An Optimization Method of Ambiguity Function Based on Multi-Antenna Constrained and Application in Vehicle Attitude Determination

The global navigation satellite system (GNSS)-based multi-antenna attitude determination method has the advantages of a simple algorithm and no error accumulation with time in long endurance operation. However, it is sometimes difficult to simultaneous obtain the fixed solutions of all antennas in vehicle attitude determination. If float or incorrect fixed solutions are used, precision and reliability of attitude cannot be guaranteed. Given this fact, a baseline-constrained ambiguity function method (BCAFM) based on a self-built four GNSS antennas hardware platform is proposed. The coordinates obtained by BCAFM can replace the unreliable real-time kinematic (RTK) float or incorrect fixed solutions, so as to assist the direct method for attitude determination. In the proposed BCAFM, the baseline constraint is applied to improve search efficiency (searching time), and the ambiguity function value (AFV) formula is optimized to enhance the discrimination of true peak. The correctness of the proposed method is verified by vehicle attitude determination results and baseline length difference. Experimental results demonstrate that the function values of error peaks are reduced, and the only true peak can be identified accurately. The valid epoch proportion increases by 14.95% after true peak coordinates are used to replace the GNSS-RTK float or incorrect fixed solutions. The precision of the three attitude angles is 0.54°, 1.46°, and 1.15°, respectively. Meanwhile, the RMS of baseline length difference is 3.8mm.

Modeling COVID-19 dynamics in the sixteen West African countries

The COVID-19 pandemic is currently causing several damages to the world, especially in the public health sector. Due to identifiability problems in parameters' estimation of complex compartmental models, this study considered a simple deterministic susceptible-infectious-recovered (SIR)-type model to characterize and predict the future course of the pandemic in the West African countries. We estimated some specific characteristics of the disease's dynamics such as its initial conditions, reproduction numbers, true peak and peak of the reported cases, with their corresponding times, final epidemic size and time-varying attack ratio. Our findings revealed a relatively low proportion of susceptible individuals in the region and in the different countries (1:2% across West Africa). The detection rate of the disease was also relatively low (0:9% for West Africa as a whole) and < 2% for most countries, except for Gambia (12.5 %), Cape-Verde (9:5%), Mauritania (5:9%) and Ghana (4:4%). The reproduction number varied between 1.15 (Burkina-Faso) and 4.45 (Niger), and the peak time of the pandemic was between June and July for most countries. Generally, the peak time of the reported cases came a week (7-8 days) after the true peak time. The model predicted 222; 100 actual active cases in the region at the peak time, while the final epidemic size accounted for 0:6% of theWest African population (2; 526; 700 individuals). The results obtained showed that COVID-19 has not severely affected West Africa as noticed in other regions of the world. However, current control measures and standard operating procedures should be maintained over time to accelerate a decline in the observed trends of the pandemic.

COVID-19: The unreasonable effectiveness of simple models

When the novel coronavirus disease SARS-CoV2 (COVID-19) was officially declared a pandemic by the WHO in March 2020, the scientific community had already braced up in the effort of making sense of the fast-growing wealth of data gathered by national authorities all over the world. However, despite the diversity of novel theoretical approaches and the comprehensiveness of many widely established models, the official figures that recount the course of the outbreak still sketch a largely elusive and intimidating picture. Here we show unambiguously that the dynamics of the COVID-19 outbreak belongs to the simple universality class of the SIR model and extensions thereof. Our analysis naturally leads us to establish that there exists a fundamental limitation to any theoretical approach, namely the unpredictable non-stationarity of the testing frames behind the reported figures. However, we show how such bias can be quantified self-consistently and employed to mine useful and accurate information from the data. In particular, we describe how the time evolution of the reporting rates controls the occurrence of the apparent epidemic peak, which typically follows the true one in countries that were not vigorous enough in their testing at the onset of the outbreak. The importance of testing early and resolutely appears as a natural corollary of our analysis, as countries that tested massively at the start clearly had their true peak earlier and less deaths overall.

Caterpillars Count! A citizen science project for monitoring foliage arthropod abundance and phenology

ABSTRACTCaterpillars Count! is a citizen science project that allows participants to collect data on the seasonal timing, or phenology, of foliage arthropods that are important food resources for forest birds. This project has the potential to address questions about the impacts of climate change on birds over biogeographic scales. Here, we provide a description of the project’s two survey protocols, evaluate the impact of survey methodology on results, compare findings made by citizen scientist participants versus trained scientists, and identify the minimum levels of sampling frequency and intensity in order to accurately capture phenological dynamics. We find that beat sheet surveys and visual surveys yield similar relative and absolute density estimates of different arthropod groups, with beat sheet surveys recording a higher frequency of beetles and visual surveys recording a higher frequency of flies. Citizen scientists generated density estimates within 6% of estimates obtained by trained scientists regardless of survey method. However, patterns of phenology were more consistent between citizen scientists and trained scientists when using beat sheet surveys than visual surveys. By subsampling our survey data, we found that conducting 30 foliage surveys on a weekly basis led to 95% of peak caterpillar date estimates to fall within one week of the "true" peak. We demonstrate the utility of Caterpillars Count! for generating a valuable dataset for ecological research, and call for future studies to evaluate how training and resource materials impact data quality and participant learning gains.

Uterine perforation by intrauterine devices: a 16-year review

IntroductionOne of the major concerns with the insertion of intrauterine devices is uterine perforation. Though uncommon, it can be debilitating and result in failure of the device. In this article we review uterine perforation with intrauterine contraception (IUC) in a community clinic in the UK over a 16-year period.MethodsWe prospectively collected data on uterine perforations for the years 2000–2015, reviewed associated factors and calculated the annual rate of perforation, estimating if this lay within the expected range of normal variation using statistical process control (SPC) analysis. We analysed the rates of perforation in relation to the time from delivery and to breastfeeding.ResultsWe identified 30 uterine perforations in 22 795 IUC insertions over the 16 years of observation, with an annual rate ranging from 0 to 4.3 per 1000 insertions, and a mean annual rate of 1.3 per 1000 insertions (95% CI 0.9 to 1.9), which remain within the SPC limits. Twenty-eight of the perforations were in parous women, 87% of whom were within 18 weeks of delivery, peaking at 13 weeks postpartum. Twenty of these were in breastfeeding women. In 3/28 cases for which we have outcome data the device was adherent to or had perforated either the bladder or bowel.ConclusionOur perforation rate is consistent with other studies. Most of our perforations were within 18 weeks of childbirth, earlier than in a recent major study. We cannot tell from our data if there is a true peak in perforations 3 months postpartum as that may be a time when a high proportion of insertions are done.

Adherence to recommended UK sampling protocols for detecting mast cell mediator release in perioperative anaphylaxis

BackgroundSheffield National Adverse Reactions Consultancy Service (NARCOS) investigates and triages suspected perioperative anaesthetic reactions to allergy clinics, using serial tryptase samples, urinary methylhistamine and clinical information on a pro forma request.ObjectiveTo determine if current UK guidelines on serial tryptase samples are achieved and describe the patterns of tryptase release.MethodA retrospective review of 3455 NARCOS cases. Tryptase and clinical details were analysed. 1746 had sufficient clinical information to grade the reactions according to the Ring and Messmer scale.Results98% provided two or more acute samples, but only 60% supplied clinical information. 308 patients never dropped within the reference range over three samples.ConclusionsGood compliance with UK guidelines for tryptase measurements is achievable in this long-term cohort, but obtaining clinical details at referral remains a challenge. Sample sequence labelling and apparent timing may be misleading. Baseline tryptase may frequently need to be rechecked in allergy clinics to estimate true peak-to-trough changes.

Accuracy of Visual Estimates of Joint Angle and Angular Velocity Using Criterion Movements

A descriptive study to document undergraduate physical education majors' (22.8 ± 2.4 yr. old) estimates of sagittal plane elbow angle and angular velocity of elbow flexion visually was performed. 42 subjects rated videotape replays of 30 movements organized into three speeds of movement and two criterion elbow angles. Video images of the movements were analyzed with Peak Motus™ to measure actual values of elbow angles and peak angular velocity. Of the subjects 85.7% had speed ratings significantly correlated with true peak elbow angular velocity in all three angular velocity conditions. Few (16.7%) subjects' ratings of elbow angle correlated significantly with actual angles. Analysis of the subjects with good ratings showed the accuracy of visual ratings was significantly related to speed, with decreasing accuracy for slower speeds of movement. The use of criterion movements did not improve the small percentage of novice observers who could accurately estimate body angles during movement.

Consistency Checks for X-Ray Microanalysis at Low KV

This work proposes a new consistency check total based on measurement of bremsstrahlung intensity which can be used to validate analyses even when concentrations have been normalised to 100%.If elemental content of a material is unknown, spectral peaks have to be identified, either interactively, or by automatic procedures. When peak overlap is severe (e.g. Si K/ Ta M / W M, Al K/Br L), it is easy for an element to be misidentified or missed altogether and at low beam kV, some elements will not even produce a characteristic line suitable for analysis. When element identification or quantification requires deconvolution of closely spaced lines, minor miscalibration or inaccurate peak modelling produces inaccurate peak area estimates, Ai, instead of true peak areas, Ai*, and consequently inaccurate concentration estimates, Ci* . A common consistency check is to confirm that the analysis total is close to unity: