659 research outputs found

    On integrable conservation laws

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    We study normal forms of scalar integrable dispersive (non necessarily Hamiltonian) conservation laws via the Dubrovin-Zhang perturbative scheme. Our computations support the conjecture that such normal forms are parametrised by infinitely many arbitrary functions that can be identified with the coefficients of the quasilinear part of the equation. More in general, we conjecture that two scalar integrable evolutionary PDEs having the same quasilinear part are Miura equivalent. This conjecture is also consistent with the tensorial behaviour of these coefficients under general Miura transformations.Comment: 17 page

    Integrable viscous conservation laws

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    We propose an extension of the Dubrovin-Zhang perturbative approach to the study of normal forms for non-Hamiltonian integrable scalar conservation laws. The explicit computation of the first few corrections leads to the conjecture that such normal forms are parameterized by one single functional parameter, named viscous central invariant. A constant valued viscous central invariant corresponds to the well-known Burgers hierarchy. The case of a linear viscous central invariant provides a viscous analog of the Camassa-Holm equation, that formerly appeared as a reduction of a two-component Hamiltonian integrable systems. We write explicitly the negative and positive hierarchy associated with this equation and prove the integrability showing that they can be mapped respectively into the heat hierarchy and its negative counterpart, named the Klein-Gordon hierarchy. A local well-posedness theorem for periodic initial data is also proven. We show how transport equations can be used to effectively construct asymptotic solutions via an extension of the quasi-Miura map that preserves the initial datum. The method is alternative to the method of the string equation for Hamiltonian conservation laws and naturally extends to the viscous case. Using these tools we derive the viscous analog of the Painlevé I2 equation that describes the universal behaviour of the solution at the critical point of gradient catastrophe

    Frailty and elderly in urology: Is there an impact on post-operative complications?

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    INTRODUCTION: Frailty used as predictive tool is still not carried out in daily practice, although many studies confirm the great clinical importance of the frailty syndrome in surgical outcomes. There is no standardized method of measuring the physiological reserves of older surgical patients. The aim of this study was to analyze a cohort of older urological patients according to various frailty indices, in order to evaluate whether they are predictors of post-operative complications after urological procedures. MATERIAL AND METHODS: This is a prospective observational study on 78 consecutive older ( 6570 years) patients, subjected to major urological (both endoscopic and 'open surgical') procedures. Frailty was defined according to the Edmonton Frail Scale. Several risk models and biochemical parameters were evaluated. Post-operative outcomes were surgical and medical complications, mortality and rehospitalisation within 3 months. RESULTS: An overall prevalence of frailty of 21.8% was found. Patients with complications were frailer than those without complications (univariate analysis), considering both total patients (p = 0.002) and endoscopic (p = 0.04) and 'open surgical' patients (p = 0.013). However, in multivariate analysis, a significant correlation was not found between all frailty indices tested and the risk of major complications. Limitation of the study: the small sample size (lack of statistical power), although this is a prospective study focused on older urological patients. CONCLUSIONS: New urology-tailored pre-operative assessment tools may prove beneficial when calculating the risks/benefits of urological procedures, so that objective data can guide surgical decision- making and patient counselling. Further large clinical studies specifically focusing on elderly in urology will be needed

    Enhancement of Heavy-Duty Engines Performance and Reliability Using Cylinder Pressure Information

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    Sustainability issues are becoming increasingly prominent in applications requiring the use of heavy-duty engines. Therefore, it is important to cut emissions and costs of such engines to re-duce the carbon footprint and keep the operating expenses under control. Even if for some applications a battery electric equipment is introduced, the diesel-equipped machinery is still popular, thanks to the longer operating range. In this field, the open pit mines are a good example. In fact, the Total Cost of Ownership (TCO) of the mining equipment is highly impacted by fuel consumption (engine efficiency) and reliability (service interval and en-gine life). The present work is focused on efficiency enhancements achievable through the ap-plication of a combustion control strategy based on the in-cylinder pressure information. The benefits are mainly due to two factors. First, the negative effects of injectors ageing can be com-pensated. Second, cylindrical online calibration of the control parameters enables the combus-tion system optimization. The article is divided into two parts. The first part describes the tool-chain that is designed for the real time application of the combustion control system, while the second part concerns the algorithm that would be implemented on the Engine Control Unit (ECU) to leverage the in-cylinder pressure information. The assessment of the potential benefits and feasibility of the combustion control algorithm is carried out in a Software in the Loop (SiL) environment, simulating both the developed control strategy and the engine behavior (Liebherr D98). Our goal is to validate the control algorithm through SiL simulations. The results of the validation process demonstrate the effectiveness of the control strategy: firstly, cylinder dispari-ty on IMEP (+/-2.5% in reference conditions) is virtually canceled. Secondly, MFB50 is individual-ly optimized, equalizing Pmax among the cylinders (+/-4% for the standard calibration), without exceeding the reliability threshold. In addition to this, BSFC is reduced by 1%, thanks to the ac-curate cylinder-by-cylinder calibration. Finally, ageing effects or fuel variations can be implicitly compensated, keeping optimal performance thorough engine life

    Risk management in solitary agricultural work: new technologies for handling emergency and falls from great heights (SHADE)

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    Solitary work and agricultural activities are the scenarios of a large number of severe injuries and deaths, also because first aid may be difficult to achieve in isolated locations. This work proposes a technology available on smartphones that allows triggering an emergency call when a fall from height or an unconsciousness state is detected. The results of several tests, which include different detection algorithms and scenarios, are reported in this work. Tests performed with the aid of a dummy have allowed developing a reliable algorithm for the detection of dangerous situations. This system is available as an Android application

    Scenario analysis of livestock-related PM2.5 pollution based on heteroskedastic geostatistical modelling

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    The air in the Lombardy region, Italy, is one of the most polluted in Europe because of limited air circulation and high emissions levels. There is a large scientific consensus that the agricultural sector has a major impact on air quality. In Lombardy, livestock activities are widely acknowledged to be responsible for approximately 97% of regional ammonia emissions due to the high density of livestock. The main objective of our study is to quantify the relationship between ammonia emissions and PM2.5 concentrations in the Lombardy region and evaluate PM2.5 changes due to the reduction of ammonia emissions through scenario analysis. In particular, the study refers to the years between 2016 and 2020 inclusive. The information contained in the data is exploited using a spatiotemporal model capable of handling spatial and temporal correlation, as well as missing data. In this study, we propose a heteroskedastic extension of the Hidden Dynamic Geostatistical Model (HDGM) which is a two-level hierarchical model suitable for complex environmental processes. Scenario analysis will be carried out on high-resolution maps of the Lombardy region showing the changes in PM2.5 across the area. As a result, it is shown that a 26% reduction in NH3 emissions in the wintertime could reduce the PM2.5 average by 2.09 mg/m3 while a 50% reduction could reduce the PM2.5 average by 4.02 mg/m3 which corresponds to a reduction close to 5% and 10% respectively. Finally, results are detailed by province and land type

    Pandemics and international security: The outlook for NATO

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    The Covid-19 pandemic has had a multi-faced impact on Western societies, quickly moving from a health crisis to a broader phenomenon deeply affecting the socio-economic and political landscapes. Multilateral institutions had to cope with unprecedented challenges, while the pandemic exposed existing patterns of great power competition applied to the global race for personal protective equipment, vaccines, and relevant raw materials. Nations – at least initially – seemed to abandon well- established patterns of cooperation to revert to national solutions to this very global challenge. Global economy experienced disruptions in trade and in the functioning of the Global Value Chains (GVCs), as well as significant redistributions of wealth through drastic downs and ups of Gross Domestic Product (GDP) across the world. In less than two years, the pandemic experience prompted a deep revision of standard views on critical interdependencies, diversification, resilience of GVCs and security of supplies. When it comes to international security, the pandemic mostly acted as a catalyst of existing trends, such as the geopolitical competition between the United States (US) and China – which has worsened, also due to the outbreak of the disease. As for the armed forces, in several NATO countries including France, Italy and the United Kingdom (UK), they have been called to operate in support of civilian authorities to deal with Covid-related aspects such as field hospitals, logistics, law enforcement, Covid tests or the vaccines’ distribution – and NATO itself provided support through its bodies such as the Euro-Atlantic Disaster Response Coordination Centre (EADRCC)

    Entity Linking meets Word Sense Disambiguation: A Unified Approach

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    Entity Linking (EL) and Word Sense Disambiguation (WSD) both address the lexical ambiguity of language. But while the two tasks are pretty similar, they differ in a fundamental respect: in EL the textual mention can be linked to a named entity which may or may not contain the exact mention, while in WSD there is a perfect match between the word form (better, its lemma) and a suitable word sense. In this paper we present Babelfy, a unified graph-based approach to EL and WSD based on a loose identification of candidate meanings coupled with a densest subgraph heuristic which selects high-coherence semantic interpretations. Our experiments show state-ofthe-art performances on both tasks on 6 different datasets, including a multilingual setting. Babelfy is online at http://babelfy.orgEntity Linking (EL) and Word Sense Disambiguation (WSD) both address the lexical ambiguity of language. But while the two tasks are pretty similar, they differ in a fundamental respect: in EL the textual mention can be linked to a named entity which may or may not contain the exact mention, while in WSD there is a perfect match between the word form (better, its lemma) and a suitable word sense. In this paper we present Babelfy, a unified graph-based approach to EL and WSD based on a loose identification of candidate meanings coupled with a densest subgraph heuristic which selects high-coherence semantic interpretations. Our experiments show state-ofthe-art performances on both tasks on 6 different datasets, including a multilingual setting. Babelfy is online at http://babelfy.or
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