is worth noting that these propulsion systems provide a purely radial thrust when their orientation is Sun-facing. This is an important advantage from an engineering point of view because, depending on the particular propulsion system, a Sun-facing attitude can be stable or obtainable in a passive way. A case study is finally presented, where the generalized sail is assumed to start the spiral trajectory from the Earth’s heliocentric orbit. The main outcome is that the required sail performance is in principle achievable on the basis of many results available in the literature.

15 Years MR-encephalography

Objective This review article gives an account of the development of the MR-encephalography (MREG) method, which started as a mere ‘Gedankenexperiment’ in 2005 and gradually developed into a method for ultrafast measurement of physiological activities in the brain. After going through different approaches covering k-space with radial, rosette, and concentric shell trajectories we have settled on a stack-of-spiral trajectory, which allows full brain coverage with (nominal) 3 mm isotropic resolution in 100 ms. The very high acceleration factor is facilitated by the near-isotropic k-space coverage, which allows high acceleration in all three spatial dimensions. Methods The methodological section covers the basic sequence design as well as recent advances in image reconstruction including the targeted reconstruction, which allows real-time feedback applications, and—most recently—the time-domain principal component reconstruction (tPCR), which applies a principal component analysis of the acquired time domain data as a sparsifying transformation to improve reconstruction speed as well as quality. Applications Although the BOLD-response is rather slow, the high speed acquisition of MREG allows separation of BOLD-effects from cardiac and breathing related pulsatility. The increased sensitivity enables direct detection of the dynamic variability of resting state networks as well as localization of single interictal events in epilepsy patients. A separate and highly intriguing application is aimed at the investigation of the glymphatic system by assessment of the spatiotemporal patterns of cardiac and breathing related pulsatility. Discussion MREG has been developed to push the speed limits of fMRI. Compared to multiband-EPI this allows considerably faster acquisition at the cost of reduced image quality and spatial resolution.