Voltage Sag Compensation Using Dynamic Voltage Restorer for DFIG Fed Distribution Network

This paper investigates compensation of voltage sag due to faults in distribution system for a doubly fed induction motor(DFIG) configuration using dynamic voltage restorer(DVR). Series compensation of terminal voltage during fault conditions using DVR is carried out by injecting voltage at the point of common coupling to the grid voltage to maintain constant DFIG stator voltage. However, the control of the DVR is crucial in order to improve the FRT capability in the DFIG-based wind turbines.wind turbine is controlled by pitch angle which controls the rotor and stator currents of induction generator under different wind speeds. DVR injects voltage in series using vector control which compensates voltage quality problems. The proposed work is verified using matlab/ Simulink software. Keywords: DFIG,DVR.Voltage sag,FRT DOI: 10.7176/ISDE/10-2-0

USL/DBMS NASA/PC R and D project system testing standards

A set of system testing standards to be used in the development of all C software within the NASA/PC Research and Development Project is established. Testing will be considered in two phases: the program testing phase and the system testing phase. The objective of these standards is to provide guidelines for the planning and conduct of program and software system testing

Spin-phonon coupling in multiferroic RCrO3_3 (R-Y, Lu, Gd, Eu, Sm): A Raman study

Raman study on a select few orthochromites, RCrO$_3$ (R = Y, Lu, Gd, Eu and Sm) shows that the phonon behavior at TN in compounds with magnetic R-ion (Gd and Sm) is remarkably different from that of non-magnetic R-ion (Y, Lu and Eu). While anomalies in most of the observed phonon frequencies in all these compounds may result from the distortion of CrO$_6$ octahedra due to size effect and magnetostriction arising from Cr-ordering, the anomalous behavior of their linewidths observed at TN for the compounds with only magnetic R-ion suggests spin-phonon coupling. The presence of spin-phonon coupling and the anomalies in the low frequency modes related to R-ion motion in orthochromites (R = Gd and Sm) support the suggestion that the coupling between 4f-3d moments play important role in inducing switchable electric polarization.Comment: 6 pages (two column format), 7 figures; The updated version of the manuscript can be found at Euro. Phys. Lett. 101, 17008 (2013

Effect of pressure on octahedral distortions in RCrO3 (R = Lu, Tb, Gd, Eu, Sm): The role of R-ion size and its implications

The effect of rare-earth ion size on the octahedral distortions in rare-earth chromites (RCrO3, R = Lu, Tb, Gd, Eu, Sm) crystallizing in the orthorhombic structure has been studied using Raman scattering and synchrotron powder x-ray diffraction up to 20 GPa. From our studies on RCrO3 we found that the octahedral tilts (distortions) increase with pressure. This is contrary to the earlier report which suggests that in LaCrO3, the distortions decrease with pressure leading to a more ordered phase at high pressure. Here we observe that the rate of increase in distortion decreases with the increase in R-ion radii. This occurs due to the reduction in the compression of RO12 polyhedra with a corresponding increase in the compression of the CrO6 octahedra with increasing R-ion radii. From the Raman studies, we predict a critical R-ion radii, above which we expect the distortions in RCrO3 to reduce with increasing pressure leading to what is observed in the case of LaCrO3. These Raman results are consistent with our pressure dependent structural studies on RCrO3 (R = Gd, Eu, Sm). Also, our results suggest that the pressure dependence of N\'eel temperature, TNCr, (where the Cr3+ spin orders) in RCrO3 is mostly affected by the compressions of Cr-O bonds rather than the alteration of octahedral tilts.Comment: 17 pages, 8 figures This manuscript has been published in Material Research Expres

Influence of lattice distortion on the Curie temperature and spin-phonon coupling in LaMn0.5_{0.5}Co0.5_{0.5}O3_{3}

Two distinct ferromagnetic phases of LaMn$_{0.5}$Co$_{0.5}$O$_{3}$ having monoclinic structure with distinct physical properties have been studied. The ferromagnetic ordering temperature $\textit{T}_{c}$ is found to be different for both the phases. The origin of such contrasting characteristics is assigned to the changes in the distance(s) and angle(s) between Mn - O - Co resulting from distortions observed from neutron diffraction studies. Investigations on the temperature dependent Raman spectroscopy provide evidence for such structural characteristics, which affects the exchange interaction. The difference in B-site ordering which is evident from the neutron diffraction is also responsible for the difference in $\textit{T}_{c}$. Raman scattering suggests the presence of spin-phonon coupling for both the phases around the $\textit{T}_{c}$. Electrical transport properties of both the phases have been investigated based on the lattice distortion.Comment: 9 figure

Exploring the Anti-inflammatory and Anti-cancer compounds from the leaves of Acalypha indica

Abstract: Acalypha indica (Euphorbiaceae) is commonly known as Indian Copperleaf and India

Neutrino mixing matrices with relatively large θ13\theta_{13} and with texture one-zero

The recent T2K, MINOS and Double Chooz oscillation data hint a relatively large $\theta_{13}$, which can be accommodated by some general modification of the Tribimaximal/Bimaximal/Democratic mixing matrices. Using such matrices we analyze several Majorana mass matrices with texture one-zero and show whether they satisfy normal or inverted mass hierarchy and phenomenologically viable or not.Comment: 16 pages, 3 figures, minor modification in the text, version to appear in EPJ

Synthon Modularity in 4-Hydroxybenzamide-Dicarboxylic Acid Cocrystals

A family of 4-hydroxybenzamide-dicarboxylic acid cocrystals has been designed and subsequently isolated and characterized. The design strategy follows from an understanding of synthon modularity in crystal structures of monocomponent crystals such as gamma-quinol, 4,4'-biphenol and 4-hydroxybenzoic acid. These monocomponent structures contain infinite O-H center dot center dot center dot O-H center dot center dot center dot O-H center dot center dot center dot cooperative synthons linked with molecular connectors such as phenyl and biphenyl, and supramolecular connectors such as the acid dimer in 4-hydroxybenzoic acid. The cocrystal design was influenced by the anticipation that dicarboxylic acids can form a supramolecular connector mediated by acid-amide synthons with 4-hydroxybenzamide, which can then form the phenol O-H center dot center dot center dot O-H center dot center dot center dot O-H center dot center dot center dot infinite synthon. Effectively, the acid-amide and phenol synthons are insulated. The short axis of such a structure will be around 5.12 angstrom and this is borne out in 2:1 cocrystals of 4-hydroxybenzamide with oxalic, succinic, fumaric, glutaric (two forms) and pimelic acids. Hydrated variations of this structure type are seen in the cocrystals obtained with adipic and sebacic acids

Designing ternary cocrystals with hydrogen bonds and halogen bonds

A graded selection of hydrogen bonds and halogen bonds allows for the isolation of 2 : 1 : 1 ternary cocrystals of the general form 4-nitrobenzamide : diacid : 1,4-dihalogenated benzene, which are mediated by the amide-acid and I center dot center dot center dot O2N supramolecular synthons