1,511 research outputs found

    Structural Basis for the Anomalously Low Spontaneous Polarisation Values of the Polar Phase of Sr1-xCaxTiO3 (x=0.02, 0.04): Evidence for a Ferrielectric Ordering

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    Full pattern Le-Bail refinement using x-ray powder diffraction profiles of Sr1-xCaxTiO3 for x=0.02, 0.04 in the temperature range 12 to 300 K reveals anomalies in the unit cell parameters at 170, 225 K due to an antiferrodistortive (cubic to tetragonal I4/mcm) phase transition and at ~32, ~34 K due to a transition to a polar phase (tetragonal I4/mcm to orthorhombic Ic2m), respectively. The lower transition temperatures obtained by us are in excellent agreement with those reported on the basis of the dielectric studies by Bednorz and Muller, [10] who attributed these to ferroelectric transition. Rietveld analysis of the diffraction profiles of the polar phase reveals off-centre displacements of both Sr2+/Ca2+ and Ti4+ ions in the X-Y plane along pseudocubic directions, in agreement with the experimentally reported direction of easy polarization by Bednorz and Muller, but the resulting dipole moments are shown to be ferrielectrically coupled in the neighbouring (001) planes along the [001] direction leading to anomalously low values of the spontaneous polarization at 12K.Comment: 5 pages, 4 figures and 1 tabl

    Survey of Document Clustering Approach for Real World Objects (Documents)

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    Since the amount of text data stored in computer repositories is growing every day, we need more than ever a reliable way to assemble or classify text documents. Clustering can provide a means of introducing some form of organization to the data, which can also serve to highlight significant patterns and trends. Document clustering is used in many fields such as data mining and information retrieval. This thesis presents the results of an experimental study of some common document clustering techniques. In particular, we compare the two main approaches of document clustering, agglomerative hierarchical clustering BIRCH and Partitional clustering algorithm K-means. As a result of comparing both algorithms we attempt to establish appropriate clustering technique to generate qualitative clustering of real world document. DOI: 10.17762/ijritcc2321-8169.15080

    Analysis of volume dependence of thermal expansivity for NaCl

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    In the present paper, a suitable model to evaluate the volume dependence of thermal expansivity α by using the reciprocal form of volume dependence of Anderson-Grüneisen parameter (δT) has been proposed. The newly developed relationship has satisfied the constraints of infinite pressure behavior, i.e., P → ∞ or V → 0. The results obtained through the present model show the consistency with the experimental data for NaCl

    Pulmonary Capillary Hemangiomatosis: A Rare Cause of Pulmonary Arterial Hypertension, Presenting as Supraventricular Tachycardia

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    With a prevalence of less than 1/million, Pulmonary Capillary Hemangiomatosis is a rare disorder of capillary proliferation in the alveolar septae leading to pulmonary arterial hypertension and mimics pulmonary veno-occlusive disease