940 research outputs found
Partial nutrient balances from agronomic and economic viewpoints: the case of corn cultivation in the acid upland soils of Isabela, the Philippines
Soil propertiesMaizeEconomic aspects
High energy DVCS on a photon and related meson exclusive production
In this work we estimate the differential cross section for the high energy
deeply virtual Compton scattering on a photon target within the QCD
dipole-dipole scattering formalism. For the phenomenology, a saturation model
for the dipole-dipole cross section for two photon scattering is considered.
Its robustness is supported by good description of current accelerator data. In
addition, we consider the related exclusive vector meson production processes.
This analysis is focused on the light and meson production, which
produce larger cross sections. The phenomenological results are compared with
the theoretical calculation using the CD BFKL approach.Comment: 6 pages, 5 figures. Version to be published in Physical Review
Model-based design for self-sustainable sensor nodes
Long-term and maintenance-free operation is a critical feature for large-scale deployed battery-operated sensor nodes. Energy harvesting (EH) is the most promising technology to overcome the energy bottleneck of today’s sensors and to enable the vision of perpetual operation. However, relying on fluctuating environmental energy requires an application-specific analysis of the energy statistics combined with an in-depth characterization of circuits and algorithms, making design and verification complex. This article presents a model-based design (MBD) approach for EH-enabled devices accounting for the dynamic behavior of components in the power generation, conversion, storage, and discharge paths. The extension of existing compact models combined with data-driven statistical modeling of harvesting circuits allows accurate offline analysis, verification, and validation. The presented approach facilitates application-specific optimization during the development phase and reliable long-term evaluation combined with environmental datasets. Experimental results demonstrate the accuracy and flexibility of this approach: the model verification of a solar-powered wireless sensor node shows a determination coefficient () of 0.992, resulting in an energy error of only -1.57 % between measurement and simulation. Compared to state-of-practice methods, the MBD approach attains a reduction of the estimated state-of-charge error of up to 10.2 % in a real-world scenario. MBD offers non-trivial insights on critical design choices: the analysis of the storage element selection reveals a 2–3 times too high self-discharge per capacity ratio for supercapacitors and a peak current constrain for lithium-ion polymer batteries
A New Sub-Period-Minimum Cataclysmic Variable With Partial Hydrogen Depletion And Evidence Of Spiral Disk Structure
We present time-resolved spectroscopy and photometry of CSS 120422:111127+571239 (=SBS 1108+574), a recently discovered SU UMa-type dwarf nova whose 55 minute orbital period is well below the cataclysmic variable (CV) period minimum of similar to 78 minutes. In contrast with most other known CVs, its spectrum features He I emission of comparable strength to the Balmer lines, implying a hydrogen abundance less than 0.1 of long-period CVs-but still at least 10 times higher than that in AM CVn stars. Together, the short orbital period and remarkable helium-to-hydrogen ratio suggest that mass transfer in CSS 120422 began near the end of the donor star's main-sequence lifetime, meaning that this CV is a strong candidate progenitor of an AM CVn system as described by Podsiadlowski et al. Moreover, a Doppler tomogram of the Ha line reveals two distinct regions of enhanced emission. While one is the result of the stream-disk impact, the other is probably attributable to spiral disk structure generated when material in the outer disk achieves a 2:1 orbital resonance with respect to the donor.NSF AST-1211196, AST-9987045Department of Physics at the University of Notre DameNSF Telescope System Instrumentation Program (TSIP)Ohio Board of RegentsOhio State University Office of ResearchAstronom
Saturation Physics in Ultra High Energy Cosmic Rays: Heavy Quark Production
In this work we estimate the heavy quark production in the interaction of
ultra high energy cosmic rays in the atmosphere, considering that the primary
cosmic ray is a proton or a photon. At these energies the saturation momentum
Q_{sat}^2 stays above the hard scale \mu_c^2=4m_c^2, implying charm production
probing the saturation regime. In particular, we show that the ep HERA data
presents a scaling on \tau_c = (Q^2+\mu_c^2)/Q_{sat}^2. We derive our results
considering the dipole picture and the Color Glass Condensate formalism, which
one shows to be able to describe the heavy quark production in photon-proton
and proton-proton collisions. Nuclear effects are considered in computation of
cross sections for scattering on air nuclei. Implications on the flux of prompt
leptons at the earth are analyzed and a large suppression is predicted.Comment: 18 pages, 10 figures, 2 tables. Version to be published in JHE
Intraventricular Thrombi with Systemic Embolization: Two Clinical Cases
A formação de trombos intraventriculares é um complicação frequente nos doentes com miocardiopatia dilatada e enfarte agudo do miocárdio, sendo o risco de embolização sistémica muito variável em função da patologia subjacente e características subjacentes dos trombos. Os autores descrevem dois casos clínicos relativos a dois doentes internados no mesmo dia com trombos intraventriculares, volumosos, protuberantes e muito móveis, no contexto de miocardiopatia dilatada e enfarte agudo do miocárdio, que embolizaram para os membros inferiores. Salientam a importância da ecocardiografia no diagnóstico, caracterização morfológica inicial e controlo evolutivo dos trombos intraventriculares, aspectos fundamentais na avaliação do risco embólico. Na ausência de recomendações específicas quanto às opções terapêuticas – anticoagulação, trombólise ou remoção cirúrgica, os autores sublinham a necessidade de avaliação individualizada, «caso a caso», tendo em conta o risco embólico, hemorrágico, e cirúrgico
Information Technology and the Search for Organizational Agility: A Systematic Review with Future Research Possibilities
Organizations are increasingly turning to information technology (IT) to help them respond to unanticipated environmental threats and opportunities. In this paper, we introduce a systematic review of the literature on IT-enabled agility, helping to establish the boundary between what we know and what we don’t know. We base our review on a wide body of literature drawn from the AIS Basket of Eight IT journals, a cross-section of non-Basket journals, IT practitioner outlets, and premier international IS conferences. We review the use of different theoretical lenses used to investigate the relationship between IT and organizational agility and how the literature has conceptualized agility, its antecedents, and consequences. We also map the evolution of the literature through a series of stages that highlight how researchers have built on previous work. Lastly, we discuss opportunities for future research in an effort to close important gaps in our understanding
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