7,608 research outputs found
28 GHz Taylor Feed Network for Sidelobe Level Reduction in 5G Phased Array Antennas
This paper presents a design procedure for a phased array feed network. The procedure is validated by designing and fabricating a set of 28âGHz 8âelement beam steerable antennas. Within the feed, a Taylor nâbar amplitude taper is implemented using unequal power dividers. At boresight, the taper reduced the sidelobe level by 2.84âdB to â15.2 dB. Beam steering from 0° to 48° is achieved using meanders. An empirical formula for the meander widths is proposed, enabling independent control of amplitude and phase. Empirical formulae for the initial parameters of the unequal dividers are also proposed. The wide transmission lines in this feed network are compatible with lowâcost PCB fabrication techniques
Effects of sunlight on bacteriophage viability and structure
Current estimates of viral abundance in natural waters rely on direct counts of virus-like particles (VLPs), using either transmission or epifluorescence microscopy. Direct counts of VLPs, while useful in studies of viral ecology, do not indicate whether the observed VLPs are capable of infection and/or replication. Rapid decay in bacteriophage viability under environmental conditions has been observed. However, it has not been firmly established whether there is a corresponding degradation of the virus particles, To address this question, viable and direct counts were carried out employing two Chesapeake Bay bacteriophages in experimental microcosms incubated for 56 h at two depths in the York River estuary, Viruses incubated in situ in microcosms at the surface yielded decay rates in full sunlight of 0.11 and 0.06 h(-1) for CB 38 Phi, and CB 7 Phi, respectively, The number of infective particles in microcosms in the dark and at a depth of 1 m was not significantly different from laboratory controls, with decay rates averaging 0.052 h(-1) for CB 38 Phi and 0.037 h(-1) for CB 7 Phi. Direct counts of bacteriophages decreased in the estuarine microcosms, albeit only at a rate of 0.028 h(-1), and were independent of treatment, Destruction of virus particles is concluded to be a process separate from loss of infectivity, It is also concluded that strong sunlight affects the viability of bacteriophages in surface waters, with the result that direct counts of VLPs overestimate the number of bacteriophage capable of both infection and replication, However, in deeper waters, where solar radiation is not a significant factor, direct counts should more accurately estimate numbers of viable bacteriophage
Cascaded Fresnel Lens Antenna for Scan Loss Mitigation in Millimeter-Wave Access Points
Millimeter wave lens antennas will be essential for future wireless access. Conventionally, they increase the gain in the boresight direction only. In this paper, cascaded Fresnel zone plate lenses are combined with a phased array to increase the gain at wide steering angles of ±52°. The side lenses are tilted to align with the maximum steering angle, and cascaded to increase the focusing gain. The inner lenses increase the gain by 2.45 dB at boresight, and by 3.19 dB at the maximum steering angle. When the side lenses are repositioned, the simulated focusing gain increases to 4.69 dB. Asymmetric amplitude distributions are proposed to prevent the main lobe from splitting. An 8-dement 7-lens prototype operating at 28 GHz achieved a gain from 12.96 dBi to 15.35 dBi with a bandwidth of at least 1.3 GHz for all measured beam directions. The maximum measured azimuthal beamwidth was 27°. A design procedure and a theoretical analysis of diffraction through the lenses are provided. By increasing the SNR, this beamfonning antenna could improve the coverage of 3-sector 5G microcell base stations, and support gigabit wireless links for vehicular, rail, and satellite communications
Conformal Transmitarray for Scan Loss Mitigation with Thinned Reconfiguration
A conformal transmitarray with thinned control is
presented, operating at 28 GHz. Its side panels are rotated to
align with the maximum steering angle, increasing the gain
and reducing the scan loss. The transmitarray is fed by an
8-element linear phased array antenna. Beam focusing to +/-
53 degrees is demonstrated for two different directions, using
combinations of crossed-slot unit cells. A unit cell placement rule
is proposed to significantly reduce (i.e. thin) the required number
of reconfigurable unit cells. A filling factor of 43% was achieved
compared to a fully populated design. This reduces the cost and
biasing complexity. By minimising scan loss, this antenna could
improve the performance of 5G small-cell access points
Continuity of Local Time: An applied perspective
Continuity of local time for Brownian motion ranks among the most notable
mathematical results in the theory of stochastic processes. This article
addresses its implications from the point of view of applications. In
particular an extension of previous results on an explicit role of continuity
of (natural) local time is obtained for applications to recent classes of
problems in physics, biology and finance involving discontinuities in a
dispersion coefficient. The main theorem and its corollary provide physical
principles that relate macro scale continuity of deterministic quantities to
micro scale continuity of the (stochastic) local time.Comment: To appear in: "The fascination of Probability, Statistics and Their
Applications. In honour of Ole E. Barndorff-Nielsen on his 80th birthday
Feasibility of smartphone colorimetry of the face as an anaemia screening tool for infants and young children in Ghana
Background Anaemia affects approximately a quarter of the global population. When anaemia occurs during childhood, it can increase susceptibility to infectious diseases and impair cognitive development. This research uses smartphone-based colorimetry to develop a non-invasive technique for screening for anaemia in a previously understudied population of infants and young children in Ghana. Methods We propose a colorimetric algorithm for screening for anaemia which uses a novel combination of three regions of interest: the lower eyelid (palpebral conjunctiva), the sclera, and the mucosal membrane adjacent to the lower lip. These regions are chosen to have minimal skin pigmentation occluding the blood chromaticity. As part of the algorithm development, different methods were compared for (1) accounting for varying ambient lighting, and (2) choosing a chromaticity metric for each region of interest. In comparison to some prior work, no specialist hardware (such as a colour reference card) is required for image acquisition. Results Sixty-two patients under 4 years of age were recruited as a convenience clinical sample in Korle Bu Teaching Hospital, Ghana. Forty-three of these had quality images for all regions of interest. Using a naĂŻve Bayes classifier, this method was capable of screening for anaemia (<11.0g/dL haemoglobin concentration) vs healthy blood haemoglobin concentration (â„11.0g/dL) with a sensitivity of 92.9% (95% CI 66.1% to 99.8%), a specificity of 89.7% (72.7% to 97.8%) when acting on unseen data, using only an affordable smartphone and no additional hardware. Conclusion These results add to the body of evidence suggesting that smartphone colorimetry is likely to be a useful tool for making anaemia screening more widely available. However, there remains no consensus on the optimal method for image preprocessing or feature extraction, especially across diverse patient populations
The secret of success
Parts of Antarctica have experienced warming almost an order of magnitude greater than the global average over the past 50 years, with the Antarctic Peninsula ranking among the three fastest-warming
regions on Earth. Antarctic ecosystems have been affected by the
warming that has taken place. Perhaps the most notable impact has been a dramatic expansion of the two species of flowering plant that occur on the continent \u2014 Antarctic pearlwort and Antarctic hair gras
Development and initial validation of the bronchiectasis exacerbation and symptom tool (BEST)
BACKGROUND:
Recurrent bronchiectasis exacerbations are related to deterioration of lung function, progression of the disease, impairment of quality of life, and to an increased mortality. Improved detection of exacerbations has been accomplished in chronic obstructive pulmonary disease through the use of patient completed diaries. These tools may enhance exacerbation reporting and identification. The aim of this study was to develop a novel symptom diary for bronchiectasis symptom burden and detection of exacerbations, named the BEST diary.
METHODS:
Prospective observational study of patients with bronchiectasis conducted at Ninewells Hospital, Dundee. We included patients with confirmed bronchiectasis by computed tomography, who were symptomatic and had at least 1 documented exacerbation of bronchiectasis in the previous 12\u2009months to participate. Symptoms were recorded daily in a diary incorporating cough, sputum volume, sputum colour, dyspnoea, fatigue and systemic disturbance scored from 0 to 26.
RESULTS:
Twenty-one patients were included in the study. We identified 29 reported (treated exacerbations) and 23 unreported (untreated) exacerbations over 6-month follow-up. The BEST diary score showed a good correlation with the established and validated questionnaires and measures of health status (COPD Assessment Test, r =\u20090.61, p =\u20090.0037, Leicester Cough Questionnaire, r =\u2009-\u20090.52,p =\u20090.0015, St Georges Respiratory Questionnaire, r =\u20090.61,p <\u20090.0001 and 6\u2009min walk test, r =\u2009-\u20090.46,p =\u20090.037). The mean BEST score at baseline was 7.1 points (SD 2.2). The peak symptom score during exacerbation was a mean of 16.4 (3.1), and the change from baseline to exacerbation was a mean of 9.1 points (SD 2.5). Mean duration of exacerbations based on time for a return to baseline symptoms was 15.3\u2009days (SD 5.7). A minimum clinically important difference of 4 points is proposed.
CONCLUSIONS:
The BEST symptom diary has shown concurrent validity with current health questionnaires and is responsive at onset and recovery from exacerbation. The BEST diary may be useful to detect and characterise exacerbations in bronchiectasis clinical trials
The leading digit distribution of the worldwide Illicit Financial Flows
Benford's law states that in data sets from different phenomena leading
digits tend to be distributed logarithmically such that the numbers beginning
with smaller digits occur more often than those with larger ones. Particularly,
the law is known to hold for different types of financial data. The Illicit
Financial Flows (IFFs) exiting the developing countries are frequently
discussed as hidden resources which could have been otherwise properly utilized
for their development. We investigate here the distribution of the leading
digits in the recent data on estimates of IFFs to look for the existence of a
pattern as predicted by Benford's law and establish that the frequency of
occurrence of the leading digits in these estimates does closely follow the
law.Comment: 13 pages, 10 figures, 6 tables, additional data analyi
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