Performance evaluation of a Ball Screw mechanism through a multibody dynamic model

Ball screws are mechanism to convert the rotational into linear motion and viceversa and are widespread in a variety of different sectors. A detailed high-fidelity dynamic mathematical model of such component is paramount in several fields and, in particular, in the definition of a PHM system for flight control EMAs in order to increase their reliability. In fact they can be used as a virtual test bench on which inject artificial defects and study their effect on specific indicators. This paper presents a MBD model of a single-nut ball screw with internal recirculation able of describing the full dynamic of each internal component allowing a more in-depth understanding of the system behavior and poses the basis for PHM-oriented analyses on different degradations

On the effects of strain wave gear kinematic errors on the behaviour of an electro-mechanical flight control actuator for eVTOL aircrafts

In recent years, the increasingly growing overcrowding of urban environments and the resulting road traffic congestion have pushed toward the search for alternative mobility solutions, among which there are novel Urban Air Mobility (UAM) technologies. The UAM, together with the development of electric actuation systems, would allow decongesting the streets by exploiting the sky using electric Vertical Take-Off and Landing (eVTOL) aircrafts. Urban air mobility vehicles are primarily based on fully electrical flight control systems with rotary output. Since such technology is relatively new and unproven, Prognostic and Health Management (PHM) algorithms, able to continuously monitor the health status of such systems, are of particular interest. The diffusion of these systems strongly depends on the general confidence of possible customers. The present paper proposes a preliminary study on the effects of the kinematic error of a Strain Wave Gear (SWG), the most used reducer for this kind of applications, on the behaviour of an Electro-Mechanical Actuator (EMA) used as a flight control actuator for an eVTOL aircraft. The simulation results show how the unavoidable kinematic error affects the EMA performances and how its presence can be detected and quantified in strain wave gears

Influência do espaçamento e da população de plantas de sorgo sacarino em diferentes épocas semeadura.

O trabalho objetivou avaliar a interferência do espaçamento entrelinhas e população de plantas sobre a produção do sorgo sacarino em duas épocas de semeadura, safra e safrinha. Os experimentos foram conduzidos na Embrapa Milho e Sorgo, em Sete Lagoas (MG), em Latossolo Vermelho Distrófi co, na safra 2011/2012. Para as duas épocas de semeadura, as parcelas foram compostas por cinco espaçamentos entrelinhas (50; 60; 70; e 80cm e linha dupla 100x50x50cm), e as subparcelas por quatro populações de plantas de sorgo sacarino (80.000, 100.000, 120.000 e 140.000 plantas ha-1). O delineamento utilizado foi em blocos ao acaso (DBC), com três repetições. Utilizou-se a variedade de sorgo sacarino BRS506. O experimento de safra foi implantado em novembro/2011 e de safrinha em março/2012. A época de semeadura no período de safra resultou em maior rendimento de matéria fresca de colmos, matéria fresca de biomassa total, massa de caldo e Brix do sorgo sacarino, independente do arranjo de plantas. O espaçamento de 50cm entrelinhas resultou em maior produção de biomassa total e massa de caldo ha-1, independente da época de semeadura. O espaçamento duplo resultou em valores similares ao espaçamento de 80cm, para as principais variáveis produtivas, independente da época de semeadura. As populações de plantas não influenciaram o rendimento de matéria fresca de colmos e massa de caldo, independente da época de semeadura

Leveraging Semantic Web Service Descriptions for Validation by Automated Functional Testing

Recent years have seen the utilisation of Semantic Web Service descriptions for automating a wide range of service-related activities, with a primary focus on service discovery, composition, execution and mediation. An important area which so far has received less attention is service validation, whereby advertised services are proven to conform to required behavioural specifications. This paper proposes a method for validation of service-oriented systems through automated functional testing. The method leverages ontology-based and rule-based descriptions of service inputs, outputs, preconditions and effects (IOPE) for constructing a stateful EFSM specification. The specification is subsequently utilised for functional testing and validation using the proven Stream X-machine (SXM) testing methodology. Complete functional test sets are generated automatically at an abstract level and are then applied to concrete Web services, using test drivers created from the Web service descriptions. The testing method comes with completeness guarantees and provides a strong method for validating the behaviour of Web services

MAPK15 protects from oxidative stress-dependent cellular senescence by inducing the mitophagic process

Mitochondria are the major source of reactive oxygen species (ROS), whose aberrant production by dysfunctional mitochondria leads to oxidative stress, thus contributing to aging as well as neurodegenerative disorders and cancer. Cells efficiently eliminate damaged mitochondria through a selective type of autophagy, named mitophagy. Here, we demonstrate the involvement of the atypical MAP kinase family member MAPK15 in cellular senescence, by preserving mitochondrial quality, thanks to its ability to control mitophagy and, therefore, prevent oxidative stress. We indeed demonstrate that reduced MAPK15 expression strongly decreases mitochondrial respiration and ATP production, while increasing mitochondrial ROS levels. We show that MAPK15 controls the mitophagic process by stimulating ULK1-dependent PRKN Ser108 phosphorylation and inducing the recruitment of damaged mitochondria to autophagosomal and lysosomal compartments, thus leading to a reduction of their mass, but also by participating in the reorganization of the mitochondrial network that usually anticipates their disposal. Consequently, MAPK15-dependent mitophagy protects cells from accumulating nuclear DNA damage due to mitochondrial ROS and, consequently, from senescence deriving from this chronic DNA insult. Indeed, we ultimately demonstrate that MAPK15 protects primary human airway epithelial cells from senescence, establishing a new specific role for MAPK15 in controlling mitochondrial fitness by efficient disposal of old and damaged organelles and suggesting this kinase as a new potential therapeutic target in diverse age-associated human diseases