1,721,079 research outputs found
Accesso e Instradamento in Reti Radio Cognitive
No full textThe always-increasing need of more flexible link for broadband connectivity in mobile
conditions has led to a high-level radio technology evolution.
Radio environment has to be shared and new strategies for improving the usage efficiency need to
be developed in order to allow coexistence between different radio systems.
In the past, the spectrum has been assigned to particular services in a fixed way, for example for
radio mobile or digital television broadcasting systems. This unyielding use of spectrum resources
has led to a really low efficiency; in fact, FCC has demonstrated that radio frequencies are used for
only the 30% of their possibilities.
Basing on these aspects the idea of new technologies allowing coexistence between different radio
systems using the same frequency band has risen up; the Cognitive Radio is one of the most
important among them. A cognitive radio is a smart device, which independently or thanks to
cooperation with others nodes (the so-called secondary users), is able to exploit unused or underused
spectrum fractions; these portions are generally assigned to primary systems, but can be used
by cognitive systems in order to provide services which traditionally were not allowed in that
bands. On the other hand, secondary nodes need to protect primary users from interference coming
from their transmissions, while primary receivers do not become aware of cognitive nodes presence.
A secondary node can adopt different strategies; first of sensing algorithm, together with
geolocation database approach, allows cognitive devices to detect available spectrum portions for
secondary transmissions; at the same time it is really important to forecast the effects of these
transmissions on the primary receivers signal quality. The target of this work was the design of an
interference prevision model, which can allow to establish the interference produced by a secondary
system against a primary DVB-T system.
The last one has many different distinctive features: first of all, the DVB-T receviers are passive
and it is not possible to establish their position in the scenario. Moreover the primary traffic model
is not link ‘burst model’, therefore there are not any temporal intervals in which the spectrum can
be considered as free.
Many different steps have been developed in order to reach the final model: in the first phase the
effect of a single secondary transmission on a primary system with only one transmitter and many
different receivers has been evaluated and a closed-form analytical expression for primary outage
probability has been provided. Then the scenario has been extended to a secondary network instead
of a single cognitive node and we obtained a closed-form analytical expression for the signal-tointerference
ratio CDF; it was not possible to determined a closed form expression for the outage
probability in this case, because of the too high complexity of the mathematical approach. For this
reason the scenario has been modeled thanks to MatLAB simulations, which allowed also to simulate more complex scenarios with more than one primary transmitter and a secondary network.
We also introduced a simple routing rule, in order to demonstrate the effect of our prevision model
on the path selection strategy.
Finally a real test-bed and the experimentation on WiFi-based system, operating in UHF band has
been described. This activity was conducted in collaboration with Politecnico di Torino and CSP
and has marked some advantages coming from the usage of this system for providing broadband
connectivity in Digital Divided zones, instead of using traditional 5 GHz, HyperLAN strategies
Mutual Interference Evaluation in Cognitive Radio Networks with Log-Normal Shadowing
No full textThe always increasing need of wireless access networks
has risen up a question about the spectrum usage efficiency. It
has been demonstrated that the traditional assignment schemes,
do not work well in terms of spectral efficiency. The cognitive
radio paradigm could solve the problem by allocating licensed
spectrum portions to unlicensed users (secondary users) under
particular restrictions. In this case, the mutual interference
between primary and secondary users represents a critical
aspect, which needs to be investigated. This paper describes a
simple but effective model for evaluating
the mutual
interference problem, in a complex scenario with more than one
primary transmitter, a multi-hop secondary network and a
channel model affected by lognormal shadowing. Moreover this
work presents how these information could be used in order to
define a reliable routing metric for the secondary multi-hop
network
Multidimensional Routing: a New Frontiere for Wireless Global Optimization
No full textIn this paper we describe and compare many existing routing metrics, realized to improve the performances of wireless ad-hoc and mesh networks. Usually these metrics are defined by a linear combination of network parameters, coming from different ISO-OSI layers; but this way to proceed could not guarantee the best performances. So we propose a new approach, named multidimensional routing that defines a new metric, combining these parameters in a non-linear way
Benessere e resilienza in donne con osteoporosi e fratture vertebrali: l’attività fisica può contribuire? Risultati dello studio Osteo-AFA 2014
No full textIntroduzione: la resilienza si riferisce a come le persone, indipendentemente dalla loro età, affrontano le difficoltà della vita, tra queste l’esperienza di malattia. Lo studio della resilienza nelle persone affette da patologie croniche sta attirando sempre più interesse, sia in ambito politico che clinico, anche per i potenziali effetti benessere, la qualità della vita e sul welfare (Ghanei,2016). Le malattie cronico degenerative costituiscono una grande fonte di stress per il nostro sistema psico-fisiologico al quale è necessario rispondere attraverso un cambiamento alla nuova condizione che si impone. L’osteoporosi rientra in queste ultime, con un esordio sintomatico con frattura. L’Italia è il secondo paese in Europa per prevalenza di osteoporosi: 4 milioni di persone affette; 3,2 milioni di donne; 0,8 milioni di uomini (IOF,2018). Le fratture ossee sono la principale conseguenze dell'osteoporosi, dal punto di vista clinico, sociale ed economico e possono rappresentare un serio ostacolo all'invecchiamento in buona salute compromettendo l'indipendenza, la qualità della vita e la sua durata. Questa condizione contribuisce a: diminuire mobilità e prestazioni fisiche; aumentare isolamento sociale, mancanza di fiducia in sé, depressione e morte prematura 2,7 volte superiore a quella delle persone senza fratture (Adachi,2001;Cauley,2000;Kado,2007). I pazienti con una frattura vertebrale dovrebbero essere sottoposti ad una terapia anti-frattura che includa l’attività fisica (Kendler,2016). A tal proposito sono sempre più numerose le evidenze scientifiche che sostengono come l’AF possa essere un mezzo per aumentare la resilienza. L'AF fisico regolare induce benefici psico-fisiologici positivi, contrasta le potenziali conseguenze di eventi stressanti e previene molte malattie croniche; rinforza l’autostima e l’autoefficacia, elementi fondamentali nella costruzione della resilienza (Deuster,2013). Lo studio sperimentale, controllato non randomizzato, OSTEO-AFA/2014, è stato condotto su donne con osteoporosi post-menopausale e fratture vertebrali, al fine di valutare i benefici in termini di qualità della vita, performance motoria e paura di cadere, di un programma di AF adattata (AFA) di media intensità della durata di 6 mesi. L’importanza dell’effetto del programma in studio è stato valutata tramite il calcolo dell’effect size (ES) proposta da Cohen.
Materiali e Metodi: le donne assegnate al gruppo sperimentale (GS) hanno eseguito, 2 volte alla settimana per 60 minuti, un programma di esercizio specificatamente strutturato somministrato da laureati in scienze motorie, che includeva esercizi posturali e di rinforzo muscolare. Il gruppo controllo (GC) riceveva l’indicazione generica di fare AF. Alla baseline e al follow-up sono stati valutati i seguenti esiti: qualità della vita (ECOS-16), paura di cadere (FES-1), capacità funzionale (6MWT), equilibrio (scala Tinetti), flessibilità della colonna (Chair Sit&Reach). È stato analizzato lo score della componente mentale (MCS) contenuta nell’ECOS-16 per indagare nello specifico i benefici del protocollo AFA in termini di resilienza.
Risultati: sono state incluse nelle analisi 40 donne (22GS;18GC). Complessivamente nel GS si è sempre osservato un miglioramento in tutti gli esiti in studio, mentre sono rimasti invariati nel CG. Il protocollo AFA in studio ha avuto un grande effetto nel ridurre la paura di cadere (FES-I, ES=1,007), migliorare l’equilibrio (scala Tinetti, ES=0,871), la performance fisica (6-MWT, ES=1,390) e la qualità della vita (ECOS-16, ES=1,204) in particolare nella sua componente mentale.
Conclusione: lo studio ha dimostrato che il programma AFA è in grado di migliorare in maniera statisticamente significativa la qualità della vita, ridurre la paura di cadere e migliorare l'efficienza fisica. Le dimensioni di grande effetto riscontrate in particolare nella componente mentale dell’ECOS-16 suggeriscono un significato anche in termini di miglioramento della resilienza
Routing Metric Estimation in Multi-hop Wireless Networks with Fading Channel
No full textIn this paper we describe a statistical analysis of a
typical routing metric, Expected Transmission Time (ETT), used
for path evaluation in multi-hop wireless networks. The need of
statistics description is linked with the presence of network
parameters uncertainty due to both a fading channel and
ambiguity of nodes position. This analysis led us to define a
statistical estimator, which allows controlling all these effects, in
order to improve the quality of route choice during routing
decisions
A cross-sectional analysis between physical activity levels, weight status and empathy-related behaviors in a sample of Tuscany primary school children
No full textBackground: The present study aimed to investigate the relationship between physical activity (PA) and the development of relational empathy skills in children, taking into account weight status. Methods: Parents/guardians of primary school children were involved in filling out a questionnaire: the Empathy Questionnaire (EmQue-I13) and children were asked to complete the Physical Activity Questionnaire for Children (PAQ-C) to investigate the self-reported PA levels. The weight status was assessed using a self-reported Body Mass Index (BMI). Results: Three hundred seventy parents or guardians of students who attended primary school (8.53±1.61 yrs) were recruited. The total score was 2.41±0.89 for PAQ-C and 41.17±6.32 for EmQue-I13. The three domains of EmQue-I13 were: contagion (8.16±2.67), attention to others' feelings (19.40±2.99) and prosocial actions (13.62±3.01). Linear regression models showed that a higher PAQ-C score was positively associated with empathy-related total score P<0.000. Weight status, age and gender were not associated with EmQue-I13. Conclusions: Our results underline the positive association between physical activity and the development of relational empathic skills
Aggression and sport: A cross-sectional study on behavioral tendencies of athletes
Full text link: This cross-sectional study aimed to measure aggression in a more heterogeneous population of athletes, with the purpose of determining whether some specific conditions are related to aggressive behaviour. Athletes of 18-64 years old were enrolled in the study. The Italian version of Buss Perry Aggression Questionnaire (BPAQ) was self-administered. A total of 390 questionnaires were collected. Males showed higher levels of physical aggression (19.58 ± 6.32) than females (15.69 ± 6.65), p < 0.001 and a significant reduction in all domains of the questionnaire with advancing age, except for physical aggression. Furthermore, subjects who practiced full contact sports showed higher levels of physical aggression (20.23 ± 6.68) than those who practiced partial contact (17.89 ± 5.86) or non-contact sports (17.19 ± 6.64) p < 0.006. Finally, those who have played competitively in the past showed lower levels of anger (14.95 ± 5.22) than those who have played amateurishly (16.05 ± 5.54), p < 0.05. Age and gender appeared to be significant in aggression scores. Martial artists and combat sports players showed significantly higher levels of physical aggression than those who practice partial contact or non-contact sports. The type of sport (individual or team players), the practice time (beginners or experts) and the current level of sport (amateurs or competitive players) did not affect the aggression scores. Instead, the past level of sport participation is correlated with current anger
Breaking the sedentary: investigating the effects of active breaks on physical Activity and psychosocial well-being in primary school children
No full textPurpose: Sedentary behavior is a growing concern and has been linked to various health problems (Janssen et al., 2010). Moderate to vigorous Physical Activity (PA) Active Breaks (ABs), performed during sedentary periods, may be helpful in promoting physical activity and well-being in developmental ages. However, despite promising results, ABs are not widely used in schools (Biddle et al. 2016; Roset et al., 2020). Therefore, this study investigated the effect of an ABs intervention on PA levels and psychosocial aspects in primary school children.
Methods: A non-randomized controlled design was employed. The sample consisted of 67 primary school children (35 F and 32 M—avg. age 8.79 ± 0.94 y.). Throughout a three-month duration, children were engaged in 10-min ABs sessions twice a day during the cur- ricular school activities. PA levels were measured using the Physical Activity Questionnaire for Children (PAQ-C), and an ad-hoc ques- tionnaire was created to measure well-being and time-on-task behavior before and after ABs intervention. The questionnaire con- tained three subscales: well-being, concentration, and learning. Results: Results showed an increment in the PA levels (F = 19.80, p \ 0.001) and a higher scores on the Classroom Behavior Ques- tionnaire in the well-being subscale (F = 4.18, p = 0.04). Concentration subscale did not reveal differences between the pre- and post-intervention (F = 1.67, p [ 0.05) while learning subscale revealed lower score in the post- compared to the pre-intervention (F = 18.81, p < 0.001).
Conclusions: Even though this study follows a non-randomized controlled design, in accordance with existent literature (e.g., Janssen et al., 2010), its results offer compelling evidence for the effectiveness of ABs in promoting PA and psychosocial well-being among primary school children. This evidence is important for the classroom climate and the quality of the teaching–learning processes. However, the learning and concentration subscales did not produce the expected results, and they could be influenced by other variables. Therefore, our further investigations are orienteed to gain a com- prehensive understanding of this phenomenon.
References:
Biddle, et al. (2016). Too much sitting and all-cause mortality: Is there a causal link? BMC Pub. Health.
Janssen et al. (2010). Systematic review of the health benefits of P.A. and fitness in school-aged children and youth. Int. J. of Behav- ioral Nutrition and P.A..
Røset et al. (2020). Norwegian youngsters’ perceptions of P.E.: Exploring the implications for mental health. Sport, Edu. & Society
Primary and middle school students' views on inclusive physical education: Perceptions, practices, and future directions
Full text linkBackground: Physical Education (PE) classes are vital for nurturing students' social development and promoting collaboration. This study examined how primary and middle school students perceived PE classes, with a focus on collaboration, well-being and enjoyment, teacher behavior, the inclusion of nondisabled and disabled students, and general class behavior. Methods: One-hundred and seventy students (24 primary school and 146 middle school students) were surveyed using a questionnaire. Results: Exploratory Factor Analysis identified seven factors including: well-being, activities for all students, teacher-oriented behavior, collaboration, and attention to students with disabilities. Linear regressions on each identified Factor revealed higher well-being (Factor 1) between primary and middle school students. In addition, the perceived well-being in PE classes and staying together with classmates among younger middle school students was found to be higher than that reported by their older counterparts in middle school. The analysis also revealed that males perceived a higher well-being in PE classes than females. Conclusion: The research underscores that primary and especially middle school PE teachers should promote the well-being of students by creating inclusive and enjoyable PE classes. The PE classes should consider the differences between sexes and the individual differences. Finally, this research lays the foundation for future investigations to refine inclusive PE strategies and improve students' well-being
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