4,637 research outputs found

    Modulation Method of Laser for Underwater Communication

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    Due to very high absorption of light in the water it is necessary to use high energy pulsed bluegreen lasers for underwater communication systems. However,these lasers do not have high repetition rates, sufficient enough to support high data rate signals. The pulse interval modulation method is one of the prospective methods of sending large bandwidth data using low frequency (500 to1000 pulses per second) pulsed laser. This method appears to be more promising for underwater communication system with likely development of fast PIM coder/decoder

    Source of the Bursty Bulk Flow Diffuse Aurora: Electrostatic Cyclotron Harmonic and Whistler Waves in the Coupling of Bursty Bulk Flows to Auroral Precipitation

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    Electron cyclotron harmonic (ECH) and whistler chorus waves are recognized as the two mechanisms responsible for the resonant waveparticle interactions necessary to precipitate plasma sheet electrons into the ionosphere, producing the diffuse Aurora. Previous work has demonstrated ECH waves dominate electron scattering at L shells >8, while whistler chorus dominates scattering at L shells L 1, consistent with electron betatron acceleration. Here, however, we nd whistler chorus emissions throughout an interval of fast ows where Te,/Te,||< 1. Parallel electron beams account for the enhanced parallel electron temperature and serve as the instability mechanism for the whistler chorus. The parallel electron beams and associated cigarshaped distributions are consistent with Fermi acceleration at dipolarizations in fast ows. We demonstrate that the scattering efciency of the whistler chorus exceeds that of ECH waves, which THEMIS also detects during the fast ows. The obliquity of the whistler waves permits efcient scattering of lowerenergy electrons into the diffuse aurora. We conclude that Fermi acceleration of electrons provides one important freeenergy source for the waveparticle interactions responsible for coupling plasma sheet electrons into the diffuse aurora during substorm conditions

    Design of Safe Slopes After Failure During an Earthquake

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    Four slope slides took place, during a major earthquake, on the slopes of hill that has a paper mill complex on its top. The subsoil condition and engineering parameters for the site were evaluated at the time of construction of this complex and again after the earthquake for the purpose of designing safe slopes. However, both times the variation in the numerical values of shear parameters obtained by different tests was very wide and it was difficult to arrive at some conclusion. Therefore, on the basis of failure surface geometries, these was assessed by back analysis and design of safe slope carried out

    Effect of rice husk biochar, carpet waste, farm yard manure and plant growth promoting rhizobium on the growth and yield of rice (Oryza sativa)

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    The present investigation was aimed for improving growth and yield of crop using waste products of differ-ent activities and also useful in ecological stability of soil environment. This objective is not only an economic option for poor farmer but also an effective strategy for increasing yield. The experiment was conducted in the organic farm-ing plot of the Institute of Agricultural Sciences, BHU, Varanasi during kharif season of rice crop in 2014. The field experiment was laid out in randomized block design (RBD) with 10 treatments and three replications. Application of graded level of biochar, carpet waste farm yard manure (FYM) and plant growth promoting rhizobium (PGPR) was found to significantly enhance the grain and straw yield of rice by 57.70% and 56.08% over control, respectively

    Electronic structure of Pr0.67_{0.67}Ca0.33_{0.33}MnO3_3 near the Fermi level studied by ultraviolet photoelectron and x-ray absorption spectroscopy

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    We have investigated the temperature-dependent changes in the near-EEF_F occupied and unoccupied states of Pr0.67_{0.67}Ca0.33_{0.33}MnO3_3 which shows the presence of ferromagnetic and antiferromagnetic phases. The temperature-dependent changes in the charge and orbital degrees of freedom and associated changes in the Mn 3dd - O 2pp hybridization result in varied O 2pp contributions to the valence band. A quantitative estimate of the charge transfer energy (EECT_{CT}) shows a larger value compared to the earlier reported estimates. The charge localization causing the large EECT_{CT} is discussed in terms of different models including the electronic phase separation.Comment: 19 pages, 7 figures, To be published in Phy. Rev.

    Study of Microstrip filters

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    Volume 2 Issue 1 (January 2014

    Conjugate (solid/fluid) computational fluid dynamics analysis of the space shuttle solid rocket motor nozzle/case and case field joints

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    Three-dimensional, conjugate (solid/fluid) heat transfer analyses of new designs of the Solid Rocket Motor (SRM) nozzle/case and case field joints are described. The main focus was to predict the consequences of multiple rips (or debonds) in the ambient cure adhesive packed between the nozzle/case joint surfaces and the bond line between the mating field joint surfaces. The models calculate the transient temperature responses of the various materials neighboring postulated flow/leakpaths into, past, and out from the nozzle/case primary O-ring cavity and case field capture O-ring cavity. These results were used to assess if the design was failsafe (i.e., no potential O-ring erosion) and reusable (i.e., no excessive steel temperatures). The models are adaptions and extensions of the general purpose PHOENICS fluid dynamics code. A non-orthogonal coordinate system was employed and 11,592 control cells for the nozzle/case and 20,088 for the case field joints are used with non-uniform distribution. Physical properties of both fluid and solids are temperature dependent. A number of parametric studies were run for both joints with results showing temperature limits for reuse for the steel case on the nozzle joint being exceeded while the steel case temperatures for the field joint were not. O-ring temperatures for the nozzle joint predicted erosion while for the field joint they did not

    HYDROCHEMICAL STUDIES OF THE HINDON RIVER, INDIA: SEASONAL VARIATIONS AND QUALITY-QUANTITY RELATIONSHIPS

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    A hydrochemical study of the Hindon river system in western Uttar Pradesh (India

    Non-Compositional Term Dependence for Information Retrieval

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    Modelling term dependence in IR aims to identify co-occurring terms that are too heavily dependent on each other to be treated as a bag of words, and to adapt the indexing and ranking accordingly. Dependent terms are predominantly identified using lexical frequency statistics, assuming that (a) if terms co-occur often enough in some corpus, they are semantically dependent; (b) the more often they co-occur, the more semantically dependent they are. This assumption is not always correct: the frequency of co-occurring terms can be separate from the strength of their semantic dependence. E.g. "red tape" might be overall less frequent than "tape measure" in some corpus, but this does not mean that "red"+"tape" are less dependent than "tape"+"measure". This is especially the case for non-compositional phrases, i.e. phrases whose meaning cannot be composed from the individual meanings of their terms (such as the phrase "red tape" meaning bureaucracy). Motivated by this lack of distinction between the frequency and strength of term dependence in IR, we present a principled approach for handling term dependence in queries, using both lexical frequency and semantic evidence. We focus on non-compositional phrases, extending a recent unsupervised model for their detection [21] to IR. Our approach, integrated into ranking using Markov Random Fields [31], yields effectiveness gains over competitive TREC baselines, showing that there is still room for improvement in the very well-studied area of term dependence in IR
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