1,721,065 research outputs found
The weight distribution of codes over finite chain rings
Full text linkIn this work, we determine new linear equations for the weight distribution of linear codes over finite chain rings. The identities are determined by counting the number of some special submatrices of the parity-check matrix of the code. Thanks to these relations we are able to compute the full weight distribution of codes with small Singleton defects, such as MDS, MDR and AMDR codes
Energy-efficient frozen food transports: the Refrigerated Routing Problem
No full textGiven the growing importance of cold chains and the need to promote sustainable processes, energy efficiency in refrigerated
transports is investigated at operational level. The Refrigerated Routing Problem is defined, involving multi-drop deliveries
of palletised unit loads of frozen food from a central depot to clients. The objective is to select the route with minimum fuel
consumption for both traction and refrigeration. The problem formulation considers speed variation due to traffic congestion
phenomena, as well as decreasing load on board along the route as successive clients are visited. Transmission load for
exposure of the vehicle to outdoor temperatures and infiltration load at door opening are modelled, taking into account
outdoor conditions varying along the day and the year. The resulting multi-period problem is modelled and solved by
means of Constraint Programming. Test scenarios come from a real local network for frozen bread dough distributed to
supermarkets. Results show how fuel minimisation leads to the selection of different routes in comparison to the traditional
total travel distance or time objectives. Energy savings are affected by demand distribution among the clients, departure
time, number of visits per tour, seasonality and location of the delivery network
The Human-Centric SMED
Full text linkThe Human-Centric SMED (H-SMED) is an evolution of the classical methodology intro-duced by Shingo to manage the setup process, which is particularly suitable for companies where the setup involves activities with high human content, that can be hardly transformed into external operations to be performed during the machine uptime. The H-SMED integrates Industry 4.0 tools, as the MES Data Analysis, Lean Management and Ergonomics with a new attention to the centrality of workers, in order to guide the transition towards the next Industry 5.0. The H-SMED methodology is developed into four phases, devolved to: (1) understanding the changeover process; (2) identifying potential improvements; (3) moving from proposal to practice; (4) training and control, in a continuous improvement cycle. The case study of a world-wide known company in the fashion eyewear industry is proposed to validate the framework, reporting a 44% reduction of setup duration
Multi-cycles deformation modeling of hot forming tools under creep-fatigue regime
No full textHot forming processes (extrusion, die ca
sting and forging) allow the production
of a wide variety of products, both in terms
of worked material and achievable shapes.
However, critical working conditions are involved for the tools subjected to severe thermo-
mechanical loads, thus requiring an accurate design. Among the different classifications
proposed in literature for hot forming die failures, one focus on separating manufacturing
and in service failures. The latter category is additionally split, as proposed by the authors,
in static failure, damage and deformation/deflec
tion failures. Static failure appears after e
reduced number of extruded billets as a consequence of an overload or of a poor initial die
design. Damage and deflection failures are ind
eed induced by the synergic detrimental
action of creep and fatigue phenomenon. In disc
riminating the relative dominant role of
creep and fatigue in leading to the final die discard, the level of temperature and of the
applied load as well as of the dwell-time are d
ecisive. In extrusion, the latter is the time in
which a constant load acts on the die and represents the time required to extruded each
single billet function of both ram speed and billet length. Fatigue and creep can be seen as
limit cases with zero and infinite
dwell-time. A novel model is proposed for the prediction
of the deformation undergone by hot forming t
ools in the creep-fatigue regime after
multiple cycles. The model is presented as applied to extrusion dies and is based on a
modified version of a simple creep law already
implemented in all the FE codes. The model
is validated against small scale dies used
in physical experiments and then against
industrial extrusion dies
Extrusion of Magnesium Hollow Profiles for Automotive Applications
No full textThe use and adoption of magne
sium extruded profiles in
structural application is
limited because magnesium extrusion technology is at its first. Once extruded hollow
sections will be available at
a reasonable cost, a tremendous in
crease of market demand is
going to be expected due to the lowest weight of the magnesium alloys in comparison with
aluminum based ones. The press productivity re
present a key factor in this scope and the
die, due to the strong incidence of strain
and temperature in the extrudability, will play a
basic role to achieve the required stem
speed. This paper present a new approach for
designing extrusion dies specifically for
magnesium alloy ZM21 by means of FEM
simulation. The goodness of the new design has
been validated extruding an hollow profile
using an industrial press with data logging
Validazione del codice Qform per l’analisi del processo di estrusione di leghe di alluminio
No full textScopo del presente lavoro è stato qu
ello di validare un codice FEM di nuova
generazione, QForm®, per
giungere all’
implementazione di una user-routine per la
previsione dell'evoluzione micr
ostrutturale durante
processi di deform
azione plastica, in
particolare di estrusione. È stata quindi c
ondotta una campagna preliminare di simulazioni
al fine di validare i modelli di
attrito disponibili nel codice
così come le condizioni di
scambio termico e i parametri che influenzano
la discretizzazione
della maglia e il
processo. I risultati numerici sono stati co
nfrontati con indagini sperimentali di
visioplasticità riportate in letteratura [1] in te
rmini di griglie di deformazione, andamento
corsa-carico sul pistone, temperature d
el profilo estruso e della matrice. La
determinazione del mod
ello ottimale di attrito e dei suoi
fattori caratterizzanti, reso
possibile dal confronto
numerico-sperimentale,
ha permesso in seguito l’implementazione
di una routine per la previs
ione dell'evoluzione micros
trutturale nel
codice Qform
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A formula on the weight distribution of linear codes with applications to AMDS codes
Full text linkThe determination of the weight distribution of linear codes has been a fascinating problem since the very beginning of coding theory. There has been a lot of research on weight enumerators of special cases, such as self-dual codes and codes with small Singleton's defect. We propose a new set of linear relations that must be satisfied by the coefficients of the weight distribution. From these relations we are able to derive known identities (in an easier way) for interesting cases, such as extremal codes, Hermitian codes, MDS and NMDS codes. Moreover, we are able to present for the first time the weight distribution of AMDS codes. We also discuss the link between our results and the Pless equations. (c) 2021 Elsevier Inc. All rights reserved
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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