142,730 research outputs found
Il fiume Olona e la seta (XVIII-XIX sec.)
No full textNello studio si affronta il processo di industrializzazione della Valle Olona. Tale analisi ci permette di comprendere come questa area sia stata plasmata dagli insediamenti industriali, che hanno agito progressivamente sull’organizzazione urbana e sociale e come all’inizio di questa trasformazione territoriale sia stato importante lo scambio di informazioni, il tessere una rete di conoscenze che ha influenzato lo sviluppo architettonico delle prime strutture seriche
Patents and Research Tools in a Schumpeterian Growth Model with Sequential Innovation
Get PDFIn the standard quality-ladder growth models, R&D firms undertake independent innovation processes to discover ideas whose value immediately transfers into tradeable applications. Here the standard multisector neo-Schumpeterian growth theory is extended by decomposing product innovation into a two-stage uncertain research activity. I compare the general equilibrium innovative performance of an economy where early-stages scientific results are patentable with the general equilibrium innovative performance with unpatentable basic ideas freely disseminated by public research institutions (universities). I show that the widely documented increasing complexity experienced in applied R&D magnifies the public basic R&D inefficiencies and suggests the patentability of research tools.
Economic impacts of high labour cost and herbicide resistance for the management of annual barnyardgrass (Echinochloa crus-galli) in rice production in the Philippines
Get PDFImplications of increasing labour cost and development of herbicide resistance for profitable weed management in Philippine rice farming systems are investigated. The study employs RIMPhil (Resistance and Integrated Management in the Philippines), a bioeconomic simulation model developed to provide a comprehensive assessment of integrated weed management programmes for the control of annual barnyardgrass (Echinochloa crus-galli) in rice crops. Results indicate that herbicide application will become increasingly economically attractive, relative to manual weeding, as labour cost increases. This is important since urban migration in the Philippines continues to increase the scarcity of rural labour. Results also show that the onset of herbicide resistance results in substantial losses in farm profit. It may be worthwhile for farmers to take management actions to prevent or delay the onset of herbicide resistance, provided that these changes are effective and not too costly. The study highlights the complexity of decision making about integrated weed management on rice farms in the Philippines.Barnyardgrass, Bioeconomic model, Herbicide resistance, Integrated weed management, Rice production, Crop Production/Industries, Farm Management, Research and Development/Tech Change/Emerging Technologies,
Seed production of barnyardgrass (Echinochloa crus-galli) in response to time of emergence in cotton and rice
Get PDFThe spread of herbicide resistance in barnyardgrass (Echinochloa crus-galli (L.) Beauv.) poses a serious threat to crop production in the southern United States. A thorough knowledge of the biology of barnyardgrass is fundamental for designing effective resistance-management programmes. In the present study, seed production of barnyardgrass in response to time of emergence was investigated in cotton and rice, respectively, in Fayetteville and Rohwer, Arkansas, over a 2-year period (2008–09). Barnyardgrass seed production was greater when seedlings emerged with the crop, but some seed production was observed even if seedlings emerged several weeks after crop emergence. Moreover, barnyardgrass seed production was highly variable across environments. When emerging with the crop (0 weeks after crop emergence (WAE)), barnyardgrass produced c. 35 500 and 16 500 seeds/plant in cotton, and c. 39 000 and 2900 seeds/plant in rice, in 2008 and 2009, respectively. Seed production was observed when seedlings emerged up to 5 WAE (2008) or 7 WAE (2009) in cotton and up to 5 WAE (2008, 2009) in rice; corresponding seed production was c. 2500 and 1500 seeds/plant in cotton, and c. 14 700 and 110 seeds/plant in rice, in 2008 and 2009, respectively. The results suggest that cultural approaches that delay the emergence of barnyardgrass or approaches that make the associated crop more competitive will be useful in integrated management programmes. In the context of herbicide resistance management, it may be valuable to prevent seed return to the seedbank, irrespective of cohorts. The findings are vital for parameterizing herbicide resistance simulation models for barnyardgrass
Bose-Fermi mixtures with pairing
Get PDFI will review recent work by us on the properties of Bose-Fermi mixtures with a tunable pairing interaction
between bosons and fermions. A many-body diagrammatic approach, able to describe the condensed phase of
a Bose-Fermi mixture from weak to strong boson-fermion couplings, will be presented [1]. This approach will
be validated by comparing it with previous [2] and new dedicated fixed-node diffusion Monte Carlo
calculations. By using both methods, a universal behavior of the condensate fraction and bosonic momentum
distribution with respect to the boson concentration is found in an extended range of boson-fermion couplings
and concentrations. For vanishing boson density, the bosonic condensate fraction reduces to the quasiparticle
weight Z of the Fermi polaron studied in the context of polarized Fermi gases, unifying in this way two
apparently unrelated quantities. Finally, I will discuss an interesting effect occurring in the molecular limit of
the boson- fermion coupling, where the condensation is completely suppressed [3]. This phenomenon is an
indirect effect on bosons of the Pauli exclusion principle acting on fermions, and is the counterpart in BoseFermi
mixtures of the so called “Sarma phase” discussed for polarized Fermi gases.
[1] A. Guidini, G. Bertaina, D. Galli, and P. Pieri, arXiv:1412.2542.
[2] G. Bertaina, E. Fratini, S. Giorgini, and P. Pieri, Phys. Rev. Lett. 110, 115303 (2013).
[3] A. Guidini, G. Bertaina, E. Fratini, and P. Pieri, Phys. Rev. A 89, 023634 (2014)
New beamwidth formulas for 1-D leaky-wave antennas: A review
No full textIn this work, we comprehensively review the recent developments made in the context of the beamwidth evaluation in finite-aperture one-dimensional (1-D) leaky-wave antennas (LWAs). Indeed, the beam properties of 1-D LWAs are commonly evaluated assuming an infinite aperture, and only very recently the effect of the aperture truncation has been accounted for. However, the effects of the aperture truncation on 1-D unidirectional LWAs are different from those on endfire 1-D LWAs, and even more different from those on 1-D bidirectional LWAs. Each case deserves its own analysis, and this paper provides general formulas for the evaluation of such effects
Radiating properties of 1-D bidirectional leaky-wave antennas
No full textWe analyze radiation from bidirectional one-dimensional leaky-wave antennas (1-D LWAs), from an original perspective. As is known, when the aperture is infinite, the radiation pattern changes considerably for certain combinations of the phase and the attenuation constants. These specific values identify the boundaries between different radiating regimes. In this work, we thoroughly explain the evolution of the beam through all the radiating regimes, and then evaluate its beamwidth with original analytical formulas. The relevant case of a finite-size aperture is considered as well. In this case, we show that the boundaries between the radiating regimes change as the radiation efficiency changes. The evolution of these boundaries as a function of the radiation efficiency is found by numerical means. These results allows for a rigorous and comprehensive description of the radiating behavior of practical 1-D bidirectional LWAs
General formulas for the beam properties of 1-D bidirectional leaky-wave antennas
No full textIn this paper, we analyze the beam properties of bidirectional 1-D leaky-wave antennas (1-D LWAs). Specifically, it is found that, even in the infinite-aperture case, the beam properties considerably change for certain combinations of the phase and the attenuation constants, and different radiation regimes are identified here. New analytic formulas are provided to exactly evaluate the beamwidth of an infinite 1-D bidirectional LWA operating in any radiating regime. However, when the antenna truncation is accounted for, the boundaries between the radiating regimes change as the radiation efficiency changes. Analytic formulas are, therefore, provided to accurately calculate such boundaries for any practical radiation efficiency. The interesting case of a finite-length bidirectional 1-D LWA radiating at broadside is then extensively discussed. With respect to previous beamwidth formulas found in the literature, the new formulas take into account the finiteness of the aperture, thus providing more useful and reliable results, especially in cases when the aperture truncation considerably affects the radiation efficiency. The numerical results corroborate the accuracy of the proposed expressions. These new formulas not only significantly improve the accuracy of the existing ones but also lay the groundwork for the analysis of the beamwidth properties of the important case of 2-D LWAs
Accurate formulas for the beamwidth of 1-D bidirectional leaky-wave antennas
No full textIn this work, we accurately evaluate the beamwidth of one-dimensional (1-D) bidirectional leaky-wave antennas (LWAs) radiating at broadside. Indeed, existing formulas neglect the effect of the aperture truncation, which affects the exact value of the beamwidth for practical realizations of 1-D LWAs. By exploiting a well-established theoretical framework, we find an approximate, but still accurate analytical formula for evaluating the beamwidth of finite-length 1-D bidirectional LWAs radiating at broadside. The comparison with numerical results confirm the accuracy of the proposed formula, whereas the comparison with previous formulas confirm its relevance for accurate LWA design
Beamwidth evaluation of finite-length 1- D bidirectional leaky-wave antennas
Get PDFIn this work we analyze the beamwidth properties of one-dimensional (1-D) bidirectional leaky-wave antennas (LWAs) when the antenna is pointing close to broadside. Existing formulas neglect the effect of the aperture truncation, which affects the exact value of the beamwidth for practical realizations of 1-D LWAs. Using a rigorous theoretical framework, we find a transcendental beamwidth equation, whose numerical solution furnishes the exact value of the beamwidth for finite-length 1-D bidirectional LWAs. Numerical results confirm that the aperture truncation considerably affects the beamwidth properties, especially for limited efficiencies
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