921 research outputs found
Addressing the Challenges of Extension and Advisory Services in Uganda: The Grameen Foundation’s Community Knowledge Worker Program
Diffusion of agricultural knowledge is vital to food security and capacity building in the developing world. Many developing world farmers still do not have access to extension and advisory services (EAS), and poor agricultural practices still exist. Diffusion of agricultural knowledge could lead to improved productivity, higher obtained prices, and increased incomes, but it is made more difficult in the developing world by poor infrastructure, high illiteracy rates, and too few extension agents. The rapid spread of mobile phones throughout the developing world has sparked many EAS programs that incorporate mobile technologies. Although they offer great potential for knowledge diffusion, research has not yet identified strong positive impacts of mobile technology-based interventions. The Grameen Foundation’s Community Knowledge Worker (CKW) program provides model farmers in Ugandan communities with training and smartphones that are linked to a database with actionable agricultural information. The model farmers (CKWs) interact with their neighbors to share the information in the database. This relatively inexpensive program differs from other EAS initiatives by using a large number of lightly trained “extension agents” and mobile technology that provides those agents with easy-to-access information they share with and help interpret for the farmers in their communities. The program also incorporates ongoing data collection via the smartphones, allowing for a two-way exchange of information and enabling constant monitoring. Two recent studies have shown this program to have positive impacts. An ongoing randomized control trial promises to offer a comprehensive impact assessmen
Molecular identification and seasonal monitoring of phytoplasmas infecting Croatian grapevines
Phytoplasmas of the 16S rRNA RFLP group XII-A (stolbur) have been detected with tests carried out 4 times from September 1997 to April 1998 in Croatian Pinot gris grapevines showing yellows symptoms. This is the first report on the presence of stolbur phytoplasma in Croatian grapevines. Two asymptomatic vineyard weeds, Taraxacum officinale Web. and Polygonum lapathifolium L. showed the presence of the same prokaryotes
Data driven theory for knowledge discovery in the exact sciences with applications to thermonuclear fusion
In recent years, the techniques of the exact sciences have been applied to the analysis of increasingly complex and non-linear systems. The related uncertainties and the large amounts of data available have progressively shown the limits of the traditional hypothesis driven methods, based on first principle theories. Therefore, a new approach of data driven theory formulation has been developed. It is based on the manipulation of symbols with genetic computing and it is meant to complement traditional procedures, by exploring large datasets to find the most suitable mathematical models to interpret them. The paper reports on the vast amounts of numerical tests that have shown the potential of the new techniques to provide very useful insights in various studies, ranging from the formulation of scaling laws to the original identification of the most appropriate dimensionless variables to investigate a given system. The application to some of the most complex experiments in physics, in particular thermonuclear plasmas, has proved the capability of the methodology to address real problems, even highly nonlinear and practically important ones such as catastrophic instabilities. The proposed tools are therefore being increasingly used in various fields of science and they constitute a very good set of techniques to bridge the gap between experiments, traditional data analysis and theory formulation
Compact x-ray source based on burst-mode inverse Compton scattering at 100 kHz
A design for a compact x-ray light source (CXLS) with flux and brilliance
orders of magnitude beyond existing laboratory scale sources is presented. The
source is based on inverse Compton scattering of a high brightness electron
bunch on a picosecond laser pulse. The accelerator is a novel high-efficiency
standing-wave linac and RF photoinjector powered by a single ultrastable RF
transmitter at x-band RF frequency. The high efficiency permits operation at
repetition rates up to 1 kHz, which is further boosted to 100 kHz by operating
with trains of 100 bunches of 100 pC charge, each separated by 5 ns. The entire
accelerator is approximately 1 meter long and produces hard x-rays tunable over
a wide range of photon energies. The colliding laser is a Yb:YAG solid-state
amplifier producing 1030 nm, 100 mJ pulses at the same 1 kHz repetition rate as
the accelerator. The laser pulse is frequency-doubled and stored for many
passes in a ringdown cavity to match the linac pulse structure. At a photon
energy of 12.4 keV, the predicted x-ray flux is
photons/second in a 5% bandwidth and the brilliance is in pulses with RMS pulse
length of 490 fs. The nominal electron beam parameters are 18 MeV kinetic
energy, 10 microamp average current, 0.5 microsecond macropulse length,
resulting in average electron beam power of 180 W. Optimization of the x-ray
output is presented along with design of the accelerator, laser, and x-ray
optic components that are specific to the particular characteristics of the
Compton scattered x-ray pulses.Comment: 25 pages, 24 figures, 54 reference
Detection of Causal Relations in Time Series Affected by Noise in Tokamaks Using Geodesic Distance on Gaussian Manifolds
Modern experiments in Magnetic Confinement Nuclear Fusion can produce Gigabytes of
data, mainly in form of time series. The acquired signals, composing massive databases, are typically
affected by significant levels of noise. The interpretation of the time series can therefore become
quite involved, particularly when tenuous causal relations have to be investigated. In the last years,
synchronization experiments, to control potentially dangerous instabilities, have become a subject
of intensive research. Their interpretation requires quite delicate causality analysis. In this paper,
the approach of Information Geometry is applied to the problem of assessing the effectiveness of
synchronization experiments on JET (Joint European Torus). In particular, the use of the Geodesic Distance on Gaussian Manifolds is shown to improve the results of advanced techniques such as Recurrent Plots and Complex Networks, when the noise level is not negligible. In cases affected by particularly high levels of noise, compromising the traditional treatments, the use of the Geodesic Distance on Gaussian Manifolds allows deriving quite encouraging results. In addition to consolidating conclusions previously quite uncertain, it has been demonstrated that the proposed approach permit to successfully analyze signals of discharges which were otherwise unusable, therefore salvaging the interpretation of those experiments.EURATOM 63305
OM: One God Universal Garland of Offerings #6: Om ityetad Aksharam idam Sarvam--Mandukya
A collection of articles exploring Hindu spirituality and theology
Developement of real time diagnostics and feedback algorithms for JET in view of the next step
Real time control of many plasma parameters will be an essential aspect in
the development of reliable high performance operation of Next Step Tokamaks.
The main prerequisites for any feedback scheme are the precise real-time
determination of the quantities to be controlled, requiring top quality and
highly reliable diagnostics, and the availability of robust control algorithms.
A new set of real time diagnostics was recently implemented on JET to prove the
feasibility of determining, with high accuracy and time resolution, the most
important plasma quantities. With regard to feedback algorithms, new
model–based controllers were developed to allow a more robust control of
several plasma parameters. Both diagnostics and algorithms were successfully
used in several experiments, ranging from H-mode plasmas to configuration with
ITBs. Since elaboration of computationally heavy measurements is often
required, significant attention was devoted to non-algorithmic methods like
Digital or Cellular Neural/Nonlinear Networks. The real time hardware and
software adopted architectures are also described with particular attention to
their relevance to ITER.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004,
Nice (France
Conceptual design of the Gas Injection and Vacuum System for DTT NBI
The Divertor Tokamak Test (DTT) is a new experimental facility whose
construction is starting in Frascati, Rome, Italy; its main goals are improving
the understanding of plasma-wall interactions and supporting the development of
ITER and DEMO. DTT will be equipped with a Neutral Beam Injector (NBI) based on
negative deuterium ions, designed to inject 10 MW of power to the tokamak.
A fundamental system for the good operations of the DTT NBI will be its Gas
injection and Vacuum System (GVS). Indeed, the efficiency of the entire NBI
strongly depends on the good performance of its GVS.
The GVS for DTT NBI will be composed of two systems working in parallel: a
grounded section connected to the main vacuum vessel, and a high voltage part
connected to the ion source vessel and working at -510 kV voltage. The grounded
part will feature a fore vacuum system (given by screw and roots pumps) plus a
high vacuum system based on turbo-molecular pumps located on the side walls of
the vessel and Non-Evaporable Getter (NEG) pumps located inside the vessel on
the upper and lower surfaces. On the other hand, the high voltage part will
feature a fore vacuum system (given by two compact screw pumps mounted on the
external surface for the ion source vessel) plus a high vacuum system based on
turbo-molecular pumps also located on the sidewalls of the ion source vessel. A
dedicated deuterium gas injection will feed the process gas to the ion source
and the neutralizer.
This paper gives a description of the conceptual design of the GVS for DTT
NBI, and of the procedure followed to optimize this system considering the
operational requirements and the other constraints of the DTT NBI.Comment: 12 pages, 8 figures, presented at the SOFT 2022 conferenc
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