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Buyukcekmece, Turkey

Osman O.,Istanbul Arel University
IET Microwaves, Antennas and Propagation

In this study, variable active antenna spatial modulation (VASM) technique, which allows the selection of any number of antennas (but not a constant number of active antennas) to transmit a symbol at the same signalling interval, is presented. In the first step of the development of VASM, antenna selection method is determined to use the minimum number of transmit antennas. Complexity analysis of maximum likelihood decoder is given for the new scheme. In the second step, to reduce the correlation effect, a novel antenna selection method called VASM improved (VASMi) that minimises the pairwise error probability is introduced for exponentially correlated channels. For 6, 8, and 10 bit/s/Hz spectral efficiencies, bit error rates are obtained and compared with spatial modulation (SM) and generalised SM (GSM) for different antenna and signal constellation configurations. VASMi outperforms SM and GSM in both uncorrelated and exponentially correlated multiple-input multiple-output channels for similar antenna configurations. © The Institution of Engineering and Technology 2015. Source

Guney E.,Istanbul Arel University | Aras N.,Istanbul University | Altnel I.K.,Istanbul University | Ersoy C.,Istanbul University
Computers and Operations Research

Sensors are tiny electronic devices having limited battery energy and capability for sensing, data processing and communicating. They can collectively behave to provide an effective wireless network that monitors a region and transmits the collected information to gateway nodes called sinks. Most of the applications require the operation of the network for long periods of times, which makes the efficient management of the available energy resources an important concern. There are three major issues in the design of sensor networks: sensor deployment or the coverage of the sensing area, sink location, and data routing. In this work, we consider these three design problems within a unified framework and develop two mixed-integer linear programming formulations. They are difficult to solve exactly. However, it is possible to compute good feasible solutions of the sink location and routing problems easily, when the sensors are deployed and their locations in the sensor field become known. Therefore, we propose a tabu search heuristic that tries to identify the best sensor locations satisfying the coverage requirements. The objective value corresponding to each set of sensor locations is calculated by solving the sink location and routing problem. Computational tests carried out on randomly generated test instances indicate that the proposed hybrid approach is both accurate and efficient. © 2011 Elsevier Ltd. All rights reserved. Source

Berk C.,Istanbul Arel University
International Journal of Energy Economics and Policy

Brent crude and West Texas intermediate (WTI) are major indices for purchases of oil worldwide among with some others such as OPEC basket. Brent is traditionally a European index whereas WTI representing slightly sweeter and lighter crude is more applicable in USA. Until 2010, the spread between WTI and Brent hasn’t been more than few dollars. However in recent years, the spread is widening in favor of Brent and then returning to the mean. WTI which historically taken over Brent, has fallen below Brent which is now claimed to be the global oil index for the World. This is sometimes argued with the Shale production and over-supply in the U.S. and several macroeconomic events such as Libyan crisis. The aim of this paper is to analyze which of these indices is a better indicator for the energy industry. The variables from NYSE exchange traded funds namely energy select sector SPDR ETF (XLE), Teucrium WTI crude oil ETF (CRUD), and United States Brent oil ETF (BNO) for the period December 1994 and September 2014. The variables are analyzed for long-run and short-run relationships with unit root tests, vector autoregression models, and vector error correction models as well as cointegration and Granger causality tests. © 2016, Econjournals. All rights reserved. Source

With the increasing importance given to smart grid solutions in end-user premises, demand response (DR) strategies applied to smart households are important topics from both real time application and academic theoretic analysis perspectives, recently. In this study, a mixed-integer linear programming (MILP) framework based evaluation of such a smart household is provided. Electric vehicles (EVs) with bi-directional power flow capability via charging and V2H operating modes, energy storage systems (ESSs) with peak clipping and valley filling opportunity and a small scale distributed generation (DG) unit enabling energy sell back to grid are all considered in the evaluated smart household structure. Different case studies including also different DR strategies based on dynamic pricing and peak power limiting are conducted to evaluate the technical and economic impacts of ESS and DG units. Besides, shiftable loads such as washing machine and dishwasher are also considered in Home Energy Management (HEM) system structure for the effective operation of the household. Moreover, a further sensitivity analysis is realized in order to discuss the impact of ESS and DG sizing on daily cost of smart household operation considering further pros and cons. © 2014 Elsevier Ltd. Source

Idiopathic absence epilepsies (IAE), that have high prevalence particularly among children and adolescents, are complex disorders mainly caused by genetic factors. Childhood absence epilepsy and juvenile absence epilepsy are among the most common subtypes of IAEs. While the role of ion channels has been the primary focus of epilepsy research, the analysis of mutation and association in both patients with absence epilepsies and animal models revealed the involvement of GABA receptors and calcium channels, but also of novel non-ion channel proteins in inducing spike wave discharges (SWD). Functional studies on a mutated variant of these proteins also support their role in the epileptogenesis of absence seizures. Studies in animal models point to both the thalamus and cortex as the origin of SWDs: the abnormalities in the components of these circuits leading to seizure activity. This review examines the current research on mutations and susceptibility alleles determined in the genes that code for the subunits of GABA receptors (GABRG2, GABRA1, GABRB3, GABRA5, GABA (B1) and GABA (B2)), calcium channels (CACNA1A, CACNA1G, CACNA1H, CACNA1I, CACNAB4, CACNAG2 and CACNG3), and novel non-ion channel proteins, taking into account the results of functional studies on these variants. © 2011 British Epilepsy Association. Source

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