3,939 research outputs found
A Bethe--Salpeter Description of Light Mesons
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
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
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
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
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
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
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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