Performance Analysis of a New MAC Protocol for Wireless Cognitive Radio Networks

Wireless Personal Communications - In this study, network performance analysis of a newly proposed cognitive radio wireless network (CRWN) medium access control (MAC) protocol is investigated in...     

Semantic analysis on social networks: A survey

As social networks are getting more and more popular day by day, large numbers of users becoming constantly active social network users. In this way, there is a huge amount of data produced by users in social networks. While social networking sites and dynamic applications of these sites are actively used by people, social network analysis is also receiving an increasing interest. Moreover, semantic understanding of text, image, and video shared in a social network has been a significant topic in the network analysis research. To the best of the author's knowledge, there has not been any comprehensive survey of social networks, including semantic analysis. In this survey, we have reviewed over 200 contributions in the field, most of which appeared in recent years. This paper not only aims to provide a comprehensive survey of the research and application of social network analysis based on semantic analysis but also summarizes the state‐of‐the‐art techniques for analyzing social media data. First of all, in this paper, social networks, basic concepts, and components related to social network analysis were examined. Second, semantic analysis methods for text, image, and video in social networks are explained, and various studies about these topics are examined in the literature. Then, the emerging approaches in social network analysis research, especially in semantic social network analysis, are discussed. Finally, the trending topics and applications for future directions of the research are emphasized; the information on what kind of studies may be realized in this area is given.     

Cost Effective Smart System for Water Pollution Control with Underwater Wireless Sensor Networks: A Simulation Study

The underwater sensor network is a rapidly developing area of research with a wide range of applications such as data collection in the ocean, pollution monitoring, and ocean sampling. One of the most researched areas is the coverage of underwater sensor networks, which are the basis of many applications. The coverage is usually related to how effectively a network is monitored by the sensor. There are major problems in the ocean or marine region, especially in water pollution. Underwater pollution generally causes acidification, plastic residues, and toxins. Today, the determination of this pollution is carried out through a human surveillance monitoring process. Therefore, there is a need for an automatic and intelligent monitoring system to identify the formation of pollution. The proposed simulation model defines the intelligent sensor-based monitoring system that identifies and alarms the formation of underwater pollution. Aloha was chosen as the medium access protocol for the cost-effective system in which we designed the simulation model. The efficiency of the system has been shown to be more stable, cost-effective and manageable than the monitoring process involving the existing human surveillance by testing with the simulation model.     

Effect of different surface treatments on the shear bond strength of resin cement to zirconia ceramic and metal alloy*

The bonding of resin cement to ceramic materials plays an important role in dentistry. The purpose of this study is to evaluate the effects of various surface treatments on the shear bond strength (SBS) of zirconia ceramic and metal alloy. A total of 60 specimens were prepared from Y-TZP ceramic and metal alloy. The specimens were divided into three subgroups (n = 10) that received different surface treatments for each material. An Er:YAG laser (ER), a femtosecond laser (FS), and air-borne particle abrasion (A) were employed as surface treatments. One specimen from each group was analyzed using a scanning electron microscope (SEM) at 500 x magnification after surface treatments. The self-adhesive resin cement was then bonded to the treated surfaces using a Teflon mold. The specimens were thermocycled for 5,000 cycles at 5–55 °C, and then the SBS test was performed. Kruskal–Wallis and Mann–Whitney U tests were used to determine the differences between the groups (p = 0.05), and failure modes were evaluated for each specimen. Statistical analyses revealed significant differences between the surface treatment methods. The mean SBS values of the air-borne particle-abraded groups were higher than those of the other groups. The femtosecond-irradiated groups of each material showed significantly higher SBS values than the Er:YAG-irradiated groups (p < 0.05). Within the limitations of this study, air-borne particle abrasion and the femtosecond laser were more effective than Er:YAG laser treatment.     

Artificial bee colony–based spectrum handoff algorithm in wireless cognitive radio networks

In this work, we proposed a new artificial bee colony–based spectrum handoff algorithm for wireless cognitive radio systems. In our wireless cognitive radio system, primary users, secondary users, and related base stations exist in the same communication environment. For our artificial bee colony–based algorithm, secondary users that always struggle to discover an idle channel have a leading role. While honey bees work hard to find the best‐quality nectar source for foraging, secondary users try to find idle channels for making communication. In this way, secondary users are organized for different missions such as sensing and handoff similar to honey bees to minimize spectrum handoff delay by working together. In the spectrum handoff stage, some secondary users must sense the spectrum so that the interrupted secondary user may perform the spectrum handoff process. In our developed spectrum handoff algorithm, the spectrum availability characteristic is observed on the basis of the missions of the bees in the artificial bee colony algorithm with the aim of minimizing the spectrum handoff delay and maximizing probability of finding an idle channel. With the help of the algorithm that is developed using the artificial bee colony, spectrum handoff delay of secondary users is considerably decreased for different number of users without reducing probability of finding an available channel.     

CTAB-assisted hydrothermal synthesis of NiFe2O4 and its magnetic characterization

A simple hydrothermal route is demonstrated for the synthesis of nickel ferrite nanocrystals, NiFe₂O₄, using cetyltrimethylammonium bromide (CTAB) as the surfactant and NH₃ and NaOH as hydrolyzing agents. Synthesized materials have been characterized by XRD, FTIR, ESR, and TEM techniques. It was found that crystallization in both hydrolyzing agent led to nanometric in size. Average particle size of prepared samples was calculated from TEM micrographs and varied significantly between samples prepared using different hydrolyzing agents; it was 12 nm when conc. NH₃ was used and 50 nm when 2 M NaOH was used. Crystallite size obtained using Scherrer equation agreed well with the TEM observations with the respective values of 15 and 55 nm. ESR analysis showed single broad bands which might indicate the phase homogeneity of the materials. Furthermore, linewidths were observed to differ due to the difference in magnetization that depends on the particle size; NiFe₂O₄ sample hydrolysed with NH₃ has a larger linewidth revealing its smaller particle size as confirmed by XRD and TEM techniques.     

Family formation,parental background and young adults’ first entry into homeownership in Britain and Germany

Abstract

Although previous research shows that family dynamics and parental socioeconomic status influence the timing of young adults’ first entry into homeownership, much less is known about how the role of family factors may vary across countries with different housing systems. In this article, we use panel survey data from Britain and Germany to compare how family life course careers and parental socioeconomic background influence young adults’ initial entry into homeownership in these two divergent national contexts. The results show that in Britain, first-time homeownership transitions are tightly synchronized with partnership formation. By contrast, in Germany first moves into homeownership typically occur later around or after the arrival of children. Parental owner-occupation accelerates entry into homeownership in both contexts, while the effects of other parental characteristics are relatively muted. Furthermore, the results highlight how individual socioeconomic factors are critical determinants of entering owner-occupation. This is particularly true in Britain where there is a strong socioeconomic gradient in first-time homeownership transitions.     

Cooperative communication based access technique for sensor networks

ABSTRACT

The collaboration of users in communication systems is defined as cooperative communication. The cognitive radio, i.e. dynamic spectrum access technique, is a wireless communication technology that provides a great chance for unlicensed users to exploit the frequency bands in an opportunistic way. A wireless sensor network is a widely used communication technology composing of spatially distributed independent sensors in order to monitor physical or environmental circumstances. In this work, a new technique that unlicensed users become a cooperative relay when they are in idle mode is proposed. Along with the proposed technique, unlicensed users help sensor nodes as a cooperative relay when they are in idle mode. Similarly, sensor nodes help unlicensed users for detecting idle frequency bands while in sleep mode. By preventing any disruption that remote users may be exposed owing to signal attenuation, the proposed cooperative relay utilises amplify and forward based cooperative communication protocol. Thanks to this approach; the overall network has greater performance than wireless sensor network that does not use cooperative communication based dynamic access technique in terms of throughput, energy, and delay.     

Exploiting cognitive wireless nodes for priority‐based data communication in terrestrial sensor networks

A priority‐based data communication approach, developed by employing cognitive radio capacity for sensor nodes in a wireless terrestrial sensor network (TSN), has been proposed. Data sensed by a sensor node—an unlicensed user—were prioritized, taking sensed data importance into account. For data of equal priority, a first come first serve algorithm was used. Non‐preemptive priority scheduling was adopted, in order not to interrupt any ongoing transmissions. Licensed users used a nonpersistent, slotted, carrier sense multiple access (CSMA) technique, while unlicensed sensor nodes used a nonpersistent CSMA technique for lossless data transmission, in an energy‐restricted, TSN environment. Depending on the analytical model, the proposed wireless TSN environment was simulated using Riverbed software, and to analyze sensor network performance, delay, energy, and throughput parameters were examined. Evaluating the proposed approach showed that the average delay for sensed, high priority data was significantly reduced, indicating that maximum throughput had been achieved using wireless sensor nodes with cognitive radio capacity.