Effects of calcination on microscopic and mesoscopic structures in Ca- and Sr-doped nano-crystalline lanthanum chromites
ABSTRACT Calcination behavior of nano-crystalline lanthanum chromites doped with calcium and strontium has been probed by Fourier transform infrared spectroscopy, X-ray diffraction and small-angle neutron scattering as a function of temperature. Infrared spectroscopic results imply that over a range of temperatures, some intermediate phase of dopant chromates evolve and then dissolve back, which has also been confirmed by the XRD. Neutron scattering data reveal a fractal type correlation of building blocks in virgin powders. Increase in fractal dimension and reduction in upper cutoff vis-à-vis the densification of agglomerates were found with increasing calcination temperature. Calcination, beyond 900 °C, results in breaking down of the fractal morphology almost completely. Such shrinkage event also results in a modification of the microscopic structure. These changes have been attributed to the compaction of agglomerates of both Ca- and Sr-doped lanthanum chromites, assisted via liquid state sintering by the melting of the intermediate phases at intermediate calcination stages.
Article: Gigabit networking[show abstract] [hide abstract]
ABSTRACT: Factors driving gigabit networking are identified. The problem of wedding the local area networks (LANs) used to interconnect supercomputers to the long-distance networks used for telecommunications is discussed. Changes in computer and telecommunications networks to accommodate higher speeds, longer distances, and new technology are examined. The American National Standard High-Performance Parallel Interface (HIPPI) is considered. Connecting HIPPI to SONET and to FDDI is addressed. Circuit-switched, ring, and tree architectures for advanced networks are discussed.< >IEEE network 06/1992; · 2.15 Impact Factor
Article: In search of gigabit applications[show abstract] [hide abstract]
ABSTRACT: Applications in existing specialized, metacomputer environments and those yet to be developed for services such as telecommunications, distributed data, and image transfer that will require networks which can handle volumes of data on the order of gigabits per second are discussed. Specific examples are presented from the fields of computational science, data navigation, and collaborative environments and instrument control. It is concluded that distributed computing and collaborative environments that support the interaction of multiple computers, as well as the interaction of computers with humans, are the paradigms that will characterize gigabit applications.< >IEEE Communications Magazine 05/1992; · 3.66 Impact Factor