6,277 research outputs found
Improved photocatalytic properties of doped titanium-based nanometric oxides
Photocatalysis is considered one of the most promising technologies for applications in the environmental field especially in the abatement of water-soluble organic pollutants. In this field, titanium dioxide nanoparticles have drawn much attention recently; however, the use of this oxide presents some limitation since it allows to obtain high photoresponse and degradation efficiency only under UV light irradiation, that represents the 3 to 4% of the solar radiation, so preventing its environmental large-scale applications under diffuse daylight. In this work the photocatalytic efficiencyoftitanium-based oxides systems containing alkaline earth metals such as barium and strontium, prepared by a simple sol-gel method was investigated, evaluating the degradation of methylene blue as model compound under UV and visible light irradiation. The results were compared with those obtained with Degussa P25 titanium dioxide. The achieved degradation percentage of methylene blue are very promising showing that under visible light irradiation it is possible to obtain a maximum dye removal percentage ~ 50 % higher than that obtained with the Degussa P25
Quantum Dynamics of the Hubbard-Holstein Model in Equilibrium and Non-Equilibrium: Application to Pump-Probe Phenomena
The spectral response and physical features of the 2D Hubbard-Holstein model
are calculated both in equilibrium at zero and low chemical dopings, and after
an ultra short powerful light pulse, in undoped systems. At equilibrium and at
strong charge-lattice couplings, the optical conductivity reveals a 3-peak
structure in agreement with experimental observations. After an ultra short
pulse and at nonzero electron-phonon interaction, phonon and spin subsystems
oscillate with the phonon period fs. The decay time of the
phonon oscillations is about 150-200 fs, similar to the relaxation time of the
charge system. We propose a criterion for observing these oscillations in high
compounds: the time span of the pump light pulse has to be
shorter than the phonon oscillation period .Comment: 4 pages, 4 figure
Steam reforming of model compounds from biomass fermentation over nanometric ruthenium modified nickel-lanthanum perovskites catalysts
Nanometric ruthenium-modified LaNiO3 perovskites prepared by coprecipitation method in aqueous and non-aqueous solvents were tested as catalysts in the steam reforming of butanol, acetone and ethanol and their mixture, named ABE, usually produced by fermentation. ABE is potentially of great interest for hydrogen production, notwithstanding the strong tendency of this mixture of oxygenated compounds to produce coke in the steam reforming conditions. The tested catalyst showed high feed conversions with improved stability
Preferences of informal carers on technology packages to support meal production by people living with dementia, elicited from personalised AT and ICT product brochures
Assistive technology (AT) can help support the continued independence of people living with dementia, supported by informal carers. Opinions and preferences of informal carers towards a range of assistive and digital information and communication technologies (ICT) to support food purchase and menu selection, including navigation and online shopping, and safe meal-making by individuals living with dementia were investigated. General attitudes and experiences with assistive technologies were first probed by means of a focus group with carers (n = 6), organised through the Alzheimer’s Society in Nottingham, England. A series of AT/ICT product brochures were then produced, describing packages of technologies to enable meal production. Task-specific questions were asked of carers (n = 10) at local Memory Cafés as to the perceived capabilities of each individual for shopping and meal-making. Carers were asked to make pair-wise choices in order to select a personalised brochure and to complete a questionnaire to elicit the practicality, desirability and affordability of specific products and to probe for preferences amongst key features. Opinions on ease-of-use, aesthetics, expected safety-in-use, independence of use and stigma related to the technology packages were also collected. Results showed that carers are able to make detailed choices and express preferences about assistive and digital technologies for the individuals in their care, and customise their enabler package. Most believed that having an enabler package would improve safety. Greater exposure of carers to newer digital products would be beneficial. The brochure method could be employed on consumer websites and by AT assessors
Non-Bayesian Updating in a Social Learning Experiment
In our laboratory experiment, subjects, in sequence, have to predict
the value of a good. The second subject in the sequence makes his prediction twice: first (“first belief”), after he observes his predecessor’s prediction; second (“posterior belief”), after he observes his private signal.
We find that the second subjects weigh their signal as a Bayesian agent
would do when the signal confirms their first belief; they overweight the
signal when it contradicts their first belief. This way of updating, incompatible with Bayesianism, can be explained by the Likelihood Ratio Test
Updating (LRTU) model, a generalization of the Maximum Likelihood
Updating rule. It is at odds with another family of updating, the Full
Bayesian Updating. In another experiment, we directly test the LRTU
model and find support for it
Viable Recycling of Polystyrene via Hydrothermal Liquefaction and Pyrolysis
Chemical recycling is considered one of the most sustainable solutions to limit the environmental issues related to plastic waste pollution, whereby plastic is converted into more valuable compounds when mechanical recycling is not feasible. Among the most critical fast-growing components of municipal solid waste, polystyrene represents 1/3 of the filling materials in landfills. In this work, the chemical recycling of polystyrene via two main thermochemical processes is investigated: pyrolysis and hydrothermal liquefaction (HTL). The influence of temperature (HTL: 300-360 & DEG;C and pyrolysis: 400-600 & DEG;C) and reaction time (HTL: 1-4 h; pyrolysis: 30 min) on the products obtained was studied. The obtained liquid and solid products were analyzed by using gas chromatography-mass spectrometry (GC-MS), an elemental analysis (EA), Fourier-transform infrared spectroscopy (FT-IR) and a thermogravimetric analysis (TGA). During HTL, a temperature of 360 & DEG;C and reaction time of 4 h were needed to completely decompose the polystyrene into mainly oil (83%) and water-soluble compounds (10%). The former was mainly composed of aromatics while the water phase was mainly composed of aromatics and oxygenated compounds (benzaldehyde and acetophenone). The pyrolysis led to the formation of 45% gas and 55% oil at 500 & DEG;C, and the oil was 40% styrene. Pyrolysis was thus more selective towards the recovery of the styrene monomer while the HTL can be an effective process to produce renewable aromatics
A dissipative environment may improve the quantum annealing performances of the ferromagnetic p-spin model
We investigate the quantum annealing of the ferromagnetic -spin model in
a dissipative environment ( and ). This model, in the large limit, codifies the Grover's algorithm for searching in an unsorted
database. The dissipative environment is described by a phonon bath in thermal
equilibrium at finite temperature. The dynamics is studied in the framework of
a Lindblad master equation for the reduced density matrix describing only the
spins. Exploiting the symmetries of our model Hamiltonian, we can describe many
spins and extrapolate expected trends for large , and . While at weak
system bath coupling the dissipative environment has detrimental effects on the
annealing results, we show that in the intermediate coupling regime, the phonon
bath seems to speed up the annealing at low temperatures. This improvement in
the performance is likely not due to thermal fluctuation but rather arises from
a correlated spin-bath state and persists even at zero temperature. This result
may pave the way to a new scenario in which, by appropriately engineering the
system-bath coupling, one may optimize quantum annealing performances below
either the purely quantum or classical limit.Comment: 9 Pag, 5 Fig, Submitte
Localization-delocalization transition of a polaron near an impurity
We solve the problem of polaron localization on an attractive impurity by
means of direct-space Diagrammatic Monte Carlo implemented for the system in
the thermodynamic limit. In particular we determine the ground state phase
diagram in dependence on the electron-phonon coupling and impurity potential
strength for the whole phonon frequency range. Including the quantum phonon
dynamics we find and characterize a new phase which is missing in the zero
phonon-frequency limit (adiabatic approximation), where self-trapped polarons
are not localized at shallow impurities. We predict and show that in the
vicinity of the localization transition a region with a mixture of weak- and
strong-coupling spectral response is realized.Comment: 4 pages, 4 figur
Updating ambiguous beliefs in a social learning experiment
We present a social learning experiment in which subjects predict the value of a good in sequence. We elicit each subject’s belief twice: first (“first belief”), after he observes his predecessors’ prediction; second, after he also observes a private signal. Our main result is that subjects update on their signal asymmetrically. They weigh the private signal as a Bayesian agent when it confirms their first belief and overweight it when it contradicts their first belief. This way of updating, incompatible with Bayesianism, can be explained by ambiguous beliefs (multiple priors on the predecessor’s rationality) and a generalization of the Maximum Likelihood Updating rule. Our experiment allows for a better understanding of the overweighting of private information documented in previous studies
Biomass Gasification and Tar Reforming in a Two-stage Reactor
Abstract Gasification is recognized as one of the most promising technologies to convert low quality fuels into more valuable ones. The principal problem related with the use of biomass in gasification processes is the high amount of tar released during the pyrolysis step. It is thus necessary to recover the tar and to transform it in lighter combustible gas species such as CH4, CO and H2 by means of catalytic processes. In this work the gasification of olive husk is performed in order to produce a high quality syngas, composed principally by carbon monoxide and hydrogen, using an innovative laboratory scale two-stage reactor. The first stage is used for gasification and the second for catalytic reforming. It is thus possible to recover the tar energy converting it into CO and H2. Ce-promoted bimetallic Ni-Co catalyst was tested and compared with Ni catalyst, both supported on γ-Al2O3
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