Sidelobe Control in Collaborative Beamforming via Node Selection

Collaborative beamforming (CB) is a power efficient method for data communications in wireless sensor networks (WSNs) which aims at increasing the transmission range in the network by radiating the power from a cluster of sensor nodes in the directions of the intended base station(s) or access point(s) (BSs/APs). The CB average beampattern expresses a deterministic behavior and can be used for characterizing/controling the transmission at intended direction(s), since the mainlobe of the CB beampattern is independent on the particular random node locations. However, the CB for a cluster formed by a limited number of collaborative nodes results in a sample beampattern with sidelobes that severely depend on the particular node locations. High level sidelobes can cause unacceptable interference when they occur at directions of unintended BSs/APs. Therefore, sidelobe control in CB has a potential to increase the network capacity and wireless channel availability by decreasing the interference. Traditional sidelobe control techniques are proposed for centralized antenna arrays and, therefore, are not suitable for WSNs. In this paper, we show that distributed, scalable, and low-complexity sidelobe control techniques suitable for CB in WSNs can be developed based on node selection technique which make use of the randomness of the node locations. A node selection algorithm with low-rate feedback is developed to search over different node combinations. The performance of the proposed algorithm is analyzed in terms of the average number of trials required to select the collaborative nodes and the resulting interference. Our simulation results approve the theoretical analysis and show that the interference is significantly reduced when node selection is used with CB.Comment: 30 pages, 10 figures, submitted to the IEEE Trans. Signal Processin

Numerical assessment of the overall heat transfer and pressure drop performances of an aqueous ammonia base-nanofluids in rectangular microchannel heat sinks

In this paper, the thermal and hydrodynamic performances of an aqueous ammonia base-nanofluid (Al2O3-NH3(aqu)) cooled in a rectangular microchannel heat sink was numerically investigated. The range of Reynolds number used in the investigation were between 140-1400. In order to assess the performance of the system during the employment of the proposed nanofluid, H2O and Al2O3-H2O were also tested and their performances were compared to Al2O3-NH3(aqu) performance in terms of thermal resistance and pressure drop. Results from the simulation showed that the proposed nanofluid outperformed pure water and slightly higher than Al2O3-H2O in terms of thermal resistance (for Re = 1400, 0.0474, 0.0449 and 0.04647 oK/W for H2O, Al2O3-H2O and Al2O3-NH3(aqu), respectively). However, it exceeds the performance of both pure water and Al2O3-H2O in terms of pressure drop (for Re = 1400, 785288, 911217, 753591 Pa for H2O, Al2O3-H2O and Al2O3-NH3(aqu), respectively). The key findings from the current study may be used to attract more research about the proposed nanofluid to be used in the cooling process of microchannel heat sinks

Design and implementation of fast and highly precise water magnetizer

In the last decades, researchers have widely discussed the effects of magnetized water on many biological and industrial aspects; many studies have also examined the effects of magnetization on water physical and chemical properties and shown a slight increase in the water pH level for the drinking water after magnetizations. This article presents a new practical model to magnetize the tap drinking water with permanent, and adjustable magnets to ensure fast and precise results. A new smart system is designed and implemented to calculate the required magnetic flux density, and the exposuretime based on the difference in the measured pH level of the water atthe inletand outlet pipes.Three permanent magnets, with magnetic flux densities of 500, 1000, and 1500 Gauss (G), are installed at different pipe routes, with added to a variable magnet on the main water outlet. The results show a promising prototype that is not only processing the water efficiently but also supply much data about the water properties, which can be led to more findingsin this field

An Efficient Automatic Mass Classification Method In Digitized Mammograms Using Artificial Neural Network

In this paper we present an efficient computer aided mass classification method in digitized mammograms using Artificial Neural Network (ANN), which performs benign-malignant classification on region of interest (ROI) that contains mass. One of the major mammographic characteristics for mass classification is texture. ANN exploits this important factor to classify the mass into benign or malignant. The statistical textural features used in characterizing the masses are mean, standard deviation, entropy, skewness, kurtosis and uniformity. The main aim of the method is to increase the effectiveness and efficiency of the classification process in an objective manner to reduce the numbers of false-positive of malignancies. Three layers artificial neural network (ANN) with seven features was proposed for classifying the marked regions into benign and malignant and 90.91% sensitivity and 83.87% specificity is achieved that is very much promising compare to the radiologist's sensitivity 75%.Comment: 13 pages, 10 figure

High-Rate Space-Time Coded Large MIMO Systems: Low-Complexity Detection and Channel Estimation

In this paper, we present a low-complexity algorithm for detection in high-rate, non-orthogonal space-time block coded (STBC) large-MIMO systems that achieve high spectral efficiencies of the order of tens of bps/Hz. We also present a training-based iterative detection/channel estimation scheme for such large STBC MIMO systems. Our simulation results show that excellent bit error rate and nearness-to-capacity performance are achieved by the proposed multistage likelihood ascent search (M-LAS) detector in conjunction with the proposed iterative detection/channel estimation scheme at low complexities. The fact that we could show such good results for large STBCs like 16x16 and 32x32 STBCs from Cyclic Division Algebras (CDA) operating at spectral efficiencies in excess of 20 bps/Hz (even after accounting for the overheads meant for pilot based training for channel estimation and turbo coding) establishes the effectiveness of the proposed detector and channel estimator. We decode perfect codes of large dimensions using the proposed detector. With the feasibility of such a low-complexity detection/channel estimation scheme, large-MIMO systems with tens of antennas operating at several tens of bps/Hz spectral efficiencies can become practical, enabling interesting high data rate wireless applications.Comment: v3: Performance/complexity comparison of the proposed scheme with other large-MIMO architectures/detectors has been added (Sec. IV-D). The paper has been accepted for publication in IEEE Journal of Selected Topics in Signal Processing (JSTSP): Spl. Iss. on Managing Complexity in Multiuser MIMO Systems. v2: Section V on Channel Estimation is update

Exploring EFL university learners’ acquisition of advanced reading skills in the Yemeni context

Reading is an essential language skill for enhancing learners’ performance at various levels of study. However, EFL learners at the tertiary level encounter reading difficulties, particularly in acquiring advanced reading skills, which have affected their reading comprehension and resulted in low academic performance achievement. This is probably attributed to various factors, including learners’ lack of effective reading strategies. A study that exclusively explores reading difficulties encountered by EFL university learners, reasons for the difficulties, and strategies adopted to overcome the difficulties and develop advanced reading skills seem to be scarce in the literature. Therefore, the main purpose of this study was to explore the acquisition process of advanced reading skills in EFL tertiary context at a private university in Yemen from learners’ perspective. The study adopted a qualitative approach to gather data from EFL tertiary learners through a focus group discussion. The data were analyzed manually using the indexing approach. Findings revealed that learners face reading difficulties such as inference making, getting the gist of the text, and managing the reading tasks. These difficulties were attributed to linguistic and non-linguistic reasons, and metacognitive, cognitive, and social-affective strategies were used in reading. The study recommends engaging EFL learners in intensive and extensive reading to help them apply the strategies they learn and develop advanced reading skills and better academic performance. Future research studies may focus on strategies for reading fluency

Petrological and Geochemical Analyses and economic potential of some Milestones and Siliceous rocks in northern United Arab Emirates.

Combined microscopic, heavy mineral, X-ray diffraction and chemical analyses have been carried out on the Jurassic limestone, the upper cretaceous Hawasina cherts and the coastal and inland sand dunes in several localities in the Ras Al Khaimah Emirate. The obtained results revealed that a number of represents cherts subfacies; namely: ferruginous radiolarian ribbon chert, carbonaceous radiolarian ribbon chert, colloform ribbon chert, calcareous chert and siliceous mud stone. These rocks consist of (in order of decreasing abundance): quartz, calcite, dolomite and hematite. The carbonate rocks are made up of lime mudstone, wackestone; pack stone and, rarely, crystalline limestone. Various types of wackestone and pack stone were recorded. Mineral1ogically, these limestone consist of calcite and much lesser proportions of quartz and dolomite. Diagenesis greatly modified the original textural and compositional characteristics of the rocks especially the limestone. On the other hand, the light fractions of the coastal sand dunes contain higher concentrations of carbonate lithoclasts and skeletal grains and lower proportions of quartz and chert than those of the inland dunes. Also, the heavy fractions of the former sediments are slightly more enriched in opaques, pyroxenes, epidotes and hornblende while depleted in rutile, tourmaline, garnet and monazite. The obtained geochemical data confirm the presence of the main chert types; namely: (i) radiolarites (R), (ii) calcareous cherts (CC), and (iii) siliceous mudstones(SM). Each type has a homogeneous and characteristics major and trace element confirmed by the increase of Ti02, Al2O3), MgO, Fe203) and HFSE ( High Field Strength Elements). The cherts exhibit LREE (Light Rare Earth Elements) fractionated patterns with moderate negative Eu anomalies. R-mode cluster analysis shows three clusters. The first is for the carbonate minerals the second includes the terrigenous components and the third is the silica cluster. Factor analysis produced a two-factor model, which accounts for 85.85% of the data variability. The first is the terrigenous factor (Ti02,Al2O3) FeO, K20, P205 Rb, Ga, Zr and REE), and the second is the carbonate factor. The majority of the studied limestones and a few of the chert rocks are Compositionally similar to those presently used by the Ras Ai Khaimah Rock Company for cement Production and, consequently can be considered for possible future needs. On the other hand, the compositional characteristics of the dune sands, especially the coastal dunes, do not permit their use as a possible source of silica

Attachment, Emotion Regulation, and ADHD: The Role of the Khadama (Foreign Domestic Worker) in Qatar

198 p.The general aims have been explored across three studies presented in this thesis. The objectives of this thesis were to investigate: a) the relationship between ADHD and emotion regulation, b) attachment security of primary and secondary parental figures as a valid construct in Arabic, c) the relationship between attachment security and emotion regulation strategies and their effects on the symptoms of hyperactivity and inattention problems. Study 1 is a meta-analysis that selected 172 studies based on the relationship between ADHD forms with emotion (dys)regulation strategies considering a broad spectrum of possible manifestations across samples while exploring the effects of different moderators. The meta-analysis demonstrated the general relationship of ADHD with emotion regulation and dysregulation. Study 2 covers the validation in Modern Standard Arabic of an attachment measure to assess attachment to parents and to a secondary figure commonplace in Qatar: the foreign domestic worker (FDW), also known as Khadama. By utilizing the reliable and valid A-IPDWA newly created questionnaire, we will be able to study attachment security to primary parental figures (mother and father) and to secondary attachment figure (i.e., FDW). Finally, Study 3 utilized a mediation analysis to investigate emotion regulation (ER) mediates the relationship between attachment security to primary (mother and father) and secondary parental figures and (hyperactivity and attention problems) in a sample of 286 adolescents studying in schools in Qatar. In Study 3, although there was no mediation of emotion regulation, as initially hypothesized, we found that FDW positively predicted hyperactivity and attention problems, while gender differences in the associations applied. The general findings demonstrated that hyperactivity and attention problems in ADHD relate to emotion regulation strategies and attachment security of primary parental figures and FDWs