8,315 research outputs found
Compact extra dimensions in cosmologies with f(T) structure
The presence of compact extra dimensions in cosmological scenarios in the
context of f(T)-like gravities is discussed. For the case of toroidal
compactifications, the analysis is performed in an arbitrary number of extra
dimensions. Spherical topologies for the extra dimensions are then carefully
studied in six and seven spacetime dimensions, where the proper vielbein fields
responsible for the parallelization process are found.Comment: 11 pages, one figure (added). Typos corrected, manuscript improved.
Additional material is contained in section IV. Accepted for publication in
Physical Review
Characterisation of an Electrostatic Vibration Harvester
Harvesting energy from ambient vibration is proposed as an alternative to
storage based power supplies for autonomous systems. The system presented
converts the mechanical energy of a vibration into electrical energy by means
of a variable capacitor, which is polarized by an electret. A lumped element
model is used to study the generator and design a prototype. The device has
been micromachined in silicon, based on a two-wafer process. The prototype was
successfully tested, both using an external polarization source and an
electret.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/EDA-Publishing
The B -- TAU FCNC connection in SUSY Unified Theories
In the context of SUSY grand unification a link is established between the
hadronic and leptonic soft breaking sectors. Such relation is here exploited in
particular for FCNC processes in B physics. It is shown how bounds on leptonic
FCNC involving the third generation translate into constraints on FC B decays.
In the second part of the contribution we show that tests of lepton
universality in K and B decays can represent an interesting handle to obtain
relevant information on the amount of FCNC in the second and third fermion
generation.Comment: 9 pages, 4 figures. Based on talks given at: DIF06, International
Workshop on discoveries in flavour physics at e+e- colloders, Laboratori
Nazionali di Frascati (Italy), February 28- March 03, 2006; XLIst Rencontres
de Moriond, La Thuile, 5-11 March 2006; CORFU2005, Corfu Summer Institute on
EPP, Corfu, Greece, September 4-26, 200
Micromachined Polycrystalline Sige-Based Thermopiles for Micropower Generation on Human Body
This paper presents a polycrystalline silicon germanium (poly-SiGe)
thermopile specially designed for thermoelectric generators used on human body.
Both the design of the single thermocouple and the arrangement of the
thermocouple array have been described. A rim structure has been introduced in
order to increase the temperature difference across the thermocouple junctions.
The modeling of the thermocouple and the thermopile has been performed
analytically and numerically. An output power of about 1 W at an output
voltage of more than 1 V is expected from the current design of thermopiles in
a watch-size generator. The key material properties of the poly-SiGe have been
measured. The thermopile has been fabricated and tested. Experimental results
clearly demonstrate the advantage of the rim structure in increasing output
voltage. In presence of forced convection, the output voltage of a non-released
thermopile can increase from about 53 mV/K/cm2 to about 130 mV/K/cm2 after the
rim structure is formed. A larger output voltage from the thermopile is
expected upon process completion.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/EDA-Publishing
Motion-Based Generators for Industrial Applications
Scaling down of electronic systems has generated a large interest in the
research on miniature energy sources. In this paper a closer look is given to
the use of vibration based scavengers in industrial environments, where waste
energy is abundantly available as engine related vibrations or large amplitude
motions. The modeling of mechanical generators resulted in the design and
realization of two prototypes, based on electromagnetic and electrostatic
conversion of energy. Although the prototypes are not yet optimized against
size and efficiency, a power of 0.3 mW has been generated in a 5 Hz motion with
a 0.5 meter amplitude.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
ADAGSS: Automatic Dataset Generation for Semantic Segmentation
A common issue in medical deep learning research is the creation of dataset for training the neural networks. Medical data collection is also tied-up by privacy laws and even if a lot of medical data are available, often their elaboration can be time demanding. This problem can be avoided using neural networks architectures that can achieve a good predicting precision with few images (e.g. U-Net). In the case of semantic segmentation, the dataset generation is even more cumbersome since it requires the creation of segmentation masks manually. Some automatic ground-truth creation techniques may be employed like filtering, thresholding and Self Organized Maps1 (SOM). These automatic methods can be very powerful and useful, but they always have a bottle-neck phase: data validation. Due to algorithm reliability (that sometimes can fail), data needs to be validated manually before they can be included in a dataset for training. In this work, we propose a method to automatize this phase by moving manual intervention to an easier task: instead of creating masks and then validate them manually, we train a convolutional neural network to classify segmentation quality. Therefore, the validation is performed automatically. An initial manual phase is still required, but the classification task requires a smaller number of elements in the dataset that will feed a network employed for classification. After this phase, similar dataset creations will require less effort. This procedure is based on the fact that to obtain a high classification precision, fewer data are required than the data that are needed to obtain high precision in semantic segmentation. High classification score, can automatize validation procedure in dataset creation, being able to discard failure case in dataset creation. Being able to produce bigger dataset in less time can led to higher precision in semantic segmentation
On the Complexity of an Unregulated Traffic Crossing
The steady development of motor vehicle technology will enable cars of the
near future to assume an ever increasing role in the decision making and
control of the vehicle itself. In the foreseeable future, cars will have the
ability to communicate with one another in order to better coordinate their
motion. This motivates a number of interesting algorithmic problems. One of the
most challenging aspects of traffic coordination involves traffic
intersections. In this paper we consider two formulations of a simple and
fundamental geometric optimization problem involving coordinating the motion of
vehicles through an intersection.
We are given a set of vehicles in the plane, each modeled as a unit
length line segment that moves monotonically, either horizontally or
vertically, subject to a maximum speed limit. Each vehicle is described by a
start and goal position and a start time and deadline. The question is whether,
subject to the speed limit, there exists a collision-free motion plan so that
each vehicle travels from its start position to its goal position prior to its
deadline.
We present three results. We begin by showing that this problem is
NP-complete with a reduction from 3-SAT. Second, we consider a constrained
version in which cars traveling horizontally can alter their speeds while cars
traveling vertically cannot. We present a simple algorithm that solves this
problem in time. Finally, we provide a solution to the discrete
version of the problem and prove its asymptotic optimality in terms of the
maximum delay of a vehicle
Effect of PAF on polyrnorphonuclear leucocyte plasma membrane polarity: a fluorescence study
The effect of PAF on the plasma membrane polarity of polymorphonuclear leukocytes (PMNs) was investigated by measuring the steady-state fluorescence emission spectra of 2-dimethylamino(6-1auroyl) naphthalene (Laurdan), which is known to be incorporated at the hydrophobic-hydrophilic interface of the bilayer, displaying spectral sensitivity to the polarity of its surrounding. Laurdan shows a marked steady-state emission blue-shift in non-polar solvents, with respect to polar solvents. Our results demonstrate that PAF (10â7 M) induces a blue shift of the fluorescence emission spectra of Laurdan. These changes are blocked in the presence of the PAF antagonist, L-659,989. Our data indicate that the interaction between PAF and PMNs is accompanied by a decrease in polarity in the hydrophobic-hydrophilic interface of the plasma membrane
Management of water distribution systems in PDA conditions using isolation valves: case studies of real networks
Abstract
The current paper reports on a case study investigating water distribution system management in emergency conditions when it is necessary to seal off a zone with isolation valves to allow repair. In these conditions, the pressure-driven analysis (PDA) is considered to be the most efficient approach for the analysis of a water distribution network (WDN), as it takes into account whether the head in a node is adequate to ensure service. The topics of this paper are innovative because, until now, previous approaches were based on the analysis of the network behaviour in normal conditions. In emergency conditions, it is possible to measure the reliable functioning of the system by defining an objective function (OF) that helps to choose the optimal number of additional valves in order to obtain adequate system control. The OF takes into account the new network topology by excluding the zone where the broken pipe is located. The results show that the solution did not improve significantly when the number of valves reached a threshold. The procedure applied to other real case studies seems to confirm the efficiency of the methodology even if further examination of other cases in different conditions is necessary
Identification of leakages by calibration of WDS models
Open Access journalCopyright © 2013 The Authors. Published by Elsevier Ltd.12th International Conference on Computing and Control for the Water Industry, CCWI2013Leakage detection is critical for the proper management of water distribution systems (WDS). This paper proposes a leak detection approach based on a Bayesian calibration method. The methodology uses a newly formulated index, Ό, which takes into account the variation of roughness in pipes between the calibrated models with and without leaks. Case studies, which use literature networks, are presented to demonstrate how the approach can be used in identifying pipes with losses. The approach starts with a calibration method followed by the analysis of sensitivity matrices. The approach proved to be effective in finding leaks, but the results depend crucially on the number and quality of the observed data.European CommissionEuropean Social FundRegion of Calabri
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