Analysis of the Least Squares Approach to Broadband Beamspace Beamforming

In this paper, we present a comprehensive comparison of different structures for broadband beamforming. We focus on both the tapped delay line (TDL) and the least squares (LS), beamspace approaches. Through simulations we confirm the superiority of the beamspace method (i.e., less complex and better frequency invariance). However, its anti-jamming ability is reduced due to non-orthogonal beams. We show how to mitigate this via a reduced rank approximation of the autocorrelation matrix

Secure D2D Communication in Large-Scale Cognitive Cellular Networks with Wireless Power Transfer

In this paper, we investigate secure device-to-device (D2D) communication in energy harvesting large-scale cognitive cellular networks. The energy constrained D2D transmitter harvests energy from multi-antenna equipped power beacons (PBs), and communicates with the corresponding receiver using the spectrum of the cellular base stations (BSs). We introduce a power transfer model and an information signal model to enable wireless energy harvesting and secure information transmission. In the power transfer model, we propose a new power transfer policy, namely, best power beacon (BPB) power transfer. To characterize the power transfer reliability of the proposed policy, we derive new closed-form expressions for the exact power outage probability and the asymptotic power outage probability with large antenna arrays at PBs. In the information signal model, we present a new comparative framework with two receiver selection schemes: 1) best receiver selection (BRS), and 2) nearest receiver selection (NRS). To assess the secrecy performance, we derive new expressions for the secrecy throughput considering the two receiver selection schemes using the BPB power transfer policies. We show that secrecy performance improves with increasing densities of PBs and D2D receivers because of a larger multiuser diversity gain. A pivotal conclusion is reached that BRS achieves better secrecy performance than NRS but demands more instantaneous feedback and overhead

Secure D2D Communication in Large-Scale Cognitive Cellular Networks: A Wireless Power Transfer Model

In this paper, we investigate secure device-to-device (D2D) communication in energy harvesting large-scale cognitive cellular networks. The energy constrained D2D transmitter harvests energy from multi-antenna equipped power beacons (PBs), and communicates with the corresponding receiver using the spectrum of the primary base stations (BSs). We introduce a power transfer model and an information signal model to enable wireless energy harvesting and secure information transmission. In the power transfer model, three wireless power transfer (WPT) policies are proposed: 1) cooperative power beacons (CPB) power transfer, 2) best power beacon (BPB) power transfer, and 3) nearest power beacon (NPB) power transfer. To characterize the power transfer reliability of the proposed three policies, we derive new expressions for the exact power outage probability. Moreover, the analysis of the power outage probability is extended to the case when PBs are equipped with large antenna arrays. In the information signal model, we present a new comparative framework with two receiver selection schemes: 1) best receiver selection (BRS), where the receiver with the strongest channel is selected, and 2) nearest receiver selection (NRS), where the nearest receiver is selected. To assess the secrecy performance, we derive new analytical expressions for the secrecy outage probability and the secrecy throughput considering the two receiver selection schemes using the proposed WPT policies. We presented Monte-carlo simulation results to corroborate our analysis and show: 1) secrecy performance improves with increasing densities of PBs and D2D receivers due to larger multiuser diversity gain, 2) CPB achieves better secrecy performance than BPB and NPB but consumes more power, and 3) BRS achieves better secrecy performance than NRS but demands more instantaneous feedback and overhead. A pivotal conclusion is reached that with increasing number of antennas at PBs, NPB offers a comparable secrecy- performance to that of BPB but with a lower complexity

Artificial-Noise Aided Secure Transmission in Large Scale Spectrum Sharing Networks

We investigate beamforming and artificial noise generation at the secondary transmitters to establish secure transmission in large scale spectrum sharing networks, where multiple noncolluding eavesdroppers attempt to intercept the secondary transmission. We develop a comprehensive analytical framework to accurately assess the secrecy performance under the primary users' quality of service constraint. Our aim is to characterize the impact of beamforming and artificial noise generation (BF&AN) on this complex large scale network. We first derive exact expressions for the average secrecy rate and the secrecy outage probability. We then derive an easy-to-evaluate asymptotic average secrecy rate and asymptotic secrecy outage probability when the number of antennas at the secondary transmitter goes to infinity. Our results show that the equal power allocation between the useful signal and artificial noise is not always the best strategy to achieve maximum average secrecy rate in large scale spectrum sharing networks. Another interesting observation is that the advantage of BF&AN over BF on the average secrecy rate is lost when the aggregate interference from the primary and secondary transmitters is strong, such that it overtakes the effect of the generated AN

Variability assessment and construction of infectious clone of Indian Apple Scar Skin Viroid

Apple scar skin viroid (ASSVd) is widely distributed and economically important pome-fruit infecting viroid belonging to the genus Apscaviroid. It causes huge economic losses to the apple industry. Apple fruits with dappling, scarring, cracking and deformation symptoms were noticed during survey of apple growing regions of Himachal Pradesh, India. ASSVd was detected from four isolates showing dappled fruits. Molecular characterization of the viroid was done. Ten clones each from five isolates were sequenced out of which seven new sequence variants of ASSVd were found. Four of the clones were 330 nucleotides (nt) long and the other eight had an additional nucleotide. The clones showed significant sequence variability (94-100%) with each other. Variability was more common in the pathogenic domain of the viroid genome. Present isolates grouped with some Chinese and Korean isolates in phylogenetic analysis. The study reports seven new sequence variants of ASSVd and also gives a first molecular evidence of a viroid infection (ASSVd) in apple from India. Infectious clone of ASSVd were constructed for in vitro mutagenic studies. Keywords: Apple scar skin viroid, cloning, DNA sequencing, phylogenetic analysi

Prevalence of hepatitis C virus in lymphoproliferative disorders

Objective: To study the prevalence of hepatitis C virus in lymphoproliferative disorders. Methods: A case control prospective study was performed on 143 patients with lymphoproliferative disorders and 29 patients with non-hematological malignancies were taken as controls. All the patients in both groups were analyzed for various risk factors for infection with hepatitis C virus and were tested for the presence of hepatitis C virus antibody (anti HCV), cryoglobulins and rheumatoid factor antibody. Hepatitis C viremia was documented by detection of HCV RNA by polymerase chain reaction. Results: There was no significant difference for risk factors for hepatitis C virus infection in both the groups except for the increase in number of surgical procedures being carried out in the control group. There was no significant difference in the presence of rheumatoid factor antibody in both the groups and cryoglobulins were not positive in any individual. Five percent patients with lymphoproliferative disorders and 3.4% with non-hematological malignancies were positive for anti HCV. HCV RNA was detected in 29.2% cases and 31.0% in controls. Conclusion: There was no association between hepatitis C virus infection and lymphoproliferative disorder in our population. However, further studies are required from this region to establish any causal relationship between hepatitis C virus infection and lymphoproliferative disorde

A unique case of urinary bladder simple melanosis: a case report and review of the literature

Melanosis refers to abnormal or excessive deposition of melanin pigment in the cells and/or tissue, which can be seen in any organ but commonly in skin and oral mucosa. Melanosis of the urinary bladder is an extremely rare benign condition and only a handful of cases been reported in the English literature before. In this article, we report a new case of urinary melanosis, describe the differential diagnostic features from pseudomelanosis and offer clues for correct diagnosis. We also provide comprehensive review of the literature on the subject

Experimental and Kinetic Study of the Effect of using Zr- and Pt-loaded Metals on Y-zeolite-based Catalyst to Improve the Products of n-heptane Hydroisomerization Reactions

The escalating cost of Pt metal has prompted researchers to incorporate other metals into Pt/catalysts to reduce the amount of Pt. In this work, several bimetallic Pt-Zr/HY-zeolite catalysts were prepared by incorporating small amounts of the inexpensive Zr into the Pt/HY-zeolite to form an active and selective catalyst. Results showed that although half of the required platinum metal was used, the catalytic activity of the prepared Pt-Zr/HY bimetallic catalyst was higher than that of the monometallic (Pt or Zr)/HY catalysts, as a result of the improved Lewis acidity of that catalyst that resulted from the addition of the Zr metal; additionally, the branched alkanes' yield also increased. The optimum catalyst was bimetallic, containing 0.5 wt% Pt + 0.5 wt% Zr, which achieved the highest yield of isomers at 70.2 mol%, along with 82.61 and 84.98 mol% for conversion and selectivity, respectively, under 1 MPa and 250°C reaction conditions. In addition, the hydroisomerization reaction kinetic model was achieved, giving good predicted results in agreement with the experimental calculations, with an acceptable relative error. It was found that lower activation energies (about 44.5 kJ/mol) were needed for olefin hydrogenation to iso-paraffins, while higher activation energies were required for i-paraffin hydrocracking (about 138.1kJ/mol)

Bank stability : the case of Nordic and non-Nordic banks in Latvia

The banking industry is facing huge challenges due to technology-enabled innovation, to changes in customer preferences, to bank de-risking and to new regulatory initiatives. To go through all these changes, banks need to be stable. The present study contributes to the empirical literature by identifying the determinants of stability of banks in the Latvian Banking Industry. This study covers both bank-specific (endogenous) factors and macroeconomic (exogenous) factors that impact the stability of banks. The data set used in this study is the annual financial statements of Latvian banks operated in the period 2003-2016. Using multivariate regression analysis techniques, we found evidence that credit risk and efficiency ratio have a significant negative impact on banks’ stability, whereas size of the bank, liquidity ratio, profitability, inflation and GDP growth have significant positive impact on bank’s stability. We made comparison of bank-specific variables performance for Nordic-owned and non-Nordic-owned banks. Credit and liquidity risks, as well as efficiency ratio for Nordic-owned banks during the research period were higher, whereas size of the banks and profitability were better. Comparing measurement results of stability of banks, we received that Nordic-owned banks performance between 2003 to 2016 was better than non-Nordic-owned banks performance.peer-reviewe