We analyse the classical and quantum geometry of the Barrett-Crane spin foam model for four dimensional quantum gravity, explaining why it has to be considering as a covariant realization of the projector operator onto physical quantum gravity states. We discuss how causality requirements can be consistently implemented in this framework, and construct causal transiton amplitudes between quantu...

the brass tubes with foam cores of alsi7sic3, alsi7sic3fe1 and alsi7sic3fe3 were produced as the crush-boxes with circle and square cross-section. then axial compressive behavior and energy absorption capability of the foam-filled tubes were investigated during the quasi-static progressive plastic buckling. the uniaxial compressive stress–strain curves of the foam-filled brass tubes exhibited t...

We develop the Z-Cone Model, in terms of which the energy of a foam may be estimated. It is directly applicable to an ordered structure in which every bubble has Z identical neighbours. The energy (i.e. surface area) may be analytically related to liquid fraction. It has the correct asymptotic form in the limits of dry and wet foam, with prefactors dependent on Z. In particular, the variation o...

We consider the EPRL spin foam amplitude for arbitrary embedded two-complexes. Choosing a definition of the faceand edge amplitudes which lead to spin foam amplitudes invariant under trivial subdivisions, we investigate invariance properties of the amplitude under consistent deformations, which are deformations of the embedded two-complex where faces are allowed to pass through each other in a ...

2 Mechanical engineer, USAMBRL. 3 Major, Army Medical Specialist Corps, USAMBRL. ROOM-TEMPERATURE-VULCANIZING (RTV) silicone rubber is a versatile material and easy to handle. The ingredients from which it is formed are thick liquids that vulcanize at room temperature within a short period of time after the catalyst is added. Depending upon the relative amounts of solid and foam ingredients, th...

In prosthetics, as in many other fields, plastic materials were quickly adopted as soon as their usefulness was recognized, not just as a substitute for other materials, but also as a supplement in places where no other material would function as well. The plastics industry is comparatively young; not much headway was made until the start of World War II. Since then giant strides were made with...

A dynamic model for describing the build-up and breakdown of a glass-melt foam is presented. The foam height is determined by the gas flux to the glass-melt surface and the drainage rate of the liquid lamellae between the gas bubbles. The drainage rate is determined by the average gas bubble radius and the physical properties of the glass melt: density, viscosity, surface tension, and interfaci...

This paper presents the results of studies concerned with the preparation of fresh food foams based on egg white and various hydrocolloids including Iranian gum tragacanth, guar and xanthan gums at different concentrations (0.002-0.040% w/w). The basic physical parameters of the obtained foams such as overrun, stability and morphology of gas bubbles were measured. Viscosity measurements were al...

Aqueous foams occur in several industrial applications including food production. One of the challenging issues in foams study is to evaluate the air bubbles stability. This problem is addressed in the present work using sequences of 2D macroscopic images of aqueous foams carried out in a glass column. Despite commercial softwares that are currently used in microscopy, the automatic analysis of...

The temperatures of standard glassware and ceramics are nearly impossible to tell just by sight. Therefore, burns from touching heated surfaces are common in the laboratory and in the kitchen. The sol-gel process is a safe method to create foam under ambient conditions. Adding different chemical compounds causes the foam to have varying physical and chemical characteristics. This project focuse...