150,795 research outputs found
CMB Observations: improvements of the performance of correlation radiometers by signal modulation and synchronous detection
Observation of the fine structures (anisotropies, polarization, spectral
distortions) of the Cosmic Microwave Background (CMB) is hampered by
instabilities, 1/f noise and asymmetries of the radiometers used to carry on
the measurements. Addition of modulation and synchronous detection allows to
increase the overall stability and the noise rejection of the radiometers used
for CMB studies. In this paper we discuss the advantages this technique has
when we try to detect CMB polarization. The behaviour of a two channel
correlation receiver to which phase modulation and synchronous detection have
been added is examined. Practical formulae for evaluating the improvements are
presented.Comment: 18 pages, 3 figures, New Astronomy accepte
Distributed-Memory Breadth-First Search on Massive Graphs
This chapter studies the problem of traversing large graphs using the
breadth-first search order on distributed-memory supercomputers. We consider
both the traditional level-synchronous top-down algorithm as well as the
recently discovered direction optimizing algorithm. We analyze the performance
and scalability trade-offs in using different local data structures such as CSR
and DCSC, enabling in-node multithreading, and graph decompositions such as 1D
and 2D decomposition.Comment: arXiv admin note: text overlap with arXiv:1104.451
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