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A device-to-device (D2D) communication permits wireless devices to communicate mutually without network assistance. It promises to enhancement in spectral and network efficiency in the next-generat...

Device to Device (D2D) communications is a candidate technology for the fifth-generation (5G) and beyond mobile networks and certainly that results in high throughput, less energy consumption, reduce delay, and data traffic offload. Proximity services are the key enablers of D2D communications. A D2D technology boosts the performance and capacity of a conventional cellular system through the proximity services. To initiate the proximity services, Device Discovery (DD) is one of the the primary tasks. A DD makes the decision for effective D2D communications in terms of accuracy, speed, and minimum energy consumption. To discover the neighbor devices, the discovery signal is transmitted directly or through some access points. The discovery signal is affected by invaders during transmission which causes inaccuracy, energy consumption, and latency. Therefore, security and privacy issues must be addressed, especially in discovery signal transmission. In this paper, security and privacy issues in DD are highlighted. It is comprehensive and proves that in-band is much better than out-band with practical and technological reasons. To enhance the scope of the research, network level, and system level Security and Privacy (S&P) issues in the distributed and centralized systems environment with or without central management are surveyed. Along with an extensive survey is provided for the most recent work on DD concerning security and privacy issues, and comparison among in-band and out-band DD is performed. In the end, open issues are identified as future work on DD security and privacy in D2D communications. It is a novel survey in terms of security and privacy aspects of DD with possible suggested solutions for readers' motivation.

The device-to-device (D2D) communication is a candidate technology to implement 5G standards commercially. To initiate D2D, device discovery is a primary issue and very few algorithms have been proposed for device discovery. A discovery algorithm has many parameters to discover the accurate position of the devices in walking and velocity scenarios. Due to rapid changes in the environment, LOS and NLOS algorithms become complex and accurate discovery ventures. Therefore, it is needed to evaluate the performance of the discovery algorithms. In this paper, a methodological approach is introduced for the performance evaluation of discovery algorithms. The performance evaluation for discovery estimation errors and complexity is evaluated using metrics and parameters, and analysis is made for range-based RSS technique using performance metrics. Discussion of performance evaluation metrics and criteria is analyzed followed by numerical/experimental, simulation models, and the parameters which affect performance and assessment. The metrics and criteria are defined in terms of a discovery signal success ratio, average residual energy, accuracy, and root-mean-square error (RMSE). Two differentiating discovery studies, Hamming and Cosine, are given and contrasted with reference RMSE for evaluation. This paper concludes with a discovery algorithm improvement cycle overview from simulation to implementation. It decreases discovery error and enhances RMSE accuracy by an average of 21%. It also reduces the complexity of 12 pairs by Euclidean distance by 29%.

The narrow bandwidth and low gain performances of a reflectarray are generally improved at the cost of high design complexity, which is not a good sign for high-frequency operation. A dual resonance asymmetric patch reflectarray antenna with a single layer is proposed in this work for 5G communication at 26 GHz. The asymmetric patch is developed from a square patch by tilting its one vertical side by a carefully optimized inclination angle. A progressive phase range of 650&deg, is acquired by embedding a circular ring slot in the ground plane of the proposed element for gain improvement. A 332-element, center feed reflectarray is designed and tested, where its high cross polarization is suppressed by mirroring the orientation of asymmetric patches on its surface. The asymmetric patch reflectarray offers a 3 dB gain bandwidth of 3 GHz, which is 4.6% wider than the square patch reflectarray. A maximum measured gain of 24.4 dB has been achieved with an additional feature of dual linear polarization. Simple design with wide bandwidth and high-gain of asymmetric patch reflectarray make it suitable to be used in 5G communications at high frequencies.

Proximal device discovery is an essential initial phase in the installment of a device-to-device communication system in cellular networks. Therefore, an efficient device discovery scheme must be proposed with characteristics of minimum latency, discover maximum devices, and energy-efficient discovery in dense areas. In this paper, a bat echolocation-based algorithm derived from the bat algorithm is proposed and analyzed to fulfill the requirement of a proximal device discovery procedure for the cellular networks. The algorithm is applied to multiple hops and cluster devices when they are in a poor coverage zone. In this proposed algorithm, devices are not required to have prior knowledge of proximal devices, nor device synchronization is needed. It allows devices to start discovering instantly at any time and terminate the proximal device discovery session on completion of the discovery of the required proximal devices. Finally, device feedback is utilized to discover the hop devices in the clusters and analyze proximal discovery in a multi-hop setting. Along with this, a random device mobility pattern is defined based on human movement, and the device discovery algorithm is applied. The device discovery probability is calculated based on the contact duration and meeting time of the devices. We set up an upper bound less than 10 ms in long-term evolution of running time of the bat echolocation-based algorithm; this upper bound signifies the maximum degree of device discovery (more than 75% of the system) and the total number of devices. The outcomes thus imply that the proposed bat echolocation-based algorithm upper bound is better than 10 ms.

Device to Device (D2D) communication was first considered in out-band to manage energy issues in the wireless sensor networks. The primary target was to secure information about system topology for successive communication. Now the D2D communication has been legitimated in in-band by the 3rd Generation Partnership Project (3GPP). To initiate D2D communication, Device Discovery (DD) is a primary task and every D2D application benefits from DD as an end to end link maintenance and data relay when the direct path is obstructed. The DD is facing new difficulties because of the mobility of the devices over static systems, and the mobility makes it more challenging for D2D communication. For in-band D2D, DD in a single cell and multi-cell, and dense area is not legitimated properly, causing latency, inaccuracy, and energy consumption. Among extensive studies on limiting energy consumption and latency, DD is one of the essential parts concentrating on access and communication. In this paper, a comprehensive survey on DD challenges, for example single cell/multi-cell and dense area DD, energy consumption during discovery, discovery delay, and discovery security, etc., has been presented to accomplish an effective paradigm of D2D networks. In order to undertake the device (user) needs, an architecture has been projected, which promises to overwhelm the various implementation challenges of DD. The paper mainly focuses on DD taxonomy and classification with an emphasis on discovery procedures and algorithms, a summary of advances and issues, and ways for potential enhancements. For ensuring a secure DD and D2D, auspicious research directions have been proposed, based on taxonomy.

At-site flood frequency analysis is a direct method of estimation of flood frequency at a particular site. The appropriate selection of probability distribution and a parameter estimation method are important for at-site flood frequency analysis. Generalized extreme value, three-parameter log-normal, generalized logistic, Pearson type-III and Gumbel distributions have been considered to describe the annual maximum steam flow at five gauging sites of Torne River in Sweden. To estimate the parameters of distributions, maximum likelihood estimation and L-moments methods are used. The performance of these distributions is assessed based on goodness-of-fit tests and accuracy measures. At most sites, the best-fitted distributions are with LM estimation method. Finally, the most suitable distribution at each site is used to predict the maximum flood magnitude for different return periods.

A device to device (D2D) communication is a direct link between the cellular devices in the next generation networks. The probability of D2D links in dense areas like in a stadium, shopping malls, and housing societies is high due to the existence of large number of devices. However, an accurate, fast, and energy efficient discovery algorithm is needed to perform D2D communication. The device discovery is a primary task to initiate D2D communication. If it is not legitimate properly may present noteworthy latency to access the system. This paper presents the belief space search algorithm for in-band device discovery cellular network. The circular network coverage area is divided into small rings and each ring belongs to a belief space. This strategy reduces the exhaustive search for the devices in the whole coverage area (space). It searches only belief space where devices are. Therefore, it saves time and energy with higher accuracy. A mathematical model for the belief space is made and verified by the simulations. It has 90% accuracy, saves 13% energy and 28% efficient than whole space search.

Languages provide speakers with a wide range of linguistic units to organize and deliver information (Jisa, Reilly, Verhoeven, Baruch & Rosado, 2002). There are several ways to verbally express the mental representations of events. The speaker, according to the linguistic tools he has acquired, selects the one that brings out the most communicative effect to convey his message.Our study focuses on two markers in Amharic, -mm and dämmo, which abound in the language and in narratives in particular. Our aim is to examine, from a developmental perspective, how the speakers use them, and the functions these elements have in their narratives. We seek to distinguish the communicative and pragmatic functions indicated by means of these markers. To do so, we created a corpus of sixty narrative productions of children from 5-6, 7-8 to 10-12 years old and adult Amharic speakers. The material we used to collect our data is a series of pictures without text “Frog, Where are you?” (Mayer, 1969). This experimental material has already been used in many developmental studies and in several languages (Bamberg, 1987 ; Kail & Hickmann, 1992 ; Berman & Slobin, 1994 ; Kern 1997 ; Akinci, 1999 ; Strömqvist &Verhoeven 2003 ; Jisa, Chenu, Fekete & Omar, 2010 ; Fekete, 2011, Saïdi 2014 and many more).The results show that -mm and dämmo, although all the speakers use them both, do not always have the same scope according to the speaker and vary according to the age. dämmo is mainly used to mark a contrastive topic to signal the concomitance of the events. It seems to be easy to use for children compared to -mm which is much more complex, not only because of its synthetic structure but primarily because it is a multi-purpose morpheme. -mm anchors the information into the context, it highlights the constituent on which it operates., Les langues offrent une multitude d’éléments linguistiques pour organiser et délivrer les informations (Jisa, Reilly, Verhoeven, Baruch & Rosado, 2002). Il y a plusieurs manières d’exprimer en mot la représentation mentale des événements. Le locuteur, en fonction des outils linguistiques dont il dispose, choisit les formes qui lui apportent le plus de valeur communicative pour transmettre son message.Notre étude est centrée sur deux connecteurs de l’amharique, -mm et dämmo, qui sont abondants dans la langue, et dans la narration en particulier. Nous avons pour objectif d’examiner, dans une perspective développementale, comment les locuteurs les utilisent, et les fonctions que ces particules ont dans leurs narrations. Nous cherchons à distinguer les fonctions communicatives ou pragmatiques qui sont signalées dans l’énoncé au moyen de ces marques. Pour ce faire, nous avons constitué un corpus de soixante productions narratives d’enfants de groupes d’âges différents (5-6, 7-8 et 10-12 ans) et d’adultes locuteurs d’amharique. Nous avons utilisé le support imagé sans texte « Frog, where are you? » (Mayer, 1969) pour recueillir nos données. Ce matériel expérimental a déjà servi à de nombreuses études développementales dans plusieurs langues (Bamberg, 1987 ; Kail & Hickmann, 1992 ; Berman & Slobin, 1994 ; Kern 1997 ; Akinci, 1999 ; Strömqvist &Verhoeven 2003 ; Jisa, Chenu, Fekete & Omar, 2010 ; Fekete, 2011, Saïdi 2014 entre autres).Les résultats montrent que le clitique -mm et la locution dämmo, bien qu’ils soient tous les deux employés par tous les locuteurs, n’ont pas toujours la même portée selon le locuteur et varient en fonction de l’âge. dämmo, marque principalement le thème contrasté pour montrer la concomitance des événements. Il s’avère être plus maniable pour les enfants par rapport à –mm qui est beaucoup plus complexe, non seulement de par sa structure synthétique mais surtout parce qu’il est multiusage. –mm ancre l’information dans le contexte, il met en exergue le constituant sur lequel il opère.

Il est indiscutable que le dialogue quotidien en face à face constitue le berceau de l'acquisition de la langue. Les premiers énoncés de l'enfant ne sont interprétables que dans la mesure où l'on a accès à la situation physique dans laquelle il se trouve et à la contribution des autres participants dans le contexte conversationnel. De très nombreuses recherches se sont attachées à comprendre comment les adultes étayent les premières compétences narratives des enfants dans l'interaction conver...

BACKGROUND: Suboptimal management of asthma by general practitioners (GPs) can lead to poor health outcomes AIMS: To assess the management of common asthma presentations by GPs using the Global Initiative for Asthma (GINA) guidelines as a comparative tool. METHODS: A cross-sectional survey was conducted in Karachi, Pakistan. Of 250 GPs approached, 192 completed a self-administered questionnaire regarding pathology, key history points, risk factors, diagnosis, and management of asthma. RESULTS: Overall, 28.6% of GPs had adequate knowledge of the core concepts of asthma, while only 10.4% had adequate practice in asthma management. About 78% of GPs had inadequate knowledge of pathology, about 90% had inadequate knowledge of medications to be used, and 63% had inadequate knowledge regarding diet restrictions. Knowledge regarding symptoms not usually associated with asthma was adequate, as was knowledge regarding non-pharmacological management (79% each). Practices regarding asthma diagnosis were good (99.0%). However, practices regarding acute exacerbations and patients who wish to exercise were inadequate in 85.9% and 82.8% of GPs, respectively. CONCLUSIONS: The majority of GPs had poor knowledge and practice of asthma. We recommend initiation of programmes to improve their knowledge and practices.

Device to Device (D2D) communication is a new paradigm for next-generation wireless systems to offload data traffic. A device needs to discover neighbor devices on the certain channel to initiate the D2D communication within the minimum period. A device discovery technique based on Global Positioning System (GPS) and neighbor awareness base are proposed for in-band cellular networks. This method is called network-centric approach, and it improves the device discovery efficiency, accuracy, and channel capacity. The differential code is applied to measure the signal to noise ratio of each discovered device. In the case that the signal to noise ratio (SNR) of two devices is above a specified threshold value, then these two devices are qualified for D2D communication. Two procedures are explored for device discovery; discovery by CN (core network) and eNB (evolved node B) cooperation with the help of GPS and neighbor awareness. Using ‘Haversine’ formula, SNR base distance is calculated. Results show an increment in the channel capacity relative to SNR obtained for each device.

The performance of maximum likelihood (ML) and sphere decoding (SD) are investigated when the channel is uncertain. In this work, a modified low complexity approach is proposed to deal with the effects of the channel uncertainty and obtain robust ML and SD. A higher complexity approach is also suggested but is not investigated here as it appears to be unsuitable for real time applications. The approach adopted involves linearly preprocessing the received signal to suppress the interference caused by channel uncertainty before applying a detector. Parallels of this approach may be found in the channel shortening literature where it is suggested to linearly preprocess the received signal with a channel shortener to reduce the effective delay spread of the intersymbol interference (ISI) channel before applying a reduced state Viterbi decoder to bring down the complexity of ML decoding. In our case, however, the preprocessing is applied to reduce the effect of the interference caused by channel uncertainty.

Comment et pourquoi les enfants apprennent-ils à parler ? Pourquoi certains d'entre eux éprouvent-ils des difficultés pour y parvenir alors même que d'autres y réussissent précocément ? Quelles conséquences peut avoir une situation de bilinguisme sur cet apprentissage ? Peut-on acquérir une compétence native dans une nouvelle langue à l'âge adulte ? Quelles sont les difficultés rencontrées plus spécifiquement à l'écrit ? Les chercheurs ne sont pas encore en mesure de répondre de manière précise à toutes ces questions. Pourtant, les deux dernières décennies ont vu se préciser un grand nombre de réponses ou d'éléments de réponse. Cet ouvrage propose un large aperçu des avancées obtenues, à l'interface de plusieurs disciplines des sciences cognitives, concernant l'acquisition de la langue maternelle, le bilinguisme et l'acquisition des langues secondes, l'apprentissage de l'écrit et les troubles du langage, oral ou écrit. Cet ouvrage offre au lecteur un vaste panorama des recherches récentes et de leurs résultats, ainsi que des méthodes parfois extrêmement sophistiquées qui permettent de les obtenir. Il présente dans le même temps, les questions qui restent en suspens et que la décennie à venir aura à affronter. Il fournit aux enseignants, aux thérapeutes, aux parents et aux étudiants un ensemble de textes rédigés par quelques-uns des meilleurs spécialistes internationaux de l'acquisition du langage.