Context. The positron fraction in cosmic rays has recently been measured with improved accuracy up to 500 GeV, and it was found to be a steadily increasing function of energy above ~10 GeV. This ...behaviour contrasts with standard astrophysical mechanisms, in which positrons are secondary particles, produced in the interactions of primary cosmic rays during their propagation in the interstellar medium. The observed anomaly in the positron fraction triggered a lot of excitement, as it could be interpreted as an indirect signature of the presence of dark matter species in the Galaxy, the so-called weakly interacting massive particles (WIMPs). Alternatively, it could be produced by nearby sources, such as pulsars. Aims. These hypotheses are probed in light of the latest AMS-02 positron fraction measurements. As regards dark matter candidates, regions in the annihilation cross section to mass plane, which best fit the most recent data, are delineated and compared to previous measurements. The explanation of the anomaly in terms of a single nearby pulsar is also explored. Methods. The cosmic ray positron transport in the Galaxy is described using a semi-analytic two-zone model. Propagation is described with Green functions as well as with Bessel expansions. For consistency, the secondary and primary components of the positron flux are calculated together with the same propagation model. The above mentioned explanations of the positron anomaly are tested using χ2 fits. The numerical package MicrOMEGAs is used to model the positron flux generated by dark matter species. The description of the positron fraction from conventional astrophysical sources is based on the pulsar observations included in the Australia Telescope National Facility (ATNF) catalogue. Results. The masses of the favoured dark matter candidates are always larger than 500 GeV, even though the results are very sensitive to the lepton flux. The Fermi measurements point systematically to much heavier candidates than the recently released AMS-02 observations. Since the latter are more precise, they are much more constraining. A scan through the various individual annihilation channels disfavours leptons as the final state. On the contrary, the agreement is excellent for quark, gauge boson, or Higgs boson pairs, with best-fit masses in the 10 to 40 TeV range. The combination of annihilation channels that best matches the positron fraction is then determined at fixed WIMP mass. A mixture of electron and tau lepton pairs is only acceptable around 500 GeV. Adding b-quark pairs significantly improves the fit up to a mass of 40 TeV. Alternatively, a combination of the four-lepton channels provides a good fit between 0.5 and 1 TeV, with no muons in the final state. Concerning the pulsar hypothesis, the region of the distance-to-age plane that best fits the positron fraction for a single source is determined. Conclusions. The only dark matter species that fulfils the stringent gamma ray and cosmic microwave background bounds is a particle annihilating into four leptons through a light scalar or vector mediator, with a mixture of tau (75%) and electron (25%) channels, and a mass between 0.5 and 1 TeV. The positron anomaly can also be explained by a single pulsar, and a list of five pulsars from the ATNF catalogue is given. We investigate how this list could evolve when more statistics are accumulated. Those results are obtained with the cosmic ray transport parameters that best fit the B/C ratio. Uncertainties in the propagation parameters turn out to be very significant. In the WIMP annihilation cross section to mass plane for instance, they overshadow the error contours derived from the positron data.
With this paper, we propose two methods for color contrast compensation of the textual information contained in a web page using numerical optimization. The optimization process can be reduced to the ...minimization of a single objective function which aims to achieve an on-the-fly compensation inducing a small amount of change in the original colors. Mass-spring system based optimization and CMA-ES metaheuristics are compared with the problem in order to assess their efficiency for compensating the loss. Experiments conducted on real and artificial datasets, prove the methods efficiency even with a small number of evaluations. Also, the methods behaviour is bound to the amount of compensation needed.
•Tools for the study of the rider's behaviours in naturalistic real world environment.•Results gained from naturalistic riding studies to describe the riding activity.•Pro and cons of the proposed ...methodology for large scale naturalistic riding studies.•Methodology to fill knowledge gaps about PTW rider behaviour and risk factors.
Instrumented vehicles are key tools for in-depth understanding of drivers’ behaviours, thus for the design of scientifically based countermeasures to reduce fatalities and injuries. The instrumentation of Powered Two-Wheelers (PTW) has been less widely implemented that for vehicles, in part due to the technical challenges involved. The last decade has seen the development in Europe of several tools and methodologies to study motorcycle riders’ behaviours and motorcycle dynamics for a range of situations, including crash events involving falls. Thanks to these tools, a broad-ranging research programme has been conducted, from the design and tuning of real-time falls detection to the study of riding training systems, as well as studies focusing on naturalistic riding situations such as filtering and line splitting.
The methodology designed for the in-depth study of riders’ behaviours in naturalistic situations can be based upon the combination of several sources of data such as: PTW sensors, context-based video retrieval system, Global Positioning System (GPS) and verbal data on the riders’ decisions making process. The goals of this paper are: (1) to present the methodological tools developed and used by INRETS-MSIS (now Ifsttar-TS2/Simu) in the last decade for the study of riders’ behaviours in real-world environment as well as on track for situations up to falls, (2) to illustrate the kind of results that can be gained from the conducted studies, (3) to identify the advantages and limitations of the proposed methodology to conduct large scale naturalistic riding studies, and (4) to highlight how the knowledge gained from this approach will fill many of the knowledge gaps about PTW-riders’ behaviours and risk factors.
This article sets out to identify the typical risky situations experienced by novice motorcyclists in the real world just after licensing. The procedure consists of a follow-up of six novices during ...their first two months of riding with their own motorbike instrumented with cameras. The novices completed logbooks on a daily basis in order to identify the risky situations they encountered, and were given face-to-face interviews to identify the context and their shortcomings during the reported events. Data show a large number of road configurations considered as risky by the riders (248 occurrences), especially during the first two weeks. The results revealed that a lack of hazard perception skills contributed to the majority of these incidents. These situations were grouped together to form clusters of typical incident scenarios on the basis of their similarities. The most frequent scenario corresponds to a lane change in dense traffic (15% of all incidents). The discussion shows how this has enhanced our understanding of novice riders' behaviour and how the findings can improve training and licensing. Lastly, the main methodological limitations of the study and some guidelines for improving future naturalistic riding studies are presented.
Practitioner Summary:
This article aims to identify the risky situations of novice motorcyclists in real roads. Two hundred forty-eight events were recorded and 13 incident scenarios identified. Results revealed that a lack of hazard perception contributed to the majority of these events. The most frequent scenario corresponds to a lane change in dense traffic.
This paper analyses motorcycle educational content in a number of French motorcycle schools on the basis of a naturalistic study of riders’ and trainers’ behaviour. The aim is to specify the ...situations delivered in motorcycle schools and to study the rider's activity in these situations. The methodology includes ethnographic observation within the motorcycle schools and the longitudinal monitoring of 14 trainee motorcyclists during their initial training. The training situations were described by the combination of audio–visual recordings and interviews data (i.e. concomitant or interruptive verbalization, and self-confrontation data). The results permit to (1) compare the “real” and “official” durations of track and on-road training, (2) characterize the real training situations, (3) describe the preferred forms of instruction, and (4) conduct an in-depth analysis of the situations used during training in traffic. The discussion show, in first, the poverty of the training situations which are based on the repetition of the exercises in the test, and, in second, disparities between the riding situations encountered during training and the demands made by riding in natural traffic. The usefulness and the applications of this type of approach – based on the integration of the rider's point of view notably by self-confrontation interview – for understanding real riding behaviours and how such approaches could supplement vehicle-based data are discussed in a large conclusion.
Rte has been using Real-Time Simulation for the functional qualification of protections for many years. The recent commissioning of a new real-time simulator implied a migration of the existing test ...templates to the new environment and a validation of the new models. This paper explains the strategy applied for the validation, describes the issues of this migration- and validation process and gives an example of the tests applied for the qualification of a distance protection.
Purpose
This study is concerned initial motorcycle training delivered in motorcycle schools in France. Novice motorcyclists are a particularly vulnerable group of road users in Europe and in France. ...However, scientific attempts to achieve a better understanding of their behaviors have been limited. The potential value of studying initial motorcycle training, both for research purposes and with regard to public policy, is readily apparent. The aims of this paper are to describe the real educational content of training in motorcycle schools and analyze to what extent this content is related to riding after licensing.
Methods
A case study of all the training process of one trainee (38 hours) was carried out in real world. Audiovisual recordings and interview data of the rider and instructors were collected at each session. This study was supplemented by ethnographic observations of the educational content provided in three motorcycle schools throughout the instructors’ working days.
Results
The results that merged from both studies show (1) the riding skills that were fostered (i.e. control skills, and especially emergency skills, in stable and restricted environments) and undervalued (i.e. hazard perception skills, everyday skills) during initial training, and (2) the poverty of observed training settings: learners spend almost all their training time riding in the same setting that is used in the test. In addition to being repeated to excess, these settings are quite different from the real traffic.
Conclusions
These results are discussed regarding the scientific literature on motorcycle education. The conclusion presents the implications of these results for public policy in order to design a future rider training system.
Interactive evolution of ant paintings Aupetit, S.; Bordeau, V.; Monmarche, N. ...
The 2003 Congress on Evolutionary Computation, 2003. CEC '03,
2003, Letnik:
2
Conference Proceeding
We present how we use an interactive genetic algorithm to find the best parameters to build an artificial art work according to user's aesthetic taste. Ants are used to spread colors on a numerical ...painting and behave with very simple rules to follow and deposit colors. These rules and colors are considered as parameters for the evolutionary process. This work can be considered as a contribution to naturally inspired artificial art and evolutionary techniques are used to help artists in their creative process.
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