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

Low Momentum Classical Mechanics with Effective Quantum Potentials

A recently introduced effective quantum potential theory is studied in a low momentum region of phase space. This low momentum approximation is used to show that the new effective quantum potential induces a space-dependent mass and a smoothed potential both of them constructed from the classical potential. The exact solution of the approximated theory in one spatial dimension is found. The concept of effective transmission and reflection coefficients for effective quantum potentials is proposed and discussed in comparison with an analogous quantum statistical mixture problem. The results are applied to the case of a square barrier.Comment: 4 figure

Contractual Forms in Islamic Finance Law and Islamic Inv. Co. of the Gulf (Bahamas) Ltd. v. Symphony Gems N.V. & Ors.: A First Impression of Islamic Finance

This Article focuses on the case of Islamic Investment Company of the Gulf (Bahamas) Ltd. v. Symphony Gems N.V. & Others (“Symphony Gems”). Symphony Gems is the first instance where a Western court of law ruled on an Islamic financial transaction. Symphony Gems illuminates the challenges and tensions within the industrial complex of Islamic finance as it seeks to exist and thrive in a commercial reality where the regulatory framework and its associated assumptions (both theoretical as well as those of commercial practice) differ markedly from those of Islamic law and the contemporary Islamic financial industry. The resulting transactions often deviate from the classical modes or forms upon which they are supposed to be based. From a conventional finance perspective, Islamic transactions can be criticized as being anomalous, inefficiently structured and obliquely documented. Symphony Gems arose out of the applicability of an Islamic financial contract known as a murabahah. This Article will explain both the conceptual basis and the contemporary usage of the murabahah contract and, more generally, the challenges of integrating Islamic financial concepts into the Anglo-American legal system that predominates the modern global economy. Murabahah contracts, simply stated, involve the sale of an item, through a middleman, in which the ultimate buyer is aware of the middleman\u27s costs in obtaining the item. As discussed later in this Article, murabahah contracts in contemporary practice closely approximate conventional financing mechanisms, particularly the economics underlying a similarly-profiled conventional commercial financing. This is why murabahah contracts are so popular. Therefore, it is not surprising that the first instance in which a Western court of law has examined and opined upon an Islamic financial contract involves a murabahah sale

p-Convex Functions in Discrete Sets

We study the new concept of a p-convex function and A-p-convex sets for somenbsp set A of a vector spacenbsp E. These concepts may have applications in convex and non linear analysis and other topics of mathematical sciences

Hyperbolic Metamaterial Resonator-Antenna Scheme for Large, Broadband Emission Enhancement and Single Photon Collection

We model the broadband enhancement of single-photon emission from color centres in silicon carbide nanocrystals coupled to a planar hyperbolic metamaterial, HMM resonator. The design is based on positioning the single photon emitters within the HMM resonator, made of a dielectric index-matched with silicon-carbide material. The broadband response results from the successive resonance peaks of the lossy Fabry Perot structure modes arising within the high-index HMM cavity. To capture this broadband enhancement in the single photon emitters spontaneous emission, we placed a simple gold based cylindrical antenna on top of the HMM resonator. We analyzed the performance of this HMM coupled antenna structure in terms of the Purcell enhancement, quantum efficiency, collection efficiency and overall collected photon rate. For perpendicular dipole orientation relative to the interface, the HMM coupled antenna resonator leads to a significantly large spontaneous emission enhancement with Purcell factor of the order of 250 along with a very high average total collected photon rate, CPR of about 30 over a broad emission spectrum, 700 nm to 1000 nm. The peak CPR increases to about 80 at 900 nm, corresponding to the emission of silicon-carbide quantum emitters. This is a state of the art improvement considering the previous computational designs have reported a maximum average CPR of 25 across the nitrogen-vacancy centre emission spectrum, 600 nm to 800 nm with the highest value being about 40 at 650 nm

Do blind persons have better audiometric hearing threshold values than sighted persons? A pair-matching analysis

Objective: This study aimed to report difference in audiometric hearing threshold values between blind and sighted persons.Methods: This was a comparative cross-sectional study of blind and normally sighted students hearing thresholds. Two groups were formed experimental and control groups respectively, matched for age only. Audiometric threshold hearing values were obtained using an Audiometer in accordance with the modified Hughson-Westlake technique at frequencies of 0.5 to 4 kHz. The Pure Tone Average is the average value at these frequencies for the better ear.Results: Each group had 23 participants, mean threshold values for blind group was 17.45dB (95%CI: 16.59 - 18.30dB); while for the sighted group is 17.59dB (95%CI: 15.90 - 19.28dB). Overall, tests did not reveal a statistical significance  even though normal sighted students had higher threshold values.Conclusion: The study did not reveal a difference between audiometric threshold values between sighted and blind persons.Keywords: Blind, sighted, audiometric values, differenc

Towards a virtual research environment for paediatric endocrinology across Europe

Paediatric endocrinology is a medical specialty dealing with variations of physical growth and sexual development in childhood. Genetic anomalies that can cause disorders of sexual development in children are rare. Given this, sharing and collaboration on the small number of cases that occur is needed by clinical experts in the field. The EU-funded EuroDSD project (www.eurodsd.eu) is one such collaboration involving clinical centres and clinical and genetic experts across Europe. Through the establishment of a virtual research environment (VRE) supporting sharing of data and a variety of clinical and bioinformatics analysis tools, EuroDSD aims to provide a research infrastructure for research into disorders of sex development. Security, ethics and information governance are at the heart of this infrastructure. This paper describes the infrastructure that is being built and the inherent challenges in security, availability and dependability that must be overcome for the enterprise to succeed

A New Monte Carlo Based Algorithm for the Gaussian Process Classification Problem

Gaussian process is a very promising novel technology that has been applied to both the regression problem and the classification problem. While for the regression problem it yields simple exact solutions, this is not the case for the classification problem, because we encounter intractable integrals. In this paper we develop a new derivation that transforms the problem into that of evaluating the ratio of multivariate Gaussian orthant integrals. Moreover, we develop a new Monte Carlo procedure that evaluates these integrals. It is based on some aspects of bootstrap sampling and acceptancerejection. The proposed approach has beneficial properties compared to the existing Markov Chain Monte Carlo approach, such as simplicity, reliability, and speed