Intermolecular And Surface Forces

In the classical theory black holes can only absorb and not emit particles. However it is shown that quantum mechanical effects cause black holes to create and emit particles as if they were hot bodies with temperature\(\frac{{h\kappa }}{{2\pi k}} \approx 10^{ - 6} \left( {\frac{{M_ \odot }}{M}} \right){}^ \circ K\) where κ is the surface gravity of the black hole. This thermal emission leads to a slow decrease in the mass of the black hole and to its eventual disappearance: any primordial black hole of mass less than about 1015 g would have evaporated by now. Although these quantum effects violate the classical law that the area of the event horizon of a black hole cannot decrease, there remains a Generalized Second Law:S+1/4A never decreases whereS is the entropy of matter outside black holes andA is the sum of the surface areas of the event horizons. This shows that gravitational collapse converts the baryons and leptons in the collapsing body into entropy. It is tempting to speculate that this might be the reason why the Universe contains so much entropy per baryon.

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Particle Creation by Black Holes

Quality function deployment: A literature review

Annalen der Physik

Nonlinear Oscillations: Exact Solutions and their Approximations

This article provides a brief historical review of multi-body dynamics analysis, initi- ated by the Newtonian axioms through constrained (removed degrees of freedom) Lagrangian dynamics or restrained (resisted degrees of freedom) Newton-Euler formulation. It provides a generic formulation method, based on system dynamics in a reduced configuration space, which encompasses both the aforementioned methods and is applicable to any cluster of material points. A detailed example is provided to show the integration of other physical phenomena such as flexibility and acoustic wave propagation into multi-body dynamics analysis. It is shown that in the scale of minutiae, when the action potentials deviate from Newtonian laws, the forces are often described by empirical or stochastic functions of separation and the medium of interactions. These make for complex analyses and distinguish a host of many body problems from Newtonian laws of motion. A simple example is provided to demonstrate this. It is suggested that unification of many-body analysis with that of multi-body dynamics is incumbent on the fundamental understanding of interaction potentials at close separations.

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From multi-body to many-body dynamics:

This technical note provides a brief background to the historical developments that led to the generalization of Galileo's principle of relativity, leading to Einstein's general theory of relativity. Therefore, its primary purpose is to mark the contributions made in physics of motion on this occasion—the marking of the new Millennium. To keep with the tradition set in this journal, this note contains a new analysis in respect of reported super-luminal observations in gain-assisted light propagation, in particular vis-a-vis their concordance with the general theory of relativity. The incompleteness principle, as an axiom of observation, is introduced here to resolve this issue.

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Relativity: 300 years from a principle to reality

The paper presents transient thermal-mixed-hydrodynamics of piston compression ring–cylinder liner conjunction for a 4-cylinder 4-stroke gasoline engine during a part of the New European Drive Cycle (NEDC). Analyses are carried out with and without cylinder de-activation technology in order to investigate its effect upon the generated tribological conditions. In particular, the effect of cylinder deactivation upon frictional power loss is studied. The predictions show that overall power losses in the piston–ring cylinder system worsen by as much as 10% because of the increased combustion pressures and liner temperatures in the active cylinders of an engine operating under cylinder deactivation. This finding shows the down-side of this progressively employed technology, which otherwise is effective in terms of combustion efficiency with additional benefits for operation of catalytic converters. The expounded approach has not hitherto been reported in literature.

Effect of Cylinder De-Activation on the Tribological Performance of Compression Ring Conjunction: Part J: Journal of Engineering Tribology

This paper investigates an NVH (Noise, Vibration and Harshness) phenomenon, which occurs as a load reversal in the presence of lashes in the driveline and is known in industry as clonk. A combined study of rigid multi-body dynamic analysis and flexible body oscillations, using super-element FEA techniques is being deployed. The results show high contribution in the driveline vibrational response of certain structural modes of the driveshaft pieces, induced by remote impacting of meshing transmission teeth trough backlash. The predicted spectrum of vibration shows good conformance with previously obtained experimental values, for both impact testing of the driveshaft pieces, as well as those obtained by vibration monitoring of experimental rigs (Vafaei et al, 2001).Copyright © 2003 by ASME

Elasto-Multibody Dynamic Simulation of Impact Induced High Frequency Vehicular Driveline Vibrations

Both the piston ring and cylinder bore experience wear throughout their life cycle. Therefore change occurs in the geometrical profile and topography of the ring. In addition, coating on the ring is also subject to wear, thus altering the physical/mechanical property of the contacting surface. These changes affect the tribological performance of the ring-bore conjunction. Geometrical changes often alter the ring contacting profile, which affects the entrainment of the lubricant into the conjunction. This can affect the regime of lubrication, thus mechanisms that contribute to friction. Wear of surfaces also plays some role in boundary friction in terms of topographical changes as well as surface properties such as hardness and asperity shear strength. Most analysis does not take into account changes in tribological conditions which occur as the result of these salient changes in practice. The paper intends to bridge this gap in the fundamental knowledge and provide explanations for some in-field experiences noted with wear of a compression ring in a typical engine test. The method of solution used is based on the average flow factors which are indicative of entrainment of the lubricant through the rough ring-bore conjunction. This approach was initiated by Patir and Cheng, for which realistic topographical parameters according to the stage of the wear process is included. Changes in friction and fuel energy consumed are predicted.

Homer Rahnejat

Papers

From multi-body to many-body dynamics:

Relativity: 300 years from a principle to reality

Effect of Cylinder De-Activation on the Tribological Performance of Compression Ring Conjunction: Part J: Journal of Engineering Tribology

Elasto-Multibody Dynamic Simulation of Impact Induced High Frequency Vehicular Driveline Vibrations

Performance evaluation of piston compression ring through accelerated wear in engine tests