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Woolly hair nevus: case report and review of literature
Woolly hair nevus consists of a patch of curly and hypopigmented hair that is restricted to an area of the scalp. It is usually benign but it can be associated with other systemic findings. Trichoscopy and dermoscopy may be useful when analyzing this entity. The authors describe a case of woolly hair nevus in a 5-year-old boy and present a review of the literature of woolly hair nevus, including classification, histopathology, associated systemic findings, and the recent described genetic mutations
Statistics, distillation, and ordering emergence in a two-dimensional stochastic model of particles in counterflowing streams
In this paper, we proposed a stochastic model which describes two species of
particles moving in counterflow. The model generalizes the theoretical
framework describing the transport in random systems since particles can work
as mobile obstacles, whereas particles of one species move in opposite
direction to the particles of the other species, or they can work as fixed
obstacles remaining in their places during the time evolution. We conducted a
detailed study about the statistics concerning the crossing time of particles,
as well as the effects of the lateral transitions on the time required to the
system reaches a state of complete geographic separation of species. The
spatial effects of jamming were also studied by looking into the deformation of
the concentration of particles in the two-dimensional corridor. Finally, we
observed in our study the formation of patterns of lanes which reach the steady
state regardless the initial conditions used for the evolution. A similar
result is also observed in real experiments involving charged colloids motion
and simulations of pedestrian dynamics based on Langevin equations, when
periodic boundary conditions are considered (particles counterflow in a ring
symmetry). The results obtained through Monte Carlo numerical simulations and
numerical integrations are in good agreement with each other. However,
differently from previous studies, the dynamics considered in this work is not
Newton-based, and therefore, even artificial situations of self-propelled
objects should be studied in this first-principle modeling.Comment: 27 pages, 13 figure
On the semi-dynamical reflection equation: solutions and structure matrices
Explicit solutions of the non-constant semi-dynamical reflection equation are
constructed, together with suitable parametrizations of their structure
matrices. Considering the semi-dynamical reflection equation with rational
non-constant Arutyunov-Chekhov-Frolov structure matrices, and a specific
meromorphic ansatz, it is found that only two sets of the previously found
constant solutions are extendible to the non-constant case. In order to
simplify future constructions of spin-chain Hamiltonians, a parametrization
procedure is applied explicitly to all elements of the semi-dynamical
reflection equation available. Interesting expressions for `twists' and
R-matrices entering the parametrization procedure are found. In particular,
some expressions for the R-matrices seem to appear here for the first time. In
addition, a new set of consistent structure matrices for the semi-dynamical
reflection equation is obtained.Comment: typos corrected and some comments adde
Pressure and Deformation Measurement with Piezoresistive Sensors
This dissertation shows us the processes to develop a sensor capable of measuring deformations
of surfaces. The work englobes the processes of production and assemblage of the transducers,
the electronics boards to read the signals from the transducers and, finally, the development
of algorithms used to transform the signal of the sensor in readable information either for
humans and other computers.
The work starts with the study of the production and assemblage methods of the transducers.
In this part, we used the screen printing technique to print the different layers of the
transducer.
After obtaining the printed transducer, we tested it, measuring only the main characteristics,
as the variation of resistance with pressure. This gave us important information to proceed with
the dimensioning of the measurement chain.
The second part of this project, was focused in the design of the measurement chain. For this
work, we projected a device that can adapt automatically to different values of sensors’
resistance.
Because the transducers tested in this project have a hysteretic behavior, a mathematical
model used to model the magnetic hysteresis was adapted to be used with piezoresistive
sensors.
This work meets the initial goal which was building a complete data acquisition system for a
printed piezoresistive sensor. The proposed mathematical algorithm to model the resistance of
piezoresistive sensors opens doors for future projects.Esta dissertação vem mostrar o processo completo para o desenvolvimento de um sensor capaz
de medir deformações de superfÃcies. O trabalho passa assim pelos processos de produção e
montagem dos transdutores, pelos circuitos eletrónicos desenhados para fazer as leituras do
transdutor e finalmente pelos algoritmos utilizados para transformar o sinal do sensor numa
informação que pode ser interpretada por humanos ou por outras máquinas.
Desta forma, o trabalho inicia-se por um estudo dos métodos de produção e montagem dos
transdutores. No final optou-se pela técnica de screen printing para produzir os transdutores e
os elétrodos. Quanto ao método de montagem, optou-se por fazer uma sobreposição das
camadas impressas.
Após termos o transdutor impresso conseguimos testá-lo e assim obter informações como a
variação da resistência. Estes são parâmetros muito importantes para o dimensionamento da
cadeia de medida, que foi o segundo passo deste trabalho. Foi desenhada uma cadeia de medida
capaz de fazer a leitura de diferentes sensores ao mesmo tempo. Este circuito é também capaz
de se adaptar a diferentes sensores automaticamente.
Como os sensores testados neste projeto apresentaram histerese, para contornar esta situação,
um modelo de aproximação utilizado com materiais magnéticos foi adaptado para os sensores
piezoresistivos.
O trabalho cumpre o objetivo proposto no inÃcio deste projeto que era construir um sistema
completo de aquisição de dados de um sensor piezoresistivo impresso. No final foi introduzido
a adaptação do algoritmo que abre portas para futuros trabalhos
Nonequilibrium scaling explorations on a 2D Z(5)-symmetric model
We have investigated the dynamic critical behavior of the two-dimensional
Z(5)-symmetric spin model by using short-time Monte Carlo (MC) simulations. We
have obtained estimates of some critical points in its rich phase diagram and
included, among the usual critical lines the study of first-order (weak)
transition by looking into the order-disorder phase transition. Besides, we
also investigated the soft-disorder phase transition by considering empiric
methods. A study of the behavior of along the self-dual critical
line has been performed and special attention has been devoted to the critical
bifurcation point, or FZ (Fateev-Zamolodchikov) point. Firstly, by using a
refinement method and taking into account simulations out-of-equilibrium, we
were able to localize parameters of this point. In a second part of our study,
we turned our attention to the behavior of the model at the early stage of its
time evolution in order to find the dynamic critical exponent z as well as the
static critical exponents and of the FZ-point on square
lattices. The values of the static critical exponents and parameters are in
good agreement with the exact results, and the dynamic critical exponent
very close of the 4-state Potts model ().Comment: 11 pages, 7 figure
Fiber orientation assessment in complex shaped parts reinforced with carbon fiber using infrared thermography
The use of composite materials is growing more and more every day in several applications. The arrangement or orientation of the fibers relative to one another have a significant influence on the strength and other properties of fiber reinforced composites. Thus, evaluation techniques are needed for measuring material fiber orientation. In this work infrared thermography is employed to assess the material’s fiber orientation. More specifically a pulsed infrared diode laser heating spot technique combined with a 3D model of the part is used in order to assess fiber orientation on the surface of carbon fiber-reinforced polymer complex shaped parts made of carbon/PEEK (Polyether ether ketone) randomly-oriented strands
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