54,234 research outputs found

    General study of superscaling in quasielastic (e,e)(e,e') and (ν,μ)(\nu,\mu) reactions using the relativistic impulse approximation

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    The phenomenon of superscaling for quasielastic lepton induced reactions at energies of a few GeV is investigated within the framework of the relativistic impulse approximation. A global analysis of quasielastic inclusive electron and charged-current neutrino scattering reactions on nuclei is presented. Scaling and superscaling properties are shown to emerge from both types of processes. The crucial role played by final state interactions is evaluated by using different approaches. The asymmetric shape presented by the experimental scaling function, with a long tail in the region of positive values of the scaling variable, is reproduced when the interaction in the final state between the knockout nucleon and the residual nucleus is described within the relativistic mean field approach. The impact of gauge ambiguities and off-shell effects in the scaling function is also analyzed.Comment: 34 pages, 14 figures, accepted in Phys. Rev. C. Section II has been shortene

    The Mobile Generation: Global Transformations at the Cellular Level

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    Every year we see a new dimension of the ongoing Digital Revolution, which is enabling an abundance of information to move faster, cheaper, in more intelligible forms, in more directions, and across borders of every kind. The exciting new dimension on which the Aspen Institute focused its 2006 Roundtable on Information Technology was mobility, which is making the Digital Revolution ubiquitous. As of this writing, there are over two billion wireless subscribers worldwide and that number is growing rapidly. People are constantly innovating in the use of mobile technologies to allow them to be more interconnected. Almost a half century ago, Ralph Lee Smith conjured up "The Wired Nation," foretelling a world of interactive communication to and from the home that seems commonplace in developed countries today. Now we have a "Wireless World" of communications potentially connecting two billion people to each other with interactive personal communications devices. Widespead adoption of wireless handsets, the increasing use of wireless internet, and the new, on-the-go content that characterizes the new generation of users are changing behaviors in social, political and economic spheres. The devices are easy to use, pervasive and personal. The affordable cell phone has the potential to break down the barriers of poverty and accessibility previously posed by other communications devices. An entire generation that is dependant on ubiquitous mobile technologies is changing the way it works, plays and thinks. Businesses, governments, educational institutions, religious and other organizations in turn are adapting to reach out to this mobile generation via wireless technologies -- from SMS-enabled vending machines in Finland to tech-savvy priests in India willing to conduct prayers transmitted via cell phones. Cellular devices are providing developing economies with opportunities unlike any others previously available. By opening the lines of communication, previously disenfranchised groups can have access to information relating to markets, economic opportunities, jobs, and weather to name just a few. When poor village farmers from Bangladesh can auction their crops on a craigslist-type service over the mobile phone, or government officials gain instantaneous information on contagious diseases via text message, the miracles of mobile connectivity move us from luxury to necessity. And we are only in the early stages of what the mobile electronic communications will mean for mankind. We are now "The Mobile Generation." Aspen Institute Roundtable on Information Technology. To explore the implications of these phenomena, the Aspen Institute Communications and Society Program convened 27 leaders from business, academia, government and the non-profit sector to engage in three days of dialogue on related topics. Some are experts in information and communications technologies, others are leaders in the broader society affected by these innovations. Together, they examined the profound changes ahead as a result of the convergence of wireless technologies and the Internet. In the following report of the Roundtable meeting held August 1-4, 2006, J. D. Lasica, author of Darknet and co-founder of Ourmedia.org, deftly sets up, contextualizes, and captures the dialogue on the impact of the new mobility on economic models for businesses and governments, social services, economic development, and personal identity

    MANURE HANDLING COSTS AND THE COMPETITIVENESS OF PORK PRODUCTION

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    Simulations of possible regulation-related manure handling costs are compared to base scenario costs for the three main regions and phases of modern hog production over widely varying scale levels. The base scenario confirms previous research suggesting that in Iowa net benefits occur at small scale levels from injecting slurry stored in an outside earthern basin for corn production using a phosphorus standard. Increased transportation costs result in Iowa costs surpassing costs in Utah at higher scale levels, while costs in North Carolina are highest at all scale levels. Requiring systems to be lined and covered in Iowa and North Carolina results in proportionately greater increased costs per head in North Carolina. Adding the requirement that manure be applied according to a phosphorus standard increases costs proportionately more in Iowa at larger scale levels, but not at all at the smallest scale, and costs in Iowa surpass those in North Carolina at the largest scale. The results of all scenarios underscore the advantages enjoyed by Utah in manure handling because scales of operation there are among the largest.Livestock Production/Industries,

    Nonlinear stability and ergodicity of ensemble based Kalman filters

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    The ensemble Kalman filter (EnKF) and ensemble square root filter (ESRF) are data assimilation methods used to combine high dimensional, nonlinear dynamical models with observed data. Despite their widespread usage in climate science and oil reservoir simulation, very little is known about the long-time behavior of these methods and why they are effective when applied with modest ensemble sizes in large dimensional turbulent dynamical systems. By following the basic principles of energy dissipation and controllability of filters, this paper establishes a simple, systematic and rigorous framework for the nonlinear analysis of EnKF and ESRF with arbitrary ensemble size, focusing on the dynamical properties of boundedness and geometric ergodicity. The time uniform boundedness guarantees that the filter estimate will not diverge to machine infinity in finite time, which is a potential threat for EnKF and ESQF known as the catastrophic filter divergence. Geometric ergodicity ensures in addition that the filter has a unique invariant measure and that initialization errors will dissipate exponentially in time. We establish these results by introducing a natural notion of observable energy dissipation. The time uniform bound is achieved through a simple Lyapunov function argument, this result applies to systems with complete observations and strong kinetic energy dissipation, but also to concrete examples with incomplete observations. With the Lyapunov function argument established, the geometric ergodicity is obtained by verifying the controllability of the filter processes; in particular, such analysis for ESQF relies on a careful multivariate perturbation analysis of the covariance eigen-structure.Comment: 38 page

    Performance assessment of tariff-based air source heat pump load shifting in a UK detached dwelling featuring phase change-enhanced buffering

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    Using a detailed building simulation model, the amount of thermal buffering, with and without phase change material (PCM), needed to time-shift an air source heat pump's operation to off-peak periods, as defined by the UK 'Economy 10' tariff, was investigated for a typical UK detached dwelling. The performance of the buffered system was compared to the case with no load shifting and with no thermal buffering. Additionally, the load shifting of a population of buffered heat pumps to off-peak periods was simulated and the resulting change in the peak demand on the electricity network was assessed. The results from this study indicate that 1000 L of hot water buffering or 500 L of PCM-enhanced hot water buffering was required to move the operation of the heat pump fully to off-peak periods, without adversely affecting the provision of space heating and hot water for the end user. The work also highlights that buffering and load shifting increased the heat pump's electrical demand by over 60% leading to increased cost to the end user and increased CO2 emissions (depending on the electricity tariff applied and time varying CO2 intensity of the electricity generation mix, respectively). The study also highlights that the load-shifting of populations of buffered heat pumps wholly to off-peak periods using crude instruments such as tariffs increased the peak loading on the electrical network by over 50% rather than reducing it and that careful consideration is needed as to how the load shifting of a group of heat pumps is orchestrated

    The Infrared Nucleus of the Wolf-Rayet Galaxy Henize 2-10

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    We have obtained near-infrared images and mid-infrared spectra of the starburst core of the dwarf Wolf-Rayet galaxy He 2-10. We find that the infrared continuum and emission lines are concentrated in a flattened ellipse 3-4'' or 150 pc across which may show where a recent accretion event has triggered intense star formation. The ionizing radiation from this cluster has an effective temperature of 40,000 K, corresponding to 30M30M_\odot stars, and the starburst is 0.51.5×1070.5-1.5 \times 10^7 years old.Comment: 17 pages Latex, 7 postscript figures, 1 postscript table, accepted to A

    Workshop on evaluating personal search

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    The first ECIR workshop on Evaluating Personal Search was held on 18th April 2011 in Dublin, Ireland. The workshop consisted of 6 oral paper presentations and several discussion sessions. This report presents an overview of the scope and contents of the workshop and outlines the major outcomes

    A filter spectrometer concept for facsimile cameras

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    A concept which utilizes interference filters and photodetector arrays to integrate spectrometry with the basic imagery function of a facsimile camera is described and analyzed. The analysis considers spectral resolution, instantaneous field of view, spectral range, and signal-to-noise ratio. Specific performance predictions for the Martian environment, the Viking facsimile camera design parameters, and a signal-to-noise ratio for each spectral band equal to or greater than 256 indicate the feasibility of obtaining a spectral resolution of 0.01 micrometers with an instantaneous field of view of about 0.1 deg in the 0.425 micrometers to 1.025 micrometers range using silicon photodetectors. A spectral resolution of 0.05 micrometers with an instantaneous field of view of about 0.6 deg in the 1.0 to 2.7 micrometers range using lead sulfide photodetectors is also feasible
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