3,152 research outputs found
Tax-benefit systems, income distribution and work incentives in the European Union
In this paper we study the impact of tax-benefit systems on income inequality and work incentivesacross the 27 Member States of the European Union (EU). Using EUROMOD, the EU-wide taxbenefitmicrosimulation model, we disentangle the role of taxes, benefits and social insurancecontributions in influencing country specific Gini coefficients and Marginal Effective Tax Rates.The extent to which tax-benefit systems contribute to income redistribution and provide work incentives at the intensive margin is found to vary considerably across the 27 Member States of the EU. Our results further highlight the presence of a trade-off between income redistribution and work incentives across EU-27 countries
On the mass of supernova progenitors: the role of the CC reaction
A precise knowledge of the masses of supernova progenitors is essential to
answer various questions of modern astrophysics, such as those related to the
dynamical and chemical evolution of Galaxies. In this paper we revise the upper
bound for the mass of the progenitors of CO white dwarfs (\mup) and the lower
bound for the mass of the progenitors of normal type II supernovae (\mups). In
particular, we present new stellar models with mass between 7 and 10 \msun,
discussing their final destiny and the impact of recent improvements in our
understanding of the low energy rate of the \c12c12 reaction.Comment: To be published on the proceedings of NIC 201
An increase in the 12C + 12C fusion rate from resonances at astrophysical energies
Carbon burning powers scenarios that influence the fate of stars, such as the late evolutionary stages of massive stars1 (exceeding eight solar masses) and superbursts from accreting neutron stars2,3. It proceeds through the 12C + 12C fusion reactions that produce an alpha particle and neon-20 or a proton and sodium-23 - that is, 12C(12C, α)20Ne and 12C(12C, p)23Na - at temperatures greater than 0.4 × 109 kelvin, corresponding to astrophysical energies exceeding a megaelectronvolt, at which such nuclear reactions are more likely to occur in stars. The cross-sections 4 for those carbon fusion reactions (probabilities that are required to calculate the rate of the reactions) have hitherto not been measured at the Gamow peaks4 below 2 megaelectronvolts because of exponential suppression arising from the Coulomb barrier. The reference rate 5 at temperatures below 1.2 × 109 kelvin relies on extrapolations that ignore the effects of possible low-lying resonances. Here we report the measurement of the 12C(12C, α 0,1)20Ne and 12C(12C, p0,1)23Na reaction rates (where the subscripts 0 and 1 stand for the ground and first excited states of 20Ne and 23Na, respectively) at centre-of-mass energies from 2.7 to 0.8 megaelectronvolts using the Trojan Horse method 6,7 and the deuteron in 14N. The cross-sections deduced exhibit several resonances that are responsible for very large increases of the reaction rate at relevant temperatures. In particular, around 5 × 108 kelvin, the reaction rate is boosted to more than 25 times larger than the reference value5. This finding may have implications such as lowering the temperatures and densities 8 required for the ignition of carbon burning in massive stars and decreasing the superburst ignition depth in accreting neutron stars to reconcile observations with theoretical models3
Advanced Techniques for Design and Manufacturing in Marine Engineering
Modern engineering design processes are driven by the extensive use of numerical
simulations, and naval architecture as well as ocean engineering are no exception. Structural
design or fluid dynamic performance evaluation can only be carried out by means of several
dedicated pieces of software. Classical naval design methodology can take advantage of
the integration of these pieces of software, giving rise to more robust design in terms of
shape, structural and hydrodynamic performances, and manufacturing processes.
This Special Issue (SI) on “Advanced Techniques for Design and Manufacturing in
Marine Engineering”, published in the Journal of Marine Science and Engineering, aimed to
invite researchers and engineers from both academia and industry to publish the latest
progress in design and manufacturing techniques in marine engineering as well as to debate
current issues and future perspectives in this research area.
After a rigorous peer review process we accepted 11 papers [1–11], covering a wide
range of topics related to the themes proposed in the Special Issue. In [1], machine-learningbased
algorithms are developed in order to enhance the real-time decision process of
an AUV sailing yacht. In [2], topology optimization techniques and laser powder bed
fusion manufacturing have been synergically adopted to redesign the bulb of sailing yachts,
leading to drag reduction and improving overall boat performance. In [3], the topic of
sail design is discussed by means of numerical fluid structure interaction methods and
a practical tool is proposed to support the analyst during the design process of a yacht
sail plan. The sail design process is also investigated in [4] but using different tools,
such as combining a velocity prediction program, RANS computations, and analytical
approaches. The problem of grid generation in a CFD model has been studied in [5], where
the authors propose, for the particular shape of a submarine, an automated procedure
based on Cartesian adaptive grids. The applicability of a CFD numerical technique to a
complex biphase fluid medium is the key point of [6], where the robustness of the method
is tested to simulate the ventilation phenomenon occurring in stepped hull planing motor
yachts. In [7], an analytical tool incorporating the main dimensional naval coefficients of a
sailing boat is adopted during the early design stage, with the additional aim of quickly
predicting the overall resistance of the hull. In [8], different pieces of sensor information
have been used by the authors to train an algorithm able to control water sample collection
in deep water. Computational methods have been used in [9] to determine the resistance
of ship fuel tanks when subjected to an increased internal pressure. In [10], a simulation
model has been used to design a platform able to compensate for the wave action on a
vessel, with particular attention to the shape optimization of the structure in order to reduce
the total weight. Finally, in [11], CFD tools using moving meshes have been adopted to
simulate turbulent flows that originate in an oscillating water column device and move a
Savonius turbine
E-grocery logistics: exploring the gap between research and practice
Purpose: This paper investigates the logistics management in the e-grocery sector. It contrasts the key issues faced by practitioners and the topics addressed in the academic literature, to identify potential misalignments between research and practice and propose avenues for future efforts. Design/methodology/approach: This work adopts a twofold methodological approach. From an academic perspective, a systematic literature review (SLR) is performed to define the topics addressed so far by scholars when analysing e-grocery logistics. From a managerial perspective, a Delphi study is accomplished to identify the most significant issues faced by logistics practitioners in the e-grocery context and the associated significance. Findings: The study develops a conceptual framework, identifying and mapping the 9 main logistics challenges for e-grocery along 4 clusters, in the light of a logistics-related revision of the SCOR model: distribution network design (area to be served, infrastructures), order fulfilment process (picking, order storage, consolidation, delivery), logistics-related choices from other domains (product range, stock-out management) and automation. These elements are discussed along three dimensions: criticalities, basic and advanced/automation-based solutions. Finally, the main gaps are identified – in terms of both under-investigated topics (order storage and stock-out management) and investigated topics needing further research (picking and automation) – and research questions and hypotheses are outlined. Originality/value: This paper provides a threefold contribution, revolving around the developed framework. First, it investigates the state of the art about e-grocery logistics, classifying the addressed themes. Second, it explores the main issues e-grocery introduces for logistics practitioners. Third, it contrasts the two outcomes, identifying the misalignment between research and practice, and accordingly, proposing research directions
Logistics challenges of e-grocery last-mile delivery: a literature review
In recent years, e-commerce has been growing globally and online markets have undergone a radical transformation during Covid-19 Pandemic. In this context, Food and Grocery sector has expanded exponentially thus leading to a development of last-mile logistics which is the least efficient supply chain activity in terms of economic and environmental impact.
At the moment, B2C e-commerce players face multiple challenges due to logistics complexities and efficiency. On the other side, demand complexities rise from Service Level expectations, and consumers’ willingness to pay for logistics services.
Food and Grocery e-commerce has three main configurations: the enogastronomic e-commerce, the on-demand food delivery and the e-grocery. Among these, the third one has reported the highest growth during and after the Pandemic. However, beside complexities of e-commerce logistics, the online purchase of grocery products raises new challenges due to product peculiarities, logistics requirements and complexity of orders.
The aim of this work is therefore to investigate which are the main problems associated with last-mile delivery for e-grocery and which are the appropriate variables to describe them. In order to achieve this objective, a Systematic Literature Review has been performed to identify key issues addressed by scholars and existing typologies of last- mile delivery problems in this sector.
The contribution of this research is threefold: firstly, it analyses the state of the art of last-mile challenges for e- grocery from an academic perspective and proposes a classification. Secondly, the identification of logistics variables associated with identified problems highlights potential threats for E-grocery players. Therefore, this work supports managers to identify challenges in a structured way before planning appropriate countermeasures for the specific context. Thirdly, it identifies opportunities for future research directions
Smart metering and Internet of Things for efficient water management
Global water use has grown steadily in the past decade, and climate change will further worsen the levels of water stress. Another global issue lies in the ageing of water infrastructures, registering conspicuous water losses (40% in the Italian scenario). A great opportunity is represented by the exploitation of new technologies relating to IoT, namely smart meters, which can enable the prediction of water consumption, detect leaks, and customise the service. This paper assesses the economic and environmental impact of smart meters adoption for water consumption, by taking the Italian scenario as a reference context, through the development of an analytical model which considers the benefits and costs associated with their adoption, with the ultimate objective of evaluating the convenience of the investment. Data to feed the model was collected through secondary sources, literature reviews, and interviews with utility companies' employees. Results provide corroborating evidence of the positive impact of smart water meter adoption, both in economic and environmental terms, in particular by increasing the roll-out number, given the higher amount of data available and economies of scale to be exploited. The present study contributes to the academic literature by providing a comprehensive model that considers economic and environmental aspects of smart water adoption, which allows practitioners to have an insightful understanding of the involved variables in such investments
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