2,830 research outputs found
Co-digestion of macroalgae for biogas production: an LCA-based environmental evaluation
Algae represent a favourable and potentially sustainable source of biomass for bioenergy-based industrial pathways in the future.
The study, performed on a real pilot plant implemented in Augusta (Italy) within the frame of the BioWALK4Biofuels project,
aims to figure out whether seaweed (macroalgae) cultivated in near-shore open ponds could be considered a beneficial aspect as a
source of biomass for biogas production within the co-digestion with local agricultural biological waste. The LCA results
confirm that the analysed A and B scenarios (namely the algae-based co-digestion scenario and agricultural mix feedstock
scenario) present an environmental performance more favourable than that achieved with conventional non-renewable-based
technologies (specifically natural gas - Scenario C). Results show that the use of seaweed (Scenario A) represent a feasible
solution in order to replace classical biomass used for biofuel production from a land-based feedstock. The improvement of the
environmental performances is quantifiable on 10% respect to Scenario B, and 38 times higher than Scenario
Surrogate-based Real-time Curbside Management for Ride-hailing and Delivery Operations
The present work investigates surrogate model-based optimization for
real-time curbside traffic management operations. An optimization problem is
formulated to minimize the congestion on roadway segments caused by vehicles
stopping on the segment (e.g., ride-hailing or delivery operations) and
implemented in a model predictive control framework. A hybrid simulation
approach where main traffic flows interact with individually modeled stopping
vehicles is adopted. Due to its non-linearity, the optimization problem is
coupled with a meta-heuristic. However, because simulations are time expensive
and hence unsuitable for real-time control, a trained surrogate model that
takes the decision variables as inputs and approximates the objective function
is employed to replace the simulation within the meta-heuristic algorithm.
Several modeling techniques (i.e., linear regression, polynomial regression,
neural network, radial basis network, regression tree ensemble, and Gaussian
process regression) are compared based on their accuracy in reproducing
solutions to the problem and computational tractability for real-time control
under different configurations of simulation parameters. It is found that
Gaussian process regression is the most suited for use as a surrogate model for
the given problem. Finally, a realistic application with multiple ride-hailing
vehicle operations is presented. The proposed approach for controlling the stop
positions of vehicles is able to achieve an improvement of 20.65% over the
uncontrolled case. The example shows the potential of the proposed approach in
reducing the negative impacts of stopping vehicles and favorable computational
properties
Surface-acoustic-wave driven planar light-emitting device
Electroluminescence emission controlled by means of surface acoustic waves
(SAWs) in planar light-emitting diodes (pLEDs) is demonstrated. Interdigital
transducers for SAW generation were integrated onto pLEDs fabricated following
the scheme which we have recently developed. Current-voltage, light-voltage and
photoluminescence characteristics are presented at cryogenic temperatures. We
argue that this scheme represents a valuable building block for advanced
optoelectronic architectures
Model-based traffic state estimation for link traffic using moving cameras
Traffic State Estimation (TSE) is the process of inferring traffic conditions
based on partially observed data using prior knowledge of traffic patterns. The
type of input data used has a significant impact on the accuracy and
methodology of TSE. Traditional TSE methods have relied on data from either
stationary sensors like loop detectors or mobile sensors such as GPS-equipped
floating cars. However, both approaches have their limitations. This paper
proposes a method for estimating traffic states on a road link using vehicle
trajectories obtained from cameras mounted on moving vehicles. It involves
combining data from multiple moving cameras to construct time-space diagrams
and using them to estimate parameters for the link's fundamental diagram (FD)
and densities in unobserved regions of space-time. The Cell Transmission Model
(CTM) is utilized in conjunction with a Genetic Algorithm (GA) to optimize the
FD parameters and boundary conditions necessary for accurate estimation. To
evaluate the effectiveness of the proposed methodology, simulated traffic data
generated by the SUMO traffic simulator was employed incorporating 140
different space-time diagrams with varying lane density and speed. The
evaluation of the simulated data demonstrates the effectiveness of the proposed
approach, as it achieves a low root mean square error (RMSE) value of 0.0079
veh/m and is comparable to other CTM-based methods. In conclusion, the proposed
TSE method opens new avenues for the estimation of traffic state using an
innovative data collection method that uses vehicle trajectories collected from
on-board cameras.Comment: Under review for journal submissio
Atmospheric circulation patterns, cloud-to-ground lightning, and locally intense convective rainfall associated with debris flow initiation in the Dolomite Alps of northeastern Italy
The Dolomite Alps of northeastern Italy experience debris flows with great
frequency during the summer months. An ample supply of unconsolidated
material on steep slopes and a summer season climate regime characterized by
recurrent thunderstorms combine to produce an abundance of these destructive
hydro-geologic events. In the past, debris flow events have been studied
primarily in the context of their geologic and geomorphic characteristics.
The atmospheric contribution to these mass-wasting events has been limited
to recording rainfall and developing intensity thresholds for debris
mobilization. This study aims to expand the examination of atmospheric
processes that preceded both locally intense convective rainfall (LICR) and
debris flows in the Dolomite region. 500 hPa pressure level plots of
geopotential heights were constructed for a period of 3Â days prior to
debris flow events to gain insight into the synoptic-scale processes which
provide an environment conducive to LICR in the Dolomites. Cloud-to-ground (CG)
lightning flash data recorded at the meso-scale were incorporated to
assess the convective environment proximal to debris flow source regions.
Twelve events were analyzed and from this analysis three common synoptic-scale circulation patterns were identified. Evaluation of CG flashes at
smaller spatial and temporal scales illustrated that convective processes
vary in their production of CF flashes (total number) and the spatial
distribution of flashes can also be quite different between events over
longer periods. During the 60 min interval immediately preceding debris
flow a majority of cases exhibited spatial and temporal colocation of LICR
and CG flashes. Also a number of CG flash parameters were found to be
significantly correlated to rainfall intensity prior to debris flow initiation
A comprehensive next generation sequencing test for the diagnosis of inherited bleeding, thrombotic and platelet disorders
Acoustic charge transport in n-i-n three terminal device
We present an unconventional approach to realize acoustic charge transport
devices that takes advantage from an original input region geometry in place of
standard Ohmic input contacts. Our scheme is based on a n-i-n lateral junction
as electron injector, an etched intrinsic channel, a standard Ohmic output
contact and a pair of in-plane gates. We show that surface acoustic waves are
able to pick up electrons from a current flowing through the n-i-n junction and
steer them toward the output contact. Acoustic charge transport was studied as
a function of the injector current and bias, the SAW power and at various
temperatures. The possibility to modulate the acoustoelectric current by means
of lateral in-plane gates is also discussed. The main advantage of our approach
relies on the possibility to drive the n-i-n injector by means of both voltage
or current sources, thus allowing to sample and process voltage and current
signals as well.Comment: 9 pages, 3 figures. Submitted to Applied Physics Letter
FURTHER DEVELOPMENT OF AN ALGEBRAIC INTERMITTENCY MODEL FOR SEPARATION-INDUCED TRANSITION UNDER ELEVATED FREE-STREAM TURBULENCE
A constitutive law for the Reynolds stresses during boundary layer laminar-to-turbulent transition, constructed in previous work by elastic-net regression on an experimental data base, has been incorporated in an algebraic intermittency model. The objective is prediction improvement of transition in a separated layer under an elevated free-stream turbulence level. The modelling for such cases functions through additional production terms in the transport equations of turbulent kinetic energy and specific dissipation rate of a k-ω turbulence model. A sensor detects the front part of a separated layer and activates the production terms. These express the effect of Klebanoff streaks generated upstream of separation on the Kelvin-Helmholtz instability rolls in the separated part of the layer. By the Klebanoff streaks, the breakdown is faster and the speed of breakdown increases by the combined effects of a large adverse pressure gradient and an elevated free-stream turbulence level
Restoring an eroded legitimacy: the adaptation of nonfinancial disclosure after a scandal and the risk of hypocrisy
Purpose \u2013 This study contributes to the literature on hypocrisy in corporate social responsibility by
investigating how organizations adapt their nonfinancial disclosure after a social, environmental or
governance scandal.
Design/methodology/approach \u2013 The present research employs content analysis of nonfinancial
disclosures by 11 organizations during a 3-year timespan to investigate how they responded to major
scandals in terms of social, environmental and sustainability reporting and a content analysis of independent
counter accounts to detect the presence of views that contrast with the corporate disclosure and suggest
hypocritical behaviors.
Findings \u2013 Four patterns in the adaptation of reporting \u2013 genuine, allusive, evasive, indifferent \u2013 emerge from
information collected on scandals and socially responsible actions. The type of scandal and cultural factors can
influence the response to a scandal, as environmental and social scandal can attract more scrutiny than
financial scandals. Companies exposed to environmental and social scandals are more likely to disclose
information about the scandal and receive more coverage by external parties in the form of counter accounts.
Originality/value \u2013 Using a theoretical framework based on legitimacy theory and organizational hypocrisy,
the present research contributes to the investigation of the adaptation of reporting when a scandal occurs and
during its aftermath
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