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Friction Modelling for Tube Hydroforming Processes : A Numerical and Experimental Study with Different Viscosity Lubricants
Full text linkThe final quality of sheet and tube metal–formed components strongly depends on the tribology and friction conditions between the tools and the material to be formed. Furthermore, it has been recently demonstrated that friction is the numerical input parameter that has the biggest effect in the numerical models used for feasibility studies and process design. For these reasons, industrial dedicated software packages have introduced friction laws which are dependent on sliding velocity, contact pressure and sometimes strain suffered by the sheet, and currently, temperature dependency is being implemented as it has also a major effect on friction. In this work, three lubricants having different viscosity have been characterized using the tube-sliding test. The final aim of the study is to fit friction laws that are contact pressure and sliding velocity dependent for their use in tube hydroforming modeling. The tests performed at various contact pressures and velocities have demonstrated that viscosity has a major effect on friction. Experimental hydroforming tests using the three different lubricants have corroborated the importance of the lubricant in the final forming of a triangular shape. The measurement of the axial forces and the final principal strains of the formed tubes have shown the importance of using advanced friction laws to properly model the hydroforming process using the finite element modeling
Elementos facilitadores para la re-significación de la práctica educativa en estudiantes universitarias de educación infantil
Full text linkEl objetivo de este estudio de caso es analizar qué elementos pueden facilitar la
re-significación de la práctica educativa en estudiantes universitarias de Educación
infantil. El artículo analiza el contenido de los seminarios en los que ocurre la reflexión
conjunta, la entrevista a la tutora y el cuestionario que responden las 13 estudiantes
en prácticas. Los resultados sugieren que la re-significación acontece en la fase de
actividad interactiva denominada interpretación y las ayudas de la tutora que han sido
clave para la re-significación de la práctica son: ayudas dialógicas; las dirigidas a la
identificación de factores; las orientadas a la construcción de un marco interpretativo;
y las ayudas dirigidas al establecimiento de relaciones con experiencias previas, con
la situación analizada y con conocimientos académicos.The objective of this case study is to define the elements that can facilitate attaching
new meaning to student teaching among undergraduate students majoring in early
childhood education. The article analyzes the content of seminars of joint reflection,
interviews with the student teacher supervisor, and a questionnaire completed by
thirteen student teachers. The results suggest that attaching new significance occurs
in the interactive phase known as interpretation and that the forms of assistance from
the student teacher supervisor that have been key in attaching new significance to
student teaching are: help through dialog, help directed to identifying factors, help
in constructing an interpretative framework, and help in establishing associations
with previous experiences, with the analyzed situation, and with academic knowledge
An overview of Industry 4.0 Applications for Advanced Maintenance Services
Full text linkManufacturing today has experienced dynamic changes imposed by social-technical systems that address economic, social and sustainable requirements. Furthermore, the technologies in Industry 4.0 have also brought many smart applications to advance manufacturing to the next level of development. In a focused sense, maintenance plays a key role in manufacturing to create value propositions—extension of equipment useful life and enhancement in overall equipment effectiveness—for stakeholders towards economics and sustainability. In this context, the maintenance services that create the value propositions are not only delivered as after-sales maintenance services but developed to advanced maintenance services embedded into Industry 4.0 applications. To provide a clearer picture of the development, this work aims to review and categorize the maintenance services in three groups—basic services, intermediate services, advanced services—associated with technologies in Industry 4.0 across the life-cycle maintenance service
Survey on decentralized congestion control methods for vehicular communication
Full text linkVehicular communications have grown in interest over the years and are nowadays recognized as a pillar for the Intelligent Transportation Systems (ITSs) in order to ensure an efficient management of the road traffic and to achieve a reduction in the number of traffic accidents. To support the safety applications, both the ETSI ITS-G5 and IEEE 1609 standard families require each vehicle to deliver periodic awareness messages throughout the neighborhood. As the vehicles density grows, the scenario dynamics may require a high message exchange that can easily lead to a radio channel congestion issue and then to a degradation on safety critical services. ETSI has defined a Decentralized Congestion Control (DCC) mechanism to mitigate the channel congestion acting on the transmission parameters (i.e., message rate, transmit power and data-rate) with performances that vary according to the specific algorithm. In this paper, a review of the DCC standardization activities is proposed as well as an analysis of the existing methods and algorithms for the congestion mitigation. Also, some applied machine learning techniques for DCC are addressed
Less Rare-Earth Electromagnetic Design for a High-Performance Permanent Magnet Motor
Full text linkThis paper presents an electromagnetic design alternative using the so-called banana-shaped magnets, achieving magnet weight reduction of 21.82% for the same performance as the baseline motor in the case study. Typically, parallel magnetization is used in this topology because it provides the manufacturing advantage of not building a specific magnetizing device required to achieve radial magnetization. Therefore, as its main contribution, this paper proposes using tilted magnetization, demonstrating that the performance is better than the conventional way of applying parallel magnetization in banana-shaped motors but still using parallel magnetization. Because of the performance improvement for the same motor structure, magnet weight reduction is possible for a new design with the same performance as the baseline motor. In addition, this paper presents the workflow followed to obtain the less rare-earth design motor candidate using tilted magnetization
Uncertainty-aware Robustness Assessment of Industrial Elevator Systems
Full text linkIndustrial elevator systems are commonly used software systems in our daily lives, which operate in uncertain environments such as unpredictable passenger traffic, uncertain passenger attributes and behaviors, and hardware delays. Understanding and assessing the robustness of such systems under various uncertainties enable system designers to reason about uncertainties, especially those leading to low system robustness, and consequently improve their designs and implementations in terms of handling uncertainties. To this end, we present a comprehensive empirical study conducted with industrial elevator systems provided by our industrial partner Orona, which focuses on assessing the robustness of a dispatcher, i.e., a software component responsible for elevators’ optimal scheduling. In total, we studied 90 industrial dispatchers in our empirical study. Based on the experience gained from the study, we derived an uncertainty-aware robustness assessment method (named UncerRobua) comprising a set of guidelines on how to conduct the robustness assessment and a newly proposed ranking algorithm, for supporting the robustness assessment of industrial elevator systems against uncertainties
Lanki kuadernoak = Cuadernos Lanki ; 16
No full textEsku artean duzun liburuxka honekin, kooperatibismoaren sustraietan sakontzeko aukera
duzu. Aurrekoari segida ematera datorren argitalpena da. Orduan, XVIII. eta XIX.
mendeetan, industria-kapitalismoari aurre eginez, langile eta herri-sektoreen inguruneetan
ernaldu ziren antolaketa-praktikak eta elkartegintza dinamikak aztertu bagenituen,
oraingoan sozialista asoziazionista deiturikoen pentsamendua eta ekinbideak izango
ditugu aztergai. Izan ere, bi horiek dira, Rochdaleko kooperatiba-esperientziaren mugarriaren
aurretik, kooperatibismoaren sorreraren iturri nagusiak.
Idazki honetan, hortaz, sozialista asoziazionistek eredu kooperatiboaren eraikuntzan
egin zuten ekarpena, teorikoa eta praktikoa, aztertuko dugu. Britainia Handiko Robert
Owen eta William King doktorea eta Frantziako Charles Fourier, Philippe Buchez eta Louis
Blanc autoreak aztertuko ditugu. Liberalismoaren erregimen indibidualista eta lehiakorra
gainditu eta elkartasunean oinarrituriko gizarte-eredua eraikitzeko, elkarkidetzan
oinarrituriko elkarteak sustatu zituzten. Batzuetan funtzionamendu-arau eta antolaketa-
eredu berritzaileak asmatuz, eta, besteetan, elkartegintza-eredu berri horien esperimentazio
praktikoak garatuz. Ez zuten kooperatiba hitza erabiltzen –berriagoa baita–,
baina zalantzarik ez dago sustatu zituzten kontsumo- edo ekoizpen-elkarteak egungo
kooperatiben aurrekari zuzenak direla. Sozialista asoziazionista horien proposamenetan,
hortaz, kooperatibismoaren oinarri ideologiko hainbaten iturriak daude. Gerora Rochdaleko
kooperatiba-esperientziak eredu bilakatuko dituen printzipio eta arau asko ere garai
honetakoak dira. Horiek guztiak arakatuko ditugu liburuxka honetan
Mechanical properties of friction induced nanocrystalline pearlitic steel
Full text linkNanocrystalline structured variants of commercially available alloys have shown potential for boosting the mechanical properties of these materials, leading to a reduction in waste and thereby retaining feasible supply chains. One approach towards achieving these nanostructures resides in frictional treatments on manufactured parts, leading to differential refinement of the surface structure as compared to the bulk material. In this work the machining method is considered to be a testing platform for the formation and study of frictional nanostructured steel, assembly of which is stabilized by fast cooling of the produced chip. Analysis of the mechanical properties has shown extraordinary results at the surface, over 2000 MPa of strength on AISI1045 steel, more than three times the strength of the base material, demonstrating at the same time a reduction of 15% in the elastic modulus. The microscopic analysis suggests a reassembly of the elements in a new lattice of carbon supersaturated nano-ferrite
A Novel Model for Vulnerability Analysis through Enhanced Directed Graphs and Quantitative Metrics
Full text linkThe rapid evolution of industrial components, the paradigm of Industry 4.0, and the new connectivity features introduced by 5G technology all increase the likelihood of cybersecurity incidents. Such incidents are caused by the vulnerabilities present in these components. Designing a secure system is critical, but it is also complex, costly, and an extra factor to manage during the lifespan of the component. This paper presents a model to analyze the known vulnerabilities of industrial components over time. The proposed Extended Dependency Graph (EDG) model is based on two main elements: a directed graph representation of the internal structure of the component, and a set of quantitative metrics based on the Common Vulnerability Scoring System (CVSS). The EDG model can be applied throughout the entire lifespan of a device to track vulnerabilities, identify new requirements, root causes, and test cases. It also helps prioritize patching activities. The model was validated by application to the OpenPLC project. The results reveal that most of the vulnerabilities associated with OpenPLC were related to memory buffer operations and were concentrated in the libssl library. The model was able to determine new requirements and generate test cases from the analysis
Life cycle cost analysis of tomato production in innovative urban agriculture systems
Full text linkThe construction of innovative urban agriculture systems in cities has increased due to food and environmental concerns. While the environmental performance of urban agriculture has been extensively studied, research on the life cycle costs of urban agriculture systems is still limited, which constraints sustainability-oriented decision-making processes. This paper analyses the economic viability of tomato production cycle in an innovative building with an integrated urban agriculture system in rooftop by applying the life cycle cost methodology. The data was collected from direct measurements and internal and external sources. To calculate labour costs, a customised data collection sheet was created. The results are presented by life cycle stage, cost category and type of cost (fixed & variable). Results indicate that the main cost drivers for tomato production are labour (24.7%), the rooftop greenhouse structure (15%), external pest control (12.6%), and rainwater consumption (9.5%), accounting altogether for 61.8% of the total costs. Accordingly, cost reduction solutions are evaluated through the development of sensitivity scenarios (rooftop greenhouse structure design, tap water use and rainwater tank size), including the consideration of another relevant aspect, such as the role of the production level output, as it can greatly influence the economic viability and profitability. Finally, the main environmental and social aspects of these urban production systems are also included