Neutron Diffraction Studies on Chemical and Magnetic Structure of Multiferroic PbFe0.67W0.33O3

We report on the single phase synthesis and room temperature structural characterization of PbFe0.67W0.33O3 (PFW) multiferroic. The PFW was synthesized by low temperature sintering, Columbite method. Analysis of powder XRD pattern exhibits single phase formation of PFW with no traces of pyrochlore phase. Detailed analysis of room temperature neutron diffraction (ND) reveals cubic phase at room temperature, space group Pm-3m. The ND pattern clearly reveals magnetic Bragg peak at 2theeta = 18.51 (Q = 1.36{\AA}-1). The refinement of magnetic structure reveals G-type antiferromagnetic structure in PFW at room temperature. The dielectric constant and loss tangent decreases with increasing frequency. The room temperature P-E measurements shows a non-linear slim hysteresis, typical nature of relaxor multiferroics, with saturation and remnant polarizations of Ps = 1.50 microC/cm2 and Pr = 0.40 microC/cm2, respectively.Comment: 3 pages, 5 figures, conferenc

An Automated Data Warehouse

An increasing number of organizations are implementing data warehouses to strengthen their decision support systems. This comes with the challenges of the population and the periodic update of data warehouses. In this thesis, we present a tool that provides users with features to create a warehouse database and transform structures of the source database into structures for the warehouse database. It is highly interactive, easy to use, and hides the underlying complexity of manual SQL code generation from its users. Attributes from source tables can be mapped into new attributes in the warehouse database tables using aggregate functions. Then, relevant data is automatically transported from the source database to the newly created warehouse. The tool thus integrates warehouse creation, schema mapping and data population into a single generalpurpose tool. This tool has been designed as a component of the framework for an automated data warehouse being developed at theComputer Science Department, University of New Orleans. Users of this framework are the database administrators, who will also be able to synchronize updates of multiple copies of the data warehouse. Warehouse images that need to be updated are taken offline and applications that need to access the data warehouse can now access any of the other image warehouses. The Switching Application built into this framework switches between databases in a way that is totally transparent to applications so that they do not realize existence of multiple copies of the data warehouse. In effect, even non-technical users can create, populate and update data warehouses with minimal time and effort

Investigations on Structural and Transport Properties of Mixed Oxide Systems

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Measurement of PVFS2 performance on InfiniBand

InfiniBand is becoming increasingly popular as a fast interconnect technology between servers and storage. It has far better price/performance ratio compared to both Gigabit Ethernet and 10 Gigabit Ethernet, and hence is being increasingly used for high-performance computing applications. PVFS2, the second generation Parallel Virtual File System (PVFS), is a distributed file system for parallel data access that is being increasingly used in clustered applications. As previous studies have shown that in general, PVFS2 over InfiniBand offers enhanced I/O rates compared to PVFS2 over TCP and Gigabit Ethernet. Apart from the hardware technology, the application programming interface into the file system also makes a difference. To get better parallel performance, the choice of a file system interface is important. Our study is to benchmark and compare the performance of PVFS2 running over InfiniBand using different file system interfaces. IOR is a popular I/O microbenchmarking tool that supports the POSIX and MPI I/O file system interfaces. In addition to testing these already supported interfaces, we have written a PVFS2 module extension for IOR to support native PVFS2 interfaces into the PVFS2 file system. As we shall see in this study, using native PVFS2 interface offers significant performance benefit compared to other file system interfaces on the PVFS2 file system. Our benchmarking effort also involves studying the effect of a multi-client environment on the I/O performance of different file system interfaces. Based on the benchmarking results we obtain, we determine the most efficient application programming interface for parallel I/O on PVFS2 in a typical multi-client parallel application scenario