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Assessment of the performance of the TOPGNSS and ANN-MB antennas for ionospheric measurements using low-cost u-blox GNSS receivers

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Geodesy and Geodynamics 2024年第3期15卷 291-301页

作者： daniel okoh Aderonke Obafaye Oluwakemi Dare-Idowu Babatunde Rabiu Anton Kashcheyev Claudio Cesaroni John Bosco Habarulema Bruno Nava United Nations African Regional Centre for Space Science and Technology Education-English(UN-ARCSSTE-E) Obafemi Awolowo University CampusIle IfeNigeria National Institute for Geophysics and Volcanology(INGV) 00143 RomeItaly Institute for Space Science and Engineering African University of Science and TechnologyAbujaNigeria University of New Brunswick FrederictonCanada South African National Space Agency(SANSA) P.O Box 32Hermanus 7200South Africa Department of Physics and Electronics Rhodes University6140 MakhandaSouth Africa The Abdus Salam International Centre for Theoretical Physics Strada Costiera11I-34151 TriesteItaly

Low-cost GNSS receivers have recently been gaining reliability as good candidates for ionospheric studies. In line with these gains are genuine concerns about improving the performance of these receivers. In this work, we present a comprehensive investigation of the performances of two antennas(the u-blox ANN-MB and the TOPGNSS TOP-106) used on a low-cost GNSS receiver known as the u-blox ZED-F9P. The two antennas were installed on two identical and co-located u-blox receivers. Data used from both receivers cover the period from January to June 2022. Results from the study indicate that the signal strengths are dominantly greater for the receiver with the TOPGNSS antenna than for the receiver with the ANN-MB antenna, implying that the TOPGNSS antenna is better than the ANN-MB antenna in terms of providing greater signal strengths. Summarily, the TOPGNSS antenna also performed better in minimizing the occurrence of cycle slips on phase TEC measurements. There are no conspicuous differences between the variances(computed as 5-min standard deviations) of phase TEC measurements for the two antennas, except for a period around May-June when the TOPGNSS gave a better performance in terms of minimizing the variances in phase TEC. Remarkably, the ANN-MB antenna gave a better performance than the TOPGNSS antenna in terms of minimizing the variances in pseudorange TEC for some satellite observations. For precise horizontal(North and East) positioning, the receiver with the TOPGNSS antenna gave better results, while the receiver with the ANN-MB antenna gave better vertical(Up) positioning. The errors for the receivers of both antennas are typically within about 5 m(the monthly mean was usually smaller than 1 m) in the horizontal direction and within about 10 m(the monthly mean was usually smaller than 4 m) in the vertical direction.

关键词： GNSS Ionosphere Low-cost Antenna TOPGNSS U-blox

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An application of artificial intelligence for investigating the effect of COVID-19 lockdown on three-dimensional temperature variation in equatorial Africa

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Geoscience Frontiers 2022年第2期13卷 52-61页

作者： daniel okoh Loretta Onuorah Babatunde Rabiu Aderonke Obafaye Dauda Audu Najib Yusuf Oluwafisayo Owolabi Centre for Atmospheric Research National Space Research and Development AgencyAnyigbaNigeria Department of Physical and Geosciences Godfrey Okoye UniversityEnuguNigeria Institute for Space Science and Engineering African University of Science and TechnologyAbujaNigeria

We present interesting application of artificial intelligence for investigating effect of the COVID-19 lockdown on 3-dimensional temperature variation across Nigeria(2°-15°E,4°-14°N),in equatorial Africa.Artificial neural networks were trained to learn time-series temperature variation patterns using radio occultation measurements of atmospheric temperature from the Constellation Observing System for Meteorology,Ionosphere,and Climate(COSMIC).Data used for training,validation and testing of the neural networks covered period prior to the lockdown.There was also an investigation into the viability of solar activity indicator(represented by the sunspot number)as an input for the process.The results indicated that including the sunspot number as an input for the training did not improve the network prediction accuracy.The trained network was then used to predict values for the lockdown period.Since the network was trained using pre-lockdown dataset,predictions from the network are regarded as expected temperatures,should there have been no lockdown.By comparing with the actual COSMIC measurements during the lockdown period,effects of the lockdown on atmospheric temperatures were deduced.In overall,the mean altitudinal temperatures rose by about 1.1℃ above expected values during the lockdown.An altitudinal breakdown,at 1 km resolution,reveals that the values were typically below0.5℃ at most of the altitudes,but exceeded 1℃ at 28 and 29 km altitudes.The temperatures were also observed to drop below expected values at altitudes of 0-2 km,and 17-20 km.

关键词： Temperature Neural network Equatorial Africa COVID-19 lockdown Time-series Sunspot number

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The comparison of H_2CO(1_(10)–1_(11)),C^(18)O(1–0) and the continuum towards molecular clouds

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Research in Astronomy and Astrophysics 2014年第8期14卷 959-970页

作者： Xin-Di Tang Jarken Esimbek Jian-Jun Zhou Gang Wu daniel okoh Xinjiang Astronomical Observatory Chinese Academy of Sciences University of Chinese Academy of Sciences Key Laboratory of Radio Astronomy Chinese Academy of Sciences Physics & Astronomy Department University of Nigeria

We present large scale observations of C^18O （1-0） towards four massive star forming regions： MON R2, S156, DR17/L906 and M17/M18. The transitions of H2CO （110-111）, C^18O （1-0） and the 6cm continuum are compared in these four regions. Our analysis of the observations and the results of the Non-LTE model shows that the brightness temperature of the formaldehyde absorption line is strongest in a background continuum temperature range of about 3 - 8 K. The excitation of the H2CO absorption line is affected by strong background continuum emission. From a comparison of H2CO and C^18O maps, we found that the extent of H2CO absorption is broader than that of C^18O emission in the four regions. Except for the DR17 region, the maximum in H2CO absorption is located at the same position as the C^18O peak. A good correlation between intensities and widths of H2CO absorption and C^18O emission lines indicates that the H2CO absorption line can trace the dense, warm regions of a molecular cloud. We find that N（H2CO） is well correlated with N（ C^18O） in the four regions and that the average ratio of column densities is （N（H2CO）/N（ClSO））～0.03.

关键词： ISM clouds -- molecules -- stars formation

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A regional GNSS-VTEC model over Nigeria using neural networks： A novel approach

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Geodesy and Geodynamics 2016年第1期7卷 19-31页

作者： daniel okoh Oluwafisavo Owolabi Christovher Ekechukwu Olanike Folarin Gila Arhiwo Joseph Agbo Segun Bolaji Babatunde Rabiu NASRDA Center for Atmospheric Research Kogi State University Anyigba Campus Nigeria Ionospheric & Space Physics Laboratory Department of Physics University of Lagos Nigeria Department of Physics University of Calabar Nigeria Department of Physics Federal University of Agriculture Makurdi Nigeria Department of Surveying & Geo-informatics Nnamdi Azikiwe University Awka Nigeria

A neural network model of the Global Navigation Satellite System - vertical total electron content （GNSS-VTEC） over Nigeria is developed. A new approach that has been utilized in this work is the consideration of the International Reference Ionosphere＇s （IRI＇s） critical plasma frequency （foF2） parameter as an additional neuron for the network＇s input layer. The work also explores the effects of using various other input layer neurons like distur- bance storm time （DST） and sunspot number. All available GNSS data from the Nigerian Permanent GNSS Network （NIGNET） were used, and these cover the period from 2011 to 2015, for 14 stations. Asides increasing the learning accuracy of the networks, the inclusion of the IRI＇s foF2 parameter as an input neuron is ideal for making the networks to learn long-term solar cycle variations. This is important especially for regions, like in this work, where the GNSS data is available for less than the period of a solar cycle. The neural network model developed in this work has been tested for time-varying and spatial per- formances. The latest 10% of the GNSS observations from each of the stations were used to test the forecasting ability of the networks, while data from 2 of the stations were entirely used for spatial performance testing. The results show that root-mean-squared-errors were generally less than 8.5 TEC units for all modes of testing performed using the optimal network. When compared to other models, the model developed in this work was observed to reduce the prediction errors to about half those of the NeQuick and the IRI model.

关键词： Global Navigation Satellite System（GNSS） ionosphereTotal electron content （TEC）Nigerian permanent GNSS network（NIGNET）Neural networkInternational reference ionosphere（IRI）

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Panel positioning error and support mechanism for a 30-m THz radio telescope

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Research in Astronomy and Astrophysics 2011年第6期11卷 725-736页

作者： De-Hua Yang daniel okoh Guo-Hua Zhou Ai-Hua Li Guo-Ping Jing-Quan Cheng National Astronomical Observatories /Nanjing Institute of Astronomical Optics ＆ Technology Chinese Academy of SciencesNanjing 210042China Key Laboratory of Astronomical Optics ＆ Technology Nanjing Institute of Astronomical Optics ＆ TechnologyChinese Academy of SciencesNanjing 210042China Centre for Basic Space Science National Space Research and Development AgencyUniversity of NigeriaNsukka 410002Nigeria National Radio Astronomy Observatory CharlottesvilleVA 22903USA

A 30-m TeraHertz（THz） radio telescope is proposed to operate at 200 μm with an active primary surface.This paper presents sensitivity analysis of active surface panel positioning errors with optical performance in terms of the Strehl ratio.Based on Ruze＇s surface error theory and using a Monte Carlo simulation,the effects of six rigid panel positioning errors,such as piston,tip,tilt,radial,azimuthal and twist displacements,were directly derived.The optical performance of the telescope was then evaluated using the standard Strehl ratio.We graphically illustrated the various panel error effects by presenting simulations of complete ensembles of full reflector surface errors for the six different rigid panel positioning errors.Study of the panel error sensitivity analysis revealed that the piston error and tilt/tip errors are dominant while the other rigid errors are much less important.Furthermore,as indicated by the results,we conceived of an alternative Master-Slave Concept-based（MSC-based） active surface by implementating a special Series-Parallel Concept-based（SPC-based） hexapod as the active panel support mechanism.A new 30-m active reflector based on the two concepts was demonstrated to achieve correction for all the six rigid panel positioning errors in an economically feasible way.

关键词： telescopes-methods：data analysis-methods：statistical-techniques：miscellaneous

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Impacts of Recent Infection Testing Integration into HIV Surveillance in Ekiti State, South West Nigeria: A Retrospective Cross Sectional Study

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World Journal of AIDS 2022年第4期12卷 183-193页

作者： daniel Chinenyeike Offie Leo Akpan Felix okoh Owolagba Femi Ofuche Eke Michael Tomori Abimbola O. Ariyo Christopher Omisakin APIN Public Health Initiatives Ado Ekiti Nigeria Federal Teaching Hospital Ido Ekiti Ido Ekiti Nigeria

Background: Timely detection of recent HIV infections is critical in achieving the HIV epidemic. The aim of this study was to evaluate the effects of integrating the Recent Infection Testing Algorithm in HIV surveillance in Ekiti State, South West Nigeria. Method: Data from the Nigeria Medical Records System (NMRS)/National Data Repository (NDR) and Index Testing (IT) Services data capturing tools were abstracted for a retrospective cross-sectional study of 719 newly diagnosed HIV-positive cases who were screened for HIV incident infection using Asante rapid recency test kits between August 2020 and June 2022 at 5 selected recency testing health facilities. The venous blood (10 ml) of all the rapid Asante tested recent patients were collected into an EDTA tube and processed for viral load testing. The plasma level of HIV-1 RNA was quantified using the CAP/CTM and cobas 4800 platform at Obafemi Awolowo University Teaching Hospital PCR Laboratory Ife. Chi-square was used to characterize the recency status of the patients. A measure of the association was done using Chi-square, while the p-value of 0.05 was considered statistically significant. Results: The median age of the participants was 39 years. The result from the study showed that of the total number of 719 new cases of diagnosed HIV-positive, 626 of them were screened for rapid Test for Recency infection (RTRI) (87%). Overall, we found that 1.8% (11/626) of clients were classified as recent. The investigation also showed that from the index cases of the 11 confirmed recent infections, a total number of 125 additional positive cases were found. Conclusion: This result indicated a rise in the number of cases discovered in the State. Therefore, incorporating recency testing within regular HIV testing programs becomes essential in order to prioritize clients for index testing and provide useful information on transmission clusters.

关键词： Impacts Recent Testing HIV Surveillance

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HIV Encephalopathy (HIVE) in Children at the University of Port Harcourt Teaching Hospital (UPTH), Port Harcourt, Nigeria

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International Journal of Clinical Medicine 2018年第6期9卷 495-504页

作者： Nsirimobu Ichendu Paul Boma Alali Ngozi okoh Edward Achinike daniel Alikor Department of Paediatrics and Child Health University of Port Harcourt Port Harcourt Nigeria

Background: HIV encephalopathy (HIVE) is associated with cognitive impairment in children with HIV infection, early diagnosis and initiation of HAART may reduce the morbidity associated with HIVE. Objective: To determine the prevalence of HIVE and associated comorbiditiesin children at the UPTH. Methodology: This was a retrospective study carried out from January to June 2017. The case notes of all HIV positive children presenting to the Paediatric Department of the University of Port Harcourt Teaching Hospital (UPTH) were studied. Children who met the diagnostic criteria for HIVE according to the Centre for Disease Control (CDC) definition were selected. The socio-demographic characteristics of the patients, mode of HIV transmission, CD4 count and associated comorbidities in these children were retrieved from the case notes. Obtained data was analyzed using Epi Info version 7.2. Comparisms of subgroups was carried out using the chi square test while statistical significance at 95% confidence interval was p value Results: A total of thirty five out of the 196 HIV positive children presenting to the hospital had HIV encephalopathy (HIVE) giving a prevalence rate of 17.9%. Of these 35 children, 18 were males and 17 females, giving a male to female ratio of 1:1. The mean age of the children was 5.7 ± 3.1 years. The mean age for the males was 6.4 ± 3.2 years and 5.0 ± 2.8 years for the females. There was no statistically significant difference observed between the sexes (t = 1.35, p = 0.187). Thirty (85.7%) of the patients with HIVE were on HAART at diagnosis. The mean age at diagnosis of HIV was 3.2 ± 3.1 years and the mean age at diagnosis of HIV encephalopathy was 3.4 ± 3.2 years. The documented route of transmission for all the subjects was mother-to-child-transmission (MTCT). Seventy five percent of the children were breastfed from birth and at 6 months all the mothers had discontinued breastfeeding. The mean CD4 count was 1053 ± 630 cells/ml. Tuberculosis was the most prevalent co-morbidity occurring among the

关键词： HIV Encephalopathy Children UPTH

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