On polarization characteristics of highly focused fields concentrated along the axis

After having proven that an uncertainty relation holds for the on-axis power content of highlyfocused fields, in this Communication we explore and discuss the consequences of such a relation concerning the polarization state characterizing the fields that satisfy it.

Injection Coding with Spectral Nulls for Even Codeword Lengths

With a view to adapting information signals to suit the frequency characteristics of digital transmission channels, it is pertinent to design channel coding schemes that can exhibit spectral shaping capabilities after being processed with a suitable modulation technique. This involves concentrating the frequency energy of the coded and modulated information signal towards a predetermined range of the frequency spectrum, or making it have low power content at such frequencies. One modulation scheme that is suitable for achieving this is pulse amplitude modulation (PAM). We thus present a permutation coding (PC) system with injections that can exhibit spectral nulls at rational sub-multiples of the symbol frequency. Such injections are achieved by strategically removing δ columns from the source PC. We also present a mathematical expression that allows for the prediction of zero energy positions in the codebook’s spectrum. Due to the way the injections are introduced, it gives the scheme an advantage of achieving higher symbol rate, when compared with conventional PC systems. The work is however limited to cases where δ =2 and the lengths of the codewords involved are even numbers.

Comparison of wavelet continuous transform and signal averaged ECG for high frequency content and late potential detection in healthy individuals

Introduction The Signal Averaged ECG (SAECG) is a classical method forSudden Cardiac Death (SCD) risk assessment, by means of Late Potentials (LP) in the filtered QRS (fQRS)[1]. But it is highly dependent on noise and require long time records, which make it tedious to use. Wavelet Continuous Transform (WCT) meanwhile is easier to use, and may let us to measure the High Frequency Content (HFC) of the QRS and QT intervals, which also correlates with the risk of SCD [2,3]. Whether the HFC of the QRS and QT measured with the WCT is a possible subrogate of LP, has never been demonstrated. Objective To demonstrate if there is any relationship between the HFC measured with the WCT and the LP analyzed with the SAECG. Methods Data from 50 consecutive healthy individuals. The standard ECG was digitally collected for 3 consecutive minutes. For the WCT Analysis 8 consecutive QT complexes were used and for the SAECG Analysis all available QRS were used. The time-frequency data of each QT complex were collected using the WCT as previously described [3] and the Total, QRS and QT power were obtained from each patient. For the SAECG, bipolar X, Y and Z leads were used with a bidirectional filter at 40 to 250 Hz [1]. LP were defined as less than 0.05 z in the terminal part of the filtered QRS and the duration (SAECG LP duration) and root mean square (SAECG LP Content) of this LP were calculated. Pearson's test was used to correlate the Power content with WCT analysis and the LP in the SAECG. Results There is a strong correlation between Total Power and the SAECG LP content (r=0.621, p<0.001). Both ST Power (r=0.567, p<0.001) and QRS Power (r=0.404, p=0.004) are related with the SAECG LP content. No correlation were found between the Power content (Total, QRS or ST Power) and the SAECG LP duration. Also no correlation was found between de SAECG LP content and duration. Conclusions Total, QRS and ST Power measured with the WCT are good surrogates of SAECG LP content. No correlation were found between WCT analysis and the SAECG LP duration. Also no correlation was found between the SAECG LP content and duration. This can be of high interest, since WCT is an easier technique, not needing long recordings and being less affected by noise. Funding Acknowledgement Type of funding source: None

Artefacts of circumpolar cartography in radio pulsar polarization

ABSTRACT Single-pulse data on radio pulsar polarization are traditionally presented in the form of two-dimensional grey-scale patterns with the pulse longitude and polarization angle (PA) on the horizontal and vertical axis, respectively. Such diagrams reveal several enigmatic polarization effects: (1) bifurcations and loops of PA curve under central pulse components, (2) vertical spread of flux at all PA values, (3) exchange of power content between PA tracks of two orthogonal polarization modes (OPMs), and (4) peripherically flat PA swings that span more than 180 deg. It is shown that all these phenomena result from passage of observed polarization state near the pure-V pole of Poincaré sphere. Much of their complexity results from cartographic transformation from Poincaré sphere to the longitude–PA plane. An odd number of near-pole passages produce apparent replacement of OPM power in the profile wings, although the same amount of flux keeps staying in each modal patch on the Poincaré sphere. The fitting of pulsar PA curves should therefore allow for transitions between the primary (strong) and secondary (weak) PA tracks. The Stokes space (or Poincaré sphere) representation of pulsar polarization data contains crucial polarization information and needs to accompany the traditional viewing if the published figures are to be fully useful for interpretation.

Construction and validation of a knowledge, attitudes and practices scale related to sustainability in university students

PurposeThe objective of this study was to build and validate a scale to analyze the knowledge, attitudes and practices on the sustainability of university students.Design/methodology/approachPsychometric validation was carried out using the criteria of internal consistency, reliability, discriminant power, content validity and predictive validity.FindingsThe KAP scale designed in this study demonstrated excellent psychometric properties and is apt for evaluating knowledge, attitudes and practices in university students.Originality/valueTransitions toward sustainability require changes in knowledge, attitudes and practices (KAP) related to sustainability, making it necessary to have tools that support educational interventions for sustainability that tend toward a generation of changes in the decisions and behavior of people. In that sense, a KAP scale can be a useful tool to support these interventions. However, studies that use validated scales are scarce.

Comparative Assessment of Savonius Water Turbine With Conventional Savonius Wind Turbine

Wind turbine has gained a keen interest in the field of research but its low efficiency due to low working fluid density triggers the need for upgradation. However, this technology will get a boost if the factor of low density fluid is eradicated. This paper is intended towards the study of performance of the same design of Savonius wind turbine when operated in high density water. The density of water is approximately 1000 times more than air. In the present study, the performance of a two bladed Savonius wind turbine and a Savonius water turbine have been analyzed both experimentally and with the aid of Computational Fluid Dynamics (CFD) using Ansys 19.0, keeping the maximum power content (Pmax) of the fluid-stream constant. Coefficient of power (Cp) is one of the deciding factors for superiority of the turbines one over the other. For the study, three cases of power contents viz. 0.61 W, 6.2 W and 16.45 W have been considered. The results obtained suggest that the Savonius water turbine with the highest Cp value of 0.343 is dominant over Savonius wind turbine. The effects of tip speed ratio and Non-dimensional factor (γ) on performance of both the turbine kinds have also been studied.