6,432 research outputs found
Minimal generating and separating sets for O(3)-invariants of several matrices
Given an algebra of polynomial invariants of an action of the group
over the vector space , a subset of is called separating if
separates all orbits that can be separated by . A minimal
separating set is found for some algebras of matrix invariants of several
matrices over an infinite field of arbitrary characteristic different from two
in case of the orthogonal group. Namely, we consider the following cases:
1) -invariants of two matrices;
2) -invariants of skew-symmetric matrices;
3) -invariants of two skew-symmetric matrices;
4) -invariants of two symmetric matrices.
A minimal generating set is also given for the algebra of orthogonal
invariants of three symmetric matrices.Comment: 11 page
Intra-industry trade and labor costs: The smooth adjustment hypothesis
We study a situation in which, owing to the exhaustion of non-renewable energy sources, conventional motor vehicles will turn out of use. We consider two scenarios: recycling or dismantling these motor vehicles. M|G|∞ queue system is used to study the process. Through it, we conclude that if the rate of dismantling and recycling of motor vehicles is greater than the rate at which they become idle, the system will tend to get balanced. The model allows also performing a brief study about the recycling or dismantling economic interest.
Increasing availability through maintainability growth using partial Multi Criteria Decision Making (pMCDM)
In the last decades considerations about equipments' availability became an important issue, as well as its dependence on components characteristics such as reliability and maintainability. This is particularly of outstanding importance if one is dealing with high risk industrial equipments, where these factors play an important and fundamental role in risk management when safety or huge economic values are in discussion. As availability is a function of reliability, maintainability, and maintenance support activities, the main goal is to improve one or more of these factors. This paper intends to show how maintainability can influence availability and present a methodology to select the most important attributes for maintainability using a partial Multi Criteria Decision Making (pMCDM). Improvements in maintainability can be analyzed assuming it as a probability related with a restore probability density function [g(t)]
Mean-field analysis of the majority-vote model broken-ergodicity steady state
We study analytically a variant of the one-dimensional majority-vote model in
which the individual retains its opinion in case there is a tie among the
neighbors' opinions. The individuals are fixed in the sites of a ring of size
and can interact with their nearest neighbors only. The interesting feature
of this model is that it exhibits an infinity of spatially heterogeneous
absorbing configurations for whose statistical properties we
probe analytically using a mean-field framework based on the decomposition of
the -site joint probability distribution into the -contiguous-site joint
distributions, the so-called -site approximation. To describe the
broken-ergodicity steady state of the model we solve analytically the
mean-field dynamic equations for arbitrary time in the cases n=3 and 4. The
asymptotic limit reveals the mapping between the statistical
properties of the random initial configurations and those of the final
absorbing configurations. For the pair approximation () we derive that
mapping using a trick that avoids solving the full dynamics. Most remarkably,
we find that the predictions of the 4-site approximation reduce to those of the
3-site in the case of expectations involving three contiguous sites. In
addition, those expectations fit the Monte Carlo data perfectly and so we
conjecture that they are in fact the exact expectations for the one-dimensional
majority-vote model
A wireless posture monitoring system for personalized home-based rehabilitation
We live in an aging society, an issue that will be exacerbated in the coming decades, due to low birth
rates and increasing life expectancy. With the decline in physical and cognitive functions with age, it is of the
utmost importance to maintain regular physical activity, in order to preserve an individual’s mobility, motor
capabilities and coordination. Within this context, this paper describes the development of a wireless sensor
network and its application in a human motion capture system based on wearable inertial and magnetic sensors.
The goal is to enable, through continuous real-time monitoring, the creation of a personalized home-based
rehabilitation system for the elderly population and/or injured people. Within this system, the user can benefit
from an assisted mode, in which their movements can be compared to a reference motion model of the same
movements, resulting in visual feedback alerts given by the application. This motion model can be created
previously, in a ‘learning phase’, under supervision of a caregiver.Project “AAL4ALL”, co-financed by the
European Community Fund FEDER through
COMPETE – Programa Operacional Factores de
Competitividade (POFC). This work is funded by
FEDER funds through the COMPETE 2020
Programme and National Funds through FCT -
Portuguese Foundation for Science and Technology
under the projects UID/CTM/50025/2013 and
UID/EEA/04436/2013.info:eu-repo/semantics/publishedVersio
An integrated formal methods tool-chain and its application to verifying a file system model
Tool interoperability as a mean to achieve integration is among the main goals of the international Grand Challenge initiative. In the context of the Verifiable file system mini-challenge put forward by Rajeev Joshi and Gerard Holzmann, this paper focuses on the integration of different formal methods and tools in modelling and verifying an abstract file system inspired by the Intel (R) Flash File System Core. We combine high-level manual specification and proofs with current state of the art mechanical verification tools into a tool-chain which involves Alloy, VDM++ and HOL. The use of (pointfree) relation modelling provides the glue which binds these tools together.Mondrian Project funded by the Portuguese NSF under contract PTDC/EIA-CCO/108302/200
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