The momentum for network separation: a guide for regulators

NGAs (Next Generation Access Networks) are a challenge to regulators and operators insofar as they require large investments, there is significant uncertainty about the ability to recover costs, and the choice of the appropriate regulatory regime is far from consensual. Regulatory authorities might want to seize the moment and reconsider the mandatory vertical separation of telecommunication firms, without jeopardizing incentives to innovation, investment and welfare. We provide a provocative but simple test for the adequacy of network separation as a regulatory remedy. We propose a decision tree procedure with four steps in order to assess whether network separation is an adequate regulatory response: [1] “Is there significant market power in the market for the provision of access services under NGAs?”; [2] “Are there few vertical complementarities between services along the supply chain?”; [3] “Is functional separation a better regulatory tool than any other alternative?”; and [4] “Is structural separation superior to functional separation?”. A positive answer to the first three questions implies that the regulator should consider functional network separation, whilst the fourth is needed for the structural alternative.Telecommunications networks, Functional separation, Structural separation

Review of real brain-controlled wheelchairs

This paper presents a review of the state of the art regarding wheelchairs driven by a brain-computer interface (BCI). Using a brain-controlled wheelchair (BCW), disabled users could handle a wheelchair through their brain activity, granting autonomy to move through an experimental environment. A classification is established, based on the characteristics of the BCW, such as the type of electroencephalographic (EEG) signal used, the navigation system employed by the wheelchair, the task for the participants, or the metrics used to evaluate the performance. Furthermore, these factors are compared according to the type of signal used, in order to clarify the differences among them. Finally, the trend of current research in this field is discussed, as well as the challenges that should be solved in the future

Brain switch mode: an alternative to drive a brain-controlled wheelchair

To date, different control paradigms of low level navigation have been tested for brain-controlled wheelchairs, mainly divided into continuous or discrete control [1]. However, these paradigms have certain drawbacks such as the need to keep the mental tasks active for a long time, as in continuous mode, or the impossibility to freely choose any distance of the movement or the turn, as in the discrete mode. An alternative paradigm to solve these problems could be the use of the brain switch mode [2], which would allow a more flexible control of the distance, requiring a lower workload for the user.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Proposals of Control Paradigms Applied to a Brain-Controlled Wheelchair

Proposals of Control Paradigms Applied to a Brain-Controlled Wheelchair, Ron-Angevin R., Velasco-Álvarez F., Fernández Rodriguez A., Proceeding og the BITs 4th Annual World Congress of Smart Material 2018, Osaka (Japan), 6-8 March 2018Several of the neurological diseases that human beings can result in severe disabilities. In some cases, people who suffer from such deficiencies lose any chance of communication with their environment, being the only possible alternative to give the brain a new channel not based on muscular activity, allowing these people to send messages and commands to the external world. The systems that allows the latter is what is known as Brain-Computer Interfaces (BCI). Their common feature is to process the brain’s electrical activity for extracting information that can be used to command an external device, as for example, a wheelchair to provide them some mobility. One of the most important limitations of these brain controlled wheelchair is to guarantee that a person can, through his mental activity, safely control the variety of navigation commands that provide control of the wheelchair: advance, turn, move back, and stop. The vast majority of the mobile robot navigation applications that are controlled via a BCI demand that the user performs as many different mental tasks as there are different control commands, worsening the classification accuracy. In order to enable an effective and autonomous wheelchair navigation with a BCI system without worsening user performance, the Brain–Computer Interface (BCI) group of the University of Málaga (UMA-BCI) proposed and later developed a new paradigm based on the discrimination of only two classes (one active mental task versus any other mental activity), which enabled the selection of four commands: move forwards, turn right, move backward and turn left. The final aim of this contribution is to show how to control a robotic wheelchair through the use of only two mental tasks. The mapping of these two mental tasks into several navigation commands allows the Brain-Controlled Wheelchair to be moved and turned in order to achieve effective navigation.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Dynamics of a vibrating tip near or in intermittent contact with a surface

We discuss the stability of the tip motion in dynamic atomic force microscopy. A nonlinear dynamics analysis shows that the tip's phase space is divided in two basins of attraction. A phase space diagram dominated by either basin of attraction implies a stable motion while a substantial contribution from both basins is associated with instabilities. Because the dominance of a given basin of attraction depends on the tip-surface interaction potential and separation, stable and unstable motions are intrinsic features of an oscillating tip near or in intermittent contact with a surface.This work has been supported by the Dirección General de Investigación Científica y Técnica (PB98-0471) and the European Union (BICEPS, BIO4-CT-2112). A.S.P. acknowledges financial support from the Comunidad de Madrid.Peer reviewe

Diameter versus girth: which variable provides the best estimate of the cross-sectional area?

Aim of study: Cross-sectional area is one of the most important forest inventory variable since it is highly correlated with growth and yield at both tree and stand levels. In this research, we evaluated the bias, precision and accuracy of three measurements such as cross-sectional area: the girth, the arithmetic mean diameter, and the geometric mean diameter normally used to estimate the cross-sectional area in practical forestry.Area of study: Measurements were taken in a poplar plantation (Populus x euramericana (Dode) Guinier cv. Luisa Avanzo) located in Huesca, Spain.Material and Methods: A total of 5,408 cross-sectional areas from 48 poplar trees were measured with and image based software. To test the differences between real and estimated cross-sectional area based on the three measurements of study, a multilevel mixed-effect model was used.Main Results: All three measurements overestimated the cross-sectional area by (0.47%-2.37%) and were found to be biased. Estimations based on arithmetic or geometric mean diameter of the maximum and minimum axes were more accurate than those using tree girth.Research highlights: There was a strong correlation between estimation errors and departures from a circumference in the cross section i.e. estimation errors were larger in elliptical cross-sections than in those closer to a circumference. In order to avoid overestimation of growth and yield derived from cross-sectional area estimates, we recommend using the geometric mean diameter trying to measure the largest and the smallest diameters of the section, especially on trees that are clearly elliptical.Keywords: diameter; circumference; cross-sectional area; poplar plantations

Positron lifetime spectroscopy applied to pure sulphur and selenium

High purity crystalline orthorhombic Sulphur and hexagonal Selenium have been investigated using Positron Lifetime Spectroscopy technique. Annealed for 3 h at 120 °C Selenium lifetime (308(1) ps) has been compared with previous Positron Lifetime Spectroscopy knowledge in order to validate the measurements and the analysis procedure, and also compared with theoretical calculations available in literature, including different methods and parametrizations, resulting on the best match of LMTO-ASA method with GGA parametrization. Annealed for 3 h at 80 °C Sulphur samples were studied by the same means providing a single lifetime component with value 300(1) ps that has been assigned to the positron annihilation in the bulk that is not present in the current literature.This research was supported by the Universidad Carlos III de Madrid and by the Comunidad de Madrid (Spain)-multiannual agreement with UC3M ('Excelencia para el Profesorado Universitario'-EPUC3M14)-Fifth regional research plan 2016-2020, and by Agencia Estatal de Investigación (PID2019-105325RB-C33 / AEI /10.13039/501100011033)

Electronic and structural distortions in graphene induced by carbon vacancies and boron doping

We present an ab initio study on the structural and electronic distortions of modified graphene by creation of vacancies, inclusion of boron atoms, and the coexistence of both, by means of thermodynamics and band structure calculations. In the case of coexistence of boron atoms and vacancy, the modified graphene presents spin polarization only when B atoms locate far from vacancy. Thus, when a boron atom fills single- and di-vacancies, it suppresses the spin polarization of the charge density. In particular when B atoms fill a di-vacancy a new type of rearrangement occurs, where a stable BC4 unit is formed inducing important out of plane distortions to graphene. All these findings suggest that new chemical modifications to graphene and new type of vacancies can be used for interesting applications such as sensor and chemical labeling.Comment: 22 pages, 9 figures and 3 table