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This paper introduces physical models of drill string whirling and torsional vibrations and analyses the physical models in V.I. Gulyayev's three papers on drill string whirling and torsional vibrations: “V.I. Gulyayev, L.V. Shevchuk, Drill string bit whirl simulation with the use of frictional and nonholonomic models, Journal of Vibration and Acoustics 138(1) (2016) 011021”, “V.I. Gulyayev, L.V. Shevchuk, Nonholonomic dynamics of drill string bit whirling in a deep bore-hole, J Multi-body Dynamics 227(3) (2013) 234–244” and “V.I. Gulyayev, SN Hudoliy, O.V. Glushakova, Simulation of torsion relaxation auto-oscillations of drill string bit with viscous and coulombic friction moment models, J Multi-body Dynamics 225 (2011) 139–152”. This work finds that the physical models described in these three papers are clearly incorrect. Keywords: Drill string, Vibration, Lateral, Torsion, Whirl

We offer a fractonic perspective on a familiar observation - a flat sheet of paper can be folded only along a straight line if one wants to avoid the creation of additional creases or tears. Our core underlying technical result is the establishment of a duality between the theory of elastic plates and a fractonic gauge theory with a second rank symmetric electric field tensor, a scalar magnetic field, a vector charge, and a symmetric tensor current. Bending moment and momentum of the plate are dual to the electric and magnetic fields, respectively. While the flexural waves correspond to the quadratically dispersing photon of the gauge theory, a fold defect is dual to its vector charge. Crucially, the fractonic condition constrains the latter to move only along its direction, i.e., the fold's growth direction. By contrast, fracton motion in the perpendicular direction amounts to tearing the paper. © 2021 American Physical Society.

This comment is devoted to the paper "Exact solutions of nonlinear diffusion-convection-reaction equation: A Lie symmetry approach" (CNSNS, vol. 67 (2019), 253-263) in which several results are not new because were derived much earlier. Moreover, some results in the paper are incorrect or incomplete., Commun Nonlinear Sci Numer Simulat

Annotated translations from Latin of three of the Euler’s papers on celestial mechanics are presented, which fall into the category of three-body problems. The first translation deals with an exact solution of three bodies that move around the common center of mass and always line up. This is considered the first work from which the three collinear Lagrange points could be obtained. The second translation deals with motions of Sun, Earth and Moon in syzygy and Moon libration as well, where, for the first time, Euler introduces an archaic form of a Fourier sine series expansion to describe the Moon’s wagging motion. The last translation relates to a paper that was written with the goal of alleviating astronomical computations of the perturbed motion of the Moon around the Earth by the Sun, ending up with eight coupled differential equations for resolving the perturbed motion of this celestial body. Despite showing great analytical skills, Euler gave no indications on how this system of equations could be solved, which renders his efforts practically useless in the determination of the variations of the nodal line and inclination of the Moon’s orbit.

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich., This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively., The paper ‘Zur Dynamik elastisch gekoppelter Punktsysteme’ by Schrödinger (1914) does not seem to have attracted the attention that it deserves. We translate it into English here and we discuss its results in detail, with a view to its possible influence in the modern theories of generalised continua. The clever solution found, in terms of Bessel functions, by Schrödinger of the problem of the vibrations of a linear infinite chain of molecules gives some important methodological hints for contemporary research.

Many complex physical systems exhibit a rich variety of discrete behavioural modes. Often, the system complexity limits the applicability of standard modelling tools. Hence, understanding the underlying physics of different behaviours and distinguishing between them is challenging. Although traditional machine learning techniques could predict and classify behaviour well, typically they do not provide any meaningful insight into the underlying physics of the system. In this paper we present a novel method for extracting physically meaningful clusters of discrete behaviour from limited experimental observations. This method obtains a set of physically plausible functions that both facilitate behavioural clustering and aid in system understanding. We demonstrate the approach on the V-shaped falling paper system, a new falling paper type system that exhibits four distinct behavioural modes depending on a few morphological parameters. Using just 49 experimental observations, the method discovered a set of candidate functions that distinguish behaviours with an error of 2.04%, while also aiding insight into the physical phenomena driving each behaviour. © 2019 Howison et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

The cost of specialized scientific equipment can be high and with limited funding resources, researchers and students are often unable to access or purchase the ideal equipment for their projects. In the fields of materials science and mechanical engineering, fundamental equipment such as tensile testing devices can cost tens to hundreds of thousands of dollars. While a research lab often has access to a large-scale testing machine suitable for conventional samples, loading devices for meso- and micro-scale samples for in-situ testing with the myriad of microscopy tools are often hard to source and cost prohibitive. Open-source software has allowed for great strides in the reduction of costs associated with software development and open-source hardware and additive manufacturing have the potential to similarly reduce the costs of scientific equipment and increase the accessibility of scientific research. To investigate the feasibility of open-source hardware, a micro-tensile tester was designed with a freely accessible computer-aided design package and manufactured with a desktop 3D-printer and off-the-shelf components. To our knowledge this is one of the first demonstrations of a tensile tester with additively manufactured components for scientific research. The capabilities of the tensile tester were demonstrated by investigating the mechanical properties of Graphene Oxide (GO) paper and thin films. A 3D printed tensile tester was successfully used in conjunction with an atomic force microscope to provide one of the first quantitative measurements of GO thin film buckling under compression. The tensile tester was also used in conjunction with an atomic force microscope to observe the change in surface topology of a GO paper in response to increasing tensile strain. No significant change in surface topology was observed in contrast to prior hypotheses from the literature. Based on this result obtained with the new open source tensile stage we propose an alternative hypothesis we term 'superlamellae consolidation' to explain the initial deformation of GO paper. The additively manufactured tensile tester tested represents cost savings of >99% compared to commercial solutions in its class and offers simple customization. However, continued development is needed for the tensile tester presented here to approach the technical specifications achievable with commercial solutions.

The overlap separation mechanism is widely used to separate paper sheets from each other in automatic teller machines. In this study, we first derived a formula used for expressing the normal separation condition of paper sheets. Then we analyzed the deformation force acting on the paper sheet surfaces by treating the paper sheet as an elastic beam and using Clapeyron's theorem of three moments. Furthermore, by using the finite element analysis software LS-DYNA, we developed a three-dimensional simulation method that can accurately reproduce normal separation, misfeeding, and double feeding behaviors. Finally, the effects of the main parameters on deformation force will be discussed. The results show that the deformation force is proportional to the overlap; the bigger the width of gate-roller or the distance of roller edges, the bigger the deformation force. Moreover, the width of the feed-roller has hardly any effect on deformation force. It is shown that separation defects obtained by the elastic beam model agree well with those obtained by the FE model.

Immediately following the commentary below, this previously published article is reprinted in its entirety: Cathleen Synge Morawetz, “The mathematical approach to the sonic barrier”, Bull. Amer. Math. Soc. (N.S.) 6 (1982), no. 2, 127–145.

The paper is devoted to correcting structure of the representation for Rayleigh waves at non-semisimple degeneracy of the fundamental matrix. The incorrect representation was given in a paper “Implicit and explicit secular equations for Rayleigh waves in two-dimensional anisotropic media” by Cerv and Plesek (2013) .

This letter solves an open question of paper spring risen by Yoneda (2019). Universal scaling laws of a paper spring are proposed by using both dimensional analysis and data fitting. It is found that spring force obeys power square law of spring extension, however strong nonlinear to the total twist angle. Without doing any additional works, we have successfully generalize the scaling laws for Poisson ratio 0.3 to the materials with an arbitrary Poisson's ratio with the help of dimensional analysis.

We already reported on the presence of dielectrophoretic forces inside pixels of electrophoretic image displays [Displays 24 (2003) 103]. It was necessary to include these forces in internal physics to explain properties that seemed in discrepancy with theory until then. In this article we explain just how electrophoresis and dielectrophoresis work together in order to make electronic paper work. We also report on a more accurate macroscopic RC-model than the one found until now. Agreement between measurement and model improves with this new electric model.

This paper studies geometric properties of a class of irreversible dynamical systems, referred to in the literature as metriplectic systems. This class of systems, related to generalized (or dissipative) Hamiltonian systems, are generated by a conserved component and a dissipative component and appear, for example, in non-equilibrium thermodynamics. In non-equilibrium thermodynamics, the two potentials generating the dynamics are interpreted as generalized energy and generalized entropy, respectively. Stability and stabilization results for metriplectic systems have been presented in the literature, however, some aspects are still poorly understood, in particular the existence of dynamical invariants such as periodic orbits. In this note, we study the properties of metriplectic systems by considering a lift from the n-dimensional state space to a (2n+1)-dimensional contact space, following an approach introduced in recent years to study irreversible control systems. This lift leads to a deeper geometric characterization of metriplectic systems in the extended space. An example is provided to illustrate the approach proposed in this paper.

Canonical solutions to frequency domain Maxwell’s equations, in the spherical coordinate system, have found extensive use as is evident from citations in the scientific literature. What is conspicuous by its absence is lack of such expressions for transient Maxwell systems. The existence of such expressions or approximations, provide the means to glean interesting physics in a variety of applications as well as validate existing numerical fullwave solvers. However, developing these expressions is beset with challenges; direct inverse Fourier transforms of frequency domain expressions are unstable. Successful approaches that ameliorate this instability are more recent endeavor. In this paper, we generalize our earlier contribution to this effort by exploiting a novel representation of the retarded potential to derive expressions for scattering from a dielectric sphere. Several results are provided that demonstrate the stability and accuracy of the method.

The comments on the recently published paper by M. Gnaneswara Reddy are presented. It is shown that the similarity transformations made in the paper are not correct.

In this paper we consider the control of a dynamically asymmetric balanced ball on a plane in the case of slipping at the contact point. Necessary conditions under which a control is possible are obtained. Specific algorithms of control along a given trajectory are constructed.

We report tensile failure experiments on paper sheets. The acoustic emission energy and the waiting times between acoustic events follow power-law distributions. This remains true while the strain rate is varied by more than two orders of magnitude. The energy statistics has the exponent $\beta \sim 1.25 \pm 0.10$ and the waiting times the exponent $\tau \sim 1.0 \pm 0.1$, in particular for the energy roughly independent of the strain rate. These results do not compare well with fracture models, for (brittle) disordered media, which as such exhibit criticality. One reason may be residual stresses, neglected in most theories., Comment: 4 pages, 5 figures

A novel hybrid simulation based on the coupled Maxwell-Schrodinger equations has been utilized to investigate, accurately, the dynamics of electron conflned in a one-dimensional potential and subjected to time-dependent electromagnetic flelds. A detailed comparison has been made for the computational results between the Maxwell-Schrodinger and conventional Maxwell-Newton approaches, for two distinct cases, namely, characterized by harmonic and anharmonic electrostatic conflning potentials. The results obtained by the two approaches agree very well for the harmonic potential while disagree quantitatively for the anharmonic potential. This clearly indicates that the Maxwell- Schrodinger scheme is indispensable to multi-physics simulation particularly when the anharmonicity efiect plays an essential role.

In a recent paper, published in Astrophys. Space Sci. (337:107, 2012) (hereafter paper ZZX) and entitled “On the triangular libration points in photogravitational restricted three-body problem with variable mass”, the authors study the location and stability of the generalized Lagrange libration points L 4 and L 5. However their study is flawed in two aspects. First they fail to write correctly the equations of motion of the variable mass problem. Second they attribute a variable mass to the third body of the restricted three-body model, a fact that is not compatible with the assumptions used in deriving the mathematical formulation of this model.

Submitted by Isabel Melo (imelo@sa.isel.pt) on 2019-09-12T08:22:47Z No. of bitstreams: 1 Oscillations_VOliveira.pdf: 1092601 bytes, checksum: 9142fdb3f2e0b9683a61a5562d028892 (MD5) Made available in DSpace on 2019-09-12T08:22:47Z (GMT). No. of bitstreams: 1 Oscillations_VOliveira.pdf: 1092601 bytes, checksum: 9142fdb3f2e0b9683a61a5562d028892 (MD5) Previous issue date: 2019-08-23 info:eu-repo/semantics/publishedVersion

In Benjamin Franklin’s one fluid theory of electrification, ordinary unelectrified matter consisted of a matrix of matter suffused with a certain amount of “electrical fluid.” Electrical effects were due to an excess or deficit of electrical fluid, hence the terms positive and negative. Before the development of a modern view of the atom, diagrams showing charged objects would simply have “+” or “–” signs to indicate the charged state. As physicists we know how to interpret these diagrams and understand what they are telling us about the underlying atomic model of charging. However, novice students may not readily make the connection between the atomic model, in which a charged solid object either gains or loses electrons but does not gain or lose positive charges. Furthermore, when isolated objects become charged, the total number of electrons must be accounted for as charge is a conserved quantity. To really understand the changes that occur in charging by contact, conduction, or induction, it is useful...

This paper considers the problem of controlling the rotational motion of an axi-symmetric rigid body using two independent control torques without angular velocity measurements. The control law which stabilizes asymptotically this motion is obtained only in terms of the orientation parameters. Global asymptotic stability is shown by applying LaSalle invariance principal. Numerical simulation is introduced.

In this paper it is shown that the well known special orthotropy of paper, explained by micromechanical models of complex bodies, actually corresponds to a special case of orthotropy of a plane elastic body. The existence of this special orthotropy was predicted by the author in a previous work.

Replies are made to comments in N N Rozanov's letter to the editors "Can even monochromatic radiation ensure ideal invisibility?" (see Usp. Fiz. Nauk 181 787 (2011) [Phys. Usp. 54 763 (2011)]) concerning our paper "Invisible cloaking of material bodies using the wave flow method" (Usp. Fiz. Nauk 180 475 (2010) [Phys. Usp. 53 455 (2010)]). Examples are given of spatial configurations that enable the creation of singularity-free cloaking materials. Some emerging cloaking ideas are discussed.

The present comment concerns some doubtful results included in the above papers.

In this paper, a finite element procedure is used to study the dynamic behaviour of a paper web in a free span between two rollers, including effects of transport velocity and surrounding air. The paper web is modelled as a three-dimensional orthotropic structure. The influence of air is accounted for by utilizing fluid-solid interaction analyses based on acoustic theory. The contribution of transport velocity is included through gyroscopic matrices and forces. The structural response on harmonic excitations has been studied using linear and non-linear models. Results show that air significantly reduces eigenfrequencies of the web. So called ''edge-flutter'' is nothing but the result of skew tension profile. Excessive web vibration can be eliminated by adjusting the web tension.

Cyclohexene molecule possesses two low frequency modes assigned to the ring-twisting and ring-bending vibrations. In this paper, the ab initio potential energy associated with these vibrations is calculated at the MP2 level by varying a single internal variable (namely a dihedral angle of the molecule), by steps of two degrees. Calculation of the molecular dipole moment variation during the vibration and numerical integration of the equation of motion lead to infrared spectra in fairly good agreement with experimental ones. Potentials fitting the experimental spectra are presented and the comparison between calculated and fitted potentials is discussed.

It is shown that, for a tokamak in the cylindrical approximation, the variational problem in the paper by Yu.N. Dnestrovskij et al. “Variational Problems for the Canonical Profiles” is formulated not quite correctly. As a result, it is unfortunately impossible to link canonical profiles to the minimum of the magnetic energy of the plasma current.

The purpose of this brief paper is to present a new derivation of Biot's theory of linear poroelasticity (Biot, M., 1935, “Le Probleḿe de la Consolidation des Matiéres Argileuses Sous une Charge,” Ann. Soc. Sci. Bruxelles,B55, pp. 110–113; Biot, M., 1941, “General Theory of Three-Dimensional Consolidation,” J. Appl. Phys., 12, pp. 155–164; and Biot, M., and Willis, D., 1957, “The Elastic Coefficients of the Theory of Consolidation,” J. Appl. Mech., 24, pp. 594–601) in a modern thermodynamically consistent fashion, and show that it may be deduced as a special case of a more general theory of chemoelasticity., National Institutes of Health (U.S.). Civil, Mechanical and Manufacturing Innovation (Award 1063626), Center for Clean Water and Clean Energy at MIT and KFUPM

In a recent paper by Zinoviev and Bies in this Journal, the authors have claimed that the well-known theoretical results of Curle and Ffowcs Williams and Hawkings (FW-H) are incorrect. This claim is categorically refuted below and serious errors are pointed out.

Some paradoxes are discussed concerning the interpretation of the passage of particles and electromagnetic waves (pulses) across potential barriers and through nonuniform media, in particular, those with frequency dispersion and therefore dissipation. It is emphasized that a rigorous nonstationary approach does not entail any supraluminal velocities for the transfer of physical substances, although supraluminal velocities are indeed possible for several kinematically defined velocities, e.g., for the group velocity.

The frictional phenomena appear in various systems. Their scales spread to extraordinary wide range. The frictional systems of large scale extend to landslide, glacier and earthquake, while those of small scale reach to sub-nanometer. There are universal behaviors in friction which are independent from the scale of the system. Typical examples are the maximum static frictional force, which is the threshold strength of the external force to cause the translational motion, and the kinetic frictional force, which results from energy dissipation accompanied by the caused motion. Besides these, stick-slip phenomena, memory effect of static frictional force, velocity dependence of kinetic frictional force and so on appear in various systems with wide range of scale. There are common mechanisms in these universal phenomena. Here we review frictional phenomena of various systems from a unified point of view.