The Achievable Rate of Interweave Cognitive Radio in the Face of Sensing Errors

Cognitive radio (CR) systems are potentially capable of mitigating the spectrum shortage of contemporary wireless systems. In this paper, we provide a brief overview of CR systems and the important research milestones of their evolution, along with their standardization activities, as a result of their research. This is followed by the detailed analysis of the interweave policy-based CR network (CRN) and by a detailed comparison with the family of underlay-based CRNs. In the interweave-based CRN, sensing of the primary user's (PU) spectrum by the secondary user's (SU) has remained a challenge, because the sensing errors prevent us from fulfilling the significant throughput gains that the concept of CR promises. Since missed detection and false alarm errors in real-time spectrum sensing cannot be avoided, based on a new approach, we quantify the achievable rates of the interweave CR by explicitly incorporating the effect of sensing errors. The link between the PU transmitter and the SU transmitter is assumed to be fast fading. Explicitly, the achievable rate degradation imposed by the sensing errors is analyzed for two spectrum sensing techniques, namely, for energy detection and for magnitude squared coherence-based detection. It is demonstrated that when the channel is sparsely occupied by the PU, the reusing techniques that are capable of simultaneously providing low missed detection and false alarm probabilities cause only a minor degradation to the achievable rates. Furthermore, based on the achievable rates derived for underlay CRNs, we compare the interweave CR and the underlay CR paradigms from the perspective of their resilience against spectrum sensing errors. Interestingly, in many practical regimes, the interweave CR paradigm outperforms the underlay CR paradigm in the presence of sensing errors, especially when the SNR at the SU is below 10 dB and when the SNR at the PU is in the range of 10-40 dB. Furthermore, we also provide rules of thumb that identify regimes, where the interweave CR outperforms the underlay CR

Geotechnical Properties of Compacted Silty Clay Mixed With Different Sludge Contents

The presence of organic matter in soil may cause different problems depending on many factors such as type and contents of these organic materials. A testing program was carried out to study the geotechnical properties and the behavior of organic matter obtained by the addition of a sludge material brought from a sewerage treatment plant.The tests include classification, chemical, compaction, compressibility and shear strength tests. Based on the results, several conclusions have been obtained. Both liquid and plastic limits increased with increasing organic matter. Regarding compaction test, it can be noticed that both maximum dry density and optimum moisture content slightly decreased with increasing organic contents then tends to increase.Through the observation of shear strength test results, qu and cu increased with increasing organic matter contents and then tends to decrease in similar manner to the density water relation of compaction test. Regarding compressibility, organic content, water content, void ratio and arrangement of soil particles are dominant factors controlling this property. The compression behavior of organic soils varies from the compression behavior of other types of soils in two ways, first the compression of organic soils is much larger and second, the creep or secondary compression plays an important role in determining the total settlement as shown in developing a unique relationship for organic soils

Percutaneous needle biopsy for indeterminate renal masses: a national survey of UK consultant urologists

<p>Abstract</p> <p>Background</p> <p>The use of percutaneous needle biopsy in the evaluation of indeterminate renal masses is controversial and its role in management remains largely unclear. We set to establish current practice on this issue in UK urology departments.</p> <p>Methods</p> <p>We conducted a national questionnaire survey of all consultant urologists in the UK, to establish current practice and attitudes towards percutaneous needle biopsy in the management of indeterminate renal masses.</p> <p>Results</p> <p>139 (43%) consultant urologists never use biopsy, whereas 111 (34%) always employ it for the diagnosis of indeterminate renal masses. 75 (23%) urologists use biopsy only for a selected patient group. Mass in a solitary kidney, bilateral renal masses and a past history of non-renal cancer were the main indications for use of percutaneous biopsy. The risk of false negative results and biopsy not changing the eventual management of their patients were the commonest reasons not to perform biopsy.</p> <p>Conclusion</p> <p>There is a wide and varied practice amongst UK Consultant Urologists in the use of percutaneous biopsy as part of the management of indeterminate renal masses. The majority of urologists believe biopsy confers no benefit. However there is a need to clarify this issue in the wake of recent published evidence as biopsy results may provide critical information for patients with renal masses in a significant majority. It not only differentiates benign from malignant tissue but can also help in deciding the management option for patients undergoing minimally invasive treatments.</p

Optimal Distribution of Renewable Energy Systems Considering Aging and Long-Term Weather Effect in Net-Zero Energy Building Design

Generation system interruptions in net-zero energy buildings (NZEBs) may result in missing the net-zero targets by a great margin. Consequently, it is significant to incorporate a realistic reliability model for renewable energy systems (RESs) that considers aging and long-term weather conditions. This study proposed a robust design optimization method that deals with the selection of RES to achieve NZEB. Different case studies were evaluated: 1. Deterministic approach; 2. Markov chain-based reliability without the aging effect; 3. Markov chain-based reliability with the aging effect. The results showed that the optimal sizes of RES, considering the aging effect, were much larger than the other two cases based on the annual energy balance. Moreover, the consideration of the aging effect on the reliability assessment of the generation system for NZEB opens a pathway for a more robust and economic design of RES

The Role of Social Media Platforms in Confronting Intellectual Extremism from Majmaah University Students Perspective

The present study aims to investigate the role of social media platforms in confronting intellectual extremism among Majmaah University students. The researchers conducted the descriptive analytical approach and applied a 20- item questionnaire to a randomly selected sample of (213) students. The results showed that Tik Tok and Snapchat were ranked first among the study sample. Also, there was a moderate negative impact of social media on intellectual security, with a mean of (2.99). This is due to the nature of the content published on networks and its impact on the subscribers. It indicated the importance of social media, more specifically Tik Tok and Snapchat, among the sample of the study. It can be attributed to gender since females are more interested in social networks to publish and share photos. Moreover, the results revealed that social media platforms played a moderate role in resisting intellectual deviation among the participants, with an average mean of (2.96). There were no statistical differences in the impact of social media platforms on young peoples intellectual security and their role in resisting intellectual extremism due to responses to the study questions. The findings of the study call for the necessity of activating the positive role of social media by exploring new approaches to evolve effective alternatives in dealing with social networks by enhancing young peoples media literacy. Contribution/Originality: This study contributed to the existing literature by identifying the role of social media in combating intellectual extremism from the perspective of students at Majmaah University, Saudi Arabia. It also explored the most popular social media platforms among university students and their impact on students intellectual security