Optimal Detector Randomization in Cognitive Radio Systems in the Presence of Imperfect Sensing Decisions

Cataloged from PDF version of article.In this study, optimal detector randomization is developed for secondary users in a cognitive radio system in the presence of imperfect spectrum sensing decisions. It is shown that the minimum average probability of error can be achieved by employing no more than four maximum a-posteriori probability (MAP) detectors at the secondary receiver. Optimal MAP detectors and generic expressions for their average probability of error are derived in the presence of possible sensing errors. Also, sufficient conditions are presented related to improvements due to optimal detector randomization. © 2014 IEEE

Optimum Power Allocation for Average Power Constrained Jammers in the Presense of Non-Gaussian Noise

Cataloged from PDF version of article.We study the problem of determining the optimum power allocation policy for an average power constrained jammer operating over an arbitrary additive noise channel, where the aim is to minimize the detection probability of an instantaneously and fully adaptive receiver employing the Neyman-Pearson (NP) criterion. We show that the optimum jamming performance can be achieved via power randomization between at most two different power levels. We also provide sufficient conditions for the improvability and nonimprovability of the jamming performance via power randomization in comparison to a fixed power jamming scheme. Numerical examples are presented to illustrate theoretical results

The solid effect of dynamic nuclear polarization in liquids – accounting for <i>g</i>-tensor anisotropy at high magnetic fields

In spite of its name, the solid effect of dynamic nuclear polarization (DNP) is also operative in viscous liquids, where the dipolar interaction between the polarized nuclear spins and the polarizing electrons is not completely averaged out by molecular diffusion on the timescale of the electronic spin–spin relaxation time. Under such slow-motional conditions, it is likely that the tumbling of the polarizing agent is similarly too slow to efficiently average the anisotropies of its magnetic tensors on the timescale of the electronic T2. Here we extend our previous analysis of the solid effect in liquids to account for the effect of g-tensor anisotropy at high magnetic fields. Building directly on the mathematical treatment of slow tumbling in electron spin resonance (Freed et al., 1971), we calculate solid-effect DNP enhancements in the presence of both translational diffusion of the liquid molecules and rotational diffusion of the polarizing agent. To illustrate the formalism, we analyze high-field (9.4 T) DNP enhancement profiles from nitroxide-labeled lipids in fluid lipid bilayers. By properly accounting for power broadening and motional broadening, we successfully decompose the measured DNP enhancements into their separate contributions from the solid and Overhauser effects.</p

Carbon and proton Overhauser DNP from MD simulations and ab initio calculations: TEMPOL in acetone

This journal is © the Owner Societies 2015. A computational analysis of the Overhauser effect is reported for the proton, methyl carbon, and carbonyl carbon nuclei of liquid acetone doped with the nitroxide radical TEMPOL. A practical methodology for calculating the dynamic nuclear polarization (DNP) coupling factors by accounting for both dipole-dipole and Fermi-contact interactions is presented. The contribution to the dipolar spectral density function of nuclear spins that are not too far from TEMPOL is computed through classical molecular dynamics (MD) simulations, whereas the contribution of distant spins is included analytically. Fermi contacts are obtained by subjecting a few molecules from every MD snapshot to ab initio quantum mechanical calculations. Scalar interaction is found to be an essential part of the 13C Overhauser DNP. While mostly detrimental to the carbonyl carbon of acetone it is predicted to result in large enhancements of the methyl carbon signal at magnetic fields of 9 T and beyond. In contrast, scalar coupling is shown to be negligible for the protons of acetone. The additional influence of proton polarization on the carbon DNP (three-spin effect) is also analyzed computationally. Its effect, however, is concluded to be practically insignificant for liquid acetone

Intercultural communicative competence in ELT

Bu çalışma, 02-05 Şubat 2012 tarihleri arasında Barcelona[İspanya]’da düzenlenen 4. World Conference on Educational Sciences (WCES)’da bildiri olarak sunulmuştur.Based on a critical review of selected relevant studies and with a historical perspective, this discussion paper, as a piece of secondary research (Nunan, 1992, p. 8), aimed to point out where the world of language teaching is in terms of the competences that learners are expected to gain. It was determined that intercultural communicative competence, i.e. the knowledge, motivation and skills needed to interact effectively and appropriately with members of different cultures (Wiseman, 2002, p. 208), is currently the highly favored type of competence after the sequential dominance of grammatical (linguistic) competence and communicative competence. The major inference drawn from the review was that although a number of particular studies draw heavily on intercultural communicative competence, they are paradoxical or not clear about where and how they differ from the tenets of its much-criticized predecessor, i.e. communicative language teaching, and about whose culture is to be taught along with the language. Taking sides for a pedagogical philosophy predicated on intercultural communicative competence, the author concludes that this is still merely a set of beliefs and procedures in need of multidisciplinary research-driven clarification and maturation and in this respect, he refers to and discusses some fundamental principles and standpoints on which a new model based on intercultural communicative competence can be built.Acad World Educ & Res CtrNear E UniversityCyprus Educ Sci AssocBahçeşehir ÜniversitesiAnkara ÜniversitesiHacettepe Üniversites

The internet and computer-mediated artefacts for foreign language learning and practice, and intercultural communication: MOODLE, second life, and others

Bu çalışma, 02-05 Şubat 2012 tarihleri arasında Barcelona[İspanya]’da düzenlenen 4th World Conference on Educational Sciences (WCES)’da bildiri olarak sunulmuştur.The present study aims at discussing the potential of the Internet and computer-mediated artefacts for education. The understanding of digitalised and technology utilised education, which is the current trend of our age, is highlighted and some computer-mediated artefacts such as the so called modular object-oriented dynamic learning environment (MOODLE), the online virtual reality chatting game Second Life, and some others are introduced in a unified connection to show how they can be practically integrated in education, and how they can foster foreign language learning and practice, and intercultural communication. It is emphasised that the current situation of the physical conditions, and also the needs, interests and abilities of the new age learners should be considered more carefully to give education a correct direction in the future.Acad World Educ & Res CtrNear E UnivCyprus Educ Sci AssocBahçeşehir ÜniversitesiAnkara ÜniversitesiHacettepe Üniversites

Density functional theory studies of MTSL nitroxide side chain conformations attached to an activation loop

A quantum-mechanical (QM) method rooted on density functional theory (DFT) linked to the Stochastic Liouville equation (SLE) in the Fokker Planck (FP) form has been employed for the first time to sample the methane-thiosulfonate spin label (MTSL) conformational space attached to the Aurora-A kinase activation loop and to calculate the EPR spectrum. The features of the calculated energy surface allowed us to describe the system in a limited number of rotamers stabilized by interactions of the MTSL side chain and neighbouring residues. The relevant magnetic parameters and the electron paramagnetic resonance (EPR) spectrum were subsequently calculated from the trajectories of the spin probe in the protein environment. The comparison between theoretical and experimental continuous wave (CW) EPR spectra revealed some small differences in the EPR line shape which arises from the combinations of g- and A-values obtained from the conformations selected. The theoretical approach adopted in this work can be used to recognise the contribution of MTSL rotamers to the EPR spectrum in order to help extract structural/dynamics properties of protein from the experimental data

Pushing the mass limit for intact launch and photoionization of large neutral biopolymers

Since their first discovery by Louis Dunoyer and Otto Stern, molecular beams have conquered research and technology. However, it has remained an outstanding challenge to isolate and photoionize beams of massive neutral polypeptides. Here we show that femtosecond desorption from a matrix-free sample in high vacuum can produce biomolecular beams at least 25 times more efficiently than nanosecond techniques. While it has also been difficult to photoionize large biomolecules, we find that tailored structures with an abundant exposure of tryptophan residues at their surface can be ionized by vacuum ultraviolet light. The combination of these desorption and ionization techniques allows us to observe molecular beams of neutral polypeptides with a mass exceeding 20,000 amu. They are composed of 50 amino acids – 25 tryptophan and 25 lysine residues – and 26 fluorinated alkyl chains. The tools presented here offer a basis for the preparation, control and detection of polypeptide beams