512 research outputs found
Neutron monitors and muon detectors for solar modulation studies: Interstellar flux, yield function, and assessment of critical parameters in count rate calculations
Particles count rates at given Earth location and altitude result from the
convolution of (i) the interstellar (IS) cosmic-ray fluxes outside the solar
cavity, (ii) the time-dependent modulation of IS into Top-of-Atmosphere (TOA)
fluxes, (iii) the rigidity cut-off (or geomagnetic transmission function) and
grammage at the counter location, (iv) the atmosphere response to incoming TOA
cosmic rays (shower development), and (v) the counter response to the various
particles/energies in the shower. Count rates from neutron monitors or muon
counters are therefore a proxy to solar activity. In this paper, we review all
ingredients, discuss how their uncertainties impact count rate calculations,
and how they translate into variation/uncertainties on the level of solar
modulation (in the simple Force-Field approximation). The main
uncertainty for neutron monitors is related to the yield function. However,
many other effects have a significant impact, at the 5-10\% level on
values. We find no clear ranking of the dominant effects, as some depend on the
station position and/or the weather and/or the season. An abacus to translate
any variation of count rates (for neutron and detectors) to a variation
of the solar modulation is provided.Comment: 28 pages, 16 figures, 9 tables, match accepted version in AdSR (minor
corrections, Dorman (1974,2004,2009) reference textbooks added
Neutron monitors and muon detectors for solar modulation studies: 2. time series
The level of solar modulation at different times (related to the solar
activity) is a central question of solar and galactic cosmic-ray physics. In
the first paper of this series, we have established a correspondence between
the uncertainties on ground-based detectors count rates and the parameter
(modulation level in the force-field approximation) reconstructed from
these count rates. In this second paper, we detail a procedure to obtain a
reference time series from neutron monitor data. We show that we can
have an unbiased and accurate reconstruction (). We also discuss the potential of Bonner spheres spectrometers and muon
detectors to provide time series. Two by-products of this calculation
are updated values for the cosmic-ray database and a web interface to
retrieve and plot from the 50's to today
(\url{http://lpsc.in2p3.fr/crdb}).Comment: 15 pages, 5 figures, 2 tables. AdSR, in press. Web interface to get
modulation parameter phi(t): new tab in http://lpsc.in2p3.fr/crd
Planting a new cherry orchard system: evaluation of economic efficiency
Cherry growing is going through an intense phase of renewal. Innovationâs economic and
financial analysis is crucial for their success and diffusion. The study evaluates three types of planting at
different densities considered, with no covers and three different kinds of shields: a traditional anti-rain
net; a multitasking anti-rain and anti-insect net; a multitasking net with high automation of opening and
closing operations. The best performing plant in economic terms seems the high-density plant (HDP),
followed by the medium density plant (MDP) and then the very high-density plant (VHDP). Higher
density plants reach a shorter payback period. Despite the high investment cost, the quicker breaking
even makes high-density plants less risky. Plants with cover structures determine more secure and stable
production yields, with benefits at the farm level and the whole production chain.
Nonetheless, the shielding structures display a significant quantity of waste during the plantâs life and at
the time of disassembling. It is crucial to progressively increase their environmentally friendly characteristics,
which to date is still poor. The supports and canopies may have a significant salvage value in
the shorter-cycle cherry orchards. Since it is inappropriate to replant the cherry tree in the same plot, it
is essential to study structures that can move from plot to plot. Thus, considerably would improve the
environmental performance and, accordingly, the economic performance of high-density, shorter-cycle
plants
Food chains and value system: the case of potato, fruit, and cheese
The aim of the paper is to analyse patterns of value system sharing along food chains, so to explore the agro-food enterprises capacity to be competitive and sustainable. The research focused on three food chains: potato, fruit, and Grana cheese of Emilia Romagna region. The paper adopts the value system approach. The methodology is aimed at creating a consolidated financial statement for each food chain so to re-create the chain operating profit and identify how this is shared among the different food chain stages. The analysis is carried out on 189 enterprises for the potato chain, 187 for the fruit chain and 203 for the cheese chain. The number of enterprises was invariable over the 5 year 2003-2007, leading to some 2,900 financial statement analysis. The chains analysed show differences. In the potato and fruit chains 35% of value is created by distribution, whereas in cheese chain only 13.6%. Over the five years value decreases 5% in fruit and potato and 9% in cheese. The lack of adequate strategic food chain partnership allows an increasing retail market power over the whole chain at the expenses of the primary sector entailing a declining sustainability for all chain actors.food chain, value system, profitability, potato, fruit, cheese, Agricultural and Food Policy,
Value sharing and food system dynamics for milk, tomato, and cereals food chains
The aim of the paper is to analyse value sharing and food system dynamics of milk, tomato, and cereals food chains, so to explore the agro-food enterprises capacity to be competitive and sustainable. The paper is based on the functionalist approach of Malassis and the notion of the system of the General Systems Theory. The methodology is aimed at creating a consolidated financial statement for each food chain so to re-create the chain value and identify how this is shared among the different food chain stages. The analysis is carried out on primary and secondary data: around 2400 financial statements concerning 480 enterprises from 2003 to 2007 and stakeholders\u2019 interviews. Results show that value is usually created in the processing and distribution stages, to the detriment of the primary sector, and that the retail managing practices tend to impose damaging structural changes on farms whose profitability is at times becoming sustainable only thanks to European subsidies. To conclude, there is evidence of inadequate definition of strategic and network alliance along the chain. Competitiveness is still a concept achieved by single food chain stages against others and food chain internal competition entails a declining sustainability of small farms and enterprises
Information Diversity in Coherent MIMO Radars
In this paper, the concept of information diversity in both the space and frequency domains is investigated for multiple-input multiple-output (MIMO) radars with widely separated antennas. Compared to phased-antenna arrays and multistatic radars, they can exploit more degrees of freedom, allowing them to maximize the information content upon centralized data fusion, thus granting unprecedented target detection and localization capabilities.This analysis proceeds in parallel with the running progresses of microwave photonics (MWP), which could represent, in the near future, a new paradigm for the development of centralized MIMO radar architectures.Thus, understanding the implications of information diversity becomes essential to foretell the system effectiveness in detecting and resolving closely spaced targets, as well as in suppressing sidelobes which may lead to false alarms. Performance metrics are proposed and evaluated to characterize the effects that information diversity has on centralized MIMO radars with widely separated antennas. On the other hand, the proposed methodology could reveal precious for designing the optimum system configuration
Phase coding of RF pulses in photonics-aided frequency-agile coherent radar systems
An innovative optical scheme to generate software-defined phase-modulated radio frequency (RF) pulses with carrier frequency agility from a mode-locked laser (MLL) is proposed. The technique exploits a direct digital synthesizer and a Mach-Zehnder modulator to apply an intermediate frequency modulation to the MLL's modes. The heterodyne detection of the optical signal allows the generation of amplitude- and phase-modulated RF carriers with very high phase stability, suitable for coherent radar applications. Further, a single MLL can be used to generate carriers simultaneously at different frequencies, enabling frequency hopping or multifunctional radars, with no need to increase the complexity of the transmitter. Results show chirped and Barker-coded pulses at around 10 or 40 GHz in a single setup, without any performance degradation while increasing the carrier frequency. The proposed technique allows the practical realization of compressed pulses for coherent radars over a wide carrier frequency range, allowing the development of software-defined radar systems with improved functionalities. © 1965-2012 IEEE
Photonic generation of phase-modulated RF signals for pulse compression techniques in coherent radars
A novel and flexible photonics-based scheme is proposed for generating phase-coded RF pulses suitable for coherent radar systems with pulse compression techniques. After selecting two modes from a mode-locked laser (MLL), the technique exploits an optical in-phase/quadrature modulator driven by a low-sample rate and low-noise direct digital synthesizer to modulate the phase of only one mode. The two laser modes are then heterodyned in a photodiode, and the RF pulse is properly filtered out. The scheme is experimentally validated implementing a 4-bit Barker code and a linear chirp on radar pulses with a carrier frequency of about 25 GHz, starting from an MLL at about 10 GHz. The measures of phase noise, amplitude- and phase-transients, and autocorrelation functions confirm the effectiveness of the scheme in producing compressed radar pulses without affecting the phase stability of the optically generated high-frequency carriers. An increase in the radar resolution from 150 to 37.5 m is calculated. The proposed scheme is capable of flexibly generating software-defined phase-modulated RF pulses with high stability, even at very high carrier frequency, using only a single commercial device with potentials for wideband modulation. It can therefore allow a new generation of high-resolution coherent radars with reduced complexity and cost. © 1983-2012 IEEE
Via-Less Microstrip to Rectangular Waveguide Transition on InP
Indium-Phosphide (InP) is one of the most common materials used for realizing active devices working in the millimeter frequency range. The isotropic etching profile of InP substrates limits the realization of passive devices, thus requiring an expensive and lossy hybrid platform. This paper presents a via-less, cost-effective and efficient solution for InP substrate. By using the proposed planar solution, it is demonstrated that rectangular waveguides can be realized on InP by fabricating a bed of nails structure which acts as a reflecting boundary for an impinging millimeter wave. As a proof of concept, a transition from microstrip to rectangular waveguide structure is realized within H-band (220-320 GHz) with a return loss of -18dB over a bandwidth of 30 GHz
UWB FastlyTunable 0.550 GHz RF Transmitter based on Integrated Photonics
Currently, due to the 6G revolution, applications ranging from communication to sensing are experiencing an increasing and urgent need of software-defined ultra-wideband (UWB) and tunable radio frequency (RF) apparatuses with low size, weight, and power consumption (SWaP). Unfortunately, the coexistence of ultra-wideband and software-defined operation, tunability and low SWaP represents a big issue in the current RF technologies. Recently, photonic techniques have been demonstrated to support achieving the desired features when applied in RF UWB transmitters, introducing extremely wide operation and instantaneous bandwidth, tunable filtering, tunable photonics-based microwave mixing with very high port-to-port isolation, and intrinsic immunity to electromagnetic interferences. Moreover, the recent advances in photonics integration also allow to obtain very compact devices. In this article, to the best of our knowledge, the first example of a complete tunable software-defined RF transmitter with low footprint (i.e. on photonic chip) is presented exceeding the state-of-the-art for the extremely large tunability range of 0.5-50 GHz without any parallelization of narrower-band components and with fast tuning (< 200 s). This first implementation represents a breakthrough in microwave photonics
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