3,906 research outputs found

    A Bethe--Salpeter Description of Light Mesons

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    We present a covariant approach to describe the low--lying scalar, pseudoscalar, vector and axialvector mesons as quark--antiquark bound states.This approach is based on an effective interaction modeling of the non--perturbative structure of the gluon propagator that enters the quark Schwinger--Dyson and meson Bethe--Salpeter equations. We extract the meson masses and compute the pion and kaon decay constants. We obtain a quantitatively correct description for pions, kaons and vector mesons while the calculated spectra of scalar and axialvector mesons suggest that their structure is more complex than being quark--antiquark bound states.Comment: Talk presented by HW at the international Scalar Meson Workshop, Utica, NY, May 2003; 12 pages, uses aip style file

    Mobile Phone Power Amplifier Linearity and Efficiency Enhancement Using Digital Predistortion

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    The new generation mobile communication systems using spectrum efficient linear modulation schemes (QPSK,8PSK,QAM)need linear power amplifiers in the transmission path to have good ACPR and EVM values. Linearization methods can be used to increase the linearity of the power amplifiers (PA).However,it is not reasonable o use complicated,power consuming and high cost systems. This paper presents a digital predistortion implementation for WCDMA signals using an FPGA (Field Programmable Gate Array)as DSP and investigates the application of this system in handsets.The method applied requires minimum change in the conventional transmitter path configuration but considerable PAE improvement can be achieved

    Autoplot: A browser for scientific data on the web

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    Autoplot is software developed for the Virtual Observatories in Heliophysics to provide intelligent and automated plotting capabilities for many typical data products that are stored in a variety of file formats or databases. Autoplot has proven to be a flexible tool for exploring, accessing, and viewing data resources as typically found on the web, usually in the form of a directory containing data files with multiple parameters contained in each file. Data from a data source is abstracted into a common internal data model called QDataSet. Autoplot is built from individually useful components, and can be extended and reused to create specialized data handling and analysis applications and is being used in a variety of science visualization and analysis applications. Although originally developed for viewing heliophysics-related time series and spectrograms, its flexible and generic data representation model makes it potentially useful for the Earth sciences.Comment: 16 page

    Energies of Quantum QED Flux Tubes

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    In this talk I present recent studies on vacuum polarization energies and energy densities induced by QED flux tubes. I focus on comparing three and four dimensional scenarios and the discussion of various approximation schemes in view of the exact treatment.Comment: 9 pages latex, Talk presented at the QFEXT 05 workshop in Barcelona, Sept. 2005. To appear in the proceeding

    Enterprising Rural Families: Making It Work

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    Enterprising Rural Families (ERFTM) is an international course for the rural family in business. ERFTM teaches a process of finding success, resilience and satisfaction for rural families engaged in enterprises; including agriculture. Instructors from the United States, Canada and Australia have teamed together to offer this course that focuses on the three main components of a family business: individuals, the family unit and the business enterprise. This course also allows families in business to increase their awareness of cultural differences and similarities and improve their understanding of global issues. The course consists of written presentations, online chat sessions, threaded discussions, readings, videos, case studies and individual projects. Using these mechanisms, the online interaction provides rural families with both the tools and skills to resolve immediate family business issues and build a profitable business for the future.Consumer/Household Economics, Farm Management,

    Soliton Models for the Nucleon and Predictions for the Nucleon Spin Structure

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    In these lectures the three flavor soliton approach for baryons is reviewed. Effects of flavor symmetry breaking in the baryon wave--functions on axial current matrix elements are discussed. A bosonized chiral quark model is considered to outline the computation of spin dependent nucleon structure functions in the soliton picture.Comment: 12 pages, Lectures presented at the Advanced Study Institute Symmetry and Spin, Prague, 2001, to appear in the proceedings. References correcte

    A comparison of assistance used by field-dependent and field-independent adults engaged in self-planned learning

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    The purpose of this investigation was to compare field-dependent and field-independent adult learners on the importance of assistance in self-planned learning. Fifty-seven adult learners were interviewed concerning the extent of their self-planned learning efforts. They were given the Embedded Figures Test, an instrument identifying tendencies toward field-dependent or field-independent cognitive style. They were also asked to complete three, researcher designed checklists examining the importance of assistance to self-planned learning;Checklist one listed 20 sources of assistance learners use in self-planned learning. Ten sources of assistance were categorized as human sources (involving interaction with people) and ten were categorized as nonhuman (interaction with materials or inanimate objects). Checklists two and three studied the types of assistance adults receive from human and nonhuman resources during their learning efforts;The study failed to reject eight hypotheses and rejected two. Field-dependent learners did report that nonhuman sources of assistance were more important to their learning than was reported by field-independent learners. The importance of nonhuman sources of assistance was found to be a predictor of reported satisfaction with self-planned learning. No significant difference between field-dependent and field-independent learners was found on the importance of human or nonhuman assistance during the process of choosing, planning, or implementing self-planned learning;The study identified areas needing further investigation including: a more precise examination of the behavior of self-planned learners when engaged in choosing, planning, and implementing learning projects; further study of those sources of assistance that aid or hinder self-planned learning; a more detailed comparison of the learning behavior of those adults possessing strong field-dependent or field-independent cognitive tendencies in lieu of studying the behavior of adults with varying degrees of field-dependence or field-independence
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