Darwin\u27s Radio Telescope: Use of Genetic Algorithms in the Optimization of Patch Antennas for Radio Astronomy

Radio Astronomy refers to astronomical observation in the radio band of the electromagnetic spectrum and is used by astrophysicists and astronomers to observe parts of the Universe outside of the visible spectrum. Through the use of radio telescopes, astronomers and astrophysicists are able to observe relatively dark or cold parts of the Universe that are not active within the visible spectrum. The specific event used within this research to observe these areas of cold matter is the 21cm wavelength emission from neutral hydrogen (the H-I line emission). This relatively low energy event allows astronomers to see large gas clouds that would normally be invisible. Radio telescopes are traditionally built out of large dish antenna arrays due to their high resolution and high gain but can be prohibitively expensive and require a great deal of upkeep. This research focused on using genetic algorithms to optimize a phased array of patch antennas that can add an aspect of versatility and robustness to the radio telescope design that is not provided by a dish antenna radio telescope. Genetic algorithms are a method of design optimization for specific desired outcomes when the relationship between design parameters and effective outcome parameters are not well defined and therefore may result in a non-intuitive optimal design. This method uses the basic rules of evolution in repeated design simulations by rewarding traits that promote a desired effect. In this research, the genetic algorithm controls the spacing and relative weighting of a 2-D array structure for a phased patch antenna array. While the patch antenna does not have the intrinsic properties required for radio astronomy, they can be combined and optimized as a 2-D array structure that provides all the necessary functions of a radio telescope and contains the added benefit of low maintenance and wider viewing angles

Augmented GNSS Differential Corrections Minimum Mean Square Error Estimation Sensitivity to Spatial Correlation Modeling Errors

Railway signaling is a safety system that has evolved over the last couple of centuries towards autonomous functionality. Recently, great effort is being devoted inthis field, towards the use and exploitation of Global Navigation Satellite System (GNSS)signals and GNSS augmentation systems in view of lower railway track equipments andmaintenance costs, that is a priority to sustain the investments for modernizing the local andregional lines most of which lack automatic train protection systems and are still manuallyoperated. The objective of this paper is to assess the sensitivity of the Linear Minimum MeanSquare Error (LMMSE) algorithm to modeling errors in the spatial correlation function thatcharacterizes true pseudorange Differential Corrections (DCs). This study is inspired bythe railway application; however, it applies to all transportation systems, including the roadsector, that need to be complemented by an augmentation system in order to deliver accurateand reliable positioning with integrity specifications. A vector of noisy pseudorange DCmeasurements are simulated, assuming a Gauss-Markov model with a decay rate parameterinversely proportional to the correlation distance that exists between two points of a certainenvironment. The LMMSE algorithm is applied on this vector to estimate the true DC, andthe estimation error is compared to the noise added during simulation. The results show thatfor large enough correlation distance to Reference Stations (RSs) distance separation ratiovalues, the LMMSE brings considerable advantage in terms of estimation error accuracy and precision. Conversely, the LMMSE algorithm may deteriorate the quality of the DCmeasurements whenever the ratio falls below a certain threshold

CFL’S CYCLE AS A METHOD OF RELIABILITY DETERMINATION AND PREMATURE DISPOSAL

En este trabajo se muestran los resultados del ciclado de una población de 86 lámparas. 82 de bajo consumo y 4 incandescentes. Las mismas han sido sometidas a las condiciones consideradas más perjudiciales para este tipo de dispositivos. Así, se definieron ciclos de funcionamiento nocturno, de 8 a 12 horas de duración, con periodos de operación de 30 minutos y de 2 minutos de reposo. Esto, presupone un número de conmutaciones fuera del estándar admitido y condiciones de operación desfavorables.This paper shows the results of the cycling of a population of 86 lamps. 82 low-power and 4 incandescent. They have been subjected to more adverse conditions considered for these devices. By this way, night cycles of operation were defined, from 8 to 12 hours, with operation periods of 30 min. and 2 min. standing. This presupposes a number of non-standard switches admitted and unfavorable operating conditions

Diagnostic and therapeutic aspects of hemiplegic migraine

Hemiplegic migraine (HM) is a clinically and genetically heterogeneous condition with attacks of headache and motor weakness which may be associated with impaired consciousness, cerebellar ataxia and intellectual disability. Motor symptoms usually last <72 hours and are associated with visual or sensory manifestations, speech impairment or brainstem aura. HM can occur as a sporadic HM or familiar HM with an autosomal dominant mode of inheritance. Mutations in CACNA1A, ATP1A2 and SCN1A encoding proteins involved in ion transport are implicated. The pathophysiology of HM is close to the process of typical migraine with aura, but appearing with a lower threshold and more severity. We reviewed epidemiology, clinical presentation, diagnostic assessment, differential diagnosis and treatment of HM to offer the best evidence of this rare condition. The differential diagnosis of HM is broad, including other types of migraine and any condition that can cause transitory neurological signs and symptoms. Neuroimaging, cerebrospinal fluid analysis and electroencephalography are useful, but the diagnosis is clinical with a genetic confirmation. The management relies on the control of triggering factors and even hospitalisation in case of long-lasting auras. As HM is a rare condition, there are no randomised controlled trials, but the evidence for the treatment comes from small studies

Exospheric Na distributions along the Mercury orbit with the THEMIS telescope

Abstract The Na exosphere of Mercury is characterized by the variability of the emission lines intensity and of its distribution in time scales from less than one hour to seasonal variations. While the faster variations, accounting for about 10–20% of fluctuations are probably linked to the planetary response to solar wind and Interplanetary Magnetic Field variability, the seasonal variations (up to about 80%) should be explained by complex mechanisms involving different surface release processes, loss, source and migrations of the exospheric Na atoms. Eventually, a Na annual cycle can be identified. In the past, ground-based observations and equatorial density from MESSENGER data have been analyzed. In this study, for a more extensive investigation of the exospheric Na features, we have studied the local time and latitudinal distributions of the exospheric Na column density as a function of the True Anomaly Angle (TAA) of Mercury by means of the extended dataset of images, collected from 2009 to 2013, by the THEMIS solar telescope. Our results show that the THEMIS images, in agreement with previous results, registered a strong general increase in sodium abundance at aphelion and a dawn ward emission predominance with respect to dusk ward and subsolar region between 90° and 150° TAA. This behavior can be explained by desorption of a sodium surface reservoir consisting of sodium that is pushed anti-sunward and condenses preferentially in the coldest regions. Our analyses show s a predominance of subsolar line-of-sight column density along the rest of Mercury's orbit. An unexpected relationship between Northward or Southward peak emission and both TAA and local time is also shown by our analysis. This result seems to contradict previous results obtained from different data sets and it is not easily explained, thus it requires further investigations

Detection of Nitroaromatic Explosives in Air by Amino-Functionalized Carbon Nanotubes

Nitroaromatic explosives are the most common explosives, and their detection is important to public security, human health, and environmental protection. In particular, the detection of solid explosives through directly revealing the presence of their vapors in air would be desirable for compact and portable devices. In this study, amino-functionalized carbon nanotubes were used to produce resistive sensors to detect nitroaromatic explosives by interaction with their vapors. Devices formed by carbon nanotube networks working at room temperature revealed trinitrotoluene, one of the most common nitroaromatic explosives, and di-nitrotoluene-saturated vapors, with reaction and recovery times of a few and tens of seconds, respectively. This type of resistive device is particularly simple and may be easily combined with low-power electronics for preparing portable devices

Deuterium retention and erosion in liquid Sn samples exposed to D2 and Ar plasmas in GyM device

The use of tin (Sn) as a liquid metal for plasma facing components has been recently proposed as a solution to the high heat load issue on the divertor target plates in nuclear fusion reactors. Due to its low vapor pressure, low reactivity with hydrogen and good resilience to neutron impact, tin is a good candidate as plasma facing component. However its high atomic number poses concerns about plasma contamination.In this paper two fundamental aspects have been investigated: deuterium retention and erosion fluxes from the Sn surface towards the plasma. The samples were exposed to plasma inside the linear machine GyM in magnetic cusp configuration. This setup permits to expose free liquid specimens without the need for the Capillary Porous System. Moreover it permits to lower the magnetic field in order to increase Sn Larmor radius and consequently limit Sn re-deposition in erosion experiments.Ex-situ analyses by ion beam diagnostics on solid samples exposed to deuterium plasma have proved that the amount of retained atomic deuterium is very low, approximately 0.18 at% estimated by Nuclear Reaction Analysis and 0.25 at% estimated by Elastic Recoil Detection Analysis.In the framework of erosion studies, the spectroscopic parameter S/XB was evaluated in Ar plasma for the SnI line at 380.1 nm by Optical Emission Spectroscopy and mass loss measurements in the 5–11 eV Te range, at a density ne ∼ 1.5 × 1011 cm−3. An average value of 150 ± 23 was obtained. Keywords: Liquid metals, Deuterium retention, Erosion, Double-cusp magnetic configuration, Ion beam diagnostics, S/XB spectroscopic paramete