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Modeling atmospheric turbulence in the convective boundary layer is challenging at kilometer and subkilometer resolutions, as the horizontal grid spacing approaches the size of the most energetic turbulent eddies. In this range of resolutions, termed terra incognita or gray zone, partially resolved convective structures are grid dependent and neither traditional 1D mesoscale parameterizations nor 3D large-eddy simulations closures are theoretically appropriate. Leveraging on a new set of one-way nested, full-physics multiscale numerical experiments, we quantify the magnitude of the errors introduced at gray zone resolutions in a real-case application and we provide new perspectives on recently proposed modeling approaches. The new set of experiments is forced by real-time-varying boundary conditions, spans a wide range of scales, and includes traditional 1D schemes, 3D closures, scale-aware parameterizations, and strategies to suppress resolved convection at gray zone resolutions. The study area is Riyadh (Saudi Arabia), where deep CBLs develop owing to strong convective conditions. Detailed analyses of our experiments, including validation with radiosonde data, calculations of spectral features, and partitioning of turbulent fluxes between resolved and subgrid scales, show that (i) grid-dependent convective structures entail minor impacts on the first-order characteristics of the fully developed boundary layer due to some degree of implicit scale awareness of 1D parameterizations and (ii) 3D closures and scale-aware schemes outperform traditional 1D schemes especially in the surface layer, among other findings. The new suite of experiments provides a benchmark of real simulations that can be extended to assess how new turbulence closures perform at gray zone resolutions. Significance Statement As recent advances in high-performance computing are leading to a new era in numerical simulations, regional atmospheric models can now increase their resolution to the widely unexplored kilometer and subkilometer range. While increasing the resolution of atmospheric models is desirable to (i) have more realistic weather and air quality predictions and (ii) better represent boundary conditions for microscale models, kilometer and subkilometer grid spacings pose some theoretical challenges that need to be addressed by the atmospheric modeling community. In this work we run a set of numerical experiments for a real case study that aim to offer new perspectives on recently developed modeling strategies and identify the most promising directions that should be investigated by follow-up studies.

The impact of the emissions from a municipal Waste-to-Energy (WtE) plant in Northern Italy on local air quality was assessed using the CALMET-CALPUFF atmospheric dispersion modelling system. Model simulations were based on hourly emission rates measured by continuous stack monitoring systems and considered both air quality-regulated pollutants (nitrogen oxides, particulate matter, toxic elements, benzo(a)pyrene), and other trace pollutants typical of WtE plants (dioxins, furans, and mercury). The model results were compared to both long-term observations from the air quality monitoring network and with short-term measurements from dedicated monitoring campaigns in the vicinity of the WtE plant, in both warm and cold season conditions. Modelling and observational results showed that the estimated plant contributions are very limited. This suggests that the observed concentration levels were the result of the contribution of all the sources distributed over the area and that they were not solely driven by the activity of the plant. Estimated contributions from the plant’s emissions were usually at least two orders of magnitudes lower than the ambient levels at the nearest monitoring site and even lower at the farthest sites.

Summary Background Exposure to poor air quality leads to increased premature mortality from cardiovascular and respiratory diseases. Among the far-reaching implications of the ongoing COVID-19 pandemic, a substantial improvement in air quality was observed worldwide after the lockdowns imposed by many countries. We aimed to assess the implications of different lockdown measures on air pollution levels in Europe and China, as well as the short-term and long-term health impact. Methods For this modelling study, observations of fine particulate matter (PM2·5) concentrations from more than 2500 stations in Europe and China during 2016–20 were integrated with chemical transport model simulations to reconstruct PM2·5 fields at high spatiotemporal resolution. The health benefits, expressed as short-term and long-term avoided mortality from PM2·5 exposure associated with the interventions imposed to control the COVID-19 pandemic, were quantified on the basis of the latest epidemiological studies. To explore the long-term variability in air quality and associated premature mortality, we built different scenarios of economic recovery (immediate or gradual resumption of activities, a second outbreak in autumn, and permanent lockdown for the whole of 2020). Findings The lockdown interventions led to a reduction in population-weighted PM2·5 of 14·5 μg m−3 across China (−29·7%) and 2·2 μg m−3 across Europe (−17·1%), with unprecedented reductions of 40 μg m−3 in bimonthly mean PM2·5 in the areas most affected by COVID-19 in China. In the short term, an estimated 24 200 (95% CI 22 380–26 010) premature deaths were averted throughout China between Feb 1 and March 31, and an estimated 2190 (1960–2420) deaths were averted in Europe between Feb 21 and May 17. We also estimated a positive number of long-term avoided premature fatalities due to reduced PM2·5 concentrations, ranging from 76 400 (95% CI 62 600–86 900) to 287 000 (233 700–328 300) for China, and from 13 600 (11 900–15 300) to 29 500 (25 800–33 300) for Europe, depending on the future scenarios of economic recovery adopted. Interpretation These results indicate that lockdown interventions led to substantial reductions in PM2·5 concentrations in China and Europe. We estimated that tens of thousands of premature deaths from air pollution were avoided, although with significant differences observed in Europe and China. Our findings suggest that considerable improvements in air quality are achievable in both China and Europe when stringent emission control policies are adopted. Funding None.

This paper presents and discusses the outcome of a multi-disciplinary study aimed at evaluating ground surface movements which could be potentially induced by the future gas production of a carbonate reservoir located in central Italy. Thanks to both good quality and quantity of data (i.e. seismic surveys, well logs, petrophysical data, PVT-PressureVolumeTemperature-fluid data, geotechnical lab data) the issue was addressed via the set-up of a coupled 3D fluid flow and mechanical model based on the preliminary definition of a 3D structural and geological model. Because it is a forecast study, no model calibration was possible, consequently a set of sensitivity analyses were performed so as to assess the effect of the most critical parameters on subsidence evolution. The 3D FEM (Finite Element Method) mechanical model was set up by adopting an elasto-plastic constitutive law. The model was populated via the integration of data from different sources at different scales (i.e. lab tests, in situ acquisition, literature) and data interpretation adopting a traditional rock mechanics approach, in other words Bieniawski classification and the Barton classification. The obtained strength and deformation parameters depend on the Hoek and Brown criterion and the GSI classification application.

The representation of air quality and meteorology over Asia remains challenging for chemical transport models as a result of the complex interactions between the East Asian monsoons and the large uncertainty (in space and time) of the high anthropogenic emissions levels over the region. High spatial resolution models allow resolving small-scale features induced by the complex topography of this region. In this study, the Weather Research and Forecasting model with Chemistry (WRF-Chem) was used to simulate the spatial and seasonal variability of main physical and chemical variables over Asia for the year 2015 at 8-km horizontal resolution to enable resolving small-scale features induced by the region complex topography. The simulated atmospheric composition was evaluated against satellite retrievals (MOPITT, IASI + GOME2, MODIS and OMI) in addition to ground-based observations in China for the year 2015, while the meteorological variables were evaluated by several observational-based datasets (ERA5, CRU, MODIS, MTE). Results showed low to moderate seasonal biases for major meteorological variables, i.e. air temperature, relative humidity, precipitation, latent heat, sensible heat and snow cover fraction. Overall, WRF-Chem reproduced well the spatial and seasonal variability of lowermost tropospheric ozone content, total column carbon monoxide and aerosol optical depth, while large discrepancies were found for tropospheric nitrogen dioxide content, mainly during the warm season. In consistency with previous studies, the different biases between model-simulated and satellite-retrieved values can be mainly attributed to i) the large uncertainties in anthropogenic and natural nitrogen oxides emission estimates, as well as dust and sea salt emissions in the case of aerosol optical depth, and ii) some coarse parameterizations used to reproduce main small-scale features (e.g. meteorology, chemical processes, dry deposition to vegetation). Compared to ground-based observations, the WRF-Chem model reproduced well the mean annual cycle of surface nitrogen dioxide, ozone and fine particles concentrations in all seasons across China. Our results suggest that WRF-Chem provides reliable spatio-temporal patterns for most of the meteorological and chemical variables, adding thus confidence to its applicability in the context of air pollution risk assessment to human and ecosystems health.

Policymakers worldwide have set challenging sustainable energy targets to decarbonize their economy. Despite the ambitious pledges, several emerging countries still lack an actual progress towards the envisioned goals, often due to the scarcity of accurate data. Here, we propose a practical methodology for bridging the gap between the wind energy targets and their implementation. We illustrate our new methodology by focusing on Saudi Arabia, which endeavors to play a leading role in the renewable energy sector and pledges to install 16GW of wind capacity by 2030. We propose a blueprint for the optimal wind farms buildout, combining novel high-resolution model simulations, a unique set of observations, land-use restrictions and a thorough cost assessment. The most suitable technological option is selected among multiple turbine models for each potential site. Our findings suggest that Saudi Arabia is well positioned to become a role model for wind energy development within the Middle East, with 26% of the electricity demand that could be met by wind power. The average levelized cost of energy of the proposed buildout is 39 USD MWh−1, which confirms the competitiveness of wind resources in Saudi Arabia. We identify the area close to Gulf of Aqaba as the most cost-effective region for wind harvesting, with turbines characterized by moderate specific rating (350 W m−2) at relatively low hub height (75 m). The modelling framework proposed in this work can be adopted by other countries aiming to start or strengthen their wind energy portfolio.

This study presents a high–resolution (5 km) set of new simulations performed with CAMx v6.40 over the Po Valley area (Northern Italy), aimed to enhance organic aerosol (OA) levels prediction and to gain insight into the sensitivity of CAMx to different uncertain features of the input setup. In particular, we mainly investigated the role of (i) volatility distributions of organic emissions, (ii) parametrizations of semi– and intermediate–volatile organic compounds (S/IVOC) emissions and (iii) different aging schemes, by exploiting the latest experimental information available in the recent scientific literature. Model results were validated against two OA–specific datasets, available for both an urban site (Bologna, February 2013) and a rural one (Ispra, March 2013). We found out a remarkable performance enhancement of modelled OA levels when applying revisions in S/IVOC emission parametrizations together with the new volatility distributions, at both the validation sites. This performance enhancement is associated with a very significant improvement in secondary organic aerosol (SOA) prediction, mainly due to revised IVOC emissions. At Bologna urban site, mean fractional bias (MFB) of OA ranged from −80.1% in the worst run to −10.1% in the best one and index of agreement (IOA) from 0.52 to 0.75. Notable improvements but overall poorer metrics were found for Ispra site, where MFB ranges from −84.2% to −35% and IOA from 0.45 to 0.50. These findings indicate that organic matter in the semi– and intermediate–volatile range are most likely underestimated in official emission inventories for each main source category (i.e. biomass burning, diesel and gasoline vehicles exhaust). Finally, model results did not show a very pronounced sensitivity to aging processes, due to the low photochemical activity typically observed during winter–time. However, we give evidence that enabling aging processes for biomass burning related SOA, which is by default disabled in CAMx v6.40, can help in closing the gap between modelled and observed SOA concentrations.

This work analyzes the frequency of days characterized by daytime temperature inversion and air stagnation events in the Po valley area. The analysis is focused on both historical series and future projections under climate change. Historical sounding data from two different Italian stations are used as well as future projections data, provided by CMCC-CCLM 4-8-19 regional climate model (MED-CORDEX initiative). A new method to detect layers of temperature inversion is also presented. The developed method computes the occurrence of a temperature inversion layer for a given day at 12 UTC without a detailed knowledge of temperature vertical profile. This method was validated using sounding data and applied to the model projections, under two different emissions scenarios (RCP4.5 and RCP8.5). Under RCP4.5 intermediate emissions scenario, the occurrence of temperature inversions is projected to increase by 12 days/year (around + 10%) in the last decade of 21st century compared to 1986–2005 average. However, the increase in temperature inversions seems to be especially concentrated in the warm period. Under RCP8.5 extreme scenario, temperature inversions are still projected to increase, though to a lesser extent compared to RCP4.5 scenario (+ 6 days/year in the last decade of 21st century). A similar trend was found also for air stagnation events, which take into account the variation of precipitation pattern and wind strength. The expected increases are equal to + 13 days/year and + 11 days/year in the last decade of 21st century compared to 1986–2005 average, under RCP4.5 and RCP8.5 scenarios respectively.

Information technology (IT) systems must provide their users with prescribed quality of service (Qos) levels, usually defined in terms of application performance. Qos requirements are in general difficult to satisfy, since the system workload may vary by orders of magnitude within the same business day. To meet Qos requirements, resources have to dynamically be allocated among running applications, re-configuring them at run-time. To deal with resource allocation so as to manage system overload issues admission control and server virtualization are typically used: the former is a protection mechanism that rejects requests under peak workload, whereas the latter allows partitioning physical resources such as CPU and disks into multiple virtual ones. For designing effective controllers to ensure the desired Qos levels, a reliable model of the server dynamics is needed. The given systems, while retaining the time-varying nature that allows one to model workload variations. To address this issue, a constrained black-box subspace identification approach endowed with a novel structure selection is designed, and the performance of the identified models are assessed on experimental data.

Background —This study was performed to compare implantation of a DDI pacemaker with rate hysteresis with no implant in respect to syncopal recurrences in patients with severe cardioinhibitory tilt-positive neurally mediated syncope. Methods and Results —Forty-two patients from 18 European centers were randomized to receive a DDI pacemaker programmed to 80 bpm with hysteresis of 45 bpm (19 patients) or no pacemaker (23 patients). Inclusion criteria were ≥3 syncopes over the last 2 years and a positive cardioinhibitory (Vasovagal Syncope International Study types 2A and 2B) response to tilt testing. The median number of previous syncopal episodes was 6; asystolic response to tilt testing was present in 36 patients (86%) (mean asystole, 13.9±10.2 seconds). All patients were followed up for a minimum of 1.0 years and a maximum of 6.7 years (mean, 3.7±2.2). One patient (5%) in the pacemaker arm experienced recurrence of syncope compared with 14 patients (61%) in the no-pacemaker arm ( P =0.0006). In the no-pacemaker arm, the median time to first syncopal recurrence was 5 months, with a rate of 0.44 per year. On repeated tilt testing performed within 15 days after enrollment, positive responses were observed in 59% of patients with pacemakers and in 61% of patients without pacemakers ( P =NS). Conclusions —In a limited, select group of patients with tilt-positive cardioinhibitory syncope, DDI pacing with hysteresis reduced the likelihood of syncope. The benefit of the therapy was maintained over the long term. Even in untreated patients, the syncopal recurrence burden was low. A negative result of tilt testing was not a useful means to evaluate therapy efficacy.

Background —Etilefrine is an α-agonist agent with a potent vasoconstrictor effect, which is potentially useful in preventing vasovagal syncope by reducing venous pooling and/or by counteracting reflex arteriolar vasodilatation. The present multicenter, randomized, placebo-controlled study was designed to evaluate the efficacy of this drug for the long-term management of patients with recurrent vasovagal syncope. Methods and Results —In the 20 participating centers, 126 patients with recurrent vasovagal syncope (at least 3 episodes in the last 2 years) and a positive baseline head-up tilt response were randomly assigned to placebo (63 patients) or etilefrine at a dosage of 75 mg/d (63 patients) and were followed up for 1 year or until syncope recurred. The primary end-point of the study was the first recurrence of syncope. There were no differences between the 2 study groups in the patients’ baseline characteristics. During follow-up, the group treated with etilefrine had a similar incidence of first syncopal recurrence to that of placebo group both in the intention-to-treat analysis (24% versus 24%) and in on- treatment analysis (26% versus 24%). Moreover, the median time to the first syncopal recurrence did not significantly differ between the 2 study groups (106 days in the etilefrine arm and 112 days in the placebo arm). Conclusions —Oral etilefrine is not superior to placebo in preventing spontaneous episodes of vasovagal syncope. Randomized controlled studies are essential to assess the real usefulness of any proposed therapy for patients with vasovagal syncope.

By-wire technologies are extremely appealing, as they allow a fully adjustable modulation of the actuation system, together with better potential performance than their wired counterparts. In this work, a novel electro-mechanical layout for a full by-wire management of a motorcycle clutch system is presented, and the related control problem is addressed. Comparing the new system with a more traditional electro-hydraulic setup that was previously studied, it results easier to control and it provides a better riding feeling. Experimental results on an instrumented vehicle demonstrate the effectiveness of the proposed approach.

Launch control is an innovative active system which offers an appealing automatic feature for sport motorcycles. Due to the high power of the engine and to the complexity of the torque transfer dynamics driving a smooth and safe start from a standstill might be difficult for non-expert riders in some working conditions. As such, an active controller capable of safely managing the vehicle acceleration from a standing start might effectively support the rider as far as both safety and performance are concerned. To control such a maneuver, two possible actuators can be employed: the engine throttle and the clutch. This paper illustrates the analysis and the design of a clutch-based launch controller for sport motorcycles, demonstrating that it allows the accurate tracking of an acceleration set-point thanks to a dedicated clutch position controller. Experimental results are presented that demonstrate the effectiveness of the proposed approach.

Vehicle velocity and tire-road friction conditions are crucial variables to determine the vehicle behaviour in all maneuvers; therefore, all active control systems must either be robust with respect to them, or adapt their parameters to their current value if they can we propose to employ be either measured or estimated. A direct measurement of the vehicle velocity in slipping conditions is in general complex and impractical, and the same holds true for tire-road friction conditions. In this paper, sliding mode observers are proposed to estimate vehicle acceleration, which can be used both as in input for existing algorithms for vehicle velocity estimation and for estimating the current road conditions. Experimental results support the validity of the proposed approach.

This paper addresses the identification and control of a motorcycle electro-hydraulic clutch, to be employed as main actuator for the design of future automatic gear shift controllers and launch controllers. These applications have very different requirements in terms of tracking performance, and designing an effective controller for both working conditions is a challenging task, mainly due to the significant parametric uncertainties affecting the system, and the limited precision and resolution of the on-board sensors. The paper discusses the identification of a control-oriented model of the clutch dynamics and the controller design, presenting experimental results which witness the effectiveness of the proposed approach.

IT systems have to provide to their users prescribed Quality of Service (QoS) levels, usually defined in terms of application performance, which must hold irrespectively of the significantly time-varying workload. To handle system overload issues, admission control is used as an overload protection mechanism which rejects requests under peak workload conditions in order to provide QoS guarantees to the running applications. For ensuring QoS levels at design time, the performance of such mechanisms should be a priori guaranteed. To this end, this paper proposes an appropriate controller, the closed-loop stability properties pf which are formally assessed.

This paper addresses the analysis of the gear shifting maneuver for motorcycles and it constitutes, to our best knowledge, the first contribute to study this aspect in two-wheeled vehicles. Specifically, a comparison between automatic and manual gear shifting is discussed, based on which some cost functions are proposed to quantitatively evaluate the maneuver quality from measured data. Based on such cost functions, we are able to automatically classify the performed maneuver and label it with a quality attribute matching that assigned by the rider.

The relationship between ventricular arrhythmias (VA) in the subacute phase of a myocardial infarction and subsequent major arrhythmic events (MAE) was mainly defined in the prefibrinolytic era, We examined the large population of patients enrolled in the GISSI-2 study in order to evaluate the significance and predictive power for MAE (sustained ventricular tachycardia -SVT-and sudden death -SD-) of VA detected by Holter monitoring during the subacute phase of a fibrinolysed acute myocardial infarction (AMI). Of the 12,381 pts. enrolled in the GISSI-2 study, an Holter monitoring was available in 8,676 and a six month follow-up was completed in 7,713. During the follow-up 84 pts. died suddenly and 26 experienced one or more SVT. The relationship between VA and MAE was evaluated by odds ratio (OR) and their 95% confidence intervals. OR for MAE was 4.5 (2.7–7.5) if the Holter showed > 10 ventricular ectopic beats per hour; 2.3 (1.5–3.7) if couplets were present; 3.3 (1.5–7.0) if nonsustained ventricular tachycardias (NSVT) were noticed; 3.0 12.0–4.5) if any complex VA was detected. A multivariate analysis (Cox modell including the major prognostic determinants confirmed the independent prognostic value of VA in the Holter recording except for NSVT. Any arrhythmic parameter had a very low positive predictive power (from 2.4 to 3.0%). In conclusion, our data show that VA still have, in the fibrinolytic era, a prognostic significance for MAE, but the predictive power is very low and is therefore mandatory to add other variables to identify the pts. more at risk.

The catalytic activity of different polymers containing axime groups has been tested in the hydrolysis of structurally different esters of p-nitrophenol. The mechanism of hydrolysis, supported by indirect kinetic evidence, seems not to involve a pre-equilibrium with a polymer-ester complex. The reaction was investigated under pseudo-first-order conditions with an excess of oxime polymer. The values of the second-order catalytic rate coefficients suggest a reaction rate mainly controlled by steric effects and hydrophobic interaction between the ester hydrocarbon residue and the macromolecular chain.