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.

/pdf/particle-creation-by-black-holes-1htfzwsw5k.pdf

Particle Creation by Black Holes

Quality function deployment: A literature review

Annalen der Physik

Nonlinear Oscillations: Exact Solutions and their Approximations

A multi-scale mathematical model is used to study the effect of surface roughness on the adhesion and friction of microfibers engaged in side contact. Results are compared to closed-form analytic approximations derived from linear elastic contact mechanics.Copyright © 2008 by ASME

Effect of Surface Roughness on Adhesion and Friction of Microfibers in Side Contact

The parasitic frictional losses in an engine are estimated to account for 20% of the
total engine losses. These include those due to piston assembly (45%), bearings
(25%), pumping action (20%) and those attributed to the valve train system (10%).
Thus, a quarter of all the parasitic losses are due to engine bearings, which include the
main crankshaft support bearings (see chapter 18), big end bearing (see also chapter
19), and other camshaft and any rocker arm bearings. Though all these bearings are
essentially hydrodynamic journal bearings, the nature of load application,
construction and design is specific to each case. The main bearings have stationary
bushings (see also chapter 18), while the bore of the big end bearing is oscillating and
subjected to cyclic fluctuating loads from repetitive combustion pressure.
The role of the big end bearing is to sustain the transmitted forces through the
connecting rod, which are due to combustion pressure and inertial imbalance, as well
as transmitting the torque to drive the crankshaft. If it malfunctions due to any reason,
then this would lead to catastrophic engine failure. The understanding of journal
bearing concept is essential for detailed analysis of big end bearings (see chapter 18).

Tribology of big-end-bearings

The study of textured surface performance is one of the highly researched topics in recent times. This is mainly due to the advantages that such surfaces can potentially provide in practice, in mitigating adverse tribological conditions, such as friction and wear. However, considering the complexities found in practice, a methodological analysis and evaluation procedure is essential in order to gain an understanding of the benefits from utilising such features in a given contact. The current study provides a combined analytical and experimental approach towards an enhanced understanding of the behaviour of textured surfaces relative to their untextured counterparts. The developed analytical models are invaluable in providing an insight into the relationship between the many parameters involved in defining even simple surface texture feature geometry and the expected outcomes in practice, when corroborated with experimental results. The current study reports on such an endeavour. With the studied texture configuration, the results have shown the possibility of reducing friction by as much as 25%.

Combined Analytical and Experimental Evaluation of Frictional Performance of Lubricated Untextured and Partially Textured Sliders

This article commemorates Newton's contributions to mechanics in small scale. In particular, it deals with Newtonian slow viscous action of fluids in narrow conjunctions leading to hydrodynamics. It is shown that the Newtonian continuum relies on some bulk properties of fluids as opposed to their molecular interactions. When the latter and surface energy effects become dominant, the interaction potentials deviate from the Newtonian continuum. A plethora of largely empirically based force laws are used to describe conjunctional behaviours in nanoscale, usually lightly loaded.

Some of these force laws are described, and their applicability to nanoconjunctions of very small devices and some biological systems is noted. In general, a thorough understanding of all the involved kinetics is required. Representative problems in soft nanoscale contacts in normal (humid) atmosphere are highlighted in the article. It is shown that contact load/adhesion depends on several key parameters including surface roughness, surface free energy, atmospheric moisture, and normal approach velocity.

/pdf/newtonian-mechanics-in-scale-of-minutia-wfshv1sc12.pdf

Newtonian mechanics in scale of minutia

Vascular grafts are widely employed in clinical practice and still pose significant problems of compatibility and longevity, particularly when the prosthesis is to replace arteries of small diameter. Once a graft has been implanted in the vascular tree, there is no easy way of assessing its interactions with the surrounding tissue. Doppler flow probes or some imaging techniques are commonly used to monitor flow velocity in vascular prostheses. It is, however, difficult to monitor a patient's recovery on a continuous basis. Continuous means of measurement can be quite invaluable. This paper presents a high-carbon filled polymer (HCFP) sensor that is developed for blood flow measurement in vascular grafts. Furthermore, a computational fluid dynamics model of incompressible blood flow in elastic blood vessels is presented.

/pdf/blood-flow-measurement-using-a-highly-filled-carbon-polymer-56e4s7l2i9.pdf

Homer Rahnejat

Papers

Effect of Surface Roughness on Adhesion and Friction of Microfibers in Side Contact

Tribology of big-end-bearings

Combined Analytical and Experimental Evaluation of Frictional Performance of Lubricated Untextured and Partially Textured Sliders

Newtonian mechanics in scale of minutia

Blood flow measurement using a highly filled carbon polymer sandwich sensor and an elasto-pseudo compressible vascular flow