Abstruct-This paper presents a theoretical framework for automatically partitioning parallel loops to minimize cache coherency traffic on shared-memory multiprocessors. While several previous papers have looked at hyperplane partitioning of iteration spaces to reduce communication traffic, the problem of deriving the optimal tiling parameters for minimal communication in loops with general affine index expressions has remained open. Our paper solves this open problem by presenting a method for deriving an optimal hyperparallelepiped tiling of iteration spaces for minimal communication in multiprocessors with caches. We show that the same theoretical framework can also be used to determine optimal tiling parameters for both data and loop partitioning in distributed memory multicomputers. Our framework uses matrices to represent iteration and data space mappings and the notion of uniformly intersecting references to capture temporal locality in array references. We introduce the notion of data footprints to estimate the communication traffic between processors and use linear algebraic methods and lattice theory to compute precisely the size of data footprints. We have implemented this framework in a compiler for Alewife, a distributed sharedmemory multiprocessor. multiprocessors, compilers, tiling, minimizing communication.

A combined experimental and theoretical study on the photoluminescence (PL) properties of strontium zirconate (SZ) and Sm3+ doped SZ nanostructures is presented in this work.

Zn 2 P 2 O 7 :Eu 3+ was synthesized and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM); Fourier transformed infrared spectroscopy (FTIR) and photoluminescence (PL) techniques. Based on the time resolved emission spectroscopic investigations (TRES), it was inferred that two different types of Eu 3+ ions were present in the zinc pyrophosphate. The first type was a long lived species ($s ¼ 1.77 ms) present at relatively few symmetric '5-coordinated Zn' sites, while the second was a short lived species ($s ¼ 620 ms) present at symmetric '6-coordinated Zn' sites. This unusual behavior of the trivalent rare earth species could be explained with the help of Judd-Ofelt (J-O) calculations. From the calculations, the radiative (s R ) and non radiative (s NR ) life times were evaluated for both species. It was observed that the radiative life time of the Eu 3+ species present in symmetric environment was higher than that of the species present in the asymmetric environment, which is consistent with the selection rules governing the transition. It was observed that the presence of a very strong non-radiative component at the symmetric site brings down the overall lifetime value. The J-O intensity parameters for all the Eu 3+ species present in the pyrophosphate system were calculated adopting standard procedure. U 4 > U 2 was found that for short lived species; while for the long lived species, the reverse trend was observed further confirming the correlation between the asymmetry and bonding.

Considering that ZnAl2O4 spinel has two different sites (octahedral and tetrahedral) and its properties change with dopant ion distribution among these two sites; ZnAl2O4 doped with varied concentrations of Fe(3+) was synthesized by a low temperature sol-gel combustion method. Phase purity and structural investigations were carried out using Rietveld refined X-ray diffraction which shows a decrease in the value of cell parameters at higher doping levels. Photoluminescence (PL) and electron paramagnetic resonance (EPR) studies have shown that on doping, Fe(3+) ions were distributed in both tetrahedral and octahedral sites. At octahedral sites, Fe(3+) exhibited a broad red emission around 745 nm while at tetrahedral sites it exhibited well-defined vibronic sidebands at 665, 674, 684 and 693 nm along with a broad blue band with a maxima at 445 nm at room temperature. EPR studies have shown a broad spectrum at g ≈ 2.2 which corresponds to the Fe(3+) in octahedral sites, while the broad signal at g ≈ 4.2 belongs to Fe(3+) in tetrahedral sites. It was also inferred from these studies that Fe(3+) prefers to occupy octahedral sites at higher concentrations and at higher annealing temperatures. The PL decay behavior of Fe(3+) in ZnAl2O4 has also shown that two different types of Fe(3+) ions were present in this matrix. The first type was a long lived species (τ ≈ 170 μs) present at octahedral sites and the other was a short lived species (τ ≈ 40 μs) present at the tetrahedral sites; the fraction of the long lived species predominate at higher concentrations. Thus the present work is mainly focused on understanding the tuning of local site occupancy of the dopant ion among those sites with varying concentration and annealing temperature, using the dopant ion itself as a spectroscopic probe, which further helps in understanding the phase (inverse and normal) of the spinel.