scholarly journals Constraints on Newtonian Interplanetary Point-Mass Interactions in Multicomponent Systems from the Symmetry of Their Cycles

Symmetry ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 846
Author(s):  
Anne M. Hofmeister ◽  
Everett M. Criss
Keyword(s):  
Numerical Models ◽  
Point Mass ◽  
Keplerian Orbit ◽  
Transient Time ◽  
Elliptical Ring ◽  
Orbit Eccentricity ◽  
Tangential Forces ◽  
Radial Forces ◽  
Conservation Principles ◽  
Central Forces

Interplanetary interactions are the largest forces in our Solar System that disturb the planets from their elliptical orbits around the Sun, yet are weak (<10−3 Solar). Currently, these perturbations are computed in pairs using Hill’s model for steady-state, central forces between one circular and one elliptical ring of mass. However, forces between rings are not central. To represent interplanetary interactions, which are transient, time-dependent, and cyclical, we build upon Newton’s model of interacting point-mass pairs, focusing on circular orbits of the eight largest bodies. To probe general and evolutionary behavior, we present analytical and numerical models of the interplanetary forces and torques generated during the planetary interaction cycles. From symmetry, over a planetary interaction cycle, radial forces dominate while tangential forces average to zero. Our calculations show that orbital perturbations require millennia to quantify, but observations are only over ~165 years. Furthermore, these observations are compromised because they are predominantly made from Earth, whose geocenter occupies a complex, non-Keplerian orbit. Eccentricity and inclination data are reliable and suggest that interplanetary interactions have drawn orbital planes together while elongating the orbits of the two smallest planets. This finding is consistent with conservation principles governing the eight planets, which formed as a system and evolve as a system.

Modelling of Magnetic Pull in Large Size Generator

2005 ◽  
Author(s):  
Paolo Pennacchi ◽  
Lucia Frosini
Keyword(s):  
Realistic Model ◽  
Dynamical Behaviour ◽  
Air Gap ◽  
Electrical Machines ◽  
Rolling Bearings ◽  
Actual Distribution ◽  
Large Size ◽  
Original Contribution ◽  
Tangential Forces ◽  
Radial Forces

This paper presents a method to analyze the dynamical behaviour of large size generators due to the magnetic pull. In rotating electrical machines, the electromagnetic radial forces acting upon rotor and stator surfaces are very large, but they are balanced when the rotor is concentric with the stator. Similarly, the tangential forces produce only an axially rotating moment. If the rotor becomes eccentric, then an imbalance of these forces occurs, so that a net radial electromagnetic force, known as Unbalanced Magnetic Pull (UMP), is developed. The models traditionally proposed in the literature to study the UMP can be considered as reliable in case of small size electrical machines supported by rolling bearings. On the contrary, in case of large size machines, such as turbo-generators supported by oil-film bearings, the approximation of circular orbits of the rotor is not acceptable. Nevertheless, the authors who have dealt with UMP in big size generators have disregarded that these rotor filtered orbits are elliptical and generally the orbit centres are not concentric with the stator. In order to provide a more realistic model and an original contribution, in this work the actual distribution of the air-gap length during the rotation will be determined in analytical terms, by taking into account the effects produced by the actual rotor orbit. The actual UMP is calculated by using the air-gap permeance approach and the simulation of the dynamical behaviour of a 320 MW generator is presented, showing the harmonic content of the UMP and the presence of non-linearities.

Analysis of Helical Torsion Spring for Epicyclic Traction Drive

2017 ◽  
Vol 261 ◽  
pp. 408-415
Author(s):  
Geza Nemeth
Keyword(s):  
Cross Section ◽  
Rectangular Cross Section ◽  
Bending Moment ◽  
Initial Shape ◽  
Traction Drive ◽  
Torsion Spring ◽  
Spring Wire ◽  
Tangential Forces ◽  
Radial Forces ◽  
Proper Operation

Let us consider a simple epicyclic traction drive containing a sun wheel, an annular wheel, planetary wheels and a planet carrier. The annular wheel is substituted by a helical torsion spring with rectangular cross section. The spring has initial tensioning, tightened to the planetary wheels. When the number of coils is z and the number of planet wheels is N, there are zN piece of concentrated forces acting to the spring from inside towards outside. The main load of the spring is bending, it is computable along the spring wire. The bending moment is limited by the spring material and the cross section of spring. The radial forces acting to the spring are governed by the constraint of stress equality, the deflections of the contacting parts are determined by the radial (and slightly the tangential) forces. An initial shape of the spring that assures the proper operation of the drive after the assembly, is calculated by elementary mechanical calculation methods. The main goal is the developing of a traction drive in which the clamping force is proportional to the torque which should be transmitted, for the sake of the favourable life rating and the efficiency.

scholarly journals Concept and application of relaxing radial retinectomy for retinal detachment with advanced proliferative vitreo-retinopathy

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Waldensius Girsang ◽  
Dwi C. R. Sari ◽  
Wahyu Srigutomo ◽  
Tjahjono D. Gondhowiardjo ◽  
Muhammad B. Sasongko
Keyword(s):  
Retinal Detachment ◽  
English Language ◽  
Adhesion Force ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Theoretical Background ◽  
Mechanical Forces ◽  
Tangential Forces ◽  
Radial Forces ◽  
Cutting Pattern

Abstract Purpose To revisit the concept of retinectomy and the theory of mechanical forces on the retina occurring in rhegmatogenous retinal detachment (RRD) and to describe the potential application of radial retinectomy in RRD with advanced proliferative vitreoretinopathy (PVR). Methods A literature search was performed to identify all English language articles reporting the use of retinectomy for the management of RRD with PVR. We reviewed the theoretical background of mechanical forces occurring in RRD. Results Detachment of the retina from the retinal pigment epithelium (RPE)/choroid is influenced by disequilibrium of several physical forces: tangential forces on the epiretinal membrane $$\left( {T_{1} } \right)$$ T 1 and radial traction on the retina $$F_{R}$$ F R exceeding the retinal adhesion force to the RPE $$\left( {T_{1} \;\text{ + }F_{R} \;\text{ > }\;F_{A} } \right)\,\,$$ T 1 + F R > F A . PVR may exaggerate the amounts of tangential and radial forces ($$\left( {T_{1} } \right)$$ T 1 and $$F_{R}$$ F R ) that pull the retina off. Relaxing radial retinectomy, by the nature of its cutting pattern, may theoretically decrease the amounts of both forces, therefore restoring the equilibrium between tensile and adhesive forces on the retinal surface $$\left( {T_{1} \;\text{ + }F_{R} \;\text{ = }\;F_{A} } \right)\,\,$$ T 1 + F R = F A . Conclusion Relaxing radial retinectomy may potentially be applied in RRD with advanced PVR but has rarely been reported to date. Future studies are needed to evaluate its outcomes and long-term complications.

Central forces and secular perihelion motion

2007 ◽  
Vol 85 (10) ◽  
pp. 1045-1054 ◽  
Author(s):  
M M D'Eliseo
Keyword(s):  
Differential Equation ◽  
General Formula ◽  
Elliptical Orbit ◽  
New Method ◽  
Secular Motion ◽  
Integro Differential Equation ◽  
First Order ◽  
Light Rays ◽  
Radial Forces ◽  
Central Forces

The first-order orbital equation and its perturbed version under the form of an integro-differential equation provide a new method to study, respectively, the elliptical orbit and the secular motion of a planetary perihelion due to the perturbing action of an important category of central forces: the inverse-power radial forces. For this, a general formula is found. The related problems of the gravitational bending of fast particles and light rays are studied using the same methods. PACS Nos.: 02.60.Nm, 04.25.–g, 46.15.Ff, 45.50.Pk

Stochastic simulation of the spatio-temporal field of the average daily heat index in Southern Russia

2020 ◽  
Vol 82 ◽  
pp. 149-160
Author(s):  
N Kargapolova
Keyword(s):  
Heat Waves ◽  
Numerical Models ◽  
Heat Index ◽  
Real Field ◽  
Gaussian Field ◽  
The Real ◽  
Southern Russia ◽  
Weather Stations ◽  
Spatio Temporal ◽  
Temporal Field

Numerical models of the heat index time series and spatio-temporal fields can be used for a variety of purposes, from the study of the dynamics of heat waves to projections of the influence of future climate on humans. To conduct these studies one must have efficient numerical models that successfully reproduce key features of the real weather processes. In this study, 2 numerical stochastic models of the spatio-temporal non-Gaussian field of the average daily heat index (ADHI) are considered. The field is simulated on an irregular grid determined by the location of weather stations. The first model is based on the method of the inverse distribution function. The second model is constructed using the normalization method. Real data collected at weather stations located in southern Russia are used to both determine the input parameters and to verify the proposed models. It is shown that the first model reproduces the properties of the real field of the ADHI more precisely compared to the second one, but the numerical implementation of the first model is significantly more time consuming. In the future, it is intended to transform the models presented to a numerical model of the conditional spatio-temporal field of the ADHI defined on a dense spatio-temporal grid and to use the model constructed for the stochastic forecasting of the heat index.

Extending "the Shorted Port Method" for Calculation of S-Matrices, Using Reduced Numerical Models

2003 ◽  
Vol 59 (3-4) ◽  
pp. 10
Author(s):  
D. Yu. Kulik ◽  
S. L. Senkevich ◽  
Victor Ivanovich Tkachenko
Keyword(s):  
Numerical Models

A Laboratory Device to Measure the Interfacial Phenomena between Rubber and Rough Surfaces

1999 ◽  
Vol 27 (4) ◽  
pp. 206-226 ◽  
Author(s):  
L. Garro ◽  
G. Gurnari ◽  
G. Nicoletto ◽  
A. Serra
Keyword(s):  
Rough Surfaces ◽  
Computer Software ◽  
Interfacial Phenomena ◽  
New Device ◽  
The Road ◽  
Constant Torque ◽  
Rubber Compounds ◽  
Simple Geometry ◽  
Tangential Forces ◽  
On The Road

Abstract The interfacial phenomena between tread rubber compounds and rough surfaces are responsible for most of the behavior of a tire on the road. A new device was developed for the investigation of these phenomena in the laboratory. The device consists of a fully instrumented road wheel on which a simple geometry specimen is driven. The possibilities offered by this device are to perform tests at constant slip or at constant torque on both wet and dry surfaces, with complex cycles. The machine allows the measurement of slip, tangential forces, and temperature on the specimen, and computer software adds the possibility of applying Fourier analyses on force, road wheel speed, and specimen speed data. Other possibilities offered by the road wheel are to change the road surface, the load on the specimen, and the water rate. The description of a complete experiment is detailed in the paper showing the correlation of data with actual tire performances.

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