Propeller geometry optimization for pressure pulses reduction: an analysis of the influence of the rake distribution

The evaluation of pressure pulses is a current issue for any high-performance propeller design. It has been addressed experimentally, by means of model tests, and numerically but in most cases the analysis has been limited to the verification of a given geometry (or, at least of few configurations) identified at the end of a traditional design loop. A more direct inclusion of pressure pulses evaluation in the design procedure, for instance by very attractive multi-objective optimization approaches, could be beneficial, especially if more accurate codes may be exploited. Among the others, BEM represent an acceptable compromise between computational costs and accuracy with the further advantage, with respect to lower fidelity approaches, to account for effects of geometrical haracteristics (such as rake distribution) which are often defined only according to designer experience and special needs. However, if the ability of the BEM methods to predict propeller performance and cavitation extension is well documented, the direct computation of pressure pulses may be less reliable, especially in correspondence to heavy cavitating conditions, requiring further validations in particular when the influence of characteristics such as rake distribution, hardly addressed in literature also from the experimental point of view, are considered. Cavitation tunnel test, BEM and RANS calculations have been consequently carried out for two propellers, designed for the same functioning conditions with different rake distributions, in order to stress the capabilities and the limitations of the numerical approaches in dealing with cavitation, pressure pulses predictions and the capability to discriminate between slightly different geometries in the light of their possible application in a design by optimization procedure

Disks, spikes, and clouds: distinguishing environmental effects on BBH gravitational waveforms

Future gravitational wave interferometers such as LISA, Taiji, DECIGO, and TianQin, will enable precision studies of the environment surrounding black holes. In this paper, we study intermediate and extreme mass ratio binary black hole inspirals, and consider three possible environments surrounding the primary black hole: accretion disks, dark matter spikes, and clouds of ultra-light scalar fields, also known as gravitational atoms. We present a Bayesian analysis of the detectability and measurability of these three environments. Focusing for concreteness on the case of a detection with LISA, we show that the characteristic imprint they leave on the gravitational waveform would allow us to identify the environment that generated the signal, and to accurately reconstruct its model parameters.Comment: 8 pages, 4 figures, 2 tables plus appendice

Nidogen-1 is a novel extracellular ligand for the NKp44 activating receptor

The release of soluble ligands of activating Natural Killer (NK) cell receptors may represent a regulatory mechanism of NK cell function both in physiologic and in pathologic conditions. Here, we identified the extracellular matrix protein Nidogen-1 (NID1) as a ligand of NKp44, an important activating receptor expressed by activated NK cells. When released as soluble molecule, NID1 regulates NK cell function by modulating NKp44-induced IFN-\u3b3 production or cytotoxicity. In particular, it also modulates IFN-\u3b3 production induced by Platelet-Derived Growth Factor (PDGF)-DD following NKp44 engagement. We also show that NID1 may be present at the cell surface. In this form or when bound to a solid support (bNID1), NID1 fails to induce NK cell cytotoxicity or cytokine release. However, analysis by mass spectrometry revealed that exposure to bNID1 can induce in human NK cells relevant changes in the proteomic profiles suggesting an effect on different biological processes

NKp44-NKp44 Ligand Interactions in the Regulation of Natural Killer Cells and Other Innate Lymphoid Cells in Humans

Natural Killer (NK) cells are potent cytotoxic cells belonging to the family of Innate Lymphoid Cells (ILCs). Their most characterized effector functions are directed to the control of aberrant cells in the body, including both transformed and virus-infected cells. NK cell-mediated recognition of abnormal cells primarily occurs through receptor-ligand interactions, involving an array of inhibitory and activating NK receptors and different types of ligands expressed on target cells. While most of the receptors have become known over many years, their respective ligands were only defined later and their impressive complexity has only recently become evident. NKp44, a member of Natural Cytotoxicity Receptors (NCRs), is an activating receptor playing a crucial role in most functions exerted by activated NK cells and also by other NKp44+ immune cells. The large and heterogeneous panel of NKp44 ligands (NKp44L) now includes surface expressed glycoproteins and proteoglycans, nuclear proteins that can be exposed outside the cell, and molecules that can be either released in the extracellular space or carried in extracellular vesicles. Recent findings have extended our knowledge on the nature of NKp44L to soluble plasma glycoproteins, such as secreted growth factors or extracellular matrix (ECM)-derived glycoproteins. NKp44L are induced upon tumor transformation or viral infection but may also be expressed in normal cells and tissues. In addition, NKp44-NKp44L interactions are involved in the crosstalk between NK cells and different innate and adaptive immune cell types. NKp44 expression in different ILCs located in tissues further extends the potential role of NKp44-NKp44L interactions

Multilayer networks and route entry into the airline industry: Evidence from the U.S. domestic market

In this paper we apply elements of multilayer network theory to the airline industry and study route entry into the U.S. domestic market. We find that airlines tend to follow the market leader and enter a route already served by the incumbent. Moreover, using multilayer network variables, our analysis confirms that entry is more likely when the airline operates other routes at the two endpoints of the target route. On the managerial side, our results may help each airline to foresee and therefore anticipate the competitors’ entry move. On the policy side, our approach, based on multilayer network theory, may be adopted by competition authorities to detect possible firm’s practices that can result from airlines’ network, and, more generally, by national public authorities to understand the centrality of each airline’s network in each country

Advancements and Research Trends in Microgrids Cybersecurity

Microgrids are growing in importance in the Smart Grid paradigm for power systems. Microgrid security is becoming crucial since these systems increasingly rely on information and communication technologies. Many technologies have been proposed in the last few years for the protection of industrial control systems, ranging from cryptography, network security, security monitoring systems, and innovative control strategies resilient to cyber-attacks. Still, electrical systems and microgrids present their own peculiarities, and some effort has to be put forth to apply cyber-protection technologies in the electrical sector. In the present work, we discuss the latest advancements and research trends in the field of microgrid cybersecurity in a tutorial form

A Possible Smart Metering System Evolution for Rural and Remote Areas Employing Unmanned Aerial Vehicles and Internet of Things in Smart Grids

The way of generating and distributing energy throughout the electrical grid to all users is evolving. The concept of Smart Grid (SG) took place to enhance the management of the electrical grid infrastructure and its functionalities from the traditional system to an improved one. To measure the energy consumption of the users is one of these functionalities that, in some countries, has already evolved from a periodical manual consumption reading to a more frequent and automatic one, leading to the concept of Smart Metering (SM). Technology improvement could be applied to the SM systems to allow, on one hand, a more efficient way to collect the energy consumption data of each user, and, on the other hand, a better distribution of the available energy through the infrastructure. Widespread communication solutions based on existing telecommunication infrastructures instead of using ad-hoc ones can be exploited for this purpose. In this paper, we recall the basic elements and the evolution of the SM network architecture focusing on how it could further improve in the near future. We report the main technologies and protocols which can be exploited for the data exchange throughout the infrastructure and the pros and cons of each solution. Finally, we propose an innovative solution as a possible evolution of the SM system. This solution is based on a set of Internet of Things (IoT) communication technologies called Low Power Wide Area Network (LPWAN) which could be employed to improve the performance of the currently used technologies and provide additional functionalities. We also propose the employment of Unmanned Aerial Vehicles (UAVs) to periodically collect energy consumption data, with evident advantages especially if employed in rural and remote areas. We show some preliminary performance results which allow assessing the feasibility of the proposed approach

Cybersecurity Issues in Communication-Based Electrical Protections

Cybersecurity is becoming a fundamental issue in Smart Grids. In the last past years, there have been remarkable advances in technologies for enhancing the security of electrical systems. Still, some systems shows severe vulnerabilities. One of them is represented by communication-based electrical protection. The present work analyzes vulnerabilities in such type of control networks. We analyze the attack models to communication-based electrical protection systems, discussing the impact of the implementation of IEC 62351 on these vulnerabilities. We also discuss possible countermeasures which can be useful to address the discussed vulnerabilities

A Framework for Network Security Verification of Automated Vehicles in the Agricultural Domain

The agricultural sector increasingly relies on automated vehicles. These machines are often based on a CANbus control network and equipped with different wireless interfaces to implement different functionalities, such as remote control through radio links, GPS-based localization, and Wi-Fi-based data exchange. Nevertheless, CANbus presents severe vulnerabilities that expose these vehicles to cyberattacks. In this context, it is crucial to develop efficient procedures for network security verification of automated agricultural vehicles. The present work proposes a framework for evaluating the network security of agricultural vehicles based on four main dimensions: CANbus Security and Network Segmentation, Remote control based on Radio-Links, Wireless Gateways, and GPS security. We presents a testbed we are developing to test the proposed procedures, also discussing the related methods and procedures

Detecting System Fault/Cyberattack within a Photovoltaic System Connected to the Grid: A Neural Network-Based Solution

The large spread of Distributed Energy Resources (DERs) and the related cyber-security issues introduce the need for monitoring. The proposed work focuses on an anomaly detection strategy based on the physical behavior of the industrial process. The algorithm extracts some measures of the physical parameters of the system and processes them with a neural network architecture called autoencoder in order to build a classifier making decisions about the behavior of the system and detecting possible cyber-attacks or faults. The results are quite promising for a practical application in real systems