Search results for "Newton"

A relativistic approach to gravitational instability in the expanding Universe: second-order Lagrangian solutions

1994

A Lagrangian relativistic approach to the non--linear dynamics of cosmological perturbations of an irrotational collisionless fluid is considered. Solutions are given at second order in perturbation theory for the relevant fluid and geometric quantities and compared with the corresponding ones in the Newtonian approximation. Specifically, we compute the density, the volume expansion scalar, the shear, the ``electric" part, or tide, and the ``magnetic" part of the Weyl tensor. The evolution of the shear and the tide beyond the linear regime strongly depends on the ratio of the characteristic size of the perturbation to the cosmological horizon distance. For perturbations on sub--horizon scal…

Answering Schrödinger's "What Is Life?"

2020

In his &ldquo

The reflection component in NS LMXBs

2014

Thanks to the good spectral resolution and large effective area of the EPIC/PN instrument on board of XMM-Newton, we have at hand a large number of observations of accreting low-mass X-ray binaries, that allow for the fist time a comprehensive view on the characteristics of the reflection component at different accretion regimes and to probe the effects of a magnetosphere on its formation. We focus here on a comparative analysis of the reflection component from a series of spectroscopic studies on selected sources: 4U 1705-44, observed both in the soft and hard state, the pulsating ms pulsars SAX J1808.4-3658 and IGR J17511-3057, and the intermittent pulsar HETE J1900-2455. Although the sou…

Low-cost viscometer based on energy dissipation in viscous liquids

2001

We describe a new type of low-cost easy-to-use viscometer based on the temperature elevation in a liquid under shear flow. After calibration, this instrument can be used to measure the apparent steady state viscosity for both Newtonian and non-Newtonian liquids with no yield stress. We compute the rise in temperature due to viscous dissipation in a Couette cell and compare it to experimental results for different fluids. We show that the variation of the temperature with shear rate can be used to characterize the rheological behaviour of viscous fluids and to evaluate their viscosity in a large domain, from typically a few cP up to more than 10 P, with an accuracy of about ±5%. In contrast …

Some relationships between the calculus of Newton, Bombelli’s Algebra and Leibniz

2010

Extension of the Concept of Intrinsic Viscosities to Arbitrary Polymer Concentration: From [η] via {η} to Intrinsic Bulkiness

2019

The capabilities of an alternative definition of intrinsic viscosities [η] published some years ago is being studied by means of comprehensive viscometric data reported in the early days of polymer science. It introduces the generalized intrinsic viscosity {η} as the specific hydrodynamic volume at arbitrary polymer concentration c. {η} quantifies the size of the flow unit and decreases monotonously for T ≫ Tg (glass transition temperature) as a function of c but passes a pronounced minimum as T approaches Tg. In the limit of the pure polymer melt, {η} becomes ; this newly introduced property is termed intrinsic bulkiness, by analogy to the intrinsic viscosity, and provides noncalorimetric …

Are polymers suitable rock analogs?

2002

To evaluate if a polymer is suitable for analog modeling, it is essential to know the rheological properties of the material. Polymers used in analog modeling exhibit a complex rheological behavior; only part of which has been taken into account in most modeling studies. The mechanical behavior is strongly dependent on strain rate and temperature, and is characterized by specific dependencies of the storage and loss moduli, related to the elasticity and viscosity, on the deformation rate (frequency). We have measured the storage and loss moduli at a broad range of strain rates and strains, using an oscillatory parallel-disk rheometer. Investigated materials are polydimethylsiloxane (PDMS), …

Strictly convergent algorithm for an elliptic equation with nonlocal and nonlinear boundary conditions

2012

The paper describes a formally strictly convergent algorithm for solving a class of elliptic problems with nonlinear and nonlocal boundary conditions, which arise in modeling of the steady-state conductive-radiative heat transfer processes. The proposed algorithm has two levels of iterations, where inner iterations by means of the damped Newton method solve an appropriate elliptic problem with nonlinear, but local boundary conditions, and outer iterations deal with nonlocal terms in boundary conditions.

Reliable computation and local mesh adaptivity in limit analysis

2019

The contribution is devoted to computations of the limit load for a perfectly plastic model with the von Mises yield criterion. The limit factor of a prescribed load is defined by a specific variational problem, the so-called limit analysis problem. This problem is solved in terms of deformation fields by a penalization, the finite element and the semismooth Newton methods. From the numerical solution, we derive a guaranteed upper bound of the limit factor. To achieve more accurate results, a local mesh adaptivity is used. peerReviewed

Newton, Isaac

2015