Jet bundles on Gorenstein curves and applications

In the last twenty years a number of papers appeared aiming to construct locally free replacements of the sheaf of principal parts for families of Gorenstein curves. The main goal of this survey is to present to the widest possible audience of mathematical readers a catalogue of such constructions, discussing the related literature and reporting on a few applications to classical problems in Enumerative Algebraic Geometry.Comment: Minor revisions, improved expositio

Gas Loss by Ram Pressure Stripping and Internal Feedback From Low Mass Milky Way Satellites

The evolution of dwarf satellites of the Milky Way is affected by the combination of ram pressure and tidal stripping, and internal feedback from massive stars. We investigate gas loss processes in the smallest satellites of the Milky Way using three-dimensional, high resolution, idealized wind tunnel simulations, accounting for gas loss through both ram pressure stripping and expulsion by supernova feedback. Using initial conditions appropriate for a dwarf galaxy like Leo T, we investigate whether or not environmental gas stripping and internal feedback can quench these low mass galaxies on the expected timescales, shorter than 2 Gyr. We find that supernova feedback contributes negligibly to the stripping rate for these low star formation rate galaxies. However, we also find that ram pressure stripping is less efficient than expected in the stripping scenarios we consider. Our work suggests that, although ram pressure stripping can eventually completely strip these galaxies, other physics is likely at play to reconcile our computed stripping times with the rapid quenching timescales deduced from observations of low mass Milky Way dwarf galaxies. We discuss the roles additional physics may play in this scenario, including host-satellite tidal interactions, cored vs. cuspy dark matter profiles, reionization, and satellite pre-processing. We conclude that a proper accounting of these physics together is necessary to understand the quenching of low mass Milky Way satellites.Comment: 16 pages, 7 figures. Accepted for publication in Ap

Energy release as a parameter for fatigue design of additive manufactured metals

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Inductor losses estimation in DC-DC converters by means of averaging technique

A suitable inductor modeling for power electronic DC-DC converters is presented in this paper. It is developed with the aim of improving inductor losses estimation achievable by averaged models, which inherently neglect inductor current ripple. In order to account for its contribution to the overall inductor losses, an appropriate parallel resistance is thus enclosed into the inductor model, whose value should be chosen in accordance with the DC-DC converter operating conditions. This allows the development of improved averaged models of DC-DC converters, especially in terms of power losses estimation. The effectiveness of the proposed modeling approach has been validated through a simulation study, which refers to the case of a boost DC-DC converter and is performed by means of a suitable circuit simulator designed for rapid modelling of switching power systems (SIMetrix/SIMPLIS)

The global impact of stellar winds and supernovae on the interstellar medium

The interstellar medium is an extremely heterogeneous mixture of gas and dust which fills the space between stars in galaxies. The life-cycle of stars is deeply connected with the presence of this medium. Massive stars form from very high density/low temperature gas and evolve for millions of years. They emit ionising radiation, blow powerful winds from their surface and, at the end of their lifetime, explode as supernovae, thereby heating up and compressing the surrounding material. These stellar feedback processes are fundamental, since they are able to influence the evolution of the interstellar medium at different scales and eventually to promote or deter further star formation events. In this thesis, we investigate the impact of stellar winds and supernovae on the interstellar medium by performing three-dimensional, Adaptive-Mesh-Refinement, hydrodynamic simulations at intermediate (pc-kpc) scales. We study how different assumptions on the position of supernova explosions drive completely different properties of the gas within disc galaxies. Supernovae are placed either at random positions, in density peaks, or both. Explosions located in density peaks do not produce hot gas due to large radiative losses and atomic hydrogen dominates the mass. Random supernovae create a large volume filling hot phase that compresses the gas into small clumps and the majority of the mass is in the form of molecular hydrogen. We then show how the combination of stellar winds and supernovae is able to regulate the otherwise over-efficient star formation process. We model star formation self-consistently via sink particles and we demonstrate how stellar winds are able to reduce the amount of gas converted into stars both at local and global scales. The inclusion of supernovae produce a hot, over-pressurised phase responsible for outflows launching

A pluralistic approach to economic and business sustainability: A critical meta‐synthesis of foundations, metrics, and evidence of human and local development

Wellbeing and sustainability are at the center of development studies and economics, being the kernel of theories and policies. Analyzing such complex phenomena implies taking into account both the economic and business spheres. In this regard, the human and local dimensions of development have assumed central importance in determining definitions, measurements, and policies and reveal decisive implications for economic ethics and long‐term development perspectives. This work intends to draw a theoretical excursus on the nexus between the human, sustainable, and local dimensions of development and wide‐ranging business theories. For this scope, the paper adopts a pluralistic approach for determining diverse conceptual insights. Entangling holistic lenses, this study explores the theoretical foundations, measurements, and experiences that have characterized the recent development theory and applied evidence in economics and business. The review detects some evidence in the global and the Italian experiences that can reveal important lessons for theorists, policymakers, and practitioners in development, sustainability, and business

On the chaotic nature of electro-discharge machining

The long-accepted thermoelectric model for electro-discharge machining is being brought into question. Several experimental facts prompt the proposal of a new theory based on the effect of gap pollution on the ignition of discharges. The first experimental proof comes from the recently reported observation of debris chains and clusters. In this view, each step of the process depends on the previous ones through a deterministic relation, even if the overall evolution is unpredictable. The paper establishes mathematical grounds for the abovementioned intuitions by setting up and solving a recursive equation for the machining energy employed at each discharge event. By means of numerical and algebraic tools, the above equation is studied and shows a chaotic evolution similar to that of the logistic map. Results reconcile the apparent paradox between deterministic nature and stochastic localization of the discharges and introduce a description of the chaotic dynamics of electro-discharge processes

Impact of additive manufacturing on engineering education – evidence from Italy

Purpose - The purpose of this paper is to evaluate how the direct access to additive manufacturing (AM) systems impacts on education of future mechanical engineers, within a Master's program at a top Italian University. Design/methodology/approach - A survey is specifically designed to assess the relevance of entry-level AM within the learning environment, as a tool for project development. The survey is distributed anonymously to three consecutive cohorts of students who attended the course of "computer-aided production (CAP)", within the Master of Science Degree in Mechanical Engineering at Politecnico di Torino. The course includes a practical project, consisting in the design of a polymeric product with multiple components and ending with the production of an assembled prototype. The working assembly is fabricated by the students themselves, who operate a fused deposition modelling (FDM) machine, finish the parts and evaluate assemblability and functionality. The post-course survey covers diverse aspects of the learning process, such as: motivation, knowledge acquisition, new abilities and team-working skills. Responses are analyzed to evaluate students' perception of the usefulness of additive technologies in learning product design and development. Among the projects, one representative case study is selected and discussed. Findings - Results of the research affirm a positive relationship of access to AM devices to perceived interest, motivation and ease of learning of mechanical engineering. Entry-level additive technologies offer a hands-on experience within academia, fostering the acquisition of technical knowledge. Research limitations/implications - The survey is distributed to more than 200 students to cover the full population of the CAP course over three academic years. The year the students participated in the CAP course is not tracked because the instructor was the same and there were no administrative differences. For this reason, the survey administration might be a limitation of the current study. In addition to this, no gender distinction is made because historically, the percentage of female students in Mechanical Engineering courses is about 10 per cent or lower. Although the answers to the survey are anonymous, only 37 per cent of the students gave a feedback. Thus, on the one hand, impact assessment is limited to a sample of about one-third of the complete population, but, on the other hand, the anonymity ensures randomization in the sample selection. Practical implications - Early exposure of forthcoming designers to AM tools can turn into a "think-additive" approach to product design, that is a groundbreaking conception of geometries and product functionalities, leading to the full exploitation of the possibilities offered by additive technologies. Social implications - Shared knowledge can act as a springboard for mass adoption of AM processes. Originality/value - The advantages of adopting AM technologies at different levels of education, for diverse educational purposes and disciplines, are well assessed in the literature. The innovative aspect of this paper is that the impact of AM is evaluated through a feedback coming directly from mechanical engineering students

Energy harvesting applied to smart shoes

The appeal of energy harvesting systems lies in the possibility of capturing free energy that would be dissipated and is therefore obtainable without costs. Today, advanced techniques and devices exist for capturing from the environment, storing, and managing quotas of natural energy, which are made available in the form of electrical energy. At the same time, the most recent microprocessors grant an extremely high power efficiency, which permits their operation with minimal power consumption. As a consequence, low-consuming devices can be power supplied by using energy harvesting systems. If this concept is applied to wearable electronics, the most efficient choice is that of exploiting the energy released when the users walk, by developing systems that are embedded in the shoe sole. At each step, the force exerted on the device can be transformed into a relatively high amount of electrical energy, for example by using piezoelectric elements and electromagnetic induction systems. The paper describes the design of four different solutions for smart shoes that make use of energy harvesting apparatuses for the power supply of sensors and complex monitoring systems, for example aimed at GPS localization. An initial comparative assessment of the four architectures is reported, by weighing production costs, ease of manufacture and energy harvesting performance

The Corrosion Behaviour of Additively Manufactured AlSi10Mg Parts Compared to Traditional Al Alloys

Additive manufacturing of metal parts in the motorsport industry is becoming a decisive technology for producing lightweight and rigid parts, with increasing applications as the costs decrease. Among the available metal alloys, AlSi10Mg is one of the most widely used. In this paper, the corrosion resistance of additively manufactured AlSi10Mg is compared with that of other traditionally manufactured aluminium alloys widespread in the automotive industry. Several potentially corrosive agents, typical of vehicle applications, were used: salty water, motor oil, suspension oil, cooling fluid and gasoline. Corrosion tests were conducted at both room temperature and 90 C. The effects of heat and surface treatments were evaluated separately. The samples were visually inspected and weighed to evaluate the corrosion rate with the aid of SEM and EDS analysis. Additively manufactured AlSi10Mg generally showed better corrosion resistance in the stress-relieved condition as compared to the T6-treated state, with slightly better results for the polished samples. Motor oil, suspension oil, cooling fluid and gasoline did not significantly corrode the specimens, except for the T6-treated AlSi10Mg samples at 90 C. However, the corrosion rate was always higher than traditionally manufactured aluminium alloys tested for comparison