156,284 research outputs found
Validation by Measurements of a IC Modeling Approach for SiP Applications
The growing importance of signal integrity (SI) analysis in integrated circuits (ICs), revealed by modern systemin-package methods, is demanding for new models for the IC sub-systems which are both accurate, efficient and extractable by simple measurement procedures. This paper presents the contribution for the establishment of an integrated IC modeling approach whose performance is assessed by direct comparison with the signals measured in laboratory of two distinct memory IC devices. Based on the identification of the main blocks of a typical IC device, the modeling approach consists of a network of system-level sub-models, some of which with already demonstrated accuracy, which simulated the IC interfacing behavior. Emphasis is given to the procedures that were developed to validate by means of laboratory measurements (and not by comparison with circuit-level simulations) the model performance, which is a novel and important aspect that should be considered in the design of IC models that are useful for SI analysi
Probabilistic Human Mobility Model in Indoor Environment
Understanding human mobility is important for the development of intelligent
mobile service robots as it can provide prior knowledge and predictions of
human distribution for robot-assisted activities. In this paper, we propose a
probabilistic method to model human motion behaviors which is determined by
both internal and external factors in an indoor environment. While the internal
factors are represented by the individual preferences, aims and interests, the
external factors are indicated by the stimulation of the environment. We model
the randomness of human macro-level movement, e.g., the probability of visiting
a specific place and staying time, under the Bayesian framework, considering
the influence of both internal and external variables. We use two case studies
in a shopping mall and in a college student dorm building to show the
effectiveness of our proposed probabilistic human mobility model. Real
surveillance camera data are used to validate the proposed model together with
survey data in the case study of student dorm.Comment: 8 pages, 9 figures, International Joint Conference on Neural Networks
(IJCNN) 201
Evolution of the social network of scientific collaborations
The co-authorship network of scientists represents a prototype of complex
evolving networks.
By mapping the electronic database containing all relevant journals in
mathematics and neuro-science for an eight-year period (1991-98), we infer the
dynamic and the structural mechanisms that govern the evolution and topology of
this complex system.
First, empirical measurements allow us to uncover the topological measures
that characterize the network at a given moment, as well as the time evolution
of these quantities.
The results indicate that the network is scale-free, and that the network
evolution is governed by preferential attachment, affecting both internal and
external links.
However, in contrast with most model predictions the average degree increases
in time, and the node separation decreases.
Second, we propose a simple model that captures the network's time evolution.
Third, numerical simulations are used to uncover the behavior of quantities
that could not be predicted analytically.Comment: 14 pages, 15 figure
Studying synthesis confinement effects on the internal structure of nanogels in computer simulations
We study the effects of droplet finite size on the structure of nanogel
particles synthesized by random crosslinking of molecular polymers diluted in
nanoemulsions. For this, we use a bead-spring computer model of polymer-like
structures that mimics the confined random crosslinking process corresponding
to irradiation- or electrochemically-induced crosslinking methods. Our results
indicate that random crosslinking under strong confinement can lead to unusual
nanogel internal structures, with a central region less dense than the external
one, whereas under moderate confinement the resulting structure has a denser
central region. We analyze the topology of the polymer networks forming nanogel
particles with both types of architectures, their overall structural
parameters, their response to the quality of the solvent and compare the cases
of non-ionic and ionic systems
Mathematical modeling of local perfusion in large distensible microvascular networks
Microvessels -blood vessels with diameter less than 200 microns- form large,
intricate networks organized into arterioles, capillaries and venules. In these
networks, the distribution of flow and pressure drop is a highly interlaced
function of single vessel resistances and mutual vessel interactions. In this
paper we propose a mathematical and computational model to study the behavior
of microcirculatory networks subjected to different conditions. The network
geometry is composed of a graph of connected straight cylinders, each one
representing a vessel. The blood flow and pressure drop across the single
vessel, further split into smaller elements, are related through a generalized
Ohm's law featuring a conductivity parameter, function of the vessel cross
section area and geometry, which undergo deformations under pressure loads. The
membrane theory is used to describe the deformation of vessel lumina, tailored
to the structure of thick-walled arterioles and thin-walled venules. In
addition, since venules can possibly experience negative transmural pressures,
a buckling model is also included to represent vessel collapse. The complete
model including arterioles, capillaries and venules represents a nonlinear
system of PDEs, which is approached numerically by finite element
discretization and linearization techniques. We use the model to simulate flow
in the microcirculation of the human eye retina, a terminal system with a
single inlet and outlet. After a phase of validation against experimental
measurements, we simulate the network response to different interstitial
pressure values. Such a study is carried out both for global and localized
variations of the interstitial pressure. In both cases, significant
redistributions of the blood flow in the network arise, highlighting the
importance of considering the single vessel behavior along with its position
and connectivity in the network
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