2,857 research outputs found
Dynamics and Topology of Flexible Chains: Knots in Steady Shear Flows
We use numerical simulations of a bead-spring model chain to investigate the
evolution of the conformation of long and flexible elastic fibers in a steady
shear flow. In particular, for rather open initial configurations, and by
varying a dimensionless elastic parameter, we identify two distinct
conformational modes with different final size, shape, and orientation. Through
further analysis we identify slipknots in the chain. Finally, we provide
examples of initial configurations of an "open" trefoil knot that the flow
unknots and then knots again, sometimes repeating several times. These changes
in topology should be reflected in changes in bulk rheological and/or transport
properties.Comment: 22 pages, 12 figure
Extracting physical chemistry from mechanics: a new approach to investigate DNA interactions with drugs and proteins in single molecule experiments
In this review we focus on the idea of establishing connections between the
mechanical properties of DNAligand complexes and the physical chemistry of
DNA-ligand interactions. This type of connection is interesting because it
opens the possibility of performing a robust characterization of such
interactions by using only one experimental technique: single molecule
stretching. Furthermore, it also opens new possibilities in comparing results
obtained by very different approaches, in special when comparing single
molecule techniques to ensemble-averaging techniques. We start the manuscript
reviewing important concepts of the DNA mechanics, from the basic mechanical
properties to the Worm-Like Chain model. Next we review the basic concepts of
the physical chemistry of DNA-ligand interactions, revisiting the most
important models used to analyze the binding data and discussing their binding
isotherms. Then, we discuss the basic features of the single molecule
techniques most used to stretch the DNA-ligand complexes and to obtain force x
extension data, from which the mechanical properties of the complexes can be
determined. We also discuss the characteristics of the main types of
interactions that can occur between DNA and ligands, from covalent binding to
simple electrostatic driven interactions. Finally, we present a historical
survey on the attempts to connect mechanics to physical chemistry for
DNA-ligand systems, emphasizing a recently developed fitting approach useful to
connect the persistence length of the DNA-ligand complexes to the
physicochemical properties of the interaction. Such approach in principle can
be used for any type of ligand, from drugs to proteins, even if multiple
binding modes are present
An Efficient Pipeline to Obtain 3D Model for HBIM and Structural Analysis Purposes from 3D Point Clouds
The aim of this work is to identify an efficient pipeline in order to build HBIM (heritage building information modelling) and create digital models to be used in structural analysis. To build accurate 3D models it is first necessary to perform a geomatics survey. This means performing a survey with active or passive sensors and, subsequently, accomplishing adequate post-processing of the data. In this way, it is possible to obtain a 3D point cloud of the structure under investigation. The next step, known as "scan-to-BIM (building information modelling)", has led to the creation of an appropriate methodology that involved the use of Rhinoceros software and a few tools developed within this environment. Once the 3D model is obtained, the last step is the implementation of the structure in FEM (finite element method) and/or in HBIM software. In this paper, two case studies involving structures belonging to the cultural heritage (CH) environment are analysed: a historical church and a masonry bridge. In particular, for both case studies, the different phases were described involving the construction of the point cloud and, subsequently, the construction of a 3D model. This model is suitable both for structural analysis and for the parameterization of rheological and geometric information of each single element of the structure
Developing a parametric system for pointe shoe customization
A Pointe Shoe is worn by ballet dancers while performing “en pointe”. This fundamental ballet technique, which is performed by rising to the tips of the toes, enables dancers to create the illusion of incredible lightness and sylph-like appearance. However, pointe work causes pain, blisters, calluses, and disfigurement of the feet. Dancers, pointe shoe fitters, and podiatrists agree that finding Pointe Shoes which fit correctly and adjust throughout your career could help to avoid feet injuries. The different parts of the shoe require different performance, depending on the different parts of the foot. Each dancer has particular feet, with variations of toe length and shape, arch flexibility, and mechanical strength. Instead of having the dancer’s feet adjusted on the point shoes, the idea is to have the shoes, uniquely ‘adapt’ according to the morphology of the feet. The foot is not just a passive weight-bearer, it must assume positions and execute movements beyond its normal limits. Therefore, the parameters to take in account are classified in anatomical, mechanical, assembly and material.
From the study, it is deduced that the above parameters may be the key to define a proposal for a solution to the design of Pointe shoe.Las puntas se usan durante la actuación "en pointe". Esta fundamental técnica de ballet, que se realiza levantándose a los dedos del pie, permite a los bailarines, crear la ilusión de una ligereza increíble y el aspecto de sílfide. Sin embargo, bailando en puntas causa dolor, ampollas, callos, y desfiguración de pies, comúnmente conocida entre los bailarines. Estas heridas pueden evitarse si los pies están mejor soportados. Bailarines, zapateros de punta, y podólogos están de acuerdo en que tener las zapatillas de punta que se adaptan y ajustan correctamente, a lo largo de carrera podrían ayudar a evitar las heridas en los pies. Cada bailarín tiene los pies únicos, con las variaciones de longitud de los dedos del pie y de su forma, la flexibilidad del arco, y la resistencia mecánica. En lugar de ajustar los pies del bailarín en las zapatillas de puntas, la idea es diseñar zapatos, que pueden "adaptarse" en forma única, según la morfología de los pies y también de la fuerza de los bailarines. El pie no es solo un portador pasivo de peso, debe asumir posiciones y ejecutar movimientos más allá de sus límites normales. Por tanto, los parámetros a tener en cuenta se clasifican en anatómicos, mecánicos, de montaje y material. Del estudio se deduce que los parámetros anteriores pueden ser la clave para definir una propuesta de solución al diseño de Pointe.Postprint (published version
Origami surfaces for kinetic architecture
This thesis departs from the conviction that spaces that can change their
formal configuration through movement may endow buildings of bigger
versatility. Through kinetic architecture may be possible to generate adaptable
buildings able to respond to different functional solicitations in terms of the
used spaces.
The research proposes the exploration of rigidly folding origami surfaces as
the means to materialize reconfigurable spaces through motion. This specific
kind of tessellated surfaces are the result of the transformation of a flat
element, without any special structural skill, into a self-supporting element
through folds in the material, which gives them the aptitude to undertake
various configurations depending on the crease pattern design and welldefined
rules for folding according to rigid kinematics.
The research follows a methodology based on multidisciplinary, practical
experiments supported on digital tools for formal exploration and simulation.
The developed experiments allow to propose a workflow, from concept to
fabrication, of kinetic structures made through rigidly folding regular origami
surfaces. The workflow is a step-by-step process that allows to take a logical
path which passes through the main involved areas, namely origami geometry
and parameterization, materials and digital fabrication and mechanisms and
control.
The investigation demonstrates that rigidly folding origami surfaces can be
used as dynamic structures to materialize reconfigurable spaces at different
scales and also that the use of pantographic systems as a mechanism
associated to specific parts of the origami surface permits the achievement of
synchronized motion and possibility of locking the structure at specific stages
of the folding.A presente tese parte da convicção de que os espaços que são capazes de
mudar a sua configuração formal através de movimento podem dotar os
edifícios de maior versatilidade. Através da arquitectura cinética pode ser
possível a geração de edifícios adaptáveis, capazes de responder a
diferentes solicitações funcionais, em termos do espaço utilizado.
Esta investigação propõe a exploração de superfícies de origami, dobráveis
de forma rígida, como meio de materialização de espaços reconfiguráveis
através de movimento. Este tipo de superfícies tesseladas são o resultado da
transformação de um elemento plano, sem capacidade estrutural que, através
de dobras no material, ganha propriedades de auto-suporte. Dependendo do
padrão de dobragem e segundo regras de dobragem bem definidas de acordo
com uma cinemática rígida, a superfície ganha a capacidade de assumir
diferentes configurações.
A investigação segue uma metodologia baseada em experiências práticas e
multidisciplinares apoiada em ferramentas digitais para a exploração formal e
simulação. Através das experiências desenvolvidas é proposto um processo
de trabalho, desde a conceptualização à construção, de estruturas cinéticas
baseadas em superfícies dobráveis de origami rígido de padrão regular. O
processo de trabalho proposto corresponde a um procedimento passo-apasso
que permite seguir um percurso lógico que atravessa as principais
áreas envolvidas, nomeadamente geometria do origami e parametrização,
materiais e fabricação digital e ainda mecanismos e controle.
A dissertação demonstra que as superfícies de origami dobradas de forma
rígida podem ser utilizadas como estruturas dinâmicas para materializar
espaços reconfiguráveis a diferentes escalas. Demonstra ainda que a
utilização de sistemas pantográficos como mecanismos associados a partes
específicas da superfície permite atingir um movimento sincronizado e a
possibilidade de bloquear o movimento em estados específicos da dobragem
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Geometry-based structural analysis and design via discrete stress functions
This PhD thesis proposes a direct and unified method for generating global static equilibrium
for 2D and 3D reciprocal form and force diagrams based on reciprocal discrete stress
functions. This research combines and reinterprets knowledge from Maxwell’s 19th century
graphic statics, projective geometry and rigidity theory to provide an interactive design and
analysis framework through which information about designed structural performance can be
geometrically encoded in the form of the characteristics of the stress function. This method
results in novel, intuitive design and analysis freedoms.
In contrast to contemporary computational frameworks, this method is direct and analytical.
In this way, there is no need for iteration, the designer operates by default within
the equilibrium space and the mathematically elegant nature of this framework results in its
wide applicability as well as in added educational value. Moreover, it provides the designers
with the agility to start from any one of the four interlinked reciprocal objects (form diagram,
force diagram, corresponding stress functions).
This method has the potential to be applied in a wide range of case studies and fields.
Specifically, it leads to the design, analysis and load-path optimisation of tension-and compression
2D and 3D trusses, tensegrities, the exoskeletons of towers, and in conjunction
with force density, to tension-and-compression grid-shells, shells and vaults. Moreover, the
abstract nature of this method leads to wide cross-disciplinary applicability, such as 2D and
3D discrete stress fields in structural concrete and to a geometrical interpretation of yield line
theory
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Geometrie
The program covered a wide range of new developments in geometry. To name some of them, we mention the topics “Metric space geometry in the style of Alexandrov/Gromov”, “Polyhedra with prescribed metric”, “Willmore surfaces”, “Constant mean curvature surfaces in three-dimensional Lie groups”. The official program consisted of 21 lectures and included four lectures by V. Schroeder (Zürich) and S. Buyalo (Sankt-Petersburg) on “Asymptotic geometry of Gromov hyperbolic spaces”
Advances in Human-Protein Interaction - Interactive and Immersive Molecular Simulations
International audienc
Intelligent Machining Systems
Machining is one of the most widespread manufacturing processes and plays a critical role
in industries. As a matter of fact, machine tools are often called mother machines as they
are used to produce other machines and production plants. The continuous development
of innovative materials and the increasing competitiveness are two of the challenges that
nowadays manufacturing industries have to cope with. The increasing attention to environmental
issues and the rising costs of raw materials drive the development of machining
systems able to continuously monitor the ongoing process, identify eventual arising problems
and adopt appropriate countermeasures to resolve or prevent these issues, leading
to an overall optimization of the process. This work presents the development of intelligent
machining systems based on in-process monitoring which can be implemented on
production machines in order to enhance their performances. Therefore, some cases of
monitoring systems developed in different fields, and for different applications, are presented
in order to demonstrate the functions which can be enabled by the adoption of
these systems. Design and realization of an advanced experimental machining testbed is
presented in order to give an example of a machine tool retrofit aimed to enable advanced
monitoring and control solutions. Finally, the implementation of a data-driven simulation
of the machining process is presented. The modelling and simulation phases are presented
and discussed. So, the model is applied to data collected during an experimental campaign
in order to tune it. The opportunities enabled by integrating monitoring systems
with simulation are presented with preliminary studies on the development of two virtual
sensors for the material conformance and cutting parameter estimation during machining
processes
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