How do real graphs evolve over time? What are “normal” growth patterns in social, technological, and information networks? Many studies have discovered patterns in static graphs, identifying properties in a single snapshot of a large network, or in a very small number of snapshots; these include heavy tails for inand out-degree distributions, communities, small-world phenomena, and others. Howe...

The interface atomic structure was proposed to have a critical effect on the microstructure evolution during sintering of ceramic materials. In liquid-phase sintering, spherical grains show the normal grain growth behavior without exception, while angular grains often grow abnormally. The coarsening process of spherical grains with a disordered or rough interface atomic structure is diffusion-c...

Sintering behavior with and without external stress was investigated using undoped and doped (1500 ppm yttria) sub-micron a-alumina powders. The yttria doped alumina showed anomalous behavior with grain size around 0.9 pm, a second peak in densification rate during free sintering and a stagnation followed by a steep increase in flow stress during sinter forging. These were thought to correspond...

Densification and distortion of W-Ni-Fe tungsten heavy alloys during liquid phase sintering are modeled using constitutive laws of grain growth, densification, and deformation. The models are ‘‘calibrated’’ via carefully designed experiments to obtain the necessary parameters to enable modeling. Metallographic analysis of quenched samples is used to obtain grain size data as functions of time a...

We verify the imaging performance of hypertelescopes on the sky, using a new scheme for pupil densification. To avoid seeing limitations, we used a miniature version with a 10 cm aperture containing 78 sub-apertures of 1 mm size, arrayed periodically as a square grid. The pupil densification is achieved with a pair of micro-lens arrays, where each pair of facing lenses behaves like a tiny demag...

Transparent polycrystalline spinel ceramic was fabricated without any sintering aids by spark plasma sintering method of a mixture of Al2O3 and MgO powders for only 10min soak at 1250°C. Densification, microstructure and optical transparency of spinel were examined. The spinel exhibits an in-line transmission of 55% for a visible-wavelength of 470nm and high hardness value of 2040 HV.

The deformation of metallic glasses involves two competing processes: a disordering process involving dilatation, free volume accumulation, and softening, and a relaxation process involving diffusional ordering and densification. For metallic glasses at room temperature and under uniaxial loading, disordering usually dominates, and the glass can fail catastrophically as the softening process ru...

Spectroscopic properties of germanium oxygen-deficient centers were studied in vapor axial deposition and modified chemical-vapor deposition germanosilicate glass after hydrostatic densification by as much as 19%. Gaussian decomposition showed a broadening and a significant shift of the initial absorption bands at 5.11 and 5.42 eV. A threefold decrease of the 3.15-eV luminescence band was revea...

This paper investigates thermal modelling of the selective laser sintering process for amorphcus polycarbonate powders. The aim is to develop a simulation for process accuracy and control which are key areas of developement for the new layer manufacturing rapid prototyping technologies. A state-of-the-art adaptive mesh 2 0 finite difference code is used simultaneously to consider heating and si...

Gelation and densification of calcium-silicate-hydrate take place during cement hydration. Both processes are crucial for the development of cement strength, and for the long-term evolution of concrete structures. However, the physicochemical environment evolves during cement formation, making it difficult to disentangle what factors are crucial for the mechanical properties. Here we use Monte ...